An acoustic neuroma is a low-grade tumor. It is on the eighth cranial nerve leading from the brainstem to the ear. This nerve is involved in hearing and ...
An acoustic neuroma is a tumor that grows on the nerve leading from the brainstem to the ear. This nerve plays a role in hearing and in maintaining your balance. An acoustic neuroma grows relatively slowly. It is a benign tumor which means it is not cancerous. However, this condition can still cause serious problems.
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The exact cause of an acoustic neuroma is unknown.
Factors that may increase your chance of an acoustic neuroma include:
- Age: 30-60 (average age of diagnosis is 50)
- History of the disease neurofibromatosis type 2 (NF2)
- Family history of NF2
The first symptoms of an acoustic neuroma include:
- Gradual hearing loss in one ear with near normal hearing in the other ear
- Decrease in sound discrimination, especially when talking on the telephone
- Ringing in the affected ear, called tinnitus
As the neuroma gradually grows larger, symptoms may include:
- Balance problems
- Facial numbness and tingling
- Weakness of the facial muscles on the side of the tumor
If headaches or mental confusion occurs, the tumor may be life threatening. Call your doctor right away.
The doctor will ask about your symptoms and medical history. Your ears will be examined. Your doctor will also do tests for your nervous system. Tests may include:
- Audiogram—a test that measures hearing in both ears
- Auditory brainstem response test—a test that measures the rate of electric impulses traveling from the inner ear to the brainstem, almost always abnormal in the presence of an acoustic neuroma
- Electronystagmography—Cold and warm water or air is inserted in the ear canal, and the resulting dizziness and rapid eye movement are recorded.
- MRI scan—a test that uses magnetic waves to make pictures of the inside of the head
- CT scan—a type of x-ray that uses a computer to make pictures of the inside of the head
The exact type of operation done depends on the size of the tumor and the level of hearing in the affected ear. If the tumor is very small, hearing may be saved. As the tumor grows larger, surgical removal is more difficult because the tumor may have thinned out the nerves that control facial movement, hearing, and balance and may also have affected other nerves and structures of the brain.
Surgery offers immediate treatment but with higher up-front risk. The risks of surgery include: cerebrospinal fluid leak (5% to 17% risk), meningitis, hydrocephalus and/or a wound infection. Other common effects include a period of headaches or balance difficulties or facial weakness. These risks increase with size of the tumor and the type of surgical procedure performed.
Gamma Knife Radiosurgery
The goal of Gamma Knife on acoustic neuromas is tumor volume control rather than tumor removal. Gamma Knife's tumor control rate is about 95%. The risks of radiosurgery are less than those for regular surgery.
As acoustic neuroma may be slow growing, observation may be acceptable for some patients. This is especially the case for elderly or frail patients with mild symptoms where the risks of therapy may be greater and where the tumor may not grow during their lifespan.
Those with smaller tumors may also decide upon "watchful waiting," getting frequent MRIs and audiograms. In this situation it is highly likely that treatment may be needed, but there is potential to postpone therapy for many years. Treatment may proceed when tumor growth is confirmed or symptoms worsen.
There are no guidelines for preventing acoustic neuroma because the cause is not usually known.