| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (AL) Class of 2022, Baylor College of Medicine, Houston, Texas |
| Transcript |
So today we're going to be talking about MOG, which is myelin oligodendrocytic glycoprotein. And the anti-MOG spectrum continues to expand, but I will give you the typical way this presents to us and when you should be thinking about MOG. So anti-MOG, an antibody against myelin oligodendrocytic glycoprotein, is an antibody-mediated disorder and it looks like optic neuritis. And so normally when you have a demyelinating optic neuritis we're thinking about multiple sclerosis as the most common cause. But several features might suggest a patient who has a retrobulbar optic neuropathy or a papillitis might actually be harboring MOG as the cause of their optic neuropathy. So, as you know in the prototype, the typical optic neuritis patient from MS is a young female, for example a 20 year old female, with an acute loss of vision, pain with eye movement, and RAPD, and the fundus is typically normal - the doctor sees nothing, the patient sees nothing, it's a retrobulbar optic neuropathy. So, if we compare and contrast the typical retrobulbar optic neuritis of multiple sclerosis against MOG, you'll see when we should be thinking about the MOG spectrum disorder. So, the first thing is if we don't have a young patient - so as opposed to multiple sclerosis, which is typically between the 20- and 40-year range, if we're outside of the age spectrum. So, in a kid for example, who has optic neuritis from an acute disseminated encephalomyelitis, we should be thinking about MOG in those patients. Or if the patient is an older patient, for example older than 40, we should be thinking about MOG rather than demyelinating optic neuritis. And if the person is not a Caucasian patient, we should be thinking about non-demyelinating, non-optic neuropathies from MS but from MOG and NMO. So Afro-Caribbean and Asian patients, older patients, or kids with ADEM, you should be thinking about MOG. In addition, the patients with the MOG have pain that seems out of proportion to what we normally see with demyelinating optic neuritis. So, in optic neuritis from MS it's pain with eye movement - but if the pain is the predominant component, or if they have severe pain, we really should be thinking about MOG in those patients. And in typical optic neuritis we have an RAPD because it's usually unilateral. But if we have a bilateral case and we don't have the RAPD (because relative to the fellow eye it's not present), that bilaterality of the enhancement, or bilaterality of the presentation, or bilaterality of the afferent problem and no RAPD, also would suggest MOG spectrum disorder. And finally, the fundus is normally normal in the typical demyelinating optic neuritis because it's retrobulbar, but in the patient who has optic disc edema, you should be thinking about MOG in those patients. And so when we do the MRI, we'll be looking for multiple sclerosis - that's periventricular white matter lesions; may or may not enhance; supratentorial, infratentorial, or corpus callosum; Dawson's fingers. But what if the MRI scan is negative? That's another thing that we need to be thinking about MOG, especially if the pattern of enhancement is in the sheath or longitudinally extensive. And by that, we mean when we're doing the MRI (here are the eyeballs), if the optic nerve enhancement is a long segment of enhancement, or if it's bilateral, or if it's involving the chiasm - bilateral, longitudinally extensive, or chiasmal enhancement are all kind of markers of NMO and MOG. And if the sheath is enhancing - so normally the nerve is enhancing in optic neuritis - but if it's the sheath, not the nerve on this coronal view you would see the sheath enhancing, and on an axial view it will be the sheath in like a tram-track sign. So sheath enhancement, or enhancement outside of the nerve parenchyma, bilateral, severe pain, no RAPD because it's bilateral, optic disc edema, or older patient, or a kid, and a non-Caucasian patient - these are the big red flags that you should be thinking about MOG, especially if the MRI is negative for demyelinating white matter lesions. |
