Acoustic neuroma, or vestibular schwannoma, is a noncancerous and usually slow-growing tumor that develops on the main nerve leading from the inner ear to the brain. Because branches of this nerve directly influence balance and hearing, pressure from an acoustic neuroma can cause hearing loss, ringing in the ear and unsteadiness.
An acoustic neuroma is a tumor that arises from the Schwann cells forming the sheath (covering) of the vestibulocochlear nerve. As the tumor grows, it expands from its origin inside the internal auditory canal out into the space between the brainstem and the temporal bone known as the cerebellopontine angle.
The cause of acoustic neuromas appears to be a malfunctioning gene on chromosome 22. Normally this gene produces a protein that helps control the growth of Schwann cells covering the nerves. What makes this gene malfunction isn’t clear.
The signs and symptoms of acoustic neuroma develop from the tumor pressing on the adjacent nerves, nearby blood vessels, or brain structures. As the tumor grows, it may be more likely to cause signs and symptoms, although tumor size doesn’t always determine effects. It’s possible for a small tumor to cause significant problems. Some of the symptoms associated with acoustic neuroma are hearing loss on one side, ringing in the affected ear, unsteadiness, loss of balance, dizziness, and facial numbness and weakness.
Because signs and symptoms of acoustic neuroma are likely to develop gradually and because symptoms such as hearing loss can be indicators of other middle and inner ear problems, it may be difficult for your doctor to detect the tumor in its early stages. Your doctor will need to conduct an ear exam in which he will do a hearing test, and do a diagnostic test such as an MRI to confirm the presence of an acoustic neuroma.
Once the acoustic neuroma has been eliminated, follow-up treatment consists of balance therapy. Most patients can return to close to their functioning level before the acoustic neuroma symptoms started. Vestibular rehabilitation consists of daily exercises prescribed by your physical therapist that retrain the brain to make use of the balance information it is still getting, whether from the inner ears or from other sources such as vision or feedback from muscles. Fortunately, the brain is flexible and can usually compensate for loss of unilateral or bilateral balance function