Optic glioma is usually a special form of of pilocytic astrocytoma (WHO Grade I). A malignant form of optic glioma is rare[^1].
Epidemiology
Optic gliomas account for approximately 2% of all gliomas in adults and 7% of all gliomas in children[^1]. In patients with Neurofibromatosis type 1, the incidence of optic glioma is increased by approximately 25%[^1].
Localization
Optic gliomas may occur in the following patterns and may occur together or as part of a hypothalamic glioma[^1]:
Involvement of the Optic nerve
Involvement of the Optic chiasm. This form occurs more frequently in sporadic cases than in cases associated with neurofibromatosis type I.
Multicentric involvement of both optic nerves without involvement of the optic chiasm. This form occurs almost exclusively in patients with neurofibromatosis type I.
Symptoms
Painless proptosis may be an early sign of unilateral optic glioma. Involvement of the optic chiasm leads to variable and nonspecific visual disturbances without proptosis. Large, extensive optic gliomas may cause dysfunction of the Hypothalamus and the Pituitary gland, as well as Obstructive hydrocephalus due to obstruction of the Foramen of Monro. Fundoscopy may also reveal gliosis of the optic nerve in some cases.
Imaging
CT or MRI imaging shows contrast enhancement in a fusiform configuration along the optic nerve, usually extending more than 1cm in length. Optic gliomas in patients with neurofibromatosis type I are typically limited to the optic nerve, whereas sporadic optic gliomas frequently involve the optic chiasm and often have cystic components[^1].
