Medical Edge Newspaper Column

Options for Treating Acoustic Neuroma

Oct. 20, 2007
Dear Mayo Clinic:
I'm 59 and have been diagnosed with an acoustic neuroma. I've been to a surgeon and his explanation of the surgical procedure has me so frightened that I've chosen to do nothing. I have many bouts of dizziness and some hearing loss. Could you better explain the surgery as well as the benefit or drawbacks of radiation?

Answer:
Acoustic neuromas are noncancerous (benign) brain tumors that develop most often in the balance (vestibular) nerve cells in the eighth cranial nerve, which carries sound and balance information from your inner ear to your brain. These tumors — vestibular schwannomas — are commonly called acoustic tumors or acoustic neuromas.

In most people, these tumors grow slowly over several months or years. As they grow, acoustic neuromas usually cause progressive hearing loss, ringing in the affected ear and balance problems. Large tumors (3 to 4 centimeters) can cause facial numbness, facial weakness and twitching, headaches and coordination problems. Ultimately, extremely large (more than 4 centimeters) untreated tumors can put pressure on your brain stem and become life threatening.

Because of the high sensitivity and accuracy of magnetic resonance imaging (MRI), diagnosing an acoustic neuroma today is easier than it once was. MRI can reliably follow a tumor's growth pattern. This allows doctors to advise some patients to periodically return for hearing tests and follow-up MRI studies to determine the growth rate and progression of the tumor, rather than recommending surgery right away.

Treatment recommendations should be based on your age, general health, occupation, level of hearing loss, tumor size and experience of the physician team. Several options are available to treat acoustic neuromas, including continued observation, stereotactic radiosurgery (see below), fractionated radiotherapy (radiation therapy of the entire area of the brain where the tumor is located, usually reserved for very large tumors) and surgical removal.

For example, an elderly person with other significant health issues who has a small acoustic neuroma and few symptoms might be encouraged to have follow-up hearing tests and MRI studies every six to 12 months. If the tumor grows or symptoms progress, the physician may recommend the patient consider stereotactic radiosurgery (Gamma Knife) — radiation therapy that is delivered precisely to a tumor in one dose without the need for an incision. This one-day outpatient procedure uses focused radiation to try to halt tumor growth.

The success rate for stereotactic radiosurgery, that is, preventing further tumor growth, is approximately 93 percent with 15 years of follow-up. Stereotactic radiosurgery is not usually employed for tumors greater than 3 centimeters. The hearing preservation rate is approximately 50 percent, and the risk of any facial weakness is less than 1 percent. The timing and type of treatment are primarily based on the size of the tumor and how much hearing remains. Neither surgery nor radiation treatments can restore or improve hearing once it is lost.

Several surgical approaches are available for removing an acoustic neuroma, and some of them have the potential to preserve hearing. The retrosigmoid approach (behind the ear) or the middle fossa approach (above the ear) both allow for the possibility of removing the tumor and saving hearing. The transmastoid approach goes through the inner ear and sacrifices hearing. For most people who can safely undergo surgery to remove the tumor, the success is high, with only a 1 percent to 2 percent recurrence rate. Similarly, serious complications that could result from the surgery — stroke, infection, long-term facial paralysis or weakness, cerebrospinal fluid leakage or death — are rare when the operation is performed by an experienced team. The larger the tumor, the greater the risks resulting from any treatment.

"To do nothing" is not a good management strategy. Most acoustic neuromas eventually grow. Periodically checking with your surgeon to monitor your symptoms, hearing loss and change in tumor size is crucial to making the best and most timely treatment decisions. If you're uneasy about the treatment options your surgeon recommends, consider getting a second opinion. A physician team experienced in treating acoustic neuromas should be able to review your previous MRI results and hearing tests, evaluate your symptoms and advise you about the best treatment strategy.

— Charles Beatty, M.D., Otorhinolaryngology, and Michael Link, M.D., Neurologic Surgery, Mayo Clinic, Rochester, Minn.