The neurofibromatoses: hereditary predisposition to multiple peripheral nerve tumors.

Neurosurgeons must be aware of the neuro-fibromatoses because they frequently present with nervous system tumors. Such patients develop numerous peripheral nerve sheath tumors; fortunately, only a few of these tumors are symptomatic or malignant. The tumor burden in individual patients can be remarkable, however, producing significant morbidity and requiring extensive or repeated care by a skilled neurosurgeon. Because it is impossible to predict which of the deep neurofibromas will undergo malignant transformation, it behooves clinicians and patients to be aware of any change in symptoms or growth of tumors, because early resection of MPNST offers the only chance for cure. Neurosurgical professionals should be familiar with the diagnostic criteria of the neurofibromatoses, because the patient who presents with an initial neurofibroma or schwannoma immediately falls into a category in which those disorders must be ruled out. In this regard, a family history of nerve sheath tumors is revealing and should prompt referral for a clinical genetics evaluation. Cutaneous manifestations of NFI can confirm the diagnosis at initial presentation. Missing the initial presentation of a patient with NF2 can lead to marked morbidity, such as deafness,because surveillance for subsequent tumors was inadequate. Tumorigenesis in all neurofibromatoses involves loss of tumor suppressor genes. These disorders illustrate that the two-hit loss of tumor suppressor gene model, which applies best for NF2, is oversimplified. As with most cancers,a theory of multistep progressive acquisition of genetic changes that promote unregulated grow this emerging in schwannomatosis. In addition, the hyperpigmentation and learning disability of NF 1 highlight that loss of one copy of the gene is sufficient to cause nontumoral manifestations of the disorder. Genetic counseling and testing have an important role in the diagnosis of NFI and NF2 as well as in the management of all the neurofibromatoses.