Neurofibromatosis Type 2
Neurofibromatosis Type 2
Description, Causes and Risk Factors:
Alternative Names: Bilateral acoustic neurofibromatosis, Vestibular Schwannoma neurofibromatosis.
Neurofibromatosis (NF) is a genetic disorder of the nervous system that causes tumors to form on the nerves anywhere in the body at any time. This progressive disorder affects all races, all ethnic groups and both sexes equally. NF is one of the most common genetic disorders in the United States (one in every 3,000 to 4,000 births).
Types may include: NF-1 and NF-2.
NF-2 is less common than NF-1. It affects about 1 in 40,000 people. It is primarily characterized by benign tumors of the nerves that transmit sound impulses from the inner ears to the brain. Associated symptoms and findings may become evident during childhood, adolescence, or early adulthood. Depending on the exact location and size of the acoustic neuromas/vestibular schwannomas, such findings may include disturbances of balance and walking (gait); dizziness; headache; facial weakness, numbness, or pain; ringing in the ears (tinnitus); and/or progressive hearing loss.
In some individuals with NF-2, additional abnormalities may also be present. These may include loss of transparency of the lenses of the eyes, progressive visual impairment, or an increased risk of developing certain tumors of the brain and spinal cord.
The cells of the body contain information, in the form of genes, for the body to make all the necessary structural components and chemicals to ensure normal function. If a gene is changed (undergo mutation) so that it does not work properly, the gene is described as being faulty. The information contained in the faulty gene, and its product, is impaired. NF-2 results from mutations (change) of a gene on the long arm (q) of chromosome 22. The NF-2 gene regulates the production of a protein that functions as a tumor suppressor. In some individuals with NF-2, the disorder is caused by new (sporadic) mutations of the gene that occur for unknown reasons. In other affected individuals, NF-2 is inherited as an autosomal dominant trait.
Symptoms of NF-2 may include:
Cataracts at a young age.
Changes in vision.
Coffee-colored marks on the skin.
Ringing and noises in the ears.
To diagnose NF2, a doctor looks for schwannomas(A benign, encapsulated neoplasm in which the fundamental component is structurally identical to a syncytium of Schwann cells; the neoplastic cells proliferate within the endoneurium, and the perineurium forms the capsule. The neoplasm may originate from a peripheral or sympathetic nerve, or from various cranial nerves, particularly the eighth nerve; when the nerve is small, it is usually found in the capsule of the neoplasm; if the nerve is large, the neurilemoma may develop within the sheath of the nerve, the fibers of which may then spread over the surface of the capsule as the neoplasm enlarges. Microscopically, neurilemoma is composed of combinations of two patterns, Antoni types A and B, either of which may be predominant in various examples of neurilemomas) along both sides of the eighth cranial nerve, or a family history of NF-2 and one schwannoma on the eighth cranial nerve before age 30. If there is no schwannoma on the eighth cranial nerve, tumors in other parts of the body and/or cataracts in the eyes in childhood could help confirm the diagnosis.
Tests May Include:
Presently, the only treatments available for the tumors of NF-2 are surgery and radiation therapy. Most persons with NF2 require at least one operation during their lifetime. Since the tumors of NF-2 lie on nerves and/or near the brain and spinal cord, their surgical removal is not without risk. For these reasons the potential benefits and risks of every contemplated surgical procedure should be carefully considered and discussed with a health care provider familiar with the disease.
In NF-2, if surgery done to remove a vestibular schwannoma causes hearing loss, an auditory brainstem implant may be used to improve hearing.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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