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.
Acoustic Neuroma Treatments
There are three main courses of treatment for acoustic neuroma:
Observation is also called watchful waiting. Because acoustic neuromas are not cancerous and grow slowly, immediate treatment may not be necessary. Often doctors monitor the tumor with periodic MRI scans and will suggest other treatment if the tumor grows a lot or causes serious symptoms.
Surgery for acoustic neuromas may involve removing all or part of the tumor.
There are three main surgical approaches for removing an acoustic neuroma:
Translabyrinthine, which involves making an incision behind the ear and removing the bone behind the ear and some of the middle ear. The upside of this approach is that it allows the surgeon to see an important cranial nerve (the facial nerve) clearly before removing the tumor. The downside of this technique is that it results in permanent hearing loss.
Retrosigmoid/sub-occipital, which involves exposing the back of the tumor by opening the skull near the back of the head. This approach can be used for removing large tumors and offers the possibility of preserving hearing.
Middle fossa, which involves removing a small piece of bone above the ear canal to access and remove small tumors confined to the internal auditory canal, the narrow passageway from the brain to the middle and inner ear. Using this approach may enable surgeons to preserve a patient's hearing.