Also known as an acoustic neuroma, a vestibular schwannoma is a benign, usually slow-growing tumor that develops near the back of the skull in the eighth cranial nerve, which controls hearing and balance. Though the tumor is itself benign, it compresses the surrounding nerves as it grows, causing usually unilateral (affecting only one ear) hearing loss, tinnitus (ringing in the ear), unsteadiness and vertigo (dizziness). In rare cases, the facial nerve may also be affected, resulting in facial weakness or paralysis on the side of the tumor. A vestibular schwannoma can be life-threatening if it becomes large enough to exert pressure on the brainstem and cerebellum and can cause hydrocephalus (fluid buildup in the brain).
Vestibular schwannomas are most likely the result of a loss of function in a gene that controls the growth of Schwann cells, cells that insulate nerves. This malfunction leads to uncontrolled Schwann cell production, which results in a tumor. Unilateral vestibular schwannomas account for the majority of cases, and in these cases it is unknown why the offending genetic malfunction occurs. Bilateral vestibular schwannomas affecting both hearing nerves, however, are generally associated with a genetic condition called neurofibromatosis type 2 (NF2), in which patients inherit the defective Schwann-cell-production gene from their parents.
Early detection of a vestibular schwannoma can be difficult—the symptoms may be confused with other middle and inner ear problems, may be subtle or may not appear at all. Early diagnosis is crucial, however, to preventing serious consequences. Unilateral symptoms may point to a vestibular schwannoma over other conditions, so consult your doctor if you notice hearing loss or persistent ringing in one ear or trouble with your balance. Only after a thorough evaluation involving an ear examination, a hearing test and CT and/or MRI scans can a proper diagnosis be given.
If you have been diagnosed, it is time to consider treatment options. Depending on the size of the tumor, your doctor may recommend Gamma Knife radiosurgery, which, despite its name, doesn’t use a knife. Instead, it focuses beams of gamma radiation on a vestibular schwannoma to limit the growth of the tumor. Doctors at the Boston Gamma Knife Center at Tufts Medical Center—northern New England’s first and only Gamma Knife Center—use this state-of-the-art technology to offer a noninvasive treatment option that is safer than traditional surgery.
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