COMANAGEMENT

Pupil Plays Dominant Role in Third Nerve Palsy

Edited by Paul C. Ajamian, O.D.

Q. How do you manage a patient who presents with sudden eye pain, ptosis, diplopia and a dilated pupil?
A. A patient who presents with the above symptoms is probably suffering an acquired third nerve, or oculomotor, palsy.
The challenge here is to determine what’s causing the palsy: Is it a compressive lesion, such as an aneurysm? Or is it a more benign blunt trauma, or a vasculopathic problem caused by diabetes or hypertension? If it’s an aneu-rysm—signaled primarily by pupil involvement—be aware that this is a life-threatening situation: The patient needs emergency neurological imaging and hospitalization.

Because intraocular and extraocular muscles can simultaneously be involved in third nerve palsy, the clinical symptoms described above are often obvious, says Tamarac, Fla. optometrist Gus Garmizo. You should confirm your suspicions through motility (ductions and versions) and pupil testing. The most common causes of third nerve palsy in adults are aneurysms, vascular disease and trauma.

“A complete palsy will cause the eye to be slightly depressed and abducted, what we refer to as being ‘down and out,’” Dr. Garmizo says.
“The eye will not adduct past the midline due to loss of medial rectus innervation, you’ll have loss of superduction due to decreased superior rectus innervation, and the eye will be intorted due to loss of inferior oblique innervation.”

Pupil involvement, loss of accommodation and the presence of a headache all heighten the suspicion of an aneurysm, he explains.
Conversely, most pupil-sparing cases are vasculopathic in origin. Be aware, however, that a small percentage of aneurysm-present, third nerve palsy cases are, in fact, pupil-sparing at onset.

The bottom line: When doing the workup, remember that while pupil involvement strongly indicates the presence of an aneurysm, pupil sparing does not necessarily mean there isn’t one.

In rare cases the reverse will happen: The pupil will be involved, but there will be no motility deficits at onset. Almost always, however, the extraocular symptoms will manifest within a few weeks. Additionally, patients might not always experience diplopia if ptosis is occluding the affected eye.

So how do you proceed? As a rule of thumb, Dr. Garmizo advises that if the pupil is involved, if there is eye pain or a headache, and if the patient has no history of trauma or vascular disease, automatically assume that he or she has a cerebral aneurysm until proven otherwise, and proceed immediately with neurological intervention.

Q. What neurological tests are needed to confirm the presence of an aneurysm?
A. As mentioned, this situation requires that the patient get emergency diagnostic imaging and hospitalization. Both invasive and less-invasive techniques are used today. MR angiography is effective in detecting larger aneurysms, but can miss small ones, says Atlanta neurologist Mark Kozinn, M.D. More invasive testing presents some risk of stroke to the patient, but “it’s the ‘gold standard’ in detecting aneurysms and the way to go if you’re concerned,” he says.

If there is no pupil involvement, the situation is less urgent. Arrange for lab work and follow the patient closely until the palsy resolves to see if the pupil dilates. (It is believed that in all aneurysm-present cases, the pupil will eventually dilate.)

Also arrange for non-invasive neurological imaging to be done on an outpatient basis to confirm or rule out the presence of an aneurysm. In younger patients—especially children—where the cause is less likely to be vasculopathic, neurological testing should always be performed.
Subsequent management of symptoms depends largely on the degree of recovery, which can take several weeks to months. Patients with residual diplopia may benefit from prisms or surgical correction.

Remember to test accommodation in young and pre-presbyopic patients for residual internal ophthalmoplegia. For example, in the photo on Page 109, the patient’s extraocular muscles recovered from a blunt trauma-induced palsy, yet the parasympathetic fibers to the pupil didn’t, resulting in a dilated pupil and no accommodation ability. His near vision was then corrected with bifocals.

A consequence of trauma-induced third nerve palsy is aberrant regeneration, also seen in this photo, where regenerating nerve fibers no longer follow their previous paths, but innervate different muscles supplied by the third nerve. Clinical signs include lid elevation during adduction or depression. Treatment isn’t usually necessary since it doesn’t interfere with vision, but the condition does confirm there has been a third nerve palsy.

Congenital third nerve palsy presents mostly in children and is usually a manifestation of widespread neurological and developmental damage. Intervention is necessary to prevent strabismic amblyopia.

Management includes patching, bifocal adds (with internal ophthalmoplegia), prisms and possibly surgery for ocular alignment in primary gaze. “Preventing amblyopia is extremely difficult,” Dr. Garmizo cautions, “and management should be attempted only by specialists experienced in handling the sensory aspects of childhood strabismus.”
Other causes of third nerve palsy include tumors, sarcoidosis, cysts, metastatic disease, meningitis, encephalitis, lupus, temporal arteritis, migraine, demyelination, syphilis, herpes zoster, or cavernous sinus fistula.

“These will all be ruled out with the MRI and blood work,” he says. “The key is that once you’ve ruled out the aneurysm, you’ll have time to investigate the other possibilities.”

Send your comanagement questions to Review of Optometry, 201 King of Prussia Road, Radnor, PA 19089; fax them to 610-964-2959; or e-mail them to reviewofoptometry@jobson.com

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