DescriptionThe neurofibromatoses are genetic disorders of the nervous system that primarily affect the development and growth of neural (nerve) cell tissues. These disorders cause tumours to grow on nerves and produce other abnormalities such as skin changes and bone deformities.
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. Scientists have classified the disorders as neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2). NF1 is the more common type of the neurofibromatoses. In diagnosing NF1, a physician looks for changes in skin appearance, tumours, or bone abnormalities, and/or a parent, sibling, or child with NF1.
SymptomsSymptoms of NF1, particularly those on the skin, are often evident at birth or during infancy and almost always by the time a child is about 10 years old. NF2 is less common. NF2 is characterised by bilateral (occurring on both sides of the body) tumours on the eighth cranial nerve. The tumours cause pressure damage to neighbouring nerves.
To determine whether an individual has NF2, a physician looks for bilateral eighth nerve tumours and similar signs and symptoms in a parent, sibling, or child. Affected individuals may notice hearing loss as early as the teen years. Other early symptoms may include tinnitus (ringing noise in the ear) and poor balance. Headache, facial pain, or facial numbness, caused by pressure from the tumours, may also occur.
CourseIn most cases, symptoms of NF1 are mild, and patients live normal and productive lives. In some cases, however, NF1 can be severely debilitating. In some cases of NF2, the damage to nearby vital structures, such as other cranial nerves and the brainstem, can be life-threatening.
TreatmentTreatments for both NF1 and NF2 are presently aimed at controlling symptoms. Surgery can help some NF1 bone malformations and remove painful or disfiguring tumours; however, there is a chance that the tumours may grow back and in greater numbers.
In the rare instances when tumours become malignant (3 to 5 percent of all cases), treatment may include surgery, radiation, or chemotherapy. For NF2, improved diagnostic technologies, such as MRI, can reveal tumours as small as a few millimetres in diameter, thus allowing early treatment. Surgery to remove tumours completely is one option but may result in hearing loss.
Other options include partial removal of tumours, radiation, and if the tumours are not progressing rapidly, the conservative approach of watchful waiting. Genetic testing is available for families with documented cases of NF1 and NF2. New (spontaneous) mutations cannot be confirmed genetically. Prenatal diagnosis of familial NF1 or NF2 is also possible utilizing amniocentesis or chorionic villus sampling procedures.
(Reviewed by Dr Andrew Rose-Innes, Yale University School of Medicine)