Mount Sinai neurointensivist Dr. Spyridoula Tsetsou provides an overview of intraoperative neuromonitoring. Following that, she discusses the different types of tests that can be performed, how they can be applied to specific neurosurgical procedures, and special considerations to take when utilizing intraoperative neuromonitoring.
Okay so uh continuing with our outstanding lecture series it's really been good from Critical Care Spirit Doula Tetsu who I I feel like I've known for many years and that's probably because it seems like her education has really taken many years. If you look at the number of fellowships I'm sure this is some sort of national record, maybe international record. And each one is more impressive than the next. Um She has her university and medical degree from University of Athens, a residency in Lausanne as well as her E. G. Fellowship. Um She did clinical research there uh spent some time in Utah. Uh and and and when she was with us I thought she was going to become join us. I hope that she was gonna join us as an attending right after her neural critical care fellowship. So I was pretty surprised when she told me she was going to at mass General for her eye on fellowship. But she assured me that she intended to come back and she was true to her word. So we're very happy that she did. Um and today we get to hear from you so welcome back spirit! Even better. Something. Uh do you see my screen? We do. Okay, perfect. Let me open up. So thank you very much for having me back. And then today we are uh I'm going to talk to you about the neurophysiology in the in the war. Right. So first I have no disclosures and what we're going to talk about today is mainly definitions, right? What is um what is the role of neurophysiology in the world? How we can do it? How is helpful in some specific procedures and then of course some special considerations. So to start that. So what is I am. Right so the american clinical, your official of society uh states that the I am the neurophysiology intra operative near monitoring. It's very important for assessing the integrity of neural structures for making the surgery safer and for helping identify the neural structures during the surgery. So it's a useful very uh important way to help uh you the surgeons to create a path of reception to identify and monitor the integrity of the nervous system throughout the procedure. And uh it's being used not only by your surgery but by multiple different specialties such as orthopedics, vascular surgeons, plastics, uh cardiothoracic and so on. So uh what we do right? How we can uh what does do have available in the world? Uh Classically what we have is the E. G. That's like being there for all times. Right? And the dog later on like the electrical discography. Very evasive E. G. Uh Some of the sensory evoked potentials, the motor evoked potentials. Either the wave recorded in the level of the spine or the majestic recorded in the muscles that brings the auditory evoked potentials uh E. M. G. Free or triggered an entertainer recording. These are the tests then for every procedure we use different combination and different approach in order to have either monitor or mapping or both. And that's what we're going to discuss more and we're gonna go more in detail in a specific kind of procedures what we use and how neurophysiology can be or not helpful. Uh So uh to start going classically uh your officials like I um is used in cerebrovascular surgery and typically in the clipping of cerebral aneurysms and CS to start on with cerebral aneurysms. Uh Typically what we do is uh more terrible potentials, transplantable motoring potentials and S. E. C. Ps. Uh upper and lower extremities of course, based on the location of the annual we're gonna sample more muscles in the upper or the lower respectively and faced. What is important. Also again based on the location of the level of the of the aneurysm we can extend our monitoring to uh to general Mississippi's or going to brainstorm about potentials. We can also arrange a long tongue uh traditional mps based on the location within uh monitor or whatever needed. Right uh important thing. Also during the cerebral aneurysm clipping is the E. G. Monitoring both for high provision but also for monitoring for eventual uh seizures And to show wants some examples. For example here is a case uh that the permanent uh NMC aneurysm here we see 1057 permanently post placed and we have here uh here's the face and then the upper extremity lower extremity muscles. We see that we have motor evoked potentials. Very nice polyphasic create amplitude, reproducible and exactly the same as the baseline. However, seven minutes later we see that with the same uh stimulus intensity, we lose the motor evoked potentials almost everywhere except of uh right D. Eight. And that's Resistent. And even when we go up to 200, like when we increase almost 100 both uh the stimulation intensity we can get some but say it's not good enough. And then after discussion, of course with a surgeon, we can the surgeon decided to remove the clip and reposition. And then motor evoked potentials are back to normal baseline with a baseline, 100 volt of intensity. So That was something showing that I am is usually right in this kind of schedule. Is. However, a recent paper of 2020 in general neurosurgery showed that I am is not That may be helpful in this kind of procedure showing that in order to prevent symptomatic infection. Uh the possibility phase you need the number needed to treat 43 when they compare people that they're having. I remember we don't have um uh and also like for permanent deficits. Again the number needed to treat was 65. We're going to discuss later on why this status can be a contradictory because we have results showing but it's useful but it's not. The big issue is also how we interpret our data and how the neurophysiologist accurately communicate uh with the surgeon. Another classic indication of uh I am from all the times is the C. A. And there are a lot of studies regarding C. A. And I am mainly with I. E. G. That was classic from the seventies that was used. And all the studies have shown that um that a major engine change during the clamping of the karate uh is related. It can be associated with a much higher risk of stroke. And also it has been shown that uh selective shin during the procedure based on the A. G. Slowing reduces the risk of uh intra operative stroke. And here is a nice example. I will show you more showing that that's an old like from 1996 with much less channels but we see that there's symmetric background and then after the climate there is a left slowing that improves after shunting. And here more recent examples how we can be helpful to the surgeon. Right? We have here it's a right A C a C A. You have here up is the right panel. So that is the left panel, right, left, right. And we see this symmetric, almost medical background. And here when uh the clip is on here so we start seeing that start being a slowing mainly on the on the right side, right. That persists here. It's like almost uh very slow. Like it's almost uh decrease severely the amplitude. And then after communicating these results, santa has decided to replace and the moment of the show is placed and opened the provision the backgrounds against medical patient woke up with uh no deficits. Uh So uh for say other than the E. G. That's the classic thing being done. There are many centres including also Montana West. There's like all the papers that they use the combination of sec e. Energy to have like meat model approach for uh for monitoring this kind of patients. There are centers that they use awake uh monitoring. They do with local anesthesia. Other they see this blood blood flow measurement older uh they would drink the Kurdistan pressure monitor or even the news. There is no um that comparison between which is more effective. It's really based on every institution preference and uh to move all classic also um is being used in a brain to more reception in senatorial surgery. And this is a very uh nice and developing film because it's not only used for monitoring but also for mapping. So classically what we do what we offer and then of course in discussion with the surgeon anesthesia. Uh What we can do is the central sulcus localization and we can do a cortical modern mapping and monitoring. A sub cortical modern mapping. Uh somatosensory monitoring language and parallel function mapping and monitoring. Uh And this classic is done having basin awake and doing tests uh actually like neuropsychology test during the war. And of course the cortical activity uh monitoring and the tests that we use is the somatosensory evoked potentials. Both for the synopsis gerrymandering but also for the Central Service localization directors of cortical direct political support, local mps and the and the three MG. And uh to have a nice and certainly here for the central location because that's the first thing uh that we tend to do. You the surgeons place the eight electorate uh strip perpendicular to the presumed central focus. And we try to localize where the central soldiers. Where is the promoter? Uh huh. The present report central area. And first if the strip is uh well placed, we're supposed to be and if it's well placed we're supposed to be you have to see the face reversal between the pre and post central area here. We know that from 1 to 4, as you can see here, it's post central because we have the nine nice and 20. And here we have uh 20. So it's positive potential and it's uh post uh interior pre central. So you know that your central service between four and five and then important thing to know. So then after we proceed with monitor and mapping, uh either with direct simulation or by using also during the procedure, uh decide that we can stimulate from its electrode if it's close to uh hunt entities or whatever and then you can have a continuous monitoring during the procedure. Uh important thing to know is that even if the strip is moved Oregon, if it's not uh consider selfish anymore for the morning. Two important nothing. It's very important to keep it because it's important uh to monitor procedures in this kind of procedures. It has been shown that uh reparative seizures happen at 4.6% in patients with big uh pandora ultimas, even if they were seizure night. And that's because the uh stimulation percent increases the risk of seizures by the prison procedure threshold. And then here you can see a nice uh seizure captured by the ecowas that can be treated immediately. What is, you know, how they could we want uh see decisions of the service charges and then it's associated with increased mobility. Another a domain that uh I am extremely helpful is the posterior forces called base brings in surgery uh and mainly for the Crandall. Next monitoring, right? So we can monitor the nerve integrity. You can find a way where to entry safeway and then we can have a continuous monitoring with AMG activity after the mapping during the section. Again, what we use, classic, the same recipes, enemies free and triggered MG. And then of course, it's like we want to have a panel monitoring uh classically we can do the brings them a little bit of potential. We can have two german electricity's being uh huh reflects. Is and then we can monitor almost every every cranial nerve. Uh as you can see here here is the muscles that we can sample. And then by doing the trick it N. G. We can monitor and map uh almost every cranial cranial nerve. And the important thing to mention is that honesty is a big part a big help of the uh for the neurophysiologist right? Because um they can take us other than adjusting the medication that we want. Also for the channel 10 for example they place a specific institute with electorates that has to be placed exactly between the vocal cords so that their health is very useful and they were for that. And that says a sure that it stays in place and where it's supposed to be. And the city tubes, They have electorates both sides, left and right, that they can be used both for stimulation recording so we can have the continues uh Criminal 10th monitor during the procedure here. You see. We have placed 80 Toobin who have nice recordings both from the left and the right side. Uh huh. Of course the most plastic use of I am. And I think the more old if it's not for the vascular center, it's a spine surgeries and uh even if it's uh the compressive surgery, spine deformity, traumatic spinal cord tumor resection, introduced to examine your spinal cord tumor sections classically, um is uh present with this case. And uh what uh usually just uh can do is CCPS and entities forcefully and triggered the MG. Again, different kinds of Mississippi student, a little bitty, for example, based on the location of uh the surgery we use e g uh limited channels, but it's important to judge the anesthesia depth and of course the waves and also calling mapping again based on on the procedure. Uh interestingly again for us, I spoke earlier for the aneurysm. So the sons are conflicting if I am is useful or not, there is an I study was done in 2000 and 13 that showed that yes, I am is useful in the spine surgeries and and cost effective about that. Uh They saw that calculating who is gonna uh the money that they're being uh spend it uh for the neurological deficit life, of course, sorry, lifetime cost for possible political uh deficits. There were much less than people that they had the surgery. Amusing irony. However, Uh recently, uh in 2017, very recently, uh the guidelines for the use of ecological monitoring that was presented in the uh and your surgeon surgery. So the confidence showed that, yes, I am uh is helpful uh for identified integrity of the spinal cord and nervous system and it should be used for that. However, they showed that there is no improvement in the universal outcome when we use I am and it's not cost effective. Again, that was done in 1970. And the other studies completing again, um there are like a lot of uh things that we should improve in order to show that what we do uh indeed useful. Uh I am also it's been used of course in multiple the procedures that we're not gonna go in detail now, but classic grills for the performer surgeries. And of course for the epilepsy surgery, which is like uh like a big part of uh this uh procedures and of course other than the neurosurgical part is using for from the vascular for abdominal. And it was prepared for spinal cord uh schema monitor and cardiothoracic surgery especially when they uh for the bypass when they want to have like uh cerebral silence for your protection. Uh So I will talk about now for uh some special consideration that we have to have in mind. Right why we may have all these conflicting results to see if it's useful? Not useful classically. Uh The big issue is the alarm criteria. So what we consider normal and when we when we uh say something to the surgeon or not for the S. E. C. Ps. What was classically considered as a long criteria that we should further escalate is the reduction by 50% of the amplitude or 10% of propagation of the agency. However, it's been shown that this is not enough and maybe it's too late. Um So last year, uh a year and a half ago was published. The new guidelines trying to further expand the criteria in order to capture more cases. And now what we said, any visually obvious reduction in the amplitude is considered alarming, especially if it's reproducible, focal and abrupt. And when we say reproducible, it's very important. They showed the different levels of reproducibility in the potential uh when it's like exactly reproducible, like in multiple uh trials, then we know it's real, even if It's not 50% for example, uh and then we have to alert and further escalate similarly. Similarly, uh the NDP is also like, what are the criteria for for the motor evoked potential? Um For the D wave, it's more uh standard, it's 50% reduction they omitted and that's it for the majestic mps. There is no standard consensus. So their studies saying yeah it should be completely disappeared. Other that use the 80% reduction in the amplitude. Others they say if you have to visit threshold stimulus intensity and that 100 but again it's randomly. And then other they can say that any decrease in the duration or complex if the Muslims can be worrisome. So as you can see all these conflicting results come from. The studies also come because uh the alarm criteria are very variable and of the standard size. Another also big uh confound er for the RMS anesthesia. So we have to be aware. Got an aesthetic should be used for every procedure in order of course to have the better level of sedation based on the profile of every patient. But uh having been your physiological tests being interpret able and that can be hard sometimes especially with a multimodal approach and by using different kinds of uh tests. Uh that's why anesthesia is a very big help uh in this uh in this type of uh monitoring and classically for example for the G would don't like probable of course because it's going to have like more like a presentation. It will be hard process for symmetries we prefer in election allegiance or need to oxide on the opposite for the any peace and sgps drop offline opiates are good. Uh But however you don't want high dose of ketamine or presidents because they're going to be a lot your threshold and you won't know if it's the sedation or or a natural problem. Of course for the motor of potential MG. Uh Paralysis is not recommended unless needed. From surgical perspective. Sub cortical level potentials like the brains and the auditory potentials are not affected by any like they are very resistant to any type of anesthesia because of course they're supportive. So the question is like what do we do? Like do we do or not? I am finally if it's useful or not useful and my answer would be that we really need to standardize our techniques and maybe the interpretation. I think it's a work between neurophysiology insurgent to figure out if that is something useful and cost effective or not. Uh And then I believe that it is and we have shown many examples shows but we have to be consistent and show how we can be helpful. Uh And that it's been called and work with A. C. N. S. Like american uh clinton official society and the international uh officially society and clinical trials be designed uh accordingly. And that's it for today.