What Is an Acoustic Neuroma?
An
acoustic neuroma is a benign (noncancerous), usually slow-growing tumor that develops from the nerves associated with balance and hearing that supply the inner ear. It comes from an overproduction of Schwann cells -- the cells that normally wrap around nerve fibers like the skin of an onion to help support and insulate the nerves.
Other names for an acoustic neuroma include:
Unilateral Versus Bilateral
An acoustic neuroma can affect one or both ears. When one ear is affected, it's known as unilateral acoustic neuroma. When both ears are affected, it's known as bilateral acoustic neuroma.
Unilateral Acoustic Neuroma
Unilateral acoustic neuroma affects only one ear. This type accounts for approximately 8 percent of all tumors inside the skull. One out of every 100,000 individuals per year develops an acoustic neuroma. Symptoms may develop at any age, but usually appear between the ages of 30 and 60. This is not a hereditary condition.
Bilateral Acoustic Neuroma
Bilateral
acoustic neuromas affect both hearing nerves and are usually associated with a genetic disorder called neurofibromatosis type 2 (NF2). Half of affected individuals have inherited the disorder from an affected parent and half seem to have a mutation for the first time in their family. Each child of an affected parent has a 50 percent chance of inheriting the disorder.
Unlike those with a unilateral acoustic neuroma, individuals with NF2 usually develop
acoustic neuroma symptoms in their teens or early adulthood. In addition, people with NF2 usually develop multiple brain- and spinal cord-related tumors. They can also develop tumors of the nerves associated with:
- Swallowing
- Speech
- Eye and facial movement
- Facial sensation.
Determining the best way to manage bilateral acoustic neuromas as well as the additional nerve, brain, and spinal cord tumors is more complicated than deciding how to treat a unilateral acoustic neuroma. Further research is needed to determine the best treatment for individuals with neurofibromatosis type 2.
Causes of Acoustic Neuroma
No one knows the exact
causes of acoustic neuroma. Doctors cannot always explain why one person gets the condition and another does not. However,
acoustic neuroma research has shown that people with certain risk factors for this condition are more likely than others to develop it. A risk factor is anything that increases a person's chance of developing a disease.
Specific risk factors include:
- Age
- Family history of neurofibromatosis type 2.
Because of its location, an
acoustic neuroma can produce serious symptoms or even death by compression of important structures, including the cranial nerves and the brainstem.
As the acoustic neuroma grows, it presses against the nerves associated with hearing and balance. This results in early
symptoms of acoustic neuroma, such as:
- One-sided or high-tone hearing loss
- Ringing in the ear (tinnitus)
- Dizziness
- Loss of balance.
As the tumor grows, later symptoms may include:
- Headaches
- Facial numbness
- Weakness of facial muscles
- Paralysis of facial muscles.
Diagnosing Acoustic Neuroma
The tests include:
- A hearing test (audiogram)
- Computerized tomography (CT) scans, enhanced with intravenous dye (contrast)
- Magnetic resonance imaging (MRI), enhanced with intravenous dye (contrast).
These tests are critical in the early detection of an acoustic neuroma, and are helpful in determining the location and size of a tumor and in planning its removal.
Making an early diagnosis is the key to preventing serious consequences of an acoustic neuroma. Once a diagnosis is made, treatment options include:
The doctor can describe the options available for treating your acoustic neuroma and the expected results of each. The two of you can work together to develop an
acoustic neuroma treatment plan that meets your medical needs and personal values. Choosing the most appropriate form of treatment is a decision that ideally involves both you and your healthcare team.
