 Okay, well we've got like a ton of material to go over so we'll go ahead and get started. So this is our annual PGY3 class lecture we're going to be talking about double vision and hopefully everybody has a piece of paper that they can have handy for drawing out one of the cranial nerve pathways. I think we're going to not have time for all of them but we would like to do at least cranial nerve three so. All right so this is our first case and this is a 49 year old man who came in complaining of double vision and his left upper eyelid was droopy. He does have a history of multiple myeloma and he had one to two months of progressively increasing and ptosis of the left upper lid. His double vision was binocular diagonal and pretty constant and really seemed to change much throughout the day and his other complaints in terms of review of systems he also had some coordination difficulty with his right arm and his past ocular history was notable for ocular hypertension, fuchs, and he's pseudophagic. He's also got as I mentioned besides the multiple myeloma he's got a history of asthma and allergies and his current medications he's on infection prophylaxis what with being still on chemotherapy and then he's also taking some prednisone five milligrams twice a day for maintenance in his remission of his multiple on exam vision was pretty good 2020 and 2025 pressure was normal but he had some pupil abnormalities so his right pupil was smaller than the left pupil and he had a four millimeter sorry a one and a half millimeter anisocorrhea between the two eyes that was equal in dark and light. I'm sorry let's go back here. His visual fields were full his motility exams showed an exotropia and a right hypertropia and primary gaze and that was in the left eye and his right eye had full movements and his left eye was severely restricted in adduction superduction and infraduction but with normal abduction. His anterior segment exam was unremarkable except for the ptosis and his neuro exam was notable for the weakness on the right upper extremity which was pretty subtle he had a negative babinski and otherwise normal exam so anybody want to describe his motility exam if not that's okay we can move on Rachel it looks like full abduction right yeah okay very good oh and by the way this case is a case that I borrowed from Iowa grant rounds I did not see any interesting cases that looked like this so we've got a progressive left cranial nerve three policy with a contralateral hemiplegia so anybody have any thoughts about where this might localize okay it's the midbrain so this patient actually underwent MRI after this visit and they found a nice little ring enhancing lesion that I feel like even our colleagues in pathology and any other specialty would be able to identify that nice ring enhancing lesion there. So let's talk about cranial nerve three so the nucleus of cranial nerve three is at the level of the superior colliculus in the midbrain and it's found dorsally and that's important to keep in mind we were just talking yesterday about common questions that come up on OCAPS and one of the you know distinctions that you have to make not only is how the nucleus is organized but where it's located and where the pathways go so that's why we thought it might be a good exercise and we'll get to it later about you know drawing out the pathways it's broken up into four sorry four nuclei for the extraocular muscles so those are the dorsal nuclei and then there's also a nucleus for the levator palpebrae which is which is this little orange guy right here and that's actually a little more interior and then they're also bilateral paired sub nuclei which are the most dorsal of the nucleus complex and that's the edinger westfall nucleus and that's involved in pupillary constriction and as we know the pathway so we have cranial nerve three exiting the midbrain anteriorly crossing near the junction of the ICA and the posterior communicating artery which is important when we think about aneurysms in that area which can commonly cause compression and can cause a cranial nerve three palsy and then the nerve enters the cavernous sinus and travels laterally to enter the orbit and so here we can see this pathway here so we're following it this is the this actually separates out the edinger westfall nucleus and then the motor nucleus of three and you can see how they travel here this is the you know together they're they're the ocular motor nerve and then they're traveling here and then they're going in through the through the annulus of zin and they're coming out here and they're splitting into the two components so you have a superior division and then you have an inferior division and this i thought this uh i'll mention too um so that that book actually um is accessible online um i really love the illustrations for all the cranial nerves um and kind of all the kind of the most common pathology so i'd make a note if you guys are studying cranial nerves in general this is excellent for kind of illustrations and the clarity of of how it presents simplifies things enough but yet leaves enough detail that what you need to know and this uh the presentation's on box so you guys have access to all the slides um so this uh this diagrams in health and disease that's the name of the the book this last diagram i just wanted to show is i thought was really handy because it kind of goes through you know each of the areas that the nerve can be injured and what kinds of things you see there so this is you know nuclear third nerve lesion this is where our patient had his injury um and you can actually see three different patterns depending on you know which aspect of the nucleus is injured and so you can have either a complete ipsilateral palsy along with ptosis and superior rectus palsy you could have bilateral ptosis you can also have a bilateral third nerve palsy that spares the lid and so and then you know again moving along this pathway i'm not going to go through this in all the details but um you should feel free to re refer to this a nice little diagram here and i'm going to move on to tina we didn't have a plan to have you guys kind of draw out cranial nerves but for the sake of time we may not actually do that but it's a really helpful exercise in solidifying where things are so maybe something to do on your own time or we can do it at the end if we perhaps get there so all right second case our classic 67 year old male veteran over at the va presents with binocular diplopia my goodness everything's diagonal i don't think it's been like that before but i don't really know um notice the last weekend didn't really go away so we went to the ed somehow we didn't get called but they did a full kind of stroke work up some big things so mr the brain and ekg some labs really nothing remarkable on any of that work up and so he came to ortho clinic for further evaluation he has an extensive history of sort of the usual things diabetes hypertension hyperlipidemia sleep apnea he had some stents in the past um he doesn't have any headache he doesn't have any pain there's no pain with eye movement he really hasn't noticed that his vision has changed other than the double vision making things blurry no recollection of this ever happening before seemed to come on all the sudden and then no trauma hasn't been in a car accident no recent falls hasn't been dizzy bonking his head anything like that on his exam his vision's fine his visual fields are full um color vision is intact no red de-saturation his pupils are normal they're behaving normally and then this is what his extracurricular movements look like this is also borrowed from iowa grand rounds because i don't have a great compilation of photos like this um who can talk to me about this exam any thoughts first step is which eye is abnormal actually the first step is is the head abnormal yeah that's a great that's even that better first step yeah absolutely so kind of drawing your attention first like dr. no fed said to the head tilt is great um in primary gaze he is slightly slightly tilted this way um perfect so kind of which eye is looking at normal primary gaze there's a little bit of a right hyper very very good excellent any other thoughts we can go to the kind of measurements so like baika said there you just go back so this is this is what you're going to get on your oral board exams and ophthalmology right like you can get some videos but this is for this particular pathology this is what you're going to get and this is this classic because it comes and they will make it easy for you right so um and so you're you have to train yourself to look for patterns right so when you look at you always look at the primary and then you look at the up down right and left and then if you need help you can look at the other ones right so you've got the nine cardinal positions but you should look at you know primary gaze first and identify pathology if you see a hyper you know you know that you must rule out the easy stuff which is what well this is likely uh right so so you're looking for a particular pattern right so you have a head tilt that really helps right uh and then sometimes a bit difficult this is a nice case because you also have you know with nice corneal reflexes to show you what's going on right but as soon as you see a right hyper you should be looking you know worse and right or left gaze and they didn't quite I guess give you the head tilt here but yeah so I guess with that then before I show you measurements is this worse in left gaze or right gaze and I get pertaining I think paying particular attention to the corneal reflex is really helpful in most of these photos which is kind of why they're there so worse left or right great worse left very good and then head tilt which direction does that head look like it's tilting but so yeah so he's tilted left which means that he's compensating right that compensate correct uh so that means that it is exactly you can deduce it from there but usually they will give you an additional photo where you would see the so your measurements of that patient kind of confirm things you have a right hyper worse with left gaze and then your tilt there so the three-step test is exactly what we've walked through but I want to make sure we revisit this because it's really important um what does the three-step test tell us which yeah and when can you use the three-step test that is the first question and it's a peretic test for peretic disease okay so if it's restrictive disease this is a question so if you see other features of things like thyroid eye disease or something that you know or even browns or something that you know is kind of restrictive based on history over you know how other things look uh this is useless so this is for a vertical well a single peretic muscle deviation right so really this test was designed to identify fourth nerve policies but we have occasional cases where we have like an inferior oblique uh policy for example that's a single peretic muscle so it's not just for that but this is you know primarily was designed for fourths yeah exactly yeah so whenever you see a right hyper and you're you're maybe not sure maybe you're on call and you're tired and you're not thinking very well if you want an easy way to say exactly like this was said so a single muscle is this a fourth nerve or not and kind of go from there beyond that it's not going to be super helpful to you but it will at least give you some direction to move off of and so we already kind of went through this for this patient but first what side is the hyper on in primary gaze we decided in this patient it's in the right eye um which side so is it worse than left or right gaze so you decide what in primary gaze what's going on is it worse when they look to the left or right and then your head tilt reminds you there and then some people also include xyclotorgin and cyclotorgin is part of this um which i think can be helpful in thinking about what the role of the um fourth nerve is and sort of what ox or extracurricular movements that is responsible for but not super helpful in making your diagnosis so we already talked through all these things we have a right hyper it's worse in left gaze and then right head tilt seems to be where the patient is comfortably resting in primary gaze um so this would be a positive three-step test which says um you have a fourth nerve palsy great that's easy if you got that on call now you know what's going on um what's our differential throughout just a few things real fast this is a veteran who's got all these comorbidities what's the biggest thing that works perfect yeah an ischemic kind of micro vascular issue uh what if you had a car accident three days before yeah traumatic another really very common etiology of a fourth nerve palsy anything else those are two of the two of the big ones to think about so that's great uh the other big one would be a congenital fourth nerve palsy so if by chance your lovely veteran has bought in a photo of his family uh for some reason uh and you notice that for instance they all have this tilt in their nice family photo that could clue you into uh a congenital fourth nerve palsy which wouldn't manifest itself until the patient can no longer kind of control those eye movements and he's older all of a sudden he starts noticing some diplopia micro vascular in this patient would be the top of my differential because he's got all these comorbidities it happened all of a sudden nothing else seems to be going on he has not any traumas you can kind of rule that off and then you can have all these other things masses thyroid eye disease your big stuff gca anything that's going on in the cavernous sinus all of these things can affect your fourth nerve but in this patient sort of our approach tends to be that this is a micro vascular cause until otherwise deemed anything else our approach to how we treat this what would you guys do with this patient is it going to get better what are you going to tell him yeah yeah you expect this to get better on its own if this is micro vascular it should get better if it doesn't within six or eight weeks and you haven't gotten imaging it might be a good idea to start broadening and thinking about other things maybe get some imaging at that point to rule out other sort of disease processes um but it should improve and so most people I would say would be plus minus in terms of imaging to start with this guy got a stroke workup so that's a little different um but it should get better uh and then I guess I'll briefly just touch on the course of the fourth nerve since we're not going to do that kind of drying out or we may or may not um so the fourth nerve comes out of the midbrain uh interestingly it's it's sort of at the level of the inferior coliculus and the fibers do decasate so the trochlear nuclei once the fibers leave the trochlear nuclei in the midbrain they run dorsally they decasate before running their course anteriorly um and that's important because if you have a a central lesion to the nucleus um you're going to have kind of ipsilateral versus contralateral problems depending on where that lesion is uh because those fibers do decasate and they're the only nerve that does that um the other important thing to remember and these questions come up on boards are as it runs uh the fibers kind of go laterally and into the cavernous sinus but they do not enter the annulus of zinc so that's an important distinction to remember as it comes up on boards if there's something affecting the cone or you're numbing the cone up in a retroval of our block your trochlear nerve will not be uh involved you'll maintain those movements um the trochleur is also the longest although it has the fewest axons sometimes that comes up in questions as well passes through the superior orbital fissure to innervate the muscle but we can maybe talk about its path a little more detail later all right moving right along forward always forward uh so my case this is a 13-year-old this is a case I saw about a month ago when I was coming to consults actually um 13-year-old girl uh was was riding her bike to school one day when she was unfortunately by a car um questionable loss of consciousness went to an outside ER they said actually you look you look all right so go ahead and go home went home started vomiting was a little confused so came back to the children's ER and they did an over read on the head CT and they did see some subarachnoid hemorrhage so she's admitted for observation and then management of her concussive symptoms she was inpatient for three days and then planned for discharge um and we we had our classic VA consult this is our classic inpatient rehab consult of had a patient here for four days we're ready to discharge her but now all of a sudden she's mentioning she's had double vision for four days so would you want to come see her right now because we're ready to discharge her um so I go and see her and she says that she has horizontal binocular dyplopia unsure like if it's getting better worse because she's been closing one of her eyes the whole time to to deal with it no other visual complaints at all no other medical or ocular history this is her exam um pretty pretty normal up until the extracurricular utility so her right eye moves completely normally but her left eye she's about minus three in abduction but is otherwise has full movements and then just some measurements there at bedside some crude measurements at bedside she's just such a look at those and then once again not my pictures but I thought I took it from Iowa but I didn't loads of change up here for the bcsc book so similar to maybe what she looked like but she she had a little bit of movement on abduction of that left eye her anterior segment was normal and her dilated exam was also normal we did review her ct from the outside hospital with uh neuro radiology just to make sure there was no orbit fracture that we were missing um and there was no plans for any repeat ct um given her improvement of overall symptoms so diagnosis anybody and then we'll go through differential but what was this most likely creative nerve six positive thank you and we look probably caused it it's right right channel okay so but I think it is important um when we were first talking about how to how to format this lecture I think Strav had a really good idea about well why don't why don't we try and format it in the way that we you know we go to see a patient and we examine them how do we really think through this so I mean this is probably most likely but if we go somewhere and we we see a patient that has a horizontal binocular dyplopia and really how do we start to think through this so what what could this differential be um I mean obviously we're talking about cranial nerve palsy but what could this be it could be like because of trauma it could be like um a orbital hemorrhage of some sort causing you know like a just like a mass defect on the muscle almost a restrictive component we talked about a fracture it could actually be causing a restriction by entrapment um could be due to swelling so so a lot of those things what what else besides I mean thinking kind of outside the box if if we didn't know about a trauma or something what else do we think of so think about anatomy right so start from the anterior go to posterior to to give you a good differential diagnosis right so what's the first structure that could get affected what's the end goal what's the end destination of cranial nerve six the muscle itself okay so what can happen to the muscle sure what else yeah so what's what would you call that mycitis okay what else can happen to the muscle it can become ischemic more commonly infiltrated not acutely but you know again putting the case aside but if we're talking about abduction deficit in general but not commonly involved in this disease but I'm very not good so what does it look like what disease is that nice kids yeah so this is this is exactly what I think I hope I mean I'm certainly not good at this but I think this is a really important thing to develop is really coming with a broad differential diagnosis probably one of the worst things I'm worse at actually but and going through this is a huge differential um and and we use all these clinical clues really narrow it down and but I mean I think this is something that we should be thinking of anytime we see a patient so I didn't I didn't organize it quite as well as Dr. Newfeld was mentioning anterior posterior but um one thing that really most commonly comes up with a six um and we talked yesterday about um specifically kind of the ways that the questions are organized on on our exams is a Dwayne syndrome and six are often compared and you you should be aware of how to differentiate between Dwayne syndrome and six nerve palsies so one of the important things is what happens in primary position for patients who have Dwayne syndrome versus those who have cranial nerve six palsies what do you see in primary position in cranial nerve six what did you see in primary position you see what do you see yep you see isotropia and what do you see in Dwayne's yeah so they usually their deviation in primary position is way out of proportion to the abduction deficit that they have so that's the key number one of course you have those other features of Dwayne's right but um this is one of the kind of the key things and that often comes up so that that's the kind of comparison between conditions that we talked about yesterday that's also important to keep in mind especially with the six and Dwayne's all right thank you um so the pathway of the six nerve palsy um so I tried to kind of underline some maybe important structures to be thinking about as well as through our uh like like within our differential so exits the brain stem right here uh oops sorry dang it so a couple of important structures so the anterior inferior cerebellar artery travels upwards and this is something that I think it was Dr. Katz was lecturing last week um and and I a lot of times in our morning meetings in neuro ophthalmology I've heard this structure this Dorello's canal I've really I mean I've never known what it is and probably still couldn't identify it on MRI yet maybe maybe soon um but it's this canal that and correct me if I'm wrong Dr. Neufeld but it seems to be made by um so you have the clivus here and then you have a petroclinoid ligament that stretches from the clivus over to the body of this phenoid is that correct yeah and I mean this is okay the clinoid is you know the clinoid process no I am glad you said that yeah I just pulled this out of an incorrect book I I think it's not a very good drawing too because it actually a little bit more correct to what you have on this other schematic because it actually forms almost like a 90 degree angle when it does enter the the Dorello's canal so the nerve you mean the nerve itself so this is why it gets damaged so yeah frequently in trauma so uh you know that it's I think this is probably not quite anatomically accurate in general it's like post your client like I'll look it up okay I trust you uh so but I think exactly what Dr. Neufeld said is what Dr. Katz kind of tried to hammer home with this year day we were talking about pituitary apoplexy and you know often the sixth nerve is the first one to be involved because it causes this albeit small but downward movement and you can imagine that if this gets moved at all because of that 90 degree angle it'll form that's going to get stretched it's going to get damaged and so you get this sixth nerve palsy and then similar to the other cranial nerves we've talked about passes into the orbit through the supra orbital canal through the cavernous sinus obviously but into the orbit through the supra orbital canal through inside of the annulus is in so this is not quite right because like Tina mentioned the fourth nerve actually doesn't shoot me go through the annulus but so I chose two incorrect drawings I'm sorry I was wrong take it back to one incorrect okay um just very briefly um just because I included them on the differential so internuclear ophthalmoplegia I know so this is something that I think we hear about a lot and is really important to kind of understand the anatomy of so this is due to a lesion most commonly we think about it with demyelinating lesions like an ms or stroke in the ml for the medial longitudinal fasciculus and that's what connects the cranial nerve six nucleus to the contralateral medial rectus sub nucleus so the cardinal sign of a unilateral I know is and I feel like I got this on one of the practice questions but it's slowed ad ducting so adducting psychotic velocity in one eye associated with abducting nystagmus in the fello eye and the eye with the slowed adduction may have full or limited range of abduction so that can be kind of tricky because a lot of times we want to say oh yeah it doesn't it doesn't abduct at all but it really can move quite normally um a couple other points here you could have a skew um deviation with the ipsilateral hyper deviation and patients may or may not still be able to converge and the eye know his name for the eye with the slow adducting velocity so just that example there that's so funny just wanted to point that out as a show video but I think we'll just skip it since we're trying to read you can have a bilateral I know as well which can give you this large exotropia or this wall eyed look and that can be from midbrain lesion near the cranial nerve three nucleus again most commonly it's demyelinating lesions or stroke and then it's always important to think about some mimicers and then this one and a half syndrome which is in the bcsc as well so this is characterized by an ipsilateral referring to the lesion so ipsilateral to lesion horizontal gaze palsy which is the one so you cannot abduct or or adduct and then contralateral adduction or adduction palsy and that's the half um and then if there's a cranial nerve seven motor abnormalities involved then we call it an eight and a half syndrome just because it's the cranial nerve seven plus the one and a half we already have this is one and a half syndrome so the complete horizontal peresis of the right eye and then a deduction peresis of the left eye is it all right you guys must be wondering what I'm going to present about because you went through all the cranial nerves this is going to be your last mutation okay I should just do that some bunch of issues talk about having no time so this is a complicated pattern of stir business that we'll talk about so the 77-year-old woman she had intermittent binocular horizontal diplopia for six months it was only present at distance for her so no diplopia at near it was worse with lateral gaze in both directions and her review systems we asked like the typical questions some of the questions that we asked for like thyroid disease and myosinia so no fluctuating eyelid position weakness dyspnea dysponia or dysphagia so myosinia symptoms she didn't have any headaches or pulse synchronous tinnitus or transient visual obscurations or other neurological symptoms so concerning like high intracranial pressure in her past ocular history she just had cataract surgery didn't have stir business before in the past she had no significant past medical history or thyroid disease her family had some diabetes and cardiovascular problems so on exam the visual acuity pupils pressure visual fields select exam bad exam all were normal but then she uh there were some things that were abnormal about her physical exam um let's see here Katherine do you want to describe a couple of things that you're seeing um yeah and then Rachel help her out and jump in external photo of both eyes um she has metosis um what's a big thing you notice about her organs here's our sulcus it's a deep sulcus we can see the cornel reflex in the right eye we're not focusing on the left yeah maybe a little bit worse on the left side okay so if she comes in with this is a static picture you know we said this is a shot so uh Rachel Brian is going to answer together what else would you want to test her for like what kind of clinical signs symptoms would you be interested in looking for movements or extracurricular pence yeah sure yep new hotel see if they're really she's really anothalmic um what kind of lip test do you want to do so an mrd one mrd two so outside of plastics world so um so other things you can test for in myisthenia so when you have someone look up for a long time and then you look oh that's how i don't know if i'm correct me this is wrong but when you look down and then straight ahead again sometimes the lids go like who like that yeah okay so for that too um all right it's already a start um what can you test outside the eye movements or eyelids like lab rice oh just just on exam what muscle is also weak around the eye other than the extracurricular muscles or vascular doses yeah orbicularis right that's really important to check okay and you can grade that from like zero to five that's like doctor come usually does um we have to squeeze their eyes shut and then you try to open up their eyelids and see how strong they are either side okay and maybe our optum residents can kind of work together it's just to use it you swan to us uh cover test yeah um so do you want to talk about like the eye movements here do you see anything abnormal so here's you can talk start about start with primary so primary gaze this stuff to see because there's no corneal reflex does look pretty much straight or orthophoric here it's fairly orthophoric there and on right gaze we have a narrowing of the pelvic with fissure right gaze left gaze there's no retract or on up gaze we look pretty symmetric similar down gaze so you can see the corneal reflex is here pretty similar there and also in looking kind of down and up you know down and up and right left looks like she's pretty full in all these directions it is she does have a little bit of a lower lid position here but she's a little bit more tonic on that side so again you know where this came from um so she had a left hyper um that was pretty small um in all gaze directions so pretty um competent uh we did a right head to help right head tilt and a left head tilt um just a little bit of a hyper on the left head tilt right head tilt sorry nothing on the left so we um also noted this et so when there's an et um sometimes we are concerned about cranial or cranial nerve six policies so would you say this follows any particular pattern or follows the cranial nerve six policy what about a bilateral cranial nerve six policy it's a good question yeah so um but it's also a pretty rare and she didn't she does she has full movement so she can still have a little bit of you know bilateral so at near what do you notice at near versus all these movement movements at distance measurements at distance so two smaller than four so she has yeah so it's worse it's worse at distance in here yep okay so here's our differential we talked about these first two um a little bit um about skew kind of kind of relates to four a little bit because there's a hyper um she does have a little small hyper and then we can consider that in our differential is it just a broken down four because i mean these measurements are pretty small um is it a divergence insubstancy because what kind of follows a divergence insufficiency pattern here where is it distance yeah exactly so when she's trying to look far away her eyes are just like still staying kind of converged like this instead of um um diverging and then um sagna syndrome and heavy ice and we should rename these doctor cat syndrome um or sagna syndrome and then unilateral or bilateral six nerve policies anytime there's like a weird pattern to a strabismus strabismus um d r always mentioned like considered thyroid eye disease mycinea miller fissure and wernicke's so is there like n skew too can also sometimes be there if there's a hyper um all right so here's our MRI and the arrows help us figure out what's going on so this is um the anterior here going posterior or yes it goes this way so what do you notice about these what muscles are we pointing at here oh yeah where are they fairly displaced yeah um so and they said they're not supposed to be this slow down they're supposed to be a little bit higher up and so you can see here there's quite a bit of space between that superior lateral right okay so this is sagna syndrome yeah exactly i tend to forget about this sometimes i should write out this in the last patient we saw we saw and doctor wonder was like what about the one the doctor cats loves so i i wanted to read a little bit more about it so i think this is like it's a very relatively new thing i think the first time it was ever described is around 2009 so we're talking about a very kind of recent entity um my you know my big suspicion is personally that i think a lot of us is due to a lot of prostagland and analog use because of fat atrophy that um we see uh in these people as well as you know just aging and the fat atrophy would associate them with that um but um for sure with you with the small um usually e deviations and a small you know hyper associated with these depending on the balance between where the position is in the how far the lateral rectum are just how far down they're displaced you have a little bit of a kind of variable pattern but certainly an entity and just kind of reassuring to tell patients that there is a thing that we can give them a diagnosis of that i do think that's a little bit more recognized now i think probably because of a lot of us so let's talk about the pathophysiology so this really sticks so we have two things two parts of anatomy that are important here we have the pulley which surrounds the extra ocular muscle the orbital and the global layer of the extra ocular muscle you can see that the pulley changes the vector of the extra ocular muscle here and here as well so it changes the way that the muscle functions and moves and then we have this band that there's a ligament then so they have a pulley and the connecting the pulleys are these ligaments um lateral rectus and superior rectus band that's labeled here as the most important one um for sagging eye syndrome and that tends to stretch out and then this is a nice picture of this uh Fattsman Echo T2 MRI that they published in in one of like um the first like it's the article that we actually think is the one to print out for patients and they in um our clinic so the band ligament that connects these two muscles is uh normal here it's stretched out and thin here and then it's completely ruptured here um so the band helps like suspend this lateral rectus vertically so helps keep it um vertically um elevated in space in the orbit because the inferior there's inferior tension being put on the globe with the inferior bleak specifically so if the lateral rectus is kind of slipping down to the side um there's uh good and there's also just thinking of the eye a little bit there's going to be limited superduction so we saw that for our patient a little bit and then there's um a lateral rectus tends to have this infruiting action a little bit more which it doesn't normally have um the esotropia also occurs because a lateral rectus isn't working in its full capacity at this point so it's like kind of slugging down so it'd be nice and kind of parallel um and against the globe there and so it tends to not be able to um uh at AB duct as well and then we tend to see this X cycload torsion because there is like a little bit of rotation of the globe there is there anything in terms of like this is one um I guess example of saggy eyes syndrome but it seems like it'd be fairly variable in presentation or do we often see just mostly the lateral rectus muscles being impacted yeah so we'll talk about like typical um findings and like the averages for um like uh measurements that we see as well that's a good question um so we already talked about the related changes so as Catherine described um there was this hyper upper high upper eyelid crease it's deep superior sulci that blepharoptosis or the lintosis that you described um so this is exactly what you were asking Brad so you have a small small vertical deviation about 10 percent after as an average so these are just the typical findings that have been published um in the few articles that have been published on this so far and you have a small iso at distance um and even smaller at that near so um and the full doctrines except on superduction should be a little bit limited does that answer it yeah this can still be a bit variable from there um so this doesn't follow the three-step test um and we discussed that it's not a uh periodic condition necessarily in this case when we do like the head tilt you see the opposite usually because there's the hypotropic eye is X cycletropic so the third step is opposite what we expect in a three-step test all right so we can do prisms um if it's a really small deviation uh if we tend to if patients are like tend to starting to worsen and prisms aren't working then you can try surgery but unfortunately these patients don't necessarily do um you know very well because 20 percent tend to have these symptomatic recurrences um and they can continue to have these progressive and volusional changes sometimes even after surgery because it's just um continued stretch of the time what's that there's there's just like there was a huge list that I found there wasn't any one particular surgery it's hard I mean they have to basically position the torque of us uh of the lateral rectus uh into kind of the appropriate position right so but without the support of the um uh of the septum it's challenged so they do a lot of posterior fixation for these patients so that helps suspend the the the muscle lateral rectus in the proper vertical position so um but they're challenging and that's why their recurrence rate is really high and and luckily a lot of these patients um just have such small deviations that prism in the glasses generally addresses the issues so so um I'll actually talk about one other topic and I'm gonna hand it off here so clinical signs that can help us distinguish between a restrictive versus a parietic ziplopia so um what do we mean by restrictive you guys throw out some examples so it's thyroid or restrictive or a parietic one it's more restrictive and then um parietic it would be like any of the cranial nerve policies that we talked about right um those are just some examples so with um parietic issues we usually see slow more slowing of saccades so um for example when someone has a cranial nerve six palsy when we're trying to get them to AB duct a bit they're tend to like move slowly in that AB ducting position come back I mean kind of quickly but they're just moving in that direction is slow versus if they're having if they still have a restriction when they're trying to AB duct they can move quickly to that restriction they stop suddenly so like restricts their movement does that make sense so it's like that the innervation is slow and moving it it's a parietic issue um and then with uh thyroid eye patients something that um so glad you're talking about plastic so what does Dr. Patel have us do for thyroid patients like you check the IOP in primary gaze and then you check the IOP in up gaze yeah exactly so we check there so checking the pressure when looking toward the position of restriction um can be helpful sometimes because it can increase according to some sources by like five millimeters in our career more um when compared to like primary gaze so we're actually increasing the pressure on the globe so the pressure and chocolate pressure increases when there's a restrictive issue there but not necessarily the parietic issue um because there's no enlargement of a muscle or restriction or push pressure on the globe um and then four instructions also so just so there's three different things you could potentially think of so with four instructions um what would you see in like so another example of restrictive is entrapment right so you'd actually wouldn't be able to move the um muscle the globe uh very well and against the restriction and um in predicate issues that I would move fully it just doesn't move um when the patient tries to do it okay so I call IOP testing and restrictive strabismus uh poor man's forced action testing I mean it's I've done a few forced action tests in clinic and let me tell you people don't like it so uh we traditionally um you know try to reserve it for the OR because it's very uncomfortable but sometimes you know really need to make a diagnosis quickly