OPTIC CHIASMATIC GLIOMA

Optic nerve glioma (also known as optic pathway glioma) is the most common primary neoplasm of the optic nerve. In 66% of NF-1 patients with optic nerve glioma, the growth involves the intraorbital optic nerve. In the absence of NF-1, the optic chiasm is most commonly involved, as is, less often, the intraorbital optic nerve. Optic nerve glioma may involve various portions of the retrobulbar visual pathway, including the optic nerve, chiasm, tracts, and radiations. Malignant lesions can invade the hypothalamus, basal ganglia, and internal capsule directly, or they may spread to the leptomeninges or subpial surfaces. On T1-weighted images, optic nerve gliomas are usually isointense to the cortex and hypointense to white matter. Invariably, the lesions are hypointense to orbital fat. On T2-weighted images, lesions demonstrate a mixed appearance that is isointense to hyperintense relative to white matter and the cortex. Following contrast administration, intense enhancement is common.