| Domain | Established finding | Evidence type / key study and year | Ontology suggestions | Confidence or gap |
|---|---|---|---|---|
| Disease definition | Hemiconvulsion-Hemiplegia-Epilepsy (HHE) syndrome is an acquired pediatric epilepsy-related syndrome characterized by a stereotyped sequence: prolonged unilateral convulsive status, followed by persistent hemiplegia, then later focal epilepsy; Open Targets lists a related entity as “idiopathic hemiconvulsion-hemiplegia syndrome.” (pqac-00000000) | Disease knowledgebase context: Open Targets disease entry; classic syndrome literature exists but was not available in current tool context (2024 Open Targets context) (pqac-00000000) | MONDO: related entity present but exact HHE mapping uncertain; NCIT: epilepsy syndrome term uncertain; HPO: Hemiconvulsion/Hemiplegia/Epilepsy terms applicable, exact IDs not verified | Moderate confidence for broad definition; exact ontology crosswalk for classic HHE remains uncertain in available context |
| Classification / origin | The syndrome is best treated as acquired rather than monogenic, because the defining event is an acute destructive hemispheric injury associated with status epilepticus and subsequent cerebral hemiatrophy. | Human clinical syndrome literature cited by search results (Auvin 2012 review; Gastaut 1959; case series), but full text not available in current context | MONDO/Orphanet mapping uncertain; HPO suggestion: acquired cerebral hemiatrophy, hemiparesis, focal seizures | Moderate confidence; primary evidence not fully extracted in tool context |
| Acute trigger sequence | Typical presentation is prolonged febrile hemiclonic status epilepticus in infancy/early childhood, often after a febrile illness, preceding unilateral brain injury. | Human clinical reviews/case series identified by search: Tenney 2012; Auvin 2012; South African series 2012; exact extracted text unavailable | HPO: Febrile seizure term, Status epilepticus term, Clonic seizure term, Focal motor seizure term | Moderate confidence; exact percentages and onset distributions are a current data gap |
| Core neurologic deficit | Persistent contralateral hemiplegia/hemiparesis follows the acute hemiconvulsive episode and is a defining phenotype. | Human clinical syndrome literature identified in searches; not directly extracted | HPO: Hemiparesis; Hemiplegia; Motor developmental impairment if chronic | High confidence for phenotype, low confidence for frequency estimates |
| Epilepsy evolution | Delayed epilepsy commonly emerges after the acute hemiplegic phase, usually as chronic focal drug-resistant epilepsy in a subset of survivors. | Human longitudinal/surgical literature identified by search, including Kim et al. 2008 on delayed epilepsy surgery | HPO: Focal-onset seizure; Drug-resistant epilepsy; Developmental regression/cognitive impairment if present | Moderate confidence; exact latency and response rates not available in current context |
| Neuroimaging | Characteristic imaging pattern: acute unilateral hemispheric edema/swelling with diffusion restriction, followed over time by hemispheric atrophy/hemiatrophy and gliosis. | Human MRI/pathology studies identified in searches: Freeman 2002; Toldo 2007; Auvin 2007; Barcia 2013; exact text not extracted | UBERON: cerebral hemisphere; HPO: Cerebral hemiatrophy, Cerebral edema, Abnormal brain MRI; GO CC not specifically applicable | High confidence for qualitative MRI sequence; numerical timing details remain a gap |
| Electrophysiology | EEG is used to document focal hemispheric seizure activity acutely and later focal epileptiform abnormalities, but no syndrome-specific EEG biomarker is established. | Human clinical literature and epilepsy reviews; no dedicated biomarker evidence retrieved | HPO: Abnormal EEG; Focal epileptiform discharges (exact term ID unverified) | Moderate confidence; syndrome-specific EEG signatures are not well standardized |
| Pathology / mechanism | Available pathology literature supports inflammatory-degenerative hemispheric injury after prolonged seizures, with mechanistic hypotheses centered on excitotoxicity, cytotoxic edema, blood-brain barrier dysfunction, and secondary inflammation rather than a single causal gene. | Human pathology case reports/reviews identified by search (Auvin 2007; Serino 2014) plus general mechanistic support from seizure/brain-injury literature found in context | GO: excitatory neurotransmission, neuroinflammatory response, cell death, response to hypoxia; CL: cortical neuron, astrocyte, microglial cell | Moderate confidence; direct HHE molecular studies are sparse |
| Genetics | SCN1A variants have been reported only in a minority of HHE cases; the available literature supports “low incidence” and argues HHE is not a typical monogenic SCN1A disorder. | Human genetics study identified by search: Kim et al. 2013, “Low incidence of SCN1A genetic mutation in patients with hemiconvulsion–hemiplegia–epilepsy syndrome” | HGNC: SCN1A; HPO: Seizures precipitated by fever may overlap with Dravet-spectrum phenotypes | Moderate-to-high confidence for “not monogenic/low incidence”; exact mutation counts not available in current context |
| Differential diagnosis | Important differentials include Dravet syndrome/GEFS+ spectrum, FIRES/NORSE, Rasmussen encephalitis, stroke, alternating hemiplegia, encephalitis/encephalopathy, and structural or metabolic disorders causing unilateral edema and subsequent atrophy. | Human review literature identified by search; current tool context does not provide extracted differential tables | HPO overlap terms: hemiplegia, focal seizures, fever-associated seizures; MONDO terms uncertain | Moderate confidence; evidence synthesis limited by unavailable full texts |
| Management | Acute management is supportive neurocritical care plus standard status epilepticus treatment; chronic management includes antiseizure medications, rehabilitation, and evaluation for epilepsy surgery in medically refractory cases. | Human clinical reviews/case reports identified by search; no dedicated interventional trials retrieved | NCIT suggestions: anticonvulsant therapy, physical therapy, occupational therapy, epilepsy surgery/hemispherectomy (exact NCIT IDs unverified) | High confidence for real-world practice pattern; low confidence for comparative efficacy data |
| Surgical treatment | In selected patients with delayed refractory epilepsy and a functionally devastated hemisphere, hemispherectomy/hemispherotomy has been reported as a real-world treatment option with seizure benefit in case series. | Human surgical series identified by search: Kim et al. 2008; later hemispherectomy experience papers also identified | NCIT: Hemispherectomy / Hemispherotomy term uncertain; HPO: post-surgical seizure reduction not an HPO phenotype | Moderate confidence; no randomized evidence |
| Epidemiology | HHE is rare; the literature consists mainly of case reports, small series, and retrospective cohorts, with no robust population incidence estimate retrieved in current context. | Search results include small retrospective series (e.g., 35 cases, 10 cases, regional case series), but no population registry evidence extracted | MONDO/Orphanet prevalence term uncertain | High confidence that disease is rare; major quantitative epidemiology gap |
| Recent developments (2023-2024) | Recent searchable material is dominated by isolated case reports and broader epilepsy classification updates; no major 2023-2024 breakthrough mechanistic, genomic, or therapeutic trial program was retrieved. (pqac-00000000) | Search evidence and Open Targets show no disease-target associations in the retrieved context. (pqac-00000000) | Open Targets disease-target links absent; omics ontology suggestions not applicable | High confidence for evidence sparsity |
| Trials / translational research | No dedicated interventional clinical trials were retrieved for HHE; no disease-specific target program or drug-development signal was found in Open Targets. (pqac-00000000) | ClinicalTrials search: no relevant dedicated trial retrieved; Open Targets associatedTargets count = 0. (pqac-00000000) | NCIT: clinical trial not disease-specific; Open Targets disease-target association absent | High confidence for lack of dedicated trial/target evidence |
| Omics / biomarkers | No HHE-specific transcriptomic, proteomic, metabolomic, spatial, or single-cell studies were retrieved; no validated circulating biomarker or molecular diagnostic signature was identified. (pqac-00000000) | Evidence gap from tool searches and Open Targets context. (pqac-00000000) | GO/CL/omics terms not disease-specific; biomarker ontology mapping unavailable | High confidence that this is a major knowledge gap |


*Table: This table summarizes the most actionable disease-knowledge findings for Hemiconvulsion-Hemiplegia-Epilepsy syndrome and explicitly marks where evidence is based on classic clinical literature versus current gaps. It is useful for rapid knowledge-base curation because it links core syndrome features to ontology suggestions and highlights missing trials, targets, and omics data.*