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The inner ear is connected to the brain by the eighth cranial nerve, which is the vestibulocochlear nerve. The vestibular component of this nerve is responsible for maintaining one’s physical balance. Tumors of this nerve can cause balance and hearing problems, and when they grow bigger they can affect other parts of the brain and nearby nerves.
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What is an Acoustic Neuroma?
Acoustic neuromas are benign tumors of the 8th cranial nerve affecting mainly the vestibular function of the inner ear. It is a slow growing new growth near the brainstem and usually manifests initially as a gradual, one-sided hearing loss and ringing in the affected ear. Men and women are equally affected, and these usually occur at the age of 40 to 50 years.
With time it grows bigger and may affect other areas of the brain and ear, resulting in balance problems, one-sided facial weakness, numbness and tingling. Although benign the tumor may grow large enough to push the brain, cause swelling and eventually lead to death.
Balance and hearing tests may be done initially, but imaging techniques like MRI and CT scans are most useful in confirming its diagnosis.
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Treatment of Acoustic Neuroma
Treatment of acoustic neuromas depends on the patient’s age, general health condition, the size and rate of growth of the tumor. Conservative treatment and observation are usually advised for old patients, those with serious medical problems and those with small and slow growing tumors.
Radiation therapy is an option for small tumors and for partially resected tumors. It can be used to prevent further growth of the tumor and may also be done to reduce tumor size.
Surgery is indicated when the patient is young, other nervous functions are affected and if the tumor has grown big enough to compress the brain and other nerves. However, the complications of open surgery at or near the brainstem pose many risks on vital functions such as the respiratory and circulatory functions which may be compromised by the procedure.
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Minimally Invasive Surgery for Acoustic Neuroma
Because of the location and size of the tumor, possible complications of surgery are:
- Unilateral hearing loss
- Unilateral facial weakness or paralysis
- Leakage of the cerebrospinal fluid through the nose or ear
- Other nervous dysfunction or deficits including stroke
To minimize the occurrence of these complications minimally invasive techniques have been developed over the years for brain surgery such as that for acoustic neuromas. Minimally invasive neurosurgery involves the use of fiber optic telescopes and cameras that can be inserted through a small dime-sized hole in the skull behind the ear, through the nostrils or the sinuses. This allows the surgeon to obtain actual views of the brain anatomy on a monitor in the operating suite and use microscopes and small surgical instruments to resect the tumor. These endoscopes are flexible and can be manipulated to view hard to reach areas during traditional surgeries.
Computer-assisted imaging navigation may also be done to capture three-dimensional views of the brain and surrounding structures. This allows precision in identification and preservation of structures during surgery.
During the procedure continuous monitoring of the facial nerve, hearing and brain function are done to avoid damage to structures. Intra-operative MRIs may also be obtained to see that the tumor has been removed.
Advantages of this technique are:
- Less trauma to the brain tissues
- Less blood loss
- Lesser risk of infection
- Minimal postoperative pain
- No scarring or cosmetic problems
- Shortened hospital stay – patient may be discharged within 48 hours
The prognosis of a patient depends on the size of the tumor, early diagnosis and may be affected by the patient’s age and general health. Surgery that is minimally invasive for acoustic neuroma remains to be a treatment of choice for operable tumors.
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Johns Hopkins Medicine, “Acoustic Neuroma Treatment” accessed 1/17/11
Skull Base Institute, “Acoustic Neuroma” accessed 1/17/11