 So I have a great respect for the third cranial nerve because this is a nerve that's notorious and it never follows any rule even though we have lots of rules that govern third nerve palsies. So why do I call this a troubling third? Well first it's a very notorious nerve because it's associated with life threatening pathologies. And whenever I see somebody with a third cranial nerve I always find it a difficult diagnosis even when it seems like a slam dunk because it doesn't always follow the rules that we get about the third nerve. One thing I want to just talk about a little bit is the anatomy of the third nerve because that really affects why it's so difficult and notorious. The third nerve lives up in the midbrain area and it goes through the midbrain and we're going to talk about the intrafascicular portion of the third nerve. It passes between the posterior cerebral artery and the superior cerebellar artery. It then enters the cavernous sinus where it then divides into the superior and inferior divisions of three. And then of course it goes to supply the eyelid, the superior rectus, the medial rectus, the inferior rectus, and of course also the pupil. And in this cartoon you can see the most important structures that the fascicle of the third nerve passes by. And that's the red nucleus within the midbrain and also the cerebral peduncle and we're going to see when we look at different types of third nerve policies, we're going to look at what you can see with third nerve policies besides passing between posterior cerebral artery and the superior cerebellar artery. It also gets into this cavernous sinus area where it comes in close contact with the fifth cranial nerve and then divides up into the superior and inferior branch. This is a dissection of the third nerve. It's a big nerve. It's probably one of the largest cranial nerves coming out of the brainstem, maybe behind the fifth cranial nerve and the eighth cranial nerve. And as you can see it very closely goes by the internal carotid artery and this cavernous sinus area, these are high real estate areas where other nerves coalesce. Here in a close-up view you can see how closely applied arteries are to the third nerve. And both here, right after the peduncle when it goes underneath the posterior cerebral artery, but as it goes to the posterior communicating and the internal carotid artery as well, a frequent site of aneurysms. And in this breakaway drawing of the cavernous sinus you can see how this third nerve then traverses alongside the internal carotid artery sitting very close by the fourth nerve, also by V1, the first division of V before it enters into the superior orbital fissure. Now the blood supply to the third nerve is also really important. So third nerve is supplied by numerous arterial supplies and that means that it has a watershed zone. So anteriorly you can see that the ophthalmic artery, let me use the arrow here, so you can see that the ophthalmic artery supplies sort of that portion that is going towards the orbit, but then the infralateral trunk comes off and it supplies numerous things, but it has a huge supply to the third nerve. And then the posterior cerebral artery also supplies the third nerve. That means that there are these watershed zones where arterial supply comes in and it makes this nerve more susceptible to ischemia and this is supposedly how you get an ischemic third nerve palsy because of these three arteries at least supplying the third nerve. Now the other thing that's extremely important to realize is that the pupillary fibers aren't widely dispersed in the nerve. They start out superiorly as they leave the midbrain and this becomes important, right? Because I had a patient where we were really wondering about whether there could be compression on the third nerve causing a dilated pupil, but you have to know where the pupillary fibers are and so when it leaves the midbrain they lie superiorly and as it goes medially, as it goes further out into the cistern you're going to see it move medially. So it goes from superior, superior medially to medial and then it goes into the orbit on the inferior division of three. That means that when it's sitting in that internal carotid posterior communicating region those fibers are medial and guess what's right there? It's the connection between the internal carotid and the posterior communicating and when those aneurysms hit it they're going to cause that pupil to dilate. So these pupil, where the pupil fibers are greatly affects whether you are going to see pupil involvement or not. Now I'm going to go through, I'm going to show you cases and all the rest of this lecture is basically cases to help us understand the third nerve and I'm going to start with nuclear third. This is a very rare condition. I probably have maybe seen two nuclear thirds in my whole career and they're never completely complete but you do need to know about it because these nuclear thirds take out the levator complex which is the central caudal nucleus and that means that both eyelids are down and so are both superior recti so it's very specific and you may get a little flavor of a partial kind of third on one side but you see bilateral ptosis and bilateral superior rectus involvement at least partially. And stroke is the usual cause of this although you can also see it with tumors. And now let's look at a case of a nuclear third. So this is a guy, can we get the volume up, does anybody know how to get the volume up here? And it's all right, you can just see that he had bilateral ptosis. Now here's what's bizarre of course. He's got medial rectus involvement on the left side and that's part of the third so you see these variations of partial third nerve palsies and you can see his down gaze is not bad okay but his up gaze is going to be affected in part and then this bilateral ptosis and then a variation of a third nerve like a medial rectus deficit but the characteristic finding is this bilateral ptosis, variable up gaze problems and then you'll see a partial third when you see them. So you could see where somebody might think oh is this an INO, is this something else but you really have to look at that bilateral ptosis to tell you that that's what's going on. So this is a nuclear third nerve palsy and this wonderful video was done by Dr. Shirley Ray. Now because the third nerve in the midbrain goes right by the red nucleus and the cerebral peduncles you can imagine that you can get different syndromes that are affected by this vesicular third and this frequently is either going to be weakness, it's going to be tremor or an ataxia usually on the opposite side so you'd see the third nerve on one side and then you'll see weakness on the other side, tremor on the other side and you might see a little bit of ataxia also on the other side. I have seen this diagnosis in triage clinic at least three times twice within the last five years so this is not completely rare. So let's look at one of these syndromes. So this is a third nerve palsy and then you're going to tell me whether it's Weber. So here which side is her third nerve palsy on? It's going to be on the right. Now let's demonstrate the features of the third nerve palsy besides the ptosis she's able, she can't ediduct that eye, she doesn't infiduct that much either and of course she's got elevation deficit, she's got good lateral rectus function so her sixth nerve is intact and now she's going to demonstrate the nerve exam. You can do this in the chair, this part you can do because all you've got to have them doing is sitting, put their arms outstretched, if they're weak they're going to not be able to lift that arm up, right? She's got a good facial strength, now so what is going on here? So she's not weak, it's not a tremor, what would you say is going on with that left arm? Ataxia, right, okay so if she's ataxic which of those three syndromes is it? She just gave you the answer. Let's go back to this one here. So Weber is when you're weak on the opposite side, Benedict's is when you've got a tremor with ataxia and sometimes you can have choreoethytosis but Claude syndrome is on ataxia so she had Claude syndrome from a stroke that affected the midbrain, alright. So those are kind of the central third nerve syndromes that you need to know about, now let's talk about what are the rules that we learn about the third nerve. So the first rule that we learn is when there's a complete ocular motor nerve palsy with completely intact pupillary function it's usually ischemic and no imaging is required unless it doesn't get better in 48 weeks, isn't that kind of the rule, even in medical school you learn that that's sort of the rule. We can talk about imaging controversies as well. When there's a thelmaplegia ptosis and a poorly reactive pupil so the combination of the ocular motor nerve palsy ptosis and the pupil is poorly reactive that sends off bells, whistles, red lights, there's serious pathology and you've got to do CT, MR, conventional angiogram because you've got a pupil involving third nerve palsy. And the third rule is if there's a completely, if there's a non-reactive, poorly reactive pupil without any ophthalmoplegia ptosis or other localizing findings you don't suspect a beginning of a third nerve palsy usually you're thinking tonic pupil, pharmacologic blockade or some other cause of the pupil. So now I'm going to take you through why these rules don't always work for a people and why this third nerve can be such a difficult one. So this is a diabetic woman and she came in with this third nerve palsy. Now the first thing you notice, there's a couple things on this and the first of all I'm just going to tell you because it's hard to see, that that left pupil is just slightly larger than the right pupil, just very slightly larger, it still works and there's one other finding on here that tells you that this is not a complete third. What's the other finding on here? What is it? That her pupil's not completely, or that her lid is not completely down, right? So her lid's not complete. So there's two things here, it's got, she has incomplete ptosis and she has a slightly large pupil. So it is true that about one out of five ischemic thirds will have a small amount of pupillary involvement. But in a study that's been done and replicated, my colleague Dan Jacobson when I was a fellow actually did this study where he took relative pupil-sparing third nerve palsies and yes, while out of the 24 patients, 10 of them were third nerve infarctions, these relative pupil-sparing third nerve palsies also ended up being pericellar masses, either primary or secondary, eight of them, eight out of the 24, a third of them, aneurysm and two, carcinoma and infiltration, leptomine and gel involvement in one, Tulosa Hunt syndrome, and so on. So while the rule is that if the pupil's spared mostly, it should be a scheming. It doesn't always follow the rule on that. So you can't, the answer to the question is when you see a pupil, there is partial pupil involvement or an incomplete third, you cannot apply that ischemic rule. Now yesterday we saw a patient with a flat out third nerve palsy, painful third nerve palsy, no pupillary involvement, but it was a complete third nerve palsy. He couldn't look in, up or down, and he had a completely spared pupil. And so we were able to apply that rule, but if it's partial, you really need to be aware. All right, now here's another case. This is a woman who we're lifting her lid because her lid is completely down, and while it's a little difficult to appreciate, she does have a large pupil that is very poorly reactive. She doesn't look up, she doesn't look down, she cannot AD duct, and you can see over here her adduction is definitely deficient. She's got fine abduction. And so we call this a pupil involving third nerve palsy, and do we just say, listen, why don't you go home? We'll see you in four to eight weeks. And Trevor says, no, we can't do that. So we did immature, and she did have a PCIC aneurysm compressing the third nerve. And because those pupillary fibers were right there measly, right? Remember when we talked about how the pupil fibers come on the top and move measly, medially on the nerve, it compressed the pupil fibers and that was a third nerve palsy. And these aneurysms are notorious for compressing the nerve. They usually never just cause an isolated dilated pupil. You always see something more with it. You can find an exo, you can find a little ptosis, et cetera, et cetera. So it's usually a partial third. So here's a pupil involving third nerve palsy. The guy's lid is down, so it is complete. Often they're a little exo if you raise their lid, and you can see how that pupil is large. There's sometimes a little bit of movement, a small amount of movement. But you can see that he cannot depress the pupil, and he can't elevate the pupil, depress the eye, he can't elevate the eye. And so this person actually had a, and this is just demonstrating the large exodeviation that he has as well. But that person actually had a dolocortatic vessel that was compressing his third nerve and giving him a pupil involving. So I wanted to just stress again where the pupil fibers are, superiorly, going measly and entering in inferiorly, and always look for a small amount of exophoria or slight ptosis if you see a big pupil. The pupil may lack true denervation super sensitivity in the pylocarpine testing, and beware if there's pain. This was a patient sent to me for an 80s pupil, and this was a while back. But you can see that she's got bilaterally big pupils, right? And when we shine light in her eye, the left pupil came down somewhat. The right did not constrict whatsoever. What, is there any, this person was 28 years old, she had a new onset of headache over the right eye, continuous pain, she noticed this dilated pupil. And so the question is, is this an 80s pupil? This was after pylocarpine testing and the pupil did not come down. Is this an 80s pupil? Is there any clue that tells you something else could be going on here? It's also tautic. But, pardon? So she may have a little ptosis, okay? What else do you see? Bit of exo. She's got exo, right? She's a little bit exophoric there. And she really had very little, except for the pupil, the ptosis, and an exo. That was it. But it was the pupil, the ptosis, and the exo that told me something had to be going on. So we got her CT scan. And we got the CT scan and it was read as normal. So is this a normal CAT scan? This is a CT with contrast. Is this a normal CT? Dr. Jacobson, is this a normal CT? Dr. Wang, anybody? Do you think this is a normal CT? Dr. Baer? Okay, why, Chris, why do you say no? What? You're showing it to us, I'm assuming it's not normal. I'm looking on the right side, because that's what we expect the pathology to be, right? All right, so on the right side, you're seeing a little bit of extra enhancement, like right in here. And maybe a little widening of the cavernous sinus here. And that's what I saw too. So I sent her for an MR. And she actually had a metastatic tumor in the very malignant pituitary cancer, and she was dead in six months. So this, I just want you to be aware that when you see this pupillary dilation that has a partial third, there's going to be something going on here that you have to look at, okay? All right, now this is a lady who came in with a bout of a partial third nerve palsy, pupil sparing, and she got ptosis, and she had diplopia, and she was exo, and this happened three times. So this is what we call a repetitive third nerve palsy. And each time she would get enhancement of her third nerve, right through the cavernous sinus, and so you can see these idiopathic repetitive oculomotor nerve palsies in normal people. Usually it's thought to be viral infection, and one of these episodes we did do a spinal tap and found white cells in the spinal fluid, but it is one of those things that you do need to be aware of that you can get repetitive third nerve palsies. Do those patients deserve repeat imaging? Pardon? Do those patients deserve repeat imaging, or do they get like one time or something? I repeated her imaging almost every time because I was worried that she had something else in addition to this idiopathically recurrent third nerve palsy. It's good to know that you can have recurrent third nerve palsies like this that can be viral related, but I think you always have to be circumspect. In my experience, this is why the third nerve is so hard because it doesn't follow these rules, and then it can do weird things like become a repetitive third, like what, you know, you have to be very careful with these third nerve palsies. All right, now I want to talk about third nerve palsies in children. These can be associated with aneurysm, schwannomas, infections, migraine, and they can be from trauma. This was a boy that I saw who had a right third nerve palsy, and he also had headaches, and they saw an abnormality on his MR scan, and they wanted to go ahead and remove this abnormality on the MR. But you should be aware of this. So this is this little enhancing lesion at the nerve root exit zone of the third nerve right here and here, and they were going to go in and remove it. Well, if they'd removed it, number one, he would add a complete third nerve palsy for the rest of his life, and number two, this is very typical of these recurrent, painful, ophthalmoplegic neuropathies, or it used to be called ophthalmoplegic migraine, but they're usually a unilateral headache with ipsilateral parisys of one, two, or all three of the ocular motor nerve. So it could be third, which is the most common, fourth, sixth, and it's usually painful. And then you usually can see this little enhancing lesion, and it goes away. That little enhancing lesion will go away, but it's right at the nerve root exit zone. So I talked to the neurosurgeon said, don't remove that. This is going to go away. Let's re-image him down the line, but let's not go and give him a permanent third nerve palsy. But you do need to know about sort of these repetitive third nerve palsies, this recurrent, painful, ophthalmoplegic neuropathy, recurrent neuropathy. All right, now I'm going to switch gears to a different problem. And this is a 34-year-old man. He has had a two-year history of horizontal double vision. He then had a spell in 1994, and he had a normal MRI scan. And on exam, his acuity was 2020, had no afferent defect. He had slightly slowed adducting saccades. He had a minor limitation of adduction and depression in the left eye. He had a 35-diopter x-euphoria, and it was actually tropic intermittently. And then his visual fields were normal. So now let's look at this picture and try to determine what's going on with this guy. So when he looks at you, let's just look at him, when he looks at you, on primary gaze, what do you see? Say it loudly. So we give him a little ptosis. Okay, anything else? A little x-o. Okay, when he looks to the right, adduction deficit, and he's got a little bit of, what do you notice when he looks to the right? Lid retraction. Okay, what does that signify? Lid retraction. Abherent regeneration. Exactly. Okay, so abherent regeneration. Now this guy did not ever have a third nerve palsy. He came in with this intermittent kind of double vision, then it became more complete double vision. When you see abherent regeneration, especially of the third nerve, there's pathology. And he did have a pituitary mass tumor. So these cellar masses, so when I was talking about how it goes right by the cavernous sinus, these cellar masses really just invade and compress the third nerve. And it's a notorious area for getting tumors to cause abherent regeneration. So what are the subtle signs of abherent regeneration that you can look for on exam with a third nerve palsy? So one, and the easiest one is this eyelids and kinesis. Okay, so that you've got a little ptosis, and then when you put the eye in that position, so when he was looking to the right with his left eye, his eyelid just pops up. So that's a pretty easy one to see. A graphe sign is kind of a retraction elevation of the lid on down gaze. So they look down and their lid pops up. Okay, and it looks like they've got lid retraction. Retraction of the globe. You can actually see almost the globe retracting. And then adduction of the eye, if you're looking up or down, you can see adduction of the eye with vertical movements. Sometimes you can see the pupil constrict in adduction. So the abherent regeneration is with the pupil and the third nerve. And then you can see an okay and change. The rule here is you see abherent regeneration. It's a intra cavernous tumor or meningioma, until proven otherwise. It's absolutely going to have pathology if it's got abherent regeneration, primary abherent regeneration. So here is somebody who's got abherent regeneration of the third nerve, bilaterally. So when he looks to the left, one lid opens up, when he looks to the right, his other lid opens up. So he's got synkinesis with eye movements. Okay, now I'm going to talk about intermittent thirds. So now intermittent thirds are rare, and they're usually transient spasms of the muscles that are innervated by the third, the sixth, or the fourth. And the key here is there's usually a previous history of radiation. So like pituitary radiation or something like that. And what happens is that they can look normal. And then all of a sudden, they have this muscle, it's like a muscle cramp. And you do have to image unless there's been previous radiation. And now I'll see if I can get this to work. This is the video that sometimes has the hardest trouble. So this is a guy with intermittent third nerve palsies. And so we're just looking at him, we're going to ask him to move his eyes around. He doesn't really have any major ptosis. He did have a little bit of XO there, maybe a little hyper. Fire left gaze. So what we did was we put him into one of the gazes and held it there for a while. And then see how the meteorrectus just fires. And it's like a cramp of the meteorrectus muscle. And this is called neuromyotonia, ocular neuromyotonia. And then it goes back to normal. So it's something to think about when you see somebody with intermittent dyplopia, to at least ask about whether their eyes kind of get stuck in a certain position. And he can get it to go away slowly by relaxing his eyes. Sometimes blinking can make it go away So sometimes you can treat this with gabapentin carbamazepine. So there are ways to treat it. And then reassurance, I mean, he hasn't had a history of previous radiation. This is not a common thing to happen. But at least you need to know about it. Okay, so pupil involving third nerve palsies, you have to look for other cranial nerves because it sits very close to the fifth nerve. Imaging is absolutely essential. MR scan has to be done. And often in MRA, sometimes you have to do angiograms if the MRA or CTA is negative. And always think about another diagnosis. I had a guy with a pupil involving third. Did the imaging, did angiogram, everything was negative. And then you got another cranial nerve palsy. And we did a lumbar puncture and he had actually had lymphoma. So it's really important. If you've got a pupil involving third, you shouldn't be sleeping at night. Okay, that you should be thinking about it. Pupil spearing third nerve palsies. Remember, it's relative spearing. Most of the time you're going to see a little anisocorrhea. These are usually painful and they should be complete. If you're going to call it an ischemic third, it better have hypertension diabetes as risk factors. It better have pain. It better not have aberrant regeneration. It better not have anything else going on with it. It better just be a complete third nerve palsy with pupil, basically pupil spearing. All right, now I'm going to go into a section that I call third nerve plus. So this is an African American man. He was actually at the VA hospital. He had fever, pain. He had increasing diplopia. He had a third nerve palsy, proctosis and numbness of his right cheek. Okay. Now, when you get numbness, the other lesson here is when you see a third nerve palsy, you've got to look for the fifth nerve. Okay, that's like part of the deal. You got to make sure that the fifth nerve is intact. Why do I mention this? Because if cavernous sinus lesions are going to give you trouble with the fifth nerve. Absolutely. So he has numbness on the right cheek. So what division of five is that? Two. And what are you going to just say, well, you know, you've got a pupil involving third. Well, you know, we'll see around. We're going to image him, right? So we imaged him and we saw that he's got a widened cavernous sinus bilaterally, really wide. Here's his carotid arteries. And he had cavernous sinus thrombosis. So fever, headache, paristhesias, often that chemosis, often it'll be V1 involved, but it can be V2. And of course, orbital vein thrombosis could look a little bit like this. But what is going to be different about orbital vein thrombosis versus cavernous sinus thrombosis? Trigeminal involvement. Absolutely. That's the key piece that you have to go after. And you have to think about things like telosahant, which we'll talk about in a little bit. Mucor orbital apex syndrome. And of course, checking white count, treating him with antibiotics, etc. So the cavernous sinus syndrome is really a third nerve, sometimes fourth. How do you tell a fourth nerve is intact? And Trevor got to do this yesterday. How do you tell that the fourth nerve is intact when you have a third nerve palsy? Do you remember how we did that yesterday? There were so many patients yesterday you probably forgot. You can't remember. Okay, anybody else? You have them look down and you look for intorsion, and that'll tell you that the fourth nerve is intact with a third. But you have to be thinking pituitary tumors, meningiomas infections, but having that numbness or any problem with that fifth nerve or a horner syndrome really brings it out of the brings it out of an isolated third nerve into this what I call third nerve plus, which means you have to image him because there's always something going on. All right, what do you think he happened here? What? Shingles. Okay, so yeah, this is a woman who had horrible, horrible, horrible pain over her left eye. Then she developed a little ptosis, then she developed a third nerve palsy. And it wasn't until the rash came out that we stumbled to the fact that she had a third nerve palsy, but that's that she had shingles and her disaster. I think you have a video playing in the background. I don't know where it is, but do you think you know where it is? This one? Oh, let's get rid of that. Okay, all right. So she actually ended up having enhancement around the cavernous sinus and even the third nerve enhanced. And you could see the enhancement of the third nerve as well on the coronals. And she actually had a small stroke after this. So a zoster is not a benign condition. This is a woman who went over to Wendover and got into domestic coral and in the parking lot. And so she's got her lid down. She has proptosis and she developed a sort of pulsatile, a pulsatility around the third nerve. She had complete ophthalmoplegia. And so what do you think happened to her? And I've got a MR scan that has the answer here. Chris, you're shaking your head, you know. Fistula. It's a CC fistula. Great. And so here on this T2, you can see this is really interesting because the cavernous sinus has these venous channels that can connect both sides. And you never see those open unless you've got blood flowing through the cavernous sinus. So she had this huge fistula that needed to be closed. And all right. Now this is a 59-year-old woman. She had a long history of migraine, but she developed a new headache over the right frontal region. Her acuity was normal. She had ptosis. And then she had limited depression and abduction. So she had a right hyper. She had an iso. And she had reduced sensation over V1, V2. So where do you localize the lesion? Anybody? Localize the lesion. So we've got ptosis, limited depression, and also an abduction deficit as well as decreased sensation over V1, V2. Cavernous sinus. Okay. And here she is. So she's got a little bit ptosis, little limitation of depression, also slightly poured abduction. And what she had was enhancement of the cavernous sinus that went all the way back on the dura. It was the cavernous sinus on this side was very much enhancing. And this is, we did a spinal tap and she had elevated protein. And then she had resolution with steroids. So this is Tulosa Hunt. It's a painful ophthalmoplegia. It can occur at any age. The third nerve is notoriously involved almost always. Sixth, fourth, fifth, and sympathetics, variably. You can't see ptosis. Rarely you can see optic nerve involvement. You've got to do an MR with ghetto, ghetto lineum. And steroids are the treatment for Tulosa Hunt. And but it can be due to tumors, infection, and other disorders. So it's, it also is one of those really difficult diagnoses that you really have to pull out all the stops to work it up. So this, this guy came in with a painful ophthalmoplegia on the right side. He had diplopia and then he had a decreased corneal reflex. And you can see he has almost a complete third nerve palsy where his lid is totally down. He can't AD duct at all, can't look down. And, and he had numbness, he had loss of the corneal reflex, which took it out of just a third nerve palsy. And you can see on his scan, he has a wide cavernous sinus on that right side. And what this ended up being was small cell cancer with a lung primary tumor. These Tulosa Hunts are notorious for harboring nasty things. And you, you see this, you really have to work it up completely. So the problem of Tulosa Hunt, it absolutely requires imaging. You often have to do a CSF examination. And you have to really, even if imaging is negative, you've got to think of other things. Diabetes can mimic this because of the pain. Giant cell arthritis, syphilis, rheumatoid arthritis, systemic lupus and prednisone for a true Tulosa Hunt, which is an idiopathic inflammatory condition of the posterior orbit or cavernous sinus is prednisone. But the problem is that Tulosa Hunt is extremely difficult and you always have to work it up. So just a couple other conditions that I want to bring up before the quiz. So this is BJ. She's 12 years old, a rubber ball hit her eye two months before. And she had the slow onset of ptosis of the right eyelid, then double vision. She had an MR scan, which was normal. She had a normal afferent exam. Acuity was great. Pupils were normal. But she did have a two-diopter hyper, an XO in left gaze. And her mom said, I think that the kid who threw the ball caused this in my daughter. And this is how she looks. So let's look at the photo and see if we can kind of diagnose what's going on. So Catherine, what do you see here? So she has some rightosis. She has adduction. She does an adduct. Okay. So it looks like a partial third, right? Okay. So imaging is negative. Is there any other tests that you would want to do on this kid? Can you think of anything else you could do? You already did vessel imaging? Huh? You already did vessel imaging also. Vessel imaging has been done. Yes. I mean, this kid got everything done. Are you kidding? The mom? Your kid has a third nerve palsy. What are you going to do? And you're going to, you're going to go, you know, she's like, you could do an LP. Is there anything else you could do? Forced adductions. What? Forced adductions. Forced adductions. Good idea. Why would you think about forced adductions? Because it was traumatic. Maybe there's some impingement on the muscle or something like that. Okay. Well, I didn't, I, there were a couple other clues to me. One clue was in the morning, she would look pretty normal. And by the end of the day, she looked like this. So now, what clue does that give you? Right? So we did a rest test and she was totally normal. So not all third nerves are what they seem. And I'm going to tell you the three things that I look for. One is myasthenia. Now myasthenia is never going to give you pupillary involvement, right? Never put that in your brain. Never. You're not going to see pupils involved with myasthenia. So if pupils involved, it is not myasthenia. Okay. So myasthenia, myositis. So inflammatory conditions or muscle conditions, graves disease. And the third one that I sometimes put in here, but I didn't for this lecture is multiple sclerosis. You can see a partial third nerve palsy as the presenting sign of multiple sclerosis. Usually there's a lesion in the midbrain, but not always. So be thinking about these mimicers. So here are my recommendations for troubling thirds. One, you may want to know the rules, but you better know the exceptions to the rules. Okay. Know the exceptions to all the rules that we talked about. Use caution and applying these rules to young people less than 20. And kids, they never follow the rules at all. And if there's an extraocular muscle palsy is incomplete, when that third nerve palsy is incomplete, you've got to be careful because that is not a complete third. And all of a sudden it's brought into the more complicated category. If the pupil's partially involved, you've got to work them up. Do not apply these rules unless it's an isolated third nerve palsy. And by that, I mean, you've got to check that trigeminal sensation. Look at the corneal reflex. Think about other entities as well. If the patient has cancer, these rules do not apply. Every single patient gets a complete workup. Even if the image is negative, angio is negative and the pupil's involved, keep looking. Think about doing a lumbar puncture. Think about repeating the imaging. Maybe the imaging wasn't adequate. Okay. And with that, I've got a quiz. So do you have a piece of paper? This is... Would you say an extraocular muscle palsy is incomplete? So if it's not like... So they don't have like a thomaplegia of the third nerve. And if they have a complete ptosis and like affecting all of the directions, just not complete. Okay. So complete ptosis and complete, I mean, like they may be able to adduct a little bit like that diabetic third that I showed you. There was a little bit of adduction. There was a little bit of elevation, but it was complete ptosis, no pupil involvement. That's a complete third. Okay. The partial thirds are where the lid isn't completely down. Well, only one or two muscles are really involved. Those incomplete thirds are the ones that are going to get you into trouble. Okay. And remember, and the bottom line is third nerve palsy, if they don't make you nervous, they should. And I want everybody to think about, you see a third nerve palsy, almost all of them get the image, almost all of them, maybe accept, you know, diabetic, hypertension, hyperlipidemic. I mean, totally complete, like we saw yesterday. You could argue why image this. That's what this is. It was painful third nerve palsy in a diabetic, you know, who's hemoglobin A1C was like 12 out of control. Lipids were off the chart. I mean, he was a mess. So, okay. A 55 year old patient, this is number one, 55 year old patient with diabetes presents with dyplopia, which would lead you to order an MR of the brain as the initial test. An isolated pupil sparing complete third nerve palsy of three days duration, a third nerve palsy with bilateral fatigable ptosis, an isolated pupil sparing third nerve palsy of eight months duration, a patient with lid retracted, restricted up gaze, and a slight proptosis, which would have you order the an MR as your initial test. It's only one of those. One of them. I know. I know you want imaging for everything, but there's only one on this one. There's one that we talked about. Okay. Ready? Number two, what is indicated if you suspect aberrant regeneration in a resolving ocular motor palsy number three, presumed to be from diabetes, no further workup, sed rate, CRP, MRLP. So, it's aberrant regeneration. Okay. Three, a diabetic has dyplopia with limited elevation, depression, adduction, ptosis on the left. Pupils are three millimeters on the right, 3.6 on the left, in light, and five and 5.5 in darkness. Your next step would be to reassure and follow up in three months. Image, do a tensile on test, have the patient return to clinic every day to watch the pupil to see if it gets bigger. Number four, a 75-year-old man has a pupil sparing right third nerve palsy. The right corneal nerve sensation reflex is absent. The headache, a headache is present on the right side. Are you going to do an MR with gadolinium, looking at the cavernous sinus, do an angiogram to look for an aneurysm, sed rate to look for giant cell arthritis, or a tensile on test. What will be your initial study? A six-year-old child comes in with a third nerve palsy. The possible diagnosis includes myosinia, aneurysm, migraine, schwannoma, or all of the above. Number six, true and false. A nuclear third would present with bilateral ptosis, true or false. Seventy. If you suspect to loss a hunt, don't image, just start steroids immediately and see if it resolves, true or false. A woman presents with a quote-unquote blown pupil, but a completely normal exam. Your next step is an MR scan, dilute pylokarpene, full strength pylokarpene, admit to the hospital with a neurologic consultation. Number nine, a person with a pupil involving third nerve palsy has a normal MR, MRA. Your next step is reassurance, a lumbar puncture, angiogram, or a tensile on test. And number 10, the third nerve passes between the superior cerebellar artery, the posterior cerebellar artery, both of the above or none of the above. And number 11, the pupillary fibers are always inferior on the third nerve. And all of these can be seen in the novel library, so all those videos that we show today are in the novel library just to tell you about it. Okay, let's go back to the quiz. Number one, 55-year-old diabetes, double vision. Which one would lead you to order the MR as the initial test? C. That's correct. Okay, because it's eight months duration. What is indicated if you see aberrant regeneration? C. C, MR scan. A diabetic has dyplopia with limited everything and the pupils are like that. What would your next step be? Reassurance. Okay, so this one, I would say there's relative pupillary sparing. I would get an MR. Because the MRs, the pupils are unequal in both light and darkness and it's over, it's not quite a millimeter, it's a half a millimeter. I would probably get an MRI scan on this one. I thought you said that there was, I thought you considered this relative pupil sparing and this was like a little bit anisocoreal. You came in after the slide that said relative pupil sparing and I watched when you came in. You came in after the slide that says relative pupil sparing in 24 patients, 12 of them, were something else. Okay, the rest of you got this one, right? Yes, because we talked about this. Okay, just say it. You miss a second, you lose a point. Okay, 75-year-old man, pupil sparing, right third, but a corneal reflex is gone. Eight. Six-year-old with the third nerve palsy. E, all of the above, they can have anything. Third nerve palsy, a nuclear third would present with bilateral ptosis. True. Tulosa hunt, don't image, just start steroids, falls. A person comes in with a blown pupil in a normal exam, completely normal exam, be dilute pilocarpine testing, and then if that didn't work, the full strength pilocarpine because you're looking for somebody who's got pharmacologic dilation. And these can be hard, I recognize and sometimes you have to think differently. So then a person with a pupil involving third nerve palsy with a normal MR, normal MRA, the next step would be, I will accept B or C because in this situation I would keep going, either B or C. I would not reassure and I wouldn't do a Tensalon test because the pupil's involved. And we talked about that. Okay, third nerve passes between, it's C. It passes, and I said this so many times, at the beginning before you came in, Marshall. The posterior cerebral artery and the superior cerebellar artery, it passes right between those two arteries as it comes out of the third nerve. And the pupillary fibers are always inferior. Now this one I know you got because I showed the pupil fibers like three times. What is it? True or false? False. All right, good. All right, so troubling thirds, can you see where I say they're troubling? I mean they should keep you awake every night. I know I seriously, I see a third nerve palsy. I saw one yesterday and so I don't, my sleep score last night was bad because I saw the third nerve palsy. I also saw eight other patients, many of whom had really bad stuff. So yeah, it was a, you know, but third nerve palsy, even when you think you've got every rule, they never follow the rules and they should make you all uncomfortable. And if you walk out of here with a respect, total respect for the third nerve, I've done my job. Okay. All right, so I'll take your scores. The pie is on the line and up, and we'll end this now.