Bowhunter syndrome (BHS) is a rare but important cause of posterior circulation stroke in children, resulting from vertebral artery compression during head rotation. In this Neuroscience Grand Rounds session, Jacq Wood, MD highlights the pediatric-specific presentation, risk factors, and subtypes, noting that children often present with stroke rather than transient positional symptoms.
Learning Objectives:
Identify the subtypes of Bowhunter Syndrome in pediatrics.
Identify the risk factors for Bowhunter Syndrome in pediatrics.
Explain the treatment options for patients with Bowhunter syndrome.
Yeah, I'd be, I mean, uh, be happy to, uh, Whoops, I I'm just having a little difficulty here. There we go. Uh, so Doctor Woods, um, joined us this past year as a fellow for neurocritical care, um, and, um, she said, uh, um, uh, she will be having, excuse me, she'll be taking up a position, um, and you'll have to remind me exactly which, uh, hospital it is, Jack, but I know it's back at, um, um, in Baltimore, um, and, uh, will be a critical care at a neurocritical care attending there. Um. I don't have her CV in front of me, so I'm not able to give her background history, but, um, I'm sure she'll be able to introduce herself as well. Uh, but it's been a real pleasure having, uh, Doctor Wood with us this year. Uh, I just learned last week, unfortunately, she won't be at the graduation, but uh, we certainly wish her well for her future career and she's going to be talking to us today about uh pediatric Bohunter syndrome. Thanks, Doctor Freeman. Um, yeah, so I did my residency, uh, here in Baltimore at Hopkins PCH for fellowship, and then I'm gonna be joining, um, Yale in September for as part of their NCC faculty. Um, yeah, so today, thanks for having me. I was gonna talk about pediatric bow hunter syndrome. What do we know and more importantly, what do we not know? Um, I have no disclosures. The objectives for today are to identify the subtypes of bowhunter syndrome in pediatrics, identify the risk factors for it, and then explain what the treatment options are. And a lot of what I'm gonna be talking about today is really gonna be about how in, in a big way, we don't really know what the best treatment is a lot of the time. And so that's really what, um, what the field is working on. Uh, so I wanna start with the case. So this is a 2 year old boy. He woke up one morning with irritability, vomiting, neglect of his left arm, and altered consciousness. His MRI showed a left superior cerebellar artery stroke, um, which you can see here, this is an axial section and this bright part, is a DWI and this bright part is the stroke. Uh, the team carrying for him got neck vessel imaging. Um, it was an MRA. It was motion degraded, and they didn't pursue any further imaging at that time. He was found to have an MTHFR mutation, uh, so this was thought to be causative. He was started on aspirin, discharged home. Three months later, he awoke with vomiting and irritability, and he was found to have a new stroke and now in his right cerebellum. So again, this is the same, um, type of picture, and axial, and this bright part is again the stroke. It's a little farther up, and it's now on his right side. As well, and he also had a left posterior temporal lobe infarct. Um, again, an MRA was, was, uh, done, and it showed decreased caliber of the right vertebral artery. He got a follow-up CT he received TPA, um, and then a follow-up CTA was recommended. However, he only got an MRA, um, it was unrevealing, it, uh, but then he underwent a diagnostic angiogram, which showed a dissection of the right vertebral artery, just distal to the right C2 foramen transversaria. Retrospective review of his prior MRAs showed that this was probably there though, uh, was able to be found on those prior MRAs once we knew exactly where to look. Um, so then he got a CTA and he got a bone reconstruction, um, and that showed a partially ossified congenital arcuate foramen encircling the right vertebral artery as it coursed along the posterior neural arch of his C1 vertebrae. He was started on Lovenox and placed in a hard sea collar. He underwent serial CTAs and once he, once they showed healing of his vertebral artery dissection, he underwent a repeat DSA with rotational head testing. For this procedure, the interventionalist injects dye and then rotates the head and sees if at any point the dye stops moving. Um, when it was done for this patient, it showed that when his head was rotated to the left, there was a profound decrease in the flow through the right vertebral artery at the C1 to C2 level. He underwent surgery to decompress that right vertebral artery. However, on follow-up DSA, he still showed that lack of flow with rotation to the left, so he underwent a C1 to C2 fusion. He had follow-up for more than 2 years without any further strokes, and then notably in the history, he had a history of torticollis, subjective hypermobility, and ligamentous laxity. So this is an example of a patient who has what I'm gonna talk about today, which is pediatric bow hunter syndrome. Pediatric bow hunter syndrome is a condition where head turn causes mechanical stress on the vertebral artery due to either abnormal adhesions or impingement, often leading to vertebral artery dissection, resulting in posterior circulation stroke from artery to artery embolus. That is a really dense definition, and I'm gonna break down all of those parts, but before we talk about what goes wrong in the pathology of bowhunters, I wanna talk about what the normal structure and and function in that area is. Um, so for the vertebral arteries, humans have two vertebral arteries. They come from our bilateral subclavian arteries, and then we, we talk about them in different segments. So the V1 segment runs from the origin of the subclavian to the C6 transverse foramen, and you can see that, um, on kind of the bottom right of that left picture, and then on the right picture, it's the green segment. And then the V2 goes through the transverse foramina on either side of the C6 to C2 vertebral bodies, and so that's gonna be the red segment on that photo on that figure to the right. Um, and then there are a couple of different naming schemas for where you where you transition from V2 to V3, um, but the one that we most typically use in neurology is that as soon as it comes out of the superior portion of C2, we now consider that the V3 segment, it goes up through the transfer foramen of C1, and then one thing that I want to get your attention to is if you look at C1, you can see this loop of the vertebral artery sitting on top of C1. And that's important because um that redundant length of artery is what allows us to turn our head, and I'm gonna talk more about that. And then that yellow segment is where it enters the dura, and that's the V4 segment. And then once you get into the dura, which is at the bottom here, we see both these vertebral arteries coming in, um, they're each gonna give off the pica here, the posterior inferior cerebellar arteries, and then they're gonna go up, they're gonna come together to form the basilar artery. They have many branches that come off, and then it ends by splitting into the two posterior cerebral arteries. And this, uh, set of arteries that are supplied by the vertebrals, um, supply the brain stem, the cerebellum, the occipital lobes, parts of the temporal lobes, and the thalammi, which we can see in these figures over to the left. Um, so any stroke in that area is what we refer to as a posterior circulation stroke, um, meaning that it is supplied by the vertebral arteries. Um, so the importance of, so getting back to that redundant length of the vertebral artery, the importance of it is that it allows us to turn our heads. And the reason as humans that we need to turn our heads is because of the importance of our visual tracking system. So our visual tracking system allows us to track moving objects for both offensive targeting of prey, as well as as well as defensive management of threats, um, and it allows us to coordinate complex actions that require vestibular integration, so stuff like navigation. However, the human gaze only moves about 40 degrees laterally in either direction, so in order to be able to see beyond that range, we have to be able to turn our heads. Um, and so that's why we have that redundancy in our vertebral arteries. The majority of that head movement is going to occur as the ring of C1 rotates on C2, which is shown in this. Illustration here. So there's C1 on top. And it rotates on C2. And remember that redundant length was sitting on top of C1, and you can see here, um, in this figure to the left, this is, we're looking straight on at someone, and their head is turned to their left, and you can see that this right vertebral artery is gonna stretch between C1 and C2 when they turn to the left. Um, and so in people with normal anatomy, this redundancy protects our vertebral arteries from being overly stressed or from dissecting every time we turn our heads. However, there are anatomic abnormalities that can make it so that there's undue stress or impingement on these arteries when we turn our heads, which is what we refer to as bow hunter syndrome. Um, so in adults, bowhunter syndrome often occurs to bony anomalies in the lower C spine, below C2, so that's what we call subaxial. Um, and that's usually from age-related changes, so things like arthritic changes. But pediatric bowhunter syndrome almost exclusively occurs above C2. There are two main subtypes, depending on where exactly above C2 this occurs, um, but they both present similarly and that they both typically result in posterior circulation strokes. So the first sub subtype is atlantoaxial. This is when you have a vertebral artery dissection between C2 and C1. Um, and you can see that here. So this is an image of an angiogram, and you can see the vertebral artery coming up here, and then where that arrow points, I'm gonna show you a bigger picture in a minute, but it, it disappears, and we know that we're below C1 because here is that redundant loop that sits on top of C1. And the second type is, um, and that is typically happens because of an abnormal adhesion or an abnormal fixation point. So rather than something physically pressing on the artery, what happens is that there's something that the artery adheres to, and so instead of being able to have free slack between those two, it makes it so that the length of the artery that is available when you turn your head is shorter because it's fixed in, in, in a place that it shouldn't be. Um, and so the second, the second subtype is atlanto occipital. So this is a vertebral artery dissection that occurs at between C1 and the occiput. And when you look here, you can see, and again I'm gonna show you a video in a second, that where that loop is, that's on top of C1 is extremely flat. And this can also happen because of abnormal adhesion adhesion points, but this is more likely than atlantoaxial to happen because of something physically pressing on the artery, often something that's attached to the occiput itself. Um, so this is again that same picture from Atlanto axial, where you can see that, and this is a video from an angiogram, and if you can watch, just try to keep an eye on that same spot. You can see, um, Is it playing? Sorry. Or maybe we won't see. OK, oh no, it froze. Mm, OK, sorry. I'll try to get this working again. Are the slides moving for anyone? Is it just my screen is frozen, or is it actually frozen? Uh, no, the slides are not moving. OK dokey. Um, all right, um. Let me try reopening it, I guess. They're there, they're moving now. OK. OK. Um, Just gonna reopen it real quick. Sorry, it closed my um presenter mode for it. So I'm just gonna reopen it real quick so I can get back to my notes. OK, hopefully it'll work now. OK, well, the video is not working, sorry, um, but what you would see is that, um, in this patient with Atlantoaxial bow hunters, um, as the patient's head is turned to the left, you end up with this flattening of the right vertebral artery. Um, and then this is a patient with Atlanta occipital bow hunters, and this is characterized by a vertebral artery dissection distal to that C1 frame and transversarium, um. And in this, see if this one will play. There we go. So for this patient, you can see as they turn their head to the right, that flattens and disappears. Um, so this is most common in bow hunters. This is gonna be from contralateral head rotation, but less commonly in some cases, especially with the lento occipital, you can see it with ips lateral lateral flexion or with extension. Um, so what are the things that are actually causing this abnormal impingement or abnormal adhesion point? Um, in pediatric bow hunters, it's typically either a congenital osseous anomaly, meaning a piece of bone that shouldn't be there, but is, or a soft tissue anomaly. So the soft tissue anomalies can be things like syneakia, which are adhesions or bands of scar tissue, fibrous tissue bands, so those can be fascial bands from paravertebral muscles, hypertrophic. Ligaments, tendon and tendinous muscle attachments for the deep neck muscles, or from ligamentous laxity. So rather than it being from something that shouldn't be there, it's from you being able to rotate too far and the bones being able to rotate relative to each other too far. And so you're just moving past where um you have enough slack to move. So in this first class, the osseous anomalies, there are several common osseous anomalies that come up in bow hunters. The most common is what's called either a ponticulus postulus ponticulus posticus or congenital arcuate foramen. So, um, the, the groove that the vertebral artery travels in on top of C1 typically does not have a roof to it. When it has a roof, that's what's called the ponticulus posticus congenital arcuate foramen. So if you look at this, you can see this. Kind of dim arch. So that's one example, and then on this 3D reconstruction, we see this um partial ponticulus posticus. So this is present in somewhere between 10 and 20% of the general population, but it's typically asymptomatic. However, when we see it in conjunction with an a traumatic vertebral artery dissection in a kid, we get a little bit concerned. Um, the other two common findings in bow hunters are bone spurs. So this can either be on the C1 articular facet, and so you can see if you compare this side here, versus there's no bone here, this is that abnormal bone spur, or it can be an occipital condyle spur. So that's this little dagger thing coming down here, and you can imagine that poking into an artery would not lead to good things. Um, so what are the neck movements that contribute to bow hunters? Like I said, most commonly it's gonna be contralateral rotation, which is just turning your head to one side, so turning your head to the left is gonna cause, uh, it's gonna cause a dissection of the right vertebral artery and vice versa. In Atlanto occipital, particularly, it can be extension. If you imagine, uh, for example, someone has an occipital condyle bone spur, and then they move their head like this, moving the occiput down. That could cause more damage and more pressure on the vertebral artery, and they can also be ipsilateral flexion, so basically putting your ear to your shoulder. However, in some patients, it can be difficult to figure out exactly what the specific movement is. One, because oftentimes we're doing this under anesthesia and we're not necessarily moving their head the way they move their head, but also because you get some obligatory combination of movements. For example, if you try to rotate your head fully to one side, you'll probably notice that you flex your neck a little bit, your chin goes down a little bit, so it can be difficult, difficult to isolate those movements. Um, so how does this end up as a stroke? Well, when you have these movements that put this undue pressure, either stretch or compression on the artery, you damage the artery. And so that artery is gonna form, um, it's gonna have a dissection, and so you can see in this illustration, um, the dissection is also often gonna cause a false lumen and it can cause clot formation. Those clots then turn into emboli and they travel up into the posterior circulation, and they can then cause Um, they can then cause strokes anywhere in this posterior circulation that we talked about earlier. So this is an example of an embolic appearing stroke in the right cerebellum of a patient. But you can see here, if this clot comes up this vertebral artery, it can go anywhere throughout this entire distribution. So oftentimes these patients will actually come in with multifocal infarcts. They'll be bilateral, um, but they'll, they will all be within the posterior circulation. So what is the clinical story with these patients? The common presentation differs a little bit by age, but typically it's because of an activity that involves either the far end of the physiologic range of motion of movement, sorry, or super physiologic movements. It's typically gonna be between ages of about 2 and 16, with a mean around 9 or 10 years, but we also see this in kids less than 1 year of age. So in infants and young kids, it often presents as a wake up stroke. So you remember how heavy kids' heads are at that age? Sometimes these kids, especially if they have these anomalies, they fall asleep and their head just suddenly flops all the way to one side. Um, so this loss of mild muscle tone can cause that abrupt movement to one side, which can cause the a dissection, or it can just be from their head staying to one side so long that they develop stasis in the vertebral artery and don't actually have a dissection. It's a stasis itself just causes clot formation. Um, in older kids, it's typically activity related, and it's often pretty normal activities, but it's activities that involve exaggerated head rotation. So it's gonna be things like golfing, baseball, wrestling, especially. I think two of the four most recent cases that we've seen at PCH have been teenagers wrestling, and, and golfing and, and baseball are fairly You know, are pretty much within the physiologic range, but as you can imagine with teens wrestling, when you're getting pinned, that's super physiologic range. Someone is forcing your head into super physiologic rotation. Um, some other things that we see, archery, which is the namesake of this condition, swimming when you're moving your head to the side to breathe, um, raves, roller coasters, chiropractic manipulation has always been famous in neurology for causing posterior circulation strokes, and then oddly enough, picking things up from under a desk. So when you're reaching under a desk and, you know, there's not room for your head to go under and you turn your head really far to one side, that can cause it as well. Um, some of the other things that we've seen clinically is that it has a huge male predominance. So I'm gonna go into the case studies a little bit more later, but the largest case series for for pediatric bow hunters range from 88 to 100% male, and nobody's really been able to suss out exactly why this is. So some of the early thoughts are, could it be because boys do more high risk activity than girls? I mean, maybe if this were something that we saw primarily in tackle football, but, you know, swimming, golf. Softball, you know, those are all, those are all activities that there is a large participation of girls in, and so that doesn't, that doesn't really make sense as an explanation. And another thought is, could it be due to hormonal differences? Um, but estrogen, which is of course higher in girls, is gonna give you ligamentous laxity, which is a risk factor for bow hunters. So if anything, that would explain why it would be higher in girls. Um, and then one of them that is not, that has not been disproven is could it be due to anatomical C-spine differences. So there have been multiple studies that have looked at the size of C spines in boys versus girls and have shown that boys have larger C spines than girls, and the, the evolutionary reason for this is cause it allows them to tolerate more axial loading forces, meaning more pressure coming downwards, but this could also lead to increased traction. Um, there have been questions about if maybe boys just have more of these bony anomalies and the risk in the, the physio the physical differences that cause bow hunters, but there have been several population studies looking at how common things like congenital arcuate foramen are, and the, the, the results have varied. Some studies find it more common in girls, some studies find it more common in boys, but there is not a clear predilection for this being much more common in boys, the arcuate foramen. And then what else do we see anecdotally? So anecdotally, children who develop bow hunters often have a reported history of cracking their neck, um, of torticollis or of what we call turtlenecking posture, and then may or may not have a history of chiropractic manipulation. They also often have a history of ligamentous laxity in in some capacity, so either their families talk about them being hypermobile in some way, double jointed or something along those lines, and it's not clear exactly why. Um, why these specific factors are related to Bow Hunter syndrome. So, you get a kid who comes in, you suspect a posterior circulation stroke, what are your first steps gonna be? With any kid with suspected posterior circulation stroke or any stroke, you're gonna get a brain MRI, making sure you include DWI, and then if it's posterior circulation, you want to make sure that you're getting vessel imaging. Typically our first vessel imaging is going to be an MRA because at least at PCH that's part of our stroke protocol, but we need to make sure that we get an MRA that includes the neck as well. Um, if a posterior circulation stroke is found on that initial imaging, you have to get neck vessel imaging. So like I said, this will often be an MRA, but given the sensitivity of the lower sensitivity of MRA compared to CTA, um, we typically, we often hear we'll just go straight to a CTA of the neck because if the MRA is negative, we're gonna want it anyway, and also because if we see a dissection, we're gonna want to get one of those reconstructions to look for bony anomalies or causes for the dissection. Um, and as far as localizing the stroke, like we talked about, the both vertebral arteries come up to form the basilar, and then most of our circulation is gonna come off the basilar. So, you know, a left thalamus stroke versus a right thalamus stroke really doesn't tell us where the problem is if it's the vertebral arteries. But if they have a normal structure of their pika related to the vertebral arteries, so the left pika comes off the left vert, right pika comes off the right vert, um, then a stroke in that part of the cerebellum can be localizing and lateral medullary infarcts are always localizing for the for the vertebral artery. So once we have the CTA, we want to get this bony reconstruction, and the reason is to look for things like congenital arcuate foramens. And so you can see on this example we looked at earlier, they have this partial congenital arcuate foramen that is right up against the vertebral artery. Um, and then acutely, we may or may not get a catheter directed digital subtraction angiogram, and the reason is because if we already know that someone has a dissection, we found it on CTA, typically in the acute period, that's not gonna add any information. However, if we're getting MRA CTAs, we don't see a dissection, and especially if someone has a recurrent or multifocal posterior circulation strokes, we really need to get a DSA so that we can see if there's a dissection because that's the gold standard. And then our initial management. So we have a patient had we have confirmed posterior circulation stroke, may or may not have confirmed vertebral artery dissection yet, but we're suspecting bow hunters. We're gonna give them an antithrombotic agent of some kind, whether they go on aspirin or Lovenox is really gonna be an interdisciplinary discussion between uh the PICU and neurocritical care and hematology. Um, and they certainly are candidates for TPA if they're in the window, but, um, as far as like bow hunter specific stuff, we're gonna do some type of antithrombotic. We're gonna do a C-spine immobilization, so we put all of these kids in a hard C collar, and then neuroprotective measures, so just your typical post-stroke measures. We want to keep blood pressure, um, normal, we want to keep sodium normal if they're intubated, we want to do. Normal carbon dioxide, just all your typical neuroprotective measures. And then for severe strokes, sometimes they need CSF drainage, um, plus or minus a craniectomy. OK, so we've gotten through this acute period, the kids stable. We think maybe this is bow hunters, so what are we going to do to definitively diagnose bow hunters? Um, the first step is gonna be, or sorry, so we are going to get vascular imaging with dynamic head positioning challenges. So what that means is we want to obtain the images that I showed you earlier, where we're watching an artery and we see when someone moves their head in different directions, do we get, does the flow through that artery significantly decrease or stop? The key with this is that it has to wait until the dissection heals, because of course what we really don't want to do is do this movement and cause them to have cause them to throw more clots or worsen an existing dissection. So typically what we do here is we get a repeat CTA 3 months after the stroke. If the dissection is healed, great, we can go ahead and do dynamic head turn imaging. Excuse me. If it's not, then we get another CTA 3 months later. As long as that's stable, the 2-3 months apart, then we consider it safe to be doing, um, diagnostic imaging. And during that entire workup period, the, the children are on antithrombiotics and they're in hard sea colors. So there are different approaches to the vascular imaging with the provocative head maneuvers. One is an ultrasound. So this is a Doppler ultrasound, so you have the patient sitting straight up, you have the Doppler at the base of their skull, um, on the back, uh, to look at the vertebral arteries, and then you're gonna watch as they turn their head, does that Doppler flow decrease or disappear. So this is helpful because it's noninvasive, it's quick, there's essentially zero risk to it other than if somebody, again, if you don't have a healed vertebral artery, could you cause them to um worsen that dissection. Um, and one of the nice things about it is for Atlantic occipital bow hunters, we think that there's probably some significant axial loading effect, meaning Meaning you're more likely to see that pathology when the patient is sitting straight up and they have the pressure of the weight of their head on their neck. Whereas for things like an angiogram, they have to be laying flat and so you get rid of that axial loading pressure. And so sometimes you may have a positive ultrasound and a negative angiogram in those kids. Um, but the downside of it is that it lacks anatomical detail. You see that the flow stops, but you don't necessarily see where the flow stopping occurs, as opposed to an angiogram when you can actually watch the artery narrow. Um, so the gold standard for this is a catheter directed angiogram. So, um, this is head manipulation under typically under general anesthesia, uh, and you do continuous imaging of the vertebral artery. So you're gonna do continuous imaging in a neutral position and then you go through the other positions. You do rotation, contralateral first, do extension, lateral flexion. And this is with a child's head being manipulated by a member of the team, and then you monitor the flow and you stop when there's a significant reduction. So you don't necessarily want to keep going and see how bad does it get when we get to the maximum term, because again, we don't want to be inducing dissections with this. So the ideal situation with this in in older kids is that they're awake and that they're moving their heads themselves, so we can see what happens when they move to their physiologic range, but of course in younger children it's often not possible. Um, so once we've done that workup, we've confirmed that they have bow hunters. The question is what to do about it and do we need to do anything about it? Uh, so in a case series of, or sorry, um, in the adult literature, they tried just doing long term voluntary movement restriction with a sea collar and seeing what happens, and about 50% of those patients still had continued symptoms. And then in pediatric literature, which is a lot less substantial than the adult literature, about 80% of kids had a recurrence when they were put on antithrombotics alone, so they were only put on Lovenox and aspirin. Um, So, it doesn't appear that conservative management necessarily uh prevents recurrence in in most of these kids. So there are a lot of different treatment options. I'm gonna go over the treatment options that we have and the pluses and minuses of them. So the first is therapeutic vertebral artery occlusion. Um, so this is when somebody goes in endovascularly and they, they place something to basically block off the affected vertebral artery. So this has the obvious downside of making the patient completely reliant on their contralateral vertebral artery. The biggest problem with this is that somewhere around 1/3 of patients with bow hunters in the pediatric population actually have bilateral disease, so they may only have one dissection, but then when we do rotational head turning tests, we see that regardless of which way we turn, one of their vertebral arteries, um, gets. It's uh is affected. Um, so this can either be from bilateral bony anomalies, for example, we've had kids with bilateral congenital arcuate foramina, um. But it can also be due, and you know, that's something that we should we probably could know without head turning, at least if the foramina are there, but a lot of these kids, their problems are due to soft tissue elements, and those are often only found if you do the diagnostic DSA because we can't really see them on imaging a lot of the time. Um, so there are some cases where this may be preferable. Uh, one of the case series that I, that I was reading was saying they had a child who had an expanding pseudoaneurysm, um, and so that they did a vertebral artery occlusion for this, and so for expanding pseudoaneury aneurysms or dissections that aren't healing and are continuing to cause strokes, this is sometimes reached for. And if Doctor Bruzo or or any of the neurosurgeons on have other thoughts I'd be, I would love to hear those as well. Um, another option is endovascular stenting. So this is rarely used. I think in general, endovascular stenting is not typically recommended anymore for mobile arteries. So even in the adult population when we're thinking about things like atherosclerotic disease, while carotid artery stents are very common, vertebral artery stents are not really recommended anymore. Um, and what this is, is something like this stent here on the right is placed inside the artery to stent it open and to also ideally give it structural integrity, so that if it's being stretched, if it's being compressed, there's something kind of backing it up. Um, the problem with this is that you still haven't fixed the source of the stress on the vertebral artery, and just like the artery can be affected, the stent can too. And so this image to the left of the stent image is, um, radio is a radiographic image of a broken stent, and so that is obviously going to cause more problems because now you have a stent that is impacting the artery and it can cause all of the same problems that you were trying to avoid to begin with. Um, another option, uh, one of the more widely used options is vertebral artery decompression and transposition. So this is if we have a source, so if we have a congenital arcuate foramen, if we have an occipital bone spur, we add, uh, remove that osseous structure, or oftentimes it's a soft tissue structure that's seen once the neurosurgeons open up the back of the neck. Um, and so this is typically done just by removing the, um, the structure that's causing the problem. Excuse me. Um, and while some authors have reported excellent outcomes with vertebral artery decompression and transposition alone, other studies have reported high stroke recurrence rate due to residual vertebral artery adhesions or new adhesions. Um, the other problem that you can run into with this is, again, about 1/3 of patients have bilateral bow hunters, and a lot of those kids, it's not diagnosed until you do the diagnostic angiogram. And so if this treatment is done without a diagnostic angiogram or they had unrecognized contralateral bow hunters, then this is not going to fix the the problem on the other side. Um, the other common treatment is a C1C2 fusion. So this likely has the lowest recurrence rate, or sorry, this, so this is a surgical fusion of C1 to C2. So you can see this is we're looking at someone from the side here, there's C1, there's C2, and there you can see the screws into it and this plate that holds them together. Um, so the idea for this is that, you know, like I showed you earlier, C1 rotates on C2, and that is what causes at least the atlantoaxial subtype of pediatric bow hunters. So if we decrease or stop that rotation, then we should decrease the pathology that's causing um the stress in the vertebral artery. Uh, so this has likely has the lowest recurrence rate, and it also treats bilateral disease, right? It's, it's, it's preventing you from moving in either direction, not just one direction. Um, however, some of the questions are if you have Atlantic occipital bow hunters, is this going to help? So maybe if it decreases your head rotation. But again, we have to think about, are there other movements in Atlanto occipital. So for example, is extension the cause of the impingement on the vertebral artery in in Atlanto occipital, and if we're getting, if we're only doing testing with someone lying down, can we really know for sure whether or not extension is a problematic movement for them because that's really hard to test when somebody is lying on their back. Um, It it has, it's, it's morbidity is not really bad overall, so there are certainly concerns about it causing morbidity, but in like the largest case study we have and in patients we've had it at at PCH also, most patients and their families don't actually report a significant change in their range of motion, so that can be seen as both a plus and a minus, right? So it's better for morbidity because it means we're not stopping them from being able to see around them. Um, but also, if we're not having a significant change in their range of motion, are we actually treating the underlying pathology? So I think probably it, it changes the extremes of motion, which is good, so it probably keeps them just shy of being able to move far enough to hurt their vertebral arteries. Um, and then some people have concerns about how putting screws in a young spine is gonna change the growth and development of the spine. Um, and then again, like I said, you know, there's this question of does it help Atlanto occipital at all. So, um, some patients are still gonna have the problems with extension. Theoretically, if someone with lanto occipital, when you do the DSA you're seeing that rotation is what's causing impingement, theoretically it could. Um, but, Unfortunately, our experience here has shown that it, it, in most, in many cases does not help with Atlanto occipital. I think that the, the exception to like when you maybe think about it, is that you can't find any target to go after. You know, they don't have an occipital bone spur, and there's nothing else that you can find to say yes, this is what we're gonna address. Um, the other option for Atlanto occipital is occipital, sorry, occipital cervical fusion, so fusing the occiput to this C-spine. Um, so this of course would address Atlanto occipital type. There's a very low recurrence rate with it, however, it has a very high morbidity because it is a very significant effect on head rotation, which, as you can imagine, if, you know, a kid as they grow up wants to do things like drive, they want to continue playing sports, um, it can really have a significant impact on their quality of life. Sorry, excuse me. So, um, Wonder what Bowhunters is. Um, what the treatment options are, but unfortunately there, we really don't have a, a whole lot of data saying exactly for a given patient what the, what the best treatment option is gonna be. So a lot of the time it comes down to, um, you know, trusting our neurosurgery colleagues and their experience, but there are a couple of nice case series, um, that have been published. So the first significant case series is, um, Is this, uh, this case series of 7 boys with V3 vertebral artery dissections in Dallas. So 2 of these boys had bilateral, so they had not, there were 9 dissections total, 6 of the 9 of them. Um, 6 of the 9 dissections were DSA positive, meaning when they did the, the head positional maneuvers, they saw that in the area of the prior dissection there was decreased flow. And the two boys who had negative DSAs both ended up having a recurrence of symptoms, so they both presented 4 months after their original presentations with TIA symptoms, and they were found to have new or worsening dissections. Um, so this group did provocative head turning DSA as a diagnostic method for bow hunters. Um, they initially put all the kids on anticoagulation and placed in hard sea collars, and then eventually and um one of 5 of the seven eventually got C1C2 fusions, which is their what they typically do with their center. Um, one of them had a unilateral anterior decompression of the C2 transverse foramen that did not. Um, that did not solve their or did not. Heal their bow hunters mechanics on DSA, so they then ended up undergoing fusion, um, and then the other two children, so 5 out of 7 underwent the fusion. The other two, were still awaiting fusion at the time of publication, so they still chose fusion for in the end, all 7 of those patients, I think just not enough time had passed for them to heal for the other 2. Um, one thing that was really interesting in this patient population and very different from our patient population here, is that not a single patient was noted to have anatomic anomalies, so osseous anomalies to explain the cause of their bow hunters when they did CT scans on this patient. Um, And this is surprising given that other case series have had a relatively high prevalence of bony anomalies in patients with bow hunters, and in our experience so far at PCH, almost every patient that we've worked out for bow hunters has had a bony anomaly. Um, it's less surprising they didn't see soft tissue anomalies. Most of the, most of the case series that talk about soft tissue anomalies, they talk about the patient or the, the neurosurgeons find the soft tissue anomalies after opening up the patients rather than something that they're finding on imaging. And in this paper, they, they only discussed what was seen on imaging, they didn't discuss what was seen in surgery, and because the main purpose of this paper was a methods paper to talk about the provocative head turning DSA, they also published it pretty soon after these surgeries, and they didn't really have outcome data to talk about. Um, however, the same group later published a paper with 11 patients who underwent fusion, um, and they, they described no recurrent strokes in any of those patients, the mean follow-up of 33 months. So they do have outcome data a little bit later and it, it does look pretty promising. Um, the other notable case series that I wanted to talk about was out of UCSF. So this was 10 boys with posterior circulation strokes and V3 vertebular arteropathy with all with adjacent cervical pathology. So this was a little bit of a different approach because they in this series, they only talked about patients where they had an anatomical reason for bow hunters. Um, So for two of those kids, they had bony anomalies, so they had congenital arcuate foramen in one and then in us oh don't, I'm gonna say this wrong, odontoidium with cervical instability in the other, which basically just means there's like a little free floating piece of bone. Um, And, and the other 8 boys all had positive DSAs with head turn. So 6 of them were treated with decompression, and all of them had all of those 6 had soft tissue abnormalities that were visualized during surgery, and then 1 underwent an endovascular stent, so that was the patient who was having the worsening pseudoaneurysm I mentioned earlier, plus spinal fusion, or sorry, no, 1 underwent endovascular stent and spinal fusion, the other one underwent endovascular occlusion, and that was the That was the kid who um had the worsening pseudoaneurysm, and they reported that not a single one of their, a single kid in their series had a recurrent stroke, um. With a median follow-up of 58 months. And I think one thing that's really important for this series, so they had, um, they were talking about most of these boys, so two of the boys never had any recurrence after the first stroke, and so they just, they just had aspirin and C-spine and aspirin and a C collar, um, and never needed surgery, but, um, I think that that's important to talk about the recurrence rate for this because Posterior circulation strokes have a significantly higher recurrence rate than anterior circulation strokes. So one study that looked at pediatric strokes quoted approximately 20% recurrence of posterior circulation compared to about 4% in anterior circulation. Um, and with the posterior circulation strokes, the recurrence typically happened within about two months. It wasn't a long period between strokes. I think this is probably due to the difference in etiology from them, so posterior circulation strokes are most often due to vertebral artery dissections, um, and I would propose that probably most of those are from bow hunters and likely it's just not worked up at a lot of centers, um, whereas anterior circulation strokes are most often cardiogenic, which we of course see a lot in the kids in the CVICU. Um, and then the tie for 2nd place is FCAs, which can be recurrent, but are oftentimes a single episode and indeterminate. So we see that a lot, and we know that strokes where we never find a cause have the best rate of recurrence, lowest rate of recurrence. So I think that's just an interesting thing to think about, you know, as neurologists, we often think about if we don't find a reason for a stroke, you know, we do aspirin, we do anticoagulation and we tell the family, you know, if we don't find a reason that's good, it means there's decreased risk of recurrence, but how many of these posterior circulation strokes at centers are just, you know, they get an MRA of the neck, they don't see a dissection, don't get more detailed imaging, and so they have recurrence because this, um, the, the, they have bow hunters and it's just not discovered. Um, so, you know, that's one case series from a center that errors towards decompression, and then one from a center that errs towards fusion. Um, that same group in Dallas who put out the first paper I discussed, they're the ones who, who really go towards fusion. They put out a pro a prospective paper discussing their treatment algorithm for suspected bow hunters. So if someone has a V3 segment dissection, they are put in a sea collar, or anticoagulation. They get a 3 month follow-up MRA. If the dissection is, is, uh, is not healed, they continue the anticoagulation and the C collar and then repeat the MRA in 3 months. If it is healed, they do a DSA with rotational head maneuvers, and they look for dynamic compression. If they don't have it, they just put them on aspirin and keep an eye on them. If they do have it, they get a posterior C1C2 fusion. Um, And so this is similar to what we do here, but I would say the biggest difference, and this is of course comes mainly after our discussion with our neurosurgery colleagues, is that we have a little bit of a different decision tree later down the road. So, if they have dynamic compression, then we say do they have a target for decompression. If they have a target, then we'll often do decompression, and if they don't have a target, we'll often do a posterior effusion. Um, in a target for decompression, I mean, can we find something like a congenital arc of ramen or another osseous abnormality, or is there a ligament that's pressing on it, something that we can take away surgically that we think will relieve the abnormal, um, pathophysiology occurring. So the asterisk to this is that if it's atlanto occipital, Um, and they don't have a target, then there's a lot more of a conversation about, um, whether a fusion is going to be helpful because again if we do a C1 C2 fusion, we don't necessarily have a lot of Have as much success with that for Atlanto occipital, but an occipital cervical fusion is going to have a much higher morbidity rate for those patients. So what have we seen here? Um, so we've had 16 patients over the last few years that we've evaluated for bow hunters, um, and it's hard to say exactly how widespread the sample is because these are essentially patients that Doctor Brizzo has been called about, right? And so if they come through and they, they don't necessarily get that workup, you know, do, do we have enough data on them and know about them to be including them in our data set, um. But for these patients of the 1613 of them had vertebral artery dissection. Um, and then 4 of them, 4 of those 13 underwent testing and had positive results, meaning they, uh, when their head was turned, we saw a decrease in the flow for one of the arteries. Only 1 had negative testing, but I think one important thing about that is that this kid's testing was several years after his dissection, so he could have just, um, grown and could have changed for that reason, and then, um, Uh, 8 of these kids didn't undergo testing, so 4 of them are because those strokes happened within the last 4 months and they just haven't had the stable CTAs to undergo testing yet. Um, 1 unfortunately died a couple of days after presentation. One was just treated without testing. This was a patient who had a bony overgrowth condition and it was a pretty slam dunk diagnosis, and so she underwent fusion, um, very couple days after presenting with her stroke. Um, and then one was lost to follow up and one patient's parents declined any further testing. Um, so just looking a little closer at the patients who had positive rotational testing with us. Um, the first is the patient that we discussed at the beginning of of the talk. So he had a right congenital arcuate foramen causing atlanto occipital bill hunters. Um, the congenital arcuate fraen was removed in a decompression, and then on a follow-up angiogram, he still had those positive mechanics, underwent a C1C2 fusion with good results and no recurrence. So this is an example of a kid who had lento occipital but did well with the C1-C2 fusion. Um, and then patient five in our series had a right congenital arcuate Freeman also causing Atlanto occipital, when, uh, underwent a C1 to C2/3 because he had a congenital C2C3 fusion, um, posterior fusion, and then he had a large recurrent stroke 15 months later. Um, notably, this was during a weightlifting session, and so likely when he was lifting weights and, you know, this was a very athletic kid probably lifting heavy weights, he likely extended his head during that. Um, also, neither he nor his parents really notice a significant change in his neck rotation after the surgery, which is reported in a lot of patients. Um, so he started wearing a sea collar again, restarted anticoagulation that was then converted to aspirin, and he declined surgical intervention. Instead, he just does voluntary activity restriction and has no had no farther strokes with that. Um, And so that first patient had Atlanto occipital did well with the C1C2 fusion. Second patient Atlanto occipital did, you know, had a large recurrent stroke with the C1C2 fusion. So that shows this difference in outcomes for Atlanto occipital subtype with those fusions. Um, and then patient six had a unilateral atlantoaxial bow hunters, um, due to an anomalous hypertrophic osteophyte on the left C1 inferior articular facet, so he had extra bone on the bottom of C1. So he underwent a decompression, um. And his bow hunter mechanics were relieved on ultrasound, but then on follow-up DCA DSA, sorry, he had a new vertebral artery dissection with intimal flap. However, he's had no recurrent strokes, has not had any further surgical interventions, and he's still undergoing CTAs and is being monitored by Doctor Abruzzo. Um, and then our 7th patient, this was a left atlanto occipital bow hunters with left occipital condyle osteophytes, so one of those kind of sharp tooth of bones coming off the bottom of the skull pressing down the vertebral artery. So he underwent a decompression and occipital condyle resection. Follow-up ultrasound and angiogram showed resolution of the pathology, but unfortunately he, he then needed an occiput to see C3 fusion for newly found atlantoaxial subluxation. So overall of the patients here with suspected bow hunters, we've had a wide range of presentations and variable outcomes, um, but like I said, we had 4 new patients in the last few months and 3 of them had clear in sighting events, and they all have osseous anomalies, so I'm interested to see where their courses will lead. Um, so in conclusion, you know, posterior circulation, stroke in childhood, always think about vertebral artery dissection. You have to get neck imaging, ideally a CTA. If a vertebral artery dissection is found, you should strongly consider bow hunters. Acutely, this means C-spine immobilization, antithrombotic treatments, um, and then you should have, then you need to seek definitive diagnosis once a vertebral artery dissection is healed, and the typical, the most common definitive treatment options are going to be vertebral artery decompression or spinal fusion. Um, these are my sources. Um, thank you so to Doctor Abruzzo for, for teaching me a lot about this and for, um, giving me some slides, and then to all everyone who takes care of these patients, our NCC team, PICU, he, neurosurgery, and everybody else. Um, I'd be happy to hear any thoughts or questions. That was uh fantastic, Jack. I really appreciated that. That was a comprehensive and uh very insightful overview of a complicated Uh, condition that we're really just beginning to understand. I, I really thought that was a great, uh, presentation. What, you asked, um, during your presentation, uh, uh, I didn't want to interrupt you. I waited till the end about vertebral artery occlusion in patients with persistent, uh, Uh, dissections, non-healing dissections. You said pseudoaneurysm, but I mean, pseudoaneurysm is just one example of a non-healing vertebral artery dissection, and I think in this population, we can see that because there's a really high degree of non-compliance, right? These are fanatic fanatical athletes and in our experience anyway, they will absolutely resist any Uh, restrictions on activity. And um that's, uh, we've seen recurrent dissections usually, um, but in the same way that we see recurrent dissections from non-compliance, I also can imagine that we would see non-healing dissections and persistent and growing, uh, lesions. And, and in, in that scenario, you know, um, You, you basically have no choice except to do a deconstructive procedure and, and sacrifice the vertebral artery. It's a suboptimal choice, of course, um, but, um, it's, it's it's sometimes, I shouldn't say often, it sometimes is the only choice, right, um, in that patient, um, but it does set them up for injury to the contralateral vertebral artery in the short term and in the long term, what we always worry about when we take down Uh, permanently sacrifice the cervical cerebral artery is that their lifelong risk of developing atherosclerotic vascular disease as they grow older and in the contralateral normal artery, and then they don't have the collateral reserve from the other artery, it sort of puts them in a very uh disadvantageous position uh to face uh the rest of their life with that. Um, but sometimes we have to do it, so. Um, I'll leave it at that, but thanks, thanks for your excellent presentation. Thanks, Doctor Brizzo. Um, and, and if, if any of the neurosurgeons have any input, Doctor Ronicer or anybody else, um, about how you, if you guys approach these patients any differently than the way I described, you know, I'd be happy to, happy to hear that. No, that was a great talk, and I would just maybe add that it's hard to make conclusions, even though we have a pretty large collection of patients. I do think it's hard to make many um conclusions from the experience that we've had so far. Yeah, thank you, Doctor Anne Kurt. Yeah, one other thing I forgot to say is that it's, it's also Hard to say because, you know, the Dallas and UCSF centers take very different approaches, but how much of their success is based on that's the approach that their neurosurgeons are comfortable with and have a lot of experience in. So, you know, if they traded approaches one day with their outcomes change, um, and we are currently trying to put together a multi-center, um, case series to hopefully have some larger numbers to look at and, um, hopefully some, some better outcome data. Nice job, Jack. Really nice sweeping review of what we know and don't know. The only, you know, sort of thought I have, and Todd's heard me mention this a couple of times, is the epidemiology of this disease. Because it seems like we just have so much of it here in Arizona, where I, I can't say I saw more than 1 or 2 cases ever in the years I spent up in Washington. We just think that we're More sensitized to it, we're more thoughtful about diagnosing it, we're more aggressive about treating it. We know more about the disease now than maybe we did a decade ago, you know, what are your thoughts? I'm sorry if I was asked before. I was, I'm in the operating room, but I caught the tail end. No, you're fine. I didn't talk about that. So, but, um, one of the papers from Dallas talked about that a little bit because unsurprisingly with their um with their just like population makeup, the majority of their patients were Hispanic. Um, I talked a little bit about, about like we don't really know why boys are significantly more affected other than maybe the the anatomical differences and just the size of their C spine. Um, but Dallas talked about how the majority of their patients were Hispanic, which is not surprising with their patient population, you know, we obviously have a very large Hispanic population, um, in Phoenix as well, um, and, you know, I obviously have much less time in practice than you have, but yeah, at Hopkins, I never saw a single case of bow hunters in my 3 years in a row there, um, and we've now had 4 in the last 4 months here, which I think is an anomaly, but, um, definitely a big difference, so, um. Yeah, I'm not sure. I, I, I'm trying to think, you know, what percentage of the kids that we've seen here have been. Hispanic, I don't know if, you know, it would be interesting to look at, is it very few, very few. Let me ask the question a different way, um, Jack and Todd, maybe you can join in. What is the incidence of MRI findings that would be considered risk factors for bow hunters and kids unaffected by bow hunters? What I mean is, how often do we see a condyle or bone spur. Or uh what what I like to refer to as a bone order conflict. In normal MRIs, normal CT scans, like by, in other words, I'm sorry, I mean like MRIs and CTs done for kids who are clinically asymptomatic. So congenital arcuate foramen is like 10 to 20% of the population. Um, I'm not sure for the other ones. What do you, what's your experience, Todd? So I, I think these are population-based studies that are done on cadavers and, and, in some cases, imaging studies and in the general population, I think that's about, that's about right. Um, and so there's a much higher incidence in, in our patients. Um, I, I don't think we know the answer in, in, in pediatric population. I, I, I couldn't really say that we have data on that. Um, I'm gonna frame the problem a little bit differently though. Um, I think that A lot of our this is posterior circulation stroke that is just misdiagnosed or underdiagnosed. Um, that's the problem, right? And that's why you didn't see it in Hopkins and other people don't see it at their institutions. That's why we have an abundance of cases because We are sensitized to the diagnosis. We're looking for it. Um, if you look at large case series of pediatric non-perinatal pediatric arterial ischemic stroke, posterior circulation stroke is a minority. It's less than 30% of all cases, and most of those cases are due to vertebral artery dissection, uh, non-traumatic vertebral artery dissection. And the remainder of those cases are a wastebasket of, of miscellaneous diagnoses. I think they're mostly missed for tebral artery dissections. Uh, just before I came here, uh, and, and you see why we missed the diagnosis in the first case that Jack presented several times, and, and that's historically been what I saw in Cincinnati as well. Patients don't get cervical vascular imaging, uh, when they come in with posterior circulation strokes. The vascular imaging is inadequate. They've missed the dissection. So there's a large proportion of patients with pediatric posterior circulation stroke who have missed vertebral artery dissections. And then the ones who have recognized vertebral artery dissections just don't get worked up or evaluated. They're just called vertebral artery dissections. And I think that accounts for the differences that we see from center to center. I don't think we're overdiagnosing it. I just think that other people are underdiagnosing it, just missing it. Thoughts on that. I don't know, Jack, any, any last comment? No, I think that's, yeah, I think that's, I, I think one of the other things which I mentioned briefly is that we are, um, Because CTAs have a non-negligible amount of radiation, I think a lot of the time we rely too much, the general we meaning pediatric neurology, not necessarily meaning PCH, um, we get an MRA and if it doesn't show a dissection, we say, OK, great, and don't necessarily, uh, think about the increased sensitivity of a CTA for that. And so my guess is that probably a lot of it is from MRAs that don't catch stuff and either, and they don't get CTAs and then, you know, I think here like you said, we Think about it a lot, and so if they don't have a dissection of CTA, we do an angiogram, which I don't think is something. You know, at other places I've worked, I, I do not think it would ever have gotten to that point. Like we, we got, one of the presentations, sorry, Jack, I know we're running out of time. I just, I wanted to mention this. One of the presentations that a colleague, uh, is giving at the IPSO meeting is sports-related, uh, neurological symptoms like patients who come in, uh, after, you know, playing baseball and they have neck pain and they have these non-specific neurological symptoms. I mean, a lot of those patients don't get the full workup and, and I feel like those patients, again, is another large category of missed vertebral artery dissections and Um, you know, just from minor, uh, sports-related, you know, uh, head turning or, or rotation or, or, uh, you know, baseball practice, um, tennis, these are all sports where patients, you know, can sustain vertebral artery dissections with minor symptoms. And, or just not diagnosed and so I, I, I think it's, it's a heavily underdiagnosed problem. Yeah. Yeah, I think also I think one of the patients that we had here, um, he had just been running, running passing routes, not tackle football, just running and then would turn around to look for the ball to catch it. Which, you know, you don't think of that as being traumatic, you know, we talk about non-traumatic dissections, that's not traumatic, that's just normal, normal kid activity, so. Um, we definitely see it from some fairly minor head movements. Thank you, Jack. That was all wonderful. Very, very nice. We appreciate you. Thank you. Congrats on graduation. Thank you. Congrats.
