Thank you for the opportunity to speak. It's a privilege and not an opportunity that I get very frequently to speak to this audience. What I was asked to do was to talk about mapping and how I use it in vascular neurosurgery, but I thought I would start by just talking about how I've been asked to sort of bring vascular neurosurgery into the mapping community, and these are just some numbers from a review of Sylvian dissections I've done for Dr. Berger and Dr. Chang, either for insular gliomas or for epilepsy surgery, and you can see it's quite a large number. So how have we gotten mapping into vascular neurosurgery? Well, the fact is it's fairly uncommon, and the reason is because if you look at aneurysms, they inhabit the subarachnoid space, so they really don't violate tissue, and we pride ourselves on staying out of the brain to do most of that work, but we do use a lot of monitoring, SEP, MEP, and EEG, which I'll talk about. AVMs have a similar behavior. They tend to respect peel planes and stay out of tissue to some degree, and the same is true with cavernous malformations. So let me begin by talking about aneurysms, and I basically use neurophysiologic monitoring for all cases, and the reason I do that is because it allows you to titrate your anesthetic agent to achieve birth suppression, and that's really important for brain protection. If you can get just the right dose of anesthetic and lower the cerebral metabolic rate of the brain, you can increase tolerance for those times when you need temporary occlusion or some induced ischemia. It's also useful in detecting ischemic changes that might happen as a result of your maneuvers, either through temporary clipping or through a direct clip application, and let me show you some examples. This is a basilar aneurysm, which you can see, and below the angiograms or the imaging or the electrophysiology changes, you can see the baseline recordings. You can see what happens just with a temporary clip occlusion. Sometimes just a clip on the basilar trunk can compromise flow to a degree where the signals will change, and you can see that once the aneurysm is dissected, clipped, and then reperfused, there's a complete restoration. But it gives you an indication during that period of ischemia how much time pressure or how quickly you need to move. Here's another example. Sometimes at the basilar apex, it's very difficult to see small perforators at the back side, and so this is an adjunct to help us find a mis-perforator. So in this case, you can see the angiogram. I thought the aneurysm was nicely clipped with no problem, but you can see the loss of the MEP signals there, and that prompted me to look a little further behind the aneurysm, and I found that one of the perforators was gathered in the tips of the clip, and I corrected that and you can see restoration. This is another example of an intraoperative rupture, again at the basilar tip, showing how everything drops during those times where you've got active bleeding and temporary clips in place, and it can help guide you as you come out of that situation as to whether you've fixed things properly. Another note on this slide is just how the MEPs can sometimes be more sensitive than the SEPs, and in this particular case, the SEPs were completely unchanged, and I think that's because those perforators are so specific that if you have one that goes just to the motor fibers, you'll get a change there without a similar change in SEP. So these are some slides of our use in basilar aneurysm clippings. You can see that there are a variety of combinations of changes. You can get changes in SEP. You can get changes in MEP. You can get changes in both or neither, and so it happens during temporary clipping. It happens during permanent clipping, and so it's a very useful adjunct. For bypasses, the same sort of thing is true. We induce ischemia when we clip or occlude these vessels for our anastomosis, and it's very useful to guide the speed with which or the urgency with which we need to complete this bypass. Now for AVMs, I think it's even more important for specific ones, and that's because there are these eloquent AVMs that we have to tackle. These are areas of eloquence, and obviously, we can't map all of these, but the ones that are useful are language and motor. So with AVMs, these are some of the things that we have incorporated into our practice. Noninvasive functional imaging with fMRI and DTI. We use interoperative motor mapping with direct cortical stimulation, and then speech mapping similarly, and then I'll touch on this reorganization of eloquent function. So this was a study that we did years ago looking at functional reorganization with AVMs. These are somewhat crude now. These are magnetic source images looking at sensory function, and what we found in this review of, I think it was about 30 or so patients of ours, was that you see this kind of reorganization where the AVM here is on the right, in the right hemisphere, but you can see that there's been movement or translocation of function from the sensory area up across the central sulcus to the pre-central gyrus, and that is an example of how these AVM shift or translocate function. Here's another example from that same series of ours where this parietal AVM here moved function from this hemisphere all the way over to the contralateral hemisphere. So it can not only shift from one gyrus to the next, it can also shift from one hemisphere to the next. This functional reorganization is also seen with speech, but before I do that, this is the table showing some of those results. I wanted to make this point that it's the transrolantic AVMs, the ones that are right in the central sulcus, that seem to be the most prone to this translocation, and we observed shift in about a third of all of our patients. That was a sensory study. Motor also does the same shift, and this is a study or a case example showing examples of shifting of the motor function to the other hemisphere or throughout the hemisphere. And this is an example from one of my patients. You can see this AVM here, and when we do fMRI, you can see how the AVM is here. It shifts the function over to the opposite hemisphere. So these are important things to know up front, because when you're making these decisions about whether or not to operate on the AVM, it may change your evaluation of the patient's eloquence. This is a study from Neil Martin's group in UCLA that showed that language function also translocates. So the bottom line is that this translocation phenomena is very important with AVMs. AVMs obviously form early in development, so there's this shifting of function, and it's important particularly in making these decisions about surgery or not. This was a review of how we used language and motor mapping in about a 12-year period for AVM surgery in my practice. And just to summarize here, these are 12 patients that we included, and it was a fairly even split between language and motor mapping. And these were the ways in which it helped. Cortical preservation is important, because if you can identify where that eloquent, for example, speech function is located, you really are protective, and you can steer in many cases your resection away from that. In other cases, you have to go transcortically to get to the AVM, and that's where it guides the approach. In defining which tissue you're going to violate or transgress to get to the nidus, that information can help you select the approach or the tissue that you go through. And then finally, the extent of resection. If you're resecting and you find that you're getting closer and closer to an eloquent functional area, you can get changes, and that will impact the extent of resection. Here's a case example. This is a patient with a speech area AVM, dominant temporal lobe. You can see how we mapped initially. You can also see here that preservation of the plane of dissection between the pia and the nidus, and then going around the nidus, you can separate this fairly cleanly. These are some of the results. We achieved safe, complete resections in two-thirds of patients, and that's obviously the goal of the mapping is to make this safe. And in those cases where we didn't feel it was safe, what we did was we left the AVM in situ. We disconnected it arterially. We left it connected venously so that it's whatever residual connections it might have in eloquent areas was provided ample outflow, and then we treated it with radiosurgery. And we think that that's a fairly reasonable way to go with these eloquent AVMs. Here's an example. This is a case I did with Eddie Chang, very large frontal AVM. I'll show you here on this video. This is a young girl who was initially treated with radiosurgery. I didn't feel like this was a safe one to take out. And she was treated initially with volume stage radiosurgery, and we got a fairly good volume reduction but not a cure. And this video just shows the changes that you can induce with radiosurgery over time. Let's see if I can control this. I guess I can't. I've lost my fast-forward knob. But anyway, what this case is showing is just how this nidus is basically in the sylvian fissure and into the frontal lobe on the frontal side of the sylvian fissure. And you can see that very nice transition or transformation of the AVM from the radiosurgery. It becomes this white sclerotic nidus rather than an active hemorrhagic nidus. And it's a much different, much easier nidus to take out. And having mapped out the speech, I knew that it was off the screen there towards the bottom left and out of harm's way. And this ultimately was removed completely. I'll fast-forward that. This is a literature review that was done by my current fellow, Brian Walcott, and some colleagues in Boston, just to show that in other centers, it's also not a widely utilized technique. It's, I think, a very highly specialized technique for a very select few numbers of AVMs. But I think it has its place. It is very valuable in these kinds of cases, again, to preserve that eloquent cortex, guide the cortical approach, and alter that extent of resection when you're getting too close. I think the message is that there's a lot of work that needs to be done here and little has been done so far. We see similar things in cavernous malformations. We find that fMRI, DTI, and MEG, these are all important and useful things that help us make our surgical plans. The mentality is a little different with cavernous malformations. With these, what we're looking for is a presenting surface of the lesion so that we can get there safely and not have to violate any tissue. And usually, with the array of approaches that we have going through subarachnoid spaces, we can find one that fits. And then it's just a matter of getting safely to that surface and then peeling it away from eloquent tissues. But cases like this are a good example. This is a mid-20-year-old guy who plays professional soccer, and he's a goalkeeper. And he didn't want to live with this, and he wanted this out. And I had to find a way to get this out safely. I didn't want to go through the floor of the fourth ventricle and risk an eye, extraocular eye movement problem. And so I decided to go through this, through the middle cerebellar peduncle, which I find is one of the few safe entry zones of the brainstem. And the DTI, which you see in that middle panel, is very helpful because it shows you exactly where the tract is. And if you go through the peduncle, you have to make sure that you avoid all the motor tract. And there is a nice pathway through the peduncle there that gets you right to it. And I'll show you this example. The middle cerebellar peduncle, again, is surprising in its tolerance. But if you look at the anatomy here, that's the eighth nerve. And as you peel the flocculus off of the eighth nerve and work your way back on the peduncle, it takes you beyond the tract of the descending motor fibers. And then as you go through the pons, it's actually one of these awkward things that sort of violates our teaching of just going through pia and not through brainstem. But in fact, this is the silent area that I've been talking about. You can go through about five millimeters or so of depth, and you can get through to the lesion and take it out safely without deficit. And that was the case in this guy. Other ways that we can use mapping. This is an example of a stimulation mapping case of a cerebral peduncle in the midbrain. So this lesion came almost to the surface. You can see the stain on the surface of the middle cerebellar, middle cerebral peduncle. But having this cartouche probe and being able to map out exactly where the fiber tracts are was extremely helpful. And this was also a case where we monitored the MEPs and SEPs, and you can see that hole in the peduncle there, but it was all done safely with no lasting changes in the signals. And this is also another example of how you can really work your way up and down, map out where the peduncle is relative to the interpeduncular fossa and the rest of the peduncle, and find a safe route in. So in the last few minutes, I'm going to talk a little bit about seizures, because obviously, as a vascular neurosurgeon, my focus is on protecting patients against hemorrhage and catastrophe, but seizures is a big part of a patient's quality of life and often how they present to me. So we do think about this, and it's something that we can impact greatly. So we've reviewed a lot of our data on our seizure outcomes with various vascular lesions, and I'll summarize some of this here for you, beginning with the AVMs. This is a review of over 400 patients. You can see how a lot of these AVMs do present with seizures, and these are some of the factors that are associated with preoperative seizures. What we found when we looked at predictions with outcome is that there weren't a lot of factors that seemed to foretell seizure cure or outcome. The preoperative symptoms were not associated. The pre- and post-op factors were not. Really the only thing that came out of this analysis was deep perforator supply, which is a little bit perplexing, but it probably has to do with the difficulty of resection and perhaps some intraoperative bleeding that's more likely with these particular ones with these deep perforators. But in any event, we did get very good seizure cure in these patients. It was in the mid-90 percent range. Now this is going on to our cavernous malformation series, looking at our results here. And this is our general philosophy and algorithm. I tend to prefer lesionectomy as the primary or first option because it's simple and effective in most cases, and it's really only the intractable cases that we think about more than just lesionectomy. So that's our algorithm. You can see in the table the numbers. And our seizure freedom rates were quite high, 98 percent with no pre-op seizure history, and 99 percent with pre-op epilepsy. So we do do quite well with these patients in general. And looking at the literature, this was also a review by Dario and Eddie from our group. And looking at the literature, I think it's a fairly good result overall. Seventy-five percent of patients end up seizure-free with surgery. So I am very pro-surgery for patients who present with these lesions and seizure problems, and I think it's very valuable. So to finish and summarize, I think there is a role for vascular surgery for seizure patients, and our rates are high. Lesionectomy tends to be a safe and sufficient way for most of these, and it's an important part of the therapy. So to conclude, these are some of my thoughts. Again, going back to how I began this talk, we pride ourselves in being able to stay out of brain tissue and stay in subarachnoid spaces and really capitalize on those tissue planes to get us to where we need to be or to the lesion. And so we try to avoid going through tissue. But when we do need to do that, I think these motor and speech mapping techniques are very valuable. I can't underestimate the value of SEP, MEP, and EEG during most, if not all, of these aneurysm cases. It's hugely important for me, and I think there's a lot more work that can be done to make this even better. Thank you.

mapping in vascular neurosurgery

neurophysiological monitoring

aneurysm surgery

AVM surgery

cavernous malformations