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Las Neurofibromatosis
The neurofibromatoses are a group of three genetically distinct but related disorders of the nervous system that cause tumors to grow around the nerves. Tumors begin in the cells that make up the myelin sheath, a thin membrane that envelops and protects nerve fibers, and often spread into adjacent areas. The type of tumor that develops depends on its location in the body and the kind of cells involved. The most common tumors are neurofibromas, which develop in the tissue surrounding peripheral nerves. Most tumors are non-cancerous, although occasionally they become cancerous over time.
Why these tumors occur still isn’t completely known, but it appears to be mainly related to mutations in genes that play key roles in suppressing tumor growth in the nervous system. These mutations keep the genes – identified as NF1 and NF2 – from making specific proteins that control cell production. Without these proteins, cells multiply out of control and form tumors.
An estimated 100,000 Americans have a neurofibromatosis (the singular form of neurofibromatoses) disorder, which occurs in both sexes and in all races and ethnic groups. Scientists have classified the disorders as neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and a type that was once considered to be a variation of NF2 but is now called schwannomatosis.
NF1 is the most common neurofibromatosis, occurring in 1 in 3,000 to 4,000 individuals in the
To diagnose NF1, a doctor looks for two or more of the following:
Many children with NF1 have larger than normal head circumference and are shorter than average. Hydrocephalus, the abnormal buildup of fluid in the brain, is a possible complication of the disorder. Headache and epilepsy are also more likely in individuals with NF1 than in the normal population. Cardiovascular complications are associated with NF1, including congenital heart defects, high blood pressure (hypertension), and constricted, blocked, or damaged blood vessels (vasculopathy). Children with NF1 may have poor linguistic and visual-spatial skills, and perform less well on academic achievement tests, including those that measure reading, spelling, and math skills. Learning disabilities, such as attention deficit hyperactivity disorder (ADHD), are common in children with NF1.
Symptoms, particularly the most common skin abnormalities -- café-au-lait spots, neurofibromas, Lisch nodules, and freckling in the armpit and groin -- are often evident at birth or shortly afterwards, and almost always by the time a child is 10 years old. Because many features of these disorders are age dependent, a definitive diagnosis may take several years.
Since doctors don’t know how to prevent or stop neurofibromas from growing, surgery is often recommended to remove them. Several surgical options exist, but there is no general agreement among doctors about when surgery should be performed or which surgical option is best. Individuals considering surgery should carefully weigh the risks and benefits of all their options to determine which surgical treatment is right for them. There are also surgical and chemical techniques that can reduce the size of eye tumors (optic gliomas) when vision is threatened. In addition, some bone malformations, such as scoliosis, can be surgically corrected. In the rare instances when tumors become malignant (3 to 5 percent of all cases), treatment may include surgery, radiation, or chemotherapy.
Treatments for other conditions associated with NF1 are aimed at controlling or relieving symptoms. Headache and epileptic seizures are treated with medications. Since there is a higher than average risk for learning disabilities, children with NF1 should undergo a detailed neurological exam before they enter school. Once these children enter school, if teachers or parents suspect there is evidence of a learning disability (or disabilities), they should request an evaluation that includes an IQ test and the standard range of tests to evaluate verbal and spatial skills. Children with learning disabilities are eligible for special education services under the provisions of the Individuals with Disabilities Education Act (IDEA).
This rare disorder affects about 1 in 40,000 people. NF2 is characterized by slow-growing tumors on the eighth cranial nerve. This nerve has two branches: the acoustic branch helps people hear by transmitting sound sensations to the brain; the vestibular branch helps people maintain their balance. The tumors of NF2, called vestibular schwannomas because of their location and the types of cells that compose them (Schwann cells, which form the myelin sheath around nerves), press against and sometimes even damage the nerves they surround. In some cases they will also damage nearby vital structures such as other cranial nerves and the brainstem, leading to a potentially life-threatening situation.
Individuals with NF2 are at risk for developing other types of nervous system tumors such as spinal schwannomas, which grow within the spinal cord and between the vertebrae, and meningiomas, which are tumors that grow along the membranes covering the brain and spinal cord.
To diagnose NF2, a doctor looks for the following:
or any two of the following:
Because NF2 is so rare, few studies have been done to look at the natural progression of the disorder. The course of NF2 varies greatly among individuals, although inherited NF2 appears to run a similar course among affected family members. Generally, vestibular schwannomas grow slowly, and balance and hearing deteriorate over a period of years. A recent study suggests that an earlier age of onset is associated with faster tumor growth and a greater mortality risk.
The distinguishing feature of schwannomatosis is the development of multiple schwannomas everywhere in the body except on the vestibular nerve. The dominant symptom is excruciatingly intense pain, which develops when a schwannoma enlarges, compresses nerves, or presses on adjacent tissue. Some people experience additional neurological symptoms, such as numbness, tingling, or weakness in the fingers and toes. Patients with schwannomatosis never have neurofibromas.
About one-third of those with schwannomatosis have tumors limited to a single part of the body, such as an arm, a leg, or a segment of the spine. Some people develop many schwannomas; others develop only a few.
Anyone with schwannomatosis experiences some degree of pain, but the intensity varies. A small number of people have such mild pain that they are never diagnosed with the disorder. Most people have significant pain, which can be managed with medications or surgery. In some extreme cases, pain will be so severe and disabling it will keep people from working or leaving the house.
Clinical genetic testing can confirm the presence of a mutation in the NF1 gene with an accuracy of 95 percent. Some families and doctors may choose to use a genetic test to confirm an uncertain diagnosis when there is no family history of the disorder and when waiting for additional symptoms to appear would put an unnecessary emotional burden on the family. Prenatal testing for the NF1 mutation is also possible using amniocentesis or chorionic villus sampling procedures. Genetic testing for the NF2 mutation is sometimes available but is accurate in only 65 percent of those tested. Genetic counselors can provide information about these procedures and help families cope with the results.
The National Institute of Neurological Disorders and Stroke (NINDS), one of the National Institutes of Health (NIH), is the leader in federal funding of research studying neurological diseases. The Institute sponsors basic studies aimed at understanding normal and abnormal development of the brain and nervous system, as well as clinical trials to improve the diagnosis and treatment of neurological disorders. In conjunction with the NIH's National Cancer Institute (NCI), the NINDS supports research focused on finding better ways to prevent, treat, and ultimately cure the neurofibromatosis disorders.
In the mid-1990s, research teams supported by the NINDS located the exact position of the NF1 gene on chromosome 17. The gene has been cloned and its structure continues to be analyzed. The NF1 gene makes a large and complex protein called neurofibromin, which is primarily active in nervous system cells as a regulator of cell division, functioning as a kind of molecular brake to keep cells from over-multiplying. In addition to work on NF1, intensive efforts have led to the identification of the NF2 gene on chromosome 22. As in NF1, the NF2 gene product is a tumor-suppressor protein (termed merlin or schwannomin).
Ongoing NINDS-sponsored research continues to discover additional genes that appear to play a role in tumor suppression or growth. Continuing research on these genes and their proteins is beginning to reveal how this novel family of growth regulators controls how and where tumors form and grow. Understanding the molecular pathways and mechanisms that govern these key proteins and their activities will offer scientists exciting opportunities to design drugs that could replace the missing proteins in people who have the neurofibromatoses and return their cell production to normal.
The NINDS currently supports basic and clinical research to understand how the genetic mutations that cause the benign tumors of NF1 can also cause abnormal development of neurons and neural networks during fetal development. This abnormal development can lead to the learning disabilities and cognitive deficits of children with the disorder.
The NINDS also encourages research aimed at developing improved methods of diagnosing the neurofibromatoses and at identifying factors that contribute to the wide variations of symptoms and severity of the disorders.
Just as important, the NINDS is supporting ongoing research with a large group of children with NF1 to help doctors answer the question that most parents ask when their child is diagnosed with the disorder: “What can we expect when our child goes to school?” Using MRI, which shows brain structure, functional MRI, which shows areas of the brain at work, and neuropsychological tests that measure specific cognitive skills, researchers are looking for associations between brain abnormalities and specific cognitive disabilities. Finding these links would give doctors an indication of the kinds of learning disabilities parents and their children could anticipate in the future and help them develop early intervention programs.
The NINDS contributes to the support of the Human Brain and
Human Brain and Spinal Fluid Resource Center
Neurology Research (127A)
W. Los Angeles Healthcare Center
11301 Wilshire Blvd., Bldg. 212
Los Angeles, CA 90073
310-268-3536
24-hour pager: 310-636-5199
Email: RMNbbank@ucla.edu
http://www.loni.ucla.edu/~nnrsb/NNRSB
For more information on neurological disorders or research programs funded by the National Institute of Neurological Disorders and Stroke, contact the Institute's Brain Resources and Information Network (BRAIN) at:
BRAIN
P.O. Box 5801
Bethesda, MD 20824
(800) 352-9424
http://www.ninds.nih.gov
Information also is available from the following organizations:
Children's Tumor Foundation 95 Pine Street 16th Floor New York, NY 10005 info@ctf.org http://www.ctf.org Tel: 800-323-7938 212-344-6633 Fax: 212-747-0004 |
National Cancer Institute (NCI) National Institutes of Health, DHHS 6116 Executive Boulevard, Ste. 3036A, MSC 8322 Bethesda, MD 20892-8322 cancergovstaff@mail.nih.gov http://cancer.gov Tel: 800-4-CANCER (422-6237) 800-332-8615 (TTY) |
Neurofibromatosis, Inc. (NF Inc.) P.O. Box 66884 Chicago, IL 60666 nfinfo@nfinc.org http://www.nfinc.org Tel: 630-627-1115 800-942-6825 |
Acoustic Neuroma Association 600 Peachtree Parkway Suite 108 Cumming, GA 30041 info@anausa.org http://www.anausa.org Tel: 770-205-8211 877-200-8211 Fax: 770-205-0239/877-202-0239 |
International RadioSurgery Association 3002 N. Second Street Harrisburg, PA 17110 office1@irsa.org http://www.irsa.org Tel: 717-260-9808 Fax: 717-260-9809 |
NIH Publication No. 06-2126
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Prepared by:
Office of Communications and Public Liaison
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892
NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.
All NINDS-prepared information is in the public domain and may be freely copied. Credit to the NINDS or the NIH is appreciated.
Last updated March 04, 2009