An optic glioma is usually a special form of pilocytic astrocytoma (WHO grade I). A malignant form of optic glioma is rare[^1].
Epidemiology
Optic gliomas account for about 2% of all gliomas in adults and 7% of all gliomas in children[^1]. In patients who suffer from neurofibromatosis type I, the incidence of an optic glioma is increased by about 25%[^1].
Localization
Optic gliomas can occur in the following patterns and can occur together or as part of a hypothalamic glioma[^1]:
Involvement of the optic nerve
Involvement of the optic chiasm. This form occurs more often in sporadic cases than in cases associated with neurofibromatosis type I.
Multicentric in both optic nerves without involvement of the optic chiasm. This form occurs almost exclusively in patients with neurofibromatosis type I.
Symptoms
Painless proptosis can be an early sign of a unilateral optic glioma. Involvement of the optic chiasm leads to a variable and non-specific occurrence of visual effects without proptosis. Large, extensive optic gliomas can cause dysfunction of the hypothalamus and the pituitary gland as well as a obstructive hydrocephalus due to blockage of the foramen of Monro. Likewise, optic nerve gliosis can be observed on fundoscopy in some cases.
Imaging
On CT or MRI imaging, contrast enhancement is seen in a fusiform arrangement along the optic nerve, which usually extends over more than 1 cm in length. Optic gliomas in patients with neurofibromatosis type I are typically limited to the optic nerve, whereas sporadic optic gliomas often show involvement of the optic chiasm and frequently have cystic components[^1].
