What Is An Acoustic Neuroma?
Acoustic neuromas are benign (noncancerous) tumors arising from abnormal growth in the cells of the protective sheath (myelin) that surrounds the eighth cranial nerve (or auditory nerve). These tumors tend to grow very slowly, eventually leading to partial or total hearing loss in the affected ear. If left untreated, the tumor may continue to expand and press on several other cranial nerves, causing dizziness and loss of balance, facial pain, or double vision. In some cases an acoustic neuroma grows large enough to involve the brain stem, leading to loss of muscle coordination (cerebellar ataxia) on the affected side of the body. However, most patients seek treatment before such complications occur.
Prognosis depends on the size of the tumor but is generally quite favorable.
Who Gets Acoustic Neuroma?
While acoustic neuroma is the most common tumor of cranial nerves and represents about 5 percent of primary brain tumors, it is still a rather uncommon disorder. Incidence is highest among those between the ages of 30 and 50.
- Partial or complete hearing loss in one ear (or rarely, in both ears). An inability to hear in one ear when using the telephone is often the first sign.
- Persistent ringing or buzzing in the affected ear (tinnitus).
- Ear pain (in some cases).
- Symptoms that may appear if a tumor affects other nerves or the cerebellum: dizziness and vertigo; facial pain; double vision; loss of muscle coordination on the affected side of the body.
- The cause of acoustic neuromas is unknown, although some studies link the problem to a genetic lack of certain proteins that normally prevent tumor growth in the tissue surrounding nerve fibers.
- A small fraction of cases occur in association with a hereditary disorder called neurofibromatosis, characterized by widespread abnormalities in the nervous system, skin, and bones. Neurofibromatosis can be associated with acoustic neuromas that affect both auditory nerves. (In almost all other cases, neuromas develop only in one auditory nerve.)
- Patient history and a hearing test (audiogram) may be strongly suggestive of the diagnosis. Evaluation by an otolaryngologist (an ear, nose, and throat specialist) is essential for any signs of hearing loss.
- CT (computed tomography) scans or MRI (magnetic resonance imaging) can confirm the presence of even very small acoustic neuromas.
- The only effective cure for acoustic neuromas is surgical removal of the tumor. Current microsurgery techniques performed by surgeons experienced in using them often yield favorable results, making it possible to preserve hearing for many patients (especially those who had good hearing preoperatively). Occasionally, however, some degree of permanent hearing loss in the affected ear is inevitable, and sometimes the surgery itself can result in weakness in the facial muscles, numbness, or other neurological symptoms owing to unavoidable damage to surrounding nerves.
- Radiation treatment may be an option to surgery for some patients. Though not a cure, the treatment slows tumor growth in the majority of cases. Treatment with a gamma knife is a special form of radiation treatment using focused beams. This treatment has less risks than surgery and may provide long term benefit to many patients.
- There is no known way to prevent the development of acoustic neuromas.
When To Call Your Doctor
- Consult a doctor regarding any signs of hearing loss. You will most likely be referred to an audiologist or an otolaryngologist for testing and examination.
Reviewed by Joseph V. Campellone, M.D., Division of Neurology, Cooper University Hospital, Camden, NJ. Review provided by VeriMed Healthcare Network.