Acoustic neuromas: Why Balance Could be a Problem

Not all growths are cancerous. A good example is acoustic neuroma which is a growth that occurs on the eighth cranial nerve. This nerve connects the brain with the inner ear. The nerve has two parts with different functions; the first part is for sound transmission while second one deals with balance information from brain to inner ear.

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.

Acoustic Neuroma Symptoms

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
  • Facial weakness
  • Taste changes
  • Difficulty swallowing and hoarseness
  • Headaches
  • Clumsiness or unsteadiness
  • Confusion

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It is still not yet clear what exactly is the cause of Acoustic neuromas but research still continues however it is believed that genes could be one of the main causes.

While not an acoustic neuroma “cause,” studies have found a couple of factors that may increase a person’s risk of developing it. Specific risk factors for acoustic neuroma include age and family history of neurofibromatosis type 2.

 Neurofibromatosis type 2 (NF-2) is a rare inherited disorder characterized by the development of acoustic neuromas on both auditory nerves. The disease is also characterized by the development of malignant central nervous system tumors. Half of all affected individuals have inherited neurofibromatosis 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.

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Doctors say that there might be difficulty when it comes to diagnosing acoustic neuroma. This is because its symptoms are very similar to those of other middle and inner ear conditions. It is still better for the disease to be diagnosed earlier than later.

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.

  • 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.

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