Neurofibromatosis 1 (NF1) is a common autosomal dominant disorder in which affected individuals develop benign and malignant tumors [ ll. Because of the association between NF 1 and tumor development, the NFI gene has been classified as a tumor suppressor gene [2]. The NFI gene was identified in 1990 and found to code for a large cytoplasmic protein of 2,818 acids [3-51. The NFI gene product, neurofibromin, contains a small region in the central part of the protein that bears sequence similarity with a family of proteins that regulate the protooncogene p21-ras [6][7][8][9]. These p2 1 -ras regulatory proteins are collectively termed guanosine triphosphatase (GTPase)-activating proteins (GAPS). Since p21-ras can transform cells, neurofibromin (as an inhibitor of p21-ras activation) would therefore suppress the growth of cells. This association between NFl GAP function and p21-ras regulation has been demonstrated for some tumors in patients with NF1 [lo-121. One of the most common tumors in patients with NF1 is the optic pathway glioma. Although optic pathway tumors account for only 2 to 5% of all brain tumors in childhood, as many as 70% are associated with NF1. While these tumors generally behave in a benign fashion, optic pathway gliomas can lead to visual loss or extend to nearby brain regions and result in other signs and symptoms. In October 1995, a steering committee was designated by the National Neurofibromatosis Foundation and the Cold Spring Harbor Laboratory to address common clinical problems in NF1. Its goals were to create task forces composed of both basic science and clinical researchers who had worked extensively in various areas of research in NF1. These task forces were to review and critique the known information on these specific targeted areas, to provide rational guidelines for the care of NFl patients, and to establish the basis for future clinical trials. This consensus statement, the result of work performed by the Optic Glioma Task Force, outlines recommendations for the screening, follow-up, and treatment of optic pathway gliomas in children with NF 1. TerminologyOptic glioma has been used widely as a diagnostic term for low-grade astrocytic gliomas arising in the optic nerves. More recently, in recognition of the involvement of other regions of the optic system, the terms optic pathway glioma and visual pathway glioma have gained acceptance. Nonetheless, these terms are imprecise because the term glioma encompasses a wide variety of biologically and clinically distinct lesions. The vast majority of optic pathway gliomas, including the tumors that arise in NF1 patients, are pilocytic astrocytomas. Indeed, the World Health Organization (WHO) classification of central nervous system tumors and the major brain tumor reference texts do not recognize optic pathway glioma as a separate pathological entity, but include these lesions under the rubric of pilocytic astrocytoma [ 13-1 61. Although not well entrenched in the literature, the most accurate term for these tumors is pilocytic artrocy...

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