An optic pathway glioma is a subset of low grade astrocytoma that grows in a portion of the optic pathway (optic nerve, optic chiasm, optic radiations). Optic gliomas typically grow as an infiltrative lesion with poorly defined borders. Because they are infiltrative they often extend and involve the entire optic pathway. They also frequently extend into adjacent structures, such as the hypothalamus. Optic chiasmatic and hypothalamic gliomas are often considered a single entity because of their ability to infiltrate into both compartments regardless of the site of origin of the tumor. These tumors originate from astrocytes, which are star-shaped brain cells. Astrocytes are a type of glial cell which function to support the surrounding cells. Optic pathway/hypothalamic gliomas account for 4-6% of all brain tumors in children and 30% of all pediatric gliomas. The peak incidence is during the first decade of life.