Which of the following is considered the most common intrinsic tumor of the optic nerve?

• A. Optic nerve sheath meningioma
• B. Optic nerve glioma
• C. Orbital cavernous hemangioma
• D. Optic nerve schwannoma

Answer: (B)

Intrinsic tumors arise from cells within the optic nerve itself, meaning the tumor develops inside the nerve substance rather than from its coverings or surrounding orbital tissues. The optic nerve glioma is the most common tumor of that internal origin. It is typically a low-grade astrocytoma that originates from optic nerve glial cells (astrocytes) and is most often seen in children, frequently in association with neurofibromatosis type 1. Because the lesion starts inside the nerve, you see progressive thinning and enlargement of the optic nerve on imaging and along the nerve’s course toward the chiasm, with variable vision loss.

Other options describe tumors not arising from the nerve itself. Optic nerve sheath meningioma comes from the meninges around the nerve, so it’s extrinsic to the nerve substance and tends to occur in adults with a characteristic imaging appearance like a thickened nerve sheath and sometimes a dural tail. Orbital cavernous hemangioma is a vascular tumor of the orbit that can compress the optic nerve from outside, also not intrinsic. Optic nerve schwannoma is very rare because the optic nerve’s central portion is CNS tissue without Schwann cells, so tumors of Schwann cells in this location are uncommon.