What is third nerve palsy and what happens?

Double vision.: A third nerve palsy can develop when the nerve is irritate by compression or inflammation. This nerve helps to control the response of your pupil to light as well as movement of your eyeball and eyelid. When the nerve is not working properly, patients can experience double vision. Sometimes, the pupil is larger than the normal side and the eyelid can droop.

Cranial nerve insult: The eye muscles are innervated by three major nerves: cranial 3,4 and 6. The third nerve acts on 4 of the six eye muscles and also the pupil and upper lid. Palsy of this nerve occurs from trauma, vascular problems, diabetes and others. In complete palsy the eye cannot move down or towards the nose, the pupil dilates and the lid droops. Sometimes permanent; occasionally can recover.

Double vision: The third cranial nerve, Oculomotor, comes from the midbrain and supplies most of the muscles that move and open the eye. Weakness, called "palsy", of the nerve gives double vision, and can also give a droopy eye and/or a dilated pupil. The most common causes are: diabetes, trauma, brain tumor or a brain aneurysm. An MRI or CT of the brain is usually the best diagnostic test to determine why!