Pediatric Hydrocephalus: More than "Big Ventricles"

I want to build up this sort of common context. We talked about the weird stuff that we see, and now I want to talk about the absolute bread and butter of pediatric neurosurgery, because if you learn one thing, this is the thing that you should know about. The one disease that everyone thinks about when they think about pediatric neurosurgery is hydrocephalus. Um, usually I torture the audience a little bit more with some questions. Um, but, uh, I've put up some statements here that are generally true, but have really interesting exceptions. Um, so hydrocephalus is when the fluid that's within the brain builds up too much that often results in increased pressure on the brain. You can think to yourself, you know, there are interesting conditions where maybe the cerebral spinal fluid doesn't actually build up that much, but the pressure still goes up, right? If anyone knows what that is, but that's an interesting disease that's called idiopathic intracranial hypertension. There's not that much fluid, but there's a ton of pressure. It's really vexing for neurosurgeons. There's another condition where you have a lot of fluid, but not so much pressure. You might even say the pressure is normal.

This is the most common form of hydrocephalus. Crazy, but if you believe the hydrocephalus association stats, it's true, called normal pressure hydrocephalus. It predominantly affects aging patients, not kids, but it's something that we always have to think about. And lastly, there's even the inverse of hydrocephalus where there's too little fluid and the pressure is too low, which may be spontaneous or induced by trauma, like this brain fluid is leaking out either through a traumatic injury or through an interaction of the cerebral spinal fluid space, even potentially in the spine with the venous system or with other sacs where it can be bulging out. The most important thing you need to know about hydrocephalus, again, if you forget everything on this slide, it's the second point. Hydrocephalus is a clinical diagnosis. You have to see and understand the patient.

And this is such a crazy thing, which is AI, robots, and lasers, and scans, and blah, right? This is one of the reasons I love neurosurgery. We're the last specialty in some ways that actually lays hands on the patient and actually examines them that needs to see what they're doing to understand what we should do next. I do not think that this is determinable from an image, but we use imaging like CT and MRI scans to understand what's going on with the patient and put it all together. It's tricky to actually come up with a perfect definition of when someone is hydrocephalus before you go to surgery. It's maybe pretty obvious when you put a drain catheter in, either a temporary or permanent catheter into the fluid spaces in the brain, the ventricles, and you find the pressure is high and there's too much fluid. Yeah, Dan, okay, that's obvious. But not every case is so obvious. There are key symptoms to watch for that in the beginning mimic a lot of other conditions of childhood. These are things like headache and somnolence and nausea and vomiting. And you might think about how do I know that in a one-month-old or a three-month-old? That might be tricky. They can't tell me if I have headaches. They're kind of sleepy all the time, 15 hours a day. They throw up all the time and so on and so forth.

There are some objective signs we can use, including doing a good exam of the back of the eye, understanding the tactile physical difference and what a normal soft spot in the front of a baby's head called the anterior fontanelle feels like, and what a normal skull feels like. And we have a variety of treatment options. So this is how you evaluate hydrocephalus. You'll note that, yes, scanning is important, but these are critical clinical points that you have to remember to take a history, to measure the head of yourself to examine the anterior fontanelle yourself by physically touching it and looking in the patient's eyes when they're cooperative and when that's possible. So we talked a little bit about this, right? It's a clinical diagnosis,

Dan. Okay, that's great. It's not imaging. Okay, that's great. Well, I'm going to show you three kids here, right? They all have something different. And now I've just spent all this time telling you it's a clinical diagnosis. So you'd expect me to be able to say, well, which of these kids has hydrocephalus? You can examine them. You can imagine what their exam would be. And you actually can't tell. And this is where it gets really interesting. So if anyone knows, and let's see, who do I, maybe I'll let the audience shout out here. If anyone knows what is the most common cause of a big head? for a kid i'll back up a second what's the most common cause of a tall kid call on allison maybe headaches what's that genetics yeah well when you say genetics specifically because it can be a lot of different things but tall parents right tall parents cause tall kids maybe they feed them well or yeah it's actually highly genetically determined the mid-parental height and all that plus minus two. So most common cause of a big head then, Allison, is? Also parents with big heads? Big heads, yes. So you might want to measure the parents' heads. And it turns out this, you know, cute little kid on the right who looks like he's got this giant noggin. Well, guess what? You talk to him and you say, the parents have really big heads. You know, all my kids have had big heads. And like, well, what's going on there? Well, actually, one of the most common causes of increased real spinal fluid accumulation in It's not fluid inside the brain where it pushes the brain against the skull and is particularly damaging and harmful or even life-threatening. It's fluid accumulating outside the brain. And this is super common.

It's extremely familial, unlike diseases like hydrocephalus, which although they have a genetic component, and that's what you read about in the books, almost every case of hydrocephalus is sporadic or acquired, even if it's potentially genetic. It usually was a de novo mutation. In this case of this benign enlargement, I'll show you examples of this in a minute. Before we go on to the non-benign cases, you'll find that an ultrasound is extremely useful. So this is a crazy point. Because babies have this bone window in the front or top of their head right here, you can actually stick an ultrasound probe on their heads, and you could actually get images that way. And I'll show you some examples. So that's something you can't do in almost any other age group. There's some interesting and specific exceptions to that, including some interesting cranial implants that we don't commonly use, but have this interesting property. In general, those kids do extremely well. In general, they don't need treatment.

So these are some images that show what benign enlargement subarachnoid spaces look. I'll say this is an extreme case, but we're talking about the extremes. So the top image on the left is an ultrasound. So it's the perspective of the ultrasound probe. You have to imagine like someone put an eyeball on the top of someone's head in one 2d plane they're looking down so you'll see the scalp uh and you'll see the fontanelle and there's huge black space that's all fluid um and then the gray is the surface and gyri brain and that huge space it's almost an inch you can like drive a hot wheels truck through it um is all fluid and you can see on the color image for example those red things in that space and on the black and white images which are the mri scans on the bottom left and on the right side. You can see in that white fluid, now it's white on MRI because of specific sequences we acquire in this patient population.

You can see the little snake like things, little black things sort of snaking their way. It looks like they're trying to get from the brain and they're trying so hard to get to the lining of the brain where they have to merge with the venous sinuses to drain the blood out of the brain. Those are blood vessels, usually veins. And what happens in these kids is they can have bleeding into this space sometimes from very minor trauma. So that is something you have to counsel patients about because it is so common and they don't need as much trauma to cause bleeding as other kids do. So it can be an important diagnosis to establish. So this is one of the really common causes of benign enlargement of the head. So let's turn our attention now from all of these nice happy kids on the left to maybe this one on the right that looks a little bit more threatening here. That's quite it. I would be scared to see that kid in my exam room. So we're going to skip the head circumference screening talk here. Just trust me, you should do it because kids with hydrocephalus have very different size heads. It's not rocket science, but it's amazing how often people don't do it. And so we've just said that these kids have a lot of pressure, these hydrocephalus kids, right? And one thing that happens when kids have a lot of pressure is their heads grow because they can. They're normally growing. When you put the intracranial contents under pressure, it pushes the bone out.

Bone's a living thing. It's constantly building, getting remodeled, getting removed, going through this life cycle. So as it experiences that pressure, mechanical, chemical, and then even hormonal signaling pathway happens, and it encourages the bone to grow outside where the pressure is coming from. But sometimes we'll see kids with hydrocephalus with severe disease, as this kid has, I'm about to show you, with a completely normal size head. And that's strange. And this is one small point about clinical diagnosis that's really important. I just said it's important to look at the patient and this and this. It's the thing about data interpretation. So this is a kid who was in our newborn ICU, actually in another hospital's newborn ICU for accuracy purposes. We'll say it's in our newborn ICU. They were born at 30 weeks, which is, is that early or late? It's early. It's about 10 weeks early. So three quarters of the way formed, they come out of the womb. And sometimes, although our outcomes in 30 weeks are generally pretty good, and this kid is in good neurologic shape, incidentally, this child has high-grade interventricular hemorrhage. So in the transition from the maternal circulation, where mom is giving you nutrition, blood, oxygen, all that good stuff, through the placental and umbilical environment in the in the fetus um they have to transition to breathing on their own getting their own oxygen um and even changing their circulatory systems because they don't get this massive maternal circulation this has huge effects on the brain um and can cause bleeding and this kind of this kid had that but if you look at their head everything is completely normal um when they come in to see me and yet this kid is you know uh when they come in to see me they're not in this state, but this was the last visit they had that was recorded.

Now that you can see it's an REMR system, um, by somebody else, um, before they came in to see me, they were completely healthy. By the time they come to see me, they're quite sick. So what's going on here? How can you just said this head grows and these kids are growing. It's so easy for their heads to grow through under pressure. This kid's head is normal. Well, this was the ultrasound that I had before, and I'm not going to expect you guys to be experts in ultrasound. So I'll talk you through it again. Probe placed on the top of the head, looking down through the soft spot, you see the gray of the braid and these black fluid spaces inside these fluid spaces are a little bit enlarged but they're not so big as we might see or we might be concerned about this is where they were before when they had that ultrasound taken so if you draw a line this kid looks like they have a rocket ship that line is sort of going up into the right where we like all of our lines in business and finance to go but not in medicine um and they're kind of they come to see me right they are rocketing off the curve um so we get them set up for urgent surgery because their skin now looks like this.

So it's very important whenever you're seeing a piece of medical data of any kind of laboratory value, a physiologic parameter, patient's height, their weight, et cetera, to put it in time context and temporal context to say, what came before and where am I now? And to do that little bit of extra work, I think, is really quite valuable because potentially, had we caught this a little bit earlier, we would have avoided a few trials and tribulations, but this child did well. Well, in the sake of time, I'll just say that there are common examples of how we can treat this condition, and there are two of them. One is the placement of a ventricular shunt. So this is a CSF system that actually has a catheter that goes into the ventricles and the fluid spaces. It goes through the brain, and then it goes into another system that drains it down into another space in the body, very commonly in the belly. It's regulated by a valve that controls how much fluid flows off. This is pretty common, but it's expensive, actually. even though it seems like a simple system. It can cost thousands of dollars to put in and tens of thousands of dollars of operating time. And half of these shunts get clogged up because the little tiny tubes have little tiny holes and protein and other debris accumulate in those holes as they're traveling through the system. So we have another way to do this, which is what's called an endoscopic third ventriculostomy.

So this is a camera-based procedure where we'll actually make a new opening for fluid to flow within the brain without having to use a shunt. So this is a pictorial depiction of what this looks like. We pass the camera carefully through the brain into the center of the brain, into the brain ventricles here. We find this membrane at the floor of the third ventricle here, and we open that up. And so from the surgeon's perspective, I'll walk you through these six images. These are the canonical images of endoscopic third matriculostomy, where the first image is from, again, you're in the top looking down. You're looking at the inside of the ventricles. You can see some CP, some chorid plexus, that pink sort of coral stuff. And then you have another little space in there. That's the third ventricle. So the next image on the right, you travel through there. You identify the floor of the third ventricle. You pay attention to that BA. That BA is, in this case, called the basilar artery. And you really have to watch out for that because it's full of blood, and you want to keep its blood inside it. see the prior conversation about bleeding and endoscopy. And then you want to carefully select where you're going to open this membrane in the tuberous cinerum, the gray potato, which is actually what a little translation is. It's crazy. And you open that membrane, you dilate it up, and you have a nice opening. And now in the bottom right image, you can pass your camera through there in the prepontinent cistern.

And you can see that huge basilar artery there happily pumping away nice and uninjured. And you've now made a way for fluid to drain from the brain around a blockage and inside the brain to a new location where it's better tolerated. So in the interest of time, I'm going to pause there. And I'm happy to answer any questions if folks have about pediatric neurosurgery, neurosurgery in general. But I wanted to cover what is pediatric neurosurgery? What are the crazy things we do? Robots and lasers and spine and brains and electrical activity and all this stuff. And then the really common stuff that I think you're going to see if you're on a pediatric neurosurgery rotation. You're going to have to understand.