Oculomotor nerve palsy

Oculomotor nerve palsies, or third nerve palsypalsies results, result in weakness of the muscles supplied by the oculomotor nerve, namely the superior rectus, inferior rectus, medial rectus, inferior oblique, and levator palpebrae superioris muscles. This leads clinically to an eye that is

Clinical presentation

Classically, patients present with a "down and out" ipsilateral eye, that is, that the eye is resting in abduction, with slight depression and intorsion, and paralysis of adduction, elevation, and depression. This classic resting position is often accompanied by complete ptosis (due to innervation of the levator palpebrae superioris) and diplopia. Patients may also have a large unreactive pupil, which suggests compression of the oculomotor nerve because the parasympathetic pupillary fibres are located peripherally in the nerve and are at higher riskof being affected from external compression.

Pathology

It has numerous possible aetiologies which can be divided according to which portion of the nerve is affected:

• dorsal midbrain (nuclear lesions): usually due to small regions of infarction; often no other neurological symptoms
• ventral midbrain (fascicular): Benedikt syndrome and Weber syndrome
• interpeduncular (subarachnoid)
  • posterior communicating artery aneurysm
    • rapidly enlarging with or without SAH is the most common cause, and usually involves only the oculomotor nerve
    • ischaemic involvement of the nerve will usually be pupil sparing whereas aneurysmal compression usually involves the pupil
  • basal meningeal processes including infection, neoplastic infiltration, and inflammatory lesions (e.g. sarcoidosis) often involve other cranial nerves also
• cavernous sinus portion
  • neoplasms, most commonly pituitary macroadenomas extending into the sinus, meningiomas of the sella or sinus and any other sinus mass (e.g. trigeminal schwannomas) can compress the nerve against the interclinoid ligaments
  • when the process is more diffuse, such as in cavernous sinus syndrome then other cranial nerves are also involved (e.g. Tolosa-Hunt syndrome)
• orbital portion
  • usually there is asociated proptosis or other focal orbital signs
  • conditions include intraorbital tumours (optic nerve glioma, optic nerve meningioma) and inflammatory orbital pseudotumor

Related articlesSee also

• trochlear nerve palsy
• abducens nerve palsy