An acoustic neuroma is a benign tumor of the nerve leading from the ear to the brain. Though the tumor is not cancerous, and will not spread to other structures, it can cause serious symptoms, and can grow large enough to impinge on important structures in the brain. Acoustic neuromas are usually located near the base of the brain, and are one of the most common brain tumors, though they are rare in general.
The cause of acoustic neuroma is unknown, though the tumor is often linked to the genetic disorder neurofibromatosis type 2. It is believed that all cases of acoustic neuroma have a genetic basis. The tumor is very slow-growing, and consequently symptoms do not usually appear before the patient's 30s.
Acoustic neuroma symptoms vary, but they commonly include hearing loss; tinnitus, a ringing sensation in the ear; and vertigo, the sensation of movement when the body is still. Other symptoms may include dizziness and loss of balance beyond vertigo, numbness or pain in the face or in one ear, weakness of the facial muscles, problems understanding speech, temporary problems with vision, fatigue, and headache. Headache as a symptom of acoustic neuroma often occurs early in the morning, and may wake the patient up. It may also be accompanied by nausea or vomiting and is often worse when the patient is in certain positions, such as sitting up or lying down. Sneezing, coughing, or otherwise straining may also worsen the headache.
Acoustic neuroma is diagnosed by physical tests including tests for hearing, vertigo, and balance. The most useful test is often a magnetic resonance imaging (MRI) or computed tomography (CT) scan of the head. If the tumor is small and not accompanied by serious symptoms, the patient may simply be kept under observation. As the tumor is slow-growing, it may never present a problem during the patient's lifetime.
If an acoustic neuroma grows large enough to negatively affect the patient's quality of life, or to endanger structures in the skull, surgery is typically used to remove the tumor. In some cases, brain surgery may be required to save the patient's life if the tumor is pressing on important brain structures. Acoustic neuromas can be treated by traditional surgery or radiosurgery. Radiosurgery can only be used on relatively small tumors, and is aimed at terminating growth of the tumor rather than removing it. The patient may suffer permanent hearing or nerve damage after either type of surgery, so they are only used as a last resort.