What is acoustic neuroma?
Acoustic neuroma is a rare non-cancerous tumor. It grows slowly from an overproduction of Schwann cells. The tumor then presses on the hearing and balance nerves in the inner ear. Schwann cells normally wrap around and support nerve fibers. A large tumor can press on the facial nerve or brain structures.
There are 2 types of acoustic neuromas:
Unilateral acoustic neuromas. This type affects only one ear. It is the most common type of acoustic neuroma. This tumor may develop at any age. It most often occurs between the ages of 30 and 60. Acoustic neuroma may be the result of nerve damage caused by environmental factors. No environmental factor has been shown to cause acoustic neuromas.
Bilateral acoustic neuromas. This type affects both ears and is inherited. It is caused by a genetic problem called neurofibromatosis-2 (NF2).
What are the causes of acoustic neuroma?
Acoustic neuroma can be caused by:
People who have a disease called neurofibromatosis type 2 (NF2) are at higher risk. NF2 can run in families.
What are the symptoms of acoustic neuroma?
These are the most common symptoms of acoustic neuroma:
Hearing loss on one side, can’t hear high frequency sounds
Feeling of fullness in the ear
A ringing in the ear (tinnitus), on the side of the tumor
Balance problems or unsteadiness
Facial numbness and tingling with possible, though rare, paralysis of a facial nerve
Headaches, clumsy gait, and mental confusion
The symptoms of acoustic neuroma may look like other conditions or health problems. Always consult your health care provider for a diagnosis.
How is acoustic neuroma diagnosed?
Because symptoms of acoustic neurinomas resemble other middle and inner ear conditions, they may be difficult to diagnose. Preliminary diagnostic procedures include ear examination and hearing test. Computerized tomography (CT) and magnetic resonance imaging (MRI) scans help to determine the location and size of the tumor. Early diagnosis offers the best opportunity for successful treatment.
A diagnosis of acoustic neuroma involves:
Hearing test (audiometry): A test of hearing function, which measures how well the patient hears sounds and speech, is usually the first test performed to diagnose acoustic neuroma. The patient listens to sounds and speech while wearing earphones attached to a machine that records responses and measures hearing function. The audiogram may show increased "pure tone average" (PTA), increased "speech reception threshold" (SRT) and decreased "speech discrimination" (SD).
Brainstem auditory evoked response (BAER): This test is performed in some patients to provide information on brain wave activity as a response to clicks or tones. The patient listens to these sounds while wearing electrodes on the scalp and earlobes and earphones. The electrodes pick up and record the brain's response to these sounds.
Scans of the head: If other tests show that the patient may have acoustic neuroma, magnetic resonance imaging (MRI) is used to confirm the diagnosis. MRI uses magnetic fields and radio waves, rather than x-rays, and computers to create detailed pictures of the brain. It shows visual “slices” of the brain that can be combined to create a three-dimensional picture of the tumor. A contrast dye is injected into the patient. If an acoustic neuroma is present, the tumor will soak up more dye than normal brain tissue and appear clearly on the scan. The MRI commonly shows a densely "enhancing" (bright) tumor in the internal auditory canal.
Treatment for Acoustic Neuromas
Acoustic neuromas can often be removed completely with surgery. However, many acoustic neuromas are so small that they may not need immediate treatment.
The treatment for acoustic neuromas depends on the size of the tumor and the patient’s age, general health and preferences, and may involve surgery, radiosurgery and sometimes observation.
Surgeons have developed several types of craniotomy to remove acoustic neuromas. Surgical craniotomy may use a suboccipital, translabyrinthine approach or middle fossa approach.
Surgery for larger tumors is complicated by the probable damage to hearing, balance, and facial nerves. Another treatment option is radiosurgery, which uses carefully focused radiation to reduce the size or limit the growth of the tumor.
For patients with smaller acoustic neuromas, surgery and radiation therapy are equally effective. Doctors may also recommend radiation therapy to treat older patients.
Radiosurgery treatments can be single or fractionated (multiple smaller treatments rather than one large one). Fractionated stereotactic radiosurgery (FSR) appears to offer very high rates of control with preservation of hearing and preservation of the facial strength.
For some slow-growing acoustic neuromas observation with delayed treatment may be acceptable. This is a common treatment option for elderly or infirm patients with mild symptoms where the risks of therapy may be greater and where the tumor may not grow during their lifespan.
Post-surgical treatment for acoustic neuromas
After treatment for acoustic neuroma, some patients experience hearing loss, cerebrospinal fluid leak, damage to the nerves in the face and other problems. Johns Hopkins offers comprehensive surgical treatment and rehabilitation care for all of these problems.
Surgical treatment for problems related to acoustic neuroma
The bone-anchored hearing aid (Baha) speech processor is a hearing aid that doctors surgically implant under the skin near the ear. The device grows into the skull bone and enhances the bone’s natural transmission of sound. The Baha speech processor transmits sound vibrations within the skull and inner ear that stimulate the nerves of the inner ear, enabling the patient to hear.
We may recommend a regular hearing aid instead of a Baha speech processor for some patients.
Patients with neurofibromatosis 2 often develop acoustic neuromas in both ears. This results in severe hearing problems or deafness in both ears. Cochlear implants can help provide a sense of sound to these patients and help them understand speech. The device consists of an external earpiece and a device that our doctors surgically implant under the skin near the ear.
Cochlear implants work by bypassing the damaged portions of the ear and directly stimulating the hearing nerve. They generate signals from the auditory nerve to the brain, which recognizes the signals as sound.
Cerebrospinal fluid leak is a common problem after surgical removal of an acoustic neuroma. Leaks are caused by a hole or tear in the dura, a membrane that covers the brain. Doctors closely monitor patients for cerebrospinal fluid leak, and if it occurs, they can perform a procedure to block the hole that is leaking cerebrospinal fluid.
Repairing facial nerve damage
If the patient’s facial nerves are damaged by the acoustic neuroma, plastic surgeons may perform procedures to help restore movement in the face.
What are the complications of acoustic neuroma?
If the tumor gets big enough it can press against the brain stem. This can affect neurological function or become life threatening.
Acoustic neuroma is a non-cancerous tumor. It affects hearing and balance when the tumor presses on the nerve the nerves in the inner ear.
It must be diagnosed using hearing tests and imaging tests.
Treatment can include watching and waiting, surgery, or radiation. It is a rare tumor that often affects middle-aged people.
Tips to help you get the most from a visit to your health care provider:
Before your visit, write down questions you want answered.
Bring someone with you to help you ask questions and remember what your provider tells you.
At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
If you have a follow-up appointment, write down the date, time, and purpose for that visit.
Know how you can contact your provider if you have questions.