third nerve palsy

This a paralysis or “stroke” to the third cranial nerve. This nerve is involved with most muscles controlling eye movement. When the nerve is damaged, this causes the eye to turn down and outwards.  The third nerve is also involved with controlling pupil size, so a palsy will often make the pupil dilate. Finally, the third nerve helps with eyelid elevation and so a palsy will often cause the eyelid to droop (ptosis).  A new third nerve palsy is a potential emergency, especially if the pupil is involved, and usually prompts a trip to the hospital to look for aneurysms or mass lesions that might be pushing on the nerve.

Third Nerve Compression
Compression of the third cranial nerve can make the pupil dilate.
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Dr. Timothy Root is a practicing ophthalmologist and cataract surgeon in Daytona Beach, Florida. His books, video lectures, and training resources can be found at:

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