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Classifications

Harrison's Part

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Mappings

MONDO

MONDO:0001309 oculomotor nerve paralysis

Primary MONDO disease identifier for this entry.

ICD-10-CM

ICD10CM:H49.0 Third [oculomotor] nerve palsy

ICD-10-CM H49.0 is the direct code for third (oculomotor) nerve palsy; laterality is expressed in the H49.00-H49.03 children.

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Definitions

2

Clinical syndrome definition for oculomotor nerve palsy

Oculomotor nerve palsy is diagnosed from weakness of the extraocular muscles supplied by cranial nerve III, with or without ptosis and pupillary involvement, after mimics such as myasthenia gravis, thyroid orbitopathy, and Horner syndrome have been excluded.

CASE_DEFINITION General clinical framing of third cranial nerve palsy

Show evidence (2 references)

PMID:30252368 SUPPORT Human Clinical

"Typical presentation includes ptosis, ophthalmoplegia, diplopia, and variable pupillary involvement, resulting in the characteristic down-and-out eye position in complete palsy."

States the defining clinical constellation of third cranial nerve palsy, including the variable pupil, which is what the case definition has to capture.

PMID:30592440 SUPPORT Human Clinical

"Oculomotor nerve palsy (ONP) is an important and common clinical diagnosis. Its main features are diplopia and ptosis."

Independent review confirming diplopia and ptosis as the cardinal presenting features on which the clinical diagnosis rests.

Anatomical localization definition

A lesion anywhere from the oculomotor nucleus in the midbrain to the terminal branches in the orbit can produce the syndrome, so localization along the nerve's course is part of the diagnostic definition rather than an afterthought.

CASE_DEFINITION Lesion localization along the course of cranial nerve III

Show evidence (2 references)

PMID:30252368 SUPPORT Human Clinical

"Lesions affecting the cranial nerve III can occur along its entire course, from the oculomotor nucleus in the midbrain to terminal branches in the orbit."

Establishes that the syndrome is defined by the affected nerve rather than by a single anatomical site, which is why localization is part of the workup.

PMID:21059515 SUPPORT Human Clinical

"Third nerve damage occurred in the subarachnoid space in 32%, the cavernous sinus in 23%, the brainstem in 14%, as a nonlocalized peripheral neuropathy in 18% and at an uncertain location in 13%."

Quantifies how lesion site is distributed across the nerve's course in a large personally-examined inpatient series.

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Subtypes

6

Ischaemic microvascular oculomotor nerve palsy

Acute painful third nerve palsy in an adult with vascular risk factors (diabetes mellitus, hypertension, dyslipidaemia, smoking), no causative lesion on imaging, and spontaneous recovery. Characteristically, though not invariably, pupil-sparing. The most common single aetiology in adults.

Show evidence (2 references)

PMID:38411317 SUPPORT Human Clinical

"The most common etiology was microvascular (n = 168, 26.5%), followed by vascular anomalies (n = 110, 17.4%), neoplastic (n = 86, 13.6%), inflammatory (n = 79, 12.5%), idiopathic (n = 60, 9.5%) and traumatic (n = 53, 8.4%)."

Establishes microvascular ischaemia as the single largest aetiological category of isolated oculomotor nerve palsy in a 633-patient hospital-wide series.

PMID:39510537 SUPPORT Human Clinical

"Ocular motor mononeuropathies affect cranial nerves III, IV and VI and are more frequent in diabetes mellitus, with oculomotor nerve involvement being predominant."

Supports diabetes mellitus as the paradigmatic vascular risk factor and cranial nerve III as the ocular motor nerve most often affected.

Compressive and aneurysmal oculomotor nerve palsy

Third nerve palsy from extrinsic mass effect on the cisternal nerve, most urgently by a posterior communicating artery aneurysm, and also by tumour, pituitary apoplexy, and uncal herniation. Painful, usually pupil-involving, and a neurosurgical emergency because the aneurysm may be about to rupture.

Show evidence (2 references)

PMID:33845117 SUPPORT Human Clinical

"Posterior communicating artery aneurysms (PCoAA) usually present with brain hemorrhage, but they might present with oculomotor nerve palsy (ONP) in about one out of five patients."

Quantifies how often a posterior communicating artery aneurysm declares itself through third nerve palsy rather than through haemorrhage.

PMID:38411317 SUPPORT Human Clinical

"Vascular anomalies included intracranial aneurysm (n = 89, 80.9%), dural arteriovenous fistula (n = 10, 9.1%), cavernous malformation (n = 9, 8.2%) and arteriovenous malformation (n = 2, 1.8%)."

Shows that intracranial aneurysm dominates the vascular-anomaly category that is the second most common cause of isolated oculomotor nerve palsy.

Traumatic oculomotor nerve palsy

Third nerve palsy following head injury, from stretch, contusion, or avulsion of the nerve, classically where it is tethered against the posterior petroclinoid ligament or the tentorial edge. The leading cause in childhood inpatient series and a major cause in young adults.

Show evidence (2 references)

PMID:21059515 SUPPORT Human Clinical

"Causes were trauma (26%), tumor (12%), diabetes (11%), aneurysm (10%), surgery (10%), stroke (8%), infection (5%), Guillain-Barre and Fisher syndromes (5%), idiopathic cavernous sinusitis (3%), benign self-limited (2%), miscellaneous (4%), and unknown (3%)."

In a large municipal inpatient population trauma was the single most common cause, establishing traumatic palsy as a major aetiological subtype.

PMID:16978866 SUPPORT Human Clinical

"The suggested mechanism of the oculomotor nerve palsy with pupil sparing in this case is stretching of the oculomotor nerve at the posterior petroclinoid ligament, maintaining an intact pupillomotor nerve."

Describes the stretch-at-a-tether-point mechanism that distinguishes traumatic palsy from compressive and ischaemic palsy.

Congenital oculomotor nerve palsy

Third nerve palsy present from infancy, usually unilateral and incomplete, associated on high-resolution MRI with hypoplasia, thinning, or frank agenesis of the oculomotor nerve and secondary atrophy of the muscles it supplies. A developmental nerve deficit, not an acquired lesion, and the most frequent presentation of third nerve palsy in childhood.

Show evidence (2 references)

PMID:30997520 SUPPORT Human Clinical

"Congenital oculomotor nerve palsy was mostly incomplete and hypoplasia or aplasia of the oculomotor nerve was apparent in one third of patients showing variable degrees of extraocular muscle atrophy, mostly of the medial rectus and inferior rectus muscles."

Establishes the defining structural correlate of the congenital subtype and its usually incomplete clinical expression.

PMID:16391633 SUPPORT Human Clinical

"Congenital-onset oculomotor nerve palsy was the most frequent presentation, followed by traumatic, neoplastic, vascular, and migrainous or para-infectious etiologies."

Supports congenital onset as the leading category in a paediatric cohort, in contrast with the adult aetiological distribution.

Inflammatory oculomotor nerve palsy

Third nerve palsy from inflammation of the nerve, its fascicle, or the cavernous sinus, with Tolosa-Hunt syndrome as the prototype. Diagnosed on an enhancing T2-hyperintense lesion affecting the nerve together with steroid responsiveness, it is the third largest aetiological category yet has the best recovery of any cause. Curated as an aetiological subtype because that category is solidly evidenced, even though the mechanism of the inflammation itself is not.

Show evidence (3 references)

PMID:38411317 SUPPORT Human Clinical

"The most common etiology was microvascular (n = 168, 26.5%), followed by vascular anomalies (n = 110, 17.4%), neoplastic (n = 86, 13.6%), inflammatory (n = 79, 12.5%), idiopathic (n = 60, 9.5%) and traumatic (n = 53, 8.4%)."

Places inflammatory aetiology at 12.5% of 633 cases, ahead of trauma, which is why it earns a subtype.

PMID:38411317 SUPPORT Human Clinical

"and the symptoms responded to steroid treatments"

Steroid responsiveness is part of how the anchoring cohort operationally defined the inflammatory category.

PMID:37853245 SUPPORT Human Clinical

"Isolated ocular motor nerve palsy was the most common (82.4%) finding of ophthalmoplegia, involving the oculomotor nerve in more than half of the cases (52.0%)."

Establishes that the prototypical inflammatory cause, Tolosa-Hunt syndrome, most often presents through the oculomotor nerve specifically.

Recurrent painful ophthalmoplegic neuropathy (formerly ophthalmoplegic migraine)

Rare disorder of repeated attacks of unilateral headache with ipsilateral ocular motor palsy, most often of cranial nerve III, with focal thickening and contrast enhancement of the nerve on MRI and usually full recovery. Reclassified by the International Headache Society in 2013 away from "ophthalmoplegic migraine" because the imaging indicates a neuropathy; the underlying mechanism remains unsettled.

Show evidence (2 references)

PMID:35659705 SUPPORT Human Clinical

"Ophthalmoplegic migraine, renamed "Recurrent Painful Ophthalmoplegic Neuropathy" (RPON) in 2013 by the International Headache Society is a rare neurologic disorder characterized by recurrent attacks of ophthalmoplegia associated to ipsilateral headache."

Defines the entity and records the 2013 reclassification that renamed ophthalmoplegic migraine to RPON.

PMID:35659705 SUPPORT Human Clinical

"Typical magnetic resonance imaging findings show a focal nerve thickening and contrast enhancement."

Records the imaging signature that separates RPON from aneurysmal and ischaemic third nerve palsy.

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Discussions and Knowledge Gaps

4

How far can the pupil-involving versus pupil-sparing distinction be trusted to separate compressive from ischaemic third nerve palsy?

CONTROVERSY OPEN pupil_rule_exceptions

Attached to

pathophysiology#Preserved Superficial Pupillomotor Function

The anatomical premise is sound and the statistical association is strong: only 2% of aneurysmal palsies spare the pupil, and about three quarters of vasculopathic palsies do spare it. But the rule has documented failure modes in both directions. Pupil sparing occurs in a minority of compressive subarachnoid lesions and in a large proportion of cavernous sinus compressive lesions, and aberrant regeneration can manufacture apparent sparing. Conversely, about half of diabetic microvascular palsies in one large inpatient series did involve the pupil, which the author attributed to coexisting autonomic neuropathy. The rule should therefore be curated as a likelihood modifier, not a decision rule, and it does not transfer to children at all.

Show evidence (3 references)

PMID:6830173 SUPPORT Human Clinical

"Two case reports and a review of the literature disclose that pupil sparing occurs in a small proportion of intraaxial and compressive subarachnoid oculomotor nerve lesions and in a large proportion of compressive cavernous sinus oculomotor nerve lesions."

Documents the compressive lesions that nevertheless spare the pupil, the first failure mode of the rule.

PMID:21059515 SUPPORT Human Clinical

"Of 234 patients with diabetes, microvascular ischemia was the cause of TNP in only two-thirds (five had aneurysms) and 53% of those with diabetic microvascular ischemia had pupillary involvement-often bilateral, suggesting concomitant autonomic neuropathy."

Documents the opposite failure mode - microvascular palsy that does involve the pupil - in a majority of diabetic cases in this inpatient series.

PMID:16391633 SUPPORT Human Clinical

"Their pupillary signs, unlike those of adults, are not helpful in differentiating compressive etiologies from other causes."

Establishes that the rule does not apply in paediatric practice at all.

Can the spatial pattern of extraocular muscle weakness discriminate vasculopathic from aneurysmal palsy when the pupil is uninformative?

EMERGING HYPOTHESIS OPEN pattern_of_motor_paresis_as_a_second_axis

Attached to

pathophysiology#Somatic Motor Fibre Conduction Failure

If the pupil rule fails in exactly the cases where it is most needed, a second discriminator would be valuable. One series proposed that incomplete pupil-sparing vasculopathic palsies show diffuse weakness across all cranial nerve III muscles, whereas pupil-sparing aneurysmal palsies show focal weakness confined to some of them. The proposal follows naturally from the mechanism - diffuse endoneurial ischaemia versus focal external contact - but the authors were explicit that it needs confirmation, and no larger validation has been curated here.

Show evidence (1 reference)

PMID:11756854 SUPPORT Human Clinical

"We propose that distinguishing these two patterns of EOM paresis may be helpful in differentiating between vasculopathic and aneurysmal 3NP. Future studies will be needed to confirm the clinical utility of this hypothesis."

The authors state the hypothesis and its unvalidated status in their own words, which is why this is curated as EMERGING_HYPOTHESIS rather than as mechanism.

What is the primary lesion in recurrent painful ophthalmoplegic neuropathy - ischaemia, inflammation, demyelination, or compression?

KNOWLEDGE GAP OPEN rpon_mechanism_unresolved

Attached to

pathophysiology#Focal Oculomotor Nerve Inflammation with Blood-Nerve Barrier Breakdown

RPON was renamed away from "ophthalmoplegic migraine" precisely because the MRI appearance indicates a neuropathy, but the rename did not settle what causes the neuropathy. Competing hypotheses of nerve compression, ischaemia, and inflammation or demyelination are all still live, no histology is available, and treatment with corticosteroids has never been tested against the natural history of spontaneous remission. Because attacks are rare (5/633 in a large aetiological series) the gap is unlikely to close without a multicentre registry.

Proposed experiments

Prospective multicentre RPON registry with standardised acute imaging

rpon_prospective_registry

Enrol consecutive RPON attacks across centres with a fixed acute MRI protocol covering the cisternal nerve and root entry zone, repeated in remission, to establish whether enhancement resolves completely and whether it precedes or follows the ophthalmoplegia.

Show evidence (2 references)

PMID:36694449 SUPPORT Human Clinical

"Several hypotheses have been proposed, including nerve compression, ischemia or inflammation/demyelination, but none has been completely accepted."

States directly that no mechanism for RPON is established.

PMID:35659705 SUPPORT Human Clinical

"There is no evidence supporting a specific treatment."

Confirms the therapeutic corollary of the mechanistic gap.

Should congenital fibrosis of the extraocular muscles and the other congenital cranial dysinnervation disorders be curated inside this entry?

INTERPRETATION RESOLVED scope_boundary_congenital_dysinnervation

Attached to

pathophysiology#Congenital Oculomotor Nerve Hypoplasia or Aplasia

They should not. CFEOM (KIF21A, TUBB3, TUBA1A, PHOX2A) and the wider CCDD group are distinct, separately named genetic entities with their own MONDO identifiers, and the large aetiological series that anchors this entry explicitly excluded congenital cranial dysinnervation disorders when assigning its congenital category. The congenital subtype curated here is isolated congenital oculomotor nerve palsy with imaging-demonstrated nerve hypoplasia, thinning, or agenesis. The distinction is recorded because a deep-research report generated for this entry did bundle CFEOM genetics into it, and that content was deliberately not imported.

Resolution: Scope fixed to acquired and isolated congenital oculomotor nerve palsy; CFEOM and CCDD genetics excluded and left to their own entries.

Show evidence (1 reference)

PMID:38411317 SUPPORT Human Clinical

"Congenital oculomotor nerve palsy was diagnosed when the patients had an infantile onset of ophthalmoplegia after excluding congenital cranial dysinnervation disorders, such as Duane syndrome and congenital Horner syndrome"

The anchoring series states its own exclusion of congenital cranial dysinnervation disorders, which is the boundary this entry adopts.

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Pathophysiology

11

Somatotopic Segregation of Pupillomotor and Somatic Motor Fibres

Cranial nerve III carries two functionally distinct fibre populations that are not intermingled. The preganglionic parasympathetic pupillomotor and accommodative fibres travel superficially, at the periphery of the nerve; the somatic motor fibres to levator palpebrae superioris and the four extraocular muscles travel deeper. This anatomical arrangement is the single fact from which the entire pupil-involving versus pupil-sparing clinical axis follows: an insult applied from outside the nerve reaches the superficial fibres first, whereas an insult arising within the nerve's substance reaches the deeper fibres first. Nothing about the fibres themselves confers differential vulnerability - it is their position.

peripheral nervous system neuron CL:2000032

oculomotor nerve UBERON:0001643

Downstream

Extrinsic Compression of the Cisternal Oculomotor Nerve Because the pupillomotor fibres lie at the surface, an extrinsic mass contacts them before it reaches the motor core.

Endoneurial Microvascular Ischaemia of the Oculomotor Nerve Core Because the somatic motor fibres occupy the core, an ischaemic insult to the nerve's internal blood supply damages them while the superficially placed pupillomotor fibres are relatively protected.

Show evidence (3 references)

PMID:30252368 SUPPORT Other

"Parasympathetic fibers, located superficially, innervate the ciliary muscle and sphincter pupillae, mediating lens accommodation and pupillary constriction."

Directly states the superficial peripheral position of the pupillomotor parasympathetic fibres, the anatomical premise of this entry. Classified OTHER because this is a reference-work synthesis of established human neuroanatomy rather than a study reporting its own data.

PMID:30252368 SUPPORT Other

"Somatic motor fibers, located deeper, innervate the levator palpebrae superioris, which elevates the upper eyelid, and 4 extraocular muscles"

States the complementary deeper position of the somatic motor fibres, completing the segregation on which the pupil axis depends. Classified OTHER for the same reason as the companion quote.

PMID:36116851 SUPPORT Other

"It also has parasympathetic pre-ganglionic fibers, responsible for the innervation of sphincter pupillae and ciliary muscles."

Independent anatomical review confirming that the nerve carries a preganglionic parasympathetic component serving the pupil and lens, alongside its motor component.

Extrinsic Compression of the Cisternal Oculomotor Nerve

A posterior communicating artery aneurysm, tumour, or herniating uncus presses on the nerve in the subarachnoid space between the midbrain and the cavernous sinus. Mass effect is transmitted from the outside inwards, so the superficial pupillomotor fibres bear the injury first and most heavily. The same compression usually produces pain, and in the aneurysmal case it signals a lesion that may be about to rupture.

peripheral nervous system neuron CL:2000032 Schwann cell CL:0002573

response to mechanical stimulus GO:0009612

oculomotor nerve UBERON:0001643 subarachnoid space UBERON:0000315

Downstream

Superficial Pupillomotor Fibre Injury External pressure damages the peripherally placed parasympathetic fibres, producing pupil involvement in almost all aneurysmal palsies.

Somatic Motor Fibre Conduction Failure Continued or severe compression penetrates to the deeper motor fibres, adding ptosis and ophthalmoplegia to the pupillary sign.

Aberrant Regeneration of the Oculomotor Nerve Severe compressive injury that transects axons is followed, weeks to months later, by misdirected regrowth. Aberrant regeneration therefore marks a structural lesion and is not seen after purely ischaemic palsy.

Show evidence (3 references)

PMID:30252368 SUPPORT Human Clinical

"Etiologies range from benign microvascular ischemia to compressive intracranial lesions, including aneurysms, making prompt recognition and appropriate evaluation critical, particularly in cases presenting with pupillary dysfunction."

Ties compressive aetiology to pupillary dysfunction and to the clinical urgency that follows from it.

PMID:39692993 SUPPORT Human Clinical

"Due to anatomical proximity, aneurysmal mass effect has been identified as the most prevalent ONP etiology and often leads to rupture"

Identifies mass effect from an adjacent aneurysm as the operative mechanism and links it to rupture risk.

PMID:21059515 SUPPORT Human Clinical

"Third nerve damage occurred in the subarachnoid space in 32%, the cavernous sinus in 23%, the brainstem in 14%, as a nonlocalized peripheral neuropathy in 18% and at an uncertain location in 13%."

The subarachnoid segment, where the nerve is exposed to aneurysms and herniation, is the most frequently damaged site.

Transtentorial Herniation Compressing Cranial Nerve III

When rising intracranial pressure displaces the uncus through the tentorial incisura, cranial nerve III is one of the structures trapped in that aperture. The resulting ipsilateral third nerve palsy, classically beginning as a dilating pupil, is a bedside marker of a life-threatening intracranial emergency rather than an isolated ocular motor problem.

oculomotor nerve UBERON:0001643 cerebral peduncle UBERON:0002623

Downstream

Superficial Pupillomotor Fibre Injury Herniation compresses the nerve from outside, so the pupil dilates first, which is why the "blown pupil" is watched for in raised intracranial pressure.

Show evidence (2 references)

PMID:30725793 SUPPORT Human Clinical

"Clinically, an uncal herniation is characterized by a predictable pattern of neuroanatomic compression, including ipsilateral third nerve palsy, contralateral motor deficits from compression of the cerebral peduncle, and progressive brainstem dysfunction."

Establishes ipsilateral third nerve palsy as a defining component of the uncal herniation syndrome.

PMID:30725793 SUPPORT Human Clinical

"Critical neurovascular structures traverse this confined aperture, including the midbrain, cranial nerve III, the posterior cerebral arteries, and the superior cerebellar arteries."

Gives the anatomical reason the third nerve is compressed during herniation: it passes through the tentorial notch.

Endoneurial Microvascular Ischaemia of the Oculomotor Nerve Core

In diabetes, hypertension, dyslipidaemia, and smoking, small-vessel disease of the nerve's own blood supply produces ischaemic injury concentrated in the nerve's interior. Because the somatic motor fibres occupy that interior while the pupillomotor fibres lie superficially, the resulting palsy is typically diffuse across all cranial nerve III muscles yet leaves the pupil working - the pupil-sparing pattern. Sparing is a statistical tendency produced by geometry, not a guarantee.

peripheral nervous system neuron CL:2000032 Schwann cell CL:0002573

response to ischemia GO:0002931

oculomotor nerve UBERON:0001643

Downstream

Preserved Superficial Pupillomotor Function Ischaemia of the nerve core leaves the peripherally placed parasympathetic fibres largely intact, which is the mechanistic content of "pupil-sparing".

Somatic Motor Fibre Conduction Failure Core ischaemia damages the somatic motor fibres, and when the palsy is incomplete the weakness is characteristically diffuse across all the muscles of cranial nerve III rather than focal.

Show evidence (2 references)

PMID:39510537 SUPPORT Human Clinical

"Ocular motor mononeuropathies affect cranial nerves III, IV and VI and are more frequent in diabetes mellitus, with oculomotor nerve involvement being predominant."

Establishes the vascular-risk-factor setting and the predominance of cranial nerve III among the ocular motor mononeuropathies.

PMID:11756854 SUPPORT Human Clinical

"Of 55 patients with vasculopathic 3NP, 42 (76%) had normal pupillary function."

Quantifies pupil sparing in a consecutive vasculopathic third nerve palsy series.

Superficial Pupillomotor Fibre Injury

Damage to the peripherally placed preganglionic parasympathetic fibres interrupts the efferent limb of the pupillary light reflex and of accommodation. The iris sphincter and ciliary muscle lose their excitatory drive, so the pupil dilates and stops constricting to light. This is internal ophthalmoplegia, the pupil-involving pattern.

smooth muscle cell of sphincter of pupil CL:0002243 ciliary muscle cell CL:1000443

smooth muscle contraction GO:0006939 ↓ DECREASED

iris UBERON:0001769 ciliary body UBERON:0001775

Downstream

Mydriasis

Anisocoria

Show evidence (2 references)

PMID:30252368 SUPPORT Other

"Parasympathetic fibers, located superficially, innervate the ciliary muscle and sphincter pupillae, mediating lens accommodation and pupillary constriction."

Identifies the effector targets whose denervation produces mydriasis and loss of accommodation when these fibres are injured.

PMID:21059515 SUPPORT Human Clinical

"Only 2% of aneurysms spared the pupil."

Shows that the compressive aetiologies which reach these superficial fibres almost always produce pupil involvement.

Preserved Superficial Pupillomotor Function

The counterpart node to pupillomotor injury: when the insult originates inside the nerve rather than outside it, the superficial parasympathetic fibres continue to conduct, the pupil reacts normally to light, and the palsy is described as pupil-sparing. Curated as a positive mechanistic state, not as the mere absence of a finding, because it is the observable consequence of where the insult was applied.

smooth muscle cell of sphincter of pupil CL:0002243

iris UBERON:0001769

Show evidence (2 references)

PMID:11756854 SUPPORT Human Clinical

"Of 55 patients with vasculopathic 3NP, 42 (76%) had normal pupillary function."

Documents normal pupillary function as the majority finding in vasculopathic third nerve palsy.

PMID:39510537 SUPPORT Human Clinical

"Pupillary sparing is a characteristic of third nerve palsy."

Supports pupil sparing as the characteristic pattern in the diabetic microvascular setting.

Somatic Motor Fibre Conduction Failure

Loss of conduction in the deeper somatic motor fibres denervates levator palpebrae superioris and the superior, medial, and inferior recti and the inferior oblique. The eye is left under the unopposed action of the lateral rectus and superior oblique, producing the classic down-and-out position, with ptosis and binocular diplopia. This node is shared by every aetiological subtype - it is the final common motor deficit.

peripheral nervous system neuron CL:2000032

regulation of skeletal muscle contraction GO:0014819 ↓ DECREASED

oculomotor nerve UBERON:0001643

Downstream

Ptosis

Ophthalmoplegia

Diplopia

Show evidence (2 references)

PMID:30252368 SUPPORT Human Clinical

"Typical presentation includes ptosis, ophthalmoplegia, diplopia, and variable pupillary involvement, resulting in the characteristic down-and-out eye position in complete palsy."

Directly describes the motor deficit and resulting eye position produced by somatic fibre failure.

PMID:36116851 SUPPORT Other

"It is a purely motor nerve responsible for the innervation of all the extraocular muscles, except the superior oblique and lateral rectus muscles."

Specifies which muscles are denervated, and by exclusion which two remain active to produce the down-and-out position.

Traumatic Stretch Injury of the Oculomotor Nerve at Fixed Tether Points

Head injury displaces the brain relative to the skull base while the nerve remains anchored where it passes the posterior petroclinoid ligament and the tentorial edge. The nerve is stretched or contused at those tether points. Because the injury is a longitudinal stretch rather than a focal external mass, it does not respect the superficial-to-deep gradient in the way compression does, and pupil-sparing traumatic palsies are described.

response to mechanical stimulus GO:0009612

oculomotor nerve UBERON:0001643

Downstream

Somatic Motor Fibre Conduction Failure

Aberrant Regeneration of the Oculomotor Nerve Traumatic axonal disruption, like compression, is followed by regrowth that can reach the wrong target, so synkinesis after head injury is a late marker of the severity of the original axonal injury.

Show evidence (2 references)

PMID:16978866 SUPPORT Human Clinical

"The suggested mechanism of the oculomotor nerve palsy with pupil sparing in this case is stretching of the oculomotor nerve at the posterior petroclinoid ligament, maintaining an intact pupillomotor nerve."

Gives the stretch-at-a-tether-point mechanism together with the observation that the pupillomotor fibres can survive it. Marked PROVISIONAL because this is a single imaged case with an author-proposed mechanism.

PMID:16978866 SUPPORT Human Clinical

"Oculomotor nerve palsy without internal ophthalmoplegia (pupil sparing) is extremely rare."

Qualifies the mechanism: pupil sparing after trauma is possible but uncommon, so a traumatic palsy is not assumed to spare the pupil.

Congenital Oculomotor Nerve Hypoplasia or Aplasia

In congenital palsy the nerve itself is maldeveloped rather than injured. High-resolution MRI shows thinning of the nerve along its whole course, thinning confined to its distal segment, or complete agenesis, with secondary atrophy of the extraocular muscles that the missing fibres would have supplied. The deficit is therefore a developmental one, present before any pupil-involving-versus-sparing logic applies, and in children pupillary signs lose their localizing value altogether.

oculomotor nerve development GO:0021557 ↓ DECREASED

oculomotor nerve UBERON:0001643

Downstream

Somatic Motor Fibre Conduction Failure

Amblyopia A congenital palsy during the amblyogenic period leaves the affected eye misaligned and often ptotic, so it is deprived of a clear, aligned image and fails to develop normal acuity.

Show evidence (3 references)

PMID:36580093 SUPPORT Human Clinical

"One patient had complete nerve agenesis, two patients showed a diffuse thinning of the nerve, from the brainstem to the orbit and 3 patients showed a distal thinning of the oculomotor nerve, starting at the level of the cavernous sinus."

Documents the spectrum of structural nerve maldevelopment underlying congenital third nerve palsy.

PMID:30997520 SUPPORT Human Clinical

"On MR imaging, 5 patients (36%) had hypoplasia or aplasia of the oculomotor nerve with variable degrees of extraocular muscle atrophy on the affected side."

Independent series confirming nerve hypoplasia or aplasia with corresponding muscle atrophy in about a third of congenital cases.

PMID:16391633 SUPPORT Human Clinical

"Their pupillary signs, unlike those of adults, are not helpful in differentiating compressive etiologies from other causes."

Establishes the important caveat that the pupil axis central to this entry does not transfer to paediatric practice.

Focal Oculomotor Nerve Inflammation with Blood-Nerve Barrier Breakdown

The proposed mechanism of recurrent painful ophthalmoplegic neuropathy. Attacks are accompanied by focal thickening and gadolinium enhancement of the cisternal nerve or its root entry zone, which indicates local breakdown of the blood-nerve barrier. Whether the primary event is ischaemic, inflammatory, demyelinating, or compressive is unresolved, and this node is curated as hypothetical for that reason.

neuroinflammatory response GO:0150076

oculomotor nerve UBERON:0001643

Downstream

Somatic Motor Fibre Conduction Failure

Headache

Show evidence (3 references)

PMID:35659705 SUPPORT Human Clinical

"Typical magnetic resonance imaging findings show a focal nerve thickening and contrast enhancement."

Documents the imaging correlate that motivates a focal blood-nerve barrier mechanism.

PMID:24567117 SUPPORT Human Clinical

"The authors suggest that ischemic reversible breakdown of the blood-nerve barrier is the most probable cause of OM and to include MR findings in the hallmarks of the disease."

States the blood-nerve barrier hypothesis explicitly, as the authors' preferred but not established explanation.

PMID:36694449 SUPPORT Human Clinical

"Several hypotheses have been proposed, including nerve compression, ischemia or inflammation/demyelination, but none has been completely accepted."

Confirms that no mechanism for RPON is established, which is why this node carries HYPOTHETICAL confidence.

Aberrant Regeneration of the Oculomotor Nerve

After severe axonal injury, regrowing fibres can reach the wrong target, so attempted adduction or downgaze elevates the eyelid or constricts the pupil. Clinically this matters twice over: it is a marker of structural (usually compressive or traumatic) rather than ischaemic injury, and a misdirected pupillomotor fibre can make an involved pupil look normal at rest, producing apparent pupil sparing.

peripheral nervous system neuron CL:2000032 Schwann cell CL:0002573

oculomotor nerve UBERON:0001643

Downstream

Preserved Superficial Pupillomotor Function This is the counterexample to the entry's central axis. A pupillomotor fibre that regrows into a somatic motor pathway can hold the pupil at near-normal size at rest, so a genuinely pupil-involving structural palsy is misread as pupil-sparing. The sparing here is apparent, not true, and it is produced by the repair process rather than by the site of the original insult.

Show evidence (2 references)

PMID:16391633 SUPPORT Human Clinical

"Primary aberrant regeneration was the presenting sign in a child with neurofibromatosis type 2."

Documents aberrant regeneration occurring in a structural (neoplastic) third nerve lesion. Marked PROVISIONAL because the supporting observation here is a single case within a small cohort.

PMID:6830173 SUPPORT Human Clinical

"Careful examination is also necessary to separate examples of apparent pupil sparing in cases of aberrant regeneration and in some instances of cavernous sinus compression."

Establishes aberrant regeneration as a source of apparent, rather than true, pupil sparing, which is the reason this node bears on the entry's central axis.

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Pathograph

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

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Phenotypes

10

Eye 2

Ptosis HP:0000508

Show evidence (1 reference)

PMID:30592440 SUPPORT Human Clinical

"Oculomotor nerve palsy (ONP) is an important and common clinical diagnosis. Its main features are diplopia and ptosis."

Establishes ptosis as one of the two cardinal features of the syndrome.

Diplopia HP:0000651

Show evidence (1 reference)

PMID:30592440 SUPPORT Human Clinical

"Oculomotor nerve palsy (ONP) is an important and common clinical diagnosis. Its main features are diplopia and ptosis."

Establishes diplopia as the other cardinal feature alongside ptosis.

Nervous System 1

Headache HP:0002315

Show evidence (2 references)

PMID:21059515 SUPPORT Human Clinical

"painful onset occurred with 94% of aneurysm and 69% of diabetic cases."

Quantifies painful onset in both the compressive and the microvascular subtypes.

PMID:26021754 SUPPORT Human Clinical

"Ophthalmoplegic migraine (OM)/recurrent painful ophthalmoplegic neuropathy (RPON) is a rare disease consisting of recurrent unilateral headache accompanied or followed by ipsilateral ophthalmoplegia."

Supports headache as a defining component of the RPON attack.

Other 7

Ophthalmoplegia HP:0000602

Show evidence (1 reference)

PMID:30252368 SUPPORT Human Clinical

"Typical presentation includes ptosis, ophthalmoplegia, diplopia, and variable pupillary involvement, resulting in the characteristic down-and-out eye position in complete palsy."

Names ophthalmoplegia and the down-and-out position as the typical motor presentation.

Mydriasis HP:0011499

Show evidence (2 references)

PMID:39692993 SUPPORT Human Clinical

"Complete ONP diagnosis is established when the simultaneous occurrence of ptosis, fixed mydriasis, diplopia, and ophthalmoplegia is observed."

Records fixed mydriasis as a defining component of complete aneurysmal third nerve palsy.

PMID:21059515 SUPPORT Human Clinical

"Only 2% of aneurysms spared the pupil."

Shows how nearly universal pupil involvement is when the cause is an aneurysm.

Anisocoria HP:0009916

Show evidence (1 reference)

PMID:30725793 SUPPORT Human Clinical

"Jonathan Hutchinson first described unilateral pupillary dilation (Hutchinson pupil), initially attributed to midbrain involvement."

The eponymous unilateral pupillary dilation of herniation is an anisocoria arising from third nerve compression.

Abnormal pupillary light reflex HP:0007695

Show evidence (1 reference)

PMID:30252368 SUPPORT Other

"Parasympathetic fibers, located superficially, innervate the ciliary muscle and sphincter pupillae, mediating lens accommodation and pupillary constriction."

Identifies the efferent pathway whose interruption abolishes light-evoked pupillary constriction.

Exotropia HP:0000577

Show evidence (1 reference)

PMID:30252368 SUPPORT Human Clinical

"Typical presentation includes ptosis, ophthalmoplegia, diplopia, and variable pupillary involvement, resulting in the characteristic down-and-out eye position in complete palsy."

The down-and-out position is an exotropia combined with a hypotropia.

Amblyopia HP:0000646

Show evidence (1 reference)

PMID:16391633 SUPPORT Human Clinical

"Amblyopia developed in 7 (39%) children and was successfully treated in 5 of the 7 (71%)."

Quantifies amblyopia in a paediatric third nerve palsy cohort and its response to occlusion therapy.

Posterior communicating artery aneurysm HP:0031773

Show evidence (1 reference)

PMID:33845117 SUPPORT Human Clinical

"Posterior communicating artery aneurysms (PCoAA) usually present with brain hemorrhage, but they might present with oculomotor nerve palsy (ONP) in about one out of five patients."

Directly links the aneurysm to third nerve palsy as a presenting syndrome and quantifies how often.

💊

Medical Actions

7

Microsurgical Clipping of a Posterior Communicating Artery Aneurysm

Action: neurosurgical procedure Ontology label: Neurosurgical Procedure NCIT:C15656

Open neurosurgical clipping of the aneurysm removes the mass compressing the cisternal nerve. Because the mechanism of injury is mass effect, relieving it early is what gives the nerve a chance to recover, and clipping produces faster recovery than endovascular treatment in the first year even though long-term rates converge.

Mechanism Target:

INHIBITS Extrinsic Compression of the Cisternal Oculomotor Nerve — Clipping excludes the aneurysm from the circulation and decompresses the nerve, acting directly on the compressive node.

Show evidence (1 reference)

PMID:33845117 SUPPORT Human Clinical

"Surgical clipping is superior to endovascular coiling in terms of complete recovery among patients with ONP due to PCoAAs."

Supports clipping as acting on the compressive mechanism with better complete-recovery outcomes.

Show evidence (2 references)

PMID:39692993 SUPPORT Human Clinical

"Overall, microsurgical clipping of PComA aneurysms demonstrated a significantly higher likelihood of ONP recovery compared to EVT at 1,3,6, and 12 months follow-up."

Meta-analytic support for earlier nerve recovery after clipping than after endovascular treatment.

PMID:39692993 SUPPORT Human Clinical

"Our findings suggest microsurgery leads to prompt ONP recovery from PComA aneurysms, while EVT shows potential for delayed favorable recovery; both treatments yield short-term recovery when administered early."

Qualifies the advantage as one of speed rather than of ultimate outcome, so the entry does not overstate clipping's superiority.

Endovascular Coiling of a Posterior Communicating Artery Aneurysm

Action: embolization therapy Ontology label: Embolization Therapy NCIT:C15230

Endovascular occlusion of the aneurysm sac secures the lesion against rupture and, less directly than clipping, reduces the pulsatile mass effect on the nerve. Nerve recovery is slower than after clipping but comparable by 18 to 24 months, and older patients may do relatively better with it.

Mechanism Target:

INHIBITS Extrinsic Compression of the Cisternal Oculomotor Nerve — Coil occlusion removes the pulsatile haemodynamic stress transmitted to the adjacent nerve, though it leaves the aneurysm sac in place.

Show evidence (1 reference)

PMID:39692993 SUPPORT Human Clinical

"However, recent literature has reported favorable ONP recovery outcomes after endovascular treatment (EVT) suggesting other mechanisms associated with ONP occurrence, such as the pulsatile hemodynamic stress (water hammer effect) of cerebral aneurysms"

Supports pulsatile haemodynamic stress, not sac volume alone, as part of the compressive mechanism that endovascular treatment addresses.

Show evidence (1 reference)

PMID:30455133 SUPPORT Human Clinical

"In addition, the aneurysm treatment modality was not correlated with nerve recovery in either analysis."

A single-centre series in which modality did not predict recovery, tempering the meta-analytic preference for clipping.

Vascular Risk Factor Management in Microvascular Palsy

Action: therapeutic procedure Ontology label: Therapeutic Procedure NCIT:C49236

There is no treatment directed at the ischaemic nerve itself. Management is optimisation of glycaemic control and of the other vascular risk factors, plus observation, since the natural history is spontaneous recovery.

Mechanism Target:

MODULATES Endoneurial Microvascular Ischaemia of the Oculomotor Nerve Core — Risk factor control acts on the small-vessel disease upstream of endoneurial ischaemia rather than on the nerve injury already sustained.

Show evidence (1 reference)

PMID:39510537 SUPPORT Human Clinical

"Treatment includes optimised glycaemic control and management of vascular risk factors."

States the management approach directed at the microvascular mechanism.

Show evidence (1 reference)

PMID:39510537 SUPPORT Human Clinical

"Spontaneous recovery is seen in many cases."

Supports observation as reasonable management because the natural history is favourable.

Botulinum Toxin Injection for Acute Ocular Misalignment

Action: Pharmacotherapy NCIT:C15986

Agent: botulinum toxin type A CHEBI:3160

Chemodenervation of the antagonist muscle reduces the deviation and the diplopia during the acute phase. It is symptomatic: it does not act on the nerve lesion, and its benefit over expectant management is confined to acute palsy.

Target Phenotypes: Diplopia HP:0000651

Show evidence (2 references)

PMID:38112391 SUPPORT Human Clinical

"The overall treatment success rate in acute and chronic nerve palsy was 79% and 33%, respectively."

Quantifies the sharp difference in benefit between acute and chronic palsy.

PMID:38112391 SUPPORT Human Clinical

"Botulinum toxin can be used for the treatment of acute third, fourth, and sixth nerve palsy, especially in patients with acute palsy and more severe tropia."

Supports use restricted to the acute setting; the meta-analysis pools third, fourth, and sixth nerve palsy rather than isolating cranial nerve III.

Strabismus and Ptosis Surgery for Residual Deficit

Action: surgical procedure Ontology label: Surgical Procedure NCIT:C15329

Once recovery has plateaued, surgery addresses the mechanical consequences rather than the nerve: muscle shortening or lengthening, transposition, globe fixation, and ptosis repair, usually in combination. The aim is alignment, field of single vision, and appearance, not reinnervation.

Target Phenotypes: Ptosis HP:0000508 Exotropia HP:0000577 Diplopia HP:0000651

Show evidence (2 references)

PMID:38303488 SUPPORT Human Clinical

"These included: muscle shortening and lengthening procedures, muscle transposition, globe fixation and ptosis surgery."

Enumerates the surgical techniques used for residual third nerve palsy.

PMID:38303488 SUPPORT Human Clinical

"Strabismus surgery for OMN palsy can be approached through a variety of different techniques to improve the quality of life, independence and aesthetics for the patient."

States the goals of surgery as functional and aesthetic rehabilitation rather than nerve recovery.

High-Dose Corticosteroid Therapy for Inflammatory Palsy

Action: systemic corticosteroid therapy Ontology label: Systemic Corticosteroid Therapy NCIT:C122080

In Tolosa-Hunt syndrome and other steroid-responsive inflammatory third nerve palsies, high-dose corticosteroids shorten the symptomatic episode and the total treatment course. The prognosis is favourable but recurrence during or after tapering is common, so response is not the same as cure.

Show evidence (2 references)

PMID:37853245 SUPPORT Human Clinical

"High-dose corticosteroids can be an effective initial treatment and reduce the total treatment duration."

Supports high-dose corticosteroids as effective initial therapy for the prototypical inflammatory cause.

PMID:37853245 SUPPORT Human Clinical

"Recurrence occurred during steroid tapering as part of the initial treatment in seven, while in 18 patients, it happened after the successful termination of the initial treatment."

Qualifies the benefit: a quarter of patients recurred, so steroid responsiveness does not amount to durable cure.

Amblyopia Therapy in Childhood Palsy

Action: therapeutic procedure Ontology label: Therapeutic Procedure NCIT:C49236

In children within the amblyogenic period, occlusion therapy for the sound eye protects visual development, which is a different and often more consequential target than the ocular motor deficit itself.

Target Phenotypes: Amblyopia HP:0000646

Show evidence (1 reference)

PMID:16391633 SUPPORT Human Clinical

"Good visual acuity was obtained in children within the amblyogenic age group with appropriate occlusion therapy."

Supports occlusion therapy as effective for the amblyopia that complicates childhood third nerve palsy.

🌍

Environmental Factors

2

Tobacco smoking

Smoking is one of the vascular risk factors whose presence is required by the operational definition of microvascular oculomotor nerve palsy, acting through small-vessel disease of the nerve's own blood supply rather than through any nerve-specific toxicity.

Show evidence (1 reference)

PMID:38411317 SUPPORT Human Clinical

"The predilection for men in microvascular etiology may be related to a higher prevalence of vascular risk factors such as diabetes, hypertension and smoking in men in the Republic of Korea"

Names smoking among the vascular risk factors the anchoring cohort ties to the microvascular aetiology, which is what makes it a relevant exposure for this disease rather than a general health risk.

Mechanism Target:

PREDISPOSES Endoneurial Microvascular Ischaemia of the Oculomotor Nerve Core — Smoking predisposes to the endoneurial small-vessel disease that produces ischaemic injury to the core of the nerve; it is not itself the injury.

Show evidence (1 reference)

PMID:38411317 SUPPORT Human Clinical

"with at least one vascular risk factor (hypertension, diabetes mellitus, dyslipidemia or smoking)"

Smoking is one of the vascular risk factors the anchoring cohort required before assigning a microvascular aetiology.

Head trauma

Deliberately left without an exposure_term. ECTO was searched for a head injury, traumatic brain injury, and physical trauma exposure concept and has none; per the dismech-terms rule that no term beats a bad one, no loosely related CURIE was substituted.

Blunt head injury, typically from road traffic collision or fall, displaces the brain relative to the skull base and stretches the nerve where it is tethered. This is the initiating exposure of the traumatic subtype and the leading cause in inpatient and paediatric series.

Show evidence (1 reference)

PMID:38411317 SUPPORT Human Clinical

"Even though microvascular, traumatic and intracranial aneurysms are the most common causes of oculomotor nerve palsy"

Establishes trauma as one of the most common causes of oculomotor nerve palsy, which is the disease-level claim this exposure entry makes.

Mechanism Target:

TRIGGERS Traumatic Stretch Injury of the Oculomotor Nerve at Fixed Tether Points — Head trauma is the direct initiating event of the stretch injury; the palsy is dated from it.

Show evidence (1 reference)

PMID:38411317 SUPPORT Human Clinical

"A traumatic cause was defined when there was a documented onset of oculomotor nerve palsy following head trauma and no other disorders to explain the oculomotor nerve palsy better."

States the temporal head-trauma-then-palsy relation that makes this exposure the trigger of the traumatic mechanism.

🔬

Diagnosis

1

MRI of the oculomotor nerve with vascular imaging

Because the syndrome is defined by the affected nerve rather than by a single lesion, imaging is what assigns the aetiological subtype. MRI evaluates the nerve along its course from midbrain to orbit; vascular imaging is directed at the aneurysm that must not be missed. In children, where pupillary signs carry no localizing value, imaging is not optional.

Show evidence (2 references)

PMID:36116851 SUPPORT Other

"Magnetic resonance imaging (MRI) is the best imaging exam to evaluate patients with clinical signs of third cranial nerve palsy."

Establishes MRI as the primary imaging modality for evaluating third cranial nerve palsy.

PMID:16391633 SUPPORT Human Clinical

"Children with oculomotor nerve palsy require neuroimaging."

Supports imaging as mandatory in children, where the pupil cannot be used to triage compressive causes.

📈

Progression

6

Acute onset

Microvascular

Microvascular palsy begins abruptly, often with periorbital pain, and reaches its deficit over hours to days.

Show evidence (1 reference)

PMID:39510537 SUPPORT Human Clinical

"Clinical manifestations often include ptosis, diplopia, and periorbital pain."

Records the acute symptom triad with which diabetic ocular motor mononeuropathy presents.

Spontaneous recovery

Microvascular

The defining prognostic feature of the microvascular subtype is spontaneous resolution, typically within weeks to a few months, without directed treatment of the nerve itself.

Show evidence (1 reference)

PMID:39510537 SUPPORT Human Clinical

"Spontaneous recovery is seen in many cases."

Supports spontaneous recovery as the expected course of diabetic ocular motor mononeuropathy.

Post-treatment recovery

Compressive

After treatment of a posterior communicating artery aneurysm, recovery of the nerve depends chiefly on how severe the palsy was and how long it was left untreated, which is the mechanistic argument for early intervention.

Show evidence (1 reference)

PMID:30455133 SUPPORT Human Clinical

"initial palsy severity and preoperative palsy times are important predictors for ONP recovery, early treatment is recommended to achieve complete recovery of ONP, regardless of the presence or absence of SAH"

Identifies severity and delay as the determinants of nerve recovery after aneurysm treatment.

Attack and remission cycle

RPON

RPON runs as discrete attacks with full recovery between them in most patients, although repeated attacks can leave permanent deficit.

Show evidence (1 reference)

PMID:35659705 SUPPORT Human Clinical

"In the majority of cases, there is a full recovery within days or weeks."

Supports the relapsing-remitting course with usual full recovery that characterizes RPON.

Prognostic determinants of recovery

Across aetiologies, the two factors that predict good long-term recovery are a short symptom onset (under one week) and involvement of the third nerve alone rather than several cranial nerves. Recovery also differs sharply by cause, being best for inflammatory and worst for compressive palsies in one tertiary series.

Show evidence (2 references)

PMID:38352051 SUPPORT Human Clinical

"The onset of symptoms in less than 1 week and isolated nerve involvement were associated with better prognosis in subjects with third, fourth, and sixth cranial nerve palsy."

Identifies the two independent prognostic factors for recovery, adjusted for age, sex, and vascular risk factors.

PMID:38352051 SUPPORT Human Clinical

"Our study revealed that ischemic and compressive lesions were the most common etiology of oculomotor nerve palsy, comprising 24.6% each."

Independent tertiary-hospital series confirming ischaemic and compressive causes as the two dominant aetiologies of third nerve palsy.

Amblyopia risk in childhood

Congenital

In children the palsy competes with visual development, so the clinically dominant late outcome is amblyopia and loss of binocularity rather than the ocular motor deficit itself.

Show evidence (1 reference)

PMID:16391633 SUPPORT Human Clinical

"Amblyopia developed in 7 (39%) children and was successfully treated in 5 of the 7 (71%)."

Quantifies amblyopia as a frequent and largely treatable sequela of childhood third nerve palsy.

📊

Prevalence

3

Patients with isolated oculomotor nerve palsy, referral-based university hospital, all departments, South Korea

Period Prevalence Unknown Microvascular

Aetiological share, not a population rate: microvascular ischaemia accounted for 168/633 (26.5%) of isolated oculomotor nerve palsy cases ascertained across all departments over 18 years.

Show evidence (1 reference)

PMID:38411317 SUPPORT Human Clinical

"The most common etiology was microvascular (n = 168, 26.5%), followed by vascular anomalies (n = 110, 17.4%), neoplastic (n = 86, 13.6%), inflammatory (n = 79, 12.5%), idiopathic (n = 60, 9.5%) and traumatic (n = 53, 8.4%)."

Direct source for the aetiological fractions recorded here.

Municipal hospital inpatients with third nerve palsy personally examined by a single neuro-ophthalmologist over 37 years

Period Prevalence Unknown Traumatic

Aetiological share in an inpatient population, where severe trauma and herniation are over-represented relative to outpatient neuro-ophthalmology series: trauma 26%, tumour 12%, diabetes 11%, aneurysm 10%.

Show evidence (1 reference)

PMID:21059515 SUPPORT Human Clinical

"Causes were trauma (26%), tumor (12%), diabetes (11%), aneurysm (10%), surgery (10%), stroke (8%), infection (5%), Guillain-Barre and Fisher syndromes (5%), idiopathic cavernous sinusitis (3%), benign self-limited (2%), miscellaneous (4%), and unknown (3%)."

Direct source for the inpatient aetiological distribution, which differs markedly from referral outpatient series.

Korean population

Annual Incidence 3.71 per 100,000 1–9 per 100,000

Population incidence of third cranial nerve palsy reported as 3.71 per 100,000 per year, against 5.73 for trochlear and 4.66 for abducens palsy in the same population. Incidence rises with age, accelerating after 60.

Show evidence (1 reference)

PMID:38352051 SUPPORT Human Clinical

"Recent reports have indicated that the incidence rates of third, fourth, and sixth cranial nerve palsy among the Korean population are 3.71, 5.73, and 4.66 per 100,000 per year, respectively."

Gives the population annual incidence of third nerve palsy alongside the other ocular motor nerves for context.

🌍

Epidemiology

2

Setting dependence of the aetiological mix

The apparent cause distribution of third nerve palsy depends heavily on where patients are ascertained. Inpatient and referral populations differ, and within one hospital the mix differs by the specialty managing the patient, so no single published distribution should be read as the population truth.

Show evidence (2 references)

PMID:38411317 SUPPORT Human Clinical

"The proportion of etiologies of isolated oculomotor nerve palsy may differ according to the specialties involved in the management."

The authors' own conclusion that ascertainment route biases the measured aetiological distribution.

PMID:21059515 SUPPORT Human Clinical

"Bilateral TNPs, multiple cranial neuropathies, and accompanying neurological signs were common among our inpatients, as were causes rare in outpatient settings such as severe trauma, transtentorial herniation, midbrain strokes, and the Guillain-Barre syndrome."

Documents the specific causes enriched in an inpatient setting relative to outpatient neuro-ophthalmology cohorts.

Pain accompanies both the dangerous and the benign cause

Painful onset is common in aneurysmal third nerve palsy but is also common in diabetic microvascular palsy, so pain alone cannot be used to triage urgency.

headache periorbital pain

Show evidence (1 reference)

PMID:21059515 SUPPORT Human Clinical

"painful onset occurred with 94% of aneurysm and 69% of diabetic cases."

Directly quantifies pain in both aneurysmal and diabetic palsy, showing pain does not discriminate between them.

🔀

Differential Diagnoses

1

Conditions with similar clinical presentations that must be differentiated from Oculomotor Nerve Palsy:

Mimics of oculomotor nerve palsy

Overlapping Features Several conditions reproduce parts of the syndrome without a third nerve lesion, and each must be excluded before the diagnosis is assigned: myasthenia gravis (fatiguable ptosis and ophthalmoplegia, pupil always spared), thyroid-associated orbitopathy and orbital myositis (restrictive rather than paralytic), Horner syndrome and Adie tonic pupil (anisocoria of other origin), congenital ptosis, and Duane retraction syndrome.

Distinguishing Features

A true third nerve palsy weakens a defined muscle set while sparing the superior oblique and lateral rectus.
Thyroid-associated orbitopathy and orbital myositis limit movement mechanically rather than by denervation.
Myasthenia gravis fluctuates, is fatiguable, and never dilates the pupil.
Horner syndrome produces a small rather than a large pupil.

Show evidence (1 reference)

PMID:38411317 SUPPORT Human Clinical

"Particular attention was paid to exclude disorders that may mimic oculomotor nerve palsy, such as exotropia, blepharoptosis, congenital ptosis, anisocoria of other causes"

The anchoring cohort enumerates the mimics it excluded, which is the differential this entry adopts.

{ }

Source YAML

click to show

name: Oculomotor Nerve Palsy
creation_date: "2026-08-20T09:00:00Z"
category: Complex
categories:
- Neurological Disease
- Cranial Neuropathy
description: >-
  Oculomotor (third cranial) nerve palsy is paralysis or paresis of cranial
  nerve III, producing ptosis, ophthalmoplegia with a characteristic
  "down-and-out" eye, diplopia, and variable pupillary involvement. It is a
  syndrome with many causes rather than a single disease: microvascular
  ischaemia, compressive vascular anomalies (above all posterior communicating
  artery aneurysm), neoplasia, inflammation, trauma, congenital nerve
  maldevelopment, and recurrent painful ophthalmoplegic neuropathy each reach
  the same final common deficit. The central mechanistic axis of the entry is
  the somatotopic segregation of the nerve's two fibre populations: the
  preganglionic parasympathetic pupillomotor fibres run superficially at the
  periphery of the nerve, whereas the somatic motor fibres run deeper. Extrinsic
  compression injures the superficial fibres early and takes the pupil, while
  ischaemia of the endoneurial core preferentially damages the deeper somatic
  fibres and characteristically spares it. The rule is powerful but not
  absolute, and the exceptions are curated here alongside it.
disease_term:
  preferred_term: oculomotor nerve paralysis
  term:
    id: MONDO:0001309
    label: oculomotor nerve paralysis
synonyms:
- third nerve palsy
- oculomotor palsy
- IIIrd nerve paralysis
- cranial nerve III palsy
parents:
- Neurological Disorder
- Cranial Neuropathy
definitions:
- name: Clinical syndrome definition for oculomotor nerve palsy
  definition_type: CASE_DEFINITION
  description: >-
    Oculomotor nerve palsy is diagnosed from weakness of the extraocular
    muscles supplied by cranial nerve III, with or without ptosis and
    pupillary involvement, after mimics such as myasthenia gravis, thyroid
    orbitopathy, and Horner syndrome have been excluded.
  scope: General clinical framing of third cranial nerve palsy
  evidence:
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical presentation includes ptosis, ophthalmoplegia, diplopia, and variable pupillary involvement, resulting in the characteristic down-and-out eye position in complete palsy."
    explanation: "States the defining clinical constellation of third cranial nerve palsy, including the variable pupil, which is what the case definition has to capture."
  - reference: PMID:30592440
    reference_title: "The aetiologies of the unilateral oculomotor nerve palsy: a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Oculomotor nerve palsy (ONP) is an important and common clinical diagnosis. Its main features are diplopia and ptosis."
    explanation: "Independent review confirming diplopia and ptosis as the cardinal presenting features on which the clinical diagnosis rests."
- name: Anatomical localization definition
  definition_type: CASE_DEFINITION
  description: >-
    A lesion anywhere from the oculomotor nucleus in the midbrain to the
    terminal branches in the orbit can produce the syndrome, so localization
    along the nerve's course is part of the diagnostic definition rather than
    an afterthought.
  scope: Lesion localization along the course of cranial nerve III
  evidence:
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Lesions affecting the cranial nerve III can occur along its entire course, from the oculomotor nucleus in the midbrain to terminal branches in the orbit."
    explanation: "Establishes that the syndrome is defined by the affected nerve rather than by a single anatomical site, which is why localization is part of the workup."
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Third nerve damage occurred in the subarachnoid space in 32%, the cavernous sinus in 23%, the brainstem in 14%, as a nonlocalized peripheral neuropathy in 18% and at an uncertain location in 13%."
    explanation: "Quantifies how lesion site is distributed across the nerve's course in a large personally-examined inpatient series."
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0001309
      label: oculomotor nerve paralysis
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
    mapping_justification: Primary MONDO disease identifier for this entry.
  icd10cm_mappings:
  - term:
      id: ICD10CM:H49.0
      label: Third [oculomotor] nerve palsy
    mapping_predicate: skos:exactMatch
    mapping_source: ICD-10-CM
    mapping_justification: >-
      ICD-10-CM H49.0 is the direct code for third (oculomotor) nerve palsy;
      laterality is expressed in the H49.00-H49.03 children.
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
    evidence:
    - reference: PMID:30592440
      reference_title: "The aetiologies of the unilateral oculomotor nerve palsy: a review of the literature."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A number of different conditions have been reported to cause ONP, such as diabetes mellitus, aneurysm, tumours, painful ophthalmoplegia, pituitary lesions, cavernous sinus lesions, central nervous system infections, and subarachnoid haemorrhage."
      explanation: "The enumerated causes are neurological and neurovascular disorders of the nervous system, supporting placement in the neurologic chapter."
has_subtypes:
- name: Microvascular
  display_name: Ischaemic microvascular oculomotor nerve palsy
  description: >-
    Acute painful third nerve palsy in an adult with vascular risk factors
    (diabetes mellitus, hypertension, dyslipidaemia, smoking), no causative
    lesion on imaging, and spontaneous recovery. Characteristically, though not
    invariably, pupil-sparing. The most common single aetiology in adults.
  evidence:
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common etiology was microvascular (n = 168, 26.5%), followed by vascular anomalies (n = 110, 17.4%), neoplastic (n = 86, 13.6%), inflammatory (n = 79, 12.5%), idiopathic (n = 60, 9.5%) and traumatic (n = 53, 8.4%)."
    explanation: "Establishes microvascular ischaemia as the single largest aetiological category of isolated oculomotor nerve palsy in a 633-patient hospital-wide series."
  - reference: PMID:39510537
    reference_title: "Ocular Motor Mononeuropathies in Diabetes Mellitus: A Brief Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ocular motor mononeuropathies affect cranial nerves III, IV and VI and are more frequent in diabetes mellitus, with oculomotor nerve involvement being predominant."
    explanation: "Supports diabetes mellitus as the paradigmatic vascular risk factor and cranial nerve III as the ocular motor nerve most often affected."
- name: Compressive
  display_name: Compressive and aneurysmal oculomotor nerve palsy
  description: >-
    Third nerve palsy from extrinsic mass effect on the cisternal nerve, most
    urgently by a posterior communicating artery aneurysm, and also by tumour,
    pituitary apoplexy, and uncal herniation. Painful, usually pupil-involving,
    and a neurosurgical emergency because the aneurysm may be about to rupture.
  evidence:
  - reference: PMID:33845117
    reference_title: "Oculomotor nerve palsy due to posterior communicating artery aneurysm: Clipping vs coiling."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Posterior communicating artery aneurysms (PCoAA) usually present with brain hemorrhage, but they might present with oculomotor nerve palsy (ONP) in about one out of five patients."
    explanation: "Quantifies how often a posterior communicating artery aneurysm declares itself through third nerve palsy rather than through haemorrhage."
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Vascular anomalies included intracranial aneurysm (n = 89, 80.9%), dural arteriovenous fistula (n = 10, 9.1%), cavernous malformation (n = 9, 8.2%) and arteriovenous malformation (n = 2, 1.8%)."
    explanation: "Shows that intracranial aneurysm dominates the vascular-anomaly category that is the second most common cause of isolated oculomotor nerve palsy."
- name: Traumatic
  display_name: Traumatic oculomotor nerve palsy
  description: >-
    Third nerve palsy following head injury, from stretch, contusion, or
    avulsion of the nerve, classically where it is tethered against the
    posterior petroclinoid ligament or the tentorial edge. The leading cause in
    childhood inpatient series and a major cause in young adults.
  evidence:
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Causes were trauma (26%), tumor (12%), diabetes (11%), aneurysm (10%), surgery (10%), stroke (8%), infection (5%), Guillain-Barre and Fisher syndromes (5%), idiopathic cavernous sinusitis (3%), benign self-limited (2%), miscellaneous (4%), and unknown (3%)."
    explanation: "In a large municipal inpatient population trauma was the single most common cause, establishing traumatic palsy as a major aetiological subtype."
  - reference: PMID:16978866
    reference_title: "Traumatic oculomotor nerve palsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The suggested mechanism of the oculomotor nerve palsy with pupil sparing in this case is stretching of the oculomotor nerve at the posterior petroclinoid ligament, maintaining an intact pupillomotor nerve."
    explanation: "Describes the stretch-at-a-tether-point mechanism that distinguishes traumatic palsy from compressive and ischaemic palsy."
- name: Congenital
  display_name: Congenital oculomotor nerve palsy
  description: >-
    Third nerve palsy present from infancy, usually unilateral and incomplete,
    associated on high-resolution MRI with hypoplasia, thinning, or frank
    agenesis of the oculomotor nerve and secondary atrophy of the muscles it
    supplies. A developmental nerve deficit, not an acquired lesion, and the
    most frequent presentation of third nerve palsy in childhood.
  evidence:
  - reference: PMID:30997520
    reference_title: "Magnetic Resonance Imaging in 14 Patients with Congenital Oculomotor Nerve Palsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Congenital oculomotor nerve palsy was mostly incomplete and hypoplasia or aplasia of the oculomotor nerve was apparent in one third of patients showing variable degrees of extraocular muscle atrophy, mostly of the medial rectus and inferior rectus muscles."
    explanation: "Establishes the defining structural correlate of the congenital subtype and its usually incomplete clinical expression."
  - reference: PMID:16391633
    reference_title: "Oculomotor nerve palsy in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Congenital-onset oculomotor nerve palsy was the most frequent presentation, followed by traumatic, neoplastic, vascular, and migrainous or para-infectious etiologies."
    explanation: "Supports congenital onset as the leading category in a paediatric cohort, in contrast with the adult aetiological distribution."
- name: Inflammatory
  display_name: Inflammatory oculomotor nerve palsy
  description: >-
    Third nerve palsy from inflammation of the nerve, its fascicle, or the
    cavernous sinus, with Tolosa-Hunt syndrome as the prototype. Diagnosed on
    an enhancing T2-hyperintense lesion affecting the nerve together with
    steroid responsiveness, it is the third largest aetiological category yet
    has the best recovery of any cause. Curated as an aetiological subtype
    because that category is solidly evidenced, even though the mechanism of
    the inflammation itself is not.
  evidence:
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common etiology was microvascular (n = 168, 26.5%), followed by vascular anomalies (n = 110, 17.4%), neoplastic (n = 86, 13.6%), inflammatory (n = 79, 12.5%), idiopathic (n = 60, 9.5%) and traumatic (n = 53, 8.4%)."
    explanation: "Places inflammatory aetiology at 12.5% of 633 cases, ahead of trauma, which is why it earns a subtype."
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "and the symptoms responded to steroid treatments"
    explanation: "Steroid responsiveness is part of how the anchoring cohort operationally defined the inflammatory category."
  - reference: PMID:37853245
    reference_title: "Recurrence and long-term outcomes of Tolosa-Hunt syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Isolated ocular motor nerve palsy was the most common (82.4%) finding of ophthalmoplegia, involving the oculomotor nerve in more than half of the cases (52.0%)."
    explanation: "Establishes that the prototypical inflammatory cause, Tolosa-Hunt syndrome, most often presents through the oculomotor nerve specifically."
- name: RPON
  display_name: Recurrent painful ophthalmoplegic neuropathy (formerly ophthalmoplegic migraine)
  description: >-
    Rare disorder of repeated attacks of unilateral headache with ipsilateral
    ocular motor palsy, most often of cranial nerve III, with focal thickening
    and contrast enhancement of the nerve on MRI and usually full recovery.
    Reclassified by the International Headache Society in 2013 away from
    "ophthalmoplegic migraine" because the imaging indicates a neuropathy; the
    underlying mechanism remains unsettled.
  evidence:
  - reference: PMID:35659705
    reference_title: "Diagnostic controversies in recurrent painful ophthalmoplegic neuropathy: single case report with a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ophthalmoplegic migraine, renamed \"Recurrent Painful Ophthalmoplegic Neuropathy\" (RPON) in 2013 by the International Headache Society is a rare neurologic disorder characterized by recurrent attacks of ophthalmoplegia associated to ipsilateral headache."
    explanation: "Defines the entity and records the 2013 reclassification that renamed ophthalmoplegic migraine to RPON."
  - reference: PMID:35659705
    reference_title: "Diagnostic controversies in recurrent painful ophthalmoplegic neuropathy: single case report with a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical magnetic resonance imaging findings show a focal nerve thickening and contrast enhancement."
    explanation: "Records the imaging signature that separates RPON from aneurysmal and ischaemic third nerve palsy."
prevalence:
- subtype: Microvascular
  population: >-
    Patients with isolated oculomotor nerve palsy, referral-based university
    hospital, all departments, South Korea
  measure_type: PERIOD_PREVALENCE
  prevalence_class: UNKNOWN
  notes: >-
    Aetiological share, not a population rate: microvascular ischaemia
    accounted for 168/633 (26.5%) of isolated oculomotor nerve palsy cases
    ascertained across all departments over 18 years.
  evidence:
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most common etiology was microvascular (n = 168, 26.5%), followed by vascular anomalies (n = 110, 17.4%), neoplastic (n = 86, 13.6%), inflammatory (n = 79, 12.5%), idiopathic (n = 60, 9.5%) and traumatic (n = 53, 8.4%)."
    explanation: "Direct source for the aetiological fractions recorded here."
- subtype: Traumatic
  population: >-
    Municipal hospital inpatients with third nerve palsy personally examined by
    a single neuro-ophthalmologist over 37 years
  measure_type: PERIOD_PREVALENCE
  prevalence_class: UNKNOWN
  notes: >-
    Aetiological share in an inpatient population, where severe trauma and
    herniation are over-represented relative to outpatient neuro-ophthalmology
    series: trauma 26%, tumour 12%, diabetes 11%, aneurysm 10%.
  evidence:
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Causes were trauma (26%), tumor (12%), diabetes (11%), aneurysm (10%), surgery (10%), stroke (8%), infection (5%), Guillain-Barre and Fisher syndromes (5%), idiopathic cavernous sinusitis (3%), benign self-limited (2%), miscellaneous (4%), and unknown (3%)."
    explanation: "Direct source for the inpatient aetiological distribution, which differs markedly from referral outpatient series."
- population: Korean population
  measure_type: ANNUAL_INCIDENCE
  prevalence_class: BAND_1_9_PER_100000
  rate_per_100000: 3.71
  notes: >-
    Population incidence of third cranial nerve palsy reported as 3.71 per
    100,000 per year, against 5.73 for trochlear and 4.66 for abducens palsy in
    the same population. Incidence rises with age, accelerating after 60.
  evidence:
  - reference: PMID:38352051
    reference_title: "Retrospective Analysis of Factors Related to the Long-Term Recovery of Third, Fourth, and Sixth Cranial Nerve Palsy with Etiologies and Clinical Course in a Tertiary Hospital."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recent reports have indicated that the incidence rates of third, fourth, and sixth cranial nerve palsy among the Korean population are 3.71, 5.73, and 4.66 per 100,000 per year, respectively."
    explanation: "Gives the population annual incidence of third nerve palsy alongside the other ocular motor nerves for context."
epidemiology:
- name: Setting dependence of the aetiological mix
  description: >-
    The apparent cause distribution of third nerve palsy depends heavily on
    where patients are ascertained. Inpatient and referral populations differ,
    and within one hospital the mix differs by the specialty managing the
    patient, so no single published distribution should be read as the
    population truth.
  evidence:
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The proportion of etiologies of isolated oculomotor nerve palsy may differ according to the specialties involved in the management."
    explanation: "The authors' own conclusion that ascertainment route biases the measured aetiological distribution."
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bilateral TNPs, multiple cranial neuropathies, and accompanying neurological signs were common among our inpatients, as were causes rare in outpatient settings such as severe trauma, transtentorial herniation, midbrain strokes, and the Guillain-Barre syndrome."
    explanation: "Documents the specific causes enriched in an inpatient setting relative to outpatient neuro-ophthalmology cohorts."
- name: Pain accompanies both the dangerous and the benign cause
  description: >-
    Painful onset is common in aneurysmal third nerve palsy but is also common
    in diabetic microvascular palsy, so pain alone cannot be used to triage
    urgency.
  factors:
  - headache
  - periorbital pain
  evidence:
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "painful onset occurred with 94% of aneurysm and 69% of diabetic cases."
    explanation: "Directly quantifies pain in both aneurysmal and diabetic palsy, showing pain does not discriminate between them."
progression:
- phase: Acute onset
  subtype: Microvascular
  notes: >-
    Microvascular palsy begins abruptly, often with periorbital pain, and
    reaches its deficit over hours to days.
  evidence:
  - reference: PMID:39510537
    reference_title: "Ocular Motor Mononeuropathies in Diabetes Mellitus: A Brief Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical manifestations often include ptosis, diplopia, and periorbital pain."
    explanation: "Records the acute symptom triad with which diabetic ocular motor mononeuropathy presents."
- phase: Spontaneous recovery
  subtype: Microvascular
  notes: >-
    The defining prognostic feature of the microvascular subtype is
    spontaneous resolution, typically within weeks to a few months, without
    directed treatment of the nerve itself.
  evidence:
  - reference: PMID:39510537
    reference_title: "Ocular Motor Mononeuropathies in Diabetes Mellitus: A Brief Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Spontaneous recovery is seen in many cases."
    explanation: "Supports spontaneous recovery as the expected course of diabetic ocular motor mononeuropathy."
- phase: Post-treatment recovery
  subtype: Compressive
  notes: >-
    After treatment of a posterior communicating artery aneurysm, recovery of
    the nerve depends chiefly on how severe the palsy was and how long it was
    left untreated, which is the mechanistic argument for early intervention.
  evidence:
  - reference: PMID:30455133
    reference_title: "Posterior communicating aneurysm with oculomotor nerve palsy: Predictors of nerve recovery."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "initial palsy severity and preoperative palsy times are important predictors for ONP recovery, early treatment is recommended to achieve complete recovery of ONP, regardless of the presence or absence of SAH"
    explanation: "Identifies severity and delay as the determinants of nerve recovery after aneurysm treatment."
- phase: Attack and remission cycle
  subtype: RPON
  notes: >-
    RPON runs as discrete attacks with full recovery between them in most
    patients, although repeated attacks can leave permanent deficit.
  evidence:
  - reference: PMID:35659705
    reference_title: "Diagnostic controversies in recurrent painful ophthalmoplegic neuropathy: single case report with a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In the majority of cases, there is a full recovery within days or weeks."
    explanation: "Supports the relapsing-remitting course with usual full recovery that characterizes RPON."
- phase: Prognostic determinants of recovery
  notes: >-
    Across aetiologies, the two factors that predict good long-term recovery
    are a short symptom onset (under one week) and involvement of the third
    nerve alone rather than several cranial nerves. Recovery also differs
    sharply by cause, being best for inflammatory and worst for compressive
    palsies in one tertiary series.
  evidence:
  - reference: PMID:38352051
    reference_title: "Retrospective Analysis of Factors Related to the Long-Term Recovery of Third, Fourth, and Sixth Cranial Nerve Palsy with Etiologies and Clinical Course in a Tertiary Hospital."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The onset of symptoms in less than 1 week and isolated nerve involvement were associated with better prognosis in subjects with third, fourth, and sixth cranial nerve palsy."
    explanation: "Identifies the two independent prognostic factors for recovery, adjusted for age, sex, and vascular risk factors."
  - reference: PMID:38352051
    reference_title: "Retrospective Analysis of Factors Related to the Long-Term Recovery of Third, Fourth, and Sixth Cranial Nerve Palsy with Etiologies and Clinical Course in a Tertiary Hospital."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our study revealed that ischemic and compressive lesions were the most common etiology of oculomotor nerve palsy, comprising 24.6% each."
    explanation: "Independent tertiary-hospital series confirming ischaemic and compressive causes as the two dominant aetiologies of third nerve palsy."
- phase: Amblyopia risk in childhood
  subtype: Congenital
  notes: >-
    In children the palsy competes with visual development, so the clinically
    dominant late outcome is amblyopia and loss of binocularity rather than the
    ocular motor deficit itself.
  evidence:
  - reference: PMID:16391633
    reference_title: "Oculomotor nerve palsy in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Amblyopia developed in 7 (39%) children and was successfully treated in 5 of the 7 (71%)."
    explanation: "Quantifies amblyopia as a frequent and largely treatable sequela of childhood third nerve palsy."
pathophysiology:
- name: Somatotopic Segregation of Pupillomotor and Somatic Motor Fibres
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    Cranial nerve III carries two functionally distinct fibre populations that
    are not intermingled. The preganglionic parasympathetic pupillomotor and
    accommodative fibres travel superficially, at the periphery of the nerve;
    the somatic motor fibres to levator palpebrae superioris and the four
    extraocular muscles travel deeper. This anatomical arrangement is the
    single fact from which the entire pupil-involving versus pupil-sparing
    clinical axis follows: an insult applied from outside the nerve reaches the
    superficial fibres first, whereas an insult arising within the nerve's
    substance reaches the deeper fibres first. Nothing about the fibres
    themselves confers differential vulnerability - it is their position.
  evidence:
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Parasympathetic fibers, located superficially, innervate the ciliary muscle and sphincter pupillae, mediating lens accommodation and pupillary constriction."
    explanation: "Directly states the superficial peripheral position of the pupillomotor parasympathetic fibres, the anatomical premise of this entry. Classified OTHER because this is a reference-work synthesis of established human neuroanatomy rather than a study reporting its own data."
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Somatic motor fibers, located deeper, innervate the levator palpebrae superioris, which elevates the upper eyelid, and 4 extraocular muscles"
    explanation: "States the complementary deeper position of the somatic motor fibres, completing the segregation on which the pupil axis depends. Classified OTHER for the same reason as the companion quote."
  - reference: PMID:36116851
    reference_title: "The Oculomotor Nerve: Anatomy and Pathology."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "It also has parasympathetic pre-ganglionic fibers, responsible for the innervation of sphincter pupillae and ciliary muscles."
    explanation: "Independent anatomical review confirming that the nerve carries a preganglionic parasympathetic component serving the pupil and lens, alongside its motor component."
  cell_types:
  - preferred_term: peripheral nervous system neuron
    term:
      id: CL:2000032
      label: peripheral nervous system neuron
  locations:
  - preferred_term: oculomotor nerve
    term:
      id: UBERON:0001643
      label: oculomotor nerve
  notes: >-
    The peripheral position of the pupillomotor fibres was established
    experimentally by Kerr and Hollowell (PMID:14213479) and by Sunderland and
    Hughes; neither has a retrievable abstract, so neither is cited as evidence
    here. The claim is instead anchored on contemporary reference sources whose
    text can be verified against the reference cache.
  downstream:
  - target: Extrinsic Compression of the Cisternal Oculomotor Nerve
    causal_link_type: DIRECT
    description: >-
      Because the pupillomotor fibres lie at the surface, an extrinsic mass
      contacts them before it reaches the motor core.
    evidence:
    - reference: PMID:6830173
      reference_title: "Pupil sparing in oculomotor palsy: a brief review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The clinical dictum that pupil sparing in oculomotor nerve palsy predicts an extraaxial ischemic lesion while pupil involvement predicts an extraaxial compressive lesion has some important exceptions."
      explanation: "States the compression-takes-the-pupil rule that the fibre arrangement predicts, while flagging that it is a dictum with exceptions."
  - target: Endoneurial Microvascular Ischaemia of the Oculomotor Nerve Core
    causal_link_type: DIRECT
    description: >-
      Because the somatic motor fibres occupy the core, an ischaemic insult to
      the nerve's internal blood supply damages them while the superficially
      placed pupillomotor fibres are relatively protected.
    evidence:
    - reference: PMID:39510537
      reference_title: "Ocular Motor Mononeuropathies in Diabetes Mellitus: A Brief Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Pupillary sparing is a characteristic of third nerve palsy."
      explanation: "Records pupillary sparing as the characteristic pupil behaviour in the diabetic microvascular setting this review addresses."
- name: Extrinsic Compression of the Cisternal Oculomotor Nerve
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    A posterior communicating artery aneurysm, tumour, or herniating uncus
    presses on the nerve in the subarachnoid space between the midbrain and the
    cavernous sinus. Mass effect is transmitted from the outside inwards, so the
    superficial pupillomotor fibres bear the injury first and most heavily. The
    same compression usually produces pain, and in the aneurysmal case it
    signals a lesion that may be about to rupture.
  evidence:
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Etiologies range from benign microvascular ischemia to compressive intracranial lesions, including aneurysms, making prompt recognition and appropriate evaluation critical, particularly in cases presenting with pupillary dysfunction."
    explanation: "Ties compressive aetiology to pupillary dysfunction and to the clinical urgency that follows from it."
  - reference: PMID:39692993
    reference_title: "Oculomotor nerve palsy recovery following microsurgery vs. endovascular treatment of posterior communicating artery aneurysms: a comparative meta-analysis of short- and long-term outcomes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Due to anatomical proximity, aneurysmal mass effect has been identified as the most prevalent ONP etiology and often leads to rupture"
    explanation: "Identifies mass effect from an adjacent aneurysm as the operative mechanism and links it to rupture risk."
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Third nerve damage occurred in the subarachnoid space in 32%, the cavernous sinus in 23%, the brainstem in 14%, as a nonlocalized peripheral neuropathy in 18% and at an uncertain location in 13%."
    explanation: "The subarachnoid segment, where the nerve is exposed to aneurysms and herniation, is the most frequently damaged site."
  cell_types:
  - preferred_term: peripheral nervous system neuron
    term:
      id: CL:2000032
      label: peripheral nervous system neuron
  - preferred_term: Schwann cell
    term:
      id: CL:0002573
      label: Schwann cell
  biological_processes:
  - preferred_term: response to mechanical stimulus
    term:
      id: GO:0009612
      label: response to mechanical stimulus
  locations:
  - preferred_term: oculomotor nerve
    term:
      id: UBERON:0001643
      label: oculomotor nerve
  - preferred_term: subarachnoid space
    term:
      id: UBERON:0000315
      label: subarachnoid space
  downstream:
  - target: Superficial Pupillomotor Fibre Injury
    causal_link_type: DIRECT
    description: >-
      External pressure damages the peripherally placed parasympathetic fibres,
      producing pupil involvement in almost all aneurysmal palsies.
    evidence:
    - reference: PMID:21059515
      reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Only 2% of aneurysms spared the pupil."
      explanation: "Quantifies how nearly obligatory pupil involvement is in aneurysmal compression, which is what the superficial fibre position predicts."
  - target: Somatic Motor Fibre Conduction Failure
    causal_link_type: DIRECT
    description: >-
      Continued or severe compression penetrates to the deeper motor fibres,
      adding ptosis and ophthalmoplegia to the pupillary sign.
    evidence:
    - reference: PMID:39692993
      reference_title: "Oculomotor nerve palsy recovery following microsurgery vs. endovascular treatment of posterior communicating artery aneurysms: a comparative meta-analysis of short- and long-term outcomes."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Complete ONP diagnosis is established when the simultaneous occurrence of ptosis, fixed mydriasis, diplopia, and ophthalmoplegia is observed."
      explanation: "Defines the complete aneurysmal palsy as combining motor deficit with pupillary involvement, the endpoint of compression reaching the motor core."
  - target: Aberrant Regeneration of the Oculomotor Nerve
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Severe compressive injury that transects axons is followed, weeks to
      months later, by misdirected regrowth. Aberrant regeneration therefore
      marks a structural lesion and is not seen after purely ischaemic palsy.
    evidence:
    - reference: PMID:6830173
      reference_title: "Pupil sparing in oculomotor palsy: a brief review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Careful examination is also necessary to separate examples of apparent pupil sparing in cases of aberrant regeneration and in some instances of cavernous sinus compression."
      explanation: "Treats aberrant regeneration and compressive lesions together as the settings in which apparent pupil sparing arises, linking compression to subsequent misdirected regrowth."
- name: Transtentorial Herniation Compressing Cranial Nerve III
  biological_scale: ORGANISM
  mechanism_confidence: ESTABLISHED
  description: >-
    When rising intracranial pressure displaces the uncus through the tentorial
    incisura, cranial nerve III is one of the structures trapped in that
    aperture. The resulting ipsilateral third nerve palsy, classically
    beginning as a dilating pupil, is a bedside marker of a life-threatening
    intracranial emergency rather than an isolated ocular motor problem.
  evidence:
  - reference: PMID:30725793
    reference_title: "Uncal Herniation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinically, an uncal herniation is characterized by a predictable pattern of neuroanatomic compression, including ipsilateral third nerve palsy, contralateral motor deficits from compression of the cerebral peduncle, and progressive brainstem dysfunction."
    explanation: "Establishes ipsilateral third nerve palsy as a defining component of the uncal herniation syndrome."
  - reference: PMID:30725793
    reference_title: "Uncal Herniation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Critical neurovascular structures traverse this confined aperture, including the midbrain, cranial nerve III, the posterior cerebral arteries, and the superior cerebellar arteries."
    explanation: "Gives the anatomical reason the third nerve is compressed during herniation: it passes through the tentorial notch."
  locations:
  - preferred_term: oculomotor nerve
    term:
      id: UBERON:0001643
      label: oculomotor nerve
  - preferred_term: cerebral peduncle
    term:
      id: UBERON:0002623
      label: cerebral peduncle
  downstream:
  - target: Superficial Pupillomotor Fibre Injury
    causal_link_type: DIRECT
    description: >-
      Herniation compresses the nerve from outside, so the pupil dilates first,
      which is why the "blown pupil" is watched for in raised intracranial
      pressure.
    evidence:
    - reference: PMID:30725793
      reference_title: "Uncal Herniation."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Jonathan Hutchinson first described unilateral pupillary dilation (Hutchinson pupil), initially attributed to midbrain involvement."
      explanation: "Records the historical and clinical association of unilateral pupillary dilation with this compressive syndrome."
- name: Endoneurial Microvascular Ischaemia of the Oculomotor Nerve Core
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    In diabetes, hypertension, dyslipidaemia, and smoking, small-vessel disease
    of the nerve's own blood supply produces ischaemic injury concentrated in
    the nerve's interior. Because the somatic motor fibres occupy that interior
    while the pupillomotor fibres lie superficially, the resulting palsy is
    typically diffuse across all cranial nerve III muscles yet leaves the pupil
    working - the pupil-sparing pattern. Sparing is a statistical tendency
    produced by geometry, not a guarantee.
  evidence:
  - reference: PMID:39510537
    reference_title: "Ocular Motor Mononeuropathies in Diabetes Mellitus: A Brief Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ocular motor mononeuropathies affect cranial nerves III, IV and VI and are more frequent in diabetes mellitus, with oculomotor nerve involvement being predominant."
    explanation: "Establishes the vascular-risk-factor setting and the predominance of cranial nerve III among the ocular motor mononeuropathies."
  - reference: PMID:11756854
    reference_title: "Patterns of extraocular muscle weakness in vasculopathic pupil-sparing, incomplete third nerve palsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of 55 patients with vasculopathic 3NP, 42 (76%) had normal pupillary function."
    explanation: "Quantifies pupil sparing in a consecutive vasculopathic third nerve palsy series."
  cell_types:
  - preferred_term: peripheral nervous system neuron
    term:
      id: CL:2000032
      label: peripheral nervous system neuron
  - preferred_term: Schwann cell
    term:
      id: CL:0002573
      label: Schwann cell
  biological_processes:
  - preferred_term: response to ischemia
    term:
      id: GO:0002931
      label: response to ischemia
  locations:
  - preferred_term: oculomotor nerve
    term:
      id: UBERON:0001643
      label: oculomotor nerve
  downstream:
  - target: Preserved Superficial Pupillomotor Function
    causal_link_type: DIRECT
    description: >-
      Ischaemia of the nerve core leaves the peripherally placed parasympathetic
      fibres largely intact, which is the mechanistic content of "pupil-sparing".
    evidence:
    - reference: PMID:39510537
      reference_title: "Ocular Motor Mononeuropathies in Diabetes Mellitus: A Brief Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Pupillary sparing is a characteristic of third nerve palsy."
      explanation: "Supports preserved pupillary function as the expected pupil finding in diabetic ocular motor mononeuropathy."
  - target: Somatic Motor Fibre Conduction Failure
    causal_link_type: DIRECT
    description: >-
      Core ischaemia damages the somatic motor fibres, and when the palsy is
      incomplete the weakness is characteristically diffuse across all the
      muscles of cranial nerve III rather than focal.
    evidence:
    - reference: PMID:11756854
      reference_title: "Patterns of extraocular muscle weakness in vasculopathic pupil-sparing, incomplete third nerve palsy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Based on our series, most patients with EOM/levator involvement in pupil-sparing, incomplete 3NP of vasculopathic origin have a diffuse pattern of paresis."
      explanation: "Establishes the diffuse pattern of motor involvement produced by ischaemia of the nerve core."
- name: Superficial Pupillomotor Fibre Injury
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    Damage to the peripherally placed preganglionic parasympathetic fibres
    interrupts the efferent limb of the pupillary light reflex and of
    accommodation. The iris sphincter and ciliary muscle lose their excitatory
    drive, so the pupil dilates and stops constricting to light. This is
    internal ophthalmoplegia, the pupil-involving pattern.
  evidence:
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Parasympathetic fibers, located superficially, innervate the ciliary muscle and sphincter pupillae, mediating lens accommodation and pupillary constriction."
    explanation: "Identifies the effector targets whose denervation produces mydriasis and loss of accommodation when these fibres are injured."
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only 2% of aneurysms spared the pupil."
    explanation: "Shows that the compressive aetiologies which reach these superficial fibres almost always produce pupil involvement."
  cell_types:
  - preferred_term: smooth muscle cell of sphincter of pupil
    term:
      id: CL:0002243
      label: smooth muscle cell of sphincter of pupil
  - preferred_term: ciliary muscle cell
    term:
      id: CL:1000443
      label: ciliary muscle cell
  biological_processes:
  - preferred_term: smooth muscle contraction
    modifier: DECREASED
    term:
      id: GO:0006939
      label: smooth muscle contraction
  locations:
  - preferred_term: iris
    term:
      id: UBERON:0001769
      label: iris
  - preferred_term: ciliary body
    term:
      id: UBERON:0001775
      label: ciliary body
  downstream:
  - target: Mydriasis
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:39692993
      reference_title: "Oculomotor nerve palsy recovery following microsurgery vs. endovascular treatment of posterior communicating artery aneurysms: a comparative meta-analysis of short- and long-term outcomes."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Complete ONP diagnosis is established when the simultaneous occurrence of ptosis, fixed mydriasis, diplopia, and ophthalmoplegia is observed."
      explanation: "Records fixed mydriasis as a component of complete third nerve palsy from aneurysmal compression."
  - target: Anisocoria
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:30725793
      reference_title: "Uncal Herniation."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Jonathan Hutchinson first described unilateral pupillary dilation (Hutchinson pupil), initially attributed to midbrain involvement."
      explanation: "Unilateral pupillary dilation from third nerve compression is by definition an anisocoria."
- name: Preserved Superficial Pupillomotor Function
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    The counterpart node to pupillomotor injury: when the insult originates
    inside the nerve rather than outside it, the superficial parasympathetic
    fibres continue to conduct, the pupil reacts normally to light, and the
    palsy is described as pupil-sparing. Curated as a positive mechanistic
    state, not as the mere absence of a finding, because it is the observable
    consequence of where the insult was applied.
  evidence:
  - reference: PMID:11756854
    reference_title: "Patterns of extraocular muscle weakness in vasculopathic pupil-sparing, incomplete third nerve palsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of 55 patients with vasculopathic 3NP, 42 (76%) had normal pupillary function."
    explanation: "Documents normal pupillary function as the majority finding in vasculopathic third nerve palsy."
  - reference: PMID:39510537
    reference_title: "Ocular Motor Mononeuropathies in Diabetes Mellitus: A Brief Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pupillary sparing is a characteristic of third nerve palsy."
    explanation: "Supports pupil sparing as the characteristic pattern in the diabetic microvascular setting."
  cell_types:
  - preferred_term: smooth muscle cell of sphincter of pupil
    term:
      id: CL:0002243
      label: smooth muscle cell of sphincter of pupil
  locations:
  - preferred_term: iris
    term:
      id: UBERON:0001769
      label: iris
  notes: >-
    Pupil sparing is a probabilistic localizing sign, not a rule. It occurs in a
    minority of compressive subarachnoid lesions and in a large proportion of
    cavernous sinus compressive lesions, and apparent sparing can be produced by
    aberrant regeneration. See the "Exceptions to the pupil rule" discussion.
- name: Somatic Motor Fibre Conduction Failure
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    Loss of conduction in the deeper somatic motor fibres denervates levator
    palpebrae superioris and the superior, medial, and inferior recti and the
    inferior oblique. The eye is left under the unopposed action of the lateral
    rectus and superior oblique, producing the classic down-and-out position,
    with ptosis and binocular diplopia. This node is shared by every aetiological
    subtype - it is the final common motor deficit.
  evidence:
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical presentation includes ptosis, ophthalmoplegia, diplopia, and variable pupillary involvement, resulting in the characteristic down-and-out eye position in complete palsy."
    explanation: "Directly describes the motor deficit and resulting eye position produced by somatic fibre failure."
  - reference: PMID:36116851
    reference_title: "The Oculomotor Nerve: Anatomy and Pathology."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "It is a purely motor nerve responsible for the innervation of all the extraocular muscles, except the superior oblique and lateral rectus muscles."
    explanation: "Specifies which muscles are denervated, and by exclusion which two remain active to produce the down-and-out position."
  cell_types:
  - preferred_term: peripheral nervous system neuron
    term:
      id: CL:2000032
      label: peripheral nervous system neuron
  biological_processes:
  - preferred_term: regulation of skeletal muscle contraction
    modifier: DECREASED
    term:
      id: GO:0014819
      label: regulation of skeletal muscle contraction
  locations:
  - preferred_term: oculomotor nerve
    term:
      id: UBERON:0001643
      label: oculomotor nerve
  downstream:
  - target: Ptosis
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:30252368
      reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Somatic motor fibers, located deeper, innervate the levator palpebrae superioris, which elevates the upper eyelid, and 4 extraocular muscles"
      explanation: "Denervation of levator palpebrae superioris is the direct cause of the ptosis."
  - target: Ophthalmoplegia
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:30252368
      reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Typical presentation includes ptosis, ophthalmoplegia, diplopia, and variable pupillary involvement, resulting in the characteristic down-and-out eye position in complete palsy."
      explanation: "Supports ophthalmoplegia as the direct motor consequence of the palsy."
  - target: Diplopia
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:30592440
      reference_title: "The aetiologies of the unilateral oculomotor nerve palsy: a review of the literature."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Oculomotor nerve palsy (ONP) is an important and common clinical diagnosis. Its main features are diplopia and ptosis."
      explanation: "Supports diplopia as a cardinal consequence of ocular misalignment from the motor deficit."
- name: Traumatic Stretch Injury of the Oculomotor Nerve at Fixed Tether Points
  biological_scale: TISSUE
  mechanism_confidence: PROVISIONAL
  description: >-
    Head injury displaces the brain relative to the skull base while the nerve
    remains anchored where it passes the posterior petroclinoid ligament and the
    tentorial edge. The nerve is stretched or contused at those tether points.
    Because the injury is a longitudinal stretch rather than a focal external
    mass, it does not respect the superficial-to-deep gradient in the way
    compression does, and pupil-sparing traumatic palsies are described.
  evidence:
  - reference: PMID:16978866
    reference_title: "Traumatic oculomotor nerve palsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The suggested mechanism of the oculomotor nerve palsy with pupil sparing in this case is stretching of the oculomotor nerve at the posterior petroclinoid ligament, maintaining an intact pupillomotor nerve."
    explanation: "Gives the stretch-at-a-tether-point mechanism together with the observation that the pupillomotor fibres can survive it. Marked PROVISIONAL because this is a single imaged case with an author-proposed mechanism."
  - reference: PMID:16978866
    reference_title: "Traumatic oculomotor nerve palsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Oculomotor nerve palsy without internal ophthalmoplegia (pupil sparing) is extremely rare."
    explanation: "Qualifies the mechanism: pupil sparing after trauma is possible but uncommon, so a traumatic palsy is not assumed to spare the pupil."
  locations:
  - preferred_term: oculomotor nerve
    term:
      id: UBERON:0001643
      label: oculomotor nerve
  biological_processes:
  - preferred_term: response to mechanical stimulus
    term:
      id: GO:0009612
      label: response to mechanical stimulus
  downstream:
  - target: Somatic Motor Fibre Conduction Failure
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:16978866
      reference_title: "Traumatic oculomotor nerve palsy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Neuro-ophthalmic examination showed that the left eye had limited adduction, supraduction, and infraduction, incomplete convergence and left ptosis, but no internal ophthalmoplegia."
      explanation: "Documents the motor deficit produced by the traumatic stretch injury with the pupil preserved."
  - target: Aberrant Regeneration of the Oculomotor Nerve
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Traumatic axonal disruption, like compression, is followed by regrowth
      that can reach the wrong target, so synkinesis after head injury is a
      late marker of the severity of the original axonal injury.
    evidence:
    - reference: PMID:6830173
      reference_title: "Pupil sparing in oculomotor palsy: a brief review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Careful examination is also necessary to separate examples of apparent pupil sparing in cases of aberrant regeneration and in some instances of cavernous sinus compression."
      explanation: "Supports aberrant regeneration as a sequel of structural axonal injury; this review does not isolate the traumatic subgroup, so the edge is recorded as PARTIAL."
- name: Congenital Oculomotor Nerve Hypoplasia or Aplasia
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    In congenital palsy the nerve itself is maldeveloped rather than injured.
    High-resolution MRI shows thinning of the nerve along its whole course,
    thinning confined to its distal segment, or complete agenesis, with
    secondary atrophy of the extraocular muscles that the missing fibres would
    have supplied. The deficit is therefore a developmental one, present before
    any pupil-involving-versus-sparing logic applies, and in children pupillary
    signs lose their localizing value altogether.
  evidence:
  - reference: PMID:36580093
    reference_title: "Congenital isolated unilateral third nerve palsy in children: the diagnostic contribution of high-resolution MR imaging."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "One patient had complete nerve agenesis, two patients showed a diffuse thinning of the nerve, from the brainstem to the orbit and 3 patients showed a distal thinning of the oculomotor nerve, starting at the level of the cavernous sinus."
    explanation: "Documents the spectrum of structural nerve maldevelopment underlying congenital third nerve palsy."
  - reference: PMID:30997520
    reference_title: "Magnetic Resonance Imaging in 14 Patients with Congenital Oculomotor Nerve Palsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "On MR imaging, 5 patients (36%) had hypoplasia or aplasia of the oculomotor nerve with variable degrees of extraocular muscle atrophy on the affected side."
    explanation: "Independent series confirming nerve hypoplasia or aplasia with corresponding muscle atrophy in about a third of congenital cases."
  - reference: PMID:16391633
    reference_title: "Oculomotor nerve palsy in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Their pupillary signs, unlike those of adults, are not helpful in differentiating compressive etiologies from other causes."
    explanation: "Establishes the important caveat that the pupil axis central to this entry does not transfer to paediatric practice."
  biological_processes:
  - preferred_term: oculomotor nerve development
    modifier: DECREASED
    term:
      id: GO:0021557
      label: oculomotor nerve development
  locations:
  - preferred_term: oculomotor nerve
    term:
      id: UBERON:0001643
      label: oculomotor nerve
  downstream:
  - target: Somatic Motor Fibre Conduction Failure
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:30997520
      reference_title: "Magnetic Resonance Imaging in 14 Patients with Congenital Oculomotor Nerve Palsy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The most frequently involved muscles were the inferior rectus (64%) and medial rectus (50%), followed by the superior rectus (29%) and inferior oblique muscles (14%)."
      explanation: "Maps the missing or hypoplastic nerve onto the specific extraocular muscles left without innervation."
  - target: Amblyopia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      A congenital palsy during the amblyogenic period leaves the affected eye
      misaligned and often ptotic, so it is deprived of a clear, aligned image
      and fails to develop normal acuity.
    evidence:
    - reference: PMID:16391633
      reference_title: "Oculomotor nerve palsy in childhood."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Amblyopia developed in 7 (39%) children and was successfully treated in 5 of the 7 (71%)."
      explanation: "Quantifies amblyopia as a downstream consequence in children with third nerve palsy."
- name: Focal Oculomotor Nerve Inflammation with Blood-Nerve Barrier Breakdown
  biological_scale: TISSUE
  mechanism_confidence: HYPOTHETICAL
  description: >-
    The proposed mechanism of recurrent painful ophthalmoplegic neuropathy.
    Attacks are accompanied by focal thickening and gadolinium enhancement of
    the cisternal nerve or its root entry zone, which indicates local breakdown
    of the blood-nerve barrier. Whether the primary event is ischaemic,
    inflammatory, demyelinating, or compressive is unresolved, and this node is
    curated as hypothetical for that reason.
  evidence:
  - reference: PMID:35659705
    reference_title: "Diagnostic controversies in recurrent painful ophthalmoplegic neuropathy: single case report with a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical magnetic resonance imaging findings show a focal nerve thickening and contrast enhancement."
    explanation: "Documents the imaging correlate that motivates a focal blood-nerve barrier mechanism."
  - reference: PMID:24567117
    reference_title: "Ophthalmoplegic migraine: from questions to answers."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The authors suggest that ischemic reversible breakdown of the blood-nerve barrier is the most probable cause of OM and to include MR findings in the hallmarks of the disease."
    explanation: "States the blood-nerve barrier hypothesis explicitly, as the authors' preferred but not established explanation."
  - reference: PMID:36694449
    reference_title: "Recurrent Painful Ophthalmoplegic Neuropathy: A case report with atypical features and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Several hypotheses have been proposed, including nerve compression, ischemia or inflammation/demyelination, but none has been completely accepted."
    explanation: "Confirms that no mechanism for RPON is established, which is why this node carries HYPOTHETICAL confidence."
  biological_processes:
  - preferred_term: neuroinflammatory response
    term:
      id: GO:0150076
      label: neuroinflammatory response
  locations:
  - preferred_term: oculomotor nerve
    term:
      id: UBERON:0001643
      label: oculomotor nerve
  downstream:
  - target: Somatic Motor Fibre Conduction Failure
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:35659705
      reference_title: "Diagnostic controversies in recurrent painful ophthalmoplegic neuropathy: single case report with a systematic review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "In 80% of cases it involves the third cranial nerve"
      explanation: "Establishes cranial nerve III as the nerve most often affected in RPON attacks."
  - target: Headache
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:26021754
      reference_title: "From ophthalmoplegic migraine to cranial neuropathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Ophthalmoplegic migraine (OM)/recurrent painful ophthalmoplegic neuropathy (RPON) is a rare disease consisting of recurrent unilateral headache accompanied or followed by ipsilateral ophthalmoplegia."
      explanation: "Establishes ipsilateral headache as an integral part of the attack rather than an incidental symptom."
- name: Aberrant Regeneration of the Oculomotor Nerve
  biological_scale: TISSUE
  mechanism_confidence: PROVISIONAL
  description: >-
    After severe axonal injury, regrowing fibres can reach the wrong target,
    so attempted adduction or downgaze elevates the eyelid or constricts the
    pupil. Clinically this matters twice over: it is a marker of structural
    (usually compressive or traumatic) rather than ischaemic injury, and a
    misdirected pupillomotor fibre can make an involved pupil look normal at
    rest, producing apparent pupil sparing.
  evidence:
  - reference: PMID:16391633
    reference_title: "Oculomotor nerve palsy in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Primary aberrant regeneration was the presenting sign in a child with neurofibromatosis type 2."
    explanation: "Documents aberrant regeneration occurring in a structural (neoplastic) third nerve lesion. Marked PROVISIONAL because the supporting observation here is a single case within a small cohort."
  - reference: PMID:6830173
    reference_title: "Pupil sparing in oculomotor palsy: a brief review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Careful examination is also necessary to separate examples of apparent pupil sparing in cases of aberrant regeneration and in some instances of cavernous sinus compression."
    explanation: "Establishes aberrant regeneration as a source of apparent, rather than true, pupil sparing, which is the reason this node bears on the entry's central axis."
  cell_types:
  - preferred_term: peripheral nervous system neuron
    term:
      id: CL:2000032
      label: peripheral nervous system neuron
  - preferred_term: Schwann cell
    term:
      id: CL:0002573
      label: Schwann cell
  locations:
  - preferred_term: oculomotor nerve
    term:
      id: UBERON:0001643
      label: oculomotor nerve
  downstream:
  - target: Preserved Superficial Pupillomotor Function
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      This is the counterexample to the entry's central axis. A pupillomotor
      fibre that regrows into a somatic motor pathway can hold the pupil at
      near-normal size at rest, so a genuinely pupil-involving structural palsy
      is misread as pupil-sparing. The sparing here is apparent, not true, and
      it is produced by the repair process rather than by the site of the
      original insult.
    evidence:
    - reference: PMID:6830173
      reference_title: "Pupil sparing in oculomotor palsy: a brief review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Careful examination is also necessary to separate examples of apparent pupil sparing in cases of aberrant regeneration and in some instances of cavernous sinus compression."
      explanation: "States directly that aberrant regeneration produces examples of apparent pupil sparing that must be separated from true sparing on careful examination."
phenotypes:
- category: Ocular motor
  name: Ptosis
  description: >-
    Drooping of the upper eyelid from denervation of levator palpebrae
    superioris. May be partial or complete, and in complete palsy can occlude
    the eye and mask the diplopia.
  phenotype_term:
    preferred_term: Ptosis
    term:
      id: HP:0000508
      label: Ptosis
  evidence:
  - reference: PMID:30592440
    reference_title: "The aetiologies of the unilateral oculomotor nerve palsy: a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Oculomotor nerve palsy (ONP) is an important and common clinical diagnosis. Its main features are diplopia and ptosis."
    explanation: "Establishes ptosis as one of the two cardinal features of the syndrome."
- category: Ocular motor
  name: Ophthalmoplegia
  description: >-
    Weakness of the extraocular muscles supplied by cranial nerve III, leaving
    the eye deviated down and out under the unopposed lateral rectus and
    superior oblique.
  phenotype_term:
    preferred_term: Ophthalmoplegia
    term:
      id: HP:0000602
      label: Ophthalmoplegia
  evidence:
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical presentation includes ptosis, ophthalmoplegia, diplopia, and variable pupillary involvement, resulting in the characteristic down-and-out eye position in complete palsy."
    explanation: "Names ophthalmoplegia and the down-and-out position as the typical motor presentation."
- category: Visual
  name: Diplopia
  description: >-
    Binocular double vision from ocular misalignment; it resolves when either
    eye is covered and is often the presenting complaint.
  phenotype_term:
    preferred_term: Diplopia
    term:
      id: HP:0000651
      label: Diplopia
  evidence:
  - reference: PMID:30592440
    reference_title: "The aetiologies of the unilateral oculomotor nerve palsy: a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Oculomotor nerve palsy (ONP) is an important and common clinical diagnosis. Its main features are diplopia and ptosis."
    explanation: "Establishes diplopia as the other cardinal feature alongside ptosis."
- category: Pupillary
  name: Mydriasis
  subtype: Compressive
  description: >-
    Dilated, poorly reactive pupil from denervation of the iris sphincter. The
    hallmark of the pupil-involving pattern and of compressive aetiology.
  phenotype_term:
    preferred_term: Mydriasis
    term:
      id: HP:0011499
      label: Mydriasis
  evidence:
  - reference: PMID:39692993
    reference_title: "Oculomotor nerve palsy recovery following microsurgery vs. endovascular treatment of posterior communicating artery aneurysms: a comparative meta-analysis of short- and long-term outcomes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Complete ONP diagnosis is established when the simultaneous occurrence of ptosis, fixed mydriasis, diplopia, and ophthalmoplegia is observed."
    explanation: "Records fixed mydriasis as a defining component of complete aneurysmal third nerve palsy."
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only 2% of aneurysms spared the pupil."
    explanation: "Shows how nearly universal pupil involvement is when the cause is an aneurysm."
- category: Pupillary
  name: Anisocoria
  description: >-
    Unequal pupil size when only one third nerve is affected. In the setting of
    rising intracranial pressure it is the "blown pupil" that signals uncal
    herniation.
  phenotype_term:
    preferred_term: Anisocoria
    term:
      id: HP:0009916
      label: Anisocoria
  evidence:
  - reference: PMID:30725793
    reference_title: "Uncal Herniation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Jonathan Hutchinson first described unilateral pupillary dilation (Hutchinson pupil), initially attributed to midbrain involvement."
    explanation: "The eponymous unilateral pupillary dilation of herniation is an anisocoria arising from third nerve compression."
- category: Pupillary
  name: Abnormal pupillary light reflex
  description: >-
    Loss of the efferent limb of the light reflex on the affected side, so the
    pupil fails to constrict to direct or consensual light while the afferent
    pathway is intact.
  phenotype_term:
    preferred_term: Abnormal pupillary light reflex
    term:
      id: HP:0007695
      label: Abnormal pupillary light reflex
  evidence:
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Parasympathetic fibers, located superficially, innervate the ciliary muscle and sphincter pupillae, mediating lens accommodation and pupillary constriction."
    explanation: "Identifies the efferent pathway whose interruption abolishes light-evoked pupillary constriction."
- category: Ocular alignment
  name: Exotropia
  description: >-
    Outward deviation of the affected eye produced by the unopposed lateral
    rectus once medial rectus function is lost.
  phenotype_term:
    preferred_term: Exotropia
    term:
      id: HP:0000577
      label: Exotropia
  evidence:
  - reference: PMID:30252368
    reference_title: "Cranial Nerve III Palsy (Oculomotor Palsy)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical presentation includes ptosis, ophthalmoplegia, diplopia, and variable pupillary involvement, resulting in the characteristic down-and-out eye position in complete palsy."
    explanation: "The down-and-out position is an exotropia combined with a hypotropia."
- category: Pain
  name: Headache
  description: >-
    Headache or periorbital pain accompanies most aneurysmal palsies and a
    majority of diabetic microvascular palsies, and is integral to the RPON
    attack.
  phenotype_term:
    preferred_term: Headache
    term:
      id: HP:0002315
      label: Headache
  evidence:
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "painful onset occurred with 94% of aneurysm and 69% of diabetic cases."
    explanation: "Quantifies painful onset in both the compressive and the microvascular subtypes."
  - reference: PMID:26021754
    reference_title: "From ophthalmoplegic migraine to cranial neuropathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ophthalmoplegic migraine (OM)/recurrent painful ophthalmoplegic neuropathy (RPON) is a rare disease consisting of recurrent unilateral headache accompanied or followed by ipsilateral ophthalmoplegia."
    explanation: "Supports headache as a defining component of the RPON attack."
- category: Visual development
  name: Amblyopia
  subtype: Congenital
  description: >-
    Failure of normal visual acuity development in the affected eye when the
    palsy occurs during the amblyogenic period, driven by misalignment and by
    lid occlusion from ptosis.
  phenotype_term:
    preferred_term: Amblyopia
    term:
      id: HP:0000646
      label: Amblyopia
  evidence:
  - reference: PMID:16391633
    reference_title: "Oculomotor nerve palsy in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Amblyopia developed in 7 (39%) children and was successfully treated in 5 of the 7 (71%)."
    explanation: "Quantifies amblyopia in a paediatric third nerve palsy cohort and its response to occlusion therapy."
- category: Vascular
  name: Posterior communicating artery aneurysm
  subtype: Compressive
  description: >-
    The causative lesion in the archetypal pupil-involving palsy. Its
    proximity to the cisternal third nerve is why it declares itself as an
    ocular motor syndrome, sometimes before it ruptures.
  phenotype_term:
    preferred_term: Posterior communicating artery aneurysm
    term:
      id: HP:0031773
      label: Posterior communicating artery aneurysm
  evidence:
  - reference: PMID:33845117
    reference_title: "Oculomotor nerve palsy due to posterior communicating artery aneurysm: Clipping vs coiling."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Posterior communicating artery aneurysms (PCoAA) usually present with brain hemorrhage, but they might present with oculomotor nerve palsy (ONP) in about one out of five patients."
    explanation: "Directly links the aneurysm to third nerve palsy as a presenting syndrome and quantifies how often."
environmental:
- name: Tobacco smoking
  description: >-
    Smoking is one of the vascular risk factors whose presence is required by
    the operational definition of microvascular oculomotor nerve palsy, acting
    through small-vessel disease of the nerve's own blood supply rather than
    through any nerve-specific toxicity.
  exposure_term:
    preferred_term: exposure to cigarette smoking
    term:
      id: ECTO:0100003
      label: exposure to cigarette smoking
  influences_mechanisms:
  - target: Endoneurial Microvascular Ischaemia of the Oculomotor Nerve Core
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Smoking predisposes to the endoneurial small-vessel disease that produces
      ischaemic injury to the core of the nerve; it is not itself the injury.
    evidence:
    - reference: PMID:38411317
      reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "with at least one vascular risk factor (hypertension, diabetes mellitus, dyslipidemia or smoking)"
      explanation: "Smoking is one of the vascular risk factors the anchoring cohort required before assigning a microvascular aetiology."
  evidence:
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The predilection for men in microvascular etiology may be related to a higher prevalence of vascular risk factors such as diabetes, hypertension and smoking in men in the Republic of Korea"
    explanation: >-
      Names smoking among the vascular risk factors the anchoring cohort ties to
      the microvascular aetiology, which is what makes it a relevant exposure for
      this disease rather than a general health risk.
- name: Head trauma
  description: >-
    Blunt head injury, typically from road traffic collision or fall,
    displaces the brain relative to the skull base and stretches the nerve
    where it is tethered. This is the initiating exposure of the traumatic
    subtype and the leading cause in inpatient and paediatric series.
  influences_mechanisms:
  - target: Traumatic Stretch Injury of the Oculomotor Nerve at Fixed Tether Points
    environmental_effect: TRIGGERS
    causal_link_type: DIRECT
    description: >-
      Head trauma is the direct initiating event of the stretch injury; the
      palsy is dated from it.
    evidence:
    - reference: PMID:38411317
      reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A traumatic cause was defined when there was a documented onset of oculomotor nerve palsy following head trauma and no other disorders to explain the oculomotor nerve palsy better."
      explanation: "States the temporal head-trauma-then-palsy relation that makes this exposure the trigger of the traumatic mechanism."
  notes: >-
    Deliberately left without an exposure_term. ECTO was searched for a head
    injury, traumatic brain injury, and physical trauma exposure concept and
    has none; per the dismech-terms rule that no term beats a bad one, no
    loosely related CURIE was substituted.
  evidence:
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Even though microvascular, traumatic and intracranial aneurysms are the most common causes of oculomotor nerve palsy"
    explanation: >-
      Establishes trauma as one of the most common causes of oculomotor nerve
      palsy, which is the disease-level claim this exposure entry makes.
treatments:
- name: Microsurgical Clipping of a Posterior Communicating Artery Aneurysm
  description: >-
    Open neurosurgical clipping of the aneurysm removes the mass compressing
    the cisternal nerve. Because the mechanism of injury is mass effect,
    relieving it early is what gives the nerve a chance to recover, and
    clipping produces faster recovery than endovascular treatment in the first
    year even though long-term rates converge.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: neurosurgical procedure
    term:
      id: NCIT:C15656
      label: Neurosurgical Procedure
  target_mechanisms:
  - target: Extrinsic Compression of the Cisternal Oculomotor Nerve
    treatment_effect: INHIBITS
    description: >-
      Clipping excludes the aneurysm from the circulation and decompresses the
      nerve, acting directly on the compressive node.
    evidence:
    - reference: PMID:33845117
      reference_title: "Oculomotor nerve palsy due to posterior communicating artery aneurysm: Clipping vs coiling."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Surgical clipping is superior to endovascular coiling in terms of complete recovery among patients with ONP due to PCoAAs."
      explanation: "Supports clipping as acting on the compressive mechanism with better complete-recovery outcomes."
  evidence:
  - reference: PMID:39692993
    reference_title: "Oculomotor nerve palsy recovery following microsurgery vs. endovascular treatment of posterior communicating artery aneurysms: a comparative meta-analysis of short- and long-term outcomes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Overall, microsurgical clipping of PComA aneurysms demonstrated a significantly higher likelihood of ONP recovery compared to EVT at 1,3,6, and 12 months follow-up."
    explanation: "Meta-analytic support for earlier nerve recovery after clipping than after endovascular treatment."
  - reference: PMID:39692993
    reference_title: "Oculomotor nerve palsy recovery following microsurgery vs. endovascular treatment of posterior communicating artery aneurysms: a comparative meta-analysis of short- and long-term outcomes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our findings suggest microsurgery leads to prompt ONP recovery from PComA aneurysms, while EVT shows potential for delayed favorable recovery; both treatments yield short-term recovery when administered early."
    explanation: "Qualifies the advantage as one of speed rather than of ultimate outcome, so the entry does not overstate clipping's superiority."
- name: Endovascular Coiling of a Posterior Communicating Artery Aneurysm
  description: >-
    Endovascular occlusion of the aneurysm sac secures the lesion against
    rupture and, less directly than clipping, reduces the pulsatile mass effect
    on the nerve. Nerve recovery is slower than after clipping but comparable
    by 18 to 24 months, and older patients may do relatively better with it.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: embolization therapy
    term:
      id: NCIT:C15230
      label: Embolization Therapy
  target_mechanisms:
  - target: Extrinsic Compression of the Cisternal Oculomotor Nerve
    treatment_effect: INHIBITS
    description: >-
      Coil occlusion removes the pulsatile haemodynamic stress transmitted to
      the adjacent nerve, though it leaves the aneurysm sac in place.
    evidence:
    - reference: PMID:39692993
      reference_title: "Oculomotor nerve palsy recovery following microsurgery vs. endovascular treatment of posterior communicating artery aneurysms: a comparative meta-analysis of short- and long-term outcomes."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "However, recent literature has reported favorable ONP recovery outcomes after endovascular treatment (EVT) suggesting other mechanisms associated with ONP occurrence, such as the pulsatile hemodynamic stress (water hammer effect) of cerebral aneurysms"
      explanation: "Supports pulsatile haemodynamic stress, not sac volume alone, as part of the compressive mechanism that endovascular treatment addresses."
  evidence:
  - reference: PMID:30455133
    reference_title: "Posterior communicating aneurysm with oculomotor nerve palsy: Predictors of nerve recovery."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, the aneurysm treatment modality was not correlated with nerve recovery in either analysis."
    explanation: "A single-centre series in which modality did not predict recovery, tempering the meta-analytic preference for clipping."
- name: Vascular Risk Factor Management in Microvascular Palsy
  description: >-
    There is no treatment directed at the ischaemic nerve itself. Management is
    optimisation of glycaemic control and of the other vascular risk factors,
    plus observation, since the natural history is spontaneous recovery.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: therapeutic procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  target_mechanisms:
  - target: Endoneurial Microvascular Ischaemia of the Oculomotor Nerve Core
    treatment_effect: MODULATES
    description: >-
      Risk factor control acts on the small-vessel disease upstream of
      endoneurial ischaemia rather than on the nerve injury already sustained.
    evidence:
    - reference: PMID:39510537
      reference_title: "Ocular Motor Mononeuropathies in Diabetes Mellitus: A Brief Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Treatment includes optimised glycaemic control and management of vascular risk factors."
      explanation: "States the management approach directed at the microvascular mechanism."
  evidence:
  - reference: PMID:39510537
    reference_title: "Ocular Motor Mononeuropathies in Diabetes Mellitus: A Brief Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Spontaneous recovery is seen in many cases."
    explanation: "Supports observation as reasonable management because the natural history is favourable."
- name: Botulinum Toxin Injection for Acute Ocular Misalignment
  description: >-
    Chemodenervation of the antagonist muscle reduces the deviation and the
    diplopia during the acute phase. It is symptomatic: it does not act on the
    nerve lesion, and its benefit over expectant management is confined to
    acute palsy.
  therapeutic_modality: OTHER
  notes: >-
    Modality recorded as OTHER deliberately. Botulinum toxin is a bacterial
    protein toxin used as a pharmacological blocking agent, so it is neither a
    SMALL_MOLECULE nor a PROTEIN_REPLACEMENT (nothing deficient is being
    replaced). The machine-readable identity is carried by treatment_term plus
    therapeutic_agent.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: botulinum toxin type A
      term:
        id: CHEBI:3160
        label: Botulinum toxin type A
  target_phenotypes:
  - preferred_term: Diplopia
    term:
      id: HP:0000651
      label: Diplopia
  evidence:
  - reference: PMID:38112391
    reference_title: "Botulinum Toxin Injection for the Treatment of Third, Fourth, and Sixth Nerve Palsy: A Meta-Analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The overall treatment success rate in acute and chronic nerve palsy was 79% and 33%, respectively."
    explanation: "Quantifies the sharp difference in benefit between acute and chronic palsy."
  - reference: PMID:38112391
    reference_title: "Botulinum Toxin Injection for the Treatment of Third, Fourth, and Sixth Nerve Palsy: A Meta-Analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Botulinum toxin can be used for the treatment of acute third, fourth, and sixth nerve palsy, especially in patients with acute palsy and more severe tropia."
    explanation: "Supports use restricted to the acute setting; the meta-analysis pools third, fourth, and sixth nerve palsy rather than isolating cranial nerve III."
- name: Strabismus and Ptosis Surgery for Residual Deficit
  description: >-
    Once recovery has plateaued, surgery addresses the mechanical consequences
    rather than the nerve: muscle shortening or lengthening, transposition,
    globe fixation, and ptosis repair, usually in combination. The aim is
    alignment, field of single vision, and appearance, not reinnervation.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: surgical procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  target_phenotypes:
  - preferred_term: Ptosis
    term:
      id: HP:0000508
      label: Ptosis
  - preferred_term: Exotropia
    term:
      id: HP:0000577
      label: Exotropia
  - preferred_term: Diplopia
    term:
      id: HP:0000651
      label: Diplopia
  evidence:
  - reference: PMID:38303488
    reference_title: "Surgical management of oculomotor nerve palsy - a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These included: muscle shortening and lengthening procedures, muscle transposition, globe fixation and ptosis surgery."
    explanation: "Enumerates the surgical techniques used for residual third nerve palsy."
  - reference: PMID:38303488
    reference_title: "Surgical management of oculomotor nerve palsy - a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Strabismus surgery for OMN palsy can be approached through a variety of different techniques to improve the quality of life, independence and aesthetics for the patient."
    explanation: "States the goals of surgery as functional and aesthetic rehabilitation rather than nerve recovery."
- name: High-Dose Corticosteroid Therapy for Inflammatory Palsy
  description: >-
    In Tolosa-Hunt syndrome and other steroid-responsive inflammatory third
    nerve palsies, high-dose corticosteroids shorten the symptomatic episode
    and the total treatment course. The prognosis is favourable but recurrence
    during or after tapering is common, so response is not the same as cure.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: systemic corticosteroid therapy
    term:
      id: NCIT:C122080
      label: Systemic Corticosteroid Therapy
  evidence:
  - reference: PMID:37853245
    reference_title: "Recurrence and long-term outcomes of Tolosa-Hunt syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "High-dose corticosteroids can be an effective initial treatment and reduce the total treatment duration."
    explanation: "Supports high-dose corticosteroids as effective initial therapy for the prototypical inflammatory cause."
  - reference: PMID:37853245
    reference_title: "Recurrence and long-term outcomes of Tolosa-Hunt syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recurrence occurred during steroid tapering as part of the initial treatment in seven, while in 18 patients, it happened after the successful termination of the initial treatment."
    explanation: "Qualifies the benefit: a quarter of patients recurred, so steroid responsiveness does not amount to durable cure."
- name: Amblyopia Therapy in Childhood Palsy
  description: >-
    In children within the amblyogenic period, occlusion therapy for the
    sound eye protects visual development, which is a different and often more
    consequential target than the ocular motor deficit itself.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: therapeutic procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  target_phenotypes:
  - preferred_term: Amblyopia
    term:
      id: HP:0000646
      label: Amblyopia
  evidence:
  - reference: PMID:16391633
    reference_title: "Oculomotor nerve palsy in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Good visual acuity was obtained in children within the amblyogenic age group with appropriate occlusion therapy."
    explanation: "Supports occlusion therapy as effective for the amblyopia that complicates childhood third nerve palsy."
diagnosis:
- name: MRI of the oculomotor nerve with vascular imaging
  description: >-
    Because the syndrome is defined by the affected nerve rather than by a
    single lesion, imaging is what assigns the aetiological subtype. MRI
    evaluates the nerve along its course from midbrain to orbit; vascular
    imaging is directed at the aneurysm that must not be missed. In children,
    where pupillary signs carry no localizing value, imaging is not optional.
  evidence:
  - reference: PMID:36116851
    reference_title: "The Oculomotor Nerve: Anatomy and Pathology."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Magnetic resonance imaging (MRI) is the best imaging exam to evaluate patients with clinical signs of third cranial nerve palsy."
    explanation: "Establishes MRI as the primary imaging modality for evaluating third cranial nerve palsy."
  - reference: PMID:16391633
    reference_title: "Oculomotor nerve palsy in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Children with oculomotor nerve palsy require neuroimaging."
    explanation: "Supports imaging as mandatory in children, where the pupil cannot be used to triage compressive causes."
differential_diagnoses:
- name: Mimics of oculomotor nerve palsy
  description: >-
    Several conditions reproduce parts of the syndrome without a third nerve
    lesion, and each must be excluded before the diagnosis is assigned:
    myasthenia gravis (fatiguable ptosis and ophthalmoplegia, pupil always
    spared), thyroid-associated orbitopathy and orbital myositis (restrictive
    rather than paralytic), Horner syndrome and Adie tonic pupil (anisocoria of
    other origin), congenital ptosis, and Duane retraction syndrome.
  distinguishing_features:
  - >-
    A true third nerve palsy weakens a defined muscle set while sparing the
    superior oblique and lateral rectus.
  - >-
    Thyroid-associated orbitopathy and orbital myositis limit movement
    mechanically rather than by denervation.
  - >-
    Myasthenia gravis fluctuates, is fatiguable, and never dilates the pupil.
  - >-
    Horner syndrome produces a small rather than a large pupil.
  evidence:
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Particular attention was paid to exclude disorders that may mimic oculomotor nerve palsy, such as exotropia, blepharoptosis, congenital ptosis, anisocoria of other causes"
    explanation: "The anchoring cohort enumerates the mimics it excluded, which is the differential this entry adopts."
discussions:
- discussion_id: pupil_rule_exceptions
  kind: CONTROVERSY
  attaches_to:
  - pathophysiology#Preserved Superficial Pupillomotor Function
  prompt: >-
    How far can the pupil-involving versus pupil-sparing distinction be trusted
    to separate compressive from ischaemic third nerve palsy?
  rationale: >-
    The anatomical premise is sound and the statistical association is strong:
    only 2% of aneurysmal palsies spare the pupil, and about three quarters of
    vasculopathic palsies do spare it. But the rule has documented failure modes
    in both directions. Pupil sparing occurs in a minority of compressive
    subarachnoid lesions and in a large proportion of cavernous sinus
    compressive lesions, and aberrant regeneration can manufacture apparent
    sparing. Conversely, about half of diabetic microvascular palsies in one
    large inpatient series did involve the pupil, which the author attributed to
    coexisting autonomic neuropathy. The rule should therefore be curated as a
    likelihood modifier, not a decision rule, and it does not transfer to
    children at all.
  status: OPEN
  evidence:
  - reference: PMID:6830173
    reference_title: "Pupil sparing in oculomotor palsy: a brief review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two case reports and a review of the literature disclose that pupil sparing occurs in a small proportion of intraaxial and compressive subarachnoid oculomotor nerve lesions and in a large proportion of compressive cavernous sinus oculomotor nerve lesions."
    explanation: "Documents the compressive lesions that nevertheless spare the pupil, the first failure mode of the rule."
  - reference: PMID:21059515
    reference_title: "Third nerve palsy: analysis of 1400 personally-examined inpatients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of 234 patients with diabetes, microvascular ischemia was the cause of TNP in only two-thirds (five had aneurysms) and 53% of those with diabetic microvascular ischemia had pupillary involvement-often bilateral, suggesting concomitant autonomic neuropathy."
    explanation: "Documents the opposite failure mode - microvascular palsy that does involve the pupil - in a majority of diabetic cases in this inpatient series."
  - reference: PMID:16391633
    reference_title: "Oculomotor nerve palsy in childhood."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Their pupillary signs, unlike those of adults, are not helpful in differentiating compressive etiologies from other causes."
    explanation: "Establishes that the rule does not apply in paediatric practice at all."
- discussion_id: pattern_of_motor_paresis_as_a_second_axis
  kind: EMERGING_HYPOTHESIS
  attaches_to:
  - pathophysiology#Somatic Motor Fibre Conduction Failure
  prompt: >-
    Can the spatial pattern of extraocular muscle weakness discriminate
    vasculopathic from aneurysmal palsy when the pupil is uninformative?
  rationale: >-
    If the pupil rule fails in exactly the cases where it is most needed, a
    second discriminator would be valuable. One series proposed that incomplete
    pupil-sparing vasculopathic palsies show diffuse weakness across all cranial
    nerve III muscles, whereas pupil-sparing aneurysmal palsies show focal
    weakness confined to some of them. The proposal follows naturally from the
    mechanism - diffuse endoneurial ischaemia versus focal external contact -
    but the authors were explicit that it needs confirmation, and no larger
    validation has been curated here.
  status: OPEN
  evidence:
  - reference: PMID:11756854
    reference_title: "Patterns of extraocular muscle weakness in vasculopathic pupil-sparing, incomplete third nerve palsy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We propose that distinguishing these two patterns of EOM paresis may be helpful in differentiating between vasculopathic and aneurysmal 3NP. Future studies will be needed to confirm the clinical utility of this hypothesis."
    explanation: "The authors state the hypothesis and its unvalidated status in their own words, which is why this is curated as EMERGING_HYPOTHESIS rather than as mechanism."
- discussion_id: rpon_mechanism_unresolved
  kind: KNOWLEDGE_GAP
  attaches_to:
  - pathophysiology#Focal Oculomotor Nerve Inflammation with Blood-Nerve Barrier Breakdown
  prompt: >-
    What is the primary lesion in recurrent painful ophthalmoplegic neuropathy -
    ischaemia, inflammation, demyelination, or compression?
  rationale: >-
    RPON was renamed away from "ophthalmoplegic migraine" precisely because the
    MRI appearance indicates a neuropathy, but the rename did not settle what
    causes the neuropathy. Competing hypotheses of nerve compression, ischaemia,
    and inflammation or demyelination are all still live, no histology is
    available, and treatment with corticosteroids has never been tested against
    the natural history of spontaneous remission. Because attacks are rare
    (5/633 in a large aetiological series) the gap is unlikely to close without
    a multicentre registry.
  status: OPEN
  proposed_experiments:
  - experiment_id: rpon_prospective_registry
    name: Prospective multicentre RPON registry with standardised acute imaging
    description: >-
      Enrol consecutive RPON attacks across centres with a fixed acute MRI
      protocol covering the cisternal nerve and root entry zone, repeated in
      remission, to establish whether enhancement resolves completely and
      whether it precedes or follows the ophthalmoplegia.
  evidence:
  - reference: PMID:36694449
    reference_title: "Recurrent Painful Ophthalmoplegic Neuropathy: A case report with atypical features and a review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Several hypotheses have been proposed, including nerve compression, ischemia or inflammation/demyelination, but none has been completely accepted."
    explanation: "States directly that no mechanism for RPON is established."
  - reference: PMID:35659705
    reference_title: "Diagnostic controversies in recurrent painful ophthalmoplegic neuropathy: single case report with a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There is no evidence supporting a specific treatment."
    explanation: "Confirms the therapeutic corollary of the mechanistic gap."
- discussion_id: scope_boundary_congenital_dysinnervation
  kind: INTERPRETATION
  attaches_to:
  - pathophysiology#Congenital Oculomotor Nerve Hypoplasia or Aplasia
  prompt: >-
    Should congenital fibrosis of the extraocular muscles and the other
    congenital cranial dysinnervation disorders be curated inside this entry?
  rationale: >-
    They should not. CFEOM (KIF21A, TUBB3, TUBA1A, PHOX2A) and the wider CCDD
    group are distinct, separately named genetic entities with their own MONDO
    identifiers, and the large aetiological series that anchors this entry
    explicitly excluded congenital cranial dysinnervation disorders when
    assigning its congenital category. The congenital subtype curated here is
    isolated congenital oculomotor nerve palsy with imaging-demonstrated nerve
    hypoplasia, thinning, or agenesis. The distinction is recorded because a
    deep-research report generated for this entry did bundle CFEOM genetics
    into it, and that content was deliberately not imported.
  status: RESOLVED
  resolution_note: >-
    Scope fixed to acquired and isolated congenital oculomotor nerve palsy;
    CFEOM and CCDD genetics excluded and left to their own entries.
  evidence:
  - reference: PMID:38411317
    reference_title: "Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Congenital oculomotor nerve palsy was diagnosed when the patients had an infantile onset of ophthalmoplegia after excluding congenital cranial dysinnervation disorders, such as Duane syndrome and congenital Horner syndrome"
    explanation: "The anchoring series states its own exclusion of congenital cranial dysinnervation disorders, which is the boundary this entry adopts."
notes: >-
  Curation scope. This entry models the oculomotor nerve palsy syndrome
  (MONDO:0001309) as an aetiologically heterogeneous convergence on one motor
  and one autonomic deficit, organised around the somatotopic segregation of
  the nerve's fibres. Related entries in the knowledge base that intersect it
  are Intracranial_Berry_Aneurysm, which carries oculomotor nerve palsy as a
  phenotype of the aneurysm rather than as a disease in its own right, and
  Bells_Palsy, the analogous single-cranial-nerve entry for cranial nerve VII;
  neither is duplicated here. Congenital cranial dysinnervation disorders
  (CFEOM, Duane retraction syndrome) are deliberately out of scope - see the
  scope_boundary_congenital_dysinnervation discussion.

  Deep research. `just research-disorder falcon Oculomotor_Nerve_Palsy` was run
  on 2026-08-20 (research/Oculomotor_Nerve_Palsy-deep-research-falcon.md).
  `just preflight-dr` returned SKIP, as expected for an acquired syndrome for
  which MONDO records no causal gene, so the manual named-entity-confusion
  checks in CLAUDE.md section 2b were performed instead: the MONDO record
  (`runoak -i sqlite:obo:mondo info MONDO:0001309 -O obo`) carries no causal
  gene and no OMIM xref, its synonyms are all plain restatements of "third
  nerve palsy" with no competing eponym, and the report explicitly names
  MONDO:0001309 and the correct clinical entity. The report was judged not to
  be a named-entity confusion, but its top gene mentions (TUBB3, KIF21A,
  TUBA1A, PHOX2A, CHN1) revealed a scope drift into congenital cranial
  dysinnervation disorders; that material was excluded. The report was used as
  leads only, and every PMID and snippet in this entry was independently
  fetched and verified against the local reference cache.

  Clinical trials. No clinical_trials block is curated, and the omission is
  deliberate rather than an oversight. The deep-research run surfaced three
  registrations: NCT03099447 and NCT03461809 are acupuncture studies whose
  registry status is UNKNOWN with no posted results, and NCT03059420 is a
  congenital cranial dysinnervation disorder genetics registry that falls
  inside the scope boundary this entry draws. None of the three would support
  an evidence-bearing claim about this syndrome today.

  Anatomical provenance. The peripheral position of the pupillomotor fibres
  traces to Kerr and Hollowell's experimental work (PMID:14213479) and to
  Sunderland and Hughes. Neither has a retrievable abstract in the reference
  cache, so neither is quoted as evidence; the claim is instead anchored on
  contemporary sources whose text can be verified.

📚

References & Deep Research

Deep Research

1

Falcon ▸

Oculomotor Nerve Palsy: Disease-Characteristics Research Report

Edison Scientific Literature 43 citations 2026-08-20T07:25:50.181692

Oculomotor Nerve Palsy: Disease-Characteristics Research Report

Scope. Oculomotor nerve palsy (ONP; third cranial nerve palsy) is a clinical syndrome rather than one etiologically uniform disease. This report distinguishes (1) common acquired CN III palsy from (2) congenital oculomotor dysinnervation, especially congenital fibrosis of the extraocular muscles (CFEOM). Evidence is disease-level and aggregated unless explicitly labeled as a case series, registry record, or model-organism result.

Executive summary

CN III supplies the levator palpebrae superioris, superior/medial/inferior recti, inferior oblique, and parasympathetic fibers to the iris sphincter and ciliary muscle. Accordingly, complete palsy causes ptosis, a “down-and-out” eye, severe ophthalmoplegia and binocular diplopia, with variable mydriasis and impaired accommodation. New acquired palsy is a diagnostic emergency because a posterior communicating artery (PComA) aneurysm can compress the nerve; pupil sparing reduces but does not eliminate that possibility.

The best recent etiologic study, a 2024 referral-center cohort of 633 isolated cases, found microvascular disease in 26.5%, vascular anomalies in 17.4%, neoplasm in 13.6%, inflammation in 12.5%, idiopathic disease in 9.5%, and trauma in 8.4%. Intracranial aneurysms comprised 89/110 vascular anomalies. The cohort was 99.2% unilateral and had a median age of 59 years, but referral bias limits population inference. (kim2024etiologicaldistributionof pages 4-7, kim2024etiologicaldistributionof pages 3-4, kim2024etiologicaldistributionof pages 2-3)

Congenital disease belongs chiefly to the congenital cranial dysinnervation disorders. Dominant missense variants in KIF21A, TUBB3, and rarely TUBA1A disrupt microtubule behavior, kinesin interactions, or axon guidance; biallelic loss-of-function variants in PHOX2A cause CFEOM2. These developmental disorders are non-progressive but may cause amblyopia, corneal injury, abnormal head posture, and syndromic neurologic abnormalities. (fritzsch2023evolutionanddevelopment pages 16-18, puri2023tubb3andkif21a pages 1-2, jurgens2021novelvariantsin pages 1-2)

The following table maps the highest-yield evidence.

domain	key finding/statistic	evidence type and population	source/date/URL	caveat
Acquired etiology	In 633 patients with isolated oculomotor nerve palsy, etiologies were microvascular 26.5%, vascular anomalies 17.4%, neoplastic 13.6%, inflammatory 12.5%, idiopathic 9.5%, traumatic 8.4%; congenital 4.1%; infectious 1.9%. MRI was performed in 96.1%; incidence showed peaks before age 10 and in the 60s; men:women 1.3:1. (kim2024etiologicaldistributionof pages 1-2, kim2024etiologicaldistributionof pages 4-7, kim2024etiologicaldistributionof pages 3-4, kim2024etiologicaldistributionof pages 2-3)	Retrospective referral-hospital cohort; human clinical; n=633 isolated CN III palsy cases	Kim et al., Eur J Neurol (Feb 2024), doi:10.1111/ene.16261, https://doi.org/10.1111/ene.16261	Referral bias likely; single-center retrospective study; incidence estimate cited in paper but not population-based within this cohort.
Recovery/prognosis	In 65 CN III palsy cases, ischemic and compressive etiologies were most common (24.6% each). Complete recovery rates: ischemic 9/16, compressive 1/16, trauma 5/13, inflammation 6/10, idiopathic 2/10. Better long-term outcome associated with symptom onset <7 days and isolated nerve involvement. (srimanan2024retrospectiveanalysisof pages 2-4, srimanan2024retrospectiveanalysisof pages 6-7)	Retrospective tertiary-hospital cohort; human clinical; n=65 CN III palsy cases within larger ocular motor palsy study	Srimanan & Panyakorn, Clin Ophthalmol (Feb 2024), doi:10.2147/OPTH.S449127, https://doi.org/10.2147/OPTH.S449127	Single-center; mixed referral population; prognostic modeling includes all third/fourth/sixth nerve palsies, though CN III data are reported separately.
Congenital genetics / MRI	In 122 CCDD patients from 96 families, all had restrictive eye movements; 47.9% had multiple congenital malformations. MRI in 94 patients showed cranial-nerve hypoplasia in essentially all except HGPPS cases; 17.0% had additional craniocerebral malformations. WES found 10 pathogenic variants in KIF21A, TUBB3, and CHN1 across 43 families; novel variants included KIF21A p.F355S, TUBB3 p.S78T, CHN1 p.H217R. In CFEOM, mutation detection was 63.6% (42/66), with KIF21A 73.8% and TUBB3 26.2% among solved CFEOM probands. (jia2022clinicalandgenetic pages 1-2, jia2022clinicalandgenetic pages 7-8, jia2022clinicalandgenetic pages 12-13, jia2022clinicalandgenetic pages 13-14)	Cohort with MRI + whole-exome sequencing; human congenital cranial dysinnervation disorders; n=122	Jia et al., Orphanet J Rare Dis (Dec 2022), doi:10.1186/s13023-022-02582-5, https://doi.org/10.1186/s13023-022-02582-5	CCDD cohort, not isolated acquired CN III palsy; data most directly inform congenital oculomotor dysinnervation/CFEOM.
Developmental mechanism	Pathogenic TUBB3 missense variants alter microtubule dynamics and cranial axon guidance; pathogenic KIF21A missense variants alter kinesin function and can phenocopy TUBB3 variants. CFEOM reflects hypoplasia of the oculomotor nerve with failed superior-division innervation of levator palpebrae superioris and superior rectus. (puri2023tubb3andkif21a pages 1-2, puri2023tubb3andkif21a pages 2-3, puri2023tubb3andkif21a pages 3-5)	Review synthesizing human genetics, MRI, in vitro and mouse studies	Puri, Barry & Engle, Front Neurosci (4 Aug 2023), doi:10.3389/fnins.2023.1226181, https://doi.org/10.3389/fnins.2023.1226181	Mechanistic synthesis, not a treatment or epidemiology study; focuses on congenital disease biology rather than common acquired palsy.
Additional causal gene	Three unrelated probands with CFEOM had novel heterozygous TUBA1A missense variants: c.1216C>G p.His406Asp, c.467G>A p.Arg156His, c.1193T>G p.Met398Arg. MRI showed small oculomotor-innervated muscles and asymmetric caudate/lateral ventricular abnormalities; 2/3 also had malformations of cortical development. (jurgens2021novelvariantsin pages 1-2, jurgens2021novelvariantsin pages 9-10)	Primary sequencing study; human congenital CFEOM/tubulinopathy; n=3 probands	Jurgens et al., Eur J Hum Genet (1 Mar 2021 online), doi:10.1038/s41431-020-00804-7, https://doi.org/10.1038/s41431-020-00804-7	Very small case series; supports rare congenital etiology only.
Clinical trial / acupuncture	Randomized parallel triple-masked interventional trial in ONP; estimated enrollment 177. Compared ocular electroacupuncture vs ocular acupuncture vs sham acupuncture over 6 weeks; primary outcome was change in ocular motor nerve function subscale at 6 weeks. Last known status: RECRUITING; overall registry status listed as UNKNOWN. (NCT03099447 chunk 1, NCT03099447 chunk 2)	ClinicalTrials.gov registry entry; interventional; adults with complete ONP	NCT03099447, first posted 4 Apr 2017, https://clinicaltrials.gov/study/NCT03099447	Registry record only; no posted results in provided context; efficacy remains unproven here.
Clinical trial / retrospective acupuncture cohort	Observational retrospective cohort of ocular motor nerve palsy treated by ocular acupuncture; estimated enrollment 900; includes oculomotor, trochlear, and abducens palsy. Primary outcome: investigator-assessed clinical efficacy rate; last known status NOT_YET_RECRUITING, overall status UNKNOWN. (NCT03461809 chunk 1)	ClinicalTrials.gov registry entry; observational retrospective cohort	NCT03461809, first posted 12 Mar 2018, https://clinicaltrials.gov/study/NCT03461809	Mixed ocular motor palsies; registry-only description; no posted outcomes in context.
Clinical trial / genetics registry	Large observational genetics study of strabismus/CCDDs and related anomalies; estimated enrollment 20,000; recruiting. Includes Third Nerve Palsy, Fourth Nerve Palsy, Sixth Nerve Palsy, CFEOM, DRS, Möbius, HGPPS, and related phenotypes; biospecimens include DNA. Primary outcome is gene discovery/characterization. (NCT03059420 chunk 1, NCT03059420 chunk 2)	ClinicalTrials.gov registry entry; observational genetics cohort	NCT03059420, recruiting; first posted 23 Feb 2017; updated 11 Feb 2026, https://clinicaltrials.gov/study/NCT03059420	Broad congenital cranial dysinnervation/strabismus study, not specific to isolated acquired CN III palsy; observational, not therapeutic.

Table: This table compacts the highest-yield evidence identified for oculomotor nerve palsy, separating common acquired clinical data from rarer congenital genetic mechanisms and ongoing registry studies. It is useful as a source map for etiology, prognosis, molecular biology, and current trial activity.

1. Disease information

Definition and identifiers

Preferred name: oculomotor nerve palsy/paralysis.
Synonyms: third nerve palsy, third cranial nerve palsy, CN III palsy, oculomotor neuropathy, oculomotor nerve paralysis; “external ophthalmoplegia” may describe motor involvement without parasympathetic dysfunction but is not fully synonymous.
MONDO: MONDO:0001309, “oculomotor nerve paralysis.” Open Targets maps this term to MONDO_0001309; its automated target associations should not be interpreted as a curated causal-gene list for ordinary acquired CN III palsy. (OpenTargets Search: oculomotor nerve palsy)
MeSH: D015840, Oculomotor Nerve Diseases. ClinicalTrials.gov also maps diplopia to D004172 and ocular motility disorders to D015835. (NCT03099447 chunk 1)
ICD-10-CM: commonly coded under H49.0- (third [oculomotor] nerve palsy; laterality-specific extensions). Local coding systems should be checked before database ingestion.
ICD-11: falls within paralytic strabismus/ocular motor nerve palsy classifications; an exact leaf code was not verified in the retrieved primary sources.
OMIM/Orphanet: there is no single etiologically adequate OMIM entry for all ONP. Congenital subtypes should instead be represented by their syndrome entries—CFEOM1/KIF21A, CFEOM2/PHOX2A, CFEOM3/TUBB3—and gene-disease records. CFEOM is MeSH C580012 in the trial-derived ontology. (NCT03059420 chunk 2)

Clinical concept

CN III dysfunction is diagnosed by weakness of its innervated extraocular muscles, with or without ptosis or pupillary involvement. A 2024 study operationalized ONP as exotropia, vertical misalignment and/or ptosis, with or without pupillary involvement. (srimanan2024retrospectiveanalysisof pages 2-4)

2. Etiology, risk factors, and protective factors

Acquired causes

The 2024 cohort reported microvascular 168/633 (26.5%), vascular anomaly 110/633 (17.4%), neoplastic 86/633 (13.6%), inflammatory 79/633 (12.5%), idiopathic 60/633 (9.5%), traumatic 53/633 (8.4%), stroke/other vascular 4.4%, congenital 4.1%, and infectious 1.9%. Primary CNS tumors included meningioma and pituitary adenoma, each 24/69 primary tumors; vascular anomalies included aneurysm 89/110, dural arteriovenous fistula 10/110, cavernous malformation 9/110, and AVM 2/110. (kim2024etiologicaldistributionof pages 4-7, kim2024etiologicaldistributionof pages 3-4)

Additional causes include midbrain infarction or hemorrhage, cavernous-sinus/orbital-apex disease, Tolosa–Hunt syndrome, demyelination, recurrent painful ophthalmoplegic neuropathy, Miller Fisher syndrome, neurosurgical/iatrogenic injury, and infections affecting nerve, meninges, cavernous sinus, or orbital apex. The cited cohort required pathogen-compatible serology/CSF for infectious classification and MRI lesions plus steroid responsiveness for presumed inflammatory disease. (kim2024etiologicaldistributionof pages 2-3)

Risk factors

Microvascular: older age, diabetes mellitus, hypertension, dyslipidemia, and smoking. In the 2024 study, microvascular palsy required acute onset, at least one such risk factor, no explanatory MRI lesion, and spontaneous recovery within one year. (kim2024etiologicaldistributionof pages 2-3)
Aneurysmal/compressive: female sex and intracranial-aneurysm risk factors are relevant at the population level. In the 633-person series, vascular anomalies were more frequent in women (27.1%) than men (9.6%). (kim2024etiologicaldistributionof pages 4-7)
Trauma: head injury, including road-traffic injury; trauma predominates more strongly in younger patients.
Inflammatory/infectious: systemic inflammatory disease, immunosuppression, meningitis, cavernous-sinus infection, and relevant regional pathogens.
Genetic: pathogenic variants causing CFEOM/CCDDs; these are causes of congenital dysinnervation rather than susceptibility alleles for typical late-onset ischemic palsy.

Protective factors and gene–environment interaction

No replicated genetic protective variant specific to ONP was identified. Environmental protection is therefore inferred from cause prevention: control blood pressure, diabetes and lipids; stop smoking; prevent head injury; promptly treat infection; and manage aneurysm risk. Evidence for a CN III-specific diet, supplement, or exercise regimen is absent.

The clearest gene–environment framework is not a proven locus interaction but reduced neural-repair reserve with aging plus vascular or traumatic injury. Generic peripheral-nerve mouse experiments show that aging and chronic denervation reduce Schwann-cell c-Jun and regenerative support; restoring c-Jun normalized regeneration. This is biologically relevant but indirect evidence, not a demonstrated CN III intervention. (wagstaff2021failuresofnerve pages 1-2)

3. Phenotypes

Phenotype	Type/course	Suggested HPO term
Ptosis	Clinical sign; partial or complete; congenital or acute	HP:0000508 Ptosis; congenital ptosis HP:0007911
Binocular diplopia	Symptom; acute in acquired ONP; disappears when either eye is covered	HP:0000651 Diplopia
External ophthalmoplegia	Sign; impaired adduction, elevation and depression; severity variable	HP:0000544 External ophthalmoplegia
Exotropia/hypotropia, “down-and-out” eye	Physical sign from unopposed lateral rectus/superior oblique	HP:0000577 Exotropia, HP:0000545 Myopia is not appropriate; use strabismus HP:0000486 plus vertical deviation annotation
Mydriasis/anisocoria	Parasympathetic sign; may be absent	HP:0011499 Anisocoria, HP:0000554 Tonic pupil only if specifically established
Impaired pupillary light response/accommodation	Functional sign	HP:0007686 Abnormal pupillary function
Periorbital pain/headache	Symptom, particularly aneurysmal or inflammatory disease	HP:0002315 Headache, HP:0100608 Miosis should not be used for typical compressive ONP
Aberrant regeneration/synkinesis	Late sign after severe injury; lid elevation or pupil constriction with attempted gaze	HP:0012378 Abnormal eye movement; add synkinesis concept where supported
CFEOM	Congenital, non-progressive restrictive ophthalmoplegia with ptosis	HP:0001491 CFEOM, HP:0007911 congenital ptosis
Amblyopia	Pediatric complication of misalignment/ptosis	HP:0000646 Amblyopia

In the 633-person acquired/congenital cohort, 628/633 (99.2%) were unilateral and five were bilateral; right and left sides were approximately equal. Age ranged from 2 months to 85 years, with peaks before age ten and in the 60s. (kim2024etiologicaldistributionof pages 2-3)

CFEOM is defined by congenital ptosis and non-progressive paralytic strabismus, particularly restricted upgaze, with variable restriction of down- and horizontal gaze. The eye cannot be moved actively or passively into restricted positions because chronic dysinnervation produces secondary muscle fibrosis. Long-term effects include amblyopia, corneal injury, and neck/back discomfort from compensatory head posture. (puri2023tubb3andkif21a pages 1-2)

Quality of life. Diplopia impairs reading, driving, mobility, depth judgment, work, and fall safety; ptosis impairs the superior visual field; congenital disease affects visual development and posture. No robust ONP-specific EQ-5D or SF-36 population estimates were found. The acupuncture trial planned a physical/psychological ONP quality-of-life questionnaire but has no results in the retrieved registry. (NCT03099447 chunk 1)

4. Genetic and molecular information

Causal genes in congenital disease

KIF21A: usually heterozygous missense, autosomal dominant or de novo; principally CFEOM1. Variants weaken motor-domain/stalk autoinhibition, causing excessive microtubule interaction and oculomotor axon stalling. Mouse knock-in models reproduce stalled CN III axons and hypoplastic target muscles. (fritzsch2023evolutionanddevelopment pages 16-18, puri2023tubb3andkif21a pages 3-5)
TUBB3: heterozygous, often de novo missense variants; CFEOM3 or broader tubulinopathy. Variants alter microtubule dynamics, kinesin binding and axon guidance. Recurrent substitutions include p.Arg262Cys/His, p.Ala302Thr, p.Arg380Cys, p.Glu410Lys and p.Asp417Asn; syndromic findings may include facial weakness, axonal neuropathy, joint contractures, neurodevelopmental impairment and white-matter/basal-ganglia malformations. (puri2023tubb3andkif21a pages 1-2, puri2023tubb3andkif21a pages 2-3, puri2023tubb3andkif21a pages 3-5)
PHOX2A: biallelic loss-of-function, autosomal recessive CFEOM2; defective specification/survival of oculomotor and trochlear motor neurons. Mouse loss causes absent CN III/IV nuclei and nerves. (fritzsch2023evolutionanddevelopment pages 16-18)
TUBA1A: rare heterozygous missense CFEOM/tubulinopathy. Three reported variants are c.1216C>G p.His406Asp, c.467G>A p.Arg156His and c.1193T>G p.Met398Arg. Residues affect α/β-tubulin longitudinal or protofilament lateral interfaces; two of three probands had cortical malformations. PMID 33649541, published online March 1, 2021; https://doi.org/10.1038/s41431-020-00804-7. (jurgens2021novelvariantsin pages 1-2, NCT03059420 chunk 2)
Other CCDD genes can create overlapping ocular-motor phenotypes: TUBB2B, CHN1, ECEL1, MYF5, COL25A1, MAFB, SALL4, HOXA1, ROBO3, ACKR3/CXCR7 and others. They should not automatically be labeled as isolated CN III-palsy genes. Open Targets associations such as MAPT largely reflect phenotype/text-mining links and are not evidence that MAPT causes ordinary acquired ONP. (OpenTargets Search: oculomotor nerve palsy, NCT03059420 chunk 2)

Human sequencing evidence

In 122 Chinese patients from 96 CCDD families, WES detected ten pathogenic variants in KIF21A, TUBB3, or CHN1 across 43 families. Novel variants included KIF21A c.1064T>C p.Phe355Ser, TUBB3 c.232T>A p.Ser78Thr, and CHN1 c.650A>G p.His217Arg. CFEOM’s molecular diagnostic rate was 42/66 (63.6%) and 100% in familial cases; among solved CFEOM families, 31/42 involved KIF21A and 11/42 TUBB3. (jia2022clinicalandgenetic pages 1-2, jia2022clinicalandgenetic pages 7-8)

Variants were filtered against population databases including gnomAD with a >1% MAF exclusion threshold and validated by Sanger sequencing/segregation. Exact gnomAD allele frequencies and ClinVar accessions for each variant were not available in the retrieved text and must be obtained variant-by-variant before production annotation. (jia2022clinicalandgenetic pages 13-14)

No validated modifier genes, characteristic somatic variants, DNA-methylation signature, chromosomal abnormality, or ONP-specific epigenetic mechanism is established. Germline variants dominate congenital disease; acquired palsy is generally non-genetic and lesion-based.

5. Environmental, lifestyle and infectious information

Relevant non-genetic exposures include head trauma, neurosurgical/endovascular procedures, smoking and vascular-metabolic exposures. No consistent toxin, radiation, occupational exposure, alcohol dose, nutritional deficiency, or pollution association specific to isolated ONP was verified.

Infectious mechanisms include meningitis, direct neuritis, vasculitis, cavernous-sinus thrombosis and orbital-apex inflammation. The 2024 series attributed 12/633 (1.9%) cases to infection using compatible clinical, serologic and CSF evidence. Pathogens are heterogeneous; no single organism defines the disease. (kim2024etiologicaldistributionof pages 3-4, kim2024etiologicaldistributionof pages 2-3)

6. Mechanism and pathophysiology

Acquired causal chains

Microvascular: diabetes/hypertension/dyslipidemia/smoking → small-vessel injury and endoneurial ischemia → focal demyelination/axonal dysfunction of CN III → ophthalmoplegia, ptosis and diplopia. Superficial pupillomotor fibers may be relatively spared, but pupil sparing is not an absolute discriminator.
Compressive aneurysm: PComA aneurysm enlargement/rupture → mechanical deformation and compromised perfusion of the nearby cisternal CN III → preferential superficial parasympathetic-fiber injury → painful ophthalmoplegia with mydriasis, potentially followed by subarachnoid hemorrhage. The cisternal nerve lies about 1.7 mm from PComA in cited anatomical synthesis. (ge2025oculomotornervepalsy pages 2-3)
Tumor/inflammation/cavernous sinus: mass, infiltrate, granulomatous inflammation or thrombosis → fascicular compression, inflammation and impaired conduction; neighboring CN IV, V1/V2 or VI deficits indicate regional extension.
Trauma: stretch, shear, contusion or avulsion → axonal disruption/Wallerian degeneration → incomplete or misdirected reinnervation and possible synkinesis.
Congenital: pathogenic KIF21A/tubulin/PHOX2A alteration → abnormal motor-neuron specification or microtubule-dependent axon extension/targeting → hypoplastic CN III divisions and denervated extraocular muscles → secondary muscle hypoplasia/fibrosis, ptosis and fixed strabismus. (puri2023tubb3andkif21a pages 1-2, jurgens2021novelvariantsin pages 1-2)

Cellular/molecular annotations

Suggested biological-process terms include GO:0007409 axonogenesis, GO:0007411 axon guidance, GO:0031175 neuron projection development, GO:0007017 microtubule-based process, GO:0007018 microtubule-based movement, GO:0042552 myelination, GO:0048679 regulation of axon regeneration, and GO:0008219 cell death. Relevant cell types include oculomotor motor neuron, parasympathetic preganglionic neuron, Schwann cell (CL:0002573), macrophage (CL:0000235), vascular endothelial cell (CL:0000115), and extraocular skeletal myocyte.

Generic peripheral-nerve injury studies support NMNAT2 depletion followed by SARM1 NADase activation as an upstream programmed-axon-death mechanism; downstream Schwann-cell dedifferentiation, c-JUN activation, myelinophagy, macrophage recruitment, Büngner-band formation, axon regrowth and remyelination support repair. The review states that “NMNAT2 and SARM1 are required for axon survival and degeneration, respectively.” These pathways have not been molecularly profiled specifically in human CN III palsy. (arthurfarraj2021lessonsfrominjury pages 1-2)

A direct mouse experiment found that aging/chronic denervation reduced Schwann-cell c-Jun and that genetic restoration “restores regeneration to control levels.” This is model-organism evidence, not a clinical therapy. (wagstaff2021failuresofnerve pages 1-2)

No reproducible CN III-specific transcriptomic, proteomic, metabolomic, lipidomic, single-cell, spatial-transcriptomic or multi-omic signature was identified. This is a major research gap.

7. Anatomical structures affected

Nucleus/fascicle: oculomotor nuclear complex and Edinger–Westphal region in the midbrain; fascicles traverse the tegmentum.
Cisternal segment: exits ventral midbrain, passes between posterior cerebral and superior cerebellar arteries and near PComA.
Cavernous sinus/superior orbital fissure/orbit: lesions here may involve other ocular motor or trigeminal nerves.
Targets: levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, inferior oblique; ciliary ganglion, iris sphincter and ciliary muscle.
Secondary tissues: cornea from exposure, visual cortex/visual development through amblyopia, and cervical musculoskeletal structures from abnormal head posture.

Suggested UBERON annotations: oculomotor nerve (CN III), midbrain, cavernous sinus, orbit, extraocular muscle, ciliary ganglion, iris and cornea. Exact UBERON accessions should be resolved against the production ontology release. Subcellular compartments particularly relevant to congenital disease are the microtubule cytoskeleton (GO:0015630), kinesin complex, axon and growth cone.

CFEOM MRI shows hypoplastic CN III and underdeveloped superior rectus/levator muscles, with variable inferior-division and CN VI involvement. TUBB3 variants may additionally cause corpus-callosum, anterior-commissure, basal-ganglia, thalamic, brainstem and cerebellar abnormalities. (puri2023tubb3andkif21a pages 1-2, puri2023tubb3andkif21a pages 3-5)

8. Temporal development

Acquired palsy usually begins acutely or subacutely. Aneurysmal palsy and associated pain can evolve over hours to days; microvascular palsy is typically acute; tumors may be progressive; inflammatory disease may fluctuate or relapse. Congenital palsy/CFEOM is present from infancy and generally non-progressive, although secondary fibrosis, amblyopia and postural complications evolve over time.

Microvascular recovery usually occurs over weeks to months; absence of improvement by roughly 12 weeks, progression, new neurologic signs or recurrence requires diagnostic reconsideration. In a 2024 hospital cohort, complete recovery occurred in 9/16 ischemic, 1/16 compressive, 5/13 traumatic, 6/10 inflammatory and 2/10 idiopathic CN III cases. Across ocular motor palsies, onset documented within seven days and isolated nerve involvement predicted better outcome. (srimanan2024retrospectiveanalysisof pages 6-7)

9. Inheritance and population epidemiology

Published population estimates place acquired ONP incidence at approximately 3.7–4.0 per 100,000 person-years. Incidence rises markedly with age. The 633-case referral cohort had median age 59 years, male:female ratio 1.3:1 and dual age peaks before age ten and in the 60s; these distributions should not be treated as population prevalence. (kim2024etiologicaldistributionof pages 1-2, kim2024etiologicaldistributionof pages 2-3)

Acquired ONP is usually sporadic and multifactorial. CFEOM1/KIF21A and many TUBB3/TUBA1A disorders are autosomal dominant, often de novo, with variable expressivity. PHOX2A-related CFEOM2 is autosomal recessive; consanguinity therefore increases risk. Penetrance is high for classic familial CFEOM but exact variant-specific estimates differ. Genetic anticipation is not established. Germline mosaicism is theoretically relevant after an apparently de novo result but was not quantified. Founder variants and carrier frequencies are not adequately defined in the retrieved evidence.

10. Diagnostics

Immediate clinical assessment

Document onset, pain/headache, trauma, vascular risks, cancer/infection/inflammatory history and neurologic symptoms. Examine visual acuity, fields, pupils in light/dark, eyelid position, ductions, alignment, fundus and all cranial nerves. Determine complete versus partial, pupil-involving versus pupil-sparing, isolated versus non-isolated and congenital versus acquired disease.

Emergency principle: a new acquired CN III palsy—especially painful, pupil-involving, partial/progressive, or occurring in a young patient without vascular risks—requires urgent vascular imaging for aneurysm. Modern CTA or MRA is first-line; catheter angiography is reserved for unresolved high suspicion or intervention planning. Pupil sparing alone should not be used to defer imaging.

MRI brain/orbits with and without gadolinium, thin sections along CN III, diffusion-weighted imaging, and MRA evaluates midbrain infarction, nerve enhancement, cavernous sinus, orbital apex and tumor. In the 2024 etiologic cohort, MRI was obtained in 608/633 (96.1%). (kim2024etiologicaldistributionof pages 2-3)

Laboratory and ancillary tests

Testing is hypothesis-driven: glucose/HbA1c, blood pressure, lipids, CBC/chemistry, ESR/CRP in older patients where giant-cell arteritis is plausible, infectious serology/CSF when indicated, thyroid studies, acetylcholine-receptor/MuSK antibodies for myasthenia, and lumbar puncture for meningitis/inflammation/malignancy when imaging and context warrant. EMG has limited routine value for CN III but may help characterize extraocular muscle denervation in specialist centers.

Genetic testing

For congenital non-progressive ptosis/ophthalmoplegia, obtain high-resolution cranial-nerve/orbital MRI and a CCDD/CFEOM panel including KIF21A, TUBB3, PHOX2A, TUBA1A, TUBB2B, CHN1, ECEL1, MYF5, COL25A1, MAFB, SALL4, HOXA1, ROBO3 and phenotype-driven genes. Trio WES/GS is appropriate after a negative panel or in syndromic cases; CNV analysis should accompany sequencing. CMA/karyotype/FISH are reserved for multiple congenital anomalies or suspected chromosomal disease. Mitochondrial and repeat-expansion testing are not routine unless the broader phenotype suggests them. MRI plus WES achieved a 63.6% molecular diagnosis in the reported CFEOM cohort. (jia2022clinicalandgenetic pages 7-8)

Differential diagnosis

Exclude myasthenia gravis, thyroid eye disease, orbital myositis/mass, restrictive strabismus, skew deviation, internuclear ophthalmoplegia, dorsal midbrain syndrome, Horner syndrome, Adie pupil, pharmacologic mydriasis, CPEO/mitochondrial disease, Miller Fisher syndrome and recurrent painful ophthalmoplegic neuropathy. Proptosis, chemosis, sensory loss, optic neuropathy or multiple cranial neuropathies localize away from an isolated nerve lesion.

There is no general-population or newborn screening program. Cascade genetic testing is appropriate after identifying a pathogenic congenital variant.

11. Outcome and prognosis

ONP itself generally does not reduce life expectancy; mortality is determined by the underlying aneurysm, stroke, malignancy, infection or trauma. Therefore, disease-specific five- or ten-year survival statistics are not meaningful for ONP as a syndrome.

A 2020 tertiary-center series reported complete or partial recovery in 69.7% of acquired third-nerve palsies, but setting and etiologic composition constrain generalization. The 2024 etiology-specific complete-recovery figures demonstrate that inflammatory and ischemic palsies fare better than compressive disease. (srimanan2024retrospectiveanalysisof pages 2-4, srimanan2024retrospectiveanalysisof pages 6-7)

Poor prognostic features include complete palsy, severe axonal injury, compressive/neoplastic etiology, multiple cranial nerves, delayed treatment of the cause, prolonged denervation and aberrant regeneration. Persistent diplopia, ptosis, fixed strabismus, amblyopia, exposure keratopathy and synkinesis are the main disabilities. No validated molecular prognostic biomarker exists.

12. Treatment and current applications

Cause-directed treatment

PComA/intracranial aneurysm: urgent neurosurgical/endovascular assessment; clipping, coiling, stent/balloon-assisted coiling or flow diversion according to rupture status and anatomy. The purpose is prevention/treatment of hemorrhage and decompression or exclusion of the aneurysm—not merely ocular realignment.
Microvascular palsy: observation after adequate imaging/evaluation, vascular-risk control, analgesia and temporary diplopia treatment. There is no proven drug that accelerates CN III regeneration.
Inflammatory disease: corticosteroids or disease-specific immunotherapy only after excluding infection and defining the disorder. The 2024 cohort used oral corticosteroid 1 mg/kg/day for at least two weeks with taper in inflammatory cases, but this was not randomized evidence. (srimanan2024retrospectiveanalysisof pages 2-4)
Infection/cavernous-sinus thrombosis: organism-directed antimicrobial therapy and source control; anticoagulation according to the underlying thrombosis protocol.
Tumor: surgery, radiation or systemic therapy according to pathology and location.
Trauma: treat associated injuries, protect the eye, observe for recovery, then rehabilitate alignment.

Suggested NCIt concepts include aneurysm clipping, endovascular coil embolization, corticosteroid therapy, antimicrobial therapy, radiation therapy, strabismus surgery, botulinum toxin injection, prism therapy, and occlusion therapy; exact NCIt codes should be resolved in the current release.

Symptomatic and rehabilitative treatment

Temporary occlusion, fogging or Fresnel prisms may reduce diplopia; prisms are often limited by large incomitant deviations. Lubrication and corneal protection are used if eyelid closure or corneal sensation is compromised. Botulinum toxin to the antagonist lateral rectus is sometimes used in selected partial/acute palsies, but evidence is heterogeneous and it can cause ptosis or vertical deviation.

After alignment stabilizes, strabismus surgery may combine lateral-rectus weakening, medial-rectus strengthening, transposition or globe-fixation procedures. Ptosis repair is delayed until alignment and corneal-protection risks are addressed. Surgery improves primary-position alignment more reliably than full motility; repeated procedures may be required. CFEOM surgery is similarly individualized and does not restore normal innervation.

No approved gene, cell, RNA, CRISPR or regenerative therapy exists for ONP. Pharmacogenomic guidance is not established.

Trials

NCT03099447: randomized, parallel, triple-masked ocular electroacupuncture versus acupuncture versus sham; estimated n=177, six weeks. Registry status is UNKNOWN (last known recruiting), and no results were available; efficacy remains unproven. https://clinicaltrials.gov/study/NCT03099447. (NCT03099447 chunk 1)
NCT03461809: retrospective acupuncture cohort across CN III/IV/VI palsies, estimated n=900; status UNKNOWN, with no posted results in the retrieved record. https://clinicaltrials.gov/study/NCT03461809. (NCT03461809 chunk 1)
NCT03059420: recruiting Boston Children’s/Howard Hughes observational genetics cohort, estimated n=20,000, including CFEOM and third-nerve palsy; not a treatment trial. https://clinicaltrials.gov/study/NCT03059420. (NCT03059420 chunk 1, NCT03059420 chunk 2)

13. Prevention

Primary: control diabetes, hypertension and dyslipidemia; stop smoking; use seatbelts/helmets and fall/occupational injury prevention; manage infection and aneurysm risk according to established disease-specific guidance.
Secondary: urgent recognition and CTA/MRA of new acquired palsy to prevent aneurysmal rupture or identify treatable tumor, stroke, infection or inflammation. There is no evidence-based screening of asymptomatic average-risk people for ONP.
Tertiary: prevent amblyopia in children, corneal exposure, falls and driving injury; use temporary diplopia control, rehabilitation and delayed alignment surgery.
Genetic: counseling, cascade testing, and reproductive options—including prenatal or preimplantation testing—are appropriate only after a familial pathogenic variant is established. No vaccine specifically prevents ONP; routine immunization may indirectly prevent selected neuroinvasive infections.

14. Other species and natural disease

Oculomotor neuropathy occurs naturally in domestic animals, including dogs, cats and horses, usually from trauma, inflammation, neoplasia, vascular disease or multifocal neurologic disease rather than a common breed-specific Mendelian syndrome. A 2024 report described bilateral idiopathic oculomotor neuropathy in a cat, but sufficient full text was unavailable for detailed annotation. Evidence is therefore limited to case-level veterinary observations. There is no zoonotic transmission of “oculomotor palsy”; only an underlying infectious cause could itself be transmissible.

Relevant taxa are Homo sapiens (NCBI Taxon 9606), Mus musculus (10090), Rattus norvegicus (10116), Danio rerio (7955), Drosophila melanogaster (7227), Felis catus (9685), Canis lupus familiaris (9615) and Equus caballus (9796).

15. Model organisms

Kif21a knock-in mouse: reproduces CFEOM1-like oculomotor axon stalling and hypoplastic extraocular targets; strong developmental-mechanism model, but not acquired palsy. (fritzsch2023evolutionanddevelopment pages 16-18)
Phox2a-null mouse: lacks normal oculomotor/trochlear nuclei and nerves, modeling recessive CFEOM2; severe developmental phenotype limits therapeutic extrapolation. (fritzsch2023evolutionanddevelopment pages 16-18)
Tubb3 variant/knockout mouse and neuronal culture: tests variant-specific microtubule dynamics, kinesin interaction and axon guidance. Simple loss of Tubb3 does not fully reproduce dominant human missense disease, demonstrating that substitution-specific altered function—not haploinsufficiency—is central. (puri2023tubb3andkif21a pages 1-2, jurgens2021novelvariantsin pages 1-2)
Tuba1a mutant mouse: models cortical-development/tubulin defects, often with severe or perinatal-lethal brain phenotypes; it incompletely models isolated human CFEOM. (jurgens2021novelvariantsin pages 1-2, jurgens2021novelvariantsin pages 9-10)
Generic peripheral-nerve injury models: mouse sciatic-nerve crush/transection and chronic denervation define SARM1/NMNAT2 axon death and Schwann-cell c-JUN repair programs. Their anatomy and target-distance differ substantially from human CN III, so they provide pathway hypotheses rather than validated ONP therapies. (arthurfarraj2021lessonsfrominjury pages 1-2, wagstaff2021failuresofnerve pages 1-2)

Evidence-supported abstract quotations

Puri et al. (published August 4, 2023) state: “Human pathogenic TUBB3 missense variants result in altered TUBB3 function” and cause errors in cranial axon growth/guidance; KIF21A variants likewise “cause errors in cranial axon growth and guidance.” https://doi.org/10.3389/fnins.2023.1226181. (puri2023tubb3andkif21a pages 1-2)
Jurgens et al. (published online March 1, 2021; PMID 33649541) report: “we identified 3 unrelated probands with CFEOM who harbored novel heterozygous TUBA1A missense variants.” https://doi.org/10.1038/s41431-020-00804-7. (jurgens2021novelvariantsin pages 1-2, NCT03059420 chunk 2)
Wagstaff et al. (January 21, 2021) report that genetically restoring Schwann-cell c-Jun “restores regeneration to control levels” in aging/chronic-denervation mouse models. https://doi.org/10.7554/eLife.62232. (wagstaff2021failuresofnerve pages 1-2)
Jessen and Mirsky (February 11, 2019) describe repair Schwann cells as activating functions that “engineer myelin clearance, prevent neuronal death, and help axon growth and guidance.” https://doi.org/10.3389/fncel.2019.00033. (jessen2019thesuccessand pages 1-2)

Knowledge gaps and curation cautions

ONP has no unified molecular signature because it is a final common phenotype of ischemia, compression, inflammation, trauma, infection and developmental dysinnervation. Gene associations must therefore be attached to the appropriate congenital syndrome, not indiscriminately to all ONP. No validated protective allele, modifier gene, epigenetic signature, fluid biomarker, pharmacogenomic rule, disease-specific omics diagnostic, or approved regenerative therapy exists. Recent clinical literature remains dominated by retrospective referral cohorts; randomized treatment evidence is sparse, and the registered acupuncture studies have no available results. The strongest immediate real-world application remains rapid anatomical diagnosis—especially exclusion of aneurysm—followed by cause-specific treatment and staged ocular rehabilitation.

References

(kim2024etiologicaldistributionof pages 4-7): Hyun‐Jae Kim, Hyo‐Jung Kim, Jeong‐Yoon Choi, Hee Kyung Yang, Jeong‐Min Hwang, and Ji‐Soo Kim. Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review. European Journal of Neurology, Feb 2024. URL: https://doi.org/10.1111/ene.16261, doi:10.1111/ene.16261. This article has 18 citations and is from a domain leading peer-reviewed journal.
(kim2024etiologicaldistributionof pages 3-4): Hyun‐Jae Kim, Hyo‐Jung Kim, Jeong‐Yoon Choi, Hee Kyung Yang, Jeong‐Min Hwang, and Ji‐Soo Kim. Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review. European Journal of Neurology, Feb 2024. URL: https://doi.org/10.1111/ene.16261, doi:10.1111/ene.16261. This article has 18 citations and is from a domain leading peer-reviewed journal.
(kim2024etiologicaldistributionof pages 2-3): Hyun‐Jae Kim, Hyo‐Jung Kim, Jeong‐Yoon Choi, Hee Kyung Yang, Jeong‐Min Hwang, and Ji‐Soo Kim. Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review. European Journal of Neurology, Feb 2024. URL: https://doi.org/10.1111/ene.16261, doi:10.1111/ene.16261. This article has 18 citations and is from a domain leading peer-reviewed journal.
(fritzsch2023evolutionanddevelopment pages 16-18): Bernd Fritzsch. Evolution and development of extra-ocular nerves and muscles in vertebrates. Unknown journal, Jun 2023. URL: https://doi.org/10.20944/preprints202306.0416.v1, doi:10.20944/preprints202306.0416.v1.
(puri2023tubb3andkif21a pages 1-2): Dharmendra Puri, Brenda J. Barry, and Elizabeth C. Engle. Tubb3 and kif21a in neurodevelopment and disease. Frontiers in Neuroscience, Aug 2023. URL: https://doi.org/10.3389/fnins.2023.1226181, doi:10.3389/fnins.2023.1226181. This article has 43 citations and is from a peer-reviewed journal.
(jurgens2021novelvariantsin pages 1-2): Julie A. Jurgens, Brenda J. Barry, Gabrielle Lemire, Wai-Man Chan, Mary C. Whitman, Sherin Shaaban, Caroline D. Robson, Sarah MacKinnon, Eleina M. England, Hugh J. McMillan, Christopher Kelly, Brandon M. Pratt, Anne O’Donnell-Luria, Daniel G. MacArthur, Kym M. Boycott, David G. Hunter, and Elizabeth C. Engle. Novel variants in tuba1a cause congenital fibrosis of the extraocular muscles with or without malformations of cortical brain development. European Journal of Human Genetics, 29:816-826, Mar 2021. URL: https://doi.org/10.1038/s41431-020-00804-7, doi:10.1038/s41431-020-00804-7. This article has 32 citations and is from a domain leading peer-reviewed journal.
(kim2024etiologicaldistributionof pages 1-2): Hyun‐Jae Kim, Hyo‐Jung Kim, Jeong‐Yoon Choi, Hee Kyung Yang, Jeong‐Min Hwang, and Ji‐Soo Kim. Etiological distribution of isolated oculomotor nerve palsy: analysis of 633 patients and literature review. European Journal of Neurology, Feb 2024. URL: https://doi.org/10.1111/ene.16261, doi:10.1111/ene.16261. This article has 18 citations and is from a domain leading peer-reviewed journal.
(srimanan2024retrospectiveanalysisof pages 2-4): Worapot Srimanan and Somboon Panyakorn. Retrospective analysis of factors related to the long-term recovery of third, fourth, and sixth cranial nerve palsy with etiologies and clinical course in a tertiary hospital. Clinical Ophthalmology (Auckland, N.Z.), 18:441-450, Feb 2024. URL: https://doi.org/10.2147/opth.s449127, doi:10.2147/opth.s449127. This article has 12 citations.
(srimanan2024retrospectiveanalysisof pages 6-7): Worapot Srimanan and Somboon Panyakorn. Retrospective analysis of factors related to the long-term recovery of third, fourth, and sixth cranial nerve palsy with etiologies and clinical course in a tertiary hospital. Clinical Ophthalmology (Auckland, N.Z.), 18:441-450, Feb 2024. URL: https://doi.org/10.2147/opth.s449127, doi:10.2147/opth.s449127. This article has 12 citations.
(jia2022clinicalandgenetic pages 1-2): Hongyan Jia, Qian Ma, Yi Liang, Dan Wang, Qinglin Chang, Bo Zhao, Zongrui Zhang, Jing Liang, Jing Song, Yidi Wang, Ranran Zhang, Zhanhan Tu, and Yonghong Jiao. Clinical and genetic characteristics of chinese patients with congenital cranial dysinnervation disorders. Orphanet Journal of Rare Diseases, Dec 2022. URL: https://doi.org/10.1186/s13023-022-02582-5, doi:10.1186/s13023-022-02582-5. This article has 12 citations and is from a peer-reviewed journal.
(jia2022clinicalandgenetic pages 7-8): Hongyan Jia, Qian Ma, Yi Liang, Dan Wang, Qinglin Chang, Bo Zhao, Zongrui Zhang, Jing Liang, Jing Song, Yidi Wang, Ranran Zhang, Zhanhan Tu, and Yonghong Jiao. Clinical and genetic characteristics of chinese patients with congenital cranial dysinnervation disorders. Orphanet Journal of Rare Diseases, Dec 2022. URL: https://doi.org/10.1186/s13023-022-02582-5, doi:10.1186/s13023-022-02582-5. This article has 12 citations and is from a peer-reviewed journal.
(jia2022clinicalandgenetic pages 12-13): Hongyan Jia, Qian Ma, Yi Liang, Dan Wang, Qinglin Chang, Bo Zhao, Zongrui Zhang, Jing Liang, Jing Song, Yidi Wang, Ranran Zhang, Zhanhan Tu, and Yonghong Jiao. Clinical and genetic characteristics of chinese patients with congenital cranial dysinnervation disorders. Orphanet Journal of Rare Diseases, Dec 2022. URL: https://doi.org/10.1186/s13023-022-02582-5, doi:10.1186/s13023-022-02582-5. This article has 12 citations and is from a peer-reviewed journal.
(jia2022clinicalandgenetic pages 13-14): Hongyan Jia, Qian Ma, Yi Liang, Dan Wang, Qinglin Chang, Bo Zhao, Zongrui Zhang, Jing Liang, Jing Song, Yidi Wang, Ranran Zhang, Zhanhan Tu, and Yonghong Jiao. Clinical and genetic characteristics of chinese patients with congenital cranial dysinnervation disorders. Orphanet Journal of Rare Diseases, Dec 2022. URL: https://doi.org/10.1186/s13023-022-02582-5, doi:10.1186/s13023-022-02582-5. This article has 12 citations and is from a peer-reviewed journal.
(puri2023tubb3andkif21a pages 2-3): Dharmendra Puri, Brenda J. Barry, and Elizabeth C. Engle. Tubb3 and kif21a in neurodevelopment and disease. Frontiers in Neuroscience, Aug 2023. URL: https://doi.org/10.3389/fnins.2023.1226181, doi:10.3389/fnins.2023.1226181. This article has 43 citations and is from a peer-reviewed journal.
(puri2023tubb3andkif21a pages 3-5): Dharmendra Puri, Brenda J. Barry, and Elizabeth C. Engle. Tubb3 and kif21a in neurodevelopment and disease. Frontiers in Neuroscience, Aug 2023. URL: https://doi.org/10.3389/fnins.2023.1226181, doi:10.3389/fnins.2023.1226181. This article has 43 citations and is from a peer-reviewed journal.
(jurgens2021novelvariantsin pages 9-10): Julie A. Jurgens, Brenda J. Barry, Gabrielle Lemire, Wai-Man Chan, Mary C. Whitman, Sherin Shaaban, Caroline D. Robson, Sarah MacKinnon, Eleina M. England, Hugh J. McMillan, Christopher Kelly, Brandon M. Pratt, Anne O’Donnell-Luria, Daniel G. MacArthur, Kym M. Boycott, David G. Hunter, and Elizabeth C. Engle. Novel variants in tuba1a cause congenital fibrosis of the extraocular muscles with or without malformations of cortical brain development. European Journal of Human Genetics, 29:816-826, Mar 2021. URL: https://doi.org/10.1038/s41431-020-00804-7, doi:10.1038/s41431-020-00804-7. This article has 32 citations and is from a domain leading peer-reviewed journal.
(NCT03099447 chunk 1): Effects of Ocular Electroacupuncture on Oculomotor Nerve Palsy. First Affiliated Hospital of Harbin Medical University. 2017. ClinicalTrials.gov Identifier: NCT03099447
(NCT03099447 chunk 2): Effects of Ocular Electroacupuncture on Oculomotor Nerve Palsy. First Affiliated Hospital of Harbin Medical University. 2017. ClinicalTrials.gov Identifier: NCT03099447
(NCT03461809 chunk 1): A Retrospective Study of the Effects of Ocular Acupuncture on Ocular Motor Nerve Palsy. First Affiliated Hospital of Harbin Medical University. 2018. ClinicalTrials.gov Identifier: NCT03461809
(NCT03059420 chunk 1): Elizabeth Engle. Genetic Studies of Strabismus, Congenital Cranial Dysinnervation Disorders (CCDDs), and Their Associated Anomalies. Boston Children's Hospital. 2004. ClinicalTrials.gov Identifier: NCT03059420
(NCT03059420 chunk 2): Elizabeth Engle. Genetic Studies of Strabismus, Congenital Cranial Dysinnervation Disorders (CCDDs), and Their Associated Anomalies. Boston Children's Hospital. 2004. ClinicalTrials.gov Identifier: NCT03059420
(OpenTargets Search: oculomotor nerve palsy): Open Targets Query (oculomotor nerve palsy, 14 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(wagstaff2021failuresofnerve pages 1-2): Laura J Wagstaff, Jose A Gomez-Sanchez, Shaline V Fazal, Georg W Otto, Alastair M Kilpatrick, Kirolos Michael, Liam YN Wong, Ki H Ma, Mark Turmaine, John Svaren, Tessa Gordon, Peter Arthur-Farraj, Sergio Velasco-Aviles, Hugo Cabedo, Cristina Benito, Rhona Mirsky, and Kristjan R Jessen. Failures of nerve regeneration caused by aging or chronic denervation are rescued by restoring schwann cell c-jun. Jan 2021. URL: https://doi.org/10.7554/elife.62232, doi:10.7554/elife.62232. This article has 142 citations and is from a domain leading peer-reviewed journal.
(ge2025oculomotornervepalsy pages 2-3): Yuanhong Ge, Qingjia Lai, Yunsen Zhang, Yao Wang, and Xuejun Xu. Oculomotor nerve palsy secondary to posterior communicating artery aneurysm: a narrative review and proposed treatment algorithm. Revista de Neurología, Nov 2025. URL: https://doi.org/10.31083/rn40930, doi:10.31083/rn40930. This article has 2 citations.
(arthurfarraj2021lessonsfrominjury pages 1-2): Peter Arthur-Farraj and Michael P. Coleman. Lessons from injury: how nerve injury studies reveal basic biological mechanisms and therapeutic opportunities for peripheral nerve diseases. Neurotherapeutics, 18:2200-2221, Oct 2021. URL: https://doi.org/10.1007/s13311-021-01125-3, doi:10.1007/s13311-021-01125-3. This article has 69 citations and is from a peer-reviewed journal.
(jessen2019thesuccessand pages 1-2): Kristjan R. Jessen and Rhona Mirsky. The success and failure of the schwann cell response to nerve injury. Frontiers in Cellular Neuroscience, Feb 2019. URL: https://doi.org/10.3389/fncel.2019.00033, doi:10.3389/fncel.2019.00033. This article has 577 citations.

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Definitions

Subtypes

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Medical Actions

Environmental Factors

Diagnosis

Progression

Prevalence

Epidemiology

Differential Diagnoses

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Oculomotor Nerve Palsy: Disease-Characteristics Research Report

Executive summary

1. Disease information

Definition and identifiers

Clinical concept

2. Etiology, risk factors, and protective factors

Acquired causes

Risk factors

Protective factors and gene–environment interaction

3. Phenotypes

4. Genetic and molecular information

Causal genes in congenital disease

Human sequencing evidence

5. Environmental, lifestyle and infectious information

6. Mechanism and pathophysiology

Acquired causal chains

Cellular/molecular annotations

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population epidemiology

10. Diagnostics

Immediate clinical assessment

Laboratory and ancillary tests

Genetic testing

Differential diagnosis

11. Outcome and prognosis

12. Treatment and current applications

Cause-directed treatment

Symptomatic and rehabilitative treatment

Trials

13. Prevention

14. Other species and natural disease

15. Model organisms

Evidence-supported abstract quotations

Knowledge gaps and curation cautions

Artifacts

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