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Acoustic neuroma

Definition

An acoustic neuroma is a slow-growing tumor of the nerve that connects the ear to the brain. This nerve is located behind the ear right under the brain.

An acoustic neuroma is benign, which means it does not spread to other parts of the body or invade the tissue around it. However, it can damage several important nerves as it grows.

Alternative Names

Vestibular schwannoma; Tumor - acoustic; Cerebellopontine angle tumor; Angle tumor

Causes, incidence, and risk factors

An acoustic neuroma is believed to occur when there is a defect in a gene that normally prevents tumors from forming. The cause of the genetic defect is not known. However, acoustic neuroma can be linked with the genetic disorder neurofibromatosis type 2 (NF2).

Acoustic neuromas are relatively uncommon.

Symptoms

The symptoms vary based on the size and location of the tumor. Because the tumor grows so slowly, symptoms usually start after the age of 30.

Common symptoms include:

• Abnormal sensation of movement (vertigo)
• Hearing loss in the affected ear that makes it hard to hear conversations
• Ringing (tinnitus) in the affected ear

Less common symptoms include:

• Difficulty understanding speech
• Dizziness
• Headache
  • Upon waking up in the morning
  • Wakes you from sleep
  • Worse when lying down
  • Worse when standing up
  • Worse when coughing, sneezing, straining, or lifting (Valsalva maneuver)
  • With nausea or vomiting
• Loss of balance
• Numbness in the face or one ear
• Pain in the face or one ear
• Sleepiness
• Vision problems
• Weakness of the face

Signs and tests

The health care provider may diagnose an acoustic neuroma based on your medical history, an examination of your nervous system, or tests.

Often, the physical exam is normal at the time the tumor is diagnosed. Occasionally, the following signs may be present:

• Drooling
• Facial drooping on one side
• Unsteady walk
• Dilated pupil on one side only (See: Eyes, pupils different size)

The most useful test to identify an acoustic neuroma is an MRI of the head. Other useful tests to diagnose the tumor and tell it apart from other causes of dizziness or vertigo include:

• Head CT
• Hearing test (audiology)
• Test of equilibrium and balance (electronystagmography)
• Test of hearing and brainstem function (brainstem auditory evoked response)
• Test for vertigo (caloric stimulation)

Treatment

Depending on the size and location of the tumor, you and your health care provider must decide whether to watch the tumor (observation) or try to remove the tumor.

Many acoustic neuromas are small and grow very slowly. Small tumors with few or no symptoms may be followed. Regular MRI scans will be done.

If they are not treated, some acoustic neuromas can damage the nerves involved in hearing, as well as the nerves responsible for movement and feeling in the face. Very large tumors can lead to a buildup of fluid (hydrocephalus) in the brain, which can be life-threatening.

Removing an acoustic neuroma is more commonly done for:

• Larger tumors
• Tumors that are causing symptoms
• Tumors that are growing quickly
• Tumors that are growing near a nerve or part of the brain that is more likely to cause problems

Surgery is done to remove the tumor and prevent further hearing loss or other nerve damage.

Stereotactic radiosurgery focuses high-powered x-rays on a small area. It is considered to be a form of radiation therapy, not a surgical procedure. It may be used:

• To slow down the growth of tumors that are hard to remove with surgery
• To treat patients who are unable to have surgery, such as the elderly or people who are very sick

Removing an acoustic neuroma can damage nerves, causing loss of hearing or weakness in the face muscles. This damage is more likely to occur when the tumor is next to or around the nerves.

Support Groups

Expectations (prognosis)

An acoustic neuroma is not cancer. The tumor does not spread (metastasize) to other parts of the body. However, it may continue to grow and press on important structures in the skull.

People with small, slow-growing tumors may not need treatment.

Once hearing loss occurs, it does not return after surgery.

Complications

• Brain surgery can completely remove the tumor in most cases.
• Most people with small tumors will have no permanent paralysis of the face after surgery. However, about two-thirds of patients with large tumors will have some permanent facial weakness after surgery.
• Approximately one-half of patients with small tumors will still be able to hear well in the affected ear after surgery.
• There may be delayed radiation effects after radiosurgery, including nerve damage, loss of hearing, and paralysis of the face.

Calling your health care provider

Call your health care provider if you experience new or worsening hearing loss or vertigo (dizziness).

Prevention

References

Brackmann DE, Arriaga MA. Neoplasms of the posterior fossa. In: Cummings CW, Flint PW, Haughey BH, et al, eds. Otolaryngology: Head & Neck Surgery. 5th ed. Philadelphia, Pa: Mosby Elsevier;2010:chap 177.

Battista RA. Gamma knife radiosurgery for vestibular schwannoma. Otolaryngol Clin North Am. 2009;42:635-654.

Sweeney P, Yajnik S, Hartsell W, Bovis G, Venkatesan J. Stereotactic radiotherapy for vestibular schwannoma. Otolaryngol Clin North Am. 2009;42:655-663.