GANGLIOGLIOMAS INVOLVING THE OPTIC CHIASM

We report three patients with gangliogliomas involving the optic chias m via distinct mechanisms. The ganglioglioma in one patient likely ori ginated in the temporal lobe and spread medially to involve the chiasm , and diffuse spinal cord dissemination also occurred. Chiasmal involv ement in this manner and dissemination at presentation are unusual for gangliogliomas. The tumor in a second patient was intrinsic to the hy pothalmus and chiasm, while in the third patient, it involved both opt ic tracts, and a cyst compressed the chiasm laterally. Two patients de veloped severe bilateral visual loss, while the other had a stable bit emporal hemianopsia. Two patients received radiotherapy, but one conti nued to lose vision. Although gangliogliomas rarely involve chiasm, th e mechanisms by which they produce chiasmal visual loss may be diverse , and the long-term visual prognosis is variable.