| 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 |
So, we are going to talk a little bit about how seizure comes to neuro-ophthalmology, and it can come in two places; one is the afferent pathway, and the second is it can come to us as the efferent pathway. And, the way it comes to us in the afferent pathway ism if you have seizure as you know in your motor cortexm that produces a tonic-clonic seizure, which is what everybody knows as a classic seizure. However, these other seizures so if the seizure occurs in the occipital lobe you won't get any motor movement until it generalizes. And so, if the seizure occurs in the occipital lobe normally what they have is bilateral and simultaneous transient positive visual phenomena. It's usually described as little tiny colored circles. It fills their field, lasts seconds two minutes at a time, and then it spontaneously resolves. They're often a little bit out of it, either right before during or after, so it's analogous to regular motor seizures in that regard. In the temporal lobe it's a little bit different. The temporal lobe seizure can have a formed hallucination, like a person or animals, and they might have an olfactory or gustatory aura, where they smell something like smoke or taste something. And so, in these temporal lobe seizures and these occipital lobe seizures which are afferent, we want to do a visual field, because what we're looking for in these patients who have positive visual phenomenon or visual hallucination, if they have a field defect, and what we're looking for is on homonymous hemianopsia, that's going to be an indication that there's a structural lesion under there causing the seizure, and so we really want to have a MRI scan of the brain in that patient. So, any a patient who has an unusual positive visual phenomenon, you should do a homonymous hemianopsia test, a whole formal visual field, because if you don't, their acuity otherwise is 20/20, their pupil exams going to be normal, external pressure, slit lamp, motility, and the fundus are all going to be normal. The whole case is doing this [HVF]. So on the afferent side, you also should be aware that if you have a seizure, you can have the equivalent of a Todd's paralysis, so when you have a motor seizure you might be hemiparetic afterwards because you have the Todd's paralysis - the after effect of the seizure, and the same thing can happen in patients who have seizure in the occipital lobe. They might have a homonymous hemianopsia as a Todd's paralysis equivalent of having seizure activity in their occipital or their temporal lobe, so we want to do the field in these patients to see if there's this Todd's paralysis equivalent. And in those patients their MRI scan might be normal, so on the differential diagnosis of a homonymous hemianopsia with a negative MRI, you should be thinking about seizure affecting the afferent pathway. Efferent pathway also can be affected, so patients can have eye movement problems, they can have fluttering of their lids, the eyes might roll up or go to the side, and if you have a seizure it acts like an irritative focus, so in the frontal lobe, as you know the saccade is controlled by the contralateral frontal lobe, so if you have a destructive lesion in the right frontal lobe, that won't be able to send the signal to look to the contralateral side, so right frontal can't look to the left. But, if you have an irritative lesion like a seizure, it'll drive the eyes to the contralateral side, so you have a gaze preference. So, both lid fluttering, eye fluttering, gaze preference, and gaze palsy on a supranuclear basis can be the efferent manifestation of seizure disorder. So, we are thinking about seizure both on the afferent side - positive visual phenomenon, visual hallucinations - check for a homonymous hemianopsia, and on the efferent side - lid fluttering, eye movement, gaze preference, gaze palsy - supranuclear. |
