Latest / CRITKNOW / Beyond the Data: Middle Meningeal Artery Embolization
Transcript
- Ramesh: Hi everyone, welcome to our next episode of the CritNO podcast. This session this time is going to be beyond the evidence. I think last podcast we talked about the stem trial. Today we have an expert in this particular area, Dr. Srinivas Paramesivan, who's a senior consultant neurosurgeon at Apollo Hospital, Green's Road. He's also a senior endovascular neurosurgeon who does both. trained in New York for his endovascular therapy and has done quite a bit of this MMA embolization in the recent past. So it's a pleasure to have you Dr. Srinivasan with us and look forward to getting your viewpoints on the STEM trial and where this strategy actually stands at this point of time. So welcome to our podcast Bharath Kumar: you Ramesh: Dr. Srinivasan. Srinivasan Paramasivam: Hello Ramesh and hello Bharat. Thanks for having me. It's my pleasure being here and I will share my views on the metal meningial artery embolization for chronic subdural hematoma, which is a path breaking newer treatment technology that we have today. And I am so excited to be here. Thank you. Ramesh: Thank you. So the first question Bharath Kumar: Thank you. Ramesh: Dr. Srinivasan is could you just tell us the rationale of why the strategy actually evolved in terms of embellishing the MMA for chronic STH. Srinivasan Paramasivam: Yes, when we were students, Bharath Kumar: Thanks. Srinivasan Paramasivam: we were of the thought or we were taught in the medical school that chronic subdural hematoma happened because of a vein rupture. And we all Ramesh: Mm-hmm. Srinivasan Paramasivam: believe that it is an kind of a subacute event or a slow collection of fluid because of the venous bleed. But then the entire thought process changed understanding the pathophysiology of this disease. It is actually a small hematoma that forms after Trivial trauma practically a patient may not even remember the trauma. Practically, they get into a car, they bump their head, or they have a little slip, they shake their head. A small bleed happens in a non-potential space that is between the dura and the arachnoid membrane. That is where the bleed happens, and the body tries to heal it by forming an inflammatory response to it. And during this inflammatory process, what happens is it forms a neo membrane. And as with any inflammatory process in neo membrane, a new blood vessels formed, and these new blood vessels are quite leaky. And these leaky blood vessels, as they try to heal, they leak more fluid and blood into the membrane, and subsequently, a collection forms, and the new collection is again induces new inflammation, and the process goes on and on to produce a low-grade inflammatory process, which is facilitated by factors like. Vascular endothelial growth factors, tissue plasminogen activator, and all this leading to microbleeds, and this recycling process leads to subdural hematoma. This led to the understanding that this is due to a leaky membrane over a period of time collecting blood. And all these bleed, fortunately for us, comes from the covering, that is from the Dura. Because Dura is one structure which just has a mechanical support, it doesn't have any function, but it is very, very vascular structure. Very pain sensitive, very vascular structure. So this is due to this, and once we block the blood supply to this membrane, we are able to completely eliminate the subdural hematoma. I tell my patients it is more like closing a tap. When we do conventional Bharath Kumar: Yeah. Srinivasan Paramasivam: treatment like burrhole tapping, we are like you know mopping the floor. This is like going in and closing the tap. And once we do that, the subdural hematoma practically disappears over a period of time. Bharath Kumar: Thanks, thanks, Srinivas, for that excellent summary of the pathophysiology. I think it's fascinating. And it's also interesting to see how you said how the understanding has changed from your medical school days to current knowledge. I think that's also been the case with the trials. In our podcast, when we recorded our podcast last week, we reviewed three trials in some details, the STEM trial, the EMBLICE, and the MAGIC-MT trial, which evaluated middle menagerie artery embolization. Of course, used two of the trials used ONIX and other one used QUID. We also went through some of the limitations of those trials, but the consistent message that seemed to be emerging in all of them was that there is some benefit of embolizing the middle menagerie artery. Even though in the industry driven trials, the benefits seem to be larger than the academic trial, but the signal seemed to be sort of consistent. So I wanted to get your thoughts on how you see the literature evolving and also your specific thoughts on these three trials and how it is sort of influencing your practice. Srinivasan Paramasivam: Yeah, anecdotally, like there are multiple evidences to show that I mean there is benefit with middle meningeal artery embolization. That's when, based on those facts, only these trials were designed. fortunately or unfortunately, a lot of them are industry-driven trials. But for the fact that we have to understand the history with middle meningal artery embolization, it dates back as early as two thousand six in Japan when group of neurosurgeons thought that We could embolize the middle meningeal artery for a patient who had repeated hemorrhages. After five surgical tappings, the patient kept having recollections and they thought we would embolize, and that worked wonders. And that's when the seed of MMA embolization started. But then we didn't have dedicated devices, there was no large takers on it. But then subsequently, we for patients with coaglopathy. Of late, we are getting a lot of patients with recent cardiac stents, patients with the anticoagulations, with the antiplatelets on board, patients waiting for liver transplant with liver dysfunction. These are the patients they used it as an adjunct along with the conventional treatment. And it worked very well. And people thought we should do a trial. And luckily, the companies came forward to sponsor these trials because, as you know, the trial involves a lot of financial implications as well. So these trials like the embolized, which was done predominantly in the US, the SEM trial done in US and Europe, the magic empty trial done in China with the large numbers, like you know, somewhere between 300 to 700 patients were enrolled, and then the membrane trial with N-butylsynacrylate. All these have pointed, as you rightly said Barat, the indicators are that this therapy is effective and it has to be used judiciously And it has to be used in selected patients for best results. The good news is that the recurrence rate is very, very low when we use middle meningal artery embolization compared to the conventional treatment. Just remember these two numbers. For a conventional therapy, the recurrence rate is somewhere between 15 to 20 percent. Whereas with middle meningal artery embolization is about two to three percent. It is as low as that. So I mean that that's how the trials have shown and that's our experience as well. Ramesh: Great, great, great, great, great, and the group that got surgery had a smaller difference and the overall difference you mentioned the member numbers were substantially apart. So where do you see the indication of mm embolization? Is it in a surgical candidate or a candidate where you have deemed them non-surgical and how do you go about choosing these patients? Srinivasan Paramasivam: See, in general, whenever we look at these trials, we have to look at them quite cautiously, especially when we are looking at the subgroup analysis. for example, if you're selecting somebody only for MMA embolization, the results are going be great because these are subset of patients who have a smaller collection who do Bharath Kumar: Okay. Srinivasan Paramasivam: not have neurologic deficit, may or may be on antiplatelets or anticoagulation, but these patients conventionally in the past, we waited and watched on them. And then decided on the conventional treatment a little later. But of late, we have been like trying to treat them upfront. These are the subgroup Ramesh: the Srinivasan Paramasivam: of patients, so they will have wonderful results. And for patients who have large collection with the deficit, with the midline shift, obviously, we are going to go for conventional treatment, either combining with embolization or without embolization. In these subgroups of patients, obviously, they are more sicker patients. And when we combine them with embolization, obviously the redo or retreatment rates were significantly lower. That's when the difference comes. So when you have to select the patient who needs conventional treatment and who's at a high risk of recurrence, we need to identify that subgroup of patients and we treat them with MMA embolization. That is where this treatment is going to be very, very effective. Bharath Kumar: Right, I that's, I think the patient selection question as you pointed out is very, important and we'll probably circle back to that. But coming back to your point on recurrence torturumas, so the recurrence rate is very impressive, as you said, it's a nice, know, the numbers are quite impressive, but does it also translate into longer term functional outcomes? And are there any safety concerns with the procedure itself? I guess, for those two parts to the question. Srinivasan Paramasivam: Yeah, two parts to the question, right? Yeah. See, in terms of functional outcome, none of these studies talk about the exact functional outcome, say 90 degree, I mean 90 days rank and scale or outcome that we do usually with strokes. They talk about radiological cure and clinical cure, practically in a short term. The the Bharath Kumar: Correct. Srinivasan Paramasivam: matter of fact is that. Whenever they have a clinical and radiological cure, it means that they don't come into the hospital for repeated procedures. Their stay in the hospital is shorter, and their stay in the ICU is relatively much, much shorter. All these parameters practically translate into good clinical outcome. So that is what the implication. The trials have not directly taken outcome as a measure in these trials. They have mostly relied on the radiological output. And yeah, go ahead, go ahead. Sorry. Bharath Kumar: Hmm. And what? Yeah. No, no, I was going to, I was going to ask what has your experience been with respect to, because they probably come back to you for follow up. So I want to check what your experiences. Srinivasan Paramasivam: Correct. When they come for follow-up, the results are fantastic. We usually follow them at two weeks for a clinical review, and then we follow them at one month for a repeat CT scan, then two months and three months again for CT scans. And usually there is about 50% reduction in the size of the hematoma at one month. And between two to three months, that's when there is a complete resolution. And we see great results, and even in patients with antiplatelets, anticoagulants. We do not stop them right after the procedure, we in fact continue and in spite of that they have complete resolution of the hematoma and it is quite encouraging. Bharath Kumar: Right, that's good to know. Ramesh: So, Dr. Srinivasan again, so if you have a patient in front of you presence with a chronic subdural hematoma, we talked about how you decide who are candidates. by looking at them say no this is not a candidate for middlemen gelatary embolization number one and number two are there any specific findings on the CT or CT angiogram whatever it is that you look that would either make you inclined towards or away from an MMA embolization. Srinivasan Paramasivam: See, being a hybrid neurosurgeon, I mean I I do both barhole tapping and middle meningal artery embolization. So I don't have any bias towards one particular procedure. We select based on exactly the patient and the disease criteria. To me today Ramesh: Hmm. Srinivasan Paramasivam: I would not embolize a patient who has a large bleed, for example a 1.5 centimeter of bleed with a midline shift of like more than eight millimeter to a centimeter and who has got a mass effect. I will not rush into doing an embolization. Rather, I would resort to a conventional treatment of a barhole tapping. And for patients who has got significant neurologic deficit, for example, he has got an arm, leg weakness, not able to stand, and it's rapidly progressing, these are the patients. I will take him to the OR, do the barhole tapping. But one difference it has made, one difference is that in the past, for patients with multiple membranes, when we look at the CT scan with multiple layers and membranes. We did craniotomy, excision of the membrane, apart from barhole tapping. Barhole tapping alone would Ramesh: Mm-hmm. Srinivasan Paramasivam: not work. But this is a subset of patients that I feel we have made a difference. Even in patients radiologically having multiple membranes, multiple layers with varying stages of hematoma, we just do a barhole tapping, evacuate as much as possible, reduce the mass effect, bring them into a lower degree of subdural hematoma. And then we take them right away to the cath lab and do a middle meningeal artery embolization. Irrespective of the membranes, it heals well. Bharath Kumar: Right. Ramesh: So my understanding as an intern is large bleed you're more likely going to need both. In smaller bleeds with no neurological deficits or mass effects it's a call between conservative management versus MMA where now the evidence says that is a subgroup that may actually benefit based on what you said that with an MMA embolization so that we should probably be leaning towards MMA embolization unless the bleed is so small. that it's probably not cost effective to go into an MMA embolization. Is that a reasonable message that I should take as an intensivist? Srinivasan Paramasivam: A little bit different from what you just summarized. If it's a even a large bleed and it's a single cavity, you have Ramesh: Mm-hmm. Srinivasan Paramasivam: a layering of the blood just as a single cavity. I would just resort to bar hole tapping and leave them alone without any MMA embolization. But if it's a large bleed with multiple membranes, you can see membranes within the subdural and causing mass effect. And in that case, I will combine the bar hole tapping with middle meningal artery embolization. And obviously for very tiny bleeds, we even today we tend to observe, but we put the ball on the patient's coat telling them that I mean there is a possibility that it could resolve and there is a possibility that it could increase. And we periodically follow them up with the serial scans and then decide on MMA embolization. So these people fall into this extreme, fall into a category of people who will need a frequent follow-up. Bharath Kumar: Right. Ramesh: That's a fantastic nuance. So depending on the number of membranes and the number of compartments, your algorithm slightly changes even in larger bleeds. So that's a very, very nuanced interpretation of the data that I think our audience would probably learn to know. Bharath Kumar: Absolutely. Dr. Srinivas, maybe slightly shifting gears. Can you talk to us a little bit about the procedure itself and sort of what it involves and how you would go about it? Of course, I would like you to answer to an audience that is not going to be only neurosurgeons. So maybe a little bit of details on what you actually do. Srinivasan Paramasivam: Yeah, I'll just make it very simple. I mean see middle meningeal artery, you you all know that it's an artery arising from the external carotid system, which is a very, very safe artery to catheterize. And an interventionalist with the average experience can catheterize these vessels quite safely. The few points that we need to note is that this middle meningeal artery at the skull base has some collaterals. That is what one need to understand. At the petrus base, the middle meningial artery goes through the foramen spinosum and then it turns back and enters the cranial cavity and carries forward along the dura. As it enters, it gives a branch to the petrus part of the bone that involves in facial artery collateral network. If we embolize that, there is a risk of facial palsy. So one has to be distal to that, one has to be aware of those branches. The other collateral that commonly comes into play is actually the ophthalmic artery connection. There is a at the lateral wall of the orbit, there is a canal called Hartal skinal, which is invariably present, and most of the branches arising from middle meningeal go through this canal to supply only the lacrimal gland. But there are times there is a connection between this lacrimal branch and the ophthalmic artery. And in fact, this can go all the way back through the ophthalmic artery to the internal carotid artery. So we need to understand this connection and avoid it. And embolization becomes very safe once we navigate the catheter more distal to these branches and embolize them distally, avoiding any proximal reflux. And usually the middle meningal artery goes as two branches: one as a frontal branch, other one as a pareto occipital branch. So in the frontal branch, avoiding the ophthalmic, go distally into the frontal branch and embolize distal to that. Likewise in paretooxcipital branch, go distal to the facial and embolize that we are safe. So as far as the anatomy goes, I mean these are the basic simple things one need to understand. Bharath Kumar: No, I think that was very Ramesh: No, Bharath Kumar: useful. Ramesh: transitioning on from what you said, Dr. Srinivasan. So you've already mentioned the two, no, very complications that I need to be aware of as an intensivist. What are the other things that if I receive a patient in the ICU that I need to look for immediate post procedure from a monitoring point of view that you would expect us to keep an eye on? Srinivasan Paramasivam: Yeah, in general, most of these MMA embolizations, when it is small, we just treat them in the cath lab, watch them for a few hours, and we can even send them home the same day if post procedure they are fine. But unfortunately, most of these subdural hematomas happen in old age patients, and these patients have a lot of other coma bids. They have cardiac issues, they have Other systemic issues like pulmonary issues that need to be taken care of. These Ramesh: it Srinivasan Paramasivam: are the patients we bring them to the ICU for an overnight check. And in general, obviously, as with any other procedure, we go either femoral or radial, the local area needs to be checked periodically by the intensivist at least for the first six to twelve hours. And then subsequently the blood pressure monitoring becomes important because most of these patients are. hypertensive patients and some of them are diabetic, and diabetic complications should be avoided. Few hours of positioning the leg straight when we do the femoral puncture becomes extremely important, and most importantly, this subdural hematoma is extremely seizurogenic and they cause a lot of seizures in these patients. So we prophylactically give them anti-epileptic drugs, but more importantly, post-procedure, I would Insist on the intensive intensivist keeping a close watch for seizures and reacting immediately. And obviously, other general parameters and when you receive these patients, you have to specifically look for any new onset facial palsy, new onset unilateral vision loss. Those are the things you need to watch for when you receive these patients. And yeah, those are the things I could think of. Bharath Kumar: Right, right. Ramesh: Just a quick question from one of the things is, is there a BP target? Because my usual thought process as an intern is you either blocked a vessel, I don't want the blood pressure to be too low, I don't want the blood pressure to be too high immediately post any angiographic procedure. So somewhere an acceptable range for me would be anywhere between 120 to 150 systolic or something like that in my mind. I'm just thinking out loud. I don't think there are any specific guidelines for this procedure. So are there any specific targets you have in your mind? Srinivasan Paramasivam: Yeah, in general these blood vessels are blood vessels of the coverings of the brain. They do not supply any vital organ. And these are very tiny vessels and the hemodynamic change following blocking this vessels are going to be extremely, extremely minimal or insignificant. So Ramesh: Mm-hmm. Srinivasan Paramasivam: I would target a normal physiological range for that particular patient rather than anything particular for the procedure. Bharath Kumar: OK, that's Ramesh: All right. Bharath Kumar: again good to know. I want to just quickly go back to the two sort of precautions you said we should take, right? The possibility of blocking off, unintentionally blocking off the facial supply or the ophthalmic supply. So routinely, do you need to map the system, Dr. Srinivas, before you proceed? Or it's all in one sitting. You go, you start the procedure, you look at the results, the anatomy, and then straight away, how do you do that? Srinivasan Paramasivam: Yeah, that's a great question. yeah. I mean when we do the angiogram, initial angiogram, we have a certain set of proceeding with the procedure. First we would put the catheter in the external carotid artery. We take a run, we make sure we are seeing all the vessels, then we take the microcatheter into the origin of the middle meningeal, that is at the re level of ram and spinosum, we do a detailed injection. Most of the time, these vessels we do these procedures with the patient being awake or under mild sedation. So there is a risk of vasospasm. To avoid vasospasm, what we do is we inject nemodipin intraarterially. But when we keep the patient awake and inject pneumodipin, they get migraine like headaches. It's such a severe, painful Ramesh: Thank Srinivasan Paramasivam: condition. So to avoid that, we have found an alternate way. That is what we do is we inject one milligram of lidocaine. We anesthetize the endothelium of the vessel and then we inject pneumodipin, they comfortably tolerate it. After we do this, we super selectively catheterize the posterior branch, anterior branch, and just close to where we expect the collaterals, we do a more detailed little pressure injections to look for these collaterals, how robust they are filling. See, one thing we need to understand with these collaterals is that there is a flow from either side, there is a competing flow. When you put a catheter, the flow is relatively low and it may not fill your collaterals. You may be mistaken for no collaterals being there. So you need to do a little forceful injections for these collaterals to open up and show what these connections are. We understand these connections just before we embolize. There is no need for a separate procedure to understand them and then plan the procedure. We can right away start the procedure, go ahead and do the entire procedure. Bharath Kumar: I think, I mean, at least for me, I did not know the intricacies and the nuances of what you need to watch out for. So that is fascinating. Thank you. I guess the only other question that Ramesh: So the next question follows. Bharath Kumar: I had, yeah, sorry, go ahead. Yeah, go ahead, Ramesh. Ramesh: No, no, I think the other question I was going to ask is, most of these patients, like you said, Dr. Srinivasan, are already on antiplatelets or anticoagulants for other comorbidities that they have been having for over years. Procedures done, we have watched them in the ICU. I think they are doing well. So my question to you is, how do you go about deciding reinitiation of these agents? At what point do you think it is safe for us to consider reinitiation of any of their old antiplatelets or anticoagulants? Srinivasan Paramasivam: Yeah, in general, we if we plan for just middle meningeal artery embolization, for the procedure and post procedure, there is no need to stop any of their anticoagulations or antiplatelet drugs. With the patient's anticoagulation on board, we can take them off for the procedure, we can do the entire procedure. However, when we are combining with the surgical procedure like burr hole tapping. And then going for a middle meningeal artery embolization. Obviously, burrhole tapping involves cutting on the skin, drilling through the bone, and then devascularizing the dura and all these maneuvers. These structures can bleed. So, potentially, what we do is we give them antiplatelets, we sorry, we stop the antiplatelet drugs or give them platelet transfusion just before the burr hole tapping in case of a large hematoma. Do the burr hole tapping. Go for MMA embolization. Once the MMA embolization is over, we come back and restart the antiplateless. Bharath Kumar: Right, OK. Great. The one final question that I had, and then over to Ramesh to see if he has anything else, Srinivasan was to ask whether, so if a patient does end up with a recurrence, I know you said recurrence rates are low, do we, I mean, when do you consider that as a treatment failure, I guess? That's something that I was curious to know. Srinivasan Paramasivam: Yeah, in general, there are situations where we back out of embolization in certain situations where the ophthalmic artery connection is pretty huge and we are not able to navigate beyond the ophthalmic artery with the microcatheter, we would back out in that sense. It is a procedural technical failure. Okay. But even for that, we have found an alternate route. What we do is today we put the microcatheter all the way up in the parietal branch more distally. And then we have the liquid embolics like squid 12, which is a very thin fluid which can penetrate through micro vasculature, and we inject it force heart to get it all the way through the collaterals into the frontal branch and bring it all the way close to where the ophthalmic is arising and stop there. In that way, technically, we have achieved more preventing this kind of failures. However, if we do embolization and the patient has a persistent collection, say at two to three months of time that is when we call it a treatment failure or the patient becomes symptomatic. There are situations where the patient is borderline between MMA embolization and barhole tapping where we think we can get away with MMA embolization, we go ahead and do it, but then the next day patient starts developing an arm drift or a deficit. That is again considered a treatment failure. And then we go for barhole tapping in addition. Generally over overall they do quite well. These are just the situations that we have faced. Bharath Kumar: Thank you. Ramesh: And one question that just popped in my mind when you talked about the stem trial is that about 15 to 20 percent are bilateral SDHs. So I assume the algorithm for bilateral SDHs would be pretty much similar. You go to the site based on the previous, know, criteria as you basically said, know how many membranes, how many compartments, what is the site, what is the mass effect? And then you decide whether they both need embolization or no one side versus the other. Is that a fair statement to say that that's the way you deal with the bilateral SDH. Srinivasan Paramasivam: Yes. See, irrespective of the side of the subdural, our Ramesh: Okay. Srinivasan Paramasivam: protocol and paradigm is we do bilateral MMA embolization in all patients. Because the Ramesh: Okay. Srinivasan Paramasivam: dura is a very, very vascular structure. And if you understand very clearly, there is an extensive network of vessels between the right and the left. So when Ramesh: . Srinivasan Paramasivam: embolize on one side, invariably from the opposite side, the through the collateral networks it can cross and start collecting again. So our protocol is to always do a bilateral middle meningolatery embolization. Ramesh: Wow, that's another nuance Bharath Kumar: Okay. Ramesh: that I didn't realize reading the STEM paper. So that's why you are the expert Dr. Srinivasan. So that was really nice, Bharath Kumar: Haha. Srinivasan Paramasivam: Thank you. Ramesh: good to know. I think that's a different way for us to think now in terms of knowing what to expect when a chronic SDS comes to the ICU. So if you Bharath Kumar: Absolutely. Ramesh: want to ahead Bharath. Bharath Kumar: No, no, go ahead, I'm sorry. Ramesh: No, no, I'm just going to say that I don't think I have any other questions unless Bharath, you want to add anything Bharath or if Dr. Srinivasan wants to give a message for all of our audience in terms of what he would do with the next chronic, what we should do with the next chronic SDH. Bharath Kumar: No, not the training was there any other, you know, points or anything that you wanted to share with respect to this procedure? Srinivasan Paramasivam: No, I just wanted to share one clinical experience of a patient. When we started Ramesh: Mm-hmm. Srinivasan Paramasivam: doing this middle meningeal artery embolization, when we just initiated, there was one exciting patient who had a large subdural hematoma. I had a call from the liver ICU and the patient was waiting for liver transplant with significant anemia, significant coagulopathy with the factors down, and the platelets were around 50,000 odd. And the patient had a huge bleed bilaterally, and the patient was Literally going down in front of our eyes. So immediately we took the patient to the OT, replacing the factors and platelets along with blood transfusion, and then we did bilateral barhole tapping. And from doing that, immediately we took the patient down to the cat lab, embolized bilateral middle meningal artery. After that, we didn't have to give her any factors or platelets. And and she just recovered in the next couple of days she was extubated and in about three months the patient recovered well with the beautiful looking scans and in about four months the patient went in for a liver transplant and the patient is living now. So this is this is one experience that gave me all the goosebumps that I need with this procedure, saving the patient. Bharath Kumar: I mean, I think those are the stories for which we come to work, right? So that's amazing. Congratulations, especially Srinivasan Paramasivam: you're Bharath Kumar: on that particular patient. Thank you, Dr. Srinivas, for making time. This has been a superb session. think I can speak for both of us and say that we both have learned a lot. And I'm sure our audience is going to learn a lot. And this is going to be useful to neuro critical care doctors, neurosurgeons, Ramesh: Thank Dr. Srinivas and it has been a pleasure. Thank you. Bharath Kumar: anybody really involved in taking care of patients with neurological emergencies. So thank you so much for making time. It's been an absolute pleasure and honor. Thank you. Srinivasan Paramasivam: It's my pleasure being here. Thank you, but Thank you all. Bharath Kumar: Thank you.