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Thank you. I want to thank Andy and Jen for inviting me, and it’s a very great honor to be in the presence of some of the titans in this field. I want to say I have nothing to disagree with in terms of what Mark said, and Eike as well. I thought their talks were fantastic. Really today I just want to round out the discussion by presenting our case series and then going into some insights that we’ve discovered.
So, I have no disclosures.
And as I said, the objectives here are really to discuss our case series at Georgetown, the surgical technique, and then some insights. Last night, dinner was great – meeting everyone, meeting some of my heroes. It made me think a lot about the talk I was going to give, and after dinner, I went and changed everything around because of Wouter and Jürgen. I think it makes for a more interesting talk. I want to also give a shoutout to Anousheh Sayah. She’s really the quarterback of our program. None of this would have been possible without her. I consider myself very lucky to be part of a comprehensive leak program with tremendous support from Georgetown and MedStar Health.
So, this is our series – pre-publication – 26 CSF-venous fistulas over 19 months, single surgeon, single IR neuroradiologist, average follow-up about 6 months. You can see a success rate with the Bern score as well as the headache scores. No perioperative complications.
One patient had a smaller, what was felt to be questionable, fistula at the adjacent level. This patient had been transferred in with a couple of craniotomies already. I did the one CSF-venous fistula ligation, and we felt like maybe this was an ideal use case – instead of a fourth surgery, let’s bring in the embolization. So, we did have one patient that had both surgery and embolization. But consistent with what the literature shows – which is surgery is highly effective and quite durable.
At our center, like I said, we consider all the options. We are multidisciplinary. We talk with the patients about all the options – patching, embolization, surgery. We respect the patient’s preference because so many patients now come so knowledgeable about this disease process. We have noted a couple of things in our case series. One is that for the critically ill patients – and you’ve all seen these, right? Patients who have intracranial mass lesions, some near coma. Maybe we’ve diagnosed a fistula site, maybe we haven’t yet. But non-targeted patching, and then if they have a site that we identified, targeted patching, can serve as a great bridge and potentially even a cure for these really critical patients who are in the ICU. That’s something we’ve been very impressed with.
Embolization is obviously for patients who prefer a shorter or maybe no anesthesia exposure. And then, in our surgical case series, we found it to be very efficacious and very durable. So we kind of wear all those hats and think about all the different options with each patient that we see, and we go on a case-by-case basis. We found great success using that protocol.
Surgical approach – some of this has been discussed and mostly wording here. But essentially, an MIS technique like Jürgen has described. All of our venous fistulas are done through a tube, 18 mm. I go way lateral, drill the lateral aspect of the facet, drill a little bit of the pedicle, expose the dorsolateral and ventrolateral thecal sac, the entirety of the nerve root as it goes out to the thoracodorsal fascia. We cauterize the plexus, shrink the diverticulum, wrap it. So, we don’t actually ligate the nerve root, which is potentially different than how some other surgical case series have described. We do instill fibrin glue.
Minimally invasive surgery: we’ve had no neurological or other complications, rapid recovery, neural elements are preserved, and no artifact left behind. Although it sounds like there may be a solution to that drawback in terms of endovascular.
So, a couple of insights from our case series. Because so much of this is, as Peter said, the unknown and what we don’t know. And one of the things that I’ve started to see, in terms of a pattern, is that there may be a subtype. I’m really curious to continue this conversation afterwards – within CSF-venous fistulas of single-channel, high-flow venous fistulas that are oftentimes coming from the thecal sac, from the main trunk dura, and there’s a single venous channel. These patients oftentimes present with a high Bern score. Then, there are other patients who have this almost plexus of veins that branch out of the diverticulum, and that’s the other common thread here – diverticulum. And these, we feel, may be low-flow and present with a low Bern score.
This is a patient who was 86 but physiologically 66 or maybe even younger, still working as a bedside nurse, presented with these bilateral subdurals and brain sag. This is the, you can see I’m working through a tube. This is a right side, so there’s a nerve root there. I’ve dissected off the venous fistula, and there’s the fistula’s connection to the main dural trunk right there, separate from the nerve root and the diverticulum. And I think in these cases, the diverticulum probably compresses a vein against the arachnoid granulations, and so it would be an interesting study to kind of understand what that angle is between the main dural trunk, the nerve root and its origin, the diverticulum, and what it does to that triangle – to constrict and potentially give these patients the opportunity to fistulize.
After surgery, you can see vents are plumped up. Now I’m wondering, is she going to develop NPH? And that kind of goes back to the high – to – low, back to high situation that we sometimes encounter.
This is another direct fistula – or single channel fistula. This patient carried a diagnosis of Alzheimer’s for about two years. And Wouter, you’ve done a great job describing these cases of essentially aphasic for a long time. And here, just to orient you, you’ve got the left nerve root origin here. You’ve got the main trunk of the dura here, and you can see there’s a single vein going directly into the thecal sac. And you could understand how she’s got significant brain sag and a high Bern score, and we ligated that.
Then the other scenario that we see probably a little bit more commonly than the other two I’ve presented. So, this is a – switching sides again on the right. Through the tube, nerve root diverticulum being pulled, and again you have this arborizing venous plexus that’s coming off of the axilla and underneath the diverticulum and creating the fistula. So, to me, that’s sort of one area that we want to explore in Georgetown, certainly – just understanding single versus multi-channel venous fistulas and how – do they have their own pathophysiology, their own pathogenesis?
The other thing that we’ve started thinking about – and this is really fresh, just one or two cases that we’ve done. This was the most stimulating conversation that I walked away with last night, which is the use of ICG venography. Now, Jürgen has contributed brilliantly to the literature describing how you can come in from the intradural side and inject fluorescein and identify the venous fistula through the intradural route. And, you know, I come at CSF fistula work through a skull base and vascular perspective, and we use ICG all the time. I was doing a recent case of a dural AV fistula intracranial at the tentorium, and I thought nothing of using ICG to identify the leptomeningeal draining vein. And it got me wondering, why not do this on the next case that we have in terms of a venous fistula?
What we did – what we were sort of early on thinking is that the – this was a theory that I had. It has two cases, so take it with a grain of salt, but it seems to be bearing out, which is a diverticulum enhances with ICG administration and post ligation will not enhance, which suggests sort of this almost reciprocal flow of blood and CSF in the fistula, which makes sense, and that’s what we would expect.
So here is a case that we just – this was our first, and I’ll orient you again. So, the perineural venous plexus here – this is a left-sided approach, so somewhere in here would be the proximal nerve root coming out this way. The venous plexus is all around the nerve. I got a little bit excited wanting to try this, so I injected the ICG probably a little earlier than I should have because I should have done a little more work just kind of delineating the actual root. But when you look at this ICG – and we have a Kinevo microscope that allows us to do this. What you see is exactly what Jürgen expected, which is brilliant enhancement of the venous plexus. But what you need to know is a nerve root is here and a small diverticulum is here. That’s not enhancing. This patient had two suspicious levels, T9-10 and T10-11, and this was the first level that I did, and I saw no filling of the diverticulum. I went ahead and did my surgery like I always do, and then we went to the next level. And this is actually after I’ve cauterized all the par… – this is still the same level. Cauterized the veins, you can see the nerve root origin is kind of going 12:00 to 6:00 – there’s a small, maybe no real diverticulum there. Usually, by the time I’ve cauterized the veins, the diverticulum shrinks.
The next level looked far more suspicious. So now you’ve got – right there, that’s what I want to show. So, there’s the dura, nerve root, diverticulum – see how thin that looks? It’s right at the origin of the nerve root, and then what you see is this bundle of veins inserting over the shoulder of the root, right at the very thin – you can almost see through that dura.
So, this time at this level, I’ve done a little bit more work to kind of identify the veins and the nerve root, and I injected fluorescein, and this is just a startling vision – a view of what we saw. And that is, you see the vein here, you see another series of veins, maybe another one here. There’s a vein coming from here. I was not surprised to see filling in this area. This is where I expected the fistula would be, but I was really surprised at how avidly the diverticulum enhanced, which suggests that cross talk between the venous structures and the CSF structures and the diverticulum.
Afterwards, this is the skeletonized nerve root. The diverticulum has been shrunk, and before I wrapped it, I said, let me see what the ICG looks like now. Black – complete darkness. So, pretty – I mean, this is one case. We had another case that we did that was also very similar in terms of the experience that we had and what we saw. So, super excited to continue to study this phenomenon and understand CSF-venous fistulas more than we do currently.
So, in conclusion, we all recognize we’re at the frontier of CSF-venous fistulas, and I think this is such a great forum to invite collaboration between all of our high-volume centers to continue to work to understand exactly what these venous fistulas are. Thank you so much.