🏷

Classifications

Harrison's Part

🔗

Mappings

MONDO

MONDO:0015643 photosensitive epilepsy

MONDO:0015643 is defined as "An epilepsy characterized by seizures triggered by visual stimuli that form patterns in space or time, such as flashing lights," is cross-referenced to OMIM phenotypic series PS132100, and carries a formal RO:0009501 (has disposition to bear a role) relationship to ECTO:0000007 (exposure to visible light radiation) in its own logical definition, which is the same relationship this entry's environmental section encodes as influences_mechanisms.

👪

Inheritance

1

Genetically complex, polygenic trait with identified contributing loci

Photosensitivity itself is a heritable EEG trait most consistent with complex, polygenic inheritance rather than a single Mendelian pattern. CHD2 is the best-established single-gene risk-factor contributor identified to date (see genetic section), but unique CHD2 variants explain only a minority of photosensitive-epilepsy cases, and the condition as a whole is genetically heterogeneous. Individual named subtypes carry their own, separately curated inheritance patterns in their own entries.

Show evidence (1 reference)

PMID:25783594 SUPPORT Human Clinical

"We identified 11 unique variants in the 580 individuals with photosensitive epilepsies and 128 unique variants in the 34 427 controls: unique CHD2 variation is over-represented in cases overall (P = 2.17 × 10(-5))"

Quantifies CHD2 as a statistically significant but partial contributor (11 of 580 cases carried a unique variant), supporting a complex rather than single-gene-necessary inheritance model for photosensitivity as a whole.

◆

Subtypes

6

Pure (Isolated) Photosensitive Epilepsy

Photically triggered seizures with no other spontaneous epilepsy syndrome: intermittent photic stimulation, and often a specific flicker-frequency range, is the only identified seizure trigger, and seizures do not occur in its absence. This is the reflex-epilepsy end of the spectrum. No dedicated MONDO identifier is bound for this subtype beyond the root MONDO:0015643 concept itself: MONDO's own children of photosensitive epilepsy (photoparoxysmal response 1-3, part of OMIM phenotypic series PS132100) are genetic-linkage loci mapped from family studies of the photoparoxysmal EEG trait, not a distinct clinical entity matching this description, so binding one of them here would overstate what they represent.

Show evidence (1 reference)

PMID:35807051 SUPPORT Other

"Epilepsy with seizures provoked by intermittent light stimulation is a distinct group of epilepsies"

A recent scoping review treats photically provoked epilepsy as its own distinct group, supporting a pure reflex form separate from photosensitivity riding along with another syndrome. Evidence source is OTHER because this is a review article.

Photosensitive Occipital Lobe Epilepsy MONDO:0100021

A focal reflex epilepsy in which flickering light or structured pattern, classically television or video games, triggers a seizure that begins with elementary visual hallucinations and is accompanied by an occipitally confined (rather than generalized) photoparoxysmal response. Already fully curated as its own dismech entry; see kb/disorders/Photosensitive_Occipital_Lobe_Epilepsy.yaml for the detailed pathophysiology, phenotypes, and evidence. This subtype block exists to place that entry in the photosensitive-epilepsy family and is deliberately not a duplicate of its content.

Show evidence (1 reference)

PMID:35503717 SUPPORT Other

"Epilepsy syndromes beginning in childhood have been divided into three categories: (1) self-limited focal epilepsies, comprising four syndromes: self-limited epilepsy with centrotemporal spikes, self-limited epilepsy with autonomic seizures, childhood occipital visual epilepsy, and..."

Establishes photosensitive occipital lobe epilepsy as a current ILAE-recognized syndrome, the same citation already used in its own entry to ground its nosological status. Evidence source is OTHER because this is a nosology position paper, not a primary study.

Photosensitivity in Juvenile Myoclonic Epilepsy MONDO:0009696

Juvenile myoclonic epilepsy (JME) is fully curated as its own dismech entry (kb/disorders/Juvenile_Myoclonic_Epilepsy.yaml); this subtype block scopes only the photosensitivity trait within it. Photosensitive seizures and an abnormal photoparoxysmal response are common in JME, but unlike pure photosensitive epilepsy, most patients also have spontaneous myoclonic and generalized tonic-clonic seizures on awakening that are not photically triggered, so JME as a whole conforms to the module's unprovoked-seizure terminal node in its own entry in a way that this photosensitivity-specific subtype block does not restate.

Show evidence (1 reference)

PMID:25783594 SUPPORT Human Clinical

"We sought CHD2 variants in 238 exomes from familial genetic generalized epilepsies, and in other public exome data sets."

Documents that the photosensitivity genetics work covered familial genetic generalized epilepsies, the category JME belongs to, as part of establishing where CHD2 variation contributes across the photosensitive-epilepsy spectrum rather than only in the archetypal syndrome.

Jeavons Syndrome (Eyelid Myoclonia with Absences) MONDO:0015346

CHD2 hgnc:1917

Jeavons syndrome is fully curated as its own dismech entry (kb/disorders/Jeavons_Syndrome.yaml). It is placed here as a subtype because the literature identifies it as the single syndrome in which photosensitivity is not merely a common accompanying trait but is part of the syndrome's own defining triad, alongside eyelid myoclonia and eye-closure-induced EEG paroxysms, and because it is the syndrome in which the CHD2 gene-photosensitivity association was first and most strongly established.

Show evidence (2 references)

PMID:25783594 SUPPORT Human Clinical

"Among epilepsy syndromes, there was over-representation of unique CHD2 variants (3/36 cases) in the archetypal photosensitive epilepsy syndrome, eyelid myoclonia with absences (P = 3.50 × 10(-4))"

States directly that eyelid myoclonia with absences (Jeavons syndrome) is the archetypal photosensitive epilepsy syndrome and gives the statistical basis for the CHD2 association being strongest there.

PMID:25783594 SUPPORT Human Clinical

"CHD2 mutation is the first identified cause of the archetypal generalized photosensitive epilepsy syndrome, eyelid myoclonia with absences."

The authors' own summary statement naming CHD2 as the first identified genetic cause specifically of Jeavons syndrome.

Photosensitivity in Dravet Syndrome MONDO:0100135

Dravet syndrome is fully curated as its own dismech entry (kb/disorders/Dravet_syndrome.yaml); this subtype block scopes only the photosensitivity trait within it. Photosensitivity in Dravet syndrome (historically described under the older name severe myoclonic epilepsy in infancy, SMEI) has been shown to follow a different physiological rule from most other photosensitive epilepsies: the photoparoxysmal response tends to depend on the total quantity of light delivered rather than on its wavelength, unlike the wavelength-dependent pattern more typical of localization-related and symptomatic generalized epilepsies.

Show evidence (1 reference)

PMID:10496248 SUPPORT Human Clinical

"Four of the six photosensitive SMEI patients had quantity-of-light-dependent PPRs."

Directly reports the quantity-of-light-dependent mechanism found in most photosensitive severe myoclonic epilepsy in infancy (Dravet syndrome) patients in this cohort, distinguishing it from the wavelength-dependent mechanism seen in other syndromes in the same study.

Photosensitivity in the Progressive Myoclonic Epilepsies MONDO:0020074

The progressive myoclonic epilepsies (individually curated as their own dismech entries, e.g. kb/disorders/Progressive_Myoclonic_Epilepsy_Type_7.yaml and kb/disorders/Progressive_Myoclonic_Epilepsy_Type_8.yaml) frequently show a photoparoxysmal EEG response, most classically in Unverricht-Lundborg disease. Unlike the genetic generalized epilepsies above, photosensitivity here occurs against a background of a degenerative, worsening disease course, and both the spike-wave discharges and the photoparoxysmal response have been reported to diminish again as the disease reaches adulthood.

Show evidence (2 references)

PMID:18358403 SUPPORT Human Clinical

"Slowing of background activity, generalized spike-wave discharges, and photoparoxysmal responses were evident in all patients' electroencephalograms."

Documents the photoparoxysmal response as a universal EEG finding in this confirmed Unverricht-Lundborg disease cohort, establishing photosensitivity as a feature of the progressive myoclonic epilepsies.

PMID:18358403 SUPPORT Human Clinical

"Spike-wave discharges and photoparoxysmal responses tended to disappear in adulthood."

Reports the age-dependent attenuation of the photoparoxysmal response in this progressive disease, a course distinct from the other subtypes in this entry.

?

Discussions and Knowledge Gaps

2

Should photosensitive epilepsy conform to the epilepsy_excitation_inhibition_imbalance module's terminal node, Recurrent Unprovoked Seizures, given that its defining feature is a reproducibly provoked seizure, and how should that boundary be recorded when a subtype (JME, Dravet, the PMEs) genuinely has both provoked and unprovoked seizures?

OPEN QUESTION OPEN pse_provoked_seizure_module_boundary

Attached to

pathophysiology#Recurrent Visually Provoked Seizures

This entry declares conformance to epilepsy_excitation_inhibition_imbalance at the Neuronal Hyperexcitability and Hypersynchrony node and stops there, for the same reason already recorded in kb/disorders/Photosensitive_Occipital_Lobe_Epilepsy.yaml: the module's terminal node is Recurrent Unprovoked Seizures, and reflex seizures are elicited by definition, so declaring conformance there would assert the negation of the defining property of the reflex component this entry models. The complication specific to this root entry, and not shared by POLE, is that most of its named subtypes (JME, Jeavons syndrome, Dravet syndrome, the PMEs) are not purely reflex: they also have genuinely spontaneous, unprovoked seizures, and those subtypes' own separately curated entries may correctly conform to the terminal node for that reason. This entry's photosensitivity-scoped pathophysiology chain should not be read as contradicting that; it describes only the reflex component common to the whole family, deliberately leaving the unprovoked-seizure question to each subtype's own full entry.

Proposed experiments

Audit of reflex-epilepsy and mixed-trigger entries against the module terminal node

pse_module_node_audit

Extending the audit already proposed in the Photosensitive_Occipital_Lobe_Epilepsy entry, specifically compare how the terminal node is (or is not) declared across purely reflex entries versus mixed entries like this one that have both a reflex-scoped root and unprovoked-seizure-capable subtypes.

Decision criterion

If curators consistently split conformance the way this entry does (reflex root stops short, individual mixed subtype entries conform separately), that confirms the current approach as the intended pattern rather than an ad hoc choice, and the module documentation should say so explicitly.

Show evidence (2 references)

PMID:34221545 SUPPORT Other

"Reflex seizures (RS) are epileptic events that are objectively and consistently elicited in response to a specific afferent stimulus or by an activity of the patient."

Establishes reflex seizures as provoked by definition, creating the conflict with the module's unprovoked terminal node that this discussion is about. Evidence source is OTHER because this is a narrative review, not a primary cohort or case study.

PMID:25783594 SUPPORT Human Clinical

"We studied 580 individuals with epilepsy and either photosensitive seizures or abnormal photoparoxysmal response on electroencephalography, or both, and 55 individuals with photoparoxysmal response but no seizures."

Shows that the cohort used to establish the genetics of this trait was itself drawn from mixed generalized-epilepsy syndromes, not only pure reflex cases, which is the empirical basis for the complication this discussion raises about subtype entries having both provoked and unprovoked seizures.

By what mechanism does CHD2, a chromatin remodeler with no known direct role in ion transport or synaptic transmission, produce an acutely provokable cortical hyperexcitability, and does that mechanism converge on the same excitation-inhibition imbalance this entry's pathophysiology chain describes for the channelopathy-driven photosensitive syndromes?

KNOWLEDGE GAP OPEN chd2_chromatin_to_hyperexcitability_gap

Attached to

genetic#CHD2 pathophysiology#Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation

Every other well-established photosensitive or generalized epilepsy gene referenced across this entry's subtypes and elsewhere in the knowledge base encodes an ion channel or a direct synaptic protein, fitting naturally into the excitation-inhibition imbalance framework this entry conforms to. CHD2 is different by the original authors' own framing: it is a chromatin remodeler, and how altering chromatin state during neurodevelopment produces a cortex that overreacts to a stimulus delivered in real time, rather than a fixed developmental malformation, is not established. The zebrafish knockdown result shows the effect is causal, not merely correlational, but does not by itself identify the intermediate steps between chromatin remodeling and acute photic-response hyperexcitability, so this is recorded as a knowledge gap rather than folded into the pathophysiology chain as an established mechanism.

Proposed experiments

Transcriptomic profiling of visual-cortex neurons in a Chd2-deficient model

chd2_downstream_expression_profiling

Single-cell or bulk transcriptomic and chromatin-accessibility profiling of visual-cortex neurons in a Chd2-deficient animal model, testing whether loss of Chd2 dysregulates expression of ion-channel or synaptic genes already implicated in the excitation-inhibition imbalance module, which would identify a convergent downstream pathway.

Decision criterion

Dysregulation of known excitability genes would support convergence on the module's existing framework; a distinct or absent transcriptional signature in relevant excitability genes would indicate CHD2 acts through a genuinely separate mechanism not yet captured by the module.

Show evidence (2 references)

PMID:25783594 SUPPORT Human Clinical

"CHD2 does not encode an ion channel, opening new avenues for research into human cortical excitability."

The authors' own statement of the mechanistic gap this discussion records.

PMID:25783594 SUPPORT Model Organism

"Chd2 knockdown markedly enhanced mild innate zebrafish larval photosensitivity."

Establishes that the CHD2-photosensitivity link is causal in an animal model, which is why this is framed as an open question about intermediate mechanism rather than about whether an effect exists at all.

⚙

Pathophysiology

6

Reduced Alpha-Rhythm Network Inhibition

Simultaneous EEG-fMRI shows that photosensitive patients have reduced inhibition of the resting-state networks that generate the posterior alpha rhythm, the brain's normal idling rhythm, compared with both non-photosensitive epilepsy patients and healthy controls. This is a baseline network-level abnormality, present outside of stimulation, and is the excitation-inhibition-imbalance amplifier step that this entry's pathophysiology chain was previously missing: the acute hyperexcitable response to flickering light described in the next node is superimposed on a cortex whose inhibitory network tone is already reduced.

Downstream

Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation

Show evidence (3 references)

PMID:28334965 SUPPORT Human Clinical

"This difference consists of a decreased alpha-related inhibition of the visual cortex and sensory-motor networks at rest."

The authors' own statement of the finding this node models: reduced alpha-related inhibition of the visual and sensory-motor cortex, measured at rest independent of any stimulus, the E/I-imbalance amplifier step this entry's pathophysiology chain was missing. Retrieved directly from the article's abstract (the earlier DOI-keyed cache entry for the same article lacked full text; this PMID-keyed fetch resolved it).

PMID:28334965 SUPPORT Human Clinical

"Genetic generalized epilepsy with photosensitivity demonstrated significantly greater mean alpha-power with respect to controls and other epilepsy groups."

The specific EEG-fMRI measurement distinguishing photosensitive from non-photosensitive epilepsy groups, establishing that this inhibitory-network abnormality is specific to photosensitivity rather than to epilepsy in general.

DOI:10.1101/2024.12.21.24319242 Preprint · not peer-reviewed SUPPORT Human Clinical

"PSE patients showed apparent differences in functional connectivity in the PPR band (3-4Hz) with hypoconnected centro-parietal regions and hyperconnected anterior and anterio-posterior areas compared to HC and PWE for stimulation frequencies 10Hz-20Hz."

Independent EEG connectivity evidence that photosensitive-epilepsy networks are abnormally hypoconnected over posterior/centro-parietal regions, a network-level correlate consistent with reduced posterior inhibitory network tone. Supports is PARTIAL because this preprint frames the finding as altered functional connectivity during stimulation rather than as reduced inhibition specifically, and it remains an unpublished preprint (is_preprint: true in its cache record).

Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation

The root abnormality is a visual cortex, and adjoining parietal cortex, that responds to flickering light or a structured pattern with an excessive, hypersynchronous discharge rather than a normal evoked response. This is a heritable trait present with or without clinical seizures, and it is the abnormality that the photoparoxysmal response makes visible on EEG.

abnormally amplified cortical response to visual stimulation ⚠ ABNORMAL

primary visual cortex UBERON:0002436

Animal models

Papio papio photosensitive baboon Papio papio (baboon) recapitulates Reproduces the core trait this entry's pathophysiology chain begins with -- a heritable cortical hyperexcitability to flickering light -- in a species phylogenetically closer to humans than the rodent and avian models available for this trait.

Fepi (Fayoumi) photosensitive chicken line Gallus gallus (Fayoumi-derived Fepi chicken strain) fails to recapitulate Reproduces heritable photic (and audiogenic) seizure susceptibility linked to a defined synaptic gene, but living neural-chimera experiments in this strain -- replacing specific embryonic brain vesicles with their Fepi-donor equivalents -- localize the seizure generator to the brain stem (prosencephalon and mesencephalon), not to the visual cortex this entry's pathophysiology chain describes.

Downstream

Photoparoxysmal EEG Response

Show evidence (2 references)

PMID:25783594 SUPPORT Human Clinical

"Photosensitivity is a heritable abnormal cortical response to flickering light, manifesting as particular electroencephalographic changes, with or without seizures."

Defines photosensitivity itself as the abnormal cortical response this node models, and establishes that it is heritable and exists independently of overt seizures.

PMID:35807051 SUPPORT Other

"we focused on reflex seizures provoked by different factors whose common feature is the patient's response to intermittent photic stimulation."

States that the common feature across these reflex seizures is the patient's cortical response to intermittent photic stimulation, which is what this node and the linked environmental exposure both describe. Evidence source is OTHER because this is a review article.

Photoparoxysmal EEG Response

The electrographic signature elicited by intermittent photic stimulation: spike, polyspike, or spike-wave discharges appearing during or immediately after the stimulus train, usually with a generalized or bilateral field in the syndromes modeled by this entry (in contrast to the occipitally confined response of the separately curated photosensitive occipital lobe epilepsy subtype). The physiological rule governing elicitation differs by underlying syndrome: some patients' responses depend on stimulus wavelength, while others', notably in Dravet syndrome, depend instead on the total quantity of light delivered.

Downstream

Visual-to-Motor Cortical Hyperexcitable Spread

Show evidence (3 references)

PMID:10496248 SUPPORT Human Clinical

"The authors found two types of pathophysiologic mechanisms of PPRs (wavelength-dependent PPRs and quantity-of-light-dependent PPRs) in patients with idiopathic generalized epilepsy and hereditary dentatorubral-pallidoluysian atrophy."

Establishes the two distinct physiological mechanisms that generate the photoparoxysmal response and ties them to different underlying epilepsy syndromes, which is the basis for this node's claim that the eliciting rule is syndrome-dependent.

PMID:10496248 SUPPORT Human Clinical

"The type of pathophysiologic mechanism for eliciting PPRs by low-luminance photic stimulation was closely related to the classification of the epilepsy syndrome."

The authors' own concluding statement linking PPR-eliciting mechanism to epilepsy syndrome classification.

PMID:31526678 SUPPORT Human Clinical

"69.9% patients were evoked by frequency ranged 8 Hz-25 Hz, with accompanying seizures in 13 patients."

Quantifies the flicker-frequency range that elicits the response in a large prospective cohort and the minority in whom the electrographic response is accompanied by a clinical seizure.

Visual-to-Motor Cortical Hyperexcitable Spread

Once elicited in visual cortex, the discharge does not stay contained: transcranial magnetic stimulation studies show that the normal inhibitory connection from primary visual cortex to primary motor cortex is lost specifically in patients who currently show a photoparoxysmal response, so that motor cortex responds excessively to visual-cortex input. This overactive visuomotor connection is proposed as the mechanistic bridge between an occipital electrographic event and the myoclonic and generalized motor phenomena that follow it.

primary motor cortex UBERON:0001384

Downstream

Photically Provoked Seizure Generation

Show evidence (2 references)

PMID:26395125 SUPPORT Human Clinical

"IGE patients with a PPR have an overactive functional response of M1 to inputs traveling from V1."

The authors' direct conclusion establishing the overactive visual-to-motor cortical connection this node models.

PMID:26395125 SUPPORT Human Clinical

"This was not true in PPR-positive IGE patients, in whom this type of physiologic inhibition was significantly (p < 0.05) reduced."

The specific measurement behind the claim: the normal V1-to-M1 inhibitory effect measured by TMS was significantly reduced only in patients currently showing a photoparoxysmal response, not in photonegative patients or healthy controls.

Photically Provoked Seizure Generation

The clinical seizure: myoclonic jerks, absence, or generalized tonic-clonic activity emerging once the visuomotor spread recruits enough cortex to produce a symptom. Which seizure type predominates depends on the underlying syndrome rather than on the trigger itself, which is why the same photic stimulus produces eyelid myoclonia in Jeavons syndrome, myoclonic jerks in juvenile myoclonic epilepsy, and occipital visual seizures in photosensitive occipital lobe epilepsy.

Downstream

Recurrent Visually Provoked Seizures

Show evidence (1 reference)

PMID:31526678 SUPPORT Human Clinical

"6 of 9 patients with eyes closure sensitivity experienced epileptic seizures during IPS."

Direct observation of the electrographic-to-clinical transition, in this case in patients with eye-closure sensitivity, a subset of the photosensitivity trait.

Recurrent Visually Provoked Seizures

The clinical epilepsy at its purest: seizures reliably and repeatedly elicited by the same class of visual stimulus. This node deliberately does not conform to the module's Recurrent Unprovoked Seizures node; see the attached discussion. It describes the reflex component common to every subtype in this entry, not the full clinical picture of any one of them; the subtype blocks and their linked entries additionally describe spontaneous, unprovoked seizures where those occur.

Show evidence (1 reference)

PMID:34221545 SUPPORT Other

"Reflex seizures (RS) are epileptic events that are objectively and consistently elicited in response to a specific afferent stimulus or by an activity of the patient."

Defines the reflex seizure by its consistent elicitation, the property that makes photically provoked seizures provoked by definition and grounds the module-boundary discussion attached to this node. Evidence source is OTHER because this is a narrative review, not a primary cohort or case study.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

5

Visually Provoked Seizures VERY_FREQUENT Neurological HP:0020216

Show evidence (1 reference)

PMID:35807051 SUPPORT Other

"Photo-dependent reflex seizures make up the majority of this type of disorder among reflex seizures."

Establishes visually provoked seizures as the majority form of reflex seizures overall, supporting a very frequent band for this defining feature. Evidence source is OTHER because this is a review article.

Photoparoxysmal Response on Intermittent Photic Stimulation Neurological HP:0010852

Show evidence (1 reference)

PMID:31526678 SUPPORT Human Clinical

"Of the 73 patients with PPR to IPS, 48 were female."

Documents a cohort of 73 patients ascertained specifically by their PPR to IPS, supporting that this EEG finding is the diagnostic criterion by which patients enter this and comparable cohorts. No frequency band is set here: this sentence quantifies the cohort's sex distribution, not what fraction of photosensitive-epilepsy patients show a PPR, and no cached reference in this entry gives a quotable population-level PPR frequency to justify one.

Photosensitive Myoclonic Seizures FREQUENT Neurological HP:0001327

Show evidence (1 reference)

PMID:25783594 SUPPORT Human Clinical

"We studied 580 individuals with epilepsy and either photosensitive seizures or abnormal photoparoxysmal response on electroencephalography, or both, and 55 individuals with photoparoxysmal response but no seizures."

Establishes photosensitive seizures, predominantly myoclonic in the genetic generalized syndromes this cohort was drawn from, as a recurrent clinical finding across a large ascertained sample.

Photosensitive Tonic-Clonic Seizures FREQUENT Neurological HP:0007207

Show evidence (2 references)

PMID:35807051 SUPPORT Other

"Although generalized seizures, such as myoclonic, tonic-clonic, and absence, are the most common, PPR has also been found in patients with occipital epilepsy and temporal lobe epilepsy"

States directly that tonic-clonic seizures are, along with myoclonic and absence seizures, among the most common seizure types in patients with PPR, supporting a frequent rather than merely occasional band. Evidence source is OTHER because this is a scoping review, not a primary cohort study. Replaces an earlier citation that quoted an eye-closure-sensitivity sentence unrelated to seizure type and miscounted 6 of 9 (67%) as "only a minority."

PMID:31526678 SUPPORT Human Clinical

"69.9% patients were evoked by frequency ranged 8 Hz-25 Hz, with accompanying seizures in 13 patients."

Quantifies that a clinical seizure of any type (not specifically tonic-clonic) accompanied the electrographic response in only 13 of the 73 PPR-positive patients (about 18%), the minority figure this paper actually supports; PARTIAL because the seizure type is not broken down by semiology in this sentence.

Eyelid Myoclonia Seizures VERY_FREQUENT Neurological HP:0032678

Show evidence (1 reference)

PMID:25783594 SUPPORT Human Clinical

"Among epilepsy syndromes, there was over-representation of unique CHD2 variants (3/36 cases) in the archetypal photosensitive epilepsy syndrome, eyelid myoclonia with absences (P = 3.50 × 10(-4))"

Names eyelid myoclonia with absences as the archetypal photosensitive epilepsy syndrome, supporting a very frequent band for its defining seizure type within this subtype.

🧬

Genetic Associations

1

CHD2 (Unique (singleton) CHD2 variants are significantly over-represented in people with photosensitive epilepsies compared to population controls, and are the strongest single-gene contributor identified to date. CHD2 encodes an ATP-dependent chromodomain-helicase-DNA-binding chromatin remodeler rather than an ion channel, which is notable because nearly every other established photosensitive/generalized epilepsy gene encodes a channel or a direct synaptic protein; how chromatin remodeling during neurodevelopment produces an acutely provokable cortical hyperexcitability is not established. Severe, fully penetrant loss-of-function CHD2 variants instead cause a distinct, separately curated developmental and epileptic encephalopathy (kb/disorders/CHD2-Related_Developmental_and_Epileptic_Encephalopathy.yaml); the risk-factor association modeled here is the milder, incompletely penetrant end of the same gene's phenotypic spectrum, seen in people whose epilepsy is not a fully expressed encephalopathy.)

Gene: CHD2 hgnc:1917 relationship_type: RISK_FACTOR

Show evidence (3 references)

PMID:25783594 SUPPORT Model Organism

"Chd2 knockdown markedly enhanced mild innate zebrafish larval photosensitivity."

Zebrafish chd2 knockdown causally enhances photosensitivity in vivo, supporting a functional, not merely statistical, role for CHD2 loss in the photosensitivity trait.

PMID:25783594 SUPPORT Human Clinical

"CHD2 does not encode an ion channel, opening new avenues for research into human cortical excitability."

The authors' own framing of CHD2 as mechanistically distinct from the channelopathies that dominate epilepsy genetics, which is the basis for treating the CHD2-to-hyperexcitability link as an open mechanistic question rather than an established pathway.

PMID:25783594 SUPPORT Human Clinical

"CHD2 variation was not over-represented in photoparoxysmal response without seizures."

Sharpens the scope of the CHD2 association: it holds for photosensitive epilepsy (seizures, or an abnormal photoparoxysmal response occurring alongside a seizure disorder) but not for the photoparoxysmal response occurring alone with no seizures, the same trait-versus-epilepsy boundary this entry draws elsewhere. Graded PARTIAL because it is a negative result narrowing where the positive association applies, not new support for the RISK_FACTOR claim itself.

💊

Medical Actions

4

Antiseizure Pharmacotherapy

Action: Pharmacotherapy NCIT:C15986

Agent: valproic acid CHEBI:39867 levetiracetam CHEBI:6437

Valproate is the conventional first-line agent for photosensitive epilepsy and reliably suppresses the photoparoxysmal response; levetiracetam is a common alternative, particularly favored in girls and young women given valproate's teratogenicity and other reproductive-health concerns. A separate, purely pharmacodynamic sex difference has also been reported: in a within-patient retrospective cohort, males showed a significantly greater reduction in the standardized photosensitivity range on valproate than females, a finding distinct from (and not explained by) the prescribing pattern driven by teratogenicity risk.

Mechanism Target:

INHIBITS Visual-to-Motor Cortical Hyperexcitable Spread

Show evidence (2 references)

PMID:40580381 SUPPORT Human Clinical

"It is well established that VPA reduces or suppresses PPR, as first shown after single oral doses in seven out of nine photosensitive patients"

States directly that valproate reduces or suppresses the photoparoxysmal response, the basis for describing it as the conventional first-line agent for photosensitive epilepsy.

PMID:40580381 SUPPORT Human Clinical

"Males experienced a significantly greater reduction in SPR compared with females. The mean decrease in SPR was -7.0 ± 2.6 in males only versus -3.9 ± 3.3 in females only (p = 0.0018)."

The study's own headline pharmacodynamic finding, quantifying the sex difference in valproate response referenced in the description above: a within-patient comparison of standardized photosensitivity range change before and after valproate, showing a significantly larger reduction in males.

Cenobamate

Action: Pharmacotherapy NCIT:C15986

Agent: cenobamate CHEBI:234112

In a phase 2 proof-of-principle study, a single oral dose of cenobamate (then YKP3089) produced dose-dependent suppression of the photoparoxysmal response in photosensitive epilepsy patients, establishing acute PPR suppression for a drug whose broader mechanism combines sodium-channel inactivation with GABA-A receptor positive allosteric modulation. It is an approved antiseizure medication used more broadly for focal-onset seizures; this entry documents its acute-suppression evidence specifically in the photosensitivity model, not a long-term PSE effectiveness trial.

Mechanism Target:

INHIBITS Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation

Show evidence (3 references)

PMID:31292226 SUPPORT Human Clinical

"Cenobamate 100 mg produced partial suppression in 1 of 3 patients; 250 mg produced complete suppression in 1 of 4 and partial suppression in 4 of 4 patients; and 400 mg produced complete suppression in 1 of 4 and partial suppression in 2 of 4 patients."

The dose-by-dose suppression results directly supporting the INHIBITS relationship asserted on this treatment. Retrieved directly from the article's PMID-keyed abstract (the earlier DOI-keyed cache entry for the same article lacked full text; this PMID-keyed fetch resolved it).

PMID:31292226 SUPPORT Human Clinical

"CONCLUSIONS: This proof-of-principle study demonstrated that cenobamate is a potentially effective product for epilepsy."

The authors' own conclusion, establishing acute PPR suppression as proof-of-principle evidence for cenobamate in photosensitive epilepsy.

clinicaltrials:NCT00616148 SUPPORT Other

"The aim of this study is to evaluate the ability of a single oral dose of YKP3089 to abolish or clearly reduce the IPS-induced photo-paroxysmal EEG response in photosensitive epilepsy patients, and to measure the onset and duration of the effect."

ClinicalTrials.gov registration record for the proof-of-principle cenobamate (YKP3089) trial whose published results are cited above. Evidence source is OTHER because this is a registration summary, not study results.

Investigational GABAergic Positive Allosteric Modulation

Action: Pharmacotherapy NCIT:C15986

PF-06372865, an alpha2/3/5-subunit-selective GABA-A receptor positive allosteric modulator designed to avoid the alpha1-mediated sedative and dependence liabilities of benzodiazepines, produced a marked and statistically significant suppression of the photoparoxysmal response in a phase 2a proof-of-principle study, comparable in magnitude to lorazepam. This is investigational rather than an approved therapy, but is included because the human photosensitivity model is being used directly as a translational efficacy readout for this drug class.

Mechanism Target:

INHIBITS Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation

Show evidence (2 references)

PMID:30877186 SUPPORT Human Clinical

"Both doses of PF-06372865 produced a marked and statistically significant mean reduction in SPR compared to placebo, which was similar in degree to lorazepam."

The primary efficacy result supporting the INHIBITS relationship asserted on this treatment.

PMID:30877186 SUPPORT Human Clinical

"There was complete suppression of SPR in 6/7 participants following PF-06372865 or lorazepam administration."

Quantifies the magnitude of response suppression achieved.

Trigger Avoidance and Environmental Modification

Action: Lifestyle Therapy NCIT:C15900

Because seizures are elicited rather than spontaneous in the reflex component this entry models, reducing exposure (distance from screens, avoiding untreated strobe environments, monocular viewing, and polarized or colored lenses that reduce the effective flicker or contrast reaching the retina) is genuinely therapeutic rather than merely precautionary, and is standard advice alongside medication.

Mechanism Target:

INHIBITS Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation

Show evidence (1 reference)

PMID:34221545 SUPPORT Other

"Treatment includes antiseizure medication, commonly valproate or levetiracetam, along with lifestyle modifications, and when amenable, surgical intervention."

Places lifestyle modification alongside pharmacotherapy as a standard component of treatment for reflex epilepsies, the category photosensitive epilepsy belongs to. Evidence source is OTHER because this is a narrative review, not a primary cohort or case study.

🌍

Environmental Factors

1

Intermittent Photic Stimulation and Structured Visual Patterns

Structured, high-contrast patterns (stripes, checkerboards) are a related and well-documented trigger, sometimes acting even under constant illumination without flicker, but ECTO was searched and has no dedicated exposure term for pattern stimulation distinct from visible light exposure in general; binding one here would misrepresent what ECTO:0000007 actually covers, so pattern sensitivity is described in prose only rather than given its own exposure_term.

Flickering light (natural, such as sunlight through trees or on water, or artificial, such as strobe lighting, television, and video games) and structured high-contrast patterns are the reproducible triggers that define this entry. MONDO's own logical definition of photosensitive epilepsy binds the visible-light exposure directly to the disease concept, which this environmental entry mirrors with a pathograph link rather than only a textual description.

Show evidence (1 reference)

PMID:25783594 SUPPORT Human Clinical

"Photosensitivity is a heritable abnormal cortical response to flickering light, manifesting as particular electroencephalographic changes, with or without seizures."

Establishes flickering light exposure as the trigger of the abnormal cortical response that defines photosensitivity, the general claim this environmental entry as a whole makes.

Mechanism Target:

TRIGGERS Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation — Delivery of intermittent photic stimulation, at an individually variable flicker-frequency range, is the direct proximate trigger of the abnormal cortical response that this entry's pathophysiology chain begins with; it is also the basis of the standard diagnostic EEG provocation procedure.

Show evidence (1 reference)

PMID:31526678 SUPPORT Human Clinical

"69.9% patients were evoked by frequency ranged 8 Hz-25 Hz, with accompanying seizures in 13 patients."

Quantifies the flicker-frequency range that triggers the cortical response in a large prospective cohort, directly supporting the TRIGGERS relationship asserted here.

🔬

Diagnosis

2

Electroencephalography with Intermittent Photic Stimulation

The core diagnostic investigation, and a deliberately provocative one: a standardized flash sequence across a range of frequencies is delivered during EEG recording specifically to elicit the photoparoxysmal response, with and without eye closure, since eye closure itself can gate the response.

Electroencephalography NCIT:C38054

Show evidence (1 reference)

PMID:31526678 SUPPORT Human Clinical

"6 of 9 patients with eyes closure sensitivity experienced epileptic seizures during IPS."

Documents eye closure as a specific, separately assessed component of the standard intermittent photic stimulation protocol.

Virtual Reality and Machine Learning-Assisted Photoparoxysmal Response Detection

An emerging research technique, not yet clinical standard of care, that adds a programmable virtual reality stimulation platform and AI-based automatic EEG scoring on top of the conventional IPS-EEG procedure, aiming to broaden and standardize the range of visual stimuli that can be tested for a photoparoxysmal response beyond the fixed manual flash protocol.

Electroencephalography NCIT:C38054

Show evidence (1 reference)

DOI:10.1007/s00521-022-06940-z SUPPORT Other

"This research focuses on introducing virtual reality (VR) in this context, adding, to the conventional infrastructure a more flexible one that can be programmed and that will allow developing a much wider and richer set of experiments in order to detect neurological illnesses, and to study..."

Describes the VR/AI-augmented IPS-EEG research platform this diagnosis entry models, distinct from and supplementary to the standard manual IPS-EEG protocol described above. Evidence source is OTHER because the paper's contribution is a detection system and methods description, not a report of patient clinical outcomes.

🌍

Epidemiology

4

Proportion of Pediatric Epilepsy Referrals with Photosensitive Epilepsy

In a single-center Chinese pediatric epilepsy service that screened 398 consecutively diagnosed children with video-EEG and intermittent photic stimulation testing, photosensitive epilepsy was found in 31. This is a proportion within an epilepsy-referral cohort ascertained by a specific IPS protocol, not a general-population prevalence estimate.

Show evidence (1 reference)

PMID:36969295 SUPPORT Human Clinical

"PSE accounted for 7.79% (31/398) of children with epilepsy during the observation period in our single epilepsy center."

Direct quantification of the fraction of children with epilepsy who were found to have photosensitive epilepsy in this ascertainment protocol. Retrieved directly from the article's PMID-keyed full text (the earlier DOI-keyed cache entry for the same article was abstract-only; this PMID-keyed fetch resolved the full text).

Onset Age and Sex Ratio in a Pediatric Photosensitive Epilepsy Cohort

In the same 31-patient Chinese pediatric cohort, seizure onset was in early childhood on average, and photosensitive epilepsy was markedly more common in girls than boys, a sex skew paralleled elsewhere in the photosensitivity literature (see the treatments section for a sex difference in valproate pharmacodynamic response).

7.8 +/- 3.28 years onset; male:female 1:3.43 years (onset age); ratio (sex)

Show evidence (2 references)

PMID:36969295 SUPPORT Human Clinical

"Among them, there were 7 males and 24 females; the male to female ratio was 1:3.43."

Direct report of the sex ratio in this pediatric photosensitive epilepsy cohort. Retrieved directly from the article's PMID-keyed full text (the earlier DOI-keyed cache entry for the same article was abstract-only; this PMID-keyed fetch resolved the full text).

PMID:36969295 SUPPORT Human Clinical

"The highest age of incidence ranged from 6 to 11 years with a proportion of 70.96% (22/31, 2 males and 10 females)."

Reports the peak incidence age range in this cohort. The source itself is internally inconsistent here: it states "22/31" for the peak-age-band proportion but then gives a male/female breakdown (2 and 10) that sums to 12, not 22. This is flagged as a discrepancy in the cited source rather than silently resolved in either direction; the female-skew qualitative pattern (2 males versus 10 females in whichever subgroup the breakdown actually describes) is consistent with the sex ratio reported elsewhere in this cohort regardless of which figure is correct.

Age at Onset of the Photosensitivity Trait

Independent of any one syndrome's seizure-onset age, the underlying photosensitivity trait itself (the abnormal photoparoxysmal EEG response) most often first appears in childhood or adolescence, with a peak age at onset around 12 years and onset before age 20 in the great majority of cases. This is a broader, syndrome-agnostic estimate, distinct from the syndrome-specific seizure-onset age reported in the Chinese pediatric cohort above.

Show evidence (1 reference)

PMID:23274161 SUPPORT Other

"Photosensitivity usually begins before the age of 20 years with a peak age at onset at around 12."

States the typical age-of-onset window and peak for the photosensitivity trait itself. Evidence source is OTHER because this is a review article.

Visual Sensitivity Prevalence Varies by Underlying Epilepsy Syndrome

The proportion of epilepsy patients who show visual sensitivity is highly syndrome-dependent rather than a single fixed rate, consistent with this entry's framing of photosensitivity as a trait riding along with different underlying epilepsy syndromes at markedly different rates (from a minority in some syndromes up to the great majority in others, such as juvenile myoclonic epilepsy).

Show evidence (1 reference)

DOI:10.5772/intechopen.1015299 SUPPORT Other

"Depending on the type of epilepsy, visual sensitivity can occur in up to 40% of patients, but this is often not diagnosed or treated."

States the syndrome-dependent range and the practical caveat that visual sensitivity is frequently underdiagnosed even when present. Evidence source is OTHER because this is a book chapter overview, not a primary study.

🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Photosensitive Epilepsy:

Self-Induced (Sunflower) Photosensitive Epilepsy

Overlapping Features A behaviorally distinct entity in which the patient deliberately elicits the photoparoxysmal response by waving fingers in front of the eyes in bright light, rather than passively encountering an environmental trigger. Not modeled as a subtype here (see notes); no MONDO disease_term is bound in this differential-diagnosis block because it names a related concept (MONDO:0100529, Sunflower syndrome) that this entry does not itself curate.

Distinguishing Features

The stimulus is self-generated by hand-waving rather than encountered environmentally.
Behavior is often compulsive and difficult to interrupt, with a described self-reinforcing quality.

Show evidence (1 reference)

PMID:35807051 SUPPORT Other

"Epilepsy with seizures provoked by intermittent light stimulation is a distinct group of epilepsies"

Supports treating photically provoked epilepsies as a distinct group within which self-induced forms are a recognized but behaviorally separate presentation. Evidence source is OTHER because this is a review article.

Fixation-Off Sensitivity Epilepsies

Overlapping Features Epilepsies, such as childhood occipital visual epilepsy, in which removing central visual fixation (eye closure in darkness, or convergence) rather than photic stimulation itself is the gating electrographic phenomenon. Distinguished by the opposite manipulation: photosensitive epilepsy's photoparoxysmal response requires a light stimulus, while fixation-off sensitivity requires the absence of structured foveal vision.

Distinguishing Features

The gating manipulation is loss of central fixation, not delivery of a light or pattern stimulus.
Seizures occur spontaneously rather than being elicited by an external visual trigger.

Show evidence (1 reference)

PMID:35503717 SUPPORT Other

"Epilepsy syndromes beginning in childhood have been divided into three categories: (1) self-limited focal epilepsies, comprising four syndromes: self-limited epilepsy with centrotemporal spikes, self-limited epilepsy with autonomic seizures, childhood occipital visual epilepsy, and..."

Lists childhood occipital visual epilepsy, the fixation-off sensitivity syndrome, alongside photosensitive occipital lobe epilepsy as a separate, nosologically distinct syndrome despite the clinical closeness POLE's own entry discusses in detail.

🔬

Clinical Trials

9

NCT02564029 PHASE_II COMPLETED

Phase 2a proof-of-principle crossover trial of PF-06372865, an alpha2/3/5-subunit-selective GABA-A receptor positive allosteric modulator, against lorazepam and placebo in patients with a stable photoparoxysmal response to intermittent photic stimulation. Published results are the basis for this entry's "Investigational GABAergic Positive Allosteric Modulation" treatment.

Target Phenotypes: EEG with photoparoxysmal response HP:0010852

Show evidence (2 references)

PMID:30877186 SUPPORT Human Clinical

"Both doses of PF-06372865 produced a marked and statistically significant mean reduction in SPR compared to placebo, which was similar in degree to lorazepam."

Primary published efficacy result of this trial, already cited in the treatments section for the same drug.

clinicaltrials:NCT02564029 SUPPORT Other

"PF-06372865 in subjects with photosensitive epilepsy"

ClinicalTrials.gov registration record establishing the trial's identity. Evidence source is OTHER because this is a registration summary, not study results.

NCT00616148 PHASE_II COMPLETED

Phase 2 proof-of-principle trial of a single oral dose of cenobamate (YKP3089) evaluating its ability to abolish or reduce the IPS-induced photoparoxysmal EEG response. Published results are the basis for this entry's cenobamate treatment.

Target Phenotypes: EEG with photoparoxysmal response HP:0010852

Show evidence (2 references)

PMID:31292226 SUPPORT Human Clinical

"CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that, for patients with photosensitive epilepsy, cenobamate suppresses IPS-induced PPR."

The published paper's own evidence classification for the NCT00616148 trial, confirming both this clinical_trials entry and the publication record for the same study. Retrieved directly from the article's PMID-keyed abstract (the earlier DOI-keyed cache entry for the same article lacked full text; this PMID-keyed fetch resolved it).

clinicaltrials:NCT00616148 SUPPORT Other

"The aim of this study is to evaluate the ability of a single oral dose of YKP3089 to abolish or clearly reduce the IPS-induced photo-paroxysmal EEG response in photosensitive epilepsy patients, and to measure the onset and duration of the effect."

ClinicalTrials.gov registration record establishing the trial's identity and design. Evidence source is OTHER because this is a registration summary, not study results.

NCT00609245 PHASE_IV COMPLETED

Phase 4 trial examining whether small intravenous changes in plasma valproic acid concentration alter the photoparoxysmal EEG response, probing the pharmacodynamic dose-response relationship of valproate, this entry's first-line agent, at the level of the EEG biomarker itself.

Target Phenotypes: EEG with photoparoxysmal response HP:0010852

Show evidence (1 reference)

clinicaltrials:NCT00609245 SUPPORT Other

"We are trying to learn if small changes in the amount of a valproate in the blood (given through an IV) will change the way the brain reacts to flashing lights."

ClinicalTrials.gov registration record establishing the trial's identity and design. Evidence source is OTHER because this is a registration summary, not study results.

NCT00401648 PHASE_II COMPLETED

Placebo-controlled, single-blind, multi-center trial of a single oral dose of brivaracetam, exploring its effect on the photoparoxysmal EEG response in photosensitive epileptic subjects.

Target Phenotypes: EEG with photoparoxysmal response HP:0010852

Show evidence (1 reference)

clinicaltrials:NCT00401648 SUPPORT Other

"to assess the effect of brivaracetam on the photoparoxysmal EEG response in photosensitive epileptic subjects"

ClinicalTrials.gov registration record establishing the trial's identity and design. Evidence source is OTHER because this is a registration summary, not study results.

NCT00784212 PHASE_II COMPLETED

Multicenter, single-blind, placebo-controlled proof-of-concept trial of single oral doses of the AMPA/kainate receptor antagonist BGG492 (selurampanel), assessed by its effect on the photoparoxysmal EEG response.

Target Phenotypes: EEG with photoparoxysmal response HP:0010852

Show evidence (1 reference)

clinicaltrials:NCT00784212 SUPPORT Other

"This study will evaluate the efficacy of BGG492 in reducing the sensitivity to flashing lights of patients with photosensitive epilepsy, using EEG as a readout."

ClinicalTrials.gov registration record establishing the trial's identity and design. Evidence source is OTHER because this is a registration summary, not study results.

NCT03686033 PHASE_II TERMINATED

Multicenter, double-blind, randomized, crossover, single-dose trial assessing the pharmacodynamic activity of E2082, measured by suppression of the photoparoxysmal response, in adults with photosensitive epilepsy.

Target Phenotypes: EEG with photoparoxysmal response HP:0010852

Show evidence (1 reference)

clinicaltrials:NCT03686033 SUPPORT Other

"The primary purpose of the study is to assess pharmacodynamic (PD) activity of E2082 as measured by suppression of epileptic photoparoxysmal response (PPR) in the participant's most sensitive eye condition in participants with photosensitive epilepsy, compared to placebo."

ClinicalTrials.gov registration record establishing the trial's identity and design; the trial's status is TERMINATED per ClinicalTrials.gov. Evidence source is OTHER because this is a registration summary, not study results.

NCT05678881 PHASE_I TERMINATED

Phase 1b randomized, double-blind, placebo-controlled crossover trial of inhaled dry powder cannabidiol (RLS103) evaluating safety and suppression of the epileptic photoparoxysmal response.

Target Phenotypes: EEG with photoparoxysmal response HP:0010852

Show evidence (1 reference)

clinicaltrials:NCT05678881 SUPPORT Other

"The purpose of this study is to evaluate RLS103 for safety and suppression of the epileptic photoparoxysmal response compared to placebo."

ClinicalTrials.gov registration record establishing the trial's identity and design; the trial's status is TERMINATED per ClinicalTrials.gov. Evidence source is OTHER because this is a registration summary, not study results.

NCT06525649 PHASE_I COMPLETED

Double-blind, randomized, crossover trial examining suppression of the photoparoxysmal EEG response with two doses of NPT 2042 compared to placebo in approximately five adults with a known stable photoparoxysmal response.

Target Phenotypes: EEG with photoparoxysmal response HP:0010852

Show evidence (1 reference)

clinicaltrials:NCT06525649 SUPPORT Other

"A double-blind, placebo-controlled, crossover trial to investigate the PPR of approximately 5 subjects with a known stable PPR on EEG, using 2 doses of NPT 2042 compared to placebo."

ClinicalTrials.gov registration record establishing the trial's identity and design. Evidence source is OTHER because this is a registration summary, not study results.

NCT04076410 NOT_APPLICABLE UNKNOWN

Pediatric trial comparing four new spectral filter lenses to the existing Zeiss Clarlet Z1 lens for reducing the photoparoxysmal response, in patients 5-18 years old referred for EEG with IPS/pattern stimulation. This is the non-pharmacological, device-based counterpart to this entry's drug trials, testing the same trigger-avoidance/environmental-modification principle described in the treatments section. Registry status was last recorded as UNKNOWN by ClinicalTrials.gov.

Target Phenotypes: EEG with photoparoxysmal response HP:0010852

Show evidence (1 reference)

clinicaltrials:NCT04076410 SUPPORT Other

"To determine whether four new lenses with different spectral characteristics are not inferior in efficacy to Z1 to reduce the PPRs in patients with PSE."

ClinicalTrials.gov registration record establishing the trial's identity and primary objective. Evidence source is OTHER because this is a registration summary, not study results.

🐁

Animal Models

2

Papio papio photosensitive baboon

The classic naturally occurring primate model of generalized photosensitive epilepsy: colonies of Papio papio baboons show a heritable predisposition to generalized epileptiform discharges and motor seizures on intermittent photic stimulation, closely paralleling the human photoparoxysmal response, and have been used for decades to study visual-network propagation and antiseizure pharmacology.

Species

Papio papio (baboon)

Genotype

Naturally occurring, heritable generalized photosensitivity trait; no causal mutation has yet been identified.

Publication

PMID:26875109

Pathograph links

Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation recapitulates fidelity: moderate Reproduces the core trait this entry's pathophysiology chain begins with -- a heritable cortical hyperexcitability to flickering light -- in a species phylogenetically closer to humans than the rodent and avian models available for this trait.

Limitations: No causal genetic lesion has been identified in Papio papio despite a presumed genetic etiology, so the model cannot yet be used to test any specific human candidate variant (including CHD2), and primate colony availability sharply limits its use relative to zebrafish or mouse models.

Readouts

Ictal and Interictal Epileptiform EEG Discharges During Intermittent Light Stimulation

Interpretation: The electrographic readout by which photosensitive, epileptic (PS) baboon colonies are distinguished from asymptomatic control (CTL) animals: ictal and interictal epileptiform EEG discharges occurring during intermittent light stimulation. Renamed from an earlier, more specific "motor seizure response" framing after the cited source was found to establish the electrographic discharge readout directly but not a separately quantified motor-seizure measurement.

Show evidence (2 references)

PMID:22276085 SUPPORT Model Organism

"our group utilized functional positron emission tomography (PET) to compare cerebral blood flow (CBF) changes occurring during intermittent light stimulation (ILS) and rest between baboons photosensitive, epileptic (PS) and asymptomatic, control (CTL) animals."

Establishes the intermittent light stimulation (ILS) paradigm and the photosensitive-epileptic (PS) versus asymptomatic-control (CTL) baboon classification this readout depends on.

+ 1 more reference

Show evidence (1 reference)

PMID:26875109 SUPPORT Other

"No specific mutation has been found in Papio papio baboon, although a genetic etiology is likely."

Establishes Papio papio as a naturally occurring photosensitive-epilepsy model with a presumed but still unidentified genetic basis, the basis for both the RECAPITULATES relationship and its stated limitation. Evidence source is OTHER because this is a narrative review, not a primary study of the baboon colony itself.

Show evidence (2 references)

PMID:22276085 SUPPORT Model Organism

"our group utilized functional positron emission tomography (PET) to compare cerebral blood flow (CBF) changes occurring during intermittent light stimulation (ILS) and rest between baboons photosensitive, epileptic (PS) and asymptomatic, control (CTL) animals."

Establishes the photosensitive baboon as a naturally occurring model in which intermittent light stimulation reproducibly distinguishes a photosensitive-epileptic phenotype from asymptomatic controls, the basis for the RECAPITULATES relationship.

PMID:26875109 SUPPORT Other

"No specific mutation has been found in Papio papio baboon, although a genetic etiology is likely."

Supports Papio papio as an informative naturally occurring model for the visual cortical hyperexcitability node. Evidence source is OTHER because this is a narrative review, not a primary study of the baboon colony itself.

Fepi (Fayoumi) photosensitive chicken line

A heritable avian model of photic and audiogenic reflex epilepsy in which a splice-site mutation in SV2A produces spontaneous, photically triggered seizures, providing a genetically defined counterpoint to the still-genetically-unresolved Papio papio model. Brain-chimera transfer experiments in this same strain, however, localize its seizure generator to the brain stem rather than to visual cortex, which is why this model is scored FAILS_TO_RECAPITULATE below rather than PARTIALLY_RECAPITULATES.

Species

Gallus gallus (Fayoumi-derived Fepi chicken strain)

Genotype

Recessive autosomal mutation in the acceptor site of SV2A intron 2 (synaptic vesicle glycoprotein 2A, the levetiracetam binding target), homozygous

Publication

PMID:22046416

Pathograph links

Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation fails to recapitulate fidelity: low Reproduces heritable photic (and audiogenic) seizure susceptibility linked to a defined synaptic gene, but living neural-chimera experiments in this strain -- replacing specific embryonic brain vesicles with their Fepi-donor equivalents -- localize the seizure generator to the brain stem (prosencephalon and mesencephalon), not to the visual cortex this entry's pathophysiology chain describes.

Limitations: The original authors' own conclusion places the Fepi seizure generator in the brain stem: substituting only the mesencephalon transfers the motor seizure, substituting only the prosencephalon transfers interictal paroxysmal activity, and total transfer requires substituting both. This is a fundamentally different anatomical locus from the visual-cortex and thalamocortical mechanism this entry establishes for human photosensitive epilepsy (see the Reduced Alpha-Rhythm Network Inhibition and Visual Cortical Hyperexcitability nodes above), not merely a difference of degree from avian brain architecture. It is recorded here as a documented negative result rather than omitted, so a future curator does not re-propose the Fepi line as a cortical model of human photosensitive epilepsy. SV2A is also not among the genes implicated in human photosensitive epilepsy -- CHD2, the best-established human risk gene curated in this entry, is unrelated to SV2A.

Show evidence (1 reference)

PMID:15260383 SUPPORT Model Organism

"We conclude that the Fepi is a good model of brain stem reflex epilepsy and suggest that the brain stem is a generator of some other animal and human genetic reflex "epileptic syndromes"."

The original authors' own conclusion, directly supporting the FAILS_TO_RECAPITULATE relationship: the Fepi model's own investigators locate its generator in the brain stem, not the visual cortex.

Show evidence (3 references)

PMID:22046416 SUPPORT Model Organism

"we report that a mutation in the acceptor site of the second intron of SV2A (the gene encoding synaptic vesicle glycoprotein 2A) is causing photosensitive reflex epilepsy in a unique vertebrate model, the Fepi chicken strain, a spontaneous model where the neurological disorder is inherited as an..."

The primary genetic study identifying the causal SV2A splice-site mutation in the Fepi chicken strain, replacing the earlier, secondary-review-only sourcing for this model with the original report.

PMID:15260383 SUPPORT Model Organism

"The Fayoumi strain of chickens (Fepi) carries a recessive autosomal gene mutation in which homozygotes are afflicted with a photogenic and audiogenic reflex epilepsy."

The classic description of the Fepi strain as a photogenic (and audiogenic) reflex epilepsy model, cited alongside the later SV2A gene-identification study above.

PMID:26875109 SUPPORT Other

"Mutation in synaptic vesicle glycoprotein 2A was found in another animal model of photosensitivity (Fayoumi chickens)."

Supports the Fayoumi chicken line as a genetically defined photosensitivity model. Evidence source is OTHER because this is a narrative review, not a primary study of the chicken line itself.

{ }

Source YAML

click to show

name: Photosensitive Epilepsy
creation_date: "2026-08-26T00:00:00Z"
category: Complex
description: >-
  Epilepsy in which seizures are reproducibly triggered by intermittent
  photic stimulation, or by structured patterns, rather than occurring purely
  spontaneously. Photosensitivity itself is a heritable trait: an abnormal
  cortical response to flickering light or contrast pattern, visible on EEG as
  the photoparoxysmal response, that exists on a spectrum from an isolated
  laboratory finding with no clinical seizures to fully expressed reflex
  epilepsy. This entry models photosensitive epilepsy as a root concept with
  subtypes, because clinically it is not one thing: a minority of patients
  have "pure" photosensitive epilepsy in which visual stimuli are the only
  identified trigger, but far more often photosensitivity is a trait that
  rides along with a distinct epilepsy syndrome that also has spontaneous,
  unprovoked seizures, most archetypally eyelid myoclonia with absences
  (Jeavons syndrome), and also juvenile myoclonic epilepsy, Dravet syndrome,
  and the progressive myoclonic epilepsies. CHD2 is the best-established
  single-gene contributor identified to date, notable because it does not
  encode an ion channel, which points to chromatin regulation of neuronal
  excitability as a mechanism distinct from the channelopathies that dominate
  the rest of the epilepsy genetics literature.
parents:
  - Epilepsy
  - Neurological Disease
synonyms:
  - PSE
  - photoparoxysmal response
  - photogenic epilepsy
  - photic-induced epilepsy
classifications:
  harrisons_chapter:
    - classification_value: NEUROLOGIC
      notes: >-
        A reflex epilepsy defined by its trigger rather than by a single
        seizure type or EEG pattern; it cuts across the generalized/focal
        divide because most affected patients carry an underlying genetic
        generalized epilepsy syndrome while a minority have a focal
        (occipital) reflex syndrome.
disease_term:
  preferred_term: photosensitive epilepsy
  term:
    id: MONDO:0015643
    label: photosensitive epilepsy
mappings:
  mondo_mappings:
    - term:
        id: MONDO:0015643
        label: photosensitive epilepsy
      mapping_predicate: skos:exactMatch
      mapping_source: MONDO
      mapping_justification: >-
        MONDO:0015643 is defined as "An epilepsy characterized by seizures
        triggered by visual stimuli that form patterns in space or time, such
        as flashing lights," is cross-referenced to OMIM phenotypic series
        PS132100, and carries a formal RO:0009501 (has disposition to bear a
        role) relationship to ECTO:0000007 (exposure to visible light
        radiation) in its own logical definition, which is the same
        relationship this entry's environmental section encodes as
        influences_mechanisms.
has_subtypes:
  - name: Pure Photosensitive Epilepsy
    display_name: Pure (Isolated) Photosensitive Epilepsy
    description: >-
      Photically triggered seizures with no other spontaneous epilepsy
      syndrome: intermittent photic stimulation, and often a specific
      flicker-frequency range, is the only identified seizure trigger, and
      seizures do not occur in its absence. This is the reflex-epilepsy end
      of the spectrum. No dedicated MONDO identifier is bound for this
      subtype beyond the root MONDO:0015643 concept itself: MONDO's own
      children of photosensitive epilepsy (photoparoxysmal response 1-3,
      part of OMIM phenotypic series PS132100) are genetic-linkage loci
      mapped from family studies of the photoparoxysmal EEG trait, not a
      distinct clinical entity matching this description, so binding one of
      them here would overstate what they represent.
    evidence:
      - reference: PMID:35807051
        reference_title: >-
          Photo-Dependent Reflex Seizures-A Scoping Review with Proposal of
          Classification.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Epilepsy with seizures provoked by intermittent light stimulation
          is a distinct group of epilepsies
        explanation: >-
          A recent scoping review treats photically provoked epilepsy as its
          own distinct group, supporting a pure reflex form separate from
          photosensitivity riding along with another syndrome. Evidence
          source is OTHER because this is a review article.
  - name: Photosensitive Occipital Lobe Epilepsy
    subtype_term:
      preferred_term: photosensitive occipital lobe epilepsy
      term:
        id: MONDO:0100021
        label: photosensitive occipital lobe epilepsy
    description: >-
      A focal reflex epilepsy in which flickering light or structured
      pattern, classically television or video games, triggers a seizure
      that begins with elementary visual hallucinations and is accompanied by
      an occipitally confined (rather than generalized) photoparoxysmal
      response. Already fully curated as its own dismech entry; see
      kb/disorders/Photosensitive_Occipital_Lobe_Epilepsy.yaml for the
      detailed pathophysiology, phenotypes, and evidence. This subtype block
      exists to place that entry in the photosensitive-epilepsy family and
      is deliberately not a duplicate of its content.
    evidence:
      - reference: PMID:35503717
        reference_title: >-
          International League Against Epilepsy classification and
          definition of epilepsy syndromes with onset in childhood: Position
          paper by the ILAE Task Force on Nosology and Definitions.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Epilepsy syndromes beginning in childhood have been divided into
          three categories: (1) self-limited focal epilepsies, comprising
          four syndromes: self-limited epilepsy with centrotemporal spikes,
          self-limited epilepsy with autonomic seizures, childhood occipital
          visual epilepsy, and photosensitive occipital lobe epilepsy
        explanation: >-
          Establishes photosensitive occipital lobe epilepsy as a current
          ILAE-recognized syndrome, the same citation already used in its own
          entry to ground its nosological status. Evidence source is OTHER
          because this is a nosology position paper, not a primary study.
  - name: Photosensitivity in Juvenile Myoclonic Epilepsy
    subtype_term:
      preferred_term: juvenile myoclonic epilepsy
      term:
        id: MONDO:0009696
        label: juvenile myoclonic epilepsy
    description: >-
      Juvenile myoclonic epilepsy (JME) is fully curated as its own dismech
      entry (kb/disorders/Juvenile_Myoclonic_Epilepsy.yaml); this subtype
      block scopes only the photosensitivity trait within it. Photosensitive
      seizures and an abnormal photoparoxysmal response are common in JME,
      but unlike pure photosensitive epilepsy, most patients also have
      spontaneous myoclonic and generalized tonic-clonic seizures on
      awakening that are not photically triggered, so JME as a whole conforms
      to the module's unprovoked-seizure terminal node in its own entry in a
      way that this photosensitivity-specific subtype block does not
      restate.
    evidence:
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          We sought CHD2 variants in 238 exomes from familial genetic
          generalized epilepsies, and in other public exome data sets.
        explanation: >-
          Documents that the photosensitivity genetics work covered familial
          genetic generalized epilepsies, the category JME belongs to, as
          part of establishing where CHD2 variation contributes across the
          photosensitive-epilepsy spectrum rather than only in the archetypal
          syndrome.
  - name: Photosensitivity as the Archetypal Syndrome, Jeavons Syndrome
    display_name: Jeavons Syndrome (Eyelid Myoclonia with Absences)
    subtype_term:
      preferred_term: epilepsy with eyelid myoclonia
      term:
        id: MONDO:0015346
        label: epilepsy with eyelid myoclonia
    description: >-
      Jeavons syndrome is fully curated as its own dismech entry
      (kb/disorders/Jeavons_Syndrome.yaml). It is placed here as a subtype
      because the literature identifies it as the single syndrome in which
      photosensitivity is not merely a common accompanying trait but is
      part of the syndrome's own defining triad, alongside eyelid myoclonia
      and eye-closure-induced EEG paroxysms, and because it is the syndrome
      in which the CHD2 gene-photosensitivity association was first and most
      strongly established.
    genes:
      - preferred_term: CHD2
        term:
          id: hgnc:1917
          label: CHD2
    evidence:
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Among epilepsy syndromes, there was over-representation of unique
          CHD2 variants (3/36 cases) in the archetypal photosensitive
          epilepsy syndrome, eyelid myoclonia with absences (P = 3.50 ×
          10(-4))
        explanation: >-
          States directly that eyelid myoclonia with absences (Jeavons
          syndrome) is the archetypal photosensitive epilepsy syndrome and
          gives the statistical basis for the CHD2 association being
          strongest there.
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          CHD2 mutation is the first identified cause of the archetypal
          generalized photosensitive epilepsy syndrome, eyelid myoclonia with
          absences.
        explanation: >-
          The authors' own summary statement naming CHD2 as the first
          identified genetic cause specifically of Jeavons syndrome.
  - name: Photosensitivity in Dravet Syndrome
    subtype_term:
      preferred_term: Dravet syndrome
      term:
        id: MONDO:0100135
        label: Dravet syndrome
    description: >-
      Dravet syndrome is fully curated as its own dismech entry
      (kb/disorders/Dravet_syndrome.yaml); this subtype block scopes only the
      photosensitivity trait within it. Photosensitivity in Dravet syndrome
      (historically described under the older name severe myoclonic epilepsy
      in infancy, SMEI) has been shown to follow a different physiological
      rule from most other photosensitive epilepsies: the photoparoxysmal
      response tends to depend on the total quantity of light delivered
      rather than on its wavelength, unlike the wavelength-dependent pattern
      more typical of localization-related and symptomatic generalized
      epilepsies.
    evidence:
      - reference: PMID:10496248
        reference_title: >-
          Photosensitive epilepsies and pathophysiologic mechanisms of the
          photoparoxysmal response.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Four of the six photosensitive SMEI patients had
          quantity-of-light-dependent PPRs.
        explanation: >-
          Directly reports the quantity-of-light-dependent mechanism found in
          most photosensitive severe myoclonic epilepsy in infancy (Dravet
          syndrome) patients in this cohort, distinguishing it from the
          wavelength-dependent mechanism seen in other syndromes in the same
          study.
  - name: Photosensitivity in the Progressive Myoclonic Epilepsies
    subtype_term:
      preferred_term: progressive myoclonus epilepsy
      term:
        id: MONDO:0020074
        label: progressive myoclonus epilepsy
    description: >-
      The progressive myoclonic epilepsies (individually curated as their own
      dismech entries, e.g. kb/disorders/Progressive_Myoclonic_Epilepsy_Type_7.yaml
      and kb/disorders/Progressive_Myoclonic_Epilepsy_Type_8.yaml) frequently
      show a photoparoxysmal EEG response, most classically in
      Unverricht-Lundborg disease. Unlike the genetic generalized epilepsies
      above, photosensitivity here occurs against a background of a
      degenerative, worsening disease course, and both the spike-wave
      discharges and the photoparoxysmal response have been reported to
      diminish again as the disease reaches adulthood.
    evidence:
      - reference: PMID:18358403
        reference_title: Unverricht-Lundborg progressive myoclonus epilepsy in Oman.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Slowing of background activity, generalized spike-wave discharges,
          and photoparoxysmal responses were evident in all patients'
          electroencephalograms.
        explanation: >-
          Documents the photoparoxysmal response as a universal EEG finding
          in this confirmed Unverricht-Lundborg disease cohort, establishing
          photosensitivity as a feature of the progressive myoclonic
          epilepsies.
      - reference: PMID:18358403
        reference_title: Unverricht-Lundborg progressive myoclonus epilepsy in Oman.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Spike-wave discharges and photoparoxysmal responses tended to
          disappear in adulthood.
        explanation: >-
          Reports the age-dependent attenuation of the photoparoxysmal
          response in this progressive disease, a course distinct from the
          other subtypes in this entry.
references:
  - reference: PMID:35807051
    title: >-
      Photo-Dependent Reflex Seizures-A Scoping Review with Proposal of
      Classification.
  - reference: PMID:10496248
    title: >-
      Photosensitive epilepsies and pathophysiologic mechanisms of the
      photoparoxysmal response.
  - reference: PMID:25783594
    title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
  - reference: PMID:26395125
    title: Overactive visuomotor connections underlie the photoparoxysmal response. A TMS study.
  - reference: PMID:31526678
    title: >-
      Photosensitive epilepsy and photosensitivity of patients with possible
      epilepsy in Chinese Han race: A prospective multicenter study.
  - reference: PMID:30877186
    title: 'Photosensitive epilepsy: Robust clinical efficacy of a selective GABA potentiator.'
  - reference: PMID:34221545
    title: Reflex Epilepsy.
  - reference: PMID:35503717
    title: >-
      International League Against Epilepsy classification and definition of
      epilepsy syndromes with onset in childhood: Position paper by the ILAE
      Task Force on Nosology and Definitions.
notes: >-
  Sourcing. Drafted from primary literature (Takahashi 1999, Galizia et al.
  2015, Strigaro et al. 2015, Bai et al. 2019, Gurrell et al. 2019, and the
  2022 reflex-seizure scoping review), then cross-checked against a
  deep-research report generated with the falcon provider (Edison
  Scientific), committed as
  research/Photosensitive_Epilepsy-deep-research-falcon.md.

  Scope note on eye closure and self-induction. This entry models
  light-triggered and pattern-triggered photosensitivity. It does not model
  self-induced photosensitive epilepsy (Sunflower syndrome, MONDO:0100529),
  in which patients deliberately wave a hand in front of the eyes in bright
  light to self-elicit the response, as a separate subtype: that is a
  distinct behavioral entity layered on top of an underlying
  photosensitivity trait rather than a differently mechanistically triggered
  epilepsy, and it does not yet have its own dismech curation.

  What is deliberately not duplicated here. Five of the six named subtypes
  (photosensitive occipital lobe epilepsy, juvenile myoclonic epilepsy,
  Jeavons syndrome, Dravet syndrome, and the progressive myoclonic
  epilepsies) already have full, independently curated dismech entries. Each
  subtype block here is intentionally thin: it exists to place that entry in
  the photosensitive-epilepsy family via subtype_term and to describe only
  the photosensitivity-specific literature, not to re-derive the full
  pathophysiology, phenotype list, or treatment plan already curated in the
  linked file. A curator editing the photosensitivity content of, say,
  Dravet syndrome should edit both this subtype block and the corresponding
  section of Dravet_syndrome.yaml, since the schema does not provide
  inheritance between them (the same non-DRY relationship that conforms_to
  has to mechanism modules).
inheritance:
  - name: Genetically complex, polygenic trait with identified contributing loci
    description: >-
      Photosensitivity itself is a heritable EEG trait most consistent with
      complex, polygenic inheritance rather than a single Mendelian pattern.
      CHD2 is the best-established single-gene risk-factor contributor
      identified to date (see genetic section), but unique CHD2 variants
      explain only a minority of photosensitive-epilepsy cases, and the
      condition as a whole is genetically heterogeneous. Individual named
      subtypes carry their own, separately curated inheritance patterns in
      their own entries.
    evidence:
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          We identified 11 unique variants in the 580 individuals with
          photosensitive epilepsies and 128 unique variants in the 34 427
          controls: unique CHD2 variation is over-represented in cases
          overall (P = 2.17 × 10(-5))
        explanation: >-
          Quantifies CHD2 as a statistically significant but partial
          contributor (11 of 580 cases carried a unique variant), supporting
          a complex rather than single-gene-necessary inheritance model for
          photosensitivity as a whole.
pathophysiology:
  - name: Reduced Alpha-Rhythm Network Inhibition
    biological_scale: TISSUE
    conforms_to: "epilepsy_excitation_inhibition_imbalance#Excitation-Inhibition Imbalance"
    description: >-
      Simultaneous EEG-fMRI shows that photosensitive patients have reduced
      inhibition of the resting-state networks that generate the posterior
      alpha rhythm, the brain's normal idling rhythm, compared with both
      non-photosensitive epilepsy patients and healthy controls. This is a
      baseline network-level abnormality, present outside of stimulation, and
      is the excitation-inhibition-imbalance amplifier step that this entry's
      pathophysiology chain was previously missing: the acute hyperexcitable
      response to flickering light described in the next node is superimposed
      on a cortex whose inhibitory network tone is already reduced.
    notes: >-
      This node deliberately does not carry the module's usual
      Excitation-Inhibition Imbalance annotations, cell_types CL:0000617
      (GABAergic neuron) and biological_processes GO:0007214 (GABA signaling,
      DECREASED). The Vaudano et al. finding modeled here is a network-level
      alpha-rhythm inhibition abnormality measured by resting-state EEG-fMRI,
      not a cellular or molecular claim about GABAergic neurotransmission
      specifically, so binding those GABA-specific terms here would overstate
      what the cited evidence establishes. Recorded here so a future
      conformance audit reads this as a deliberate scope choice rather than
      an incomplete annotation.
    downstream:
      - target: Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation
    evidence:
      - reference: PMID:28334965
        reference_title: >-
          Photosensitive epilepsy is associated with reduced inhibition of
          alpha rhythm generating networks.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          This difference consists of a decreased alpha-related inhibition of
          the visual cortex and sensory-motor networks at rest.
        explanation: >-
          The authors' own statement of the finding this node models: reduced
          alpha-related inhibition of the visual and sensory-motor cortex,
          measured at rest independent of any stimulus, the E/I-imbalance
          amplifier step this entry's pathophysiology chain was missing.
          Retrieved directly from the article's abstract (the earlier
          DOI-keyed cache entry for the same article lacked full text; this
          PMID-keyed fetch resolved it).
      - reference: PMID:28334965
        reference_title: >-
          Photosensitive epilepsy is associated with reduced inhibition of
          alpha rhythm generating networks.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Genetic generalized epilepsy with photosensitivity demonstrated
          significantly greater mean alpha-power with respect to controls and
          other epilepsy groups.
        explanation: >-
          The specific EEG-fMRI measurement distinguishing photosensitive
          from non-photosensitive epilepsy groups, establishing that this
          inhibitory-network abnormality is specific to photosensitivity
          rather than to epilepsy in general.
      - reference: DOI:10.1101/2024.12.21.24319242
        reference_title: >-
          Functional network dynamics in photosensitive epilepsy depend on
          stimulation frequency and photosensitivity type
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          PSE patients showed apparent differences in functional connectivity
          in the PPR band (3-4Hz) with hypoconnected centro-parietal regions
          and hyperconnected anterior and anterio-posterior areas compared to
          HC and PWE for stimulation frequencies 10Hz-20Hz.
        explanation: >-
          Independent EEG connectivity evidence that photosensitive-epilepsy
          networks are abnormally hypoconnected over posterior/centro-parietal
          regions, a network-level correlate consistent with reduced posterior
          inhibitory network tone. Supports is PARTIAL because this preprint
          frames the finding as altered functional connectivity during
          stimulation rather than as reduced inhibition specifically, and it
          remains an unpublished preprint (is_preprint: true in its cache
          record).
  - name: Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation
    biological_scale: TISSUE
    conforms_to: "epilepsy_excitation_inhibition_imbalance#Neuronal Hyperexcitability and Hypersynchrony"
    description: >-
      The root abnormality is a visual cortex, and adjoining parietal
      cortex, that responds to flickering light or a structured pattern with
      an excessive, hypersynchronous discharge rather than a normal evoked
      response. This is a heritable trait present with or without clinical
      seizures, and it is the abnormality that the photoparoxysmal response
      makes visible on EEG.
    locations:
      - preferred_term: primary visual cortex
        term:
          id: UBERON:0002436
          label: primary visual cortex
    biological_processes:
      - preferred_term: abnormally amplified cortical response to visual stimulation
        description: >-
          No GO term is bound here: GO:0050908 ("detection of light stimulus
          involved in visual perception") names retinal phototransduction,
          not the cortical amplitude abnormality this node claims, and no
          better-fitting GO term for cortical visual-response hyperexcitability
          was found, so the claim is kept as free text rather than bound to a
          mismatched term.
        modifier: ABNORMAL
    downstream:
      - target: Photoparoxysmal EEG Response
    evidence:
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Photosensitivity is a heritable abnormal cortical response to
          flickering light, manifesting as particular electroencephalographic
          changes, with or without seizures.
        explanation: >-
          Defines photosensitivity itself as the abnormal cortical response
          this node models, and establishes that it is heritable and exists
          independently of overt seizures.
      - reference: PMID:35807051
        reference_title: >-
          Photo-Dependent Reflex Seizures-A Scoping Review with Proposal of
          Classification.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          we focused on reflex seizures provoked by different factors whose
          common feature is the patient's response to intermittent photic
          stimulation.
        explanation: >-
          States that the common feature across these reflex seizures is the
          patient's cortical response to intermittent photic stimulation,
          which is what this node and the linked environmental exposure both
          describe. Evidence source is OTHER because this is a review
          article.
  - name: Photoparoxysmal EEG Response
    biological_scale: TISSUE
    description: >-
      The electrographic signature elicited by intermittent photic
      stimulation: spike, polyspike, or spike-wave discharges appearing
      during or immediately after the stimulus train, usually with a
      generalized or bilateral field in the syndromes modeled by this entry
      (in contrast to the occipitally confined response of the separately
      curated photosensitive occipital lobe epilepsy subtype). The
      physiological rule governing elicitation differs by underlying
      syndrome: some patients' responses depend on stimulus wavelength, while
      others', notably in Dravet syndrome, depend instead on the total
      quantity of light delivered.
    downstream:
      - target: Visual-to-Motor Cortical Hyperexcitable Spread
    evidence:
      - reference: PMID:10496248
        reference_title: >-
          Photosensitive epilepsies and pathophysiologic mechanisms of the
          photoparoxysmal response.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          The authors found two types of pathophysiologic mechanisms of PPRs
          (wavelength-dependent PPRs and quantity-of-light-dependent PPRs) in
          patients with idiopathic generalized epilepsy and hereditary
          dentatorubral-pallidoluysian atrophy.
        explanation: >-
          Establishes the two distinct physiological mechanisms that
          generate the photoparoxysmal response and ties them to different
          underlying epilepsy syndromes, which is the basis for this node's
          claim that the eliciting rule is syndrome-dependent.
      - reference: PMID:10496248
        reference_title: >-
          Photosensitive epilepsies and pathophysiologic mechanisms of the
          photoparoxysmal response.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          The type of pathophysiologic mechanism for eliciting PPRs by
          low-luminance photic stimulation was closely related to the
          classification of the epilepsy syndrome.
        explanation: >-
          The authors' own concluding statement linking PPR-eliciting
          mechanism to epilepsy syndrome classification.
      - reference: PMID:31526678
        reference_title: >-
          Photosensitive epilepsy and photosensitivity of patients with
          possible epilepsy in Chinese Han race: A prospective multicenter
          study.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          69.9% patients were evoked by frequency ranged 8 Hz-25 Hz, with
          accompanying seizures in 13 patients.
        explanation: >-
          Quantifies the flicker-frequency range that elicits the response in
          a large prospective cohort and the minority in whom the
          electrographic response is accompanied by a clinical seizure.
  - name: Visual-to-Motor Cortical Hyperexcitable Spread
    biological_scale: TISSUE
    description: >-
      Once elicited in visual cortex, the discharge does not stay contained:
      transcranial magnetic stimulation studies show that the normal
      inhibitory connection from primary visual cortex to primary motor
      cortex is lost specifically in patients who currently show a
      photoparoxysmal response, so that motor cortex responds excessively to
      visual-cortex input. This overactive visuomotor connection is proposed
      as the mechanistic bridge between an occipital electrographic event and
      the myoclonic and generalized motor phenomena that follow it.
    locations:
      - preferred_term: primary motor cortex
        term:
          id: UBERON:0001384
          label: primary motor cortex
    downstream:
      - target: Photically Provoked Seizure Generation
    evidence:
      - reference: PMID:26395125
        reference_title: >-
          Overactive visuomotor connections underlie the photoparoxysmal
          response. A TMS study.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          IGE patients with a PPR have an overactive functional response of
          M1 to inputs traveling from V1.
        explanation: >-
          The authors' direct conclusion establishing the overactive
          visual-to-motor cortical connection this node models.
      - reference: PMID:26395125
        reference_title: >-
          Overactive visuomotor connections underlie the photoparoxysmal
          response. A TMS study.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          This was not true in PPR-positive IGE patients, in whom this type
          of physiologic inhibition was significantly (p < 0.05) reduced.
        explanation: >-
          The specific measurement behind the claim: the normal V1-to-M1
          inhibitory effect measured by TMS was significantly reduced only in
          patients currently showing a photoparoxysmal response, not in
          photonegative patients or healthy controls.
  - name: Photically Provoked Seizure Generation
    biological_scale: ORGANISM
    description: >-
      The clinical seizure: myoclonic jerks, absence, or generalized
      tonic-clonic activity emerging once the visuomotor spread recruits
      enough cortex to produce a symptom. Which seizure type predominates
      depends on the underlying syndrome rather than on the trigger itself,
      which is why the same photic stimulus produces eyelid myoclonia in
      Jeavons syndrome, myoclonic jerks in juvenile myoclonic epilepsy, and
      occipital visual seizures in photosensitive occipital lobe epilepsy.
    downstream:
      - target: Recurrent Visually Provoked Seizures
    evidence:
      - reference: PMID:31526678
        reference_title: >-
          Photosensitive epilepsy and photosensitivity of patients with
          possible epilepsy in Chinese Han race: A prospective multicenter
          study.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          6 of 9 patients with eyes closure sensitivity experienced epileptic
          seizures during IPS.
        explanation: >-
          Direct observation of the electrographic-to-clinical transition,
          in this case in patients with eye-closure sensitivity, a subset of
          the photosensitivity trait.
  - name: Recurrent Visually Provoked Seizures
    biological_scale: ORGANISM
    description: >-
      The clinical epilepsy at its purest: seizures reliably and repeatedly
      elicited by the same class of visual stimulus. This node deliberately
      does not conform to the module's Recurrent Unprovoked Seizures node;
      see the attached discussion. It describes the reflex component common
      to every subtype in this entry, not the full clinical picture of any
      one of them; the subtype blocks and their linked entries additionally
      describe spontaneous, unprovoked seizures where those occur.
    evidence:
      - reference: PMID:34221545
        reference_title: Reflex Epilepsy.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Reflex seizures (RS) are epileptic events that are objectively and
          consistently elicited in response to a specific afferent stimulus
          or by an activity of the patient.
        explanation: >-
          Defines the reflex seizure by its consistent elicitation, the
          property that makes photically provoked seizures provoked by
          definition and grounds the module-boundary discussion attached to
          this node. Evidence source is OTHER because this is a narrative
          review, not a primary cohort or case study.
phenotypes:
  - category: Neurological
    name: Visually Provoked Seizures
    description: >-
      Seizures reliably elicited by flickering light or a structured visual
      pattern.
    phenotype_term:
      preferred_term: Visually-induced seizure
      term:
        id: HP:0020216
        label: Visually-induced seizure
    frequency: VERY_FREQUENT
    evidence:
      - reference: PMID:35807051
        reference_title: >-
          Photo-Dependent Reflex Seizures-A Scoping Review with Proposal of
          Classification.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Photo-dependent reflex seizures make up the majority of this type
          of disorder among reflex seizures.
        explanation: >-
          Establishes visually provoked seizures as the majority form of
          reflex seizures overall, supporting a very frequent band for this
          defining feature. Evidence source is OTHER because this is a
          review article.
  - category: Neurological
    name: Photoparoxysmal Response on Intermittent Photic Stimulation
    description: >-
      Generalized or bilateral spike, polyspike, or spike-wave discharges
      elicited on EEG by intermittent photic stimulation, the laboratory
      correlate of the trigger.
    phenotype_term:
      preferred_term: EEG with photoparoxysmal response
      term:
        id: HP:0010852
        label: EEG with photoparoxysmal response
    evidence:
      - reference: PMID:31526678
        reference_title: >-
          Photosensitive epilepsy and photosensitivity of patients with
          possible epilepsy in Chinese Han race: A prospective multicenter
          study.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Of the 73 patients with PPR to IPS, 48 were female.
        explanation: >-
          Documents a cohort of 73 patients ascertained specifically by their
          PPR to IPS, supporting that this EEG finding is the diagnostic
          criterion by which patients enter this and comparable cohorts. No
          frequency band is set here: this sentence quantifies the cohort's
          sex distribution, not what fraction of photosensitive-epilepsy
          patients show a PPR, and no cached reference in this entry gives a
          quotable population-level PPR frequency to justify one.
  - category: Neurological
    name: Photosensitive Myoclonic Seizures
    description: >-
      Myoclonic jerks provoked by photic stimulation, the predominant seizure
      type in the genetic generalized photosensitive syndromes such as
      Jeavons syndrome and juvenile myoclonic epilepsy.
    phenotype_term:
      preferred_term: Photosensitive myoclonic seizure
      term:
        id: HP:0001327
        label: Photosensitive myoclonic seizure
    frequency: FREQUENT
    evidence:
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          We studied 580 individuals with epilepsy and either photosensitive
          seizures or abnormal photoparoxysmal response on
          electroencephalography, or both, and 55 individuals with
          photoparoxysmal response but no seizures.
        explanation: >-
          Establishes photosensitive seizures, predominantly myoclonic in the
          genetic generalized syndromes this cohort was drawn from, as a
          recurrent clinical finding across a large ascertained sample.
  - category: Neurological
    name: Photosensitive Tonic-Clonic Seizures
    description: >-
      Bilateral tonic-clonic seizures provoked by photic stimulation, seen
      when the propagated discharge engages a sufficiently large cortical and
      subcortical network rather than remaining restricted to a myoclonic
      jerk.
    phenotype_term:
      preferred_term: Photosensitive tonic-clonic seizure
      term:
        id: HP:0007207
        label: Photosensitive tonic-clonic seizure
    frequency: FREQUENT
    evidence:
      - reference: PMID:35807051
        reference_title: >-
          Photo-Dependent Reflex Seizures-A Scoping Review with Proposal of
          Classification.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Although generalized seizures, such as myoclonic, tonic-clonic, and
          absence, are the most common, PPR has also been found in patients
          with occipital epilepsy and temporal lobe epilepsy
        explanation: >-
          States directly that tonic-clonic seizures are, along with
          myoclonic and absence seizures, among the most common seizure types
          in patients with PPR, supporting a frequent rather than merely
          occasional band. Evidence source is OTHER because this is a
          scoping review, not a primary cohort study. Replaces an earlier
          citation that quoted an eye-closure-sensitivity sentence unrelated
          to seizure type and miscounted 6 of 9 (67%) as "only a minority."
      - reference: PMID:31526678
        reference_title: >-
          Photosensitive epilepsy and photosensitivity of patients with
          possible epilepsy in Chinese Han race: A prospective multicenter
          study.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          69.9% patients were evoked by frequency ranged 8 Hz-25 Hz, with
          accompanying seizures in 13 patients.
        explanation: >-
          Quantifies that a clinical seizure of any type (not specifically
          tonic-clonic) accompanied the electrographic response in only 13 of
          the 73 PPR-positive patients (about 18%), the minority figure this
          paper actually supports; PARTIAL because the seizure type is not
          broken down by semiology in this sentence.
  - category: Neurological
    name: Eyelid Myoclonia Seizures
    subtype: Photosensitivity as the Archetypal Syndrome, Jeavons Syndrome
    description: >-
      Brief, rapid eyelid jerks with upward eye deviation, typically provoked
      by eye closure in bright light. The defining seizure type of Jeavons
      syndrome, included here because eye-closure sensitivity is itself part
      of the photosensitivity trait spectrum this entry models.
    phenotype_term:
      preferred_term: Eyelid myoclonia seizure
      term:
        id: HP:0032678
        label: Eyelid myoclonia seizure
    frequency: VERY_FREQUENT
    evidence:
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Among epilepsy syndromes, there was over-representation of unique
          CHD2 variants (3/36 cases) in the archetypal photosensitive
          epilepsy syndrome, eyelid myoclonia with absences (P = 3.50 ×
          10(-4))
        explanation: >-
          Names eyelid myoclonia with absences as the archetypal
          photosensitive epilepsy syndrome, supporting a very frequent band
          for its defining seizure type within this subtype.
genetic:
  - name: CHD2
    gene_term:
      preferred_term: CHD2
      term:
        id: hgnc:1917
        label: CHD2
    relationship_type: RISK_FACTOR
    association: >-
      Unique (singleton) CHD2 variants are significantly over-represented in
      people with photosensitive epilepsies compared to population controls,
      and are the strongest single-gene contributor identified to date. CHD2
      encodes an ATP-dependent chromodomain-helicase-DNA-binding chromatin
      remodeler rather than an ion channel, which is notable because nearly
      every other established photosensitive/generalized epilepsy gene
      encodes a channel or a direct synaptic protein; how chromatin
      remodeling during neurodevelopment produces an acutely provokable
      cortical hyperexcitability is not established. Severe, fully
      penetrant loss-of-function CHD2 variants instead cause a distinct,
      separately curated developmental and epileptic encephalopathy
      (kb/disorders/CHD2-Related_Developmental_and_Epileptic_Encephalopathy.yaml);
      the risk-factor association modeled here is the milder, incompletely
      penetrant end of the same gene's phenotypic spectrum, seen in people
      whose epilepsy is not a fully expressed encephalopathy.
    case_fractions:
      - population: >-
          580 individuals with photosensitive seizures and/or abnormal
          photoparoxysmal response (EuroEPINOMICS CoGIE consortium)
        case_fraction_percent: 1.9
        cohort_size: 580
        notes: >-
          11 of 580 individuals carried a unique CHD2 variant (11/580 ≈
          1.9%), a statistically significant excess over the 128/34427 rate
          in unselected population controls (P = 2.17 x 10^-5), but still a
          minority of cases overall.
        evidence:
          - reference: PMID:25783594
            reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: >-
              We identified 11 unique variants in the 580 individuals with
              photosensitive epilepsies and 128 unique variants in the 34
              427 controls: unique CHD2 variation is over-represented in
              cases overall (P = 2.17 × 10(-5)).
            explanation: >-
              Source of the case count and control comparison used to derive
              the case fraction.
      - population: Eyelid myoclonia with absences (Jeavons syndrome) subgroup, n=36
        case_fraction_percent: 8.3
        cohort_size: 36
        notes: 3 of 36 Jeavons syndrome cases carried a unique CHD2 variant.
        evidence:
          - reference: PMID:25783594
            reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: >-
              there was over-representation of unique CHD2 variants (3/36
              cases) in the archetypal photosensitive epilepsy syndrome,
              eyelid myoclonia with absences (P = 3.50 × 10(-4))
            explanation: >-
              Source of the syndrome-specific case count showing a higher
              CHD2 yield within Jeavons syndrome than in the mixed
              photosensitive-epilepsy cohort overall.
    evidence:
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Chd2 knockdown markedly enhanced mild innate zebrafish larval
          photosensitivity.
        explanation: >-
          Zebrafish chd2 knockdown causally enhances photosensitivity in
          vivo, supporting a functional, not merely statistical, role for
          CHD2 loss in the photosensitivity trait.
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          CHD2 does not encode an ion channel, opening new avenues for
          research into human cortical excitability.
        explanation: >-
          The authors' own framing of CHD2 as mechanistically distinct from
          the channelopathies that dominate epilepsy genetics, which is the
          basis for treating the CHD2-to-hyperexcitability link as an open
          mechanistic question rather than an established pathway.
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          CHD2 variation was not over-represented in photoparoxysmal response
          without seizures.
        explanation: >-
          Sharpens the scope of the CHD2 association: it holds for
          photosensitive epilepsy (seizures, or an abnormal photoparoxysmal
          response occurring alongside a seizure disorder) but not for the
          photoparoxysmal response occurring alone with no seizures, the same
          trait-versus-epilepsy boundary this entry draws elsewhere. Graded
          PARTIAL because it is a negative result narrowing where the
          positive association applies, not new support for the RISK_FACTOR
          claim itself.
environmental:
  - name: Intermittent Photic Stimulation and Structured Visual Patterns
    description: >-
      Flickering light (natural, such as sunlight through trees or on water,
      or artificial, such as strobe lighting, television, and video games) and
      structured high-contrast patterns are the reproducible triggers that
      define this entry. MONDO's own logical definition of photosensitive
      epilepsy binds the visible-light exposure directly to the disease
      concept, which this environmental entry mirrors with a pathograph link
      rather than only a textual description.
    exposure_term:
      preferred_term: exposure to visible light radiation
      term:
        id: ECTO:0000007
        label: exposure to visible light radiation
    evidence:
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Photosensitivity is a heritable abnormal cortical response to
          flickering light, manifesting as particular electroencephalographic
          changes, with or without seizures.
        explanation: >-
          Establishes flickering light exposure as the trigger of the
          abnormal cortical response that defines photosensitivity, the
          general claim this environmental entry as a whole makes.
    influences_mechanisms:
      - target: Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation
        environmental_effect: TRIGGERS
        causal_link_type: DIRECT
        description: >-
          Delivery of intermittent photic stimulation, at an individually
          variable flicker-frequency range, is the direct proximate trigger
          of the abnormal cortical response that this entry's pathophysiology
          chain begins with; it is also the basis of the standard diagnostic
          EEG provocation procedure.
        evidence:
          - reference: PMID:31526678
            reference_title: >-
              Photosensitive epilepsy and photosensitivity of patients with
              possible epilepsy in Chinese Han race: A prospective multicenter
              study.
            supports: SUPPORT
            evidence_source: HUMAN_CLINICAL
            snippet: >-
              69.9% patients were evoked by frequency ranged 8 Hz-25 Hz, with
              accompanying seizures in 13 patients.
            explanation: >-
              Quantifies the flicker-frequency range that triggers the
              cortical response in a large prospective cohort, directly
              supporting the TRIGGERS relationship asserted here.
    notes: >-
      Structured, high-contrast patterns (stripes, checkerboards) are a
      related and well-documented trigger, sometimes acting even under
      constant illumination without flicker, but ECTO was searched and has no
      dedicated exposure term for pattern stimulation distinct from visible
      light exposure in general; binding one here would misrepresent what
      ECTO:0000007 actually covers, so pattern sensitivity is described in
      prose only rather than given its own exposure_term.
epidemiology:
  - name: Proportion of Pediatric Epilepsy Referrals with Photosensitive Epilepsy
    description: >-
      In a single-center Chinese pediatric epilepsy service that screened 398
      consecutively diagnosed children with video-EEG and intermittent photic
      stimulation testing, photosensitive epilepsy was found in 31. This is a
      proportion within an epilepsy-referral cohort ascertained by a specific
      IPS protocol, not a general-population prevalence estimate.
    unit: proportion of a single-center pediatric epilepsy referral cohort
    evidence:
      - reference: PMID:36969295
        reference_title: >-
          Electroclinical characteristics of photosensitive epilepsy: A
          retrospective study of 31 Chinese children and literature review.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          PSE accounted for 7.79% (31/398) of children with epilepsy during
          the observation period in our single epilepsy center.
        explanation: >-
          Direct quantification of the fraction of children with epilepsy who
          were found to have photosensitive epilepsy in this ascertainment
          protocol. Retrieved directly from the article's PMID-keyed full
          text (the earlier DOI-keyed cache entry for the same article was
          abstract-only; this PMID-keyed fetch resolved the full text).
  - name: Onset Age and Sex Ratio in a Pediatric Photosensitive Epilepsy Cohort
    description: >-
      In the same 31-patient Chinese pediatric cohort, seizure onset was in
      early childhood on average, and photosensitive epilepsy was markedly
      more common in girls than boys, a sex skew paralleled elsewhere in the
      photosensitivity literature (see the treatments section for a sex
      difference in valproate pharmacodynamic response).
    unit: years (onset age); ratio (sex)
    mean_range: "7.8 +/- 3.28 years onset; male:female 1:3.43"
    evidence:
      - reference: PMID:36969295
        reference_title: >-
          Electroclinical characteristics of photosensitive epilepsy: A
          retrospective study of 31 Chinese children and literature review.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Among them, there were 7 males and 24 females; the male to female
          ratio was 1:3.43.
        explanation: >-
          Direct report of the sex ratio in this pediatric photosensitive
          epilepsy cohort. Retrieved directly from the article's PMID-keyed
          full text (the earlier DOI-keyed cache entry for the same article
          was abstract-only; this PMID-keyed fetch resolved the full text).
      - reference: PMID:36969295
        reference_title: >-
          Electroclinical characteristics of photosensitive epilepsy: A
          retrospective study of 31 Chinese children and literature review.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          The highest age of incidence ranged from 6 to 11 years with a
          proportion of 70.96% (22/31, 2 males and 10 females).
        explanation: >-
          Reports the peak incidence age range in this cohort. The source
          itself is internally inconsistent here: it states "22/31" for the
          peak-age-band proportion but then gives a male/female breakdown
          (2 and 10) that sums to 12, not 22. This is flagged as a
          discrepancy in the cited source rather than silently resolved in
          either direction; the female-skew qualitative pattern (2 males
          versus 10 females in whichever subgroup the breakdown actually
          describes) is consistent with the sex ratio reported elsewhere in
          this cohort regardless of which figure is correct.
  - name: Age at Onset of the Photosensitivity Trait
    description: >-
      Independent of any one syndrome's seizure-onset age, the underlying
      photosensitivity trait itself (the abnormal photoparoxysmal EEG
      response) most often first appears in childhood or adolescence, with a
      peak age at onset around 12 years and onset before age 20 in the great
      majority of cases. This is a broader, syndrome-agnostic estimate,
      distinct from the syndrome-specific seizure-onset age reported in the
      Chinese pediatric cohort above.
    unit: years
    evidence:
      - reference: PMID:23274161
        reference_title: >-
          Photosensitivity: epidemiology, genetics, clinical manifestations,
          assessment, and management.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Photosensitivity usually begins before the age of 20 years with a
          peak age at onset at around 12.
        explanation: >-
          States the typical age-of-onset window and peak for the
          photosensitivity trait itself. Evidence source is OTHER because
          this is a review article.
  - name: Visual Sensitivity Prevalence Varies by Underlying Epilepsy Syndrome
    description: >-
      The proportion of epilepsy patients who show visual sensitivity is
      highly syndrome-dependent rather than a single fixed rate, consistent
      with this entry's framing of photosensitivity as a trait riding along
      with different underlying epilepsy syndromes at markedly different
      rates (from a minority in some syndromes up to the great majority in
      others, such as juvenile myoclonic epilepsy).
    unit: percent of patients, syndrome-dependent
    evidence:
      - reference: DOI:10.5772/intechopen.1015299
        reference_title: How and When to Treat Visually-Evoked Seizures
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Depending on the type of epilepsy, visual sensitivity can occur in
          up to 40% of patients, but this is often not diagnosed or treated.
        explanation: >-
          States the syndrome-dependent range and the practical caveat that
          visual sensitivity is frequently underdiagnosed even when present.
          Evidence source is OTHER because this is a book chapter overview,
          not a primary study.
animal_models:
  - name: Papio papio photosensitive baboon
    species: Papio papio (baboon)
    genotype: >-
      Naturally occurring, heritable generalized photosensitivity trait; no
      causal mutation has yet been identified.
    publication: PMID:26875109
    description: >-
      The classic naturally occurring primate model of generalized
      photosensitive epilepsy: colonies of Papio papio baboons show a
      heritable predisposition to generalized epileptiform discharges and
      motor seizures on intermittent photic stimulation, closely paralleling
      the human photoparoxysmal response, and have been used for decades to
      study visual-network propagation and antiseizure pharmacology.
    modeled_mechanisms:
      - target: Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation
        relationship: RECAPITULATES
        fidelity: MODERATE
        description: >-
          Reproduces the core trait this entry's pathophysiology chain begins
          with -- a heritable cortical hyperexcitability to flickering light
          -- in a species phylogenetically closer to humans than the rodent
          and avian models available for this trait.
        limitations: >-
          No causal genetic lesion has been identified in Papio papio despite
          a presumed genetic etiology, so the model cannot yet be used to test
          any specific human candidate variant (including CHD2), and primate
          colony availability sharply limits its use relative to zebrafish or
          mouse models.
        evidence:
          - reference: PMID:26875109
            reference_title: Genetics of reflex seizures and epilepsies in humans and animals.
            supports: SUPPORT
            evidence_source: OTHER
            snippet: >-
              No specific mutation has been found in Papio papio baboon,
              although a genetic etiology is likely.
            explanation: >-
              Establishes Papio papio as a naturally occurring
              photosensitive-epilepsy model with a presumed but still
              unidentified genetic basis, the basis for both the
              RECAPITULATES relationship and its stated limitation. Evidence
              source is OTHER because this is a narrative review, not a
              primary study of the baboon colony itself.
        readouts:
          - name: Ictal and Interictal Epileptiform EEG Discharges During Intermittent Light Stimulation
            target: Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation
            interpretation: >-
              The electrographic readout by which photosensitive, epileptic
              (PS) baboon colonies are distinguished from asymptomatic
              control (CTL) animals: ictal and interictal epileptiform EEG
              discharges occurring during intermittent light stimulation.
              Renamed from an earlier, more specific "motor seizure response"
              framing after the cited source was found to establish the
              electrographic discharge readout directly but not a separately
              quantified motor-seizure measurement.
            evidence:
              - reference: PMID:22276085
                reference_title: Functional PET Evaluation of the Photosensitive Baboon.
                supports: SUPPORT
                evidence_source: MODEL_ORGANISM
                snippet: >-
                  our group utilized functional positron emission tomography
                  (PET) to compare cerebral blood flow (CBF) changes
                  occurring during intermittent light stimulation (ILS) and
                  rest between baboons photosensitive, epileptic (PS) and
                  asymptomatic, control (CTL) animals.
                explanation: >-
                  Establishes the intermittent light stimulation (ILS)
                  paradigm and the photosensitive-epileptic (PS) versus
                  asymptomatic-control (CTL) baboon classification this
                  readout depends on.
              - reference: PMID:22276085
                reference_title: Functional PET Evaluation of the Photosensitive Baboon.
                supports: SUPPORT
                evidence_source: MODEL_ORGANISM
                snippet: >-
                  CBF changes in the subtraction and covariance analyses
                  reveal the physiological response and visual connectivity
                  in CTL animals and pathophysiological networks underlying
                  responses associated with the activation of ictal and
                  interictal epileptic discharges in PS animals.
                explanation: >-
                  Directly reports the ictal and interictal epileptiform EEG
                  discharges that distinguish photosensitive from control
                  baboons, the specific measurement this readout attests.
    evidence:
      - reference: PMID:22276085
        reference_title: Functional PET Evaluation of the Photosensitive Baboon.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          our group utilized functional positron emission tomography (PET) to
          compare cerebral blood flow (CBF) changes occurring during
          intermittent light stimulation (ILS) and rest between baboons
          photosensitive, epileptic (PS) and asymptomatic, control (CTL)
          animals.
        explanation: >-
          Establishes the photosensitive baboon as a naturally occurring
          model in which intermittent light stimulation reproducibly
          distinguishes a photosensitive-epileptic phenotype from
          asymptomatic controls, the basis for the RECAPITULATES
          relationship.
      - reference: PMID:26875109
        reference_title: Genetics of reflex seizures and epilepsies in humans and animals.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          No specific mutation has been found in Papio papio baboon, although
          a genetic etiology is likely.
        explanation: >-
          Supports Papio papio as an informative naturally occurring model for
          the visual cortical hyperexcitability node. Evidence source is
          OTHER because this is a narrative review, not a primary study of the
          baboon colony itself.
  - name: Fepi (Fayoumi) photosensitive chicken line
    species: Gallus gallus (Fayoumi-derived Fepi chicken strain)
    genotype: >-
      Recessive autosomal mutation in the acceptor site of SV2A intron 2
      (synaptic vesicle glycoprotein 2A, the levetiracetam binding target),
      homozygous
    publication: PMID:22046416
    description: >-
      A heritable avian model of photic and audiogenic reflex epilepsy in
      which a splice-site mutation in SV2A produces spontaneous, photically
      triggered seizures, providing a genetically defined counterpoint to the
      still-genetically-unresolved Papio papio model. Brain-chimera transfer
      experiments in this same strain, however, localize its seizure
      generator to the brain stem rather than to visual cortex, which is why
      this model is scored FAILS_TO_RECAPITULATE below rather than
      PARTIALLY_RECAPITULATES.
    modeled_mechanisms:
      - target: Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation
        relationship: FAILS_TO_RECAPITULATE
        fidelity: LOW
        description: >-
          Reproduces heritable photic (and audiogenic) seizure susceptibility
          linked to a defined synaptic gene, but living neural-chimera
          experiments in this strain -- replacing specific embryonic brain
          vesicles with their Fepi-donor equivalents -- localize the seizure
          generator to the brain stem (prosencephalon and mesencephalon), not
          to the visual cortex this entry's pathophysiology chain describes.
        limitations: >-
          The original authors' own conclusion places the Fepi seizure
          generator in the brain stem: substituting only the mesencephalon
          transfers the motor seizure, substituting only the prosencephalon
          transfers interictal paroxysmal activity, and total transfer
          requires substituting both. This is a fundamentally different
          anatomical locus from the visual-cortex and thalamocortical
          mechanism this entry establishes for human photosensitive epilepsy
          (see the Reduced Alpha-Rhythm Network Inhibition and Visual
          Cortical Hyperexcitability nodes above), not merely a difference of
          degree from avian brain architecture. It is recorded here as a
          documented negative result rather than omitted, so a future curator
          does not re-propose the Fepi line as a cortical model of human
          photosensitive epilepsy. SV2A is also not among the genes
          implicated in human photosensitive epilepsy -- CHD2, the
          best-established human risk gene curated in this entry, is
          unrelated to SV2A.
        evidence:
          - reference: PMID:15260383
            reference_title: An avian model of genetic reflex epilepsy.
            supports: SUPPORT
            evidence_source: MODEL_ORGANISM
            snippet: >-
              We conclude that the Fepi is a good model of brain stem reflex
              epilepsy and suggest that the brain stem is a generator of some
              other animal and human genetic reflex "epileptic syndromes".
            explanation: >-
              The original authors' own conclusion, directly supporting the
              FAILS_TO_RECAPITULATE relationship: the Fepi model's own
              investigators locate its generator in the brain stem, not the
              visual cortex.
    evidence:
      - reference: PMID:22046416
        reference_title: >-
          Epilepsy caused by an abnormal alternative splicing with dosage
          effect of the SV2A gene in a chicken model.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          we report that a mutation in the acceptor site of the second intron
          of SV2A (the gene encoding synaptic vesicle glycoprotein 2A) is
          causing photosensitive reflex epilepsy in a unique vertebrate
          model, the Fepi chicken strain, a spontaneous model where the
          neurological disorder is inherited as an autosomal recessive
          mutation.
        explanation: >-
          The primary genetic study identifying the causal SV2A splice-site
          mutation in the Fepi chicken strain, replacing the earlier,
          secondary-review-only sourcing for this model with the original
          report.
      - reference: PMID:15260383
        reference_title: An avian model of genetic reflex epilepsy.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          The Fayoumi strain of chickens (Fepi) carries a recessive autosomal
          gene mutation in which homozygotes are afflicted with a photogenic
          and audiogenic reflex epilepsy.
        explanation: >-
          The classic description of the Fepi strain as a photogenic (and
          audiogenic) reflex epilepsy model, cited alongside the later SV2A
          gene-identification study above.
      - reference: PMID:26875109
        reference_title: Genetics of reflex seizures and epilepsies in humans and animals.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Mutation in synaptic vesicle glycoprotein 2A was found in another
          animal model of photosensitivity (Fayoumi chickens).
        explanation: >-
          Supports the Fayoumi chicken line as a genetically defined
          photosensitivity model. Evidence source is OTHER because this is a
          narrative review, not a primary study of the chicken line itself.
diagnosis:
  - name: Electroencephalography with Intermittent Photic Stimulation
    description: >-
      The core diagnostic investigation, and a deliberately provocative one:
      a standardized flash sequence across a range of frequencies is
      delivered during EEG recording specifically to elicit the
      photoparoxysmal response, with and without eye closure, since eye
      closure itself can gate the response.
    diagnosis_term:
      preferred_term: Electroencephalography
      term:
        id: NCIT:C38054
        label: Electroencephalography
    evidence:
      - reference: PMID:31526678
        reference_title: >-
          Photosensitive epilepsy and photosensitivity of patients with
          possible epilepsy in Chinese Han race: A prospective multicenter
          study.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          6 of 9 patients with eyes closure sensitivity experienced epileptic
          seizures during IPS.
        explanation: >-
          Documents eye closure as a specific, separately assessed component
          of the standard intermittent photic stimulation protocol.
  - name: Virtual Reality and Machine Learning-Assisted Photoparoxysmal Response Detection
    description: >-
      An emerging research technique, not yet clinical standard of care, that
      adds a programmable virtual reality stimulation platform and AI-based
      automatic EEG scoring on top of the conventional IPS-EEG procedure,
      aiming to broaden and standardize the range of visual stimuli that can
      be tested for a photoparoxysmal response beyond the fixed manual flash
      protocol.
    diagnosis_term:
      preferred_term: Electroencephalography
      term:
        id: NCIT:C38054
        label: Electroencephalography
    evidence:
      - reference: DOI:10.1007/s00521-022-06940-z
        reference_title: >-
          Virtual reality and machine learning in the automatic
          photoparoxysmal response detection
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          This research focuses on introducing virtual reality (VR) in this
          context, adding, to the conventional infrastructure a more flexible
          one that can be programmed and that will allow developing a much
          wider and richer set of experiments in order to detect neurological
          illnesses, and to study subjects’ behaviours automatically.
        explanation: >-
          Describes the VR/AI-augmented IPS-EEG research platform this
          diagnosis entry models, distinct from and supplementary to the
          standard manual IPS-EEG protocol described above. Evidence source
          is OTHER because the paper's contribution is a detection system and
          methods description, not a report of patient clinical outcomes.
treatments:
  - name: Antiseizure Pharmacotherapy
    description: >-
      Valproate is the conventional first-line agent for photosensitive
      epilepsy and reliably suppresses the photoparoxysmal response;
      levetiracetam is a common alternative, particularly favored in girls
      and young women given valproate's teratogenicity and other
      reproductive-health concerns. A separate, purely pharmacodynamic sex
      difference has also been reported: in a within-patient retrospective
      cohort, males showed a significantly greater reduction in the
      standardized photosensitivity range on valproate than females, a
      finding distinct from (and not explained by) the prescribing pattern
      driven by teratogenicity risk.
    therapeutic_modality: SMALL_MOLECULE
    treatment_term:
      preferred_term: Pharmacotherapy
      term:
        id: NCIT:C15986
        label: Pharmacotherapy
      therapeutic_agent:
        - preferred_term: valproic acid
          term:
            id: CHEBI:39867
            label: valproic acid
        - preferred_term: levetiracetam
          term:
            id: CHEBI:6437
            label: levetiracetam
    target_mechanisms:
      - target: Visual-to-Motor Cortical Hyperexcitable Spread
        treatment_effect: INHIBITS
    evidence:
      - reference: PMID:40580381
        reference_title: >-
          Evidence of Sex-Related Pharmacodynamic Differences in
          Photosensitive Epilepsy Treated with Valproate: Findings from a
          Retrospective, Observational, Single-Center, Within-Patient,
          Cohort Study.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          It is well established that VPA reduces or suppresses PPR, as
          first shown after single oral doses in seven out of nine
          photosensitive patients
        explanation: >-
          States directly that valproate reduces or suppresses the
          photoparoxysmal response, the basis for describing it as the
          conventional first-line agent for photosensitive epilepsy.
      - reference: PMID:40580381
        reference_title: >-
          Evidence of Sex-Related Pharmacodynamic Differences in
          Photosensitive Epilepsy Treated with Valproate: Findings from a
          Retrospective, Observational, Single-Center, Within-Patient,
          Cohort Study.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Males experienced a significantly greater reduction in SPR compared
          with females. The mean decrease in SPR was -7.0 ± 2.6 in males only
          versus -3.9 ± 3.3 in females only (p = 0.0018).
        explanation: >-
          The study's own headline pharmacodynamic finding, quantifying the
          sex difference in valproate response referenced in the description
          above: a within-patient comparison of standardized photosensitivity
          range change before and after valproate, showing a significantly
          larger reduction in males.
  - name: Cenobamate
    description: >-
      In a phase 2 proof-of-principle study, a single oral dose of cenobamate
      (then YKP3089) produced dose-dependent suppression of the
      photoparoxysmal response in photosensitive epilepsy patients,
      establishing acute PPR suppression for a drug whose broader mechanism
      combines sodium-channel inactivation with GABA-A receptor positive
      allosteric modulation. It is an approved antiseizure medication used
      more broadly for focal-onset seizures; this entry documents its
      acute-suppression evidence specifically in the photosensitivity model,
      not a long-term PSE effectiveness trial.
    therapeutic_modality: SMALL_MOLECULE
    treatment_term:
      preferred_term: Pharmacotherapy
      term:
        id: NCIT:C15986
        label: Pharmacotherapy
      therapeutic_agent:
        - preferred_term: cenobamate
          term:
            id: CHEBI:234112
            label: Cenobamate
    target_mechanisms:
      - target: Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation
        treatment_effect: INHIBITS
    evidence:
      - reference: PMID:31292226
        reference_title: >-
          Suppression of the photoparoxysmal response in photosensitive
          epilepsy with cenobamate (YKP3089).
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Cenobamate 100 mg produced partial suppression in 1 of 3 patients;
          250 mg produced complete suppression in 1 of 4 and partial
          suppression in 4 of 4 patients; and 400 mg produced complete
          suppression in 1 of 4 and partial suppression in 2 of 4 patients.
        explanation: >-
          The dose-by-dose suppression results directly supporting the
          INHIBITS relationship asserted on this treatment. Retrieved
          directly from the article's PMID-keyed abstract (the earlier
          DOI-keyed cache entry for the same article lacked full text; this
          PMID-keyed fetch resolved it).
      - reference: PMID:31292226
        reference_title: >-
          Suppression of the photoparoxysmal response in photosensitive
          epilepsy with cenobamate (YKP3089).
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          CONCLUSIONS: This proof-of-principle study demonstrated that
          cenobamate is a potentially effective product for epilepsy.
        explanation: >-
          The authors' own conclusion, establishing acute PPR suppression as
          proof-of-principle evidence for cenobamate in photosensitive
          epilepsy.
      - reference: clinicaltrials:NCT00616148
        reference_title: "Pharmacodynamic Evaluation of YKP3089 in Epilepsy Patients With a Photo-induced Paroxysmal EEG-Response: Proof of Principle"
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The aim of this study is to evaluate the ability of a single oral
          dose of YKP3089 to abolish or clearly reduce the IPS-induced
          photo-paroxysmal EEG response in photosensitive epilepsy patients,
          and to measure the onset and duration of the effect.
        explanation: >-
          ClinicalTrials.gov registration record for the proof-of-principle
          cenobamate (YKP3089) trial whose published results are cited above.
          Evidence source is OTHER because this is a registration summary,
          not study results.
  - name: Investigational GABAergic Positive Allosteric Modulation
    description: >-
      PF-06372865, an alpha2/3/5-subunit-selective GABA-A receptor positive
      allosteric modulator designed to avoid the alpha1-mediated sedative and
      dependence liabilities of benzodiazepines, produced a marked and
      statistically significant suppression of the photoparoxysmal response
      in a phase 2a proof-of-principle study, comparable in magnitude to
      lorazepam. This is investigational rather than an approved therapy, but
      is included because the human photosensitivity model is being used
      directly as a translational efficacy readout for this drug class.
    therapeutic_modality: SMALL_MOLECULE
    treatment_term:
      preferred_term: Pharmacotherapy
      term:
        id: NCIT:C15986
        label: Pharmacotherapy
    target_mechanisms:
      - target: Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation
        treatment_effect: INHIBITS
    evidence:
      - reference: PMID:30877186
        reference_title: >-
          Photosensitive epilepsy: Robust clinical efficacy of a selective
          GABA potentiator.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Both doses of PF-06372865 produced a marked and statistically
          significant mean reduction in SPR compared to placebo, which was
          similar in degree to lorazepam.
        explanation: >-
          The primary efficacy result supporting the INHIBITS relationship
          asserted on this treatment.
      - reference: PMID:30877186
        reference_title: >-
          Photosensitive epilepsy: Robust clinical efficacy of a selective
          GABA potentiator.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          There was complete suppression of SPR in 6/7 participants following
          PF-06372865 or lorazepam administration.
        explanation: >-
          Quantifies the magnitude of response suppression achieved.
  - name: Trigger Avoidance and Environmental Modification
    description: >-
      Because seizures are elicited rather than spontaneous in the reflex
      component this entry models, reducing exposure (distance from screens,
      avoiding untreated strobe environments, monocular viewing, and
      polarized or colored lenses that reduce the effective flicker or
      contrast reaching the retina) is genuinely therapeutic rather than
      merely precautionary, and is standard advice alongside medication.
    therapeutic_modality: BEHAVIORAL
    treatment_term:
      preferred_term: Lifestyle Therapy
      term:
        id: NCIT:C15900
        label: Lifestyle Therapy
    target_mechanisms:
      - target: Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation
        treatment_effect: INHIBITS
    evidence:
      - reference: PMID:34221545
        reference_title: Reflex Epilepsy.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Treatment includes antiseizure medication, commonly valproate or
          levetiracetam, along with lifestyle modifications, and when
          amenable, surgical intervention.
        explanation: >-
          Places lifestyle modification alongside pharmacotherapy as a
          standard component of treatment for reflex epilepsies, the category
          photosensitive epilepsy belongs to. Evidence source is OTHER
          because this is a narrative review, not a primary cohort or case
          study.
clinical_trials:
  - name: NCT02564029
    phase: PHASE_II
    status: COMPLETED
    description: >-
      Phase 2a proof-of-principle crossover trial of PF-06372865, an
      alpha2/3/5-subunit-selective GABA-A receptor positive allosteric
      modulator, against lorazepam and placebo in patients with a stable
      photoparoxysmal response to intermittent photic stimulation. Published
      results are the basis for this entry's "Investigational GABAergic
      Positive Allosteric Modulation" treatment.
    target_phenotypes:
      - preferred_term: EEG with photoparoxysmal response
        term:
          id: HP:0010852
          label: EEG with photoparoxysmal response
    evidence:
      - reference: PMID:30877186
        reference_title: >-
          Photosensitive epilepsy: Robust clinical efficacy of a selective
          GABA potentiator.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          Both doses of PF-06372865 produced a marked and statistically
          significant mean reduction in SPR compared to placebo, which was
          similar in degree to lorazepam.
        explanation: >-
          Primary published efficacy result of this trial, already cited in
          the treatments section for the same drug.
      - reference: clinicaltrials:NCT02564029
        reference_title: "A Double Blind, Randomized, Cross- Over Study Examining Efficacy Of Pf-06372865 In A Photosensitivity Epilepsy Study Using Lorazepam As A Positive Control"
        supports: SUPPORT
        evidence_source: OTHER
        snippet: "PF-06372865 in subjects with photosensitive epilepsy"
        explanation: >-
          ClinicalTrials.gov registration record establishing the trial's
          identity. Evidence source is OTHER because this is a registration
          summary, not study results.
  - name: NCT00616148
    phase: PHASE_II
    status: COMPLETED
    description: >-
      Phase 2 proof-of-principle trial of a single oral dose of cenobamate
      (YKP3089) evaluating its ability to abolish or reduce the IPS-induced
      photoparoxysmal EEG response. Published results are the basis for this
      entry's cenobamate treatment.
    target_phenotypes:
      - preferred_term: EEG with photoparoxysmal response
        term:
          id: HP:0010852
          label: EEG with photoparoxysmal response
    evidence:
      - reference: PMID:31292226
        reference_title: >-
          Suppression of the photoparoxysmal response in photosensitive
          epilepsy with cenobamate (YKP3089).
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          CLASSIFICATION OF EVIDENCE: This study provides Class III evidence
          that, for patients with photosensitive epilepsy, cenobamate
          suppresses IPS-induced PPR.
        explanation: >-
          The published paper's own evidence classification for the
          NCT00616148 trial, confirming both this clinical_trials entry and
          the publication record for the same study. Retrieved directly from
          the article's PMID-keyed abstract (the earlier DOI-keyed cache
          entry for the same article lacked full text; this PMID-keyed fetch
          resolved it).
      - reference: clinicaltrials:NCT00616148
        reference_title: "Pharmacodynamic Evaluation of YKP3089 in Epilepsy Patients With a Photo-induced Paroxysmal EEG-Response: Proof of Principle"
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The aim of this study is to evaluate the ability of a single oral
          dose of YKP3089 to abolish or clearly reduce the IPS-induced
          photo-paroxysmal EEG response in photosensitive epilepsy patients,
          and to measure the onset and duration of the effect.
        explanation: >-
          ClinicalTrials.gov registration record establishing the trial's
          identity and design. Evidence source is OTHER because this is a
          registration summary, not study results.
  - name: NCT00609245
    phase: PHASE_IV
    status: COMPLETED
    description: >-
      Phase 4 trial examining whether small intravenous changes in plasma
      valproic acid concentration alter the photoparoxysmal EEG response,
      probing the pharmacodynamic dose-response relationship of valproate,
      this entry's first-line agent, at the level of the EEG biomarker
      itself.
    target_phenotypes:
      - preferred_term: EEG with photoparoxysmal response
        term:
          id: HP:0010852
          label: EEG with photoparoxysmal response
    evidence:
      - reference: clinicaltrials:NCT00609245
        reference_title: "Effect of Small Changes in Plasma Valproic Acid Concentration on the Photoparoxysmal Response"
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          We are trying to learn if small changes in the amount of a
          valproate in the blood (given through an IV) will change the way
          the brain reacts to flashing lights.
        explanation: >-
          ClinicalTrials.gov registration record establishing the trial's
          identity and design. Evidence source is OTHER because this is a
          registration summary, not study results.
  - name: NCT00401648
    phase: PHASE_II
    status: COMPLETED
    description: >-
      Placebo-controlled, single-blind, multi-center trial of a single oral
      dose of brivaracetam, exploring its effect on the photoparoxysmal EEG
      response in photosensitive epileptic subjects.
    target_phenotypes:
      - preferred_term: EEG with photoparoxysmal response
        term:
          id: HP:0010852
          label: EEG with photoparoxysmal response
    evidence:
      - reference: clinicaltrials:NCT00401648
        reference_title: "A Placebo-controlled, Single-blind, Multi-center Study to Explore the Photoparoxysmal Response in Photosensitive Epileptic Subjects After One Single Oral Dose of Brivaracetam in Capsules."
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          to assess the effect of brivaracetam on the photoparoxysmal EEG
          response in photosensitive epileptic subjects
        explanation: >-
          ClinicalTrials.gov registration record establishing the trial's
          identity and design. Evidence source is OTHER because this is a
          registration summary, not study results.
  - name: NCT00784212
    phase: PHASE_II
    status: COMPLETED
    description: >-
      Multicenter, single-blind, placebo-controlled proof-of-concept trial of
      single oral doses of the AMPA/kainate receptor antagonist BGG492
      (selurampanel), assessed by its effect on the photoparoxysmal EEG
      response.
    target_phenotypes:
      - preferred_term: EEG with photoparoxysmal response
        term:
          id: HP:0010852
          label: EEG with photoparoxysmal response
    evidence:
      - reference: clinicaltrials:NCT00784212
        reference_title: "A Multicenter, Single-blind, Within-subject, Placebo-controlled Proof of Concept Study to Assess the Effect of Single Oral Doses of BGG492 on the Photoparoxysmal EEG Response in Patients With Photosensitive Epilepsy"
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          This study will evaluate the efficacy of BGG492 in reducing the
          sensitivity to flashing lights of patients with photosensitive
          epilepsy, using EEG as a readout.
        explanation: >-
          ClinicalTrials.gov registration record establishing the trial's
          identity and design. Evidence source is OTHER because this is a
          registration summary, not study results.
  - name: NCT03686033
    phase: PHASE_II
    status: TERMINATED
    description: >-
      Multicenter, double-blind, randomized, crossover, single-dose trial
      assessing the pharmacodynamic activity of E2082, measured by
      suppression of the photoparoxysmal response, in adults with
      photosensitive epilepsy.
    target_phenotypes:
      - preferred_term: EEG with photoparoxysmal response
        term:
          id: HP:0010852
          label: EEG with photoparoxysmal response
    evidence:
      - reference: clinicaltrials:NCT03686033
        reference_title: "A Multicenter, Double-Blind, Randomized, Crossover, Single-Dose Study With An Open-Label Treatment Period Evaluating Pharmacodynamic Activity of E2082 in Adult Subjects With Photosensitive Epilepsy"
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The primary purpose of the study is to assess pharmacodynamic (PD)
          activity of E2082 as measured by suppression of epileptic
          photoparoxysmal response (PPR) in the participant's most sensitive
          eye condition in participants with photosensitive epilepsy,
          compared to placebo.
        explanation: >-
          ClinicalTrials.gov registration record establishing the trial's
          identity and design; the trial's status is TERMINATED per
          ClinicalTrials.gov. Evidence source is OTHER because this is a
          registration summary, not study results.
  - name: NCT05678881
    phase: PHASE_I
    status: TERMINATED
    description: >-
      Phase 1b randomized, double-blind, placebo-controlled crossover trial
      of inhaled dry powder cannabidiol (RLS103) evaluating safety and
      suppression of the epileptic photoparoxysmal response.
    target_phenotypes:
      - preferred_term: EEG with photoparoxysmal response
        term:
          id: HP:0010852
          label: EEG with photoparoxysmal response
    evidence:
      - reference: clinicaltrials:NCT05678881
        reference_title: "A Phase 1b Randomized, Double-Blind, Placebo Controlled, Crossover Study to Evaluate the Safety, Tolerability, and Efficacy of Two Doses of RLS103 (Inhaled Dry Powder Cannabidiol [CBD]) in a Clinical Model of Photosensitive Epilepsy"
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          The purpose of this study is to evaluate RLS103 for safety and
          suppression of the epileptic photoparoxysmal response compared to
          placebo.
        explanation: >-
          ClinicalTrials.gov registration record establishing the trial's
          identity and design; the trial's status is TERMINATED per
          ClinicalTrials.gov. Evidence source is OTHER because this is a
          registration summary, not study results.
  - name: NCT06525649
    phase: PHASE_I
    status: COMPLETED
    description: >-
      Double-blind, randomized, crossover trial examining suppression of the
      photoparoxysmal EEG response with two doses of NPT 2042 compared to
      placebo in approximately five adults with a known stable
      photoparoxysmal response.
    target_phenotypes:
      - preferred_term: EEG with photoparoxysmal response
        term:
          id: HP:0010852
          label: EEG with photoparoxysmal response
    evidence:
      - reference: clinicaltrials:NCT06525649
        reference_title: "A Double Blind, Randomized, Cross-over Study Examining the Suppression of the Photoparoxysmal EEG Response With NPT 2042"
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          A double-blind, placebo-controlled, crossover trial to investigate
          the PPR of approximately 5 subjects with a known stable PPR on EEG,
          using 2 doses of NPT 2042 compared to placebo.
        explanation: >-
          ClinicalTrials.gov registration record establishing the trial's
          identity and design. Evidence source is OTHER because this is a
          registration summary, not study results.
  - name: NCT04076410
    phase: NOT_APPLICABLE
    status: UNKNOWN
    description: >-
      Pediatric trial comparing four new spectral filter lenses to the
      existing Zeiss Clarlet Z1 lens for reducing the photoparoxysmal
      response, in patients 5-18 years old referred for EEG with IPS/pattern
      stimulation. This is the non-pharmacological, device-based counterpart
      to this entry's drug trials, testing the same
      trigger-avoidance/environmental-modification principle described in
      the treatments section. Registry status was last recorded as
      UNKNOWN by ClinicalTrials.gov.
    target_phenotypes:
      - preferred_term: EEG with photoparoxysmal response
        term:
          id: HP:0010852
          label: EEG with photoparoxysmal response
    evidence:
      - reference: clinicaltrials:NCT04076410
        reference_title: "Efficacy of New Lenses in Abolishing Photoparoxysmal Responses in Paediatric Patients With Photosensitive Epilepsy (PSE)"
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          To determine whether four new lenses with different spectral
          characteristics are not inferior in efficacy to Z1 to reduce the
          PPRs in patients with PSE.
        explanation: >-
          ClinicalTrials.gov registration record establishing the trial's
          identity and primary objective. Evidence source is OTHER because
          this is a registration summary, not study results.
differential_diagnoses:
  - name: Self-Induced (Sunflower) Photosensitive Epilepsy
    description: >-
      A behaviorally distinct entity in which the patient deliberately
      elicits the photoparoxysmal response by waving fingers in front of the
      eyes in bright light, rather than passively encountering an
      environmental trigger. Not modeled as a subtype here (see notes); no
      MONDO disease_term is bound in this differential-diagnosis block
      because it names a related concept (MONDO:0100529, Sunflower syndrome)
      that this entry does not itself curate.
    distinguishing_features:
      - The stimulus is self-generated by hand-waving rather than encountered environmentally.
      - Behavior is often compulsive and difficult to interrupt, with a described self-reinforcing quality.
    evidence:
      - reference: PMID:35807051
        reference_title: >-
          Photo-Dependent Reflex Seizures-A Scoping Review with Proposal of
          Classification.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Epilepsy with seizures provoked by intermittent light stimulation
          is a distinct group of epilepsies
        explanation: >-
          Supports treating photically provoked epilepsies as a distinct
          group within which self-induced forms are a recognized but
          behaviorally separate presentation. Evidence source is OTHER
          because this is a review article.
  - name: Fixation-Off Sensitivity Epilepsies
    description: >-
      Epilepsies, such as childhood occipital visual epilepsy, in which
      removing central visual fixation (eye closure in darkness, or
      convergence) rather than photic stimulation itself is the gating
      electrographic phenomenon. Distinguished by the opposite manipulation:
      photosensitive epilepsy's photoparoxysmal response requires a light
      stimulus, while fixation-off sensitivity requires the absence of
      structured foveal vision.
    distinguishing_features:
      - The gating manipulation is loss of central fixation, not delivery of a light or pattern stimulus.
      - Seizures occur spontaneously rather than being elicited by an external visual trigger.
    evidence:
      - reference: PMID:35503717
        reference_title: >-
          International League Against Epilepsy classification and
          definition of epilepsy syndromes with onset in childhood: Position
          paper by the ILAE Task Force on Nosology and Definitions.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Epilepsy syndromes beginning in childhood have been divided into
          three categories: (1) self-limited focal epilepsies, comprising
          four syndromes: self-limited epilepsy with centrotemporal spikes,
          self-limited epilepsy with autonomic seizures, childhood occipital
          visual epilepsy, and photosensitive occipital lobe epilepsy
        explanation: >-
          Lists childhood occipital visual epilepsy, the fixation-off
          sensitivity syndrome, alongside photosensitive occipital lobe
          epilepsy as a separate, nosologically distinct syndrome despite
          the clinical closeness POLE's own entry discusses in detail.
discussions:
  - discussion_id: pse_provoked_seizure_module_boundary
    kind: OPEN_QUESTION
    status: OPEN
    prompt: >-
      Should photosensitive epilepsy conform to the
      epilepsy_excitation_inhibition_imbalance module's terminal node,
      Recurrent Unprovoked Seizures, given that its defining feature is a
      reproducibly provoked seizure, and how should that boundary be recorded
      when a subtype (JME, Dravet, the PMEs) genuinely has both provoked and
      unprovoked seizures?
    attaches_to:
      - "pathophysiology#Recurrent Visually Provoked Seizures"
    rationale: >-
      This entry declares conformance to
      epilepsy_excitation_inhibition_imbalance at the Neuronal
      Hyperexcitability and Hypersynchrony node and stops there, for the same
      reason already recorded in
      kb/disorders/Photosensitive_Occipital_Lobe_Epilepsy.yaml: the module's
      terminal node is Recurrent Unprovoked Seizures, and reflex seizures are
      elicited by definition, so declaring conformance there would assert the
      negation of the defining property of the reflex component this entry
      models. The complication specific to this root entry, and not shared by
      POLE, is that most of its named subtypes (JME, Jeavons syndrome, Dravet
      syndrome, the PMEs) are not purely reflex: they also have genuinely
      spontaneous, unprovoked seizures, and those subtypes' own separately
      curated entries may correctly conform to the terminal node for that
      reason. This entry's photosensitivity-scoped pathophysiology chain
      should not be read as contradicting that; it describes only the reflex
      component common to the whole family, deliberately leaving the
      unprovoked-seizure question to each subtype's own full entry.
    proposed_experiments:
      - experiment_id: pse_module_node_audit
        name: Audit of reflex-epilepsy and mixed-trigger entries against the module terminal node
        description: >-
          Extending the audit already proposed in the
          Photosensitive_Occipital_Lobe_Epilepsy entry, specifically compare
          how the terminal node is (or is not) declared across purely reflex
          entries versus mixed entries like this one that have both a
          reflex-scoped root and unprovoked-seizure-capable subtypes.
        decision_criterion: >-
          If curators consistently split conformance the way this entry does
          (reflex root stops short, individual mixed subtype entries conform
          separately), that confirms the current approach as the intended
          pattern rather than an ad hoc choice, and the module documentation
          should say so explicitly.
    evidence:
      - reference: PMID:34221545
        reference_title: Reflex Epilepsy.
        supports: SUPPORT
        evidence_source: OTHER
        snippet: >-
          Reflex seizures (RS) are epileptic events that are objectively and
          consistently elicited in response to a specific afferent stimulus
          or by an activity of the patient.
        explanation: >-
          Establishes reflex seizures as provoked by definition, creating the
          conflict with the module's unprovoked terminal node that this
          discussion is about. Evidence source is OTHER because this is a
          narrative review, not a primary cohort or case study.
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          We studied 580 individuals with epilepsy and either photosensitive
          seizures or abnormal photoparoxysmal response on
          electroencephalography, or both, and 55 individuals with
          photoparoxysmal response but no seizures.
        explanation: >-
          Shows that the cohort used to establish the genetics of this trait
          was itself drawn from mixed generalized-epilepsy syndromes, not
          only pure reflex cases, which is the empirical basis for the
          complication this discussion raises about subtype entries having
          both provoked and unprovoked seizures.
  - discussion_id: chd2_chromatin_to_hyperexcitability_gap
    kind: KNOWLEDGE_GAP
    status: OPEN
    prompt: >-
      By what mechanism does CHD2, a chromatin remodeler with no known direct
      role in ion transport or synaptic transmission, produce an acutely
      provokable cortical hyperexcitability, and does that mechanism converge
      on the same excitation-inhibition imbalance this entry's
      pathophysiology chain describes for the channelopathy-driven
      photosensitive syndromes?
    attaches_to:
      - "genetic#CHD2"
      - "pathophysiology#Visual Cortical Hyperexcitability to Flickering Light and Pattern Stimulation"
    rationale: >-
      Every other well-established photosensitive or generalized epilepsy
      gene referenced across this entry's subtypes and elsewhere in the
      knowledge base encodes an ion channel or a direct synaptic protein,
      fitting naturally into the excitation-inhibition imbalance framework
      this entry conforms to. CHD2 is different by the original authors' own
      framing: it is a chromatin remodeler, and how altering chromatin state
      during neurodevelopment produces a cortex that overreacts to a stimulus
      delivered in real time, rather than a fixed developmental malformation,
      is not established. The zebrafish knockdown result shows the effect is
      causal, not merely correlational, but does not by itself identify the
      intermediate steps between chromatin remodeling and acute
      photic-response hyperexcitability, so this is recorded as a knowledge
      gap rather than folded into the pathophysiology chain as an established
      mechanism.
    proposed_experiments:
      - experiment_id: chd2_downstream_expression_profiling
        name: Transcriptomic profiling of visual-cortex neurons in a Chd2-deficient model
        description: >-
          Single-cell or bulk transcriptomic and chromatin-accessibility
          profiling of visual-cortex neurons in a Chd2-deficient animal
          model, testing whether loss of Chd2 dysregulates expression of
          ion-channel or synaptic genes already implicated in the
          excitation-inhibition imbalance module, which would identify a
          convergent downstream pathway.
        decision_criterion: >-
          Dysregulation of known excitability genes would support convergence
          on the module's existing framework; a distinct or absent
          transcriptional signature in relevant excitability genes would
          indicate CHD2 acts through a genuinely separate mechanism not yet
          captured by the module.
    evidence:
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: HUMAN_CLINICAL
        snippet: >-
          CHD2 does not encode an ion channel, opening new avenues for
          research into human cortical excitability.
        explanation: >-
          The authors' own statement of the mechanistic gap this discussion
          records.
      - reference: PMID:25783594
        reference_title: CHD2 variants are a risk factor for photosensitivity in epilepsy.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Chd2 knockdown markedly enhanced mild innate zebrafish larval
          photosensitivity.
        explanation: >-
          Establishes that the CHD2-photosensitivity link is causal in an
          animal model, which is why this is framed as an open question about
          intermediate mechanism rather than about whether an effect exists
          at all.

📚

References & Deep Research

References

8

PMID:35807051

Photo-Dependent Reflex Seizures-A Scoping Review with Proposal of Classification.

No top-level findings curated for this source.

PMID:10496248

Photosensitive epilepsies and pathophysiologic mechanisms of the photoparoxysmal response.

No top-level findings curated for this source.

PMID:25783594

CHD2 variants are a risk factor for photosensitivity in epilepsy.

No top-level findings curated for this source.

PMID:26395125

Overactive visuomotor connections underlie the photoparoxysmal response. A TMS study.

No top-level findings curated for this source.

PMID:31526678

Photosensitive epilepsy and photosensitivity of patients with possible epilepsy in Chinese Han race: A prospective multicenter study.

No top-level findings curated for this source.

PMID:30877186

Photosensitive epilepsy: Robust clinical efficacy of a selective GABA potentiator.

No top-level findings curated for this source.

PMID:34221545

Reflex Epilepsy.

No top-level findings curated for this source.

PMID:35503717

International League Against Epilepsy classification and definition of epilepsy syndromes with onset in childhood: Position paper by the ILAE Task Force on Nosology and Definitions.

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

Photosensitive Epilepsy: Disease Characteristics Research Report

Edison Scientific Literature 24 citations 2026-08-26T22:35:36.441752

Photosensitive Epilepsy: Disease Characteristics Research Report

Executive summary

Photosensitive epilepsy (PSE) is not one uniform monogenic disorder. It is a visually provoked reflex epilepsy phenotype that occurs most often within genetic generalized epilepsies, but also in focal occipital epilepsy and several developmental or progressive epilepsy syndromes. Its objective biomarker is a photoparoxysmal response (PPR)—occipital or generalized epileptiform activity induced by intermittent photic stimulation (IPS), pattern stimulation, or comparable real-world visual stimuli. A person may have pure PSE, with only visually provoked seizures, or epilepsy with photosensitivity, in which visually provoked and spontaneous seizures coexist. PPR without clinical epilepsy can also occur and should not by itself be equated with epilepsy. (brazzo2010mechanismsofaltered pages 12-17, verrotti2012photosensitivityepidemiologygenetics pages 1-2, vaudano2017photosensitiveepilepsyis pages 1-2)

Recent research has reinforced a network model: abnormal visual-cortical excitability combines with deficient alpha-mediated inhibition and altered occipital–frontoparietal–sensorimotor/thalamic connectivity. The strongest routinely applicable diagnostic and pharmacodynamic tool remains standardized IPS-EEG. Recent innovations include virtual-reality stimulation, machine-learning PPR detection, network EEG analysis, and continued use of PPR suppression as a small-sample proof-of-principle platform for antiseizure drugs. (trenite2019suppressionofthe pages 1-2, timar2024functionalnetworkdynamics pages 1-3, moncada2023virtualrealityand pages 1-2)

Domain	Evidence-backed finding	Suggested ontology terms/IDs	Evidence type/strength
Disease definition / PPR	Photosensitive epilepsy (PSE) is a reflex epilepsy/EEG trait in which flickering light or patterned visual stimuli provoke epileptiform activity; the EEG hallmark is the photoparoxysmal response (PPR), ranging from occipital to generalized spike-wave activity. Pure PSE (only visually induced seizures) should be distinguished from epilepsy with photosensitivity (spontaneous + visually provoked seizures). (brazzo2010mechanismsofaltered pages 12-17, verrotti2012photosensitivityepidemiologygenetics pages 1-2, vaudano2017photosensitiveepilepsyis pages 1-2)	MONDO:0015643 photosensitive epilepsy; MeSH: Epilepsy, Reflex; HPO: Photoparoxysmal response, Reflex seizure, Photosensitivity	Human clinical reviews + human EEG-fMRI background evidence; moderate-strong
Major phenotypes	Common seizure phenotypes include generalized tonic-clonic, myoclonic, absence, eyelid myoclonia, and less often focal occipital seizures; in a 2023 pediatric cohort, IPS induced electroclinical seizures in 41.94% and EEG-only discharge in 58.06%. (brazzo2010mechanismsofaltered pages 12-17, zhang2023electroclinicalcharacteristicsof pages 1-2, zhang2023electroclinicalcharacteristicsof pages 2-3)	HPO: Generalized tonic-clonic seizure; Myoclonic seizure; Absence seizure; Eyelid myoclonia; Occipital seizure	Human cohort + reviews; strong for seizure spectrum
Age / sex pattern	Onset is usually in childhood/adolescence, often around puberty, with female predominance; the Chinese pediatric cohort reported mean onset 7.8 ± 3.28 years and male:female ratio 1:3.43. (brazzo2010mechanismsofaltered pages 12-17, verrotti2012photosensitivityepidemiologygenetics pages 1-2, zhang2023electroclinicalcharacteristicsof pages 1-2)	HPO: Childhood onset; Adolescent onset; Female predominance	Human cohort + reviews; moderate-strong
Triggers / provoking factors	Highest IPS sensitivity is typically around 10–20 Hz; triggers include sunlight flicker, television/screens, video games, LED/light flashes, and patterns; eye-closure sensitivity is prominent in many patients. (trenite2021theimportanceof pages 17-19, zhang2023electroclinicalcharacteristicsof pages 1-2, zhang2023electroclinicalcharacteristicsof pages 2-3, NCT04076410 chunk 1)	HPO: Seizure triggered by flickering light; Eye closure sensitivity; Environmental exposure terms for flashing light/pattern stimulation	Human cohort, trial protocol, reviews; strong
Anatomy / systems affected	Primary system: central nervous system, especially visual cortex/occipital cortex with spread to parietal, frontal, sensorimotor, cingulate, supplementary motor, and thalamic networks. (timar2024functionalnetworkdynamics pages 1-3, vaudano2017photosensitiveepilepsyis pages 1-2)	UBERON: brain; occipital lobe / visual cortex; thalamus; anterior cingulate cortex; supplementary motor area	Human EEG-fMRI/network studies; moderate
Cell types	Evidence most strongly implicates cortical excitatory-inhibitory microcircuits and thalamocortical neurons; syndrome-associated literature also points to interneuron dysfunction in broader generalized epilepsy biology. (vaudano2017photosensitiveepilepsyis pages 1-2, scheffer2024developmentalandepileptic pages 19-21)	CL: glutamatergic neuron; GABAergic interneuron; thalamic relay neuron	Indirect human mechanistic inference + broader epilepsy evidence; moderate/indirect
Core mechanism	Current model favors abnormal visual-network excitability plus impaired inhibitory control rather than a purely local occipital trigger. PSE patients show altered 3–4 Hz connectivity and reduced alpha-related inhibition of visual/sensorimotor networks at rest. (timar2024functionalnetworkdynamics pages 1-3, vaudano2017photosensitiveepilepsyis pages 1-2)	GO: regulation of membrane potential; synaptic transmission, GABAergic; visual perception; neuronal network synchronization; thalamocortical signaling	Human EEG-fMRI + scalp EEG network study; moderate-strong
Upstream/downstream pathophysiology	Upstream: genetically influenced susceptibility and visually evoked cortical-thalamocortical hyperexcitability. Downstream: PPR propagation from occipital to distributed frontoparietal/sensorimotor networks, producing myoclonus, absence, or generalized convulsions. (timar2024functionalnetworkdynamics pages 1-3, vaudano2017photosensitiveepilepsyis pages 1-2)	GO: sensory stimulus response; action potential propagation; seizure; neuron-neuron synaptic transmission	Human mechanistic studies + reviews; moderate
Genetics	PSE is genetically heterogeneous. Evidence supports susceptibility and syndrome association rather than a single universal causal gene. CHD2 is repeatedly highlighted; photosensitivity also occurs in SCN1A-related Dravet syndrome and in broader epilepsy gene contexts including GABRA1/GABRG2 and SYNGAP1. (vaudano2017photosensitiveepilepsyis pages 1-2, scheffer2024developmentalandepileptic pages 19-21)	Gene terms: CHD2, SCN1A, GABRA1, GABRG2, SYNGAP1; MONDO-linked syndrome annotation as applicable	Human genetic review/primer evidence; moderate, heterogeneous
Inheritance	Inheritance is usually complex or syndrome-specific; familial aggregation is recognized, but penetrance/expressivity depend on the underlying epilepsy syndrome or susceptibility background. (brazzo2010mechanismsofaltered pages 12-17, verrotti2012photosensitivityepidemiologygenetics pages 1-2, vaudano2017photosensitiveepilepsyis pages 1-2)	HPO: Family history of seizures; inheritance term often multifactorial/variable	Reviews + limited cohort observations; moderate
Diagnostics	Standard diagnosis relies on EEG with intermittent photic stimulation (IPS), often across eye-open, eyes-closed, and eye-closure conditions, with quantification by standardized photosensitivity range (SPR). Differential diagnosis includes migraine/headache disorders, nonepileptic visual discomfort, and focal occipital epilepsies/syndromes. (verrotti2012photosensitivityepidemiologygenetics pages 1-2, zhang2023electroclinicalcharacteristicsof pages 2-3, moncada2023virtualrealityand pages 1-2)	LOINC/EEG term names; HPO: Abnormal EEG with generalized spike-wave complexes; Photoparoxysmal response	Human clinical practice/review + protocol evidence; strong
Treatment	Broad-spectrum ASMs are standard; valproate and levetiracetam are repeatedly reported as effective/common choices. In a proof-of-principle trial, cenobamate partially or completely suppressed PPR in most evaluable patients at 250–400 mg. (trenite2019suppressionofthe pages 1-2, zhang2023electroclinicalcharacteristicsof pages 1-2)	NCIT: Valproic Acid; Levetiracetam; Cenobamate; Anticonvulsant therapy	Human cohort + interventional study; moderate for PPR suppression, weaker for long-term seizure control
Prevention / non-pharmacologic management	Trigger avoidance is central: reduce exposure to flicker/patterns/screens, use monocular occlusion in acute exposure, and consider protective tinted lenses. A lens protocol cites prior Z1 lens abolition of PPRs in 75.9% of 610 patients. (verrotti2012photosensitivityepidemiologygenetics pages 1-2, trenite2021theimportanceof pages 17-19, NCT04076410 chunk 1)	NCIT/intervention terms: Protective eyewear; Behavioral avoidance; Patient education	Review + clinical trial protocol citing prior large series; moderate
Epidemiology	Photosensitivity is reported in about 5–10% of epilepsy overall, but much higher in some syndromes (for example JME, Dravet syndrome). In the 2023 single-center Chinese pediatric sample, PSE represented 7.79% of children with epilepsy. (brazzo2010mechanismsofaltered pages 12-17, timar2024functionalnetworkdynamics pages 1-3, zhang2023electroclinicalcharacteristicsof pages 1-2, vaudano2017photosensitiveepilepsyis pages 1-2)	Epidemiology descriptors only	Human cohort + reviews; moderate
Recent developments (2023–2024)	Recent work includes a 2023 pediatric electroclinical cohort, 2023 VR/ML work on automated PPR detection, and a 2024 network study showing frequency- and type-dependent connectivity abnormalities; these advances mainly refine diagnosis/biomarkers rather than establish new disease-specific therapies. (timar2024functionalnetworkdynamics pages 1-3, zhang2023electroclinicalcharacteristicsof pages 1-2, moncada2023virtualrealityand pages 1-2)	Diagnostic biomarker terms; EEG-based digital biomarker	Recent human cohort/computational/preprint evidence; emerging
Models / comparative biology	Useful but indirect models include photosensitive baboon and chicken models, plus zebrafish/mouse epilepsy systems for mechanistic and antiseizure screening work; model translation to human PSE remains incomplete. (brazzo2010mechanismsofaltered pages 12-17)	NCBI Taxon terms as applicable; model organism annotation	Preclinical/indirect evidence; limited
Major evidence gaps	No single definitive causal gene for all PSE; limited validated biomarkers beyond IPS-EEG/PPR; sparse data on quality of life, long-term prognosis, protective genetic factors, and PSE-specific omics (single-cell, spatial transcriptomic, proteomic, metabolomic, epigenomic) or chromosomal abnormalities. (verrotti2012photosensitivityepidemiologygenetics pages 1-2, timar2024functionalnetworkdynamics pages 1-3, scheffer2024developmentalandepileptic pages 19-21, moncada2023virtualrealityand pages 1-2)	Knowledge gap annotation; no robust ontology ID needed	Evidence gap synthesis; strong confidence in absence/scarcity of data

Table: This compact table summarizes evidence-backed findings for a photosensitive epilepsy knowledge-base entry, including disease definition, phenotypes, mechanisms, genetics, diagnostics, treatment, epidemiology, and key gaps. It is designed for ontology-aware curation while avoiding overstatement where evidence is limited or indirect.

1. Disease information

Definition and terminology

Photosensitivity is the neurophysiological tendency for visual stimulation to evoke epileptiform EEG activity. PSE is diagnosed when this susceptibility is clinically situated within epilepsy, especially when seizures are reproducibly provoked by flicker or patterns. The PPR is generally stimulus-independent epileptiform activity—occipital spikes, posterior spread, or generalized spike/polyspike-wave—rather than the normal, stimulus-locked photic-driving response. PPR is commonly graded from Waltz type 1 (occipital spikes) through type 4 (generalized spike/polyspike-wave); types 3–4 are most clinically associated with epilepsy. A photomyoclonic response, consisting of frontally dominant muscle artifact time-locked to flashes, is a non-cerebral response and an important diagnostic distinction. (brazzo2010mechanismsofaltered pages 12-17, zhang2023electroclinicalcharacteristicsof pages 2-3, moncada2023virtualrealityand pages 1-2)

Synonyms/related labels: photogenic epilepsy, photic-induced epilepsy, visually sensitive epilepsy, visually provoked seizures, visual reflex epilepsy, epilepsy with photosensitivity, pure photosensitive epilepsy, photosensitive occipital lobe epilepsy, and video-game epilepsy. “Jeavons syndrome” is now usually termed epilepsy with eyelid myoclonia and is a related syndrome rather than a synonym for all PSE.

Identifiers

MONDO: MONDO:0015643, photosensitive epilepsy. Open Targets recognizes this disease entry but currently returns no associated targets, supporting the conclusion that there is no single universally assigned molecular target. (OpenTargets Search: photosensitive epilepsy)
MeSH: Epilepsy, Reflex, D020195; broader Epilepsy, D004827. (NCT00784212 chunk 1)
ICD-10: no dedicated PSE code; coding generally falls under G40 epilepsy categories, selected according to focal/generalized syndrome and intractability.
ICD-11: classify under the underlying epilepsy type/reflex-seizure context; no uniquely validated PSE code was established in the retrieved evidence.
OMIM/Orphanet: no single disease-level entry adequately represents all PSE. OMIM entries apply to an underlying monogenic syndrome, where present.
Suggested SNOMED/HPO concepts: photosensitive epilepsy; reflex seizure; photoparoxysmal response; seizure triggered by flickering light.

This report synthesizes aggregated disease-level resources, published cohorts, mechanistic imaging studies, and trial registries, not individual EHR records.

2. Etiology and risk/protective factors

Causal and susceptibility factors

PSE usually reflects genetically influenced network susceptibility plus a visual exposure. In isolated/common PSE, inheritance is complex and no single causal gene explains most cases. In syndromic disease, a pathogenic variant may cause the broader epilepsy syndrome, with photosensitivity as one variably penetrant feature. Reviews report onset usually before 20 years, a puberty-related peak, female excess, and familial aggregation. (brazzo2010mechanismsofaltered pages 12-17, verrotti2012photosensitivityepidemiologygenetics pages 1-2, vaudano2017photosensitiveepilepsyis pages 1-2)

Relevant genes include:

CHD2: the most consistently emphasized gene for photosensitivity; rare/de novo pathogenic variants cause CHD2-related developmental and epileptic encephalopathy, often with myoclonic and visually sensitive seizures. Human data also show enrichment of rare CHD2 variants among photosensitive epilepsy cases. (vaudano2017photosensitiveepilepsyis pages 1-2, scheffer2024developmentalandepileptic pages 19-21)
SCN1A: pathogenic germline variants cause Dravet syndrome and related epilepsies; approximately 40% of Dravet patients may show photosensitivity, sometimes early in infancy. Photosensitivity is a syndrome feature, not evidence that SCN1A causes ordinary isolated PSE. (brazzo2010mechanismsofaltered pages 12-17, trenite2026howandwhen pages 9-12, scheffer2024developmentalandepileptic pages 19-21)
SYNGAP1, GABRA1, GABRG2 and other epilepsy genes can occur in disorders with photosensitivity, but current evidence does not justify treating them as universal PSE genes.
Historical linkage signals include 6p21, 7q32, and 16p13, but linkage has not yielded a clinically definitive common causal allele.

For a patient with isolated PSE and no developmental disorder, labeling a rare variant as pathogenic requires standard ACMG/AMP evidence; PPR association alone is insufficient. No recurrent variant, protective allele, carrier frequency, founder mutation, anticipation, or germline-mosaicism rate is established for PSE as a single entity.

Environmental and lifestyle risk factors

Provocative exposures include high-contrast flicker, television/computer/mobile displays, video games, LED/strobe lighting, sunlight interrupted by trees or railings, reflected sunlight on water or snow, and striped/grating/checkerboard patterns. Red stimulation around 600–700 nm is particularly provocative in susceptible individuals. The most sensitive frequencies commonly lie around 10–20 Hz, although the clinically relevant range is broader and individual-specific. Sleep deprivation, stress, alcohol, medication nonadherence, and prolonged/intense exposure can lower seizure threshold but are precipitants, not causes of inherited photosensitivity. (trenite2021theimportanceof pages 17-19, NCT00609245 chunk 1, zhang2023electroclinicalcharacteristicsof pages 1-2, NCT04076410 chunk 1)

Protective factors and gene–environment interaction

There is no validated genetic protective variant. Environmental protection consists of reducing retinal input or stimulus intensity: increasing viewing distance, reducing screen size/brightness/contrast, avoiding provocative content, maintaining ambient room lighting, taking breaks, and rapidly covering one eye rather than merely closing both eyes. Monocular occlusion reduces binocular cortical summation. Blue/red-attenuating lenses can reduce PPR. The Z1 lens reportedly abolished PPR in 75.9% of 610 tested patients, although this is an electrophysiological endpoint and the very dark lens has practical limitations. (trenite2021theimportanceof pages 17-19, NCT04076410 chunk 1)

The central gene–environment chain is: inherited or syndrome-specific network vulnerability → exposure within the individual’s spatial, chromatic, luminance, and frequency sensitivity range → excessive visual-cortical synchronization → propagation to distributed seizure networks.

3. Phenotypes

Clinical expression is episodic and ranges from EEG-only PPR to eyelid flutter, eyelid myoclonia, myoclonic jerks, absences, focal visual seizures, and generalized tonic–clonic seizures. Visual aura, headache, nausea, or impaired awareness can accompany events. Generalized tonic–clonic seizures are commonly reported as the most consequential phenotype. Self-induction—waving fingers before the eyes, seeking sunlight, or repeatedly closing the eyes—occurs particularly in epilepsy with eyelid myoclonia or “sunflower” phenotypes. (brazzo2010mechanismsofaltered pages 12-17, trenite2021theimportanceof pages 17-19)

A 2023 single-center Chinese pediatric cohort provides recent quantitative data: PSE constituted 31/398 epilepsy cases (7.79%); mean onset was 7.84 ± 3.28 years; 24/31 were female; IPS induced an electroclinical seizure in 13/31 (41.94%) and EEG-only discharge in 18/31 (58.06%). Eye-closure IPS was positive in 83.87%, versus 41.94% with eyes open and 35.48% with eyes continuously closed. Thirty of 31 had epilepsy with photosensitivity and only one had pure PSE; 28/31 had spontaneous interictal epileptiform discharges. Imaging was normal in all 23 imaged patients. (zhang2023electroclinicalcharacteristicsof pages 1-2, zhang2023electroclinicalcharacteristicsof pages 2-3)

Exact abstract quote: “The highest range of frequency sensitivity of the IPS test for the induction of EEG epileptic discharge or electroclinical seizures was within 10–20 Hz.” — Zhang et al., published 9 March 2023, DOI: https://doi.org/10.3389/fped.2023.994817. (zhang2023electroclinicalcharacteristicsof pages 1-2)

Suggested HPO annotations include Generalized tonic-clonic seizure, Myoclonic seizure, Absence seizure, Eyelid myoclonia, Focal visual seizure/visual aura, Abnormal EEG, Generalized spike-and-wave, Photoparoxysmal response, Seizure triggered by flickering light, Eye-closure sensitivity, and Childhood/adolescent onset. Exact current HPO identifiers should be verified against the release used by the knowledge base.

Quality of life: trigger avoidance can restrict screen use, education, employment, driving, entertainment, and social participation and can produce anticipatory anxiety. Direct PSE-specific EQ-5D/SF-36 estimates are sparse. The ongoing lens study explicitly measures adherence, autonomy, seizure frequency, tolerability, and perceived quality-of-life improvement, illustrating the present evidence gap. (NCT04076410 chunk 1)

4. Genetic and molecular information

PSE is best curated as a phenotype with heterogeneous genetic architecture. CHD2 has the most direct association, whereas SCN1A, SYNGAP1, GABRA1/GABRG2, and other genes generally define syndromes in which photosensitivity is one manifestation. The Open Targets disease record has no assigned targets for MONDO:0015643. (OpenTargets Search: photosensitive epilepsy, vaudano2017photosensitiveepilepsyis pages 1-2)

For syndromic testing, variants may be germline de novo or inherited and may include missense, nonsense, frameshift, splice, copy-number, or other loss-of-function changes; functional direction must be determined gene by gene. For example, SCN1A disorders include both loss- and gain-of-function spectra with different treatment implications. No characteristic somatic mutation, chromosomal rearrangement, methylation signature, pathogenic repeat expansion, or population allele frequency defines PSE itself. (scheffer2024developmentalandepileptic pages 19-21)

Modifier genes and epigenetics: plausible but unvalidated at clinically actionable PSE-specific levels. Hormonal/developmental effects are suggested by the female and pubertal peak, but a defined endocrine mechanism or epigenetic signature is lacking.

5. Environmental information

PSE is not caused by infection, toxin, pollution, radiation injury, smoking, or diet in the usual sense. Its disease-relevant environmental exposure is visual stimulation. Artificial media are important real-world exposures: the 1997 Pokémon broadcast reportedly provoked seizures in 685 Japanese children and drove broadcast-safety standards. (zhang2023electroclinicalcharacteristicsof pages 1-2)

Lifestyle management should prioritize regular sleep, ASM adherence, moderation/avoidance of alcohol where relevant, safe screen practices, and individualized recognition of trigger frequencies and patterns. No vaccine, antimicrobial intervention, or infectious-agent annotation is applicable.

6. Mechanism and pathophysiology

Causal chain

Upstream susceptibility: genetically and developmentally influenced imbalance of excitation and inhibition in visual and generalized epilepsy networks.
Sensory entrainment: flicker/pattern input activates retinal–geniculate–occipital pathways; provocative frequencies efficiently synchronize cortical populations.
Failure of inhibition: reduced alpha-related inhibition and altered GABAergic control allow excessive occipital synchronization.
Network recruitment: pathological 3–4 Hz spike/polyspike-wave activity propagates through parietal, frontal, anterior, sensorimotor, cingulate, supplementary motor, and thalamocortical networks.
Clinical manifestation: limited propagation produces occipital symptoms or EEG-only PPR; wider recruitment produces eyelid myoclonia, myoclonus, absence, impaired awareness, or bilateral tonic–clonic seizure. (timar2024functionalnetworkdynamics pages 1-3, vaudano2017photosensitiveepilepsyis pages 1-2)

A human EEG-fMRI study of 44 epilepsy patients and 16 controls found greater resting alpha power, smaller alpha-related BOLD decreases in occipital, sensorimotor, anterior cingulate, and supplementary motor cortices, and abnormal connectivity with visual thalamus only in photosensitive epilepsy. The authors concluded that the difference “consists of a decreased alpha-related inhibition of the visual cortex and sensory-motor networks at rest.” Published 20 February 2017; DOI: https://doi.org/10.1093/brain/awx009. (vaudano2017photosensitiveepilepsyis pages 1-2)

A December 2024 preprint analyzing 45 PSE patients found maximal pathological power at 10–20 Hz stimulation, with hypoconnected centroparietal and hyperconnected anterior/anterior–posterior regions in the 3–4 Hz PPR band. Importantly, visual evoked responses were mostly unchanged outside type 4, suggesting that visual-cortex hyperexcitability alone is not sufficient; abnormal large-scale connectivity facilitates propagation. DOI: https://doi.org/10.1101/2024.12.21.24319242. This is emerging, not yet definitive peer-reviewed evidence. (timar2024functionalnetworkdynamics pages 1-3)

Exact abstract conclusion: “PSE is a network effect modulated by hyperconnected anterior and anterio-posterior regions, accompanied by a hyperexcitable visual cortex.” (timar2024functionalnetworkdynamics pages 1-3)

Suggested annotations: GO—visual perception; response to light stimulus; regulation of membrane potential; neuron–neuron synaptic transmission; GABAergic synaptic transmission; regulation of neuronal synaptic plasticity; neural-network synchronization. CL—glutamatergic neuron, GABAergic interneuron, cortical neuron, thalamic relay neuron. No established PSE-specific immune, inflammatory, apoptotic, fibrotic, ischemic, or neurodegenerative mechanism exists, except where an underlying progressive syndrome supplies one.

Molecular profiling and advanced technologies

No replicated PSE-specific transcriptomic, proteomic, metabolomic, lipidomic, methylomic, single-cell, spatial-transcriptomic, or CRISPR-screen signature is clinically validated. Current advanced profiling is principally systems-level EEG, EEG-fMRI, connectivity analysis, and digital biomarkers. A VR/ML platform under study at Burgos University Hospital integrates programmable VR stimulation, EEG, and automated analysis. (moncada2023virtualrealityand pages 1-2)

Exact abstract quote: “This system is currently in study with subjects at Burgos University Hospital, Spain.” Published in the 2023 journal volume; DOI: https://doi.org/10.1007/s00521-022-06940-z. (moncada2023virtualrealityand pages 1-2)

7. Anatomical structures affected

The primary organ is the brain/CNS. The principal initiating tissue is nervous tissue in the bilateral occipital/visual cortex, but PSE is a network disorder rather than a structural occipital lesion. Relevant sites include primary and associative visual cortex, posterior parietal cortex, frontal/premotor cortex, sensorimotor cortex, anterior cingulate, supplementary motor area, pulvinar/posterior thalamus, and other thalamocortical circuitry. In focal photosensitive occipital epilepsy, occipital onset can remain focal or secondarily generalize. Routine MRI is commonly normal. (timar2024functionalnetworkdynamics pages 1-3, zhang2023electroclinicalcharacteristicsof pages 2-3, vaudano2017photosensitiveepilepsyis pages 1-2)

Suggested UBERON terms: brain, cerebral cortex, occipital lobe, visual cortex, parietal lobe, frontal lobe, motor cortex, anterior cingulate cortex, thalamus, pulvinar nucleus. Suggested GO cellular components: neuron projection, axon, dendrite, glutamatergic synapse, GABAergic synapse, voltage-gated ion-channel complex. There is no characteristic lateralized lesion; generalized PPR is bilateral.

8. Temporal development

Typical onset is pediatric or adolescent, commonly around puberty. Reviews cite an approximate 8–19-year onset range and peak near age 12; the recent pediatric cohort showed onset from 1 to 13.92 years. Adult-onset and persistence beyond 50 occur but are less common and warrant careful assessment for focal/acquired epilepsy and medication effects. (brazzo2010mechanismsofaltered pages 12-17, verrotti2012photosensitivityepidemiologygenetics pages 1-2, zhang2023electroclinicalcharacteristicsof pages 2-3)

The course is episodic and exposure-dependent, not continuously progressive in isolated PSE. Photosensitivity may diminish or disappear between ages 20 and 30, but persistence is common enough that medication withdrawal should not be based on age alone. Family history, broader epilepsy syndrome, persistent wide PPR range, spontaneous seizures, and early PPR in disorders such as Dravet syndrome may indicate less favorable outcome. Relapse after ASM withdrawal may approach 50% in selected literature cited by the lens trial. (trenite2021theimportanceof pages 17-19, zhang2023electroclinicalcharacteristicsof pages 2-3, NCT04076410 chunk 1)

9. Inheritance and population

Across epilepsy populations, photosensitivity is commonly estimated near 5%, with some sources using 5–10%; estimates vary with age, syndrome mix, IPS protocol, geography, and whether EEG-only PPR is included. It occurs in approximately 15% of generalized epilepsies in older syntheses and can be substantially higher in juvenile myoclonic epilepsy, Dravet syndrome, absence epilepsies, and progressive myoclonic epilepsies. A 2024 network report states that PSE affects about 5% of epilepsy patients worldwide; the 2023 pediatric specialty-center estimate was 7.79%, while that paper’s review cited 10–20% among children with epilepsy. These are not population incidence estimates and should not be conflated. (brazzo2010mechanismsofaltered pages 12-17, timar2024functionalnetworkdynamics pages 1-3, zhang2023electroclinicalcharacteristicsof pages 1-2)

Females predominate, particularly during adolescence: reported ratios range around 1.5–2 females per male, with 24 females to 7 males (3.43:1) in the recent Chinese cohort. No robust annual incidence per 100,000, ethnic-specific carrier frequency, consanguinity effect, or universal penetrance estimate is available. Inheritance is multifactorial for ordinary PSE and follows the underlying syndrome—often autosomal dominant/de novo—for monogenic cases. Expressivity and penetrance are variable. (brazzo2010mechanismsofaltered pages 12-17, verrotti2012photosensitivityepidemiologygenetics pages 1-2, zhang2023electroclinicalcharacteristicsof pages 1-2)

10. Diagnostics

Standard clinical approach

Diagnosis requires: (1) detailed seizure history linked to visual exposure; (2) syndrome classification; and (3) EEG with standardized IPS, generally testing eye closure, eyes closed, and eyes open. Pattern stimulation is useful if patterned images are suspected. IPS proceeds through ascending and descending standard frequencies and stops promptly when generalized PPR emerges. The standardized photosensitivity range (SPR) is the number/range of flash frequencies evoking PPR and serves as a reproducible quantitative biomarker. (NCT00609245 chunk 1, NCT03686033 chunk 1, zhang2023electroclinicalcharacteristicsof pages 2-3)

The 2023 study used 1–60 Hz IPS, 10-second trains separated by at least seven seconds, and terminated stimulation when PPR appeared to reduce seizure risk. Clinical laboratories should follow current IFCN/ILAE-compatible protocols rather than reproduce research settings without safeguards. (timar2024functionalnetworkdynamics pages 1-3, zhang2023electroclinicalcharacteristicsof pages 2-3)

MRI is indicated when focal onset, abnormal examination, developmental regression, or acquired pathology is suspected, but isolated/genetic PSE commonly has normal structural imaging. There is no diagnostic blood, urine, CSF, biopsy, PET, proteomic, or metabolomic biomarker. (zhang2023electroclinicalcharacteristicsof pages 2-3)

Genetic testing

Genetic testing is not mandatory for otherwise typical isolated PSE. Use an epilepsy multigene panel or exome/genome sequencing when onset is infantile, seizures are drug-resistant, development is abnormal/regressing, dysmorphism or movement disorder exists, family history is strong, or a syndrome such as CHD2-, SCN1A-, or SYNGAP1-related epilepsy is suspected. Trio testing improves de novo-variant interpretation. CMA is appropriate for developmental disability/congenital anomalies; mitochondrial, repeat-expansion, or single-gene testing should be phenotype-driven. No newborn or general-population screening program exists.

Differential diagnosis

Rule out normal photic driving/photomyoclonic response, migraine aura, photophobia without epilepsy, syncope, psychogenic nonepileptic events, tics/stereotypies, retinal disease, and focal structural occipital epilepsy. Migraine visual symptoms usually evolve more slowly and last longer; epileptic visual phenomena tend to be brief, stereotyped, and may progress to impaired awareness or motor seizure. A PPR in an asymptomatic person indicates susceptibility, not automatically epilepsy. (verrotti2012photosensitivityepidemiologygenetics pages 1-2, moncada2023virtualrealityand pages 1-2)

11. Outcome and prognosis

Isolated PSE generally has a favorable survival outlook and is not known to reduce life expectancy independently. There are no credible PSE-specific 5- or 10-year survival statistics. Mortality and SUDEP risk are governed principally by the underlying epilepsy, especially ongoing generalized tonic–clonic seizures, nocturnal seizures, drug resistance, and adherence—not photosensitivity alone.

Morbidity includes injury during provoked seizures, driving restrictions, educational/occupational limitations, anxiety, avoidance behavior, and adverse effects of ASMs. Photosensitivity may remit in early adulthood, but spontaneous epilepsy may persist after PPR disappears. Conversely, PPR can remain without frequent real-world seizures. A wide or persistent SPR and clinical symptoms during IPS imply greater daily-life seizure likelihood. (trenite2021theimportanceof pages 17-19, zhang2023electroclinicalcharacteristicsof pages 2-3)

12. Treatment

Management algorithm

Classify the underlying epilepsy and distinguish EEG-only PPR from clinically significant visually provoked seizures.
Educate regarding triggers and emergency monocular occlusion.
If events are rare and exclusively avoidable, environmental control may suffice.
If spontaneous seizures coexist, exposures cannot be reliably avoided, or events include impaired awareness/generalized convulsions, use an ASM appropriate to the entire syndrome.
Reassess clinical seizures and, when useful, SPR/PPR; do not infer long-term seizure freedom solely from acute PPR suppression.

Valproate is historically the most effective broad-spectrum option for generalized photosensitive epilepsies; it increases inhibitory tone and has multiple ion-channel effects. Its major limitations are teratogenicity, weight/metabolic effects, tremor, and other toxicity, making it inappropriate or tightly restricted for many people who could become pregnant. Levetiracetam (SV2A ligand) is frequently used and avoids teratogenic risk to the same degree, though behavioral adverse effects occur. Lamotrigine, topiramate, brivaracetam, and syndrome-specific therapies may be considered. Sodium-channel blockers can aggravate myoclonus or absence in some generalized epilepsies, so treatment must follow syndrome—not simply the presence of PPR. In the 2023 cohort, valproate and levetiracetam were the common effective mono/combination therapies, but the observational design does not establish comparative efficacy. (NCT00401648 chunk 1, zhang2023electroclinicalcharacteristicsof pages 1-2)

Cenobamate evidence: in a six-patient phase 2a proof-of-principle study, 250 mg yielded complete PPR suppression in 1/4 and partial suppression in 4/4; 400 mg yielded complete suppression in 1/4 and partial suppression in 2/4. Exposure of 201–400 μg·h/mL produced partial suppression in 4/6 (66%); common adverse events were dizziness and somnolence. This was Class III evidence for acute PPR suppression, not a long-term PSE effectiveness trial. Published August 2019; DOI: https://doi.org/10.1212/WNL.0000000000007894; NCT00616148. (trenite2019suppressionofthe pages 1-2)

Other PPR-model studies include completed brivaracetam phase 2 (NCT00401648; n=20), valproate phase 4 (NCT00609245; n=13), and the AMPA/kainate antagonist selurampanel/BGG492 phase 2 (NCT00784212; n=13; associated PMID 25963722). These studies demonstrate pharmacodynamic effects but are too small to define routine long-term treatment algorithms. (NCT00401648 chunk 1, NCT00609245 chunk 1, NCT00784212 chunk 1)

Recent/experimental activity:

NPT 2042, 160 or 240 mg, completed a randomized quadruple-masked phase 1 crossover PPR study in five adults (NCT06525649; started 21 August 2024, completed 26 June 2025); no outcome results were available in the retrieved record. (NCT06525649 chunk 1)
Inhaled CBD RLS103 (4/8 mg) was terminated for poor enrollment after only two participants (NCT05678881), illustrating the feasibility limitations of this rare biomarker population. (NCT05678881 chunk 1)
E2082 phase 2 enrolled eight and was terminated after safety review (NCT03686033). (NCT03686033 chunk 1)
A pediatric lens study, NCT04076410, compares four new spectral lenses with Z1; its registry status was unknown after a last known active-not-recruiting state, with estimated completion in January 2026. (NCT04076410 chunk 1)

No gene, cell, RNA, immune, or surgical therapy is approved specifically for isolated PSE. Surgery is relevant only if a discrete focal epileptogenic lesion exists. Suggested NCIT intervention concepts: Anticonvulsant Therapy, Valproic Acid, Levetiracetam, Brivaracetam, Cenobamate, Cannabidiol, Protective Eyewear, Patient Education.

13. Prevention

Primary prevention of genetic susceptibility is unavailable. Public-health prevention can reduce provoked events through broadcast, game, web-animation, nightclub/strobe, and workplace-lighting standards controlling flash frequency, luminance contrast, red saturation, patterned area, and screen coverage. The Pokémon event demonstrates the potential population impact of unsafe content. (zhang2023electroclinicalcharacteristicsof pages 1-2)

Secondary prevention consists of early recognition, standardized IPS-EEG in appropriately selected patients, syndrome diagnosis, and genetic evaluation where developmental or severe disease suggests a monogenic cause. Routine screening of asymptomatic people is not recommended.

Tertiary prevention includes individualized trigger avoidance, adherence, adequate sleep, responsible alcohol use, protective lenses, seizure first-aid planning, and control of generalized tonic–clonic seizures. During unexpected exposure, turn away and cover one eye with the palm; simply squeezing both eyes shut can retain flicker transmission and may itself provoke eye-closure-sensitive PPR. (trenite2021theimportanceof pages 17-19, NCT04076410 chunk 1)

Genetic counseling should explain heterogeneous inheritance and avoid assigning Mendelian recurrence risk without a molecular diagnosis. If a pathogenic syndrome-causing variant is found, cascade, prenatal, or preimplantation testing can be discussed according to that disorder.

14. Other species and natural disease

Naturally photosensitive epilepsy-like phenotypes are best documented in Papio papio baboons (NCBI Taxonomy: Papio papio) and photosensitive chicken lines, historically including Fayoumi-derived strains. Baboons develop generalized epileptiform responses and seizures to photic stimulation and are valuable for generalized network physiology and pharmacology. Chicken models provide strong reflex photosensitivity but differ substantially from human cortical organization. Neither condition is zoonotic or transmissible. (brazzo2010mechanismsofaltered pages 12-17)

Domestic dogs and cats may have reflex seizures, but there is insufficient evidence to define a common veterinary analogue of human PSE or to assign a validated VBO breed term. Comparative orthologue annotations should be attached to the specific modeled gene—such as Chd2/CHD2 or Scn1a/SCN1A—rather than to PSE globally.

15. Model organisms

Relevant systems include genetic generalized epilepsy in baboons; photosensitive chicken strains; zebrafish and mouse models of CHD2-, SCN1A-, GABA-receptor-, or other syndrome-associated epilepsies; and acute chemoconvulsant models. Zebrafish permit high-throughput behavioral/electrophysiological drug screening, while mice permit cell-type and circuit manipulation. BRD2-haploinsufficient mice, for example, show reduced GABAergic neuronal populations and sex-specific seizure susceptibility, but they are an indirect generalized-epilepsy model rather than a validated model of human PSE. (vaudano2017photosensitiveepilepsyis pages 1-2, scheffer2024developmentalandepileptic pages 19-21)

Key limitations are species-specific visual systems, stimulation paradigms, developmental timing, and failure to reproduce the full human combination of PPR, subjective visual symptoms, spontaneous seizures, and psychosocial burden. Models are therefore most suitable for studying excitation–inhibition balance, visual-network propagation, gene function, and initial ASM screening—not for directly predicting clinical effectiveness.

Evidence appraisal and knowledge gaps

The strongest current evidence concerns the electroclinical phenotype, standardized IPS-EEG, age/sex distribution, visual triggers, and network physiology. Major gaps are population incidence, prospective natural history, PSE-specific quality-of-life measures, protective genetics, validated molecular biomarkers, comparative long-term ASM trials, and disease-specific omics. Recent 2023–2024 work improves pediatric characterization and network/digital biomarker analysis but has not produced a new disease-specific standard therapy. The 2024 connectivity work remains a preprint and should be curated accordingly. (timar2024functionalnetworkdynamics pages 1-3, zhang2023electroclinicalcharacteristicsof pages 1-2, moncada2023virtualrealityand pages 1-2)

Finally, most medication studies use acute PPR/SPR suppression as a surrogate endpoint. This model is sensitive and valuable for early drug development, but acute electrophysiological suppression must not be represented as equivalent to durable prevention of spontaneous or real-world visually provoked seizures. (NCT00609245 chunk 1, trenite2019suppressionofthe pages 1-2)

References

(brazzo2010mechanismsofaltered pages 12-17): Mechanisms of altered cortical excitability in photosensitive epilepsy This article has 1 citations.
(verrotti2012photosensitivityepidemiologygenetics pages 1-2): Alberto Verrotti, Francesca Beccaria, Federica Fiori, Alessandra Montagnini, and Giuseppe Capovilla. Photosensitivity: epidemiology, genetics, clinical manifestations, assessment, and management. Epileptic Disorders, 14:349-362, Dec 2012. URL: https://doi.org/10.1684/epd.2012.0539, doi:10.1684/epd.2012.0539. This article has 77 citations and is from a peer-reviewed journal.
(vaudano2017photosensitiveepilepsyis pages 1-2): Anna Elisabetta Vaudano, Andrea Ruggieri, Pietro Avanzini, Giuliana Gessaroli, Gaetano Cantalupo, Antonietta Coppola, Sanjay M. Sisodiya, and Stefano Meletti. Photosensitive epilepsy is associated with reduced inhibition of alpha rhythm generating networks. Brain, 140:981–997, Apr 2017. URL: https://doi.org/10.1093/brain/awx009, doi:10.1093/brain/awx009. This article has 72 citations and is from a highest quality peer-reviewed journal.
(trenite2019suppressionofthe pages 1-2): Dorothee G.A. Kasteleijn- Nolst Trenite, Bree D. DiVentura, John R. Pollard, Gregory L. Krauss, Sarah Mizne, and Jacqueline A. French. Suppression of the photoparoxysmal response in photosensitive epilepsy with cenobamate (ykp3089). Neurology, 93:e559-e567, Aug 2019. URL: https://doi.org/10.1212/wnl.0000000000007894, doi:10.1212/wnl.0000000000007894. This article has 61 citations and is from a highest quality peer-reviewed journal.
(timar2024functionalnetworkdynamics pages 1-3): Lili Timar, Sina Deplazes, Julia Bothmann, Roland Renzel, Debora Ledergerber, Tena Dubcek, and Lukas Imbach. Functional network dynamics in photosensitive epilepsy depend on stimulation frequency and photosensitivity type. MedRxiv, Dec 2024. URL: https://doi.org/10.1101/2024.12.21.24319242, doi:10.1101/2024.12.21.24319242. This article has 0 citations.
(moncada2023virtualrealityand pages 1-2): Fernando Moncada, Sofía Martín, Víctor M. González, Víctor M. Álvarez, Beatriz García-López, Ana Isabel Gómez-Menéndez, and José R. Villar. Virtual reality and machine learning in the automatic photoparoxysmal response detection. Neural Computing and Applications, 35:5643-5659, Jan 2023. URL: https://doi.org/10.1007/s00521-022-06940-z, doi:10.1007/s00521-022-06940-z. This article has 30 citations and is from a peer-reviewed journal.
(zhang2023electroclinicalcharacteristicsof pages 1-2): Bo Zhang, Tianyu Chen, Xiaosheng Hao, Meiying Xin, and Jianmin Liang. Electroclinical characteristics of photosensitive epilepsy: a retrospective study of 31 chinese children and literature review. Frontiers in Pediatrics, Mar 2023. URL: https://doi.org/10.3389/fped.2023.994817, doi:10.3389/fped.2023.994817. This article has 4 citations.
(zhang2023electroclinicalcharacteristicsof pages 2-3): Bo Zhang, Tianyu Chen, Xiaosheng Hao, Meiying Xin, and Jianmin Liang. Electroclinical characteristics of photosensitive epilepsy: a retrospective study of 31 chinese children and literature review. Frontiers in Pediatrics, Mar 2023. URL: https://doi.org/10.3389/fped.2023.994817, doi:10.3389/fped.2023.994817. This article has 4 citations.
(trenite2021theimportanceof pages 17-19): The Importance of Photosensitivity for Epilepsy This article has 7 citations.
(NCT04076410 chunk 1): Ana Checa-Ros, MD, PhD. Efficacy of Lenses in Abolishing Photoparoxysmal Responses. Aston University. 2021. ClinicalTrials.gov Identifier: NCT04076410
(scheffer2024developmentalandepileptic pages 19-21): Ingrid E. Scheffer, Sameer Zuberi, Heather C. Mefford, Renzo Guerrini, and Amy McTague. Developmental and epileptic encephalopathies. Nature reviews. Disease primers, 10 1:61, Sep 2024. URL: https://doi.org/10.1038/s41572-024-00546-6, doi:10.1038/s41572-024-00546-6. This article has 167 citations.
(OpenTargets Search: photosensitive epilepsy): Open Targets Query (photosensitive epilepsy, 10 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(NCT00784212 chunk 1): Effect of BGG492 on EEG in Patients With Photosensitive Epilepsy. Novartis Pharmaceuticals. 2008. ClinicalTrials.gov Identifier: NCT00784212
(trenite2026howandwhen pages 9-12): Dorothee Kasteleijn-Nolst Trenite and Boulenouar Mesraoua. How and When to Treat Visually-Evoked Seizures. IntechOpen, May 2026. URL: https://doi.org/10.5772/intechopen.1015299, doi:10.5772/intechopen.1015299. This article has 0 citations.
(NCT00609245 chunk 1): Bassel Abou-Khalil. Effect of Valproic Acid Concentration on Photic Response. Vanderbilt University Medical Center. 2007. ClinicalTrials.gov Identifier: NCT00609245
(NCT03686033 chunk 1): A Study to Evaluate the Pharmacodynamic Activity of E2082 in Adult Participants With Photosensitive Epilepsy. Eisai Inc.. 2018. ClinicalTrials.gov Identifier: NCT03686033
(NCT00401648 chunk 1): Effect of Brivaracetam in Photosensitive Epileptic Subjects. UCB Pharma. 2002. ClinicalTrials.gov Identifier: NCT00401648
(NCT06525649 chunk 1): A Double Blind, Randomized, Cross-over Study Examining the Suppression of the Photoparoxysmal EEG Response With NPT 2042. NeuroPro Therapeutics, Inc.. 2024. ClinicalTrials.gov Identifier: NCT06525649
(NCT05678881 chunk 1): Safety, Tolerability, and Efficacy of RLS103 in a Clinical Model of Photosensitive Epilepsy. Receptor Life Sciences. 2022. ClinicalTrials.gov Identifier: NCT05678881

Artifacts

Edison artifact artifact-00

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	9
Resolved	9
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	9
On topic	3
Off topic	0

All extracted references resolved successfully.

Ask OpenScientist

OpenScientist Report

Classifications

Mappings

Inheritance

Subtypes

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Environmental Factors

Diagnosis

Epidemiology

Differential Diagnoses

Clinical Trials

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Photosensitive Epilepsy: Disease Characteristics Research Report

Executive summary

1. Disease information

Definition and terminology

Identifiers

2. Etiology and risk/protective factors

Causal and susceptibility factors

Environmental and lifestyle risk factors

Protective factors and gene–environment interaction

3. Phenotypes

4. Genetic and molecular information

5. Environmental information

6. Mechanism and pathophysiology

Causal chain

Molecular profiling and advanced technologies

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

10. Diagnostics

Standard clinical approach

Genetic testing

Differential diagnosis

11. Outcome and prognosis

12. Treatment

Management algorithm

13. Prevention

14. Other species and natural disease

15. Model organisms

Evidence appraisal and knowledge gaps

Artifacts

Reference Validation