The optic chiasm is located in the forebrain directly in front of the hypothalamus. Crucial to sight, left and right optic nerves intersect at the chiasm. One-half of each nerve's axons enter the opposite tract at this location, making it a partial decussation. While rare, optic gliomas -- tumors -- can grow within the chiasm or in conjunction with hypothalamic tumors. Gliomas can directly affect the optic nerves. Noncancerous and typically emergent before age 20, symptoms of optic glioma can include: Bulging eyes or vision loss Loss of appetite and fat reduction as part of diencephalic syndrome Squinting or involuntary eye movement Intracranial pressure Following a preliminary diagnosis, a cerebral angiography or biopsy may be performed. A head CT scan may be conducted to confirm the location and mass of the glioma. Visual field tests can help determine if the tumor has spread deeper into the brain. Treatment options include chemotherapy, cortisteroids, or radiation. In some cases surgery may be required to remove the glioma from the optic chiasm.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Optic chiasma