Acoustic Neuromas - Patient Information

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Definition

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 causes 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 too rapidly. 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% of all acoustic neuromas occur in people with neurofibromatosis. Some studies also have linked acoustic neuromas to long-term exposure to loud noises.

Treatment

*From the National Institute of Health

Early diagnosis of a vestibular schwannoma is key to preventing its serious consequences. There are three options for managing a vestibular schwannoma: (1) surgical removal; (2) radiation; and (3) monitoring. Typically, the tumor is surgically removed (excised). The exact type of operation done depends on the size of the tumor and the level of hearing in the affected ear. If the tumor is very small, hearing may be saved and accompanying symptoms may improve. As the tumor grows larger, surgical removal is more complicated because the tumor may have damaged the nerves that control facial movement, hearing, and balance and may also have affected other nerves and structures of the brain.

The removal of tumors affecting the hearing, balance, or facial nerves can make the patient's symptoms worse because sections of these nerves may also need to be removed with the tumor.

As an alternative to conventional surgical techniques, radiosurgery (that is, radiation therapy--the "gamma knife" or LINAC) may be used to reduce the size or limit the growth of the tumor. Radiation therapy is sometimes the preferred option for elderly patients, patients in poor medical health, patients with bilateral vestibular schwannoma (tumor affecting both ears), or patients whose tumor is affecting their only hearing ear. In some cases, usually elderly or medically infirm patients, it may be reasonable to "watch" the tumor for growth. Repeat MRI over time is used to carefully monitor the tumor for any growth.

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