Acoustic Neuroma

An acoustic neuroma is a noncancerous (benign), often slow-growing tumor of the nerve that connects the ear to the brain. It is located behind the ear adjacent to the brain.

Causes

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, when in both ears is often linked with the rare 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
  • Numbness in the face or one ear
  • Pain in the face or one ear
  • Weakness of the face

Exams 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:

  • Facial drooping on one side
  • Unsteady walk

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

  • Head CT
  • Hearing test (audiology)
  • Test of equilibrium and balance (electronystagmography)

Treatment

Surgery

Goals of surgery are to remove the tumor and prevent paralysis of the face. Preserving hearing is more difficult. If a tumor is removed when it is very small, hearing may be preserved. You cannot get back any hearing that is lost before surgery. Large tumors usually result in total loss of hearing on the affected side.

Large tumors may also press down on nerves important for movement and feeling in the face. These tumors can typically be safely removed, but the surgery often leads to paralysis of some muscles of the face.

Extremely large tumors may also press on the brainstem, threatening other nerves and preventing the normal flow of cerebrospinal fluid. This can lead to a build-up of fluid (hydrocephalus), which can increase pressure in the head and can be life-threatening. Goals of surgery in these cases are to treat the hydrocephalus and relieve pressure on the brainstem.

Stereotactic radiosurgery, a form of radiation therapy

The goal is to slow or stop the tumor growth, not to cure or remove the tumor.

Radiosurgery is often performed.

Sometimes during brain surgery to treat acoustic neuromas, not all of the tumor can be safely removed, and some of the tumor must be left behind. Radiosurgery is often used after surgery in these cases to treat the tumor that remains.

Radiosurgery is only appropriate for small and medium sized tumors, so that radiation damage to surrounding tissues can be minimized.

Like brain surgery, radiosurgery can sometimes result in paralysis of the face or loss of hearing.

Observation

Since these tumors usually grow very slowly, small tumors that have few or no symptoms can be safely watched with regular MRI scans and left untreated unless they grow dangerously.
Very often elderly patients will die of other natural causes before small, slow growing tumors show symptoms.

Outlook (Prognosis)

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

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