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  • Childhood-onset Hydrocephalus With Dr. Shenandoah Robinson
    Childhood-onset hydrocephalus encompasses a wide range of disorders with varying clinical implications. There are numerous causes of symptomatic hydrocephalus in neonates, infants, and children, and each predicts the typical clinical course across the lifespan. Etiology and age of onset impact the lifelong management of individuals living with childhood-onset hydrocephalus. In this episode, Casey Albin, MD, speaks with Shenandoah Robinson, MD, FAANS, FAAP, FACS, author of the article “Childhood-onset Hydrocephalus” in the Continuum® June 2025 Disorders of CSF Dynamics issue. Dr. Albin is a Continuum® Audio interviewer, associate editor of media engagement, and an assistant professor of neurology and neurosurgery at Emory University School of Medicine in Atlanta, Georgia. Dr. Robinson is a professor of neurosurgery, neurology, and pediatrics at Johns Hopkins University School of Medicine in Baltimore, Maryland. Additional Resources Read the article: Childhood-onset Hydrocephalus Subscribe to Continuum®: shop.lww.com/Continuum Earn CME (available only to AAN members): continpub.com/AudioCME Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud More about the American Academy of Neurology: aan.com Social Media facebook.com/continuumcme @ContinuumAAN Host: @caseyalbin Full episode transcript available here Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast. Dr Albin: Hi, this is Dr Casey Albin. Today I'm interviewing Dr Shenandoah Robinson about her article on childhood onset hydrocephalus, which appears in the June 2025 Continuum issue on disorders of CSF dynamics. Dr Robinson, thank you so much for being here. Welcome to the podcast. I'd love to start by just having you briefly introduce yourself to our audience. Dr Robinson: I'm a pediatric neurosurgeon at Johns Hopkins, and I'm very fortunate to care for kids and children from the neonatal intensive care unit all the way up through young adulthood. And I have a strong interest in developing better treatments for hydrocephalus. Dr Albin: Absolutely. And this was a great article because I really do think that understanding how children with hydrocephalus are treated really does inform how we can care for them throughout the continuum of their lifespan. You know, I was shocked in reading your article about the scope of the problem for childhood onset hydrocephalus. Can you walk our listeners through what are the most common reasons why CSF diversion is needed in the pediatric population? Dr Robinson: For the United States, and Canada too, the most common reasons are spina bifida---so, a baby that's born with a myelomeningocele and then develops associated hydrocephalus---and then about equally as common is posthemorrhagic hydrocephalus of prematurity, congenital causes such as from aquaductal stenosis, and other genetic causes are less common. And then we also have kids that develop hydrocephalus after trauma or meningitis or tumors or other sort of acquired problems during childhood. Dr Albin: So, it's a really diverse and sort of heterogeneous causes that across sort of the, you know, the neonatal period all the way to, you know, young adulthood. And I'm sure that those etiologies really shift based on sort of the subgroup population that you're talking about. Dr Robinson: Yes, they definitely shift over time. Fortunately for our kids that are born with problems that raise concerns, such as myelomeningocele or if they're born preterm, they sort of declare themselves by the time they're a year old. So, if you're an adult provider, they should have defined themselves and it's unlikely that they will suddenly develop hydrocephalus as a teenager or older adult. Dr Albin: Totally makes sense. I think many of the listeners to this podcast are adult neurologists who are probably very familiar with external ventriculostomies for temporary CSF diversion, and with the more permanent ventricular peritoneal shines or ventricular atrial or plural shines that are needed when there's the need for permanent diversion. But you described in your article two procedures that provide temporary CSF diversion that I think many of our listeners are probably not as familiar with, which is the ventricular access devices and ventriculosubgaleal shunts. Can you briefly describe what those procedures provide? Who are the candidates for them? And then what complications neurologists may need to think about if they're consulted for comanagement in one of these complex patients? Dr Robinson: Well, the good thing is that if as an adult neurologist you encounter someone with, you know, residual tubing from one of these procedures, you are unlikely to need to do anything about it. So, we put in ventricular access device or ventriculosubgaleal shunts, usually in newborns or infants. And sometimes when they no longer need the device, we just leave it in because that saves them an extra surgery. So, if you encounter one later on, it's most likely you won't need to do anything. Often if the baby goes on to show that they need a permanent shunt, we go ahead and put in that permanent shunt. We may or may not go back and take out the reservoir or the subgaleal shunt. The reservoir and subgaleal shunts are often put in the frontal location. Sometimes we'll put the permanent shunt in the occipital location and just leave the residual tubing there. So, you're very unlikely to need to intervene with a reservoir or subgaleal shunt if you encounter an older child or adult with that left in. We use these in the small babies because the external ventricular drains that we're very familiar with have a very high complication rate in this population. In the adult ICU, you often see these, and maybe there's, you know, a few percent risk of infection. It actually heads into 20 to 25% in our preterm infants and other newborns that require one of these devices for drainage. So, we try not to use external ventricular drains like we use in older patients. We use the internalized device: either the ventricular reservoir with a little area for us to tap every day, every other day; or the ventriculosubgaleal shunt, which diverts the spinal fluid to a pocket in the scalp. So, we use these in preterm infants that are too tiny for a permanent shunt. And for some of our babies that are born, for example, with an omphalocele, that we can't use their peritoneal cavity and so we need some temporizing device to manage their CSF. Dr Albin: Totally makes sense. And so just to clarify, I mean, this is a tube that's placed into the ventricles of the brain and then it's tunneled into the subgaleal space and the collection, the CSF, just builds up there, like? Dr Robinson: Yeah. Dr Albin: And over time either, you know, the baby will learn how to account for that extra CSF, and then I guess it's just reabsorbed? Dr Robinson: Yeah. When it's present, though, it looks like maybe, I don't know if you're familiar with like a tissue expander. There is this bubble of fluid under the scalp, but it's prominent, it can be several centimeters in diameter. Dr Albin: Wow, that's just absolutely fascinating. And I don't think I've ever had the opportunity to see this in clinical practice. I've really learned quite a bit about this. I assume that these children are going to go on to get some sort of permanent diversion. And then, you know, over time, those permanent shunts do create a lot of problems. And so, I was hoping you could kind of walk us through, you know, what are some of the things that you're seeing that you're concerned about? And then if you've just inherited a patient who had a shunt placed at, say, a different institution, how do you go about figuring out what kind of shunt it is and if they're still dependent on it? Dr Robinson: There's a few things that, fortunately, technology is helping with. So, it is much easier now for patients to get their images uploaded to image-sharing software, and then we can download their images into our institutional software, which is very helpful. Another option is that we are strongly encouraging our families to use a app such as HydroAssist that's available from the Hydrocephalus Association. So that's an app that goes on your phone, and you can upload the images from an MRI or a CT scan or x-rays from a shunt series. And then that you can take if you're traveling and you have to go to emergency department or you're establishing care with a new provider, you can have your information right there and not be under stress to remember it. It also has areas so you can record the type of valve. And all of our valves have pluses and minuses, they all tend to malfunction a little bit. And they can be particularly helpful with different types of hydrocephalus. I really doubt that we're going to narrow down from the fifteen or so valves we have access to now. And so, recording your valve type, the manufacturer as well as the setting, is very helpful when you're transferring care or if you're traveling and then have to, unfortunately, stop in the emergency department. Dr Albin: Yeah, I thought that was a really great pearl that, like, families now are empowered to sort of take control of understanding sort of the devices that they have, the settings that they're using. And what an incredible thing for providers who are going to care for these patients who, you know, unfortunately do end up in centers that are not their primary center. The other challenge that I find… I practice as a neurointensivist, and sometimes patients come in and they have a history of being shunt dependent and they present with a neurologic change. And I think that we as neurologists can be a little quick to blame the shunt and want the shunt to be tapped. And I was really struck in reading this article about the complexity of shunt taps. And I was hoping, you know, can you kind of walk us through what's involved and maybe why we should have a little bit of a higher threshold before just saying, ah, just have the neurosurgeons tap the shunt. Like, it's not that straightforward. Dr Robinson: And it may depend on the population you're caring for. So, when I was at a different institution, we actually published that there's about a 5% complication rate from shunt taps. And that may be- that was in pediatric patients. And again, that may be population dependent, but you can introduce infection to a perfectly clean shunt by doing a shunt tap. You can also cause an acute shunt malfunction. So that's why we tend to prefer that only neurosurgeons are doing shunt taps for evaluation of a shunt malfunction. There are times that, for example, our patients who are getting intrathecal chemotherapy or something have a CSF access device like an Ommaya reservoir, and other providers may tap that reservoir to instill medicine. But that's different than an evaluation, like, you're talking about somebody with a neurological change. And so, it is possible that if somebody has small ventricles or something, if you tap that shunt, you can take a marginally functioning shunt and turn it into an acute proximal malfunction, which is an emergency. Dr Albin: Absolutely. I think that's a fantastic pearl for us to take away from this. It's just that heightened level. And kind of on the flip side of that, you know, and I really- I do feel for us when we're trying to kind of, you know, make a case that it's, it's not the shunt. Many of our shunted patients also have a lot of neurologic complexity, which I think you really talked upon in this article. I mean, these are patients who have developmental cognitive delays and that they have epilepsy and that they're at risk for, you know, complications from prematurity, since that's a very common reason that patients are getting shunts. But from your experience as a neurosurgeon, what are some of the features that make you particularly concerned about shnut malfunction? And how do you sort of evaluate these patients when they come in with that altered mental status? Dr Robinson: It is challenging, especially for our patients that have, you know, some intellectual delay or other difficulties that make it hard for them to give an accurate history. Problem is, if they're sick and lethargic, they may not remember the symptoms that they had when they were sick. But sometimes there's hopefully there's a family member present that does remember and can say, oh, no, this is what they look like when they have a viral illness. And this is different from when they have the shot malfunction, which was projectile emesis, not associated with a fever. It's rare to have a fever with a shunt malfunction, although shunt infection often presents with malfunction. So, it's not completely exclusionary. We often look at the imaging, but it's taking the whole picture together. Some of the common other diagnoses we see are severe constipation that can decrease the drainage from the shunt and even cause papilledema in some people. So, we look at that as well on the shunt series. It's very important to have the shunt series if you're concerned about shunt malfunction or- the shunt tubing is good. It tends to last maybe 20to 25 years before it starts to degrade. And so, you may have had a functioning shunt for decades and it worked well and you're very dependent on it, and then it breaks and you become ill. But on the flip side, we have patients that have had a broken shunt for years, they just didn't know about it. And we don't want to jump in and operate on them and then cause complexities. And so, it is a challenge to sort out. The simplest thing is obviously if they come in and their ventricles are significantly larger, and that goes along with a several-hour or a couple-day deterioration, that's a little more clear-cut. Dr Albin: Absolutely. And you talked about this shunt series. What other imaging- and, sort of maybe walk us through, what's involved in a shunt series, what are you looking at? And then what other imaging is sort of your preferred method for evaluating these patients? Dr Robinson: In adult patients, the shunt series is the x-ray from the entire shunt. And so, if they have an atrial shunt, that would be skull x-ray plus a chest x-ray; or the shunt ends in the perineal cavity, it goes to the perineum. And we're looking for continuity. We're looking for the- sometimes as people grow and age, the ventricular catheter can pull out of the ventricle. So, we're looking to make sure that the ventricular catheter is in an optimal position relative to the skull. We can also look at the valve setting to see the type of valve. So, that can also be helpful as well. And then in terms of additional imaging, a CT scan or an MRI is helpful. If you don't know what type of valve they have, they should not, ideally, go in the MRI scanner. We like to know what their setting is before they go in the MRI because we're going to have to reset the valve after they come out of the MRI if it's a programmable valve. Dr Albin: This is fantastic. I've heard several pearls. So, one is that with the shunt series, which, am I correct in understanding those are just plain X-rays? Dr Robinson: Yes. Dr Albin: Right. Then we can look for constipation, and that might be actually something really serious in a pediatric patient that could clue us in that they could actually be developing hydrocephalus or increased ICP just because of the abdominal pressure. And then that we need to be mindful of what are the stunt settings before we expose anyone to the MRI machine. Is that two good takeaways from all of this? Dr Robinson: Yes. And it's very rare that there'll be an MRI tech that will allow a patient with a valve in the MRI without knowing what it is. So, they have their job security that way. But yeah, if you're not sure, just go ahead and get the CT. Obviously, in our younger kids, we're trying to avoid CT scans. But if you're weighing off trying to decide if somebody has a shunt malfunction versus, you know, waiting 12 or 24 hours for an MRI, go ahead and get the CT. Dr Albin: Absolutely. I love it. Those are things I'm going to take with me for this. I have one more question about these shunts. So, every now and then, and I think you started to touch on this, we will get a shunt series and we'll see that the catheter is fractured. Do the patients develop little- like, a tract that continues to allow diversion even though the catheter is fractured? Dr Robinson: Yes. So, they can develop scar tissue around, and some people have more scar tissue than others. You'll even see that sometimes, say, the catheter has fractured and we'll take out that old fractured tubing and put in new tubing on the other side. But if you go and palpate their neck or chest, you'll still feel that tract is there because it calcifies along the tract. Some patients drain through that calcified tract for weeks or months without symptoms, and then it can occlude off. So, we don't consider it a reliable pathway. It's also not a reliable pathway if you're positioned prone in the OR. So some of our orthopedic colleagues, for example, if they go to do a spine fusion, we like to confirm that the shunt is working before you undergo that long anesthesia, but also that you're going to be positioned prone and you could potentially- you know, the pressure could occlude that track that normally is open. Dr Albin: This is fantastic. I feel like I've gotten everything I've ever wanted to know about shunts and all of their complications in this, which is, you know, this is really difficult. And I think that because we are not trained to put these in, sometimes we see them and we just say, oh, it's fractured that must be a malfunction. But it's good to know that sometimes those patients can drain through, you know, a sort of scarred-down tract, but that it may not be nearly as reliable as when they have the tubing in place. Another really good thing that I'm going to put in my back pocket for the next time I see a patient with a potential shunt malfunction. Dr Robinson: And we do have some patients that the tubing is fractured years ago and they don't need it repaired, and that totally can be challenging when they then transfer to your practice for follow-up care. We tend to follow those patients very closely, both our clinic visits as well as having them seen by ophthalmology. So, there are teenagers and young adults out there that have… their own system has recovered and they are no longer shunt-dependent; and they may have a broken shunt and not actually be using that track, but they usually have had fairly intensive follow up to prove that they're not shunt-dependent. And we still have a healthy respect there that, you know, if they start to get a headache, we're going to take that quite seriously as opposed to, you know, some of our shunt patients, about 10 to 20%, have chronic headaches that are not shunt-related. So, not everybody who has a headache and has a shunt has a shunt malfunction. It's tough. Dr Albin: This is really tough. That actually brings me to sort of the last clinical scenario that I was hoping we could get your perspective on. And I think this would be of great interest to neurologists, especially in the context that these children may develop headaches that have nothing to do with the shunt. I'd like to sort of give you this hypothetical case that I'm a neurologist seeing a patient in clinic and it’s a teenager, maybe a young adult, and they had a shunt placed early in childhood. They've done really well. And they've come to me for management of a new headache. And, you know, as part of this workup, their primary care provider had ordered an MRI. And, you know, I look at the MRI, and I don't think that the ventricles look really enlarged. They don't look overdrained. Is having an MRI that looks pretty okay, is that enough to exonerate the shunt in this situation? Dr Robinson: In most cases it is. The one time that we don't see a substantial change in the ventricles is if we have a pseudocyst in the abdomen. The ventricles cannot enlarge initially, and then later on they might enlarge. So, we see that sometimes that somebody will come in and their ventricles will be stable in size, but we're still a little bit suspicious. They’ve got this persistent headache. They may have, you know, some emesis or loss of appetite, loss of activity, and a slower presentation than you would get with an acute proximal malfunction. We can check an abdominal ultrasound for them. And sometimes, even though the ventricles haven't changed in size, they still have a malfunction because they have that distal pseudocyst. One of the questions that we ask our patients when we're establishing care, in addition to what valve type they have and what sort of their shunt history or other interventions such as endoscopic third ventriculostomy, is to ask if their ventricles enlarge when they have a shunt malfunction. There is a small fraction where they do not. They kind of have a stiff brain, if you will. And so, it's good to know that. That's one of the key factors is asking somebody, do the ventricles enlarge when they have a malfunction? If they have enlarged in the past, they're likely to enlarge again if they have a malfunction. But again, it's not 100%. So, in peds, 20% of the time the ventricles don't enlarge. So, in adults, I'm not that- you know, I don't know what percentage it is, but it's something to consider that you can have a stable ventricular size and still have a shunt malfunction. So, if your clinical judgment, you're just kind of, like, still uneasy, you know, respect that and maybe do a little more workup. That's why we so much want patients to establish care with somebody, whether it's a neurologist or a neurosurgeon or other provider in some areas that have fewer neurospecialists, but to establish care so that you all know what a change is for that patient. That's really important. Dr Albin: That's fantastic. So, to summarize that, it's really important to understand the patient's baseline and how they presented with prior shunt complications, if they've had some. That if they're coming in with a new headache that we don't have a baseline, so, we should just have a heightened level of awareness that, like, the shunt has a start and it has an end. And even if the start of the shunt in the brain looks okay, there still could be the potential for complications in the abdomen. And maybe the third thing I heard from that is that we should look for GI symptoms and sort of be aware of when there could be a complication in the abdomen as well. Does that all sound about right? Dr Robinson: And especially for our kids with spina bifida and for posthemorrhagic hydrocephalus are now adults, because the preterm infants are prone to necrotizing enterocolitis. And they may not have had surgery for it, but they still may have adhesions and other things that predispose them to develop pseudocysts over time. And then our individuals with spina bifida often have various abdominal surgeries and other procedures to help them manage their bowel and bladder function. And so that can also create adhesions that then predisposes to pseudocysts. So, we do have a healthy respect for that. In addition, it used to be---because we have gotten a little better with shunts over time---it used to be, like, when I was in training that you heard, you know, if you haven't had a shunt malfunction for 10 or 15 years, you must- you may no longer be dependent. And that's not really true. There are some people who outgrow their need for shunt dependence, but not everyone does outgrow it. And so, you can be 15, 20 years without a shunt revision and still be shunt-dependent. Dr Albin: Those are fantastic pearls. I think most of them, walking away with this, like, a very healthy respect for the fact that these are complex patients, which the shunt is one component of sort of the things that can go wrong and that we have to have a really healthy respect and really detailed investigation and sort of take the big picture. I really like that. Dr Robinson: Yeah, I know. I think it's- there's a very strong push amongst pediatric neurosurgery and a lot of the related, our colleagues in other areas, to develop multidisciplinary transition clinics and lifespan programs for these patients to help keep everything else optimized so that they're not coming in, for example, with seizures. But then you have to figure out if this is a seizure or a shunt; you know, if we can keep them on track, if we can keep them healthy in all their other dimensions, it makes it safer for them in terms of their shunt malfunction. Dr Albin: Absolutely. I love that, and just the multidisciplinary preventative aspect of trying to keep these patients well. So important. Dr Robinson, I really would like to thank you for your time. We're getting towards the end of our time together. Are there any other points about the article that you just are anxious that leave the readers with, or should I just direct them back to the fantastic review that you've put together on this topic? Dr Robinson: No, I think that we covered a lot of the high points. I think one of the really exciting things for hydrocephalus is that there's a lot of investigations into other options besides shunts for certain populations. We are seeing less hydrocephalus now with the fetal repair of the myelomeningocele, which is great. And we're trying to make inroads into posthemorrhagic hydrocephalus as well. So, there are a lot of great things on the horizon and, you know, hopefully someday we won't have the need to have these discussions so much for shunts. Dr Albin: I love it. I think that's really important. And all of those points were touched on the article. And so, I really invite our listeners to go and check out the article, where you can see sort of, like, how this is evolving in real time. Thank you, Dr Robinson. Please go and check out the childhood-onset hydrocephalus article, which appears in the most recent issue of Continuum on the disorders of CSF dynamics. And be sure to check out Continuum Audio episodes from this and other issues. Thank you again to our listeners for joining us today. And thank you, Dr Robinson. Dr Robinson: Thanks for having me. Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.
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  • Management of Normal Pressure Hydrocephalus With Dr. Kaisorn Chaichana
    Normal pressure hydrocephalus (NPH) is a pathologic condition whereby excess CSF is retained in and around the brain despite normal intracranial pressure. MRI-safe programmable shunt valves allow for fluid drainage adjustment based on patients’ symptoms and radiographic images. Approximately 75% of patients with NPH improve after shunt surgery regardless of shunt type or location. In this episode, Aaron Berkowitz, MD, PhD, FAAN, speaks with Kaisorn L. Chaichana, MD, author of the article “Management of Normal Pressure Hydrocephalus” in the Continuum® June 2025 Disorders of CSF Dynamics issue. Dr. Berkowitz is a Continuum® Audio interviewer and a professor of neurology at the University of California San Francisco in the Department of Neurology in San Francisco, California. Dr. Chaichana is a professor of neurology in the department of neurological surgery at the Mayo Clinic in Jacksonville, Florida. Additional Resources Read the article: Management of Normal Pressure Hydrocephalus Subscribe to Continuum®: shop.lww.com/Continuum Earn CME (available only to AAN members): continpub.com/AudioCME Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud More about the American Academy of Neurology: aan.com Social Media facebook.com/continuumcme @ContinuumAAN Host: @LyellJ Guest: @kchaichanamd Full episode transcript available here Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast. Dr Berkowitz: This is Dr Aaron Berkowitz, and today I'm interviewing Dr Kaisorn Chaichana about his article on management of normal pressure hydrocephalus, which he wrote with Dr Jeremy Cutsforth-Gregory. The article appears in the June 2025 Continuum issue on disorders of CSF dynamics. Welcome to the podcast, and please introduce yourself to our audience. Dr Chaichana: Yeah, thank you for having me. I'm Kaisorn Chaichana. I'm a neurosurgeon at Mayo Clinic in Jacksonville, Florida. Part of my practice is doing hydrocephalus care, which includes shunts for patients with normal pressure hydrocephalus. Dr Berkowitz: Fantastic. Well, before we get into shunt considerations and NPH specifically, which I know is the focus of your article, I thought it would be a great opportunity for a neurologist to pick a neurosurgeon's brain a bit about shunts. So, to start, can you lay out for us the different types of shunts and shunt procedures, the advantages, disadvantages of each type of shunt, how you think about which shunt procedure should be used for which patient, that type of thing? Dr Chaichana: Yeah. So, there are different types of shunts, and the most common one that is used is called a ventricular peritoneal shunt. So, it has a ventricular catheter, it has a catheter that tunnels underneath the skin and it goes into the peritoneum where the fluid goes from the ventricular system into the peritoneum. Typically, the shunts are in the ventricle because that is the largest fluid-filled space in the brain. Other terminal areas include the atrium, which is really the jugular vein, and those are called ventricular atrial shunts. You can also have ventricular pleural shunts, which end in the pleural space and drain flui into the pleural space. Those are pretty much the most common ventricular shunts. There's also a lumboperitoneal shunt that drains from the lumbar spine, similar to a lumbar drain into the peritoneum. For the lumbar shunts, we don't typically have a lumbar pleural or lumbar atrial shunt just because of the pressure dynamics, because the lumbar spine is below the lung and as well as the atrium. And so, the drainage pattern is very different than ventricular peritoneal which is top to bottom. The most common shunt, why we use the ventricular peritoneal shunt the most, is because it has the most control. So, the peritoneum is set at a standard pressure in the intraabdominal pressure, whereas the ventricular atrial shunt depends on your venous return or venous pressure and your ventricular pleural shunt varies with inspiration and expiration. So, the easiest way for us to control the fluid, the ventricular system is through the ventricular peritoneal shunt. And that's why that's our most common shunt that we use. Dr Berkowitz: Fantastic. So, as you mention in the article, neurologists may be reluctant to offer a shunt to patients with NPH because many patients may not improve, or they improve only transiently; and out of fear of shunt complications. So, of course, as neurologists, we often only hear about a patient’s shunt when there is a problem. So, we have this sort of biased view of seeing a lot of shunt malfunction and shunt infection. Of course, we might not see the patient if their shunt is working just fine. How common are these complications in practice, and how do you as a neurosurgeon weigh the risks against the often uncertain or transient benefits of a shunt in a patient with NPH who may be older and multiple medical comorbidities? How do you think about that and talk about it with patients? Dr Chaichana: When you hear about shunt complications, most of the shunt complications you hear about are typically in patients with congenital hydrocephalus. Those patients often require several shunt revisions just from either growing or the shunt stays in for a long time or the ventricular caliber is a lot less than some with normal pressure hydrocephalus. So, we don't really see a lot of complications with normal pressure hydrocephalus. So that shunt placement in these patients is typically pretty safe. The procedure’s a relatively short procedure, around 30 minutes to 45 minutes to place a shunt, and we can control the pressure within the shunt setting so that we don't overdrain---which means too much fluid drains from the ventricular system---which can cause things like a subdural, which is probably the most common complication associated with normal pressure hydrocephalus. So, to obviate those risks, what we do is typically insert the shunt and then keep the shunt setting at a high setting. The higher the setting, the less it drains, and then we bring it slowly down based on the patient's symptoms to try to minimize the risk of this over drainage in the subdural hematoma while at the same time benefiting the patient. So, there's a concern for shunt in patients with normal pressure hydrocephalus. The concern or the complication risks are very low. The problem with normal pressure hydrocephalus, though, is that over time these patients benefit less and less from drainage or their disease process takes over. So, I do recommend placing this shunt as soon as possible just so that we can maximize their quality of life for that period of time. Dr Berkowitz: So, if I'm understanding you, then the risk of complication is more sort of due to the mechanical factors in patients with congenital hydrocephalus or sort of outgrowing the shunt, their pressure dynamics may be changing over time. And in your experience, an older patient with NPH, although they may have more medical comorbidities, the procedure itself is relatively quick and low-risk. And the actual complications due to mechanical factors, my understanding, are just much less common because the patient is obviously fully grown and they're getting one sort of procedure at one point in time and tend to need less revision, have less complication. Is that right? Dr Chaichana: Yeah, that's correct. The complication risk for normal hydrocephalus is a lot less than other types of hydrocephalus. Dr Berkowitz: That's helpful to know. While we're talking about some of these complications, let's say we're following a patient in neurology with NPH who has a shunt. What are some of the symptoms and signs of shunt malfunction or shunt infection? And what are the best studies to order to evaluate for these if we're concerned about them? Dr Chaichana: Yeah. So basically, for shunt malfunction, it’s basically broken down into two categories. It's either overdrainage or underdrainage. So, underdrainage is where the shunt doesn't function enough. And so basically, they return to their state before the shunt was placed. So that could be worsening gait function, memory function, urinary incontinence are the typical symptoms we look for in patients with normal pressure hydrocephalus and underdrainage, or the shunt is not working. For patients that are having overdrainage, which is draining too much, the classic sign is typically headaches when they stand up. And the reason behind that is when there's overdrainage, there's less cerebrospinal fluid in their ventricular system, which means less intracranial pressure. So that when they stand up, the pressure differential between their head and the ground is more than when they're lying down. And because of that pressure differential, they usually have worsening headaches when standing up or sitting up. The other thing are severe headaches, which would be a sign of a subdural hematoma or focality in their neurological symptoms that could point to a subdural hematoma, such as weakness, numbness, speaking problems, depending on the hemisphere. How we work this up is, regardless if you're concerned about overdrainage or underdrainage, we usually start with a CAT scan or an MRI scan. Typically, we prefer a CAT scan because it's quicker, but the CAT scan will show us if the ventricular caliber is the same and/or the placement of the proximal catheter. So, what we look for when we see that CAT scan or that MRI to see the location of the proximal catheter to make sure it hasn't changed from any previous settings. And then we see the caliber of the ventricles. If the caliber of the ventricles is smaller, that could be a sign of overdrainage. If the caliber of the ventricles are larger, it could be a sign of underdrainage. The other thing we look for are subdural fluid collections or hydromas or subdural hematomas, which would be another sign of lower endocranial pressure, which would be a sign of overdrainage. So those are the biggest signs we look for, for underdrainage and overdrainage. Other things we can look for if we're concerned of the shunt is fractured, we do a shunt X-ray and what a shunt x-ray is is x-rays of the skull, the neck and the abdomen to see the catheter to make sure it's not kinked or fractured. If you're really concerned, you can't tell from the x-ray, another scan to order is a CT of the chest and abdomen and pelvis to look at the location of the catheter to make sure there's no brakes in the catheter, there's no fluid collections on the distal portion of the catheter, which would be a sign of shunt malfunction as well. Other tests that you can do to really exclude shunt malfunction is a shunt patency test, and what that is a nuclear medicine test where radionucleotide is injected into the valve and then the radionucleotide is traced over time or imaged through time to make sure that it's draining appropriately from the valve into the distal catheter into the peritoneum or the distal site. If there's a shunt malfunction that's not drainage, that radioisotope would remain stagnant either in the valve or in the catheter. There's overdrainage, we can't really tell, but there will be a quick drainage of the radioisotope. For shunt infection, we start with an imaging just to make sure there's not a shunt malfunction, and that usually requires cerebrospinal fluid to test. The cerebrospinal fluid can come from the valve itself, or it can come from other areas like the lumbar spine. If the lumbar spine is showing signs of shunt infection, then that usually means the shunt is infected. If the valve is aspirated with- at the bedside with a butterfly needle into the valve and that shows signs of shunt infection, that also could be a sign of infection. Dr Berkowitz: That's very helpful. You mentioned CT and shunt series. One question that often comes up when obtaining neuroimaging in patients with a shunt, who have NPH or otherwise, is whether we need to call you when we're doing an MRI to reprogram the shunt before or after. Is there a way we can know as a neurologists at the bedside or as patients carry a card, like with some devices where we know whether we have to call and bother our neurosurgery colleagues to get this MRI? Or if the radiology techs ask us, is this safe? And is the patient's shunt going to get turned off? How do we go about determining this? Dr Chaichana: Yeah, so unfortunately, a lot of patients don't carry a card. We typically offer a card when we do the shunt, but that card, there's two problems with it. One is it tells the model, but the second thing is it has to be updated any time the shunt is changed to a different setting. Oftentimes patients don't know that shunt setting, and often times they don't know that company brand that they use. There are different types of shunts with different types of settings. If there's ever concern as to what type of shunt they have, an x-ray is usually the best bet to see with a shunt series, or a skull x-ray. A lateral skull x-ray usually looks at the valve, and the valve has certain radio-dense markers that indicate what type of shunt it is. And that way you can call neurosurgery and we can always tell you what the shunt setting is before the MRI is done. Problem with an MRI scan if you do it without a shunt x-ray before is that you don't know the setting before unless the patient really knows or it's in the patient chart, and the MRI can need to change the setting. It doesn't usually turn it off, but it would change the setting, which would change the fluid dynamics within their ventricular system, which could lead to overdrainage or underdrainage. So, any time a patient needs MRI imaging, whether it's even the brain MRI, a spine MRI, or even abdominal MRI, really a shunt x-ray should be done just to see the shunt setting so that it could be returned to that setting after the MRI is done. Dr Berkowitz: So, the only way to know sort of what type of shunt it would be short of the patient knowing or the patient getting care at the same hospital where the shunt was placed and looking it up in the operative reports would be a skull film. That would then tell us what type of shunt is there and then the marking of the setting. And then we would be able to call our colleagues in neurosurgery and say, this patient is getting an MRI this is the setting, this is the type of shunt. And do we need to call you afterwards to come by and reprogram it? Is that right? Dr Chaichana: That's correct, yeah. Dr Berkowitz: Is there anything we would be able to see on there, or it's best we just- best we just call you and clarify? Dr Chaichana: The easiest thing to do is, when you get the skull x-ray, you can Google different types of shunts or search for different shunts, and they'll have markers that show the type of shunt it is as well as the setting that it's at. And just match it up with the picture. Dr Berkowitz: And as long as it's not a programmable shunt, there's no concern about doing the MRI. Is that right? Dr Chaichana: Correct. So, if it's a programmable shunt, even if it's MRI-compatible, we still like to get the setting before and make sure the setting after the MRI is the same. Nonprogrammable shunts can't be changed with MRI scans, and those don't need neurosurgery after the MRI scan, but it should be confirmed before the scan is done. Dr Berkowitz: Very helpful. Okay, so let's turn to NPH specifically. As you know, there's a lot of debate in the literature, some arguing, even, NPH might not even exist, some saying it's underdiagnosed. I think. I don't know if it was last year at our American Academy of Neurology conference or certainly in recent years, there was a pro and con debate of “we are underdiagnosing NPH” versus “we are overdiagnosing NPH.” What's your perspective as a neurosurgeon? What's the perspective in neurosurgery? Is this something we're underdiagnosing, and the times you shunt these patients you see miraculous results? Is this something that we're overdiagnosing, you get a lot of patients sent to that you think maybe won't benefit from a shunt? Or is it just really hard to say and some patients have shunt-responsive noncommunicating hydrocephalus of unclear etiology and either concurrent Parkinson's disease, Alzheimer's, cervical lumbar stenosis, neuropathy, vestibular problems, and all these other issues that play into multifactorial gait to sort of display a certain amount of the percentage of problem in a given patient or take overtime? What's your perspective if you're open to sharing it, or what's the perspective of neurosurgery? Is this debated as it is in neurology or this is just a standard thing you see and patients respond to shunt to some degree in some proportion of the time? And what are the sort of predictors you see in your experience? Dr Chaichana: Yeah, so, for me, I'd say it's too complicated for a neurosurgeon to evaluate. We rely on neurology to tell us whether or not they need a shunt. But I think the problem is, obviously, a part of the workout for at least the ones that I like to do, is that I want them to have a high-volume lumbar puncture with pre- and postgait analysis to see if there's really an objective measure of them improving. If they have an objective measure of improvement---and what's even better is that they have a subjective measure of improvement on top of the objective measure of improvement---then they benefit from a shunt. The problem is, some patients do benefit even though they don't have objective performance increases after a high-volume shunt. And those are the ones that make me the most worrisome to do the shunt, just because I don't like to do a procedure where there's no benefit for the patient. I do see, according to the literature as well, that there's around a 30 to 40%, even 50%, increase in gait function, even in patients that don't have large improvements following the high-volume lumbar puncture. And those are the most challenging patients for us as neurosurgeons because we'll put the shunt in, they say we're no better in terms of their gait, no better in terms of their urinary incontinence. We try to lower their shunt down to a certain setting and we're kind of stuck after that point. The good thing about NPH, though, is that, from the neurosurgery side, the shunt, like I said, is a pretty benign, low-risk procedure. So, we're not putting the patient through a very severe procedure to see if there's any benefit. So, in cases where we try to improve their quality of life in patients that don't have a benefit from high-volume lumbar puncture, we give them the odds of whether or not it's improving and say it might not improve. But because the procedure’s minimally invasive, I think it's a good way to see if we can benefit their quality of life. Dr Berkowitz: Yeah, it's a very helpful perspective. Yeah, those are the most challenging cases on our side as well, right. If the patient- we think they may have NPH, or their gait and/or urinary and/or cognitive problems are- at least have a component of NPH that could be reversible, we certainly want to do the large volume lumbar puncture and/or consider a lumbar drain trial, all discussed in other articles and interviews for this issue of Continuum, But the really tough ones, as you said, there is this literature on patients who don't respond to the large-volume lumbar puncture for some reason but still may be shunt responsive. And despite all the imaging predictors and all the other ways we try to think about this, it's hard to know who's going to benefit. I think that's really a helpful perspective from your end that, as you say in the very beginning of your article, right, maybe there's a little bit too much fear of shunting on the neurology side because when we hear about shunts, it's often in the setting of complication. And so, we're not sort of getting the full spectrum of all the patients you shunt and you see who are doing just fine. They might not improve---the question is related to NPH---but at least they're not harmed by the shunt, and we're maybe overbiased and/or seeing a overly representative sample of negative shunt outcomes when they're actually not that common in practice. Is that a fair summary of your perspective? Dr Chaichana: Yeah, that's correct. So, I mean, complications can occur---and anytime you do a surgery, there are risks of complications---but I think they're relatively low for the benefit that we can help their quality of life. And the procedure's pretty short. So, the risk, it mostly outweighs the benefits in cases with normal pressure hydrocephalus. Dr Berkowitz: Very helpful perspective. So, well, thanks so much again. Today I've been interviewing Dr Kaisorn Chaichana about his article on management of normal pressure hydrocephalus, which he wrote with Dr Jeremy Cutsforth-Gregory. This article appears in the most recent issue of Continuum on disorders of CSF dynamics. Be sure to check out Continuum Audio episodes from this and other issues, and thank you to our listeners for joining us today. Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.
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  • Radiographic Evaluation of Normal Pressure Hydrocephalus With Dr. Aaron Switzer
     Normal pressure hydrocephalus (NPH) is a clinical syndrome of gait abnormality, cognitive impairment, and urinary incontinence. Evaluation of CSF dynamics, patterns of fludeoxyglucose (FDG) uptake, and patterns of brain stiffness may aid in the evaluation of challenging cases that lack typical clinical and structural radiographic features. In this episode, Katie Grouse, MD, FAAN, speaks with Aaron Switzer, MD, MSc, author of the article “Radiographic Evaluation of Normal Pressure Hydrocephalus” in the Continuum® June 2025 Disorders of CSF Dynamics issue. Dr. Grouse is a Continuum® Audio interviewer and a clinical assistant professor at the University of California San Francisco in San Francisco, California. Dr. Switzer is a clinical assistant professor of neurology in the department of clinical neurosciences at the University of Calgary in Calgary, Alberta, Canada. Additional Resources Read the article: Radiographic Evaluation of Normal Pressure Hydrocephalus Subscribe to Continuum®: shop.lww.com/Continuum Earn CME (available only to AAN members): continpub.com/AudioCME Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud More about the American Academy of Neurology: aan.com Social Media facebook.com/continuumcme @ContinuumAAN Full episode transcript available here Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast. Dr Grouse: This is Dr Katie Grouse. Today I'm interviewing Dr Aaron Switzer about his article on radiographic evaluation of normal pressure hydrocephalus, which he wrote with Dr Patrice Cogswell. This article appears in the June 2025 Continuum issue on disorders of CSF dynamics. Welcome to the podcast, and please introduce yourself to our audience. Dr. Switzer: Thanks so much for having me, Katie. I'm a neurologist that's working up in Calgary, Alberta, Canada, and I have a special interest in normal pressure hydrocephalus. So, I'm very happy to be here today to talk about the radiographic evaluation of NPH. Dr Grouse: I'm so excited to have you here today. It was really wonderful to read your article. I learned a lot on a topic that is not something that I frequently evaluate in my clinic. So, it's really just a pleasure to have you here to talk about this topic. So, I'd love to start by asking, what is the key message that you hope for neurologists who read your article to take away from it? Dr. Switzer: The diagnosis of NPH can be very difficult, just given the clinical heterogeneity in terms of how people present and what their images look like. And so, I'd like readers to know that detailed review of the patient's imaging can be very helpful to identify those that will clinically improve with shunt surgery. Dr Grouse: There's another really great article in this edition of Continuum that does a really great job delving into the clinical history and exam findings of NPH. So, I don't want to get into that topic necessarily today. However, I'd love to hear how you approach a case of a hypothetical patient, say, where you're suspicious of NPH based on the history and exam. I'd love to talk over how you approach the imaging findings when you obtain an MRI of the brain, as well as any follow-up imaging or testing that you generally recommend. Dr. Switzer: So, I break my approach down into three parts. First, I want to try to identify ventriculomegaly and any signs that would support that, and specifically those that are found in NPH. Secondly, I want to look for any alternative pathology or evidence of alternative pathology to explain the patient's symptoms. And then also evaluate any contraindications for shunt surgery. For the first one, usually I start with measuring Evans index to make sure that it's elevated, but then I want to measure one of the other four measurements that are described in the article, such as posterior colossal angle zed-Evans index---or z-Evans index for the American listeners---to see if there's any other features that can support normal pressure hydrocephalus. It's very important to identify whether there are features of disproportionately enlarged subarachnoid space hydrocephalus, or DESH, which can help identify patients who may respond to shunt surgery. And then if it's really a cloudy clinical picture, it's complicated, it's difficult to know, I would usually go through the full evaluation of the iNPH radscale to calculate a score in order to determine the likelihood that this patient has NPH. So, the second part of my evaluation is to rule out evidence of any alternative pathology to suggest another cause for the patient's symptoms, such as neurodegeneration or cerebrovascular disease. And then the third part of my evaluation is to look for any potential contraindications for shunt surgery, the main one being cerebral microbleed count, as a very high count has been associated with the hemorrhagic complications following shunt surgery. Dr Grouse: You mentioned about your use of the various scales to calculate for NPH, and your article does a great job laying them out and where they can be helpful. Are there any of these scales that can be reasonably relied on to predict the presence of NPH and responsiveness to shunt placement? Dr. Switzer: I think the first thing to acknowledge is that predicting shunt response is still a big problem that is not fully solved in NPH. So, there is not one single imaging feature, or even combination of imaging features, that can reliably predict shunt response. But in my view and in my practice, it's identifying DESH, I think, is really important---so, the disproportionately enlarged subarachnoid space hydrocephalus---as well as measuring the posterior colossal angle. I find those two features to be the most specific. Dr Grouse: Now you mentioned the concept of the NPH subtypes, and while this may be something that many of our listeners are familiar with, I suspect that, like myself when I was reading this article, there are many who maybe have not been keeping up to date on these various subtypes. Could you briefly tell us more about these NPH subtypes? Dr. Switzer: Sure. The Japanese guidelines for NPH have subdivided NPH into three different main categories. So that would be idiopathic, delayed onset congenital, and secondary normal pressure hydrocephalus. And so, I think the first to talk about would be the secondary NPH. We're probably all more familiar with that. That's any sort of pathology that could lead to disruption in CSF dynamics. These are things like, you know, a slow-growing tumor that is obstructing CSF flow or a widespread meningeal process that's reducing absorption of CSF, for instance. So, identifying these can be important because it may offer an alternative treatment for what you're seeing in the patient. The second important one is delayed onset congenital. And when you see an image of one of these subtypes, it's going to be pretty different than the NPH because the ventricles are going to be much larger, the sulcal enfacement is going to be more diffuse. Clinically, you may see that the patients have a higher head circumference. So, the second subtype to know about would be the delayed onset congenital normal pressure hydrocephalus. And when you see an image of one of these subtypes, it's going to be a little different than the imaging of NPH because the ventricles are going to be much larger, the sulcal enfacement is going to be more diffuse. And there are two specific subtypes that I'd like you to know about. The first would be long-standing overt ventriculomegaly of adulthood, or LOVA. And the second would be panventriculomegaly with a wide foramen of magendie and large discernomagna, which is quite a mouthful, so we just call it PAVUM. The importance of identifying these subtypes is that they may be amenable to different types of treatment. For instance, LOVA can be associated with aqueductal stenosis. So, these patients can get better when you treat them with an endoscopic third ventriculostomy, and then you don't need to move ahead with a shunt surgery. And then finally with idiopathic, that's mainly what we're talking about in this article with all of the imaging features. I think the important part about this is that you can have the features of DESH, or you can not have the features of DESH. The way to really define that would be how the patient would respond to a large-volume tap or a lumbar drain in order to define whether they have this idiopathic NPH. Dr Grouse: That's really helpful. And for those of our listeners who are so inclined, there is a wonderful diagram that lays out all these subtypes that you can take a look at. I encourage you to familiarize yourself with these different subtypes. Now it was really interesting to read in your article about some of the older techniques that we used quite some time ago for diagnosing normal pressure hydrocephalus that thankfully we're no longer using, including isotope encephalography and radionuclide cisternography. It certainly made me grateful for how we've come in our diagnostic tools for NPH. What do you think the biggest breakthrough in diagnostic tools that are now clinically available are? Dr. Switzer: You know, definitely the advent of structural imaging was very important for the evaluation of NPH, and specifically the identification of disproportionately enlarged subarachnoid space hydrocephalus, or DESH, in the late nineties has been very helpful for increasing the specificity of diagnosis in NPH. But some of the newer technologies that have become available would be phase-contrast MRI to measure the CSF flow rate through the aqueduct has been very helpful, as well as high spatial resolution T2 imaging to actually image the ventricular system and look for any evidence of expansion of the ventricles or obstruction of CSF flow. Dr Grouse: Regarding the scales that you had referenced earlier, do you think that we can look forward to more of these scales being automatically calculated and reported by various software techniques and radiographic interpretation techniques that are available or going to be available? Dr. Switzer: Definitely yes. And some of these techniques are already in development and used in research settings, and most of them are directed towards automatically detecting the features of DESH. So, that's the high convexity tight sulci, the focally enlarged sulci, and the enlarged Sylvian fissures. And separating the CSF from the brain tissue can help you determine where CSF flow is abnormal throughout the brain and give you a more accurate picture of CSF dynamics. And this, of course, is all automated. So, I do think that's something to keep an eye out for in the future. Dr Grouse: I wanted to ask a little more about the CSF flow dynamics, which I think may be new to a lot of our listeners, or certainly something that we've only more recently become familiar with. Can you tell us more about these advances and how we can apply this information to our evaluations for NPH? Dr. Switzer: So currently, only the two-dimensional phase contrast MRI technique is available on a clinical basis in most centers. This will measure the actual flow rate through the cerebral aqueduct. And so, in NPH, this can be elevated. So that can be a good supporting marker for NPH. In the future, we can look forward to other techniques that will actually look at three-dimensional or volume changes over time and this could give us a more accurate picture of aberrations and CSF dynamics. Dr Grouse: Well, definitely something to look forward to. And on the topic of other sort of more cutting-edge or, I think, less commonly-used technologies, you also mentioned some other imaging modalities, including diffusion imaging, intrathecal gadolinium imaging, nuclear medicine studies, MR elastography, for example. Are any of these modalities particularly promising for NPH evaluations, in your opinion? Do you think any of these will become more popularly used? Dr. Switzer: Yes, I think that diffusion tract imaging and MR elastography are probably the ones to keep your eye out for. They're a little more widely applicable because you just need an MR scanner to acquire the images. It's not invasive like the other techniques mentioned. So, I think it's going to be a lot easier to implement into clinical practice on a wide scale. So, those would be the ones that I would look out for in the future. Dr Grouse: Well, that's really exciting to hear about some of these techniques that are coming that may help us even more with our evaluation. Now on that note, I want to talk a little bit more about how we approach the evaluation and, in your opinion, some of the biggest pitfalls in the evaluation of NPH that you've found in your career. Dr. Switzer: I think there are three of note that I'd like to mention. The first would be overinterpreting the Evans index. So, just because an image shows that there's an elevated Evans index does not necessarily mean that NPH is present. So that's where looking for other corroborating evidence and looking for the clinical features is really important in the evaluation. Second would be misidentifying the focally enlarged sulci as atrophy because when you're looking at a brain with these blebs of CSF space in different parts of the brain, you may want to associate that to neurodegeneration, but that's not necessarily the case. And there are ways to distinguish between the two, and I think that's another common pitfall. And then third would be in regards to the CSF flow rate through the aqueduct. And so, an elevated CSF flow is suggestive of NPH, but the absence of that does not necessarily rule NPH out. So that's another one to be mindful of. Dr Grouse: That's really helpful. And then on the flip side, any tips or tricks or clinical pearls you can share with us that you found to be really helpful for the evaluation of NPH? Dr. Switzer: One thing that I found really helpful is to look for previous imaging, to look if there were features of NPH at that time, and if so, have they evolved over time; because we know that in idiopathic normal pressure hydrocephalus, especially in the dash phenotype, the ventricles can become larger and the effacement of the sulci at the convexity can become more striking over time. And this could be a helpful tool to identify how long that's been there and if it fits with the clinical history. So that's something that I find very helpful. Dr Grouse: Absolutely. When I read that point in your article, I thought that was really helpful and, in fact, I'm guessing something that a lot of us probably aren't doing. And yet many of our patients for one reason or other, probably have had imaging five, ten years prior to their time of evaluation that could be really helpful to look back at to see that evolution. Dr. Switzer: Yes, absolutely. Dr Grouse: It's been such a pleasure to read your article and talk with you about this today. Certainly a very important and helpful topic for, I'm sure, many of our listeners. Dr. Switzer: Thank you so much for having me. Dr Grouse: Again, today I've been interviewing Dr Aaron Switzer about his article on radiographic evaluation of normal pressure hydrocephalus, which he wrote with Dr Patrice Cogswell. This article appears in the most recent issue of Continuum on disorders of CSF dynamics. Be sure to check out Continuum Audio episodes from this and other issues, and thank you to our listeners for joining today. Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.
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  • Clinical Features and Diagnosis of Normal Pressure Hydrocephalus with Dr. Abhay Moghekar
    Normal pressure hydrocephalus (NPH) is a clinical syndrome characterized by the triad of gait apraxia, cognitive impairment, and bladder dysfunction in the radiographic context of ventriculomegaly and normal intracranial pressure. Accurate diagnosis requires consideration of clinical and imaging signs, complemented by tests to exclude common mimics. In this episode, Lyell Jones, MD, FAAN speaks with Abhay R. Moghekar, MBBS, author of the article “Clinical Features and Diagnosis of Normal Pressure Hydrocephalus” in the Continuum® June 2025 Disorders of CSF Dynamics issue. Dr. Jones is the editor-in-chief of Continuum: Lifelong Learning in Neurology® and is a professor of neurology at Mayo Clinic in Rochester, Minnesota. Dr. Moghekar is an associate professor of neurology at Johns Hopkins University School of Medicine in Baltimore, Maryland. Additional Resources Read the article: Clinical Features and Diagnosis of Normal Pressure Hydrocephalus Subscribe to Continuum®: shop.lww.com/Continuum Earn CME (available only to AAN members): continpub.com/AudioCME Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud More about the American Academy of Neurology: aan.com Social Media facebook.com/continuumcme @ContinuumAAN Host: @LyellJ Full episode transcript available here Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast. Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum: Lifelong Learning in Neurology. Today I'm interviewing Dr Abhay Moghekar, who recently authored an article on the clinical features and diagnosis of normal pressure hydrocephalus for our first-ever issue of Continuum dedicated to disorders of CSF dynamics. Dr Moghekar is an associate professor of neurology and the research director of the Cerebrospinal Fluid Center at Johns Hopkins University in Baltimore, Maryland. Dr Moghekar, welcome, and thank you for joining us today. Why don't you introduce yourself to our listeners? Dr Moghekar: Thank you, Dr Jones. I'm Abhay Moghekar. I'm a neurologist at Hopkins, and I specialize in seeing patients with CSF disorders, of which normal pressure hydrocephalus happens to be the most common. Dr Jones: And let's get right to it. I think most of our listeners who are neurologists in practice have encountered normal pressure hydrocephalus, or NPH; and it's a challenging disorder for all the reasons that you outline in your really outstanding article. If you were going to think of one single most important message to our listeners about recognizing patients with NPH, what would that be? Dr Moghekar: I think I would say there are two important messages. One is that the triad is not sufficient to make the diagnosis, and the triad is not necessary to make the diagnosis. You know these three elements of the triad: cognitive problems, gait problems, bladder control problems are so common in the elderly that if you pick 10 people out in the community that have this triad, it's unlikely that even one of them has true NPH. On the other hand, you don't need all three elements of the triad to make the diagnosis because the order of symptoms matters. Often patients develop gait dysfunction first, then cognitive dysfunction, and then urinary incontinence. If you wait for all three elements of the triad to be present, it may be too late to offer them any clear benefit. And hence, you know, it's neither sufficient nor necessary to make the diagnosis. Dr Jones: That's a really great point. I think most of our listeners are familiar with the fact that, you know, we're taught these classic triads or pentads or whatever, and they're rarely all present. In a way, it's maybe a useful prompt, but it could be distracting or misleading, even in a way, in terms of recognizing the patient. So what clues do you use, Dr Moghekar, to really think that a patient may have NPH? Dr Moghekar: So, there are two important aspects about gait dysfunction. Say somebody comes in with all three elements of the triad. You want to know two things. Which came first? If gate impairment precedes cognitive impairment, it's still very likely that NPH is in the differential. And of the two, which are more- relatively more affected? So, if somebody has very severe dementia and they have a little bit of gait problems, NPH is not as likely. So, is gait affected earlier than cognitive dysfunction, and is it affected to a more severe degree than cognitive dysfunction? And those two things clue me in to the possibility of NPH. You still obviously need to get imaging to make sure that they have large ventricles. One of the problems with imaging is large ventricles are present in so many different patients. Normal aging causes large ventricles. Obviously, many neurodegenerative disorders because of cerebral atrophy will cause large ventricles. And there's an often-used metric called as the events index, which is the ratio of the bitemporal horns- of the frontal horns of the lateral ventricles compared to the maximum diameter of the skull at that level. And if that ratio is more than 0.3, it's often used as a de facto measure of ventriculomegaly. What we've increasingly realized is that this ratio changes with age. And there's an excellent study that used the ADNI database that looked at how this ratio changes by age and sex. So, in fact, we now know that an 85-year-old woman who has an events index of 0.37 which would be considered ventriculomegaly is actually normal for age and sex. So, we need to start adopting these more modern age- and sex-appropriate age cutoffs of ventriculomegaly so as not to overcall everybody with big ventricles as having possible NPH. Dr Jones: That's very helpful. And I do want to come back to this challenge that we've seen in our field of overdiagnosis and underdiagnosis. But I think most of us are familiar with the concept of how hydrocephalus could cause neurologic deficits. But what's the latest on the mechanism of NPH? Why do some patients get this and others don't? Dr Moghekar: Very good question. I don't think we know for sure. And it for a long time we thought it was a plumbing issue. Right? And that's why shunts work. People thought it was impaired CSF absorption, but multiple studies have shown that not to be true. It's likely a combination of impaired cerebral blood flow, biomechanical factors like compliance, and even congenital factors that play a role in the pathogenesis of NPH. And yes, while putting in shunts likely drains CSF, putting in a shunt also definitely changes the compliance of the brain and affects blood flow to the subcortical regions of the brain. So, there are likely multiple mechanisms by which shunts benefit, and hence it's very likely that there's no single explanation for the pathogenesis of NPH. Dr Jones: We explored this in a recent Continuum issue on dementia. Many patients who have cognitive impairment have co-pathologies, multiple different causes. I was interested to read in your article about the genetic risk profile for NPH. It's not something I'd ever really considered in a disorder that is predominantly seen in older patients. Tell us a little more about those genetic risks. Dr Moghekar: Yeah, everyone is aware of the role genetics plays in congenital hydrocephalus, but until recently we were not aware that certain genetic factors may also be relevant to adult-onset normal pressure hydrocephalus. We've suspected this for a long time because nearly half of our patients who come to us to see us in clinic with NPH have head circumferences that are more than 90th percentile for height. And you know, that clearly indicates that this started shortly at the time after birth or soon afterwards. So, we've suspected for a long time that genetic factors play a role, but for a long time there were not enough large studies or well-conducted studies. But recently studies out of Japan and the US have shown mutations in genes like CF43 and CWH43 are disproportionately increased in patients with NPH. So, we are discovering increasingly that there are genetic factors that underlie even adult onset in patients. There are many more waiting to be discovered. Dr Jones: Really fascinating. And obviously getting more insight into the risk and mechanisms would be helpful in identifying these patients potentially earlier. And another thing that I learned in your article that I thought was really interesting, and maybe you can tell us more about it, is the association between normal pressure hydrocephalus and the observation of cervical spinal stenosis, many of whom require decompression. What's behind that association, do you think? Dr Moghekar: That's a very interesting study that was actually done at your institution, at Mayo Clinic, that showed this association. You know, as we all get older, you know, the incidence of cervical stenosis due to osteoarthritis goes up, but the incidence of significant, clinically significant cervical stenosis in the NPH population was much higher than what we would have expected. Whether this is merely an association in a vulnerable population or is it actually causal is not known and will need further study. Dr Jones: It's interesting to speculate, does that stenosis affect the flow of CSF and somehow predispose to a- again, maybe a partial degree for some patients? Dr Moghekar: Yeah, which goes back to the possible hydrodynamic theory of normal pressure hydrocephalus; you know, if it's obstructing normal CSF flow, you know, are the hydrodynamics affected in the brain that in turn could lead to the development of hydrocephalus. Dr Jones: One of the things I really enjoyed about your article, Abhay, was the very strong clinical focus, right? We can't just take an isolated biomarker or radiographic feature and rely on that, right? We really do need to have clinical suspicion, clinical judgment. And I think most of our listeners who've been in practice are familiar with the use and the importance of the large-volume lumbar puncture to determine who may have, and by exclusion not have, NPH, and then who might respond to CSF diversion. And I think those of us who have been in this situation are also familiar with the scenario where you think someone may have NPH and you do a large-volume lumbar puncture and they feel better, but you can't objectively see a difference. How do you make that test useful and objective in your practice? What do you do? Dr Moghekar: Yeah, it's a huge challenge in getting this objective assessment done carefully because you have to remember, you know, subconsciously you're telling the patients, I think you have NPH. I'm going to do this spinal tap, and if you walk better afterwards, you're going to get a shunt and you're going to be cured. And you can imagine the huge placebo response that can elicit in our subjects. So, we always like to see, definitely, did the patient subjectively feel better? Because yes, that's an important metric to consider because we want them to feel better. But we also wanted to be grounded in objective truths. And for that, we need to do different tests of speed, balance and endurance. Not everyone has the resources to do this, but I think it's important to test different domains. Just like for cognition, you know, we just don't test memory, right? We test executive function, language, visuospatial function. Similarly, walking is not just walking, right? It's gait speed, it's balance, and it's endurance. So, you need to ideally test at least most of these different domains for gait and you need to have some kind of clear criteria as to how are you going to define improvement. You know, is a 5% improvement, is a 10% improvement in gait, enough? Is 20%? Where is that cutoff? And as a field, we've not done a great job of coming up with standardized criteria for this. And it varies currently, the practice varies quite significantly from center to center at the current time. Dr Jones: So, one of the nice things you had in your article was helpful tips to be objective if you're in a lower-resource setting. For you, this isn't a common scenario that someone encounters in their practice as opposed to a center that maybe does a large volume of these. What are some relatively straightforward objective measures that a neurologist or someone else might use to determine if someone is improving after a large-volume LP? Dr Moghekar: Yeah, excellent question, Dr Jones, and very practically relevant too. So, you need to at least assess two of the domains that are most affected. One is speed and one is balance. You know, these patients fall ultimately, right, if you don't treat them correctly. In terms of speed, there are two very simple tests that anybody can do within a couple of minutes. One is the timed “up-and-go” test. It's a test that's even recommended by the CDC. It correlates very well with faults and disability and it can be done in any clinic. You just need about ten feet of space and a chair and a stopwatch, and it takes about a minute or slightly more to do that test. And there are objective age-associated norms for the timed up-and-go test, so it's easy to know if your patient is normal or not. The same thing goes for the 10-meter walk test. You do need a slightly longer walkway, but it's a fairly easy and well-standardized test. So, you can do one of those two; you don't need to do both of them. And for balance, you can do the 30-second “sit-to-stand”; and it's literally, again, 30 seconds. You need a chair, and you need somebody to watch the patient and see how many times they can sit up and stand up from a seated position. Then again, good normative data for that. If you want to be a little more sophisticated, you can do the 4-stage balance test. So, I think these are tests that don't add too much time to your daily assessment and can be done with even trained medical assistants in any clinic. And you don't need a trained physical therapist to do these assessments. Dr Jones: Very practical. And again, something that is pretty easily deployed, something we do before and then after the LP. I did see you mentioned in your article the dual timed up-and-go test where it's a simultaneous gait and executive function test. And I’ve got to be honest with you, Dr Moghekar, I was a little worried if I would pass that test, but that may be beyond the scope of our time today. Actually, how do you do that? How do you do the simultaneous cognitive assessment? Dr Moghekar: So, we asked them to count back from 100, subtracting 3. And we do it particularly in patients who are mildly impaired right? So, if they're already walking really good, but then you give them a cognitive stressor, you know, that will slow them down. So, we reserve it for patients who are high-performing. Dr Jones: That's fantastic. I'm probably aging myself a little here. I have noticed in my career, a little bit of a pendulum swing in terms of the recognition or acceptance of the prevalence of normal pressure hydrocephalus. I recall when I was a resident, many, many people that we saw in clinic had normal pressure hydrocephalus. Then it seemed for a while that it really faded into the background and was much less discussed and much less recognized and diagnosed, and less treated. And now that pendulum seems to have swung back the other way. What's behind that from your perspective? Dr Moghekar: It's an interesting backstory to all of this. When the first article about NPH was published in the Newman Journal of Medicine, it was actually a combined article with both neurologists and neurosurgeons on it. They did describe it as a treatable dementia. And what that did is it opened up the floodgates so that everybody with any kind of dementia started getting shunts left, right, and center. And back then, shunts were not programmable. There were no antibiotic impregnated catheters. So, the incidence of subdural hematomas and shunt-related infections was very high. In fact, one of our esteemed neurologists back then, Houston Merritt, wrote a scathing editorial that Victor and Adam should lose their professorships for writing such an article because the outcomes of these patients were so bad. So, for a very long period of time, neurologists stopped seeing these patients and stopped believing in NPH as a separate entity. And it became the domain of neurosurgeons for over two or three decades, until more recently when randomized trials started being done early on out of Europe. And now there's a big NIH study going on in the US, and these studies showed, in fact, that NPH exists as a true, distinct entity. And finally, neurologists have started getting more interested in the science and understanding the pathophysiology and taking care of these patients compared to the past. Dr Jones: That's really helpful context. And I guess that maybe isn't rare when you have a disorder that doesn't have a simple, straightforward biomarker and is complex in terms of the tests you need to do to support the diagnosis, and the treatment itself is somewhat invasive. So, when you talk to your patients, Dr Moghekar, and you've established the diagnosis and have recommended them for CSF diversion, what do you tell them? And the reason I ask is that you mentioned before we started recording, you had a patient who had a shunt placed and responded well, but continued to respond over time. Tell us a little bit more about what our patients can expect if they do have CSF diversion? Dr Moghekar: When we do the spinal tap and they meet our criteria for improvement and they go on to have a shunt, we tell them that we expect gait improvement definitely, but cognitive improvement may not happen in everyone depending on what time, you know, they showed up for their assessment and intervention. But we definitely expect gait improvement. And we tell them that the minimum gait improvement we can expect is the same degree of improvement they had after their large-volume lumbar puncture, but it can be even more. And as the brain remodels, as the hydrodynamics adapt to these shunts… so, we have patients who continue to improve one year, two years, and even three years into the course of the intervention. So, we’re, you know, hopeful. At the same time, we want to be realistic. This is the same population that's at risk for developing neurodegenerative disorders related to aging. So not a small fraction of our patients will also have Alzheimer's disease, for example, or go on to develop Lewy body dementia. And it's the role of the neurologist to pick up on these comorbid conditions. And that's why it's important for us to keep following these patients and not leave them just to the neurosurgeon to follow up. Dr Jones: And what a great note to end on, Dr Moghekar. And again, I want to thank you for joining us, and thank you for such a wonderful discussion and such a fantastic article on the clinical diagnosis of normal pressure hydrocephalus. I learned a lot reading the article, and I learned a lot more today just in the conversation with you. So, thank you for being with us. Dr Moghekar: Happy to do that, Dr Jones. It was a pleasure. Dr Jones: Again, we've been speaking with Dr Abhay Moghekar, author of a wonderful article on the clinical features and diagnosis of NPH in Continuum's first-ever issue dedicated to disorders of CSF dynamics. Please check it out. And thank you to our listeners for joining today. Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.
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  • Treatment and Monitoring of Idiopathic Intracranial Hypertension With Drs. John Chen and Susan Mollan
    Idiopathic intracranial hypertension (IIH), a condition of increased intracranial pressure (ICP), causes debilitating headaches and, in some, visual loss. The visual defects are often in the periphery and not appreciated by the patient until advanced; therefore, monitoring visual function with serial examinations and visual fields is essential. In this episode, Kait Nevel, MD speaks with John J. Chen, MD, PhD, and Susan P. Mollan, MBChB, PhD, FRCOphth, authors of the article “Treatment and Monitoring of Idiopathic Intracranial Hypertension” in the Continuum® June 2025 Disorders of CSF Dynamics issue. Dr. Nevel is a Continuum® Audio interviewer and a neurologist and neuro-oncologist at Indiana University School of Medicine in Indianapolis, Indiana. Dr. Chen is a professor of ophthalmology and neurology at the Mayo Clinic in Rochester, Minnesota. Dr. Mollan is an honorary professor of metabolism and systems science in the department of neuro-ophthalmology at University Hospitals Birmingham in Birmingham, United Kingdom. Additional Resources Read the article: Treatment and Monitoring of Idiopathic Intracranial Hypertension Subscribe to Continuum®: shop.lww.com/Continuum Earn CME (available only to AAN members): continpub.com/AudioCME Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud More about the American Academy of Neurology: aan.com Social Media facebook.com/continuumcme @ContinuumAAN Host: @IUneurodocmom Guests: @chenmayo, @DrMollan Full episode transcript available here Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast. Dr Nevel: Hello, this is Dr Kate Nevel. Today, I'm interviewing Drs John Chen and Susan Mollan about their article on treatment and monitoring of idiopathic intracranial hypertension, which appears in the June 2025 Continuum issue on disorders of CSF dynamics. Drs Chen and Mollan, welcome to the podcast. And please, could you introduce yourselves to the audience? Dr Chen: Hello, everyone. I'm John Chen, one of the neuro-ophthalmologists at the Mayo Clinic. Thanks for having us here. Dr Mollan: Yeah, it's great to be with you here. I'm Susan Mollan. I'm a consultant neuro-ophthalmologist in Birmingham, England. Dr Nevel: Wonderful. So great to have you both here today, and our listeners. To start us off, talking about your article, can you share with us what you think is the most important takeaway from your article for the practicing neurologist out there? Dr Chen: Yeah, so our article talked about the treatment and monitoring of IIH. And I think one takeaway point is, IIH is becoming much more prevalent now that there's this worldwide obesity epidemic with obesity having- essentially being the largest risk factor for IIH other than female. It's really important to monitor vision because vision loss is often peripheral vision loss at first, which the patient may be completely unaware of. And so, it's important to pair up with an ophthalmologist so you can monitor the papilledema of the visual fields and make sure they don't get permanent vision loss. And in the article, we also talk about- there's been changes in the treatment of severe IIH, where traditionally, we used VP shunts; but there's been a trend toward using more venous sinus stenting in addition to the traditional surgeries. Dr Nevel: Great, thank you. I think probably most of our listeners or a lot of neurologists out there have a pretty good understanding of kind of the basics of the IIH. But can you kind of just go over a few key characteristics of IIH, and maybe some things that are less commonly known or things that are maybe just been kind of better understood over the past decade, perhaps? Dr Mollan: Yes, certainly. I think, as Dr Chen said, it's because this condition is becoming more prevalent, people recognize it. I think it's- we like to go back to the diagnostic criteria so that we're making a very accurate diagnosis. So, the patients may come in to the emergency room with, say, papilledema that's been identified elsewhere or crashing headaches. And it's important to go through that sort of diagnostic pathway, taking a blood pressure, taking a full blood count to make sure the patient is anemic, and then moving forward with that confirmation of papilledema into urgent neuroimaging, whether it's CT or MRI, but including venography to exclude a venous sinus thrombosis. And then if you have no structural lesion that's causing the raised ICP, it's moving forward with your lumbar puncture and carefully checking those pressures. But the patients may not only have crashing headache, they often have pulsatile tinnitus and neck pain. I think some of the features that we're now recognizing is the systemic metabolic effects that are unique to IIH. And so, there's an increased risk of cardiometabolic disease that's over and above what is conferred by obesity. Also, our patients have a sort of maternal health burden where they get impaired fertility, gestational diabetes and preeclampsia. And there's also an associated mental health burden, amongst other things. So we're really starting to understand the spectrum of the disease a bit more. Dr Nevel: Yeah, thank you for that. And that really struck me in your article, how important it is to be aware of those things so that we're making sure that we're managing our whole patient and connecting them with the appropriate providers for some of those other issues that may be associated. For the practicing neurologist out there without all the neuro-ophthalmology equipment, if you will, what should our bedside exam focus on to help us get maybe an early but accurate picture of the patient's visual function when we suspect IIH to be at play, perhaps before they can get in with the neuro-ophthalmologist? Dr Chen: Yeah, I think at the bedside you can still check visual acuity and confrontational visual fields, you know, with finger counting. Of course, you have to know that those are, kind of, crude kind of ways of screening. With papilledema, oftentimes the visual acuity is intact. And the confrontational visual fields aren't as sensitive as automated perimetry. Another important thing will be to do your direct ophthalmoscope and look at the amount of papilledema. If it's grade one or two papilledema on the more mild side, it's actually not vision threatening. It's the higher degrees of papilledema that can cause rapid vision loss. And so, if you look in and you see grade one papilledema, obviously you need to do the full workup, the MRI, MRV, lumbar puncture. But in terms of rapidly getting to an ophthalmologist to screen for vision loss, it's not going to be as important because you're not going to have vision loss at that low grade. If you look in and you see this rip-roaring papilledema, grade five papilledema, that patient is going to be at very severe risk of vision loss. So, I think that exam, looking at the optic nerve can be very helpful. And of course, talking to the patient about symptoms; is there decreased vision Is there double vision from a sixth nerve palsy? Are there transient visual obscurations which would indicate at least a higher degree of papilledema? That'd be helpful as well. Dr Nevel: Great, thank you. And when the patient does get in with a neuro-ophthalmologist, you talk in your article and, of course, in clinical practice, how OCT testing is important to monitor in this condition. Can you provide for the listeners the definition of OCT and how it plays a role in monitoring patients with IIH? Dr Mollan: Sure. So, OCT is short for optical coherence tomography imaging, and really the eye has been at the forefront of OCT alone. Our sort of cardiology colleagues are catching up on the imaging of blood vessels. But what it allows us to do is give us really good cross-sectional, anatomical-level changes that we can see both in the retina and also at the optic nerve head. And it gives us some really good measurements. It's not so good at sort of saying, is this definitely papilledema or not? That sort of lower end of disc elevation. But it is very good at ruling out what we call the pseudopapilledema. So, things like drusens or these other little masses we find underneath the optic nerve head. But in terms of monitoring, because we can longitudinally take these images and the reproducibility is pretty good at the optic nerve head, it allows us to see whether there's direct changes: either the papilledema getting worse or the papilledema getting better at the optic nerve head. It also gives us some indication of what's going on in the ganglion cell layer complex. And that can be helpful when we're thinking about sort of looking at structure versus function. So, ophthalmologists in general, we love OCT; and we spend much more time nowadays looking at the OCT than we really do the back of the eye. And it's just become critical for patients with papilledema to be able to be very accurate from visit to visit to see what's changing. Dr Nevel: How do you determine how frequently somebody needs to see the neuro-ophthalmologist with IIH and how often they need that OCT evaluation? Dr Chen: Once the diagnosis of IIH is made, how often they need to be seen and how frequent they need to be seen depends on the degree of papilledema. And again, OCT is really nice. You can quantify it and then different providers can actually use the same OCT numbers, which is super helpful. But again, if it's grade three papilledema or higher, or article thickness of 200 or higher, I tend to follow them a little bit more closely, trying to treat them more aggressively. Try to get the papilledema down into a safer zone. If it's grade one or two papilledema, we see them less frequently. So, my first visit might be three months out. They come with grade five papilledema, I'm seeing them within a few days to make sure that's papilledema’s come down quickly because we're trying to decide, are they going to need surgery or not? Dr Nevel: Yeah, great. And that's a nice segue into talking a little bit about how we treat patients with IIH after the diagnosis is confirmed. And I'd like to just point out you have a very lovely figure in your article---Figure 5-6,---that I'd like to direct our listeners to read your article and check out that figure, which is kind of an algorithm on how we think about the various treatment options for patients who have IIH, which seems to rely a lot on the degree of presence of papilledema and the presence of vision disturbance. Could you maybe walk us through a little bit about how you think about the different treatment options for patients with IIH and when more urgent surgical intervention might be indicated? Dr Mollan: Yeah, sure. We always find it quite hard in any medical specialty to write these kind of flow diagrams because it's really an individual we're looking at. But these are kind of what we’d say is “broad brushstrokes” into those patients that we worry about, sort of, red disease in those patients, more amber disease. Now obviously, even those patients that may not have severe papilledema, they may have crashing headaches. So, they may be an urgent referral themselves because of that. And so, it's nice to try and work out which end of the spectrum you're working with. If we think of the papilledema, Dr Chen's already laid out the sort of lower end of the prison's scale---our grades one, our grades two---that we're less anxious about. And those patients, we would definitely be having discussions about medical management, which includes acetazolamide therapy; but also thinking about weight management. And it may well be that we talk a little bit further about weight management, but I think it's helpful to sort of coach those conversations after you've made a definite diagnosis. And then laying out the risk that's caused, potentially, the IIH in an individual. And then having a sort of open conversation with them about what changes they can have in their lifestyle alongside thinking about medical therapy. There’s some patients with very low levels of papilledema that we decide not to put on medicines initially. As patients progress up that papilledema grade, we're definitely thinking about medical therapy. And our first line from the IIH treatment trial would be using acetazolamide, but we need to be thinking about using appropriate dosing. So, a lot of the patients that I see can be sent to me with very low doses that may be inappropriate for that person. In the IIHTT they used up to four grams daily in a divided dose. And you do need to counsel your patients when you're putting them on acetazolamide because of the side effects. You've got quite a nice table in this article about the side effects. I think if you get the patient on board, that they understand that they will experience side effects, that is helpful because they will expect it, and then possibly tolerate it a bit better. Moving through to that area where we're more anxious, that visual-threatening papilledema. As Dr Chen said, it's sort of like you look in and it's sort of “blood and thunder” in there. And you need to be getting on and encouraging the ophthalmologist to get a formal assessment of the visual field. It's very difficult to determine exactly the level at which- and we talk about the mean deviation in a lot of our research studies. But in general, it's a combination of things: the patient's journey to get to you, their symptoms, what's going on with the visual field, but what's also happening at the OCT. So, we look in and we see that fluid is seeping towards the fovea. We get very anxious, and those patients may not even have enough time for a rapid escalation of acetazolamide. It may well be at the first presentation, which we would term, like, fulminant; that we'd be thinking about surgical intervention. And I think before I stop, the other thing to say is, the surgical landscape is really changing. So, we're having some good studies coming out in terms of stenting. And so, there is a sort of bracket where it may well be that we are thinking about neuroradiological intervention in an earlier case. They may not quite be at that visual-threatening stage, but they may be resistant to medical treatments. Dr Nevel: Thank you for that. What do you think is a potential pitfall or a mistake to avoid, if you will, in the management of patients with IIH? Dr Chen: I think it's- in terms of pitfalls, I think the potential pitfalls I've seen are essentially patients where we don't necessarily create a good patient physician relationship. Where they don't have buy-ins on the treatment, they don't have buy-ins to come back, and they're lost to follow-up. And these patients can be dangerous, because they could have vision threatening papilledema and if not getting the appropriate treatment---and if they're not monitoring the vision---this can lead to poor outcomes. So, I've definitely seen that happen. As Dr Mollan said, you really have to tell them about the side effects from the medications. If you just take acetazolamide, letting them know the paresthesias and the changes in taste and some of these other side effects, they're going to immediately stop the medication. Again, and these medications do work, proven in the IIH treatment trial. So again, I think that patient-physician relationship is very important to make sure they have appropriate follow up. Dr Nevel: The topic of weight loss in this patient population can be tricky, and I know I talked with Susie in a prior interview about how to approach this topic with our patients in a sensitive and compassionate manner. Once this topic is broached, I find many patients are looking for advice on strategies for weight loss, or potentially medications or other interventions. How do you prioritize or think about the different weight loss strategies or treatments with your patients, and how do you think about the way that you recommend these different treatments or not? Dr Mollan: Yeah. I think that's a really great question because we sort of stray here into a specialty that we have not been trained in. One thing I definitely ask my patients: if they've been on a weight loss journey before, and what's worked for them and what's not worked for them. And within our different healthcare systems, we have access to different tiers of weight management approaches. But for the person sitting in front of me, that possibly there may be a long journey to access more professional care, it's about understanding. iIs there things that are free, such as, we have some apps in the National Health Service which are weight management applications where they can actually just start putting in their calories, their daily calorie intake. And those apps can be quite helpful and guiding in terms of targeting areas, but also informing the patient of what types of foods to avoid in their diet and what types of foods to include in their diet. And with some of the programs that are completely complementary, they also sometimes add on things about exercise. But I think it is a really difficult thing to manage as, say, an ophthalmologist or a neurologist, mainly because it's not our area of expertise. And I think we've all got to find, in our local hospitals and healthcare systems, those pathways where the patients may be able to access nutritional support, and sort of behavioral lifestyle therapy support, all the way through to the new medications for weight loss; and also for some people, bariatric surgery pathways. It's a tricky topic. Dr Nevel: So how should we counsel our patients about what to expect in the future in terms of visual outcomes? Dr Chen: I think a lot of that depends on the degree of papilledema when they present. If a patient comes in with grade five papilledema, that fulminant IIH that Dr Mollan had mentioned, these patients can have very severe vision loss. And even if we treat them very aggressively with high-dose medications and urgent surgical interventions, sometimes they can have permanent vision loss. And so, we counsel them that, you know, there's a strong chance that they're going to have a good amount of vision loss. But some patients, we're very surprised and we get a lot of vision back. So, we kind of set expectations, but we're cautiously optimistic that we can get vision back. If a patient presents with more mild papilledema like grade one or two papilledema, they're most likely not going to have any permanent vision loss as long as we're treating them, we're monitoring their vision, they're coming to their follow-ups. They tend to do very well from a vision perspective. Dr Nevel: That's great, thank you. And you know, ties into what you said earlier about really making sure that, you know, we create good- as with any patient, but good physician-patient relationships so that they, you know, trust us and they come to follow up so we can really monitor their vision appropriately. What do you think is going on in research in this area that's exciting? What do you think one of the next breakthroughs or thing that we need to understand the most about treatment and monitoring of IIH? Dr Chen: I think surgically, venous sinus stenting is going to probably take over the bulk of surgeries. We still need that randomized clinical trial, but we have some amazing outcomes with venous sinus stenting. And there's many efforts on randomized clinical trials for venous sinus stenting. So we'll have those results soon. From a medical standpoint, Dr Mollan can actually say, actually, more about this. Dr Mollan: I completely agree. The GLP-1 receptor agonists, the twofold prong approach: one is the weight loss where these patients, you know, have significant weight loss to put their disease into remission; and the other side of it is whether certain GLP-1s have the ability to reduce intracranial pressure. So, a phase 2 study that we undertook here in Birmingham did show that we were able to reduce intracranial pressure, but we don't think it's a class effect. So, I think the sort of big breakthrough will be looking at novel therapies like xenotide and other drugs that, say, work on the proximal kidney tubule. Are they able to reduce intracranial pressure directly? And I think we are on the cusp of a real breakthrough for this disease. Dr Nevel: Great. Thank you so much for chatting with me today. And I really learned a lot, appreciated the opportunity. I hope our listeners learned something today, too. So again, today I've been interviewing Drs John Chen and Susan Mollan about their article on treatment and monitoring of idiopathic intracranial hypertension, which appears in the most recent issue of Continuum on disorders of CSF dynamics. Be sure to check out Continuum Audio episodes from this and other issues. And thank you to our listeners for joining us today. Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.
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Continuum Audio features conversations with the guest editors and authors of Continuum: Lifelong Learning in Neurology, the premier topic-based neurology clinical review and CME journal from the American Academy of Neurology. AAN members can earn CME for listening to interviews for review articles and completing the evaluation on the AAN’s Online Learning Center.
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