Benign tumour, originating in the connective tissue around a nerve, usually the auditory nerve. The first symptoms are deafness in one ear, often with an associated whistling sound. As the auditory nerve runs with the nerve from the organ of balance, it is possible that problems of balance may also occur (vertigo). Later, pressure on the nearby trigeminal nerve can cause loss of feeling in and paralysis of the face. Finally the tumour can exert pressure on the brain stem, causing paralysis in the rest of the body. If the tumour has advanced to this extent the diagnosis is practically certain. It is usually possible to remove the entire tumour by surgery, but loss of hearing in one ear can probably not be avoided because the tumour has usually grown rigidly together with the auditory nerve. Loss of feeling in or paralysis of one half of the face is usually completely cured by removal of the tumour.