Well, thank you for inviting me to speak. My name is Uzma Samadhani, and I'm going to be presenting Neurosurgery in Press for Trauma, and what I'm going to talk about today is middle meningeal artery embolization for chronic subdural. I think this is a very hot topic. Some of us who haven't currently been doing this procedure are wondering if we're missing out. Others of us who have been doing it want to make sure that we understand the indications and that we know which patients should be getting it, and how well accepted the evidence is that supports it. So I'll be presenting that. I'm at University of Minnesota. I'm also in private practice, and I work at the VA. These are my disclosures. None of them are actually relevant for the purposes of this talk, other than I will be presenting one trial that's sponsored by Medtronic, however, I'm not affiliated with that division or branch of Medtronic, nor have I ever received funding from them. So basically, this is the problem, chronic subdural. We all know this. All neurosurgeons see lots of these cases. We tend to think of these cases as relatively easier to treat, but the reality is that these patients are generally sicker than patients with brain tumors. They may be in the hospital longer than a brain tumor patient. In the VA system, at least, the total stay in the VA was greater than a week versus less than a week for a tumor. They have an 11% to 20% recurrence rate. A paper just came out in Journal of Neurosurgery this week, basically the newest finished study showing a 19% recurrence rate after surgery, so that's consistent with prior studies. The one-year mortality in the VA system is 32%, and in the brand-new finished study, it was 15%. So in any event, the one-year mortality is pretty high from a chronic subdural. The mean survival in the VA system is 4.4 years versus six years expected survival based on actuarial tables. So it's a real problem, and it's growing in incidence. This is from a paper that our lab published, basically showing that as the population ages, the incidence of chronic subdural is rising, and that number is expected to continue to rise, although with COVID, it's unclear that the aging population will continue to have an increased life expectancy. But it's still the case in other countries. It's not so much in the United States anymore. One of the largest studies that has been published about middle meningeal artery embolization for chronic subdural, center experience of 154 consecutive embolizations, of whom 138 had data that they were able to include in the study, and obviously it was a multicenter retrospective analysis. And these authors were the investigators at multiple different centers. And basically there were 15 hospitals that pooled their cases. The cases were collected between July 2018 and 2019, and there was no standard protocol by which physicians decided whether or not the patient should undergo middle meningeal artery embolization. Generally speaking, for patients that had midline shift greater than five millimeters and significant symptoms, conventional drainage procedures were performed, which consisted of either craniostomy or craniotomy or other sort of surgical, conventional surgical treatments. And for patients who had no symptoms or no midline shift, observation was performed. So it was really the patients in the middle, the patients who had clinical symptoms and or midline shift and or recurrence that were candidates for middle meningeal artery embolization. The embolizations were performed by angio via the femoral or radial artery to the main trunk of the middle meningeal, avoiding the lacrimal or petrous branches because those could be the ones responsible for causing any particular deficit. So of the patients who underwent middle meningeal artery embolization, some of them did not have any imaging afterwards, and so therefore they were excluded, 148 left, 10 of these were lost to follow up. And the question is as well, were they lost to follow up because they had a poor outcome? That's unclear. In any event, 138 were included in the study. The primary outcome measure was proportion of patients who required additional surgical treatment after the index treatment. And an additional, so there was one clinical primary outcome measure and a radiographic primary outcome measure was the proportion of patients with greater than 50% thickness reduction on imaging within 90 days or at last follow up. And then there were a variety of secondary outcome measures, including hemorrhagic or ischemic complications, cranial neuropathy, such as blindness or facial nerve palsy, abducens palsy has also been described after this procedure, access related complications, mortality, length of hospital stay, NIHSS, the stroke scale score or modified Rankin scale score at last follow up. And then finally, the radiographic outcomes of chronic subdural hemorrhage thickness on last follow up, and it was compared among the different embolization materials to determine if there was any superiority among those. And this table from that paper basically shows that the majority of patients actually still had general anesthesia. Sorry, not the majority, a large percentage of the patients still had general anesthesia at 46%. The majority had MAC at 54%. The majority did receive heparin, and the procedures were not short. The mean was 66.3 minutes. So actually, that's longer than burr holes or small craniostomy in most people's hands. The types of materials that were used for embolization included liquid embolic, particles and coils, just particles or just coils. And then the catheter position before embolization is important because you want to avoid these extra lacrimal and parietal branches, and you want to make sure to embolize the frontal and parietal branches. The principle behind this is that you keep the chronic subdural from revascularizing after it's formed or from vascularizing after it is formed. And so it's important to embolize those branches. Dangerous collaterals were seen in 10%. And technical success, which means the vessels were able to be embolized, was achieved in 97% of patients. One of the weaknesses of this study is that it was comprised of 70% white and 71% male participants. The other features of the baseline patient characteristics are shown in the table. The mean age was 70 years approximately. 48% of patients did have a prior subdural, so this was a recurrence for many of the patients who participated in this study. And many of them had had prior surgery with craniotomy or burr holes. A few had had SEPs as well. And a certain percentage of the patients were also on anticoagulants or antiplatelets, which is not surprising given the nature of this population. The mean NIH stroke scale score was only 1, and the mean modified Rankin scale score was only 1.3. So basically, most patients were relatively asymptomatic. So just as a reminder, the NIH stroke scale, if you're scoring a 0 or 1, that means you have no symptoms on each of these 11 parameters. So those patients, in other words, are basically neurologically non-focal. And a score of 1 means you have one symptom on all of these parameters. So in this retrospective study over a year, 30 patients improved in NIH stroke scale, but 79 had no difference. The majority had no difference. And the reason for that is that they started out relatively non-focal prior to beginning the study. 71 out of 104 patients were RS, modified Rankin scale score, 0 or 1 to start with. So that means that they had either no symptoms or no significant disability. So a majority of patients who participated in these retrospective analyses were asymptomatic or relatively less symptomatic, I should say. As far as outcomes, 9 of 138 patients required additional surgery, 44 improved in modified Rankin scale score, and 46 had no difference. So basically, the table, table 4, essentially shows that the length of hospital stay was only two days. So that's relatively short. Symptomatic subdural hemorrhage increase was seen in 7 patients, or 6.3%. Other symptoms were seen in smaller percentages. Mortality was 6 or 4.4%, so which is relatively low. Need for retreatment, again, was 9 out of 138 patients, which is less than has been reported in the literature in the past. So compared to historical controls, it appears that this series of patients had a lower risk for need for treatment for recurrence. The NIH scale stroke score did not improve by very much, but that's because it started out relatively normal, and the follow-up was available in more than half of the patients at 90 days. The modified Rankin scale score, again, did not improve very much. The majority of patients had no difference, and that's because they started out relatively asymptomatic. And what you see in figure 3 from that paper here is that the preoperative scale score for modified Rankin was 0 in a large number of patients, 41 patients, and it was 0 in 66 patients at 90 days of the follow-up. So it appears that a substantive percentage of patients didn't have room for improvement. The second outcome measure for this study was radiographic outcome, and what we see is that there was a decrease in thickness of the subdural from admission of a mean of 9 millimeters and a percentage of 71 percent. So 91 percent of patients had an improvement, 4 percent had no difference, and 5 percent had worsening. And approximately 31 percent or 32 percent had 100 percent improvement, and 52 percent had greater than 70 percent improvement. So it seems that a majority of patients seem to have improvement. Whether that's better than the natural history for patients selected specifically from that middle group of patients requiring treatment is unclear at this point. So the problem is that when you select a group of patients to receive this procedure, one doesn't really know whether they're better than baseline if they had not received the procedure, and so that's sort of the next step. Table 6 basically shows a summary of all of the primary outcome measures. So subdural hemorrhage thickness was a radiographic outcome measure, NIH scale stroke score, and modified Rankin scale score. And you can see the number of patients who were able to follow up at each of the time intervals, 24 hours, 2 weeks, 6 weeks, and 90 days, and a substantive number of patients were able to follow up. The subdural thickness was very low in patients at 90 days, the NIH scale stroke score was down to 0.2, and the modified Rankin scale stroke score was down to 0.7. Each of these was statistically significant in the difference between pre-op and last known follow-up for all of the patients in that study. So I guess that we are left with, after this review of retrospective cases, we are left with a question of whether this is better than the natural history of subdural hemorrhage treated without embolization. And because that question is so pressing, there are 15 studies that are currently either ongoing, one was recently completed, that was a 6-patient study at Cornell, that essentially are asking the question of whether embolization is better than conservative management or conventional management for treatment of chronic subdural. So just to review a few of these trials, the one that's sponsored by BALT, which is a French company that makes an embolization agent called Squid, that is essentially conducting a study at 24 sites in the United States and France. The lead sites in the United States are Stony Brook and SEMS Murphy. They began enrollment in December of 2020, and they planned 228 patients. Here, the inclusion criteria, again, are modified Rankin scale score of 0 or 1. So relatively less symptomatic patients. Chronic subdural has to be greater than 10 millimeters. The patient has to be symptomatic. Exclusion criteria are going to be prior crani or burr hole. So that is different from what's reported in the literature for the patient groups that have been studied so far, because they are going to specifically exclude recurrent subdurals, essentially, which was a majority of patients or a large number of patients in the prior studies. And the trial is going to look at medical and surgical management versus the same plus embolization of the MMA. The primary outcome measures are residual or reaccumulation of subdural, reoperation, and major neurologic morbidity or death. So that trial is ongoing. It has started enrolling, and there are a number of sites that are actively enrolling to investigate that question. A second trial, also sponsored by a company that makes the embolic material, this one is sponsored by Medtronic, and it's investigating the Onyx liquid embolic system. It's enrolling 600 patients. The lead sites are New York Presbyterian and Buffalo. Here, the inclusion criteria are a little more broad. It goes up to a modified Rankin scale score anywhere less than three. It includes chronic or subacute subdurals, and the patients are randomized to four different groups, surgery, surgery plus embolization, observation, and embolization alone. The primary outcome measure is the incidence of recurrence requiring reintervention, and the secondary outcome measures are readmission, hematoma volume, thickness, midline shift, and safety. So both of these large trials are being conducted at multiple centers, more than 10 centers each, and both of them are sponsored by the companies that make the embolic agents. It'll be interesting to see if they demonstrate that this is an improvement over the standard care that we have that currently has approximately a 15% to 20% recurrence rate. And the final trial that I'll discuss of the 15 trials on clinicaltrials.gov is the MProtect trial. This is embolization of the middle meningeal artery for prevention of chronic subdural recurrence in high-risk patients. It's being conducted in France at multiple centers. It's standard surgical care with or without embolization to prevent recurrence, 342 patients. It's open label, and it's publicly funded. It's not funded by one of the companies that make embolic agents. So I think at the end of the day, for those of us who are already doing this procedure, I think it's interesting to continue to do it to find out whether or not it's clinically indicated. For those of us who are not doing this procedure, that's probably also okay, because we don't yet know whether or not this has improved outcomes over the natural history of chronic subdural. Chronic subdural, I think, is something that we as neurosurgeons tend to think of as having relatively good outcomes. But actually, the numbers suggest that in the past, there's a high recurrence rate and a high mortality after this condition. I'm happy to take questions. You can always email me or reach me on Twitter. My email is uzma.samadhani.com. My Twitter is at Dr. Samadhani. Thank you.

neurosurgeon

middle meningeal artery embolization

chronic subdural

retrospective analysis

subdural thickness