Orbital optic glioma in neurofibromatosis. Magnetic resonance diagnosis of perineural arachnoidal gliomatosis.

In a patient with neurofibromatosis and orbital optic glioma, T2-weighted axial magnetic resonance images showed a fusiform area of high signal intensity with a central linear core of lower signal intensity. Computed tomographic images did not show a corresponding variation in tumor density. Histopathologic examination of the tumor revealed dense, circumferential, perineural glial proliferation. This "arachnoidal gliomatosis" is a feature of orbital optic gliomas in neurofibromatosis and, in our magnetic resonance scans, accurately corresponded with the region of high signal intensity within the tumor.