Symptoms of cranial nerve disorders depend on which nerves are damaged and how they were damaged. Cranial nerve disorders can affect smell, taste, vision, sensation in the face, facial expression, hearing, balance, speech, swallowing, and muscles of the neck. For example, vision may be affected in various ways:
If one of the 2nd cranial nerves (optic nerve) is damaged, vision in the affected eye may be partially or completely lost.
If any of the three cranial nerves that control eye movement (3rd, 4th, or 6th cranial nerve) is damaged, people cannot move their eyes normally. Symptoms include double vision when looking in certain directions.
If the 3rd cranial nerve (oculomotor nerve) is paralyzed, people cannot move their upper eyelid. It droops down over the eye and interferes with vision.
If the 8th cranial nerve (auditory or vestibulocochlear nerve) is damaged or malfunctions, people may have problems hearing and/or vertigo—a feeling that they, their environment, or both are spinning.
Cranial nerve disorders can also cause various kinds of facial or head pain.