Acquired third nerve lesions: most common causes

Location of the lesion	Associated symptoms/signs	Most common causes
Nucleus	Complete ipsilateral third plus contralateral ptosis and contralateral superior rectus weakness	Infarction Hemorrhage Tumor
Fascicles	Contralateral hemiparesis (Weber's syndrome) Contralateral tremor (Benedikt's syndrome) Ipsilateral ataxia (Nothnagel's syndrome)	Infarction Hemorrhage Tumor Demyelination
Subarachnoid space	Typically isolated May present with headaches or orbital pain	ICA/Pcom A/Basilar/PCA Aneurysm Microvascular (ischemic) Tumor (pituitary, carcinomatous meningitis) Meningitis Herniation Trauma
Cavernous sinus	Cranial nerves IV, VI, V1, V2 Oculosympathetic dysfunction (Horner) Pain may be prominent	Tumor Inflammation Carotid aneurysm Microvascular (ischemic) Thrombosis Arteriovenous fistula
Orbital apex	Proptosis Visual loss Cranial nerves IV, VI, V1, V2 Oculosympathetic dysfunction (Horner) Pain may be prominent	Trauma Tumor Inflammation Infection (fungus)

Causes_of_third_nerve_palsy.htm

ICA: internal carotid artery; Pcom A: posterior communicating artery; PCA: posterior cerebral artery.

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