Oculomotor nerve palsies


Oculomotor nerve palsies

Description, Causes and Risk Factors:

Alternative Name: Third nerve palsy.

The third cranial nerve controls movement of four eye muscles that move the eye in, up, down and torsion. The third cranial nerve also controls constriction of the pupil, the eyelid and the ability of the eye to “focus” or accommodate and upper eyelid position.

The oculomotor nerve (cranial nerve III) innervates all internal and external ocular muscles except the superior oblique and the lateral rectus and is considered the most important nerve involved in ocular motility. Although oculomotor nerve palsy is less common than sixth and fourth cranial nerve palsies, it is associated with significant morbidity.

Patients typically present with blepharoptosis, limitation in eye movement accompanied by exotropia and a dilated pupil which poorly reacts to light.

Types May include:

    Congenital oculomotor nerve palsy is rare compared to acquired oculomotor nerve palsy.

  • Ischemia is the most common cause of pupil sparing oculomotor nerve palsy.

  • Intracranial aneurysms are the most common cause of isolated oculomotor nerve palsy involving the pupil.

Most reports have stated ischemia as the most common cause of oculomotor nerve paralysis. Although the majority of patients with ischemic oculomotor nerve palsy suffer from diabetes mellitus, other disorders such as hypertension, atherosclerosis and migraine may manifest similarly.

The majority of peripheral oculomotor nerve palsies are caused by minor injury to vessels in subarachnoid space or in the cavernous sinus. Less common causes are compression (due to aneurysm or tumor) and inflammation (sarcoidosis and vasculitis). In cases of trauma-related third cranial nerve palsy, underlying lesions such as aneurysms and tumors should be considered and ruled out.

Childhood Causes of third nerve (oculomotor) palsy may include:

    Trauma.

  • Neoplasm.

  • Undetermined.

  • Ophthalmoplegic migraine.

  • Postoperative cause.

  • Meningitis/encephalitis.

  • Subdural hematoma.

  • Viral or post-upper respiratory tract infection.

  • Varicella-zoster virus.

  • Aneurysm.

  • Orbital cellulitis.

  • Sinus disease.

  • Mesencephalic cyst.

  • Cyclic oculomotor nerve palsy.

Symptoms:

Symptoms May Include:

    Diplopia.People over 10 years of age with third nerve palsy usually have diplopia (double vision) due to misalignment of the eyes. If a ptosis (droopy eyelid) covers the pupil, diplopia may not be noticeable.

  • Children may develop amblyopia in the involved eye.

  • Ptosis.

  • Symptomatic glare from failure of constriction of pupil.

  • Blurring of vision on attempt to focus of near objects due to loss of accommodation.

Diagnosis:

The diagnosis is based on results of a neurologic examination and computed tomography (CT) or magnetic resonance imaging (MRI). If the pupil is affected or if symptoms suggest a serious underlying disorder, CT is done immediately. If a ruptured aneurysm is suspected and CT does not detect blood, a spinal tap (lumbar puncture), magnetic resonance angiography, CT angiography, or cerebral angiography is done.

Treatment:

    Treatment if often surgical. The surgical treatment of third nerve palsies presents a formidable challenge to the ophthalmic surgeon. A complete third nerve paralysis with complete ptosis is best left untreated.

  • When the paralysis is partial, especially when some adduction is preserved, the patient may benefit from maximal recession of the lateral and resection of the medial rectus muscles. This may be combined with upward transposition of the muscle insertions to counteract the hypotropia. Transfer of the superior oblique muscle to the insertion of the medial rectus muscles with or without fracture of the trochlea has also been recommended.

  • Ptosis surgery is postponed until alignment of the eyes has been achieved by surgery. Caution with regard to ptosis surgery is advised if elevation is impaired because of exposure problems.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

Reference and Source are from:

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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