An acoustic neuroma is a benign (noncancerous) tumor on the eighth cranial nerve leading from the brainstem to the ear. This nerve is involved in hearing and maintaining equilibrium. Acoustic neuromas grow relatively slowly.

Causes

The exact cause of an acoustic neuroma is unknown.

Risk Factors

A risk factor is something that increases your chances of getting a disease or condition.

Risk factors include:

• Age: 30-60 (Average age of diagnosis is 50)

• History of the disease neurofibromatosis type 2 (for bilateral neuromas only, which are very rare)

Symptoms

The first symptoms of an acoustic neuroma include:

• Gradual hearing loss in one ear

• Decrease in sound discrimination, especially when talking on the telephone

• Ringing in the ears, called tinnitus

As the neuroma gradually enlarges, symptoms may include:

• Balance problems

• Facial numbness and tingling

• Weakness of the facial muscles

Finally, if headaches or mental confusion occurs, the tumor may be life threatening. A doctor should be contacted immediately.

Diagnosis

The doctor will ask about your symptoms and medical history, and examine your ears and nervous system. Tests may include:

• Audiogram–A test that measures hearing in both ears.

• Auditory Brainstem Response Test (ABR, BAER, or BSER)–A test that measures the rate of electric impulses traveling from the inner ear to the brainstem. A slowed or absent impulse may indicate the presence of an acoustic neuroma. This test is almost always abnormal in the presence of an acoustic neuroma.

• Electronystagmography–a test for balance. Cold and warm water or air is insterted in the ear canal, and the resulting dizziness and rapid eye movement (nystagmus) is recorded.

• MRI Scan–A test that uses magnetic waves to make pictures of the inside of the body.

• CT Scan–A type of x-ray that uses a computer to make pictures of the inside of the body.

Treatment

Treatment depends on your age, general health, the size and location of the tumor, and its rate of growth. Treatment may include:

Observation–If the tumor is very small, your doctor may just monitor its growth. This is common among people over age 70.

Microsurgical Removal–As the tumor grows and/or hearing becomes impaired, removal of the tumor may be necessary. The surgical approach depends on the size and location of the tumor. Complications of surgery may include permanent hearing loss and/or paralysis of facial muscles on the affected side.

Radiation Therapy (or Radiotherapy)–The use of radiation to kill cells and shrink tumors. Radiation is expected to prevent further growth of the tumor. Radiation may be used when tumors are small and surgery is not possible. This method may preserve hearing.

Prevention

There are no guidelines for preventing the development of an acoustic neuroma because the cause is not usually known.

RESOURCES:

American Academy of Audiology
http://www.audiology.org

Acoustic Neuroma Association
http://www.anausa.org

International Radiosurgery Association
http://www.irsa.org/about_us.html

References:

Acoustic Neuroma Association website. Available at: http://www.anausa.org. Accessed October 13, 2005.

The American Otological Society. Available at: http://www.otology-neurotology.org/AOS/AOS-home.html. Accessed October 13, 2005.

Rowland LP, et al. Merritt’s Neurology. Philadelphia, PA: Lippincott Williams and Wilkins; 2000.