Third nerve palsy

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Background

  • Third (oculomotor) nerve, innervates eyelid muscles and external ocular muscles (except lateral rectus and superior oblique)
  • Nerve also carries parasympathetic fibers on external surface allowing for pupillary constriction
  • Palsy causes diplopia except in lateral gaze (lateral rectus innervated by CN VI)
  • Ptosis, headache

Causes

  • PCom artery aneurysm
    • Compresses nerve
  • Ischemia
    • Diabetes
  • Trauma
    • Temporal lobe herniation through tentorium
  • Myasthenia Gravis

Clinical Features

  • Eye deviates laterally and down
  • Pupil exam:
    • If dilated/nonreactive likely secondary to space occupying lesion
    • If pupil is spared likely ischemic etiology
  • Loss of accommodation

DDx

  • Aneurysm
  • Carotid Cavernous Fistula
  • Mass
  • Ischemia


Work-up

  • CT/CTA head
  • MRI/MRA head
  • Cerebral Angiography

Dispo

  • If ischemic cause
    • Medical management with most self resolving in 6-8 wks
    • Ophthalmology f/u
  • If aneurysm/mass
    • Neurosurgery consult
  • If diplopia, no driving or operating heavy machinery

Source

Harwood and Nuss, Rosen's, Emedicine

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