12.5 Optic Nerve Tumors

12.5.1 Optic Nerve Glioma

Optic nerve glioma is the most common cause of optic nerve enlargement, and patients present with proptosis and decreased vision. Optic nerve glioma is a juvenile pilocytic astrocytoma in children [28]. The average age at presentation is 7 years, with 90% of patients presenting prior to age 20 [29]. The childhood form grows slowly with no tendency for malignant transformation and may even undergo spontaneous regression with improved vision [30]. The malignant form may extend to the hypothalamus and third ventricle.

Optic gliomas are well circumscribed with fusiform enlargement [31]. On CT, an optic glioma is isodense to the optic nerve and demonstrates mild to moderate enhancement. There may be associated enlargement of the bony optic canal. Calcification may be seen following radiation therapy. On MRI, the lesion is hypointense to isointense to muscle on T1 images, hyperintense on T2 images, and demonstrates variable enhancement with widening and kinking of the optic nerve (Fig. 12.10) [31].

Fig. 12.10 Optic nerve glioma, right optic nerve. (a) Axial T2 image demonstrates a hyperintense lesion involving the right optic nerve (arrow). (b) Coronal T1 postcontrast image shows homogeneous enhancement of the optic glioma (arrow). Note the normal appearance of the left optic nerve (small arrow)

12.5.2 Optic Nerve Sheath Meningiomas

Meningiomas arise from arachnoid rests in the dural sheath of optic nerves. Patients may present with proptosis and signs of optic neuropathy [32]. These generally occur in middle-aged and elderly women, are slightly more aggressive in children,