Optic nerve glioma appears as diffuse enlargement of the left optic nerve (arrows) in an 8-year-old girl.
Optic nerve glioma is the most common cause of optic nerve enlargement. Typically causes uniform thickening of the nerve with mild undulation or lobulation. In children (especially preadolescent girls), optic nerve gliomas are usually hamartomas that spontaneously stop enlarging and require no treatment. In older patients, however, these gliomas may have a progressive malignant course despite surgical or radiation therapy. Optic nerve gliomas are a common manifestation of neurofibromatosis (typically low-grade lesions that act more like hyperplasia than neoplasms).
Optic nerve glioma. (A) Sagittal and (B) coronal T1-weighted MR scans show involvement of the chiasm and left optic nerve.