| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (JK) Class of 2022, Baylor College of Medicine, Houston, Texas |
| Transcript |
Today we're going to talk about ptosis, but not surgery. The diagnostic approach to ptosis. So, ptosis as you know means you have a droopy lid. So, the first thing you need to do is make sure it's not a pseudo-ptosis. So, what could cause the patient to have a pseudo-ptosis (and pseudo means false). If you have lid retraction on the other side, the other lid might look ptotic, so we want to push the lid retraction down to make sure that the patient doesn't have a pseudo-ptosis. Also, there are other things that can cause a pseudo-ptosis including the eye is higher and underneath the layer or hyper-globus or 10 million other things that could make the lid look down even though it's not down. When we're dealing with a ptosis what we'd like to know is: Is it a neurogenic cause? And there are two neurogenic causes of ptosis that we have to worry about in neuro-ophthalmology. Third nerve palsy and that means we have to check the pupil and the motility. And that can cause either a partial or complete ptosis. So, in every patient with ptosis; we need to make sure the motility and the pupil are normal. The second is the Horner syndrome which is the oculo-sympathetic pathway. That usually makes only a 1 to 2 millimeters of ptosis associated with an anisocoria that's greater in the dark because it's a sympathetic dilation problem with a smaller pupil. So, you can see the importance of checking the pupil and any patient less who has lid but also low motility. Once you've made sure it's not the neurogenic causes, then we're going to be looking at neuromuscular junction and the most prominent neuromuscular junction disorder that we see is myasthenia gravis. So, in the history we'd like to know if it's variable and fatigable, we'd like to know if they have any weakness anywhere else, and again the motility examination for diplopia and ophthalmoplegia. As opposed to the neurogenic causes the pupil better be normal in myasthenia gravis as myasthenia does not affect the pupil; at least not clinically. And so, the junction, myasthenia we want to look for Cogan's; twitch sign which is here's the ptotic lid and we have them look down and rest the acetylcholine when they look back up the acetylcholine fires, but it can't hold and then it falls back down; which we call a Cogan's lid twitch sign. We'd look for enhancement of ptosis where we would lift up one lid and the other lid might fall down because we're relieving the innervational effort of Hering's law on the contralateral lid and that way make it more ptotic and we're going to again look for on the exam variability and fatigue; the hallmarks of myasthenia gravis. And finally, we're going to be looking to see if it's myogenic which is the muscle and the muscle that lifts your lid up is called the levator palpebrae superioris. The levator, we need to check the levator function. So the way to measure the levator function is we measure the excursion of the eye from the down position to the up position and we use the ruler to measure how much the levator edge moves so when we're looking down we put the ruler there, when they look up, we put the ruler here. That movement is levator function and patients who have neurogenic or neuromuscular junction related ptosis usually have a decreased levator function versus the more common cause of myogenic ptosis, levator dehiscence, has a normal or near normal levator function. So, of all the parameters that we test levator function is the one that matters most on the neuro-ophthalmology side and we'd like to know if it's preserved. The other signs: high indistinct lid crease, an older patient and a levator to dehiscence etiology like trauma or contact lens helps support the diagnosis of myogenic levator dehiscence. It's not really a dehiscence, it's more like a stretching and degenerative thing, but myogenic ptosis is a super common cause. So insummary when we're dealing with ptosis what really looking for is to make sure it's not "neurop", The way to make sure that the ptosis is not "neurop" is by checking the motility, checking the pupil making sure it's not a third, making sure it's not a Horner's, looking for variability and fatigue, making sure it's not myasthenia gravis, looking for a mechanical cause both for pseudo ptosis and true ptosis, and if all that is not "neurop" then prove that the levator function is intact, they have a high and indistinct lid crease, and that the person has a reason to have levator dehiscence. Once you've done that, then you can operate on that lid but first make sure it's not "neurop". |
