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Providing Multidisciplinary Care for Bow Hunter Syndrome

Scott Webb: Welcome to Pediatric Insights, advances and innovations with Children's Health. I'm Scott Webb. And today, we're discussing bow hunter syndrome with Dr. Bruno Braga. He's a pediatric neurosurgeon at Children's Health and an Assistant Professor of Neurological Surgery and Pediatrics at UT Southwestern.

Doctor, I'm eager to have you tell us about advancements in diagnosing bow hunter's, but before we get there, can you provide an explanation about what bow hunter syndrome is and what causes it?

Dr. Bruno Braga: So bow hunter's is when you would turn your head and that causes symptoms like you were having a stroke. So that's most commonly in adults. It happens usually in the vertebral arteries. These are two arteries that go on the side of your neck and supply the back of the brain in contrary to the carotid arteries, which are more famous and that run just in front of the neck, on the side, but in front of the vertebral arteries that supply the front and most of the brain.

So in bow hunter's, if you turn your head to the side, depending how much you turn, you occlude one of the vertebral arteries. But because they join in the middle to form another artery called basilar artery, when you turn your head like if you were normal, nothing happens. But if you have a disease in one of the arteries, because you just close the other one by turning your head, then you have low supply of blood to the brain and that may cause problems. And you would be in the symptoms like you're having a stroke.

Scott Webb: So doctor, what's your process in making a diagnosis?

Dr. Bruno Braga: Yeah. So in children, the clinical picture is a little different. So they don't present with this temporary symptoms when they turn their heads. So they usually present already with symptoms of a stroke. So stroke in the back of the head is different than stroke in the other parts of the brain. So a stroke in the back of the head, they usually cause vertigo, headaches, imbalance, feeling that you think you're going to faint.

If a patient has that, he goes to the hospital and they're going to be worked up for stroke and they usually find a stroke if the patient has the pediatric bow hunter type of syndrome. So once they find this stroke in the back of the brain, then we have to look for the cause of the stroke. And if it is bow hunter, they're going to find some tearing in one of these vertebral arteries. And what we found in our study was that this tearing is typically at the level of the second cervical vertebrae. And that artery of those people who have bow hunter, they usually have this typical configuration with a very acute turning of the vessel. So when the person turns their neck, that turning with time is going to cause wear and tear of the artery, which eventually leads to the tearing to the dissection that causes the stroke.

So once we find the dissection of the vertebral artery, which was the cause for the posterior stroke, then we have to think about bow hunter. There's no diagnosis on bow hunter yet. Then, in these children, we have to do this special kind of tests called a rotational angiogram or dynamic angiogram, where we inject contrast in the groin and check for the blood circulation in the brain and in the neck. And while are we doing that, we turn the patient's head from side to side. So if we turn the head to the side opposite to where he had the dissection and the artery is closed there at the site of the dissection, then that's the diagnosis of bow hunter's.

Scott Webb: Yeah. And you mentioned the study that you did. So I want to have you talk about the research that you've done to provide this innovative care to pediatric patients, who are facing this diagnosis.

Dr. Bruno Braga: This is a very rare syndrome in kids. So, our literature review showed that there were approximately 45 patients, who have had this reported and described. So we started looking into those more carefully. And so now, every patient that we have, that presents to the ED with a symptom of posterior stroke and are found to have a dissection in the vertebral artery at this level of C2, we do this dynamic angiogram.

And with that, we're able to find many more patients than ever with this bow hunter, which we can call as well dynamic compression in vertebral artery dissection because it's a little different than adults. We found 11 patients who had stroke dissection at this specific segment. And then on the dynamic angiogram, they were found to have narrowing of the artery at that specific level, therefore confirming the diagnosis of bow hunter.

So the treatment can be done a few different ways. So, you can put the patient in a collar. In that way, you avoid neck rotation. And, initially, because they just had the stroke, you put them on heparin. You'll give them anticoagulants. But of course, it's not feasible to have active children with a brace in their necks and on anticoagulation for a long time.

So the alternative to that is to do a decompression. So you would remove bone or soft tissue around the artery to avoid the dissection or you would do a fusion, which you put screws between the first and the second vertebrae, which is where most of that rotation occurs. That way, you avoid the internal rotation. It's like you put an internal brace for that movement to no longer happen and then the artery heals and it's no longer compressed by turning off the head. So when these kids turn their heads, they can still turn them, but not at that level. So the vessel, the vertebral artery is not compressed, so it doesn't tear again causing a further stroke.

Scott Webb: Yeah. I have kids and you're so right, picturing my kids having to wear a collar for a long period of time, that's just not going to work, right? So as you say, it's a short term solution, but long-term, you and the team there, you know, have other methods to try. And I want to talk about your team. I know you provide multi-disciplinary care to patients, which does set you apart from other health systems. Can you explain that multidisciplinary care that you offer and how it really makes patient's lives easier?

Dr. Bruno Braga: It always starts in the emergency department. So our emergency physicians, they are the ones who think about the initial diagnosis of stroke when they have these children presenting with the fainting, the imbalance, headache, vomiting or vertigo. So after that, once they ordered the test and think about a stroke, the neurologist is called.

Then, this patient, if he's diagnosed with a stroke, he's going to go to the ICU, so we have the intensive care team helping this child. Then, if the dissection is identified at that level, this patient is going to need that rotational angiogram, which is done by our neuroradiology team. Actually, we have a specialized neurosurgeon who is also a pediatric vascular surgeon, so he does those studies for us. And then, the children to undergo that study, they need special anesthesia, so we have specialized pediatric anesthesia.

And then once the diagnosis is made, then, we, the neurosurgeons together with the radiologist and the neurologist, are going to think about what's the next step in the treatment for this patient, whether or not he's going to need surgery.

We have here at Children's a cerebrovascular center and we meet once monthly and we discuss all these cases. It's good care that these children receive and we know each other and we're always talking and discussing cases in order to provide what we think is the best.

Scott Webb: Yeah. I just love that team approach and really fascinating topic today. Doctor, as we wrap up here today, anything else you want to tell people about bow hunter syndrome?

Dr. Bruno Braga: Since we began doing this dynamic angiogram for these children, we've identified more patients. I think the take home point here is that, if you have a child with posterior stroke and they are found to have a vertebral artery dissection as a cause for the stroke, they need the dynamic angiogram in order to be able to do that diagnosis of bow hunter's.

As I said in the beginning, we reviewed the literature and found 45 cases of bow hunter in children. And about half of them had strokes that recurred because the diagnosis was not made. So those patients did not undergo the dynamic angiogram. So they were treated as having a stroke for no apparent calls. And then, because they were moving their heads still, they had another stroke. Since we began doing this protocol with our patients, we've had no recurrent stroke. And that's very good, because, you know, a secondary stroke can be more serious, even more serious than the first one.

Scott Webb: Yeah. And my takeaway today is really about that dynamic angiogram and how critical that is and what an advancement that is, because as you've explained here today, for all intents and purposes, these patients are going to present and appear to have had a stroke and they did, but really a question of what caused the stroke, so doctor, thanks so much for your time today and you stay well.

Dr. Bruno Braga: Thank you. You too.

Scott Webb: And thank you for tuning into Pediatric Insights. You can find out more information at childrens.com/neurosurgery.