| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (KC) Class of 2021, Baylor College of Medicine, Houston, Texas |
| Transcript |
We're gonna be talking today about optic nerve tumors, and by optic nerve tumors, I'm gonna be focusing in on primary optic nerve tumors. And, the optic nerve really doesn't have a lot of stuff in it, so it can make a tumor out of the nerve itself - and that's gonna be a glioma. Or, it can make it tumor from the sheath - and that's gonna be a sheath meningioma. So, the two most common tumors of the optic nerve are optic nerve glioma and optic nerve sheath meningioma, and we can differentiate these based on clinical grounds and also on radiographic grounds. So, the optic nerve glioma is usually a younger patient, in fact, often a child, and what we're worried about is the associated phakomatosis - neurofibromatosis type 1. So, you're gonna be looking for the café-au-lait spots, the axillary freckling, the lisch nodules, and the other cutaneous findings of neurofibromatosis type 1 - the neurofibroma. A child with a optic nerve glioma is gonna present with optic nerve findings. Those are the usual optic nerve findings - loss of acuity, loss of field, relative afferent pupillary defect, a swollen or pale optic nerve, but the nerve might be normal. Because it's orbital optic nerve glioma, we would be worried about proptosis and ophthalmoplegia. So, a painless progressive loss of vision is the stem for optic nerve glioma. We're gonna be looking for the optic neuropathy findings: RAPD and a failed nerve. You're gonna think about NF type 1. And, the imaging of optic nerve glioma is typically a fusiform enlargement of the nerve itself, so it's an intraaxial, intraparenchymal enlargement of the optic nerve. And so, an optic nerve glioma makes a big optic nerve. Obviously if it's intracranial, it'll do the same thing in the chiasm. It'll be a big chiasm, and it can even be in the optic tract. In contrast, the meningioma is not usually a child, although meningioma can occur at any age, it's typically an adult, usually an older age or middle-aged female. It can be associated with multiple meningiomas or the schwannoma of the aether, and that's NF type 2 - neurofibromatosis type 2, even though most patients with sheath meningioma do not have NF type 2. And, just like the optic nerve glioma, similar types of clinical presentation - painless, progressive loss of vision, RAPD, swollen or pale optic nerve. If the nerve compression is slow enough, they might have a shunt vessel, a retinal choroidal venous collateral, that is shunting the blood from the choroid venous side and the retina, out the optic nerve. And, we might have orbital signs: proptosis, ophthalmoplegia, just like with the optic nerve glioma. The optic nerve sheath meningioma has a different radiographic feature. So, it's in the optic nerve sheath, and so, it causes a tram track sign. So, the sheath itself is enhancing and enlarged, but the parenchyma of the nerve itself is usually not, although there's some variability. So, if the enhancement and the enlargement is in the sheath, they're an adult, we're thinking about sheath meningioma. If it's intraaxial, intraparenchymal, fusiform, in a kid, especially with NF type 1, we're thinking about optic nerve glioma. So, the two main primary optic nerve tumors that you need to know about - sheath meningioma and glioma - similar clinical presentation different demographics, different phakomatoses, and different radiographic features. |
