What is Neurofibromatosis?
The neurofibromatoses are genetic disorders of the nervous system that primarily affect the development and growth of neural (nerve) cell tissues. These disorders cause tumors to grow on nerves and produce other abnormalities such as skin changes and bone deformities. The neurofibromatoses occur in both sexes and in all races and ethnic groups. Scientists have classified the disorders as neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2). Other or variant types of the neurofibromatoses may exist, but are not yet identified.
What is NF1?
NF1 is the more common type of the neurofibromatoses, occurring in about 1 in 4,000 individuals in the United States. Although many affected persons inherit the disorder, between 30 and 50 percent of new cases arise spontaneously through mutation (change) in an individual's genes. Once this change has taken place, the mutant gene can be passed on to succeeding generations. Previously, NF1 was known as peripheral neurofibromatosis (or von Recklinghausen's neurofibromatosis) because some of the symptoms--skin spots and tumors--seemed to be limited to the outer nerves, or peripheral nervous system, of the affected person. This name is no longer technically accurate because central nervous system tumors are now known to occur in NF1
What is NF2?
This less common of the neurofibromatoses affects about 1 in 40,000 persons. NF2 is characterized by bilateral (occurring on both sides of the body) tumors on the eighth cranial nerve. It was formerly called bilateral acoustic neurofibromatosis or central neurofibromatosis because the tumors, which cause progressive hearing loss, were thought to grow primarily on the auditory nerve, a branch of the eighth cranial nerve responsible for hearing. Scientists now know that the tumors typically occur on the vestibular nerve, another branch of the eighth cranial nerve near the auditory nerve. The tumors, called vestibular schwannomas for their location and for the type of cells in them, cause pressure damage to neighboring nerves. In some cases, the damage to nearby vital structures, such as other cranial nerves and the brainstem, can be life-threatening.
