cranial nerve III palsy; oculomotor nerve palsy

Etiology

• ischemic microvascular disease
  • diabetes mellitus
  • hypertension
• posterior communicating artery aneurysm
• cavernous sinus thrombosis (may also involve CN4 & CN6)
• myasthenia gravis
• Grave's disease
• tumor
• trauma

Pathology

• diabetic 3rd nerve palsy
  • pupillary sparing due to vascular damage in the central portion of CN-3
  • parasympathetic pupillomotor fibers at the periphery remain intact
• aneurysm of the posterior communicating artery
  • may also spare parasympathetic pupillomotor fibers at the periphery of CN-3
  • compression of CN-3 as in emerges from the brainstem at the junction of the posterior communicating artery & the internal carotid artery

Clinical manifestations

• diabetic 3rd nerve palsy
  • pain often precedes palsy
  • mild ptosis of affected eye
  • inability to adduct or move affected eye medially
  • pupillary reflexes are often intact
• myasthenia gravis
  • disturbance in CN-IV & CN-VI are also likely
  • internuclear ophthalmoplegia & other sign of myasthenia gravis

Laboratory

• serum chemistries: serum glucose
• erythrocyte sedimentation rate (ESR)

Diagnostic procedures

• tensilon test (myasthenia gravis)

Radiology

• magnetic resonance imaging (MRI)
• cerebral angiography if pupil(s) involved & MRI is negative
• magnetic resonance angiography (MRA)
  • evaluate for posterior communicating artery aneurysm

Differential diagnosis

• myasthenia gravis
• thyroid disease (hyperthyroidism)
• orbital pseudotumor (inflammatory)
• Parinaud's syndrome
• giant cell arteritis
• cavernous sinus thrombosis may also involve cranial nerve 4 & cranial nerve 6
  • Tolosa Hunt syndrome

Management

• total cranial nerve 3 palsy with normal pupil
  • follow patient for 5 days
    • after 5 days, pupil is unlikely to dilate
  • identify risk factors (diabetes, HTN)
  • recovery generally occurs < 3 months
• total cranial nerve 3 palsy with dilated pupil*
  • MRI immediately to rule out compressive lesion
  • if MRI is negative, cerebral angiography
• partial cranial nerve 3 palsy with normal pupil
  • follow without treatment
• partial cranial nerve 3 palsy with dilated pupil*
  • MRI immediately to rule out compressive lesion
  • if MRI is negative, cerebral angiography

* key to management is the presence of a dilated pupil

More general terms

• cranial nerve palsy

More specific terms

• Weber-Gubler syndrome; hemiparesis alternans oculomotoria; superior alternating hemiplegia

Additional terms

• oculomotor nerve (CN III)