Vascular disorders such as diabetes, heart disease, atherosclerosis and aneurysm, particularly of the posterior communicating artery.It can also occur as a consequence of severe birth trauma. The condition can also result from aplasia or hypoplasia of one or more of the muscles supplied by the oculomotor nerve. There is some evidence of a familial tendency to the condition, particularly to a partial palsy involving the superior division of the nerve with an autosomal recessive inheritance. The origins of the vast majority of congenital oculomotor palsies are idiopathic. Non traumatic pupil-sparing oculomotor nerve palsies are often referred to as a "medical third", with those affecting the pupil being known as a "surgical third". Oculomotor palsy can arise as a result of a number of different conditions.
The affected individual will also have a ptosis, or drooping of the eyelid, and mydriasis (pupil dilation). The downward displacement occurs because the superior oblique muscle (innervated by the fourth cranial or trochlear nerve) is unantagonized by the paralyzed superior rectus, inferior rectus and inferior oblique. The outward displacement occurs because the lateral rectus muscle (innervated by the sixth cranial nerve) maintains muscle tone in comparison to the paralyzed medial rectus. The limitations of eye movement resulting from the condition are generally so severe that patients are often unable to maintain normal eye alignment when gazing straight ahead, leading to strabismus and, as a consequence, double vision ( diplopia).Ī complete oculomotor nerve palsy will result in a characteristic displacement outward ( exotropia) and downward (hypotropia). The nerve also supplies the upper eyelid muscle ( levator palpebrae superioris) and is accompanied by parasympathetic fibers innervating the muscles responsible for pupil constriction ( sphincter pupillae). Damage to this nerve will result in an inability to move the eye normally. As the name suggests, the oculomotor nerve supplies the majority of the muscles controlling eye movements (four of the six extraocular muscles, excluding only the lateral rectus and superior oblique). Oculomotor nerve palsy or oculomotor neuropathy is an eye condition resulting from damage to the third cranial nerve or a branch thereof.
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