Acoustic Neuroma

What Is It?

An acoustic neuroma is a type of benign (noncancerous) brain tumor that grows in the middle ear. It is one of the most common types of benign brain tumors, and is a major cause of hearing loss.

The auditory nerve (also called the eighth cranial nerve) connects the inner ear to the brain. It is responsible for sending information about hearing and balance to the brain. The nerve normally is wrapped in layers of specialized cells called Schwann cells. An acoustic neuroma develops when the Schwann cells that surround the auditory nerve grow at an abnormal rate. This problem sometimes is called an acoustic or vestibular schwannoma. If an acoustic neuroma is not diagnosed or treated, it can grow through the skull bones that make up the middle ear and press on important structures in the brain.

The main symptoms of an acoustic neuroma — dizziness, hearing loss and ringing in the ears (tinnitus) — are caused by the tumor pressing on the auditory nerve. If the tumor grows large enough, it also may press on other nearby nerves and cause weakness, pain or tingling in the face. Although acoustic neuromas are not cancerous, they can become life threatening if they grow so large that they press on parts of the brain that control vital body functions.

No one knows what causes these tumors to develop. In most cases, the tumor grows only on one side of the head, and is diagnosed between the ages of 30 and 50. Acoustic neuromas in children are very rare. People with a hereditary disease called neurofibromatosis have a higher risk of developing acoustic neuromas, and can develop tumors in both ears. About 10 percent of all acoustic neuromas occur in people with neurofibromatosis. Some studies also have linked acoustic neuromas to long-term exposure to loud noises.

Symptoms

Acoustic neuromas generally grow slowly, so the symptoms develop gradually and are easy to miss or misinterpret. The earliest and most common symptoms of an acoustic neuroma are:

• Loss of hearing in one ear (this usually is gradual, but can occur suddenly in some cases)
• Tinnitus, a ringing, buzzing or noisy sound in the ear that may distort normal hearing

Less common symptoms include:

• Dizziness
• Loss of balance or clumsiness
• Facial weakness, pain, numbness or tingling
• Headache
• A feeling of something clogging the ear
• Mental confusion

Diagnosis

Because the symptoms of acoustic neuroma are often subtle and slow to develop, they can be missed easily in their early stages. Gradual hearing loss, especially if it occurs only in one ear, always should be checked by a physician.