| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (AS) Class of 2022, Baylor College of Medicine, Houston, Texas |
| Transcript |
Today, we're gonna be talking about proptosis but proptosis in neuro-ophthalmology. Obviously, in orbit and oculoplastics, the list and the emphasis is going to be totally different. But in neuro-ophthalmology, proptosis is a very important and distinctive sign. And the reason it's distinctive is it tells us whatever the problem is in the orbit. And so the first thing that we would like to know is not so much what is the lesion but where is the lesion. And once we have proptosis, that localizes the problem to the orbit. It doesn't have to just be in the orbit but the presence of the proptosis tells us that we're in the orbit. And what that means for you clinically is you must do a Hertel or some other exophthalmometry reading in every patient that we see whether the complaint is afferent (I've lost my vision) or efferent (I have diplopia). Even if it looks like optic neuritis (an acute unilateral loss of vision), RAPD normal fundus, it sounds like optic neuritis - once you add the proptosis into that stem, it moves the differential from demyelinating disease (an optic neuritis from MS) away from the cause. Because why would MS or optic neuritis cause proptosis? It wouldn't. And what that really means is, as soon as you add the proptosis into the stem, it's a mass lesion in the orbit. And so doing a Hertel is a super underutilized and underappreciated thing. In my experience, the resident only wants to do the Hertel on the person who looks proptotic, but that's actually the person we don't need the Hertel on. The reason we have this instrument is to detect proptosis that you can't see, so we should be doing the Hertel on every diplopia patient and every patient who has unexplained vision loss in one eye or both eyes because we're trying to find the distinctive sign of proptosis. If the eye is already proptotic, we're still going to do that Hertel on that person but that's just a measure for follow-up. We already know that the person has proptosis so we should be doing the Hertel on the person we don't know has proptosis. That's the whole point of having the Hertel. And so the most common thing that we encounter in Neuro-Op causing proptosis is thyroid eye disease. It is, by far, the most common cause in adults of unilateral or bilateral proptosis. And so if a patient has diplopia, we know that the where is important and that diplopia could be supranuclear, nuclear, infranuclear. And if it's infranuclear, it can be the nerve, the muscle, or the junction. Once you add the proptosis, that puts the lesion in the orbit and myasthenia gravis is, all of a sudden, not tenable. And so we should be thinking about thyroid eye disease in every patient with diplopia because it can always be thyroid eye disease and we'd like to do that with the Hertel exophthalmometer. If you measure proptosis, the other thing that's super important is when we do the imaging study (usually MRI), we're not just gonna be doing the head. Because once you have the proptosis, we have to image the head and the orbit. And if we're going to image the orbit with gadolinium, we're gonna want to have fat suppression. So adding the proptosis onto the stem makes you order the orbit on the back end and the gadolinium and fat saturation to look for the lesion in the orbit. And so in Neuro-Op, the presence of proptosis is a super important sign. We should look for it with the Hertel on patients who have both afferent and efferent disease. You should be thinking about thyroid eye disease as the most common cause. There are other things that it could be: neoplasms, in the acute setting retrobulbar hemorrhage, inflammatory disease, orbital inflammatory pseudotumor. But the imaging study is going to be telling you what it is. But before we can say what it is, we have to know where it is. And so, for me, recognizing that the patient is proptotic, measuring that they are proptotic, and imaging the proptosis is way more important than actually knowing what is the cause of the proptosis. Because if you just do the head MRI and you don't know they're proptotic, the head imaging might be normal. |
