A noncancerous tumor of the eighth cranial (vestibulocochlear) NERVE. Acoustic neuromas typically grow over years to decades and in some people cause no symptoms; doctors detect them incidentally. An acoustic neuroma does not invade the surrounding tissues, though it can become life-threatening if it becomes large enough to put pressure on the structures of the brainstem.

Most often doctors do not know why acoustic neuromas develop and classify them as idiopathic (of unknown cause). Acoustic neuromas sometimes occur with neurofibromatosis type 2, a rare hereditary disorder in which fibrous growths develop in the CRANIAL NERVES and SPINAL NERVES.

Early symptoms of acoustic neuroma are vague and often perceived as normal consequences of aging because the tumor is so slow growing it typically appears in the later decades of life. Early symptoms include:

• gradual loss of hearing, especially difficulty understanding speech, in one EAR.
• TINNITUS (rushing or roaring sound) in one ear.
• balance disturbances such as dizziness or loss of balance with motion.

Advanced symptoms occur when the tumor’s size begins to encroach on nearby structures such as the seventh cranial (facial) nerve. Such symptoms might include facial PAIN and disturbances of facial expression. An AUDIOLOGIC ASSESSMENT helps determine the level of HEARING LOSS and whether it affects one or both ears.

Hearing loss in both ears suggests causes other than acoustic neuroma; it is very rare that a person would have two tumors, one affecting each vestibulocochlear nerve. MAGNETIC RESONANCE IMAGING (MRI) can usually determine the presence of an acoustic neuroma.

Treatment depends on the extent of symptoms and the person’s overall health status. For many people, especially those who have no symptoms, the preferred treatment is watchful waiting (observation and regular tests to monitor the tumor’s growth).

Surgery to remove the tumor or RADIATION THERAPY to shrink the tumor is an option when symptoms interfere with QUALITY OF LIFE or affect vital brainstem functions such as regulation of BREATHING and HEART RATE or motor control. Each method has risks and benefits; individual health circumstances also influence the decision.

When it exists with no symptoms, acoustic neuroma does not interfere with the regular activities of living or present any threat to health. For most people who experience symptoms and undergo treatment, recovery is complete.

Idiopathic acoustic neuromas do not return, though acoustic neuromas associated with neurofibromatosis type 2 often recur. Other than neurofibromatosis type 2, there are no known risk factors or preventive measures for acoustic neuroma.