Evolving Techniques and Controversies in Myelography

Recently, sophisticated myelographic techniques to precisely subtype and localize CSF leaks have been developed and refined. These techniques improve the detection of various types of CSF leaks thereby enabling targeted therapies.

In this episode, Katie Grouse, MD, FAAN, speaks with Ajay A. Madhavan, MD, author of the article “Radiographic Evaluation of Spontaneous Intracranial Hypotension” 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. Madhavan is assistant professor of radiology at the Mayo Clinic in Rochester, Minnesota.

Additional Resources

Read the article: Radiographic Evaluation of Spontaneous Intracranial Hypotension

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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 Ajay Madhavan about his article on Radiographic Evaluation of Spontaneous Intracranial Hypotension, which he wrote with Dr Levi Chazen. 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 Madhavan:  Hi, thanks a lot, Katie. Yeah, so I’m Ajay Madhaven. I'm a neuroradiologist at the Mayo Clinic in Rochester, Minnesota. I did all my training here, so, I've been here for a long time. And I have a lot of interest in spinal CSF leaks, and I do a lot of that work. And so I'm really excited to be talking about this article with you.

Dr Grouse:  I'm really excited too. And in fact, it's such a pleasure to have you here talking today on this topic. I know a lot's changed in this field, and I'm sure many of our listeners are really interested in learning about the developments and imaging techniques to improve detection and treatment of CSF leaks, especially since maybe we've learned about this in training. I want to start by asking you what you think is the most important takeaway from your article.

Dr Madhavan:  Yeah, that's a great question. I think---and you kind of already alluded to it---I think the main thing is, I hope people recognize that this field has really changed a lot in the last five to ten years, through a lot of multi-institutional collaboration and also collaboration between different specialties. We've learned a lot about different types of spinal CSF leaks, how we can recognize the disease, particularly the types of myelography that we need to be using to accurately localize and treat these leaks. Those are the things that have really evolved in the last five to ten years, and they've really helped us improve these patients’ lives.

Dr Grouse:  Can you remind us of the different common types of spinal leaks that can cause spontaneous intracranial hypotension?

Dr Madhavan:  Yeah, so there are a number of different spinal CSF leaks, types, and I would say the three most common ones that really most people should try to be aware of and cognizant of are: first, ventral dural tears. So those are, like, just physical holes in the dura. And they're usually caused by little bone spurs that come from the vertebral columns. So, they're often patients who have some degenerative changes in their spine. And those are really very common. Another type of spinal CSF leak that we commonly see is a lateral dural tear. So that's like the same thing in a slightly different location. So instead of being in the front, it's off to the side of the dura laterally. And so, it's also just a hole in the dura. And then the third and most recently discovered type of spinal CSF leak is a CSF-venous fistula. So those are direct connections between the subarachnoid space and little paraspinal vein. And it took us a long time to even realize that this was a real pathology. But now that it's been recognized, we've found that this is actually quite common. So those three types of leaks are probably the three most common that we see. And there's certainly others out there, but I would say over 90% of them fall into one of those three categories.

Dr Grouse:  That's a great review, thank you. Just as another quick review, as we talk more about this topic, can you remind us of some of the most common or typical brain imaging findings that you'll see in cases of spontaneous intracranial hypotension?

Dr Madhavan:  Yeah, absolutely. So, when you do a brain MRI in a patient who has spontaneous intracranial hypotension, you will usually, though not always, see typical brain MRI abnormalities. And I kind of think of those as falling into three different categories. So, the first one I think of is dural enhancement or thickening. So that's enlargement or engorgement of the dura, the pachymeninges, and enhancement on postgadolinium imaging. So, that's kind of the first category. The second is that, when you lose spinal fluid volume, other things often expand to take up the space. So, for example, you can get distension or enlargement of the dural venous sinuses, and sometimes you can also get subdural food collections or hematomas. They can arise spontaneously. And I kind of think of those as, you know, you, you've lost the cerebrospinal fluid volume and something else is kind of filling up the space. And then the third category is called brain sagging. And that's a constellation of findings where the posterior fossa structures and the pituitary gland in the cell have become abnormal because you've lost the fluid that normally cushions those structures and causes them to float up. For example, the brain stem will sag down, the distance between the mammillary body and the ponds may become reduced. The suprasellar cistern space may be reduced such that the optic chiasm becomes very close to the pituitary gland, and the prepontine cistern may also become reduced in size. And there are various measurements that can be used to determine whether something is subtly abnormal. But just generally speaking, those are really the three categories of brain MRI abnormalities you'll see.

Dr Grouse:  That was a great review. And of course, I think in many times when we are thinking about or suspecting this diagnosis, we may be lucky to find those imaging findings to reinforce a diagnosis. Because as it turns out, after reading your article, I was really surprised to find out that in as many as 19% of cases we actually see normal brain imaging, which really was a surprise to me, I have to say. And I think that this really encompasses why spontaneous intercranial hypotension is such a difficult diagnosis to make. I think a lot of us struggle with how far to take the workup when, you know, spontaneous intercranial hypotension is clinically suspected, but multiple imaging studies are normal. Do you have any guidance on how to approach these more difficult cases?

Dr Madhavan:  So, that's a really good question. And you know, it's- as you can imagine, that's a topic that comes up in most meetings where people discuss this, and it's been a continued challenge. And so, like you said, about 19 or 20% of patients who have this disease can have a, a normal brain MRI. And we've tried to do some work to figure out why that is and how we can identify patients who still have the disease. And I can just provide, I guess, some tips that have helped me in my clinical practice. One thing is, if I ever see a patient with a normal brain MRI where this disease is clinically suspected---for example, maybe they have orthostatic headaches or other very typical symptoms and we don't know why, but their brain MRI is normal---the first thing I do is I try to look back at their old imaging. So many times, these patients who present to us at Mayo, who, when we do their MRI scan here, their brain MRI looks normal… if you really look back at imaging that they've had done elsewhere---maybe even two to three years prior---at the time their symptoms started, they actually had some abnormalities. So, I might see that a patient, two years ago, had dural enhancement that spontaneously resolved; but now they still have symptoms of SIH and they may still have a CSF leak that we can find and treat, but their brain MRI has, for whatever reason, normalized.

So, I always start by looking back at old imaging, and I found that to be very helpful. The other thing is, if you see a patient with a normal brain MRI, it's also important to look at their spine MRI because that can provide clues that might suggest that they could still have a spinal CSF leak. And the two things I look for on the spine MRI: one, if there's any extradural CSF. So, spinal fluid outside of where it's supposed to be within the confines of the subarachnoid space. And you know, really, if you see extradural CSF, you know they probably have a spinal fluid leak somewhere. Even if their brain MRI is normal, that just gives you the information that there is a dural tear probably somewhere. And so, in those patients we’ll definitely still proceed to myelography or other testing, even if they have a normal brain MRI. And then the last thing I look for is whether or not they have prominent meningeal diverticula. Patients with CSF venous fistulas almost always have one or more prominent diverticula on their spine along the nerve root sleeves. And that's probably because most of these fistulas come from nerve root sleeve diverticula. We don't completely understand the pathogenesis of CSF venous fistulas, but they're clearly associated with meningeal diverticula. So, if I see a patient who has a normal brain MRI, but I see on their spine MRI that they have many meningeal diverticula that are relatively prominent, that makes me more inclined to be a little bit more aggressive in doing myelography to find a CSF leak. And then I look at other demographic features, too. So, for example, elevated BMI and older age are associated with CSF venous fistulas. So, that can help you determine whether or not it's warranted to go on to more advanced imaging, too. So those are all just a variety of different things that we've used to help us.

Dr Grouse:  Thank you for sharing that. I wanted to go on to say that, you know, reading your article, of course, as you mentioned, you alluded to the fact there's lots of new imaging modalities out there. It was very illuminating and just an excellent resource for the options that exist and when they're useful. You did a great job summarizing it. And I encourage our readers to check out your article, to refresh themselves, update themselves on what's happened in this space. And of course, we can't summarize them all today, but I was wondering if you could possibly walk us through a hypothetical case of a patient who comes in with a history very suspicious for SIH? How would you approach this patient? Say you have gotten imaging that suggested that there is a spinal fluid leak and now you have to figure out where it is.

Dr Madhavan:  Yeah. So, you know, I think the most typical scenario it'll be a patient who has been seen by one of my excellent neurology colleagues and they've done a brain MRI and they've made the diagnosis through a combination of clinical information and brain MRI finding. And then the next thing we'll do always is, we'll obtain a spine MRI. So, I think of the purpose of the spine MRI as to determine what type of spinal fluid leak they have. On the spine MRI, if you see extradural CSF, those patients essentially always will have a dural tear. And it may be a ventral dural tear or a lateral dural tear. But if you see extradural CSF, that is pretty much what they have. And conversely, if you don't see extradural CSF---if you just see, for example, many meningeal diverticula, but you don't see anything else particularly abnormal---most of those patients have a CSF venous fistula, just common things being common.

So I use the spine MRI to determine what type of leak they have. And then the next thing I think about is, okay, I'm going to do a myelogram on this patient. How do I want to position them? Because it turns out that positioning is probably the most important factor for finding these spinal fluid leaks. You have to have the patient positioned correctly to find the leak that you're trying to localize. And so, if I suspect they have a ventral dural tear, I will always position those patients prone for their myelogram. And I might do one of many different types of myelograms. And, you know, the article talks about things like digital subtraction myelography and dynamic CT myelography. And you can find any of these leaks with any of those techniques, but you just have to have the patient positioned correctly. So, if I think I have a ventral dural tear, I’ll put them prone for the myelogram. If I think they have a lateral dural tear, I'll put them in the cubitus position for the myelogram. And also, if they- if I think they have a CSF-venous fistula, I'll also put them in the decubitus position. Obviously if you're putting them in the decubitus position, you have to decide whether it's going to be left or right side down. So that may require a two-day exam. Sometimes you don't have to; in many cases, we're able to just do everything in one day. But those are all the different factors I think about when I'm trying to determine how I'm going to work those patients up further. So, I really use the spine MRI chiefly to think about what type of leak they're going to have and how I'm going to plan the myelogram.

Dr Grouse:  That's really great. And it's, I think, really nice to emphasize how much the positioning matters in all this, which I think is not something we've been classically taught as far as the diagnosis of spinal leaks. Another thing I'm really interested in your opinion on is, you talked a lot about how to optimize and what can make you successful at diagnosis. I'm curious what you think one of the easiest mistakes to make or, you know, that we should hopefully avoid when treating patients with this disease.

Dr Madhavan:  Yeah. And I think, you know, one other thing that's been discussed a lot in this topic… you know, we've talked about the patients with a normal brain MRI. Another barrier or challenge particularly with CSF-venous fistulas is, sometimes they can be very subtle on imaging. So, it's not always you see it very definitive CSF-venous fistula where you can say, like, there's no question, that's a fistula. There are many times where we do a good-quality myelogram and we see something that looks, like, possible for a CSF venous fistula, or probable. If I had to put a number on it, maybe there's a 50 to 70% chance of real. So, in those cases, we end up wondering, like, should we treat this suspected leak? And I think one common mistake  or one thing that needs to be looked at further is, how do we handle these patients where we don't know whether the fistula is real or not? That's usually something where I will have a discussion with the patient, and I'm usually just very upfront with him about my interpretation of the imaging. I'll just tell them, we did a good-quality myelogram. You did a great job. We got good images. I don't see anything definitive, but I see this thing that I think has maybe a 60% chance of being real. And then I'll confer with one of my neurology colleagues and we'll decide whether it's worth treating that or not. And we'll just be very upfront with a patient about whether- about the likelihood of its success and what their long-term prognosis is. And oftentimes we let them make the decision. But I think that remains to be one of the big challenges is, how do we treat these patients who have suspected leaks that are not definitive on imaging.

Dr Grouse:  That sounds absolutely like an important area where there can be problems, so I appreciate that insight. I'm interested what you think in your article would come as the biggest surprise to our listeners who may not have kept up as much with all of the changes that have happened in recent years?

Dr Madhavan:  One of the things that was certainly, at least, a surprise to me as I was going through my training and learning about this topic is how diverse myelography has really become. You know, when I was a radiology resident, I learned about myelography as this thing that we've been doing for 30 to 40 years. And historically we've used myelograms just to look for degenerative changes: disc bulges, you know, disc herniations and things like that. Now that MRI is more prevalent, we don't use it as much, but it has turned out that it has a very big role in patients with spinal fluid leaks. Furthermore, something that I've learned is just how diverse these different types of myelograms have become. It used to kind of be just that a myelogram is a myelogram is a myelogram, but now we have different types of positioning, different types of equipment that we use. We vary the timing between contrast injection and imaging to optimize success for finding spinal fluid leaks. So, I think many times I talk to people who may not be as familiar with this field and they're surprised at just how diverse that has become and how sophisticated some of the various myelographic techniques have become and how much that really makes a difference in being able to accurately diagnose these patients.

Dr Grouse:  Well, I can say it was a surprise to me. Even as someone who does treat quite a few patients with this condition, I was surprised to see the breadth of different options that have become available. And then kind of a follow-up to that, what do you think the current area of controversy is in this area of diagnosis and treatment?

Dr Madhavan:  The biggest ones are ones you've sort of already alluded to. So, one big one is, how far do we go in patients who have a normal brain MRI who still have a clinical suspicion of the disease? And sometimes it's really hard, because sometimes you will find patients who clinically have a very strong case for having spontaneous intracranial hypotension. You look at them, they have very acute-onset orthostatic headaches. There's no better explanation for their symptoms that we know of. And it's hard to know what to do with those patients, because some of them want to continue to undergo diagnostic workup, but you can only do so many myelograms and you can only do so much with this diagnostic workup that requires some radiation dose before it becomes very challenging. That's a major point of just, I guess, ongoing research as to what can we do better for that subset of patients. Fortunately, it's not all of them, it's a subset of them, but I think we could help those patients better in the future as we learn more about the disease. So that's one. And the other one is treating these equivocal findings, like I discussed.  And where should our threshold be to treat a patient, and what type of treatment should we do in patients where we don't know whether a leak is real? Should we just do a very noninvasive- relatively noninvasive blood patch? Do we do an embolization where we're leaving a foreign body there? Is it worth sending those patients to surgery? Those are all unanswered questions and things that continue to spark ongoing debate.

Dr Grouse:  Do you think that there's going to be any new big breakthroughs, or even, do you know of any big developments on the horizon that we should be keeping our eyes out for?

Dr Madhavan:  You know, I think for me the biggest thing is, imaging is dramatically improving. We talked a little bit about photon counting detector CT in our article, and that's one of the newest and best techniques for imaging these patients because it has very, very high resolution, it has a lower radiation dose, it has allowed us to find leaks that we were not able to find before. And there are other high-resolution modalities that are emerging and becoming more accessible to things like cone beam CT which we do in addition to digital subtraction myelography. And on top of that, we've started to use AI-based tools to make images look a lot better. So, there are various AI algorithms that have come out that allow us to remove artifacts from imaging. They help us image patients with a bigger body habitus better without running into a lot of imaging artifacts. They help us reduce noise in imaging. They can just give us better-quality images and aid us in the diagnosis. For me as a radiologist, those are some of the most exciting things. We're finding less invasive ways with less radiation to better diagnose these patients with just better-quality imaging.

Dr Grouse:  Well, that is definitely something to be excited about. So, I just want to thank you so much for talking with us today. It's been such an interesting, informative discussion and a real privilege to talk with you about this important topic.

Dr Madhavan:  Yeah, thanks so much. I really appreciate the time to talk with you, and I look forward to seeing the article out there and hopefully getting some interesting questions.

Dr Grouse:  Again, today I've been interviewing Dr Ajay Madhavan about his article on Radiographic Evaluation of Spontaneous Intracranial Hypotension, which he wrote with Dr Levi Chasen. 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.