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Definition
Acoustic neurinoma is a benign tumor that may develop on the hearing and balance nerves near the inner ear.
The tumor results from an overproduction of Schwann cells - small, sheet-like cells that normally wrap around nerve fibers like onion skin and help support the nerves.
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Description
When growth is abnormally excessive, Schwann cells bunch together, pressing against the hearing and balance nerves, often causing gradual hearing loss, tinnitus (ringing in the ears), and dizziness.
If the tumor becomes large, it can interfere with the facial nerve, causing partial paralysis, and eventually pressing against brain structures, becoming life-threatening.
There are two types of acoustic neurinomas: unilateral and bilateral. Unilateral neurinomas affect only one ear and account for approximately 8 percent of tumors inside the skull.
Symptoms may develop at any age, but usually occur between the ages of 30 and 60 years.
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Causes and Risk Factors
Bilateral acoustic neurinomas, which affect both ears, are hereditary. Inherited from one's parents, this tumor results from a genetic disorder known as neurofibromatosis-2 (NF2).
Affected individuals have a 50 percent chance of passing this disorder on to their children. Unlike those with a unilateral acoustic neurinoma, individuals with NF2 usually develop symptoms in their teens or early adulthood.
Because NF2 patients usually have multiple tumors, the surgical procedure is more complicated than the removal of a unilateral acoustic neurinoma.
Scientists believe that both types of acoustic neurinoma form following a loss of the function of a gene on chromosome 22.
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Diagnosis
Early diagnosis of an acoustic neurinoma is key to preventing its serious consequences. Unfortunately, early detection of the tumor is sometimes difficult, because the symptoms may be subtle and may not appear in the beginning stages of growth. Also, hearing loss, dizziness, and tinnitus are common symptoms of any middle and inner ear problems. Therefore, once the symptoms appear, a thorough ear examination and hearing test are essential for proper diagnosis.
Computerized tomography(CT) and magnetic resonance imaging (MRI) are helpful in determining the location and size of a tumor and also in planning its removal.
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Treatment
If an acoustic neurinoma is removed surgically when it is still very small, hearing may be preserved and accompanying symptoms may go away. As the tumor grows larger, surgical removal is often more complicated because the tumor may become firmly attached to the nerves that control facial movement, hearing and balance.
The removal of tumors attached to hearing, balance or facial nerves can make the patient's symptoms worse, because sections of these nerves must also be removed with the tumor. As an alternative to conventional surgical techniques, radiosurgery may be used to reduce the size or limit the growth of the tumor.
Radiosurgery, utilizing carefully focused radiation, is sometimes performed on the elderly, on patients with tumors on both hearing nerves, or on patients with a tumor growing on the nerve of their only hearing ear.
If the tumor is not removed, MRI is used to carefully monitor its growth.
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Questions to Ask Your Doctor
Are both ears affected (bilateral) or is only one ear affected (unilateral)?
Is it neurofibromatosis? If so, is it hereditary?
Is the diagnosis definitive or could the symptoms be caused by other ear problems?
Is surgery required? Why does it have to be done?
What would happen if surgery is not performed?
What are the risks and benefits of surgery?
Will surgery affect the facial nerves, balance and hearing?
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