Symptoms and Anatomy of Acoustic Neuromas

     Hearing disturbances from acoustic neuromas are probably due to pressure on the cochlear portion of the vestibulocochlear (8th) cranial nerve. Allegedly, the cochlear nerve is more sensitive to pressure than other nerves.

     The internal auditory artery supplies blood to the cochlear nerve. Pressure on this artery may also be the cause of hearing changes associated with acoustic neuromas.

     The internal auditory artery is often removed at surgery along with the nerve, in order to get the tumor out, thus surgery can result in complete hearing loss.

     Most acoustic neuromas actually arise from the vestibular nerve portion of the vestibulocochlear nerve; however the vestibular nerve, which deals with balance, seems to adapt far more readily than the cochlear (hearing) portion of the nerve to pressure from a growing tumor.

     The facial nerve is resistant to pressure so most patients do not present with facial nerve weakness as an early sign of their acoustic neuroma; however, some patients will note facial spasms or twitches, or difficulty with blinking the eye on the side of the tumor.

     The facial nerve is responsible for tears and nasal secretions so either of these can be damaged during surgery.

     Numbness of the face, mouth, or tongue, is only supposed to occur if the tumor is large enough to pressure the trigeminal (fifth) nerve. However, anecdotally, some patients seem to have such symptoms even with smaller tumors.

     Pressure on the trigeminal nerve can also cause sudden stabs of severe pain.

     Pressure on the abducens (6th) cranial nerve will cause problems moving the eye laterally.

     Pressure on the 10th cranial nerve will cause difficulty swallowing.

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© November 24, 2004, Bradley Hennenfent, MD
http://www.acousticneuromafoundation.org/