The frequency of symptomatic nonoptic pathway brain tumors in adolescents and adults known to have neurofibromatosis type 1 (NF1) was determined from the National Neurofibromatosis Foundation International Database (NNFFID) in a study at Washington University School of Medicine, St Louis, MO. These tumors were reported in 17 (0.8%) of 2108 patients with NF1 over 10 years of age. The prevalence of brain tumors in patients with NF1 up to 50 years of age is more than 100 times greater than expected, and is significantly elevated at all ages. Of 17 patients with NF1 with adequate clinical information (10 from the NNFFID study and 7 from a National Cancer Institute (NCI) newly diagnosed adult glioma study), brain tumors were diagnosed in 4 cases between 10 and 20 years of age, 7 between 21 and 40 years of age, and in 6 at 41 years or older. Tumors were located in brainstem, cerebellum, cortical and subcortical regions. Three were pilocytic astrocytomas, 6 were grade II, 4 were grade III, and 2 were grade IV (glioblastoma multiforme) neoplasms (grades III and IV in patients older than 20). None had received chemotherapy or radiation previously. Headache was the most frequent presenting symptom (in 15), and paralysis or seizures in 3 patients each. 
COMMENT. Patients with NF1 are at increased risk for the development of astrocytomas beyond 10 years of age and in adult life. In older patients these tumors may be malignant grades III and IV gliomas, not always the more characteristic pilocytic astrocytoma. Population-based epidemiologic studies are recommended, but brain imaging and careful clinical follow-up should be performed in patients with NF1 of any age who present with persistent headache or neurologic abnormalities.