Third nerve palsy

Features

• eye is deviated 'down and out'
• ptosis
• pupil may be dilated (sometimes called a 'surgical' third nerve palsy)

Causes

• diabetes mellitus
• vasculitis e.g. temporal arteritis, SLE
• false localizing sign* due to uncal herniation through tentorium if raised ICP
• posterior communicating artery aneurysm
  • pupil dilated
  • often associated pain
• cavernous sinus thrombosis
• Weber's syndrome: ipsilateral third nerve palsy with contralateral hemiplegia -caused by midbrain strokes
• other possible causes: amyloid, multiple sclerosis
• this term is usually associated with sixth nerve palsies but it may be used for a variety of neurological presentations