An acoustic neuroma is a benign (noncancerous) tumor that starts from a nerve of the brain, the eighth cranial nerve, also known as the vestibular nerve. Cranial nerves are 12 pairs of nerves that come from the bottom surface of the brain. Cells wrapping around this nerve are called Schwann cells. Acoustic neuromas are also called vestibular schwannomas.
Neuromas can affect either one ear (unilateral) or both ears (bilateral). Most occur in people 30 to 60 years old.
The cause is unclear, but the tumor results from production of too many Schwann cells around the vestibular nerve. Unilateral neuromas occur sporadically and are not inherited. Bilateral neuromas are associated with the genetic disorder neurofibromatosis. Acoustic neuromas are not contagious and cannot spread from one person to another. No way to prevent acoustic neuromas is known.
The first symptom in more than 90% of people is one-sided hearing loss. The usually subtle hearing loss occurs slowly. However, sudden acute hearing loss can occur.
Other symptoms include loss of balance and tinnitus (a ringing or hissing sound in the ear).
A growing tumor may press on nerves and cause numbness and tingling in the face or facial muscle paralysis and loss of facial expression. A large tumor can squeeze part of the brain and lead to headaches, clumsy walking, and confusion.
If symptoms appear, the health care provider will do complete neurological and ear examinations and a hearing test (audiogram). Early diagnosis is critical.
The health care provider will order an MRI or CT scan of the brain to help diagnose the acoustic neuroma.
Treatments include surgery, radiation, and monitoring. Treatment is decided on the basis of tumor size and growth rate, degree of impairment, life expectancy, age, and surgical risk.
Surgery is the most reliable treatment. For very small tumors, hearing may be saved and symptoms may improve. Surgery for larger tumors is more complicated.
Another excellent choice, instead of traditional surgery, may be gamma knife surgery. This method uses beams of highenergy gamma radiation aimed exactly at the tumor and leaves other areas alone.
Radiation therapy may reduce the size or limit the growth of a neuroma. This therapy is sometimes preferred for elderly people, people in poor health, people with tumors affecting both ears, or people with a tumor affecting their only hearing ear.
Just watching the tumor and repeating the brain MRI after a few months may be reasonable in some cases, usually in people with other serious illnesses.
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