Grand Rounds-Typical and Mysterious Causes for Shunt Malfunction and How to Troubleshoot Them
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- Hello, ladies and gentlemen, and thank you for joining us. This session will be a discussion regarding troubleshooting the shunt. This is a very complex topic. There are lots of dilemmas involved in the management of shunts with a suspicion of an infection or malfunction. Doctor Joel Boaz from Indiana University and Goodman Campbell Brain and Spine, a pediatric neurosurgeon, will be discussing this complex topic. Again, thank you for being with us.
- Thank you very much for asking me to come and talk about troubleshooting the shunt and diagnosing problems with them.
- Thank you, Joel. So, let's go ahead and review the basics and the disclosures, none of which really interfere with the presentation today. One of the main dilemmas that as neurosurgeons on call we run into is the worried mom or the anxious mom who calls in with a suspicion of a shunt malfunction in her young child, with obviously a history of shunt that was placed in a various period of time recently versus in a long past. And we always learned its dilemma, should the child be brought to the emergency room, or this is something that potentially unrelated to the shunt? Would you somewhat start your discussion with some of the details relevant to answer that dilemma?
- I think that taking care of patients with shunts that may live quite some distance from your hospital is always difficult. And ideally, it should be a collaborative effort between the pediatrician or primary care doctor who knows children and their health best, you, who knows hydrocephalus and the shunt, and the parent that knows their own specific child, and none of those expertises are a real substitute for the others. So that by talking to the mother and potentially figuring out how high the suspicion you have for a shunt problem, you avoid excess trips to your emergency room or clinic. On the other hand, if a child is sick, then you know that they can come to see you. Some of the things that I think parents may tell you about that are of concern, certainly headaches, headaches in a child that's old enough to complain are one of the most common problems that would suggest that the shunt is not working the way it should. Vomiting, or lethargy, or other things, any decline in the visual performance, and that could include turning the head to the side, or nystagmus, or not being able to see the board at school, we do not like to see any decline in a child's performance, whether that's school performance, or developmental milestones. Once a child has achieved a given level, we do not permit them to get worse without being concerned. And the last thing that I think parents will oftentimes tell you is that the eyes look different, that something is different about the child's eyes or their appearance. Headaches may be seen in children of all different ages. And one of the most important ways that we can determine whether those headaches are related to high pressure, low pressure, or are unrelated to pressure, is the temporal and positional correlates of the headaches. In other words, what time of day and in what position are the headaches most severe? It worries me most if a child wakes up at night with a headache or first thing in the morning with a headache that gets better as the day goes on. This is important because the pressure in the head is highest at night when the patient is flat and they are relatively hypo-ventilating, which means that they will have cerebral vasodilatation. So, I always worry most about headaches that are present on awakening in the morning before the child gets out of bed. Such a patient may decide that they need to have several pillows or to sleep in a recliner, or something of this sort. The opposite side would be the child that wakes up feeling pretty good, but by 10 or 11 o'clock in the morning is feeling poorly at school, goes to the nurse's office and lies down, feels better after lying down for a half hour, and then once again at three or four o'clock is ready to lie down again. That timing, and the suggestion that the patient is better when flat, would suggest that that child is suffering from low pressure rather than high. So, I always ask the parents a bit about the temporal and positional correlates of the headaches. It's not always easy for a parent to explain, and it may be that they have not noticed a difference with temporal and positional factors, but this is always one of the things that I am most interested in hearing about.
- And if I may ask, Joe, the child who comes to the ER with potentially a GI or gastroenteritis symptoms versus shunt malfunction, they both have nausea and vomiting as some of their symptoms, what are the details that you look for in that specific situation?
- I think that I am always interested in whether the child has fever associated with their vomiting, and/or headaches. I'm always interested in knowing whether they have diarrhea, and for the most part, I like children that have headaches and vomiting to also have diarrhea and to have fever. Those are things that, unless the shunt has been manipulated recently, would suggest to me that it is more likely a viral illness than it is a shunt malfunction.
- Thank you.
- Many times, parents will tell me that the child just does not look right. And the thing that they will most frequently say is that the eyes are different. They may tell you that the child's eyes are crossing or that they're having a lazy eye, which they did not before. Many children, especially premature babies or children with hydrocephalus or other neurologic problems, may have some element of strabismus. But if the family tells you that the eyes are crossed and they have not been in the past, then it suggests that this may be a sixth-nerve palsy or a non-specific indicator of elevated pressure. They may also say that the child looks scared or surprised. And if that is what they report, it may well be what the child has is some element of upgaze paresis. And as the eyes are deviated down towards the nose, more sclera is showing up top, and the family would interpret this as the child looks wide-eyed, scared, or surprised, and it may be an upgaze paresis. Those children may even look down their nose or tilt the head back to compensate for the fact that they can't look up. And a third thing that parents will frequently describe is that the child's eyes or face looks puffy. And if this is something that the parent says, it's very highly suggestive of a shunt problem. The degree of puffiness in the periorbital region that is sufficient for the parent to worry may not even be evident to the neurosurgeon or the observer that's not related to the child. And I take great interest when a parent tells you that the child's face looks puffy. That puffiness may well be an indicator of a shunt malfunction. It's generally seen in babies, or toddlers, as opposed to 12-year-olds or teenagers. But these are some of the things that the family may tell me that would make me very concerned that we may be dealing with a shunt problem. When we're examining the child with a ventricular peritoneal shunt, if the child is young enough to have open sutures and a head that can grow, of course, we're interested in how the fontanelle feels, whether the sutures are separated, and what's been happening to the OFC, or the head size. I always keep track of what the child's head size is in my clinic charts so that I know what his baseline is. And what's nice is that when a child gets old enough that their head no longer grows in response to pressure from within, they may be verbal to the point where they can talk to you. So, you're substituting a growing head for a child that's more articulate. In looking at the shunt itself, I think that three of the things that I'm most interested in is whether there's any erythema over the shunt to suggest infection or inflammation, whether or not there is swelling around the shunt, which one can see either with infection or with a shunt that's disrupted so that the spinal fluid is tracking around the shunt instead of through it. You also may be able to feel or palpate a disconnection or discontinuity in this shunt. These are some of the things that I'm interested in looking at the shunt itself. The abdomen is also of interest, that if one has an infection in the shunt, they may have almost an acute abdomen picture. On the other hand, if there is an infection or peritoneal malabsorption that is longstanding, the belly may be big with ascites, or a CSFoma within the belly itself. Once we have examined the patient and made an assessment of how sick they are, the next question is, what sorts of tests are the most useful to us in evaluating the shunt function? Now, when I was a resident many years ago, it was almost a knee-jerk response to tell the people in the emergency room, "Well, get a CAT scan and a shunt series and call me when they're done." These are still nice ways of looking at the shunt, the CAT scan to see how the ventricles look, and the shunt series to evaluate the continuity of the shunt or evaluate for disconnections, but if you look at the synapse, or the record of the child's x-rays, you may find that everybody's ordering CAT scans. They're getting a scan at the pediatrician's office because the head is large, they came to the emergency room and got a scan. And what is happening is that the children are getting quite a bit of radiation, so that CT scans may be, in some ways, sub-optimal. One alternative to CT scan, which shows the ventricular system very nicely and is just as good, if not better than the CAT scan, is to do a fast T2 MRI. The fast T2 MRI does not have the radiation that's associated, and it quick enough that even a child that is too young to hold still can have the study completed relatively efficiently. Unfortunately, this may not be available if the child presents quite sick at two o'clock in the morning, in which case the CAT scan is perhaps the study of choice. Another option besides CAT scan would be to do a shunt tap or to prep the skin over the shunt and introduce a butterfly needle into the shunt in an attempt to assess the patency of the shunt and the pressure within the head. Neither the CT scan nor the shunt tap is a perfect test, and each has their own risks, as well as their own advantages in terms of diagnostic benefit.
- Joel, if I may ask you, some folks go ahead and do knee-jerk spinal CT scan, which is unfortunate because especially with young children, the risk of radiation from a CT scan is substantial. And sometimes people court a small risk of infecting the shunt with tapping it. So, either way, there is some risk associated with each one and sometimes it's easier, and some people say, "Well, let's just make the pediatrician feel easy and feel happy. Just tap the shunt anytime you get a call to worry about shunt infection or malfunction." What are your comments? I mean, if somebody shows up and you have a reasonable suspicion that you think there could be a shunt malfunction here, would you just go straight to the CT scan, and they're very young, let's say they're six months to a year, versus tapping the shunt? And if you tap the shunt, how reliable is the measuring of the pressure by elevating the butterfly catheter?
- I think that for the most part, the shunt tap can give you quite a bit of information. The shunt tap can tell you whether the shunt is open and whether there is proximal flow from the shunt, and in fact, one could argue that the best test of shunt function is proximal patency and spontaneous flow so that it can give you useful information. It may be particularly useful in the patient where the CT scans have been done and do not show dramatic changes when there is malfunction present. I am reluctant to aspirate a lot of spinal fluid, unless I know that the ventricles are large, but tapping the shunt does have a very low risk of introducing infection if one preps nicely and uses sterile technique. Many years ago, when shunts first were around and were being used, people looked at the infection rate from a shunt tap and the infection rate from tapping the shunt is really very low, well under 1%, a very low risk of infecting the shunt. Nevertheless, it is, to some extent, invasive and so that if I tap a shunt, I want to get every bit of information that I can from that tap and I don't wanna take it lightly, nor should we take it lightly, getting CAT scans multiple times in young children.
- So, essentially what you're recommending is, if a person has a suspicion of shunt malfunction, you cannot do the CT, do the tap and see if there is evidence of proximal malfunction and just proceed with shunt revision.
- Yes, and I am most aggressive when the patient looks quite ill. In other words, I would not spare them the procedures if they were quite sick, but I do think it is something that we've grown increasingly focused on, is that the effects of many, many CAT scans or radiations. Many times a child comes with a CAT scan in hand, or if you decide that the CAT scan is indicated, it is very nice if there is a comparison. And when children move or children travel, I think it's reasonable for the parents to have a CD with their CT scan from their point of origin, if you will, because the CT scan really has meaning in the context of the prior studies. There are certain children that if the ventricles are mildly generous, this would be catastrophic, in other children, it may be the norm. So, the CT has meaning in the context of prior studies, and we would like to have a comparison. If that comparison is obtained, it should be obtained at a time when the child is doing well. And if that's the case, then a fast T2 MRI is certainly an option. We say that big ventricles tend to stay big and small ventricles tend to stay small. What that really means is that it takes greater pressure to dilate small ventricles than it does to dilate or maintain the dilatation of a ventricle that is already generous in size. And one could look at it from the physics standpoint where one could say it's much like blowing up a balloon, that if you start out with the balloon small, the first few puffs may hurt your cheeks. Once the balloon gets to a certain size, it really doesn't take as much pressure to blow it up the rest of the way. So, that the fact that big ventricles tend to stay big and small tend to stay small, is important for us in assessing whether the shunt is working and also in deciding what sort of shunt system would be beneficial for someone. When we're looking at a CAT scan, I think that it's natural for our gaze to be drawn to the bodies of the lateral ventricles, that's basically what we're looking at. But especially in a situation where those ventricles are quite large, it may be hard for us to appreciate differences in size in very large ventricles. You can have a significant decrease or increase in volume and the diameter or the volume doesn't reflect that. The volume of an object that is five centimeters in diameter is really twice that of one that is four centimeters in diameter, because it's a linear measurement and you cube that. So, I would encourage you when you are trying to see if there are differences in a scan, to look at the small CSF spaces, for example, the temporal horns, the fourth ventricle, or even the interhemispheric fissure. This may lead you to pick up subtle changes that are harder to tell in the patient with very large ventricles. When I say that it's nice to have a prior CT scan or that the CT has meaning in the context of prior studies, this is a child who was recently moved to Indiana, had previously had a shunt placed in Washington state with only one revision, and has also had a reconstruction, a cranial reconstruction done. And this child came to the emergency room, it's a preschool-aged child, very lethargic, had been vomiting, the pupils were equal, but reacted minimally, the child was even somewhat hypothermic and did almost nothing. He was also bradycardic in the range of 50s and 60s so that everything would speak to shunt malfunction, but we had no prior CT scan. This is a child where you have to believe the patient and not the scan, and this child needs to have aggressive diagnosis. The shunt was tapped, and despite this beautiful-looking scan, was found to be obstructed. And when we revised the shunt, the patient did fine. But this shows the importance of having previous scans. We say that generally speaking, radiographically and clinically, the patient with a shunt malfunction tends to present the way they presented with their prior malfunction. Here, the child had only had one revision, but this shows the pitfalls of being reassured by small ventricles because the shunt was completely obstructed and the child woke up and did well after the revision. Another thing that can be somewhat problematic on CT scan is when you see what would appear to be a progressive or new difference in the size of the two ventricles. In other words, this patient had not had any scans for a number of years. And when we looked at this scan in the patient who is a preteen and is having headaches that sound high pressure from their temporal and positional correlates, we see that the ipsilateral ventricle is completely slit and the contralateral is quite plump. So, the question is, does the patient have low pressure from over-drainage of the ipsilateral ventricle? Is this ventricle trapped to where the pressure is high and that ventricle isn't draining, and what's the cause of the problem? You may have a failure of the two sides to communicate, and this would be a good reason for the headaches and the scan to appear like this. You also may see an appearance like this when the patient has a discrepancy in size between the two ventricles, which is not that unusual or abnormal, and then gets a proximal obstruction, which results in the preferential dilatation of the ventricle that is already larger. So, that this may be the picture of a proximal obstruction where the slit ventricle does not dilate as much as the opposite. It may be the picture of a trapped ventricle, if you will, or this may be a patient that has over-drainage. And one has to do further studies, this CT does not tell you for sure if the patient has a proximal obstruction, if the patient has non-communication, or what. And there are ways to tell that, but this is the thing that you will see. The larger ventricle tends to dilate preferentially because big ventricles get bigger easier than small ventricles. Trapped fourth ventricle is another dilemma, or something that we may see in a child that has headaches, and vomiting, and question shunt malfunction. And in order to get a trapped fourth ventricle, what you really need is to have that fourth ventricle unable to drain into the subarachnoid space and have absorption, so, communicating hydrocephalus. It drains into the subarachnoid space, but it's not absorbed. You also, if the child is shunted, need to have inability for that CSF in the fourth ventricle to track up the aqueduct and be drained by the shunt. So, trapped fourth ventricle is requiring communicating hydrocephalus and obstruction of the aqueduct. Most often you'll see it in children with post-hemorrhagic hydrocephalus or prematurity, sometimes you will see it in children who have infectious or inflammatory hydrocephalus. And I think that rarely, if this trapped fourth ventricle is unchanged and has been present for a long time, this child is probably 13, is it going to be the cause of the troubles? Most frequently, you will see increased vomiting and spasticity with a trapped fourth. And the number that I shunt is really very small, so that I would encourage you not to get too aggressive about assuming that it's the fourth ventricle that is the problem. Maybe the most difficult thing that we see in patients on CT scans, or a way that the CT scan can be misleading or complicated to diagnose, is if the patient has an abnormality of the brain stiffness, if the brain volume pressure relationships are off, or if there's a compliance abnormality, if you will. I believe that this happens perhaps more than we realize. And I think for the most part, it's iatrogenic, it's usually a patient that we have predisposed to this change in their compliance or stiffness. I think perhaps the case that was the most clear-cut or explains things the best was a patient who had a pineal tumor and presented with pineal tumor, profound visual loss, and obstructive hydrocephalus on the basis of that tumor. That patient had a ventricular peritoneal shunt placed at the time of presentation, and then came to see me several weeks later with a shunt in place. The vision had actually improved, the ventricles had come down nicely, but there was no diagnosis yet for the pineal tumor when I first saw the patient. We operated on that youngster from an infratentorial supracerebellar approach so that the patient was prone, he was in a prone position, did the craniotomy, retracted the cerebellum down, and the surgery went quite well. We prepped out the shunt, which I think is always nice to do, at least the reservoir to tap to shunt, and my impression at the time of surgery was that the brain seemed to be getting a little bit full or that my exposure wasn't as nice. Now, with that supracerebellar approach, it's never gonna be beautiful, but I did tap the shunt and it was patent, and the pressure was low and I could withdraw as much spinal fluid as I would like. We finished up the surgery, we finished up the surgery which lasted a number of hours, closed the patient's head, and he was very slow to wake up, seemed listless and lethargic much as he had been before the shunt was placed, went down to CAT scan, and the ventricles are very, very large as if he had never been shunted. We tapped the shunt again, it's patent and the pressure is low, so that the pressure in the head is now lower than the resistance of the valve and the shunt isn't working. And we have reset his stiffness, or we have changed the relationships because the head and the ventricles were at atmospheric pressure for a number of hours. During that time, the pressure is lower than the resistance of the shunt valve, and so, no CSF is draining and the ventricles are enlarging. We've closed the head and the pressure is still essentially zero and the shunt still isn't working, but the patient is symptomatic from ventriculomegaly in the face of low pressure or a functional shunt. And so, we have generated a compliance abnormality or a change in the volume pressure relationships by doing that. Let me go ahead and show you some cases, and I'll come back. This is after a Baclofen pump. This is after the patient had been externalized for a time to treat a shunt infection. The other things that we can do to patients that may predispose them to the changes in the compliance or the volume-pressure relationships, would include intradural spine surgery. We open into the spinal subarachnoid space and lower the pressure. We lower it below the resistance of the valve and the ventricles enlarge. So, intradural spine surgery could include spinal cord tumor, it could include tethered cord release. I have even seen the hole from a Baclofen pump generate a low enough pressure that the patient enlarge the ventricles. And I will show you the patient that had the Baclofen pump placed. And this was an early scan afterwards, and the child was lethargic. The ventricles even got quite a bit bigger this, but you could see that they were slit originally. And if we tap the shunt, the pressure is low, the fluid is nice, there's no infection. And the reason that child has developed the progressive ventriculomegaly that you're only seeing the very start of, is because we have lowered the pressure below the pressure of the valve. The same thing can happen if we have a patient who has a shunt infection, or has had say a ruptured bladder, to where the shunt is externalized for a time. When the shunt is externalized, we generally are draining the ventricles fairly aggressively. We then may well elevate that shunt bag, or the external bag, up in an effort to make the ventricles large enough to place the new shunt. This is after such a patient was shunted and the catheter on the next cut can be seen to sit nicely in the ventricle. So, these are situations where we have generated a situation where the pressure in the head is potentially lower than the resistance of the valve. If you want to treat that, there's two ways that you can do it. One is to lower the resistance of the shunt. And many years ago, we always externalized the shunt as a way of treating this. And you may then put the shunt to a very low level. You may drain them at negative 10, negative 15, negative 20, and you'll find that the ventricles come down and the patient's symptoms from the ventriculomegaly improve so that you can externalize the shunt. The attractive thing is that you can see what is coming out and that the shunt is working. The negative is that you have written off at least the bottom end of this shunt. And you may reset or help the patient regain the normal brain stiffness by gradually elevating that bag and not re-shunt them until they have a fairly normal volume-pressure relationship. One could also bend a butterfly needle 90 degrees and put this into the reservoir and drain directly from the shunt. The optimist would say, "Well, we're not necessarily gonna have to do any shunt procedures. When we no longer need the butterfly, we'll pull it out." The pessimist would say, "You may well infect the whole thing by having a needle going through the skin." I suppose my preference is to externalize the shunt, a little bit safer and a little bit cleaner. What's perhaps even a nicer way, instead of lowering the resistance of the system, is to increase the pressure in the head, and one way of doing that is to wrap the neck. This is something that Doctor Ricarte has in the past. And the idea of wrapping that neck is that we increase the venous pressure and therefore the intracranial pressure. And that's the primary effect. And the secondary effect is that the shunt is sped up and the ventricles come down so that wrapping the neck is a very effective way of beating this compliance problem or this volume-pressure problem. And it really is my favorite of these three, but you have to assume that this is a diagnosis of exclusion. If you go wrapping next on people that have proximal obstructions, then clearly you're not gonna be doing them any favors and you won't help the patient. But wrapping the neck may well improve things to the point where the patient does not need to have anything done to the shunt. I usually would use a two-inch ACE wrap, almost no one has a neck big enough for a three, but a two-inch ACE wrap, I would wrap it not as tight as if it was a knee or an ankle, but maybe somewhat tighter than a traditional turtleneck. And I think that that the importance of this compliance issue or this issue with large ventricles and low pressure is to recognize its existence, to know some of the things that we do to people to predispose them to that, and to know some strategies for treating it. It's surprising, given the number of patients that have tethered cord releases and shunts, how infrequently we see this syndrome. But we do see it sometimes in myelominingoceles, status post-tether release. I think it may be on the basis of their Chiari that we don't see it any more than we do, but ventricular enlargement after intradural spine surgery, Baclofen pump placement, lumbar puncture, one thing to consider is that this may not be a shunt malfunction, but it may be a compliance issue. Besides the CAT scan, the other thing that has been long used as sort of the knee-jerk thing recommended by the residents on call is to do a shunt series. Shan series has simply x-rays AP and lateral views of the skull, the chest, and a KUB. And the shunt series x-rays really are done to try to look at the continuity of the shunt. If you get x-rays, just as if you do any test, I think it's important to get as much information as possible from the test. You may find a shunt fracture which is what you were looking for and a malfunction on that basis. You may also find a malposition of the shunt, such as extrusion of the ventricular catheter or erosion of the catheter into the colon to where the shunt is following the path of the colon. You may see an intact shunt in good position, but the sutures on the skull are separated so that it's important to look for any little thing that may give you a clue. Beyond a certain age, the sutures really shouldn't be separated. A paucity of bowel gas in a certain area of the abdomen in proximity to the catheter may be evidence of the CSFoma collection of spinal fluid. The other thing that you could see is a foreign body, such as an adjusted coin or battery in a child. And this would be a nice reason to have vomiting and would not involve us. It would be a shame to assume that it was the shunt if the child had a quarter in the esophagus or something in his throat. The next way that we look at shunts is to tap the shunts. And tapping the shunt, I always prefer using a 25-gauge butterfly. I think this has a large-enough gauge that you can see what is the flow of fluid and a small-enough gauge that you don't make a huge hole into the shunt apparatus, so that a 25-gauge butterfly is my favorite. And if you use one that has 12 inches of tubing, there's about 2 1/2 centimeters to the inch. So, if you multiply that 12 by 2 1//2, you'll get 30 centimeters. And you can say that halfway up the tube is about 15 centimeters of water, a third of the way is 10 centimeters of water, and it may let you gauge what the pressure is. As Doctor Cohen had alluded to, the concern always is that the shunt tap could lead to infection. That's a low risk, and yet whenever we violate the shunt, I think we need to get as much information as possible from that. The first thing I want to know is whether there's proximal patency. In other words, that if you stick that needle into the shunt reservoir, ideally upstream from any resistance, is there good flow of spinal fluid. And spontaneous flow can be checked for by holding the butterfly down so that the fluid is taking the path of least resistance down the tubing, as opposed to down the shunt. I want the shunt to drip spinal fluid without me aspirating it. If you hook a syringe on an aspirate and can get fluid, but it doesn't drip spontaneously, it may be that you're overcoming a partial proximal obstruction and your syringe can exert more negative pressure than the brain should have to exert positive. So, proximal patency is the first thing I wanna know with the shunt tap. If the shunt is obstructed, then you have to take the patient and fix it, you have to take them to surgery. You really don't have a good way to temporize because you have no access to spinal fluid. If the shunt is patent, you may try to estimate the opening pressure. And we said that the butterfly with the 30 centimeters of tubing is a poor man's manometer and you can hold the tubing up and estimate what the pressure is. One thing that I would warn you is that if the distal portion of the shunt is working, say, you have a traditional differential pressure valve that has a resistance of 12 centimeters of water. If the distal portion of the shunt is working, you will never measure pressure greater than 12 even if the pressure inside the head is twice that. And the reason is, as soon as the fluid has access to your butterfly needle, it has access to the reservoir and the valve so that you may underestimate the pressure if the ventricles are very small, and as soon as spinal fluid is made, it comes out the shunt in case of cranial cerebral disproportion, or if there's a partial proximal obstruction, the pressure in the head may be higher. The opening pressure is really only of interest if it measures high. If it measures high, then you feel as though it's got to be a distal problem because the valve shouldn't allow it to do that. The other things that we want from the shunt tap is CSF for analysis and the response to withdrawal of spinal fluid. If you have a patient that is being evaluated in your clinic, for example, and has headaches and you tap the shunt, then it would be nice to know if you take fluid off, does it make them better, does it make them worse? Why tap the shunt in the first place? I think the two reasons, the first would be in order to diagnose whether there is a malfunction or not, and you may elect to do a shunt tap instead of a CAT scan. If a CAT scan has already been done and it shows the ventricles are large, and you know that the patient has small ventricles at baseline, and that the last time they hit a malfunction two years ago the ventricles enlarged, I think you could spare that child a tap because you know it's a malfunction, you don't need, in that situation, to tap the shunt. The other reason is to question whether or not there's infection and my index of suspicion for infection is highest when a short time has elapsed since the shunt was placed or revised so that within the first two to three months, I think that you worry about infection more than you do if the shunt's been in place for a long period of time. We used to say two to three months is the time when you worry about that, it may well be with antibiotic impregnated tubing that some of our infections may be pushed back in terms of their time of presentation. But if a child has had no procedures, either shunt or peritoneal, and that's been for two years, then I wouldn't worry so much that it could be infected. But if you do tap the shunt, see if it's open, see if it's patent. If it's not, then you need to fix it. If it is patent, you probably want spinal fluid for analysis. And I send cultures and gram stain, I also send glucose protein, and a cell-count differential. And that may be quite a lot of studies, but I think you owe it to the child to optimize the benefits of the tap that you have inflicted on them. With infection, we typically see as white cell pleocytosis. In the acute setting, it may be mostly polys and neutrophils, and some of those types of things, maybe even bands. In a chronic infection or an infection with an indolent organism, you may even see mononuclear cells, lymphs and monos. But if you tap the shunt and you find a pleocytosis, even if that shunt's not working, you shouldn't rush to the operating room because if there's infection, then fixing the shunt is not gonna fix the problem. If you see many red cells in your shunt tap, this may be because of scalp contamination. But if you say, "Gee, it was a very atraumatic tap. The fluid didn't flow perfectly, but I was able to aspirate 3CCs and I sent it off," and you see a lot of red cells, it may well be that you're drawing across some choroid plexus, almost like a teabag, but that choroid plexus will turn your spinal fluid a little bit pink, or a little bit colored. So, if you see red cells and you say, "Hmm, you know, I was able to draw that out, but I worked a little harder. Maybe there were some balls in the tubing," then one possibility is it's a partial proximal obstruction, and it might as well be a complete obstruction that needs to be fixed. One other thing that we see sometimes with spinal fluid analysis from a shunt is a number of eosinophils, CSF eosinophilia, or, if you'd prefer a pleocytosis with an eosinophilic predominance. I first saw this phenomenon in premature babies that had intraventricular hemorrhage. It seemed as though a lot of those children were having shunt revision after shunt revision and they were plugging proximally and they were plugging distally. The spinal fluid sometimes was teaming with eosinophils and also generally, you saw increased protein and decreased glucose. And it was hard to sort out, is the eosinophil the newborn's neutrophil, in other words, that is this sign of infection? Is it related to being a premature baby, or is it related to the blood? I've come to the conclusion that it usually is a combination of the blood and the shunt because we see it second most frequently in children who have massive hydrocephalus are shunted and probably have some blood in the spinal fluid from decompression. The most intense case that I've seen of this CSF eosinophilia was in a child that had a bleeding disorder involving a hypercoagulable state with a secondary sort of a consumptive coagulopathy who bled two weeks after a shunt revision and bled into her head did fine. But we had the opportunity to sample the spinal fluid in an ongoing way and the eosinophils came to the blood like sharks so that this child had the eosinophils, the protein and the glucose, and she wasn't a premature child. So, I think that we see it most frequently in the setting of blood in the shunt. Often, if you have that CSF eosinophilia, you'll see swelling around the shunt at the level of the scalp. And it's a little bit of a vicious circle because I think when you have the swelling around the shunt and the CSF has access to the subcutaneous or subgaleal space that the inflammatory response may get considerably worse, you could look at it the other way and say that the poor shunt function prompts the CSF to come around the shunt instead of through it. But I think that fluid around the shunt is frequently associated with this eosinophils. Whether it's the swelling causes the eosinophils, or vice versa, I think it's a bit of a vicious circle. When I first saw this and had the idea that it's an inflammatory response to the shunt, my first strategy after we saw that revising the shunt repeatedly didn't seem to do the trick, was to de-bulk the allergen, if you would, or the immunogen. We would take the shunts out of those little premature babies and put reservoirs in for tapping and not put a new shunt in until we saw the CSF numbers come close to normalizing. And that is a very effective strategy. We saw it work repeatedly. Unfortunately, some of the patients with this maybe older children, or term babies, and it's a shame to keep them in the hospital to tap a little reservoir. So, I looked for a different way to treat this eosinophils. And the first thing that I tried was steroids, and Decadron is sort of the neurosurgeon steroid, but as time went on, I gravitated towards using the pre-lam, which is what the pediatricians do for asthma flare. One or two milligrams per kilogram per day divided BID, and it's very effective at calming that inflammatory response. Just as with the compliance issue that you have to make sure is not a proximal obstruction, in this case, you need to watch the cultures because if you treat an unrecognized infection with steroids, then certainly that is not in the patient's best interests. But this is a very effective way at knocking down the eosinophils. I also think when you see swelling around the shunt that it's a good thing to try to wrap the head or compress that in such a way that you don't have that ongoing cycle of swelling eosinophils, eosinophil swelling. But this CSF eosinophilia can be a very difficult thing to beat. And I'm not suggesting that the steroids alone will obviate the need for revisions at times, but I think that if those revisions need to be done, if they're done under the cover of the steroids, which don't have to be going for very long, the new shunt has a better chance of functioning in a long-term way. So that that CSF eosinophilia is something that we see not infrequently. The timing of it, I seen it most frequently at about two weeks after the shunt is put in. And my suspicion is that it probably happens in children that do not have shunt malfunctions and is transient and self-limited, but at times it may be associated with multiple malfunctions. One other group of children that is tremendously problematic and would involve difficulty troubleshooting the shunt is patients that are symptomatic. They maybe have headaches, maybe have vomiting, maybe have lethargy with small ventricles. And this is what people have called a slit ventricle picture, a slit ventricle syndrome. One reason is simply shunt malfunction. And if we say that small ventricles tend to stay small, perhaps that patient has a shunt malfunction and the compliance or stiffness is such that the ventricles just don't dilate, so that you can't assume the small ventricles mean the shunt is not malfunctioning. And the first child I showed with no prior scans as an example, shunts can malfunction, the ventricles be small. There is some situation where it would be nice to do the tap and ensure that the shunt is patent. Intermittent proximal malfunction is what McLaurin had described many years ago, that the ventricles are small, the shunt obstructs proximally, the patient comes to the ER, the shunt opens back up again as the ventricle dilates. So, that may be an intermittent proximal malfunction. You could argue that both of these, and for that matter, the other three categories as well, come about because we shunt people too well for too long. The skeptic might say the two kinds of shunts that exist are ones that aren't working and ones that are working too fast. And these are all complications of shunts that are working too fast. Low-pressure headaches, we should be able to sort out with the temporal and positional correlates. Vascular headaches, we may predispose children to because we have taken out the CSF that normally provides a buffer to changes in the pressure with vascular dilatation and constriction. And my drug of choice for the vascular headaches is sustained-release verapamil, although beta blockers in the non-asthmatic child, or Elavil, are helpful. And low-pressure headaches and vascular headaches may be related. The low-pressure headaches are more clearcut in terms of their temporal and positional correlates. And if you want to figure out whether someone has low-pressure headaches, you've done the tap, the shunt is open, the pressure seems low, and you can wrap the neck very much as you did for the large ventricles, but here we're doing it simply to elevate the pressure and see if they are better. The most feared complication, at least my most feared complication, is craniocerebral disproportion. If the shunt has worked so well for so long that the head now is fused at a size that is no longer sufficient for the growing brain, then you may have very high pressures in the head despite a functional shunt, and this is a child that needs to have the head expanded. Obviously, that's a massive undertaking and I wouldn't consider doing it without ICP monitoring to show that, in fact, that is the case. Now, we talked a little bit, and I'll finish up here shortly, we talked a little bit about the traditional ways of evaluating the shunt, CAT scan, shunt series, shunt tap, isotope injection is not something we do frequently. When one of our residents rotated at another institution and it was a patient with a shunt issue, and he suggest maybe we could do a nuclear shunt injection, they said, "Well, who did you train with? They must be really old." At that time, it wasn't true, I suppose now it would be. But the nuclear isotope injection, we put isotope into the shunt proximal to a point where we could put pressure over it and see the speed with which it clears. I probably only do a nuclear shunt injection once every few months, but it may be helpful because it's a physiologic test. Provocative maneuvers, if you have a patient in clinic, and it's very hard to sort out whether they have high pressure, low pressure, or unrelated, is you can wrap the neck if you want to try to elevate the pressure, you can give them Diamox if you want to try to see how they do if the pressure is lowered. So that a short course of Diamox, I think Diamox is like buying on credit, it's not something that you should do in an ongoing way, but a few days at a time as a diagnostic maneuver. In the very refractory cases where the shunt seems to be fine but the patient seems to have high pressure, or perhaps you think they are having low pressure and you can't sort it out, an ICP monitor is a reasonable thing to try. And the last thing, what they would say at Children's Memorial is that the only true test of shunt function is exploration. And I think, in some ways, that's true. I suppose, on the other hand, you could say the only real way to make a definitive diagnosis is with an autopsy. And just like the shunt exploration, the autopsy is something we'd prefer to make the diagnosis before going to exploration, but you have to believe that child and not the studies, and sometimes exploration is mandatory despite the fact that you've exhausted your other tests and can't get things figured out. With a sick patient, believe the patient, not the CT scan or the shunt tap. And I think that my thoughts.
- Joel, this is an excellent talk, especially talking about intermural procedures in patients who have shunts. One idea is, let's say you have a diagnosis of shunt infection. Some people go ahead and take the entire shunt out, put an EVD in, and treat the CSF with antibiotic until it's cleared, based on the cultures and sensitivities. Some folks leave the shunt in if the shunt is not obstructing and a patient is not symptomatic. Clear the CSF with the same shunt in, go back in surgery when the CSF is cleared, take out the entire shunt and put a new shunt in. Do you have any thoughts in those two approaches?
- I think many years ago, many years ago in Cincinnati, people tried to clear the shunts with IV antibiotics alone or IV antibiotics and injection into the shunt, and the success rate was not as high as one would like so that most people will externalize the shunt at the very least, or take the shunt out and put in a ventriculostomy. There have been studies done many years ago where that was compared to changing the whole shunt out under the cover of antibiotics. I think that changing the shunt out under the cover of antibiotics works better in cases of the VA shunt, where you have a short segment of tubing instead of coils and coils in the belly. I think the most conservative way, and the most traditional way to treat the shunt infection is to externalize the shunt, especially if the ventricles are small. This allows you then to enlarge the ventricles or make it possible to take the shunt out of the top and put in a ventriculostomy without worrying that you won't get the shunt back into place. So that I think the most conservative method would be externalization of the shunt followed by putting in an external ventriculostomy, especially if the cultures were persistently positive. There are two places where the infection can be. One is in the head, and we have the ability to sample the CSF. The other is in the belly. And once the catheter is out of the belly, the antibiotic should clear that, but we really don't have a good way of assessing that. So, that my preference is to externalize the shunt, and then if need be, which is usually the case, put in a ventriculostomy. In a case of a child with large ventricles in the oh-vee-rial infection, you may say, "The ventricles are big enough. I'm taking the shunt out and putting a ventriculostomy in an all-at-one sitting."
- How about the situation where it's 2:00 a.m. in the morning, that patient shows up in the ER, they have large ventricles, they are somewhat sleepy, but not very much. And so, the ventriculomegaly is symptomatic. How about if we tap the shunt, withdraw about 30CC and then do this shunt revision electively in the morning, giving you a chance to also exclude shunt infection, even though there is no evidence of fevers or anything else that would make you suspect there's a shunt infection? Is that a reasonable strategy?
- I think it is reasonable. I would watch them like a hawk. But I think if you tap the shunt and you aspirate off fluid, you know it's not a proximal problem so that you have the ability to tap it again, if necessary. You also have the ability to see whether or not there appears to be any infection so that I am much more aggressive about fixing a proximal obstruction as quickly as possible. I'm much more aggressive with that than a distal problem, which may be on the basis of infection or peritoneal malabsorption. And one has to weigh the risks of taking the patient to surgery in the middle of the night versus having them with potentially elevated pressure. And I think sometimes it's a hard decision to make, but I lean towards being more aggressive with the proximal problem than I do the distal, that may involve infection or malabsorption.
- Well, thanks so much. This was very valuable and very great learning points. We appreciate you being with us, and we look forward to having you with us again.
- Well, thank you for inviting me. And hopefully it's been of some interest or use.
- It has been. Thank you.
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