Strabismus Online Information Resource

Third Nerve Palsy

  • The third cranial nerve innervates the levator muscle, the pupillary sphincter and the extraocular muscles involved in the movement of the eye in all three planes (horizontal, vertical, and torsional). The inferior division of the third nerve innervates the pupil, the inferior rectus, medial rectus, and inferior oblique muscles while its superior division innervates the superior rectus and levator muscles.


  • Congenital vs acquired
  • Complete vs partial
  • Pupil-sparing vs pupil-involved
  • Aberrant regeneration

Congenital Third Nerve Palsy

  • rare
  • usually unilateral
  • associated with other neurologic abnormalities in a significant percentage of patients
  • etiology:
    • lesion of the nerve (most common)
    • aplasia or hypoplasia of the oculomotor nucleus
  • clinical picture: exotropia, hypotropia and ptosis
  • incomitant deviations largest in the field of action of the affected muscles
  • +/-efferent pupillary defect secondary to deficient sphincter innervation or aberrant papillary response related to aberrant innervation.
  • +/-aberrant regeneration (common)
  • +/-cyclic oculomotor spasm
  • significant risk of amblyopia

Acquired Third Nerve Palsy

  • uncommon
  • usually unilateral
  • etiology:
    • trauma (more common in children)
    • neoplasm (primary or metastatic tumor)
    • aneurysm (more common in younger adults)
    • vascular (more common in older adults):
      • hemorrhage
      • infarction (diabetes mellitus & hypertension)
    • demyelinating (more common in young adults)
  • exotropia, hypotropia and ptosis of varying degrees depending on the anatomic location of the lesion.
  • incomitant deviations largest in the field of action of the affected muscles
  • diplopia &/or visual confusion
  • compensatory head posture
  • +/-pupillary involvement depending on the etiology: (microvascular, diabetic > pupil-sparing), (compressive > pupil-involving).

Pupil-involving Isolated Third Nerve Palsy

  • complete ptosis
  • dilated pupil unresponsive to light or accomodation
  • exotropia +/-hypotropia
  • appropriate investigation must be pursued until an aneurysm (particularly a posterior communicating artery aneurysm) is excluded
    if an aneurysm is found, emergency neurosurgery must be performed to prevent subarachnoid hemorrhage

Pupil-Sparing Isolated Third Nerve Palsy

  • The pupillary fibers travel in the outer layers of the third nerve and are therefore closer to the nutrient blood supply surrounding the nerve. This may explain why the pupils are spared in 80% of ischemic third nerve palsies, but are affected in 95% of cases of compressive (trauma, tumor, aneurysm) third nerve palsies.
  • If the pupil is spared and the patient is over 50 years of age, diabetic, or hypertensive, a diagnosis of vasculopathic 3rd nerve palsy may be presumed.
  • The patient is followed carefully for the first week since aneurysms that do not at first involve the pupil have been described.

Aberrant regeneration

  • Regenerating third nerve fibers may be misdirected from the muscle location they normally innervate, to other muscles they don't normally innervate.
  • Primary aberrant regeneration occurs when there is insidious development of third nerve palsy with accompanying signs of misdirection. There is no preceding acute third nerve palsy. It is usually caused by an intracavernous lesion such as meningioma, aneurysm or neurinoma.
  • Secondary aberrant regeneration is usually observed weeks to months after the onset of the palsy. It is seen after trauma and after compression of the third nerve by tumor, but never after third nerve palsy of ischemic origin.
  • Lid-gaze dyskinesis: pseudo-von Graefe's sign: eyelid retraction with depression of the eye inverse Duane's syndrome: eyelid retraction with adduction of the eye
  • Pupil-gaze dyskinesis: pseudo-Argyll Robertson pupil: greater constriction of pupil to convergence than to light. pupillary constriction on attempted downgaze


  • complete ocular and neurological examination
  • Immediate CT scan of the brain (axial and coronal) &/or MRI is indicated for:
  • Pupil-involving (relative or complete) third nerve palsies
  • Pupil-sparing third nerve palsies in the following groups of patients:
    • younger than 50 years of age
    • incomplete third nerve palsies
    • third-nerve palsies of greater than 3 months in duration with no improvement
    • additional cranial nerve or neurologic abnormality
  • Development of aberrant regeneration (except for traumatic third nerve palsies)
  • Cerebral angiography in patients older than 10 years of age, with pupil-involved and CT scan &/or MRI is normal or shows a mass consistent with an aneurysm.
  • Tensilon Chloride test when pupil not involved and myasthenia gravis suspected
  • ESR if giant cell arteritis suspected


  • Pupil-involved
  • Immediate hospitalization and work-up as described above
  • Pupil-spared
  • Follow-up for 1 week to observe for delayed pupil involvement then recheck every 6 weeks. Resolution should occur within 3 months.
  • The management of third nerve palsy is difficult because of multiple muscle involvement and both horizontal and vertical ocular misalignment.
  • Observation for at least 6 months should be the initial management to allow for spontaneous improvement.
  • The therapeutic goals are to eliminate diplopia in primary position and to create binocularity in as many gaze positions as possible.
  • Non-surgical treatments:
    • patching in visually immature children to prevent amblyopia
    • occlusion or prisms to relieve diplopia in visually mature individual (especially during the observation period)
    • botulinum toxin injection of the antagonist muscle(s) to prevent contracture
  • Surgical treatments:
    • supramaximal recession of the lateral rectus muscle, and supramaximal resection of the medial rectus muscle to improve the exotropia.
    • if no medial rectus muscle function exists, a transposition of the superior oblique tendon insertion to a position adjacent to the medial rectus insertion might be attempted
    • Ptosis surgery is done after completion of the strabismus surgery.


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