An acoustic neuroma is a noncancerous growth that develops on the eighth cranial nerve. Also known as the vestibulocochlear nerve, it connects the inner ear with the brain and has two different parts. One part is involved in transmitting sound; the other helps send balance information from the inner ear to the brain.
Acoustic neuromas -- sometimes called vestibular schwannomas or neurolemmomas -- usually grow slowly over a period of years. Although they do not actually invade the brain, they can push on it as they grow. Larger tumors can press on nearby cranial nerves that control the muscles of facial expression and sensation. If tumors become large enough to press on the brain stem or cerebellum, they can be deadly.
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The early symptoms of an acoustic neuroma are often subtle. Many people attribute the symptoms to normal changes of aging, so it may be a while before the condition is diagnosed.
The first symptom is usually a gradual loss of hearing in one ear, often accompanied by ringing in the ear (tinnitus) or a feeling of fullness in the ear. Less commonly, acoustic neuromas may cause sudden hearing loss.
Other symptoms, which may occur over time, include:
Problems with balance
Vertigo (feeling like the world is spinning)
Facial numbness and tingling, which may be constant or come and go
Difficulty swallowing and hoarseness
Clumsiness or unsteadiness
It's important to see your doctor if you experience these symptoms. Symptoms like clumsiness and mental confusion can signal a serious problem that requires urgent treatment.
Acoustic Neuroma Causes
There are two types of acoustic neuroma: a sporadic form and a form associated with a syndrome called neurofibromatosis type II (NF2). NF2 is an inherited disorder characterized by the growth of noncancerous tumors in the nervous system. Acoustic neuromas are the most common of these tumors and often occur in both ears by age 30.
NF2 is a rare disorder. It accounts for only 5% of acoustic neuromas. This means the vast majority are the sporadic form. Doctors aren't certain what causes the sporadic form. One known risk factor for acoustic neuroma is exposure to high doses of radiation.