What Is an Acoustic Neuroma?
An acoustic neuroma is a benign, slow-growing tumor that develops on the nerve connecting the inner ear to the brain. This nerve has two different parts: One is involved with transmitting auditory signals to the brain while the other helps send balance signals to the brain. The tumor tends to grow at a rate of one to two millimeters each year but sometimes faster or not at all.
In rare cases the tumor grows rapidly, becoming large enough to press against the brain and interfere with vital functions. Large tumors can put pressure on nearby cranial nerves that control facial muscles and sensations, affecting facial function. If the tumors become large enough to put pressure on the brainstem or cerebellum — which control motor and sensory function, and play a role in cardiac and respiratory function — they can be deadly.
If the acoustic neuroma is the result of a genetic disorder, it will typically develop in both ears due to a malfunctioning gene in a specific chromosome. This gene normally produces a protein that helps control the growth of certain cells covering the nerves, but without this protein, the cells overproduce and wrap around the nerve, leading to the formation of the tumor. This disorder is called neurofibromatosis type 2 and is rare; neurofibromatosis accounts for only 5% of acoustic neuromas.
Medical researchers are not yet certain what causes an acoustic neuroma to materialize randomly in the other 95% of cases, but exposure to high doses of radiation, especially to the head and neck, may be a risk factor.
Early symptoms are often subtle and are usually a direct result of the tumor disrupting the auditory nerve, nearby blood vessels, or brain structures. Symptoms are likely to change or progress as the tumor increases in size, but it’s possible for even a small tumor to cause significant signs and symptoms. You may experience:
- Gradual hearing loss, usually affecting one ear (although, in some cases, hearing loss may be sudden)
- Tinnitus, or ringing in the ear, on one side
- Dizziness, clumsiness, or loss of balance
- Facial numbness or weakness
- Changes in the taste of food
- Difficulty swallowing or hoarseness
Many will assume these symptoms are part of normal changes that take place as the body ages. Speak to your doctor if you experience any combination of these symptoms, as they may signal a condition that requires urgent attention.
Depending on how quickly or slowly the tumor is growing, immediate treatment may not be necessary. Monitoring the tumor’s rate of growth will help your doctor determine what treatment is needed.
Surgery may involve removing all or part of the tumor. Typically, a small section of bone above or behind the ear canal is removed, allowing the surgeon to view and access the nerve pathway and effectively remove the tumor. Patients may lose part or all of their functional hearing in the affected ear.
In some cases, radiation therapy delivered directly to the site of the tumor can limit damage to the surrounding tissue and may help to preserve hearing outcomes better than more conventional surgical techniques. The tumor’s growth may slow or stop, and it might also recede to a size that allows for comfortable living with mild or no symptoms.