|CRANIAL NERVE III PALSY
SIGNS AND SYMPTOMS
There will be limitation of elevation, depression and adduction. There is an underaction of the superior, inferior, and medial recti muscles and inferior oblique muscle, which may be total or partial. The pupil may be dilated and minimally reactive to light (pupillary involvement), totally reactive and normal (pupillary non-involvement), or may be sluggishly responsive (partial pupillary involvement). The patient is frequently elderly and often has concurrent diabetes and/or hypertension.
Damage to the third nerve within the subarachnoid space produces an isolated third nerve palsy. The main causes are compression of the nerve by an expanding aneurysm of the posterior communicating artery or the basilar artery, and ischemic vasculopathy. There will always be pain in aneurysmal compression and pupillary involvement is typical, though there have been infrequent cases of aneurysmal compression that did not initially affect pupillary function. In ischemic vascular nerve third palsies, pain is frequent and the pupil is typically normal and reactive.
Damage to the third nerve in the cavernous sinus, superior orbital fissure, or posterior orbit is unlikely to present as third nerve palsy due to the confluence of other structures in these areas. Cavernous sinus involvement may also include pareses of cranial nerves IV, VI and V-1, and an ipsilateral Horner's syndrome. The most common causes of damage in these areas include metastatic disease, inflammation, herpes zoster, carotid artery aneurysm, pituitary adenoma and apoplexy, and sphenoid wing meningioma.
If the patient is under 50 and has a non-pupillary involved isolated third nerve palsy, intracranial angiography is indicated since ischemic vasculopathy is less likely to occur in this age group than is aneurysm. If the adult patient of any age presents with a complete or incomplete isolated third nerve palsy with pupillary involvement, consider this to be a medical emergency and have the patient undergo intracranial angiography immediately. In these cases, the cause is likely subarachnoid aneurysm and the patient may die if the aneurysm ruptures. Children under the age of 14 rarely have aneurysms; the majority of third nerve palsies in this age group are traumatic or congenital.
Other reports in this section
Eyelids & Eyelashes | Conjunctiva & Sclera | Cornea
Uvea | Vitreous & Retina | Optic Nerve & Brain | Oculosystemic Disease
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