An acoustic neuroma (also called vestibular schwannoma) is a benign (non-cancerous) tissue growth that arises on the eighth cranial nerve. Early symptoms are easily overlooked. In over 90% of people there is a reduction in hearing in one ear, often accompanied by ear noise or ringing (tinnitus). The loss of hearing is usually subtle and worsens very slowly, although occasionally a sudden loss of hearing occurs. Unsteadiness and balance problems may occur early in the growth of the neuroma since the balance portion of the eighth cranial nerve is where the tumour arises. The remainder of the balance system sometimes compensates for this loss, and balance problems may be forgotten. As the tumour presses on other cranial nerves, facial sensation may be affected, with numbness and facial tingling felt constantly or intermittently. Headaches and unsteady gait caused by increased intracranial pressure may occur.
Asymptomatic acoustic neuromas have been found during autopsy in 2.4% of the general population. Estimates of symptomatic acoustic neuromas range from one in every 3,500 people to five in every million people. More women than men are affected. Most acoustic neuromas are diagnosed between the ages of thirty and sixty.