| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (AB) Class of 2024, Baylor College of Medicine, Houston, Texas |
| Transcript |
What I want to talk today about is the carotid artery. And in neuro-ophthalmology, there's some things we need to know about the carotid. So obviously, the internal carotid artery is the main artery that we are dealing with in ophthalmology. The first intracranial branch is the ophthalmic and then that artery becomes the central retinal artery. And so, when you have carotid occlusive disease in the neck, emboli can fly off, go down the ophthalmic, and produce an ophthalmic artery occlusion or a central retinal artery occlusion or a branch retinal artery occlusion. So, that means we have to deal with both acute vision loss that is transient, and the transient version is called amaurosis fugax, which means fleeting blindness. Transient monocular vision loss is often ipsilateral carotid artery in the acute setting. And, you can get a tear in this artery, which is a dissection, and that dissection can affect the sympathetic pathway fibers, which are on the outside of the artery and can produce a smaller pupil and a little bit of ptosis, which we call the Horner's syndrome. So, both acute transient vision loss (amaurosis fugax) can be associated with the Horner's syndrome, or the acute and permanent vision loss (a central retinal artery occlusion or a branch retinal occlusion) can be associated with a Horner's syndrome from carotid disease, either occlusive disease inside the artery or a dissection on the outside. And, of course, vasculitis can also cause the same constellation of findings where the problem is on the outside of the artery. And, the most common vasculitis that we see in elderly patients is giant cell arteritis. So, those patients can present with central retinal artery occlusions or ischemic disease from the ophthalmic causing posterior or anterior ischemic optic neuropathy, or could produce amaurosis fugax, or if it's the ophthalmic again, it can produce efferent symptoms like diplopia and ophthalmoplegia. And then rarely, even a Horner's syndrome. So, you should be thinking about vasculitis and the external carotid distribution as well when we're dealing with transient monocular vision loss, Horner's syndrome, or emboli inside the eye. There are also unusual things that you have to think about with carotid disease where emboli are flying up into the head. And, the terminus artery for the internal carotid artery, of course, is the middle cerebral artery, and the anterior circulation with the anterior cerebral artery. So, sometimes we see patients who have homonymous hemianopsias on the contralateral side to the carotid disease. And one of the very unusual things that you might encounter is if we have occlusive disease. So, if we have occlusive disease on one side, normally that means there's going to be no flow. However, a carotid could be occluded and a collateral is supplying the ipsilateral hemisphere now. That collateral could be from the external carotid artery instead of the internal carotid artery. And so, anybody who has100% occlusion in the carotid, we want to make sure that that external carotid is not actually supplying that hemisphere. And, the thing that's dangerous for ophthalmologists is the superficial temporal artery is from that external carotid, and if it is going retrograde and supplying that hemisphere, we would not want to do a temporal artery biopsy on this person. So, you can see how you can get in big trouble here. They're elderly, they presented with amaurosis fugax, you're worried about giant cell, the carotid is occluded in the neck. We probably should not betaking the superficial temporal artery on this side until we're sure that that's not the collateral vessel that is supplying the ipsilateral hemisphere. And then the last thing that can occur, which is even more rare but you need to know about it is, if you have 100% occlusive disease, we're not going to be able to do surgery on that, but if it's 99% or 70 to 99 even, they might do a carotid endarterectomy. When that artery is opened up, especially if the hemisphere is already hypoperfused chronically, that can cause too much blood flow to go to that hemisphere and that is a cerebral hyperperfusion event. And so, if you hyperperfuse a chronically hypoperfused hemisphere, you'll get a hemorrhage. And so, that hemorrhage can be either ipsilateral to the carotid endarterectomy, producing a homonymous hemianopsia, or because of the circle of Willis and the dysregulation of the carotid system from chronic hypoperfusion as well as damage to the baroreceptor for pressure sensing on that carotid, you can get a cerebral hyperperfusion syndrome and hemorrhage on both the ipsilateral side and the contralateral side. So, you need to know a little bit about carotid artery disease in neuro-ophthalmology. |
