Visual loss in children with neurofibromatosis type 1 and optic pathway gliomas: Relation to tumor location by magnetic resonance imaging

PURPOSE: To examine the potential for visual acuity loss, and its relation to extent and location of optic pathway gliomas in a cohort of children wit h neurofibromatosis type I studied with magnetic resonance imaging. METHODS: We reviewed the neuro-ophthalmologic records and brain/orbital mag netic resonance imaging scans for 43 consecutive pediatric patients with ne urofibromatosis type I and optic pathway gliomas who were followed at the C hildren's Hospital of Philadelphia. The presence of visual loss, defined as abnormal visual acuity for age in one or both eyes, was determined. Optic pathway gliomas were classified by tumor extent and location according to i nvolvement of the optic nerves, chiasm, and postchiasmal structures by magn etic resonance imaging. RESULTS: involvement of the optic tracts and other postchiasmal structures at tumor diagnosis was associated with a significantly higher probability o f visual acuity loss (P = .048, chi-square test). Visual loss was noted in 20 of 43 patients (47%) at a median age of 4 years; however, three patients developed visual acuity loss for the first time during adolescence. CONCLUSIONS: In pediatric patients with neurofibromatosis type 1 and optic pathway gliomas, the likelihood of visual loss is dependent on the extent a nd location of the tumor by magnetic resonance imaging and is particularly associated with involvement of postchiasmal structures. Furthermore, older age during childhood (adolescence) does not preclude the occurrence of visu al loss. Close follow-up beyond the early childhood years, particularly for those with postchiasmal tumor, is recommended. (Am J Ophthalmol 2001;131:4 42-445. (C) 2001 by Elsevier Science inc. All rights reserved).