CRANIAL NERVE PALSIES & DOUBLE VISION
There are twelve paired cranial nerves. The 3rd cranial nerve (oculomotor nerve), 4th cranial nerve (trochlear nerve) and 6th cranial nerve (abducens nerve) supply messages to the eye muscles that move the eyeballs. If the 3rd, 4th, or 6th cranial nerves are “sick” or injured, the eyes do not move in synchrony and double vision* may result.
The cranial nerves can be injured from trauma (e.g. car accident or falls), lack of blood supply (e.g. diabetes, high blood pressure, giant cell arteritis), inflammations (e.g. viruses, meningitis, multiple sclerosis) or from structural lesions (e.g. tumors or aneurysms).
Patients with 6th cranial nerve (abducens) palsies usually complain of double vision worse in the distance, with horizontal separation of the objects. The affected eye may appear displaced in towards the nose.
Patients with 3rd cranial nerve (oculomotor) palsy may have a droopy eyelid, and inability to move the eye inwards, and vertically. The affected eye may be displaced downwards and outwards. If the eyelid is not markedly drooped, then double vision with diagonal separation is often seen. If a patient has a new onset third nerve palsy accompanied by a dilated pupil, the possibility of a brain aneurysm should be excluded.
Patients with 4th cranial nerve (trochlear) nerve palsies often complain of double vision with diagnoal separation. By tilting the head opposite the side of the fourth nerve palsy, patients can often decrease their double vision.
Cranial nerve palsies due to lack of blood supply frequently recover by themselves over a 1 to 6 month period. In the interim patients can patch their eyes/tape their glasses, or try prism glasses that bend light in a direction opposite to the abnormal eye deviation. Hilary Clinton has a temporary “stick-on” Fresnel prism over her left lens.
If the cranial nerve palsy shows no sign of recovery after 9-12 months, then strabismus surgery might be considered.
MYASTHENIA GRAVIS (antibody blockade of the chemical messenger between the nerves to the muscles) can sometimes cause the appearance of a cranial nerve palsy. Acetylcholine receptor antibody blood test may help exclude this possibility.
*If you have double vision that persists, even when you cover one eye, the comments on this page probably do NOT apply to you.