Bilateral optic nerve glioma

Additional clinical history: Patient also has café au lait spots, and his mother has a history of Neurofibromatosis Type 1.


Findings

CT Head: There is enlargement of the bilateral optic nerves and optic chiasm.
MRI Brain: There is fusiform enlargement of the optic nerves bilaterally, with extension to the optic chiasm. The optic nerves demonstrate isointense signal to grey matter on T1 (and, not shown, also on T2 and FLAIR images), with contrast enhancement.

Differential diagnosis:
- Optic nerve sheath meningioma
- Optic neuritis
- Pseudotumor (Idiopathic orbital inflammatory disease)
- Adult malignant optic glioma
- Bilateral optic nerve glioma associated with NF-1


Diagnosis: Presumed bilateral optic nerve glioma in NF-1 patient


Key points

General:
- Most common cause of optic nerve enlargement
- Much more common than optic nerve sheath meningioma (up to 4 times more common)
- 3% of all orbital tumors
- Treatment may include radiation, chemotherapy, or surgery if needed
- Strong association with NF-1
Up to 50% of cases of optic nerve glioma involve patients with NF-1
Conversely, 15% of patients with optic nerve glioma have NF-1
May be bilateral in NF-1

Clinical Presentation
- Patients present with progressive vision loss
- May have proptosis
- Age at presentation is median of 5 years old
- Approximately 80% occur by 10 years of age
- Rarely progress after 6 years old, with cases of spontaneous regression

Pathology
- Grade I astrocytoma of the optic nerve
- Same histologic appearance as juvenile pilocytic astrocytoma


Radiology

Fusiform or sausage like enlargement of the optic nerve
Resulting in kinking of the optic nerve
May extend into proximal optic pathway, including optic chiasm, optic tracts, lateral geniculate body, and optic radiations
Demonstrates variable enhancement
Causes enlargement of optic canal

CT
- Isodense optic nerve enlargement
- Rare to have calcification (different from meningioma)

MR
- T1 iso/hypointense
- T2 variable signal
- Variable enhancement