Oculomotor Palsy (cranial nerve III palsy)


a.k.a. III nerve palsy


This is a clinical diagnosis. The underlying cause requires investigations.

Clinical features:

In neutral gaze: The eye is looking down & out. There is complete ptosis.
On looking downwards torsional (in-torsion) nystagmus of the eye occurs (due to intact IV nerve action)
Note the presence of meiosis:

  • Normal pupil (pupil sparing): the parasympathetics are spared. Occurs in non-compressive causes.
  • Dilated pupil (pupil involving) the parasympathetics are affected. Occurs in compressive cause. Often painful

Investigations to consider:

Fasting blood glucose, HbA1c, ESR, CRP, ANA, anti-dsDNA, c-ANCA, p-ANCA, LDH, VZV serology

  • Meningioma
  • Midbrain lesions

MRA head or CTA head:

  • PCOM aneurysm, ICA aneurysm, basilar aneurysm

If no abnormalities on MRI there is a dilated pupil, consider:

  • Catheter angiography of cerebral arteries

Consider other tests:

  • CSF: meningitis
  • Tests for head and neck cancer: transneural spread

Causes of Oculomotor nerve palsy (CN III): think of anatomy

Nuclear & fasciular:

  • Tumours: Glioma
  • Part of a brainstem stroke syndrome

Basilar area:

  • Meningitis:
    • Bacterial, Meningovascular syphilis
    • TB meningitis
    • Fungal meningitis
  • Basilar aneurysms
  • Posterior communicating artery PCOM aneurysm
  • Temporal lobe herniation (uncal herniation)

Cavernous sinus area:

  • Tumours: Intrasellar & extrasellar tumours e.g. pituitary, chordoma, meningioma, Nasopharymgeal tumours, craniopharygioma
  • Internal Carotid artery aneurysms
  • Cavernous sinus thrombosis
  • Mucormycosis

Superior orbital fissure & Orbital apex area:

  • Tumours: nasopharygeal, meningioma, hemangioma, glioma, sarcoma, Hand-Schuller-Christian disease, metastasis
  • AVMs
  • Tolosa-Hunt syndrome
  • Pseudotumour of the orbit


  • Idiopathic
  • Vascular:
    • Vasculopathy: diabetes mellitus, hypertension & atherosclerosis, giant cell arteritis
  • Wegner’s granulomatosus
  • Hodgkin’s disease, VZV, encephalitis, collagen vascular disease, Paget’s disease
  • Trauma


Treat the cause

  • Fitting prisms to the patients glasses
  • Patching the affected eye

If unresolving diplopia & palsy consider surgery:

  • Restoring binocular vision in primary positions of gaze


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