It's bright and early on a Friday morning after a fun night last night. My name is David Brogan, and our ICL today is Stop Poking Me, the Future of Nerve Imaging as a Replacement for EMG. I'm very fortunate to have joining us as well a number of panelists, and my co-moderator, Dr. D, and then we also have Dr. Murphy from the University of Manchester, and Dr. Fox will be joining us in a few minutes. She's engaged in another ICL at this time. But the focus of this morning really is how can we potentially exploit different imaging modalities to eventually, hopefully, move away from, at least for me, it was a pretty significant reliance on nerve conduction studies. And so we'll do that by looking at several different modalities, some that are currently in use and some that are hopefully more in the preclinical phases. And Dr. D will talk about ultrasound and traumatic nerve injury. Dr. Murphy will talk about their outcomes for measures for peripheral nerve regeneration. And then Dr. Fox will give us a tour of MRI, and I'll talk to you about some of the work that we've done in the lab, looking at neuro-infrared fluorophores. And if there's time at the end, hopefully we'll have time for a discussion and go through some cases. So without further ado, I'd like Dr. D to lead us off here. There we go. All right, so thank you for coming on Friday morning. Exciting topic, it's near and dear to my heart, peripheral nerve. So David asked me to talk about the use of ultrasound in traumatic nerve injury. This is something that I did not use early on in practice. I was not exposed to in my training, and I've evolved towards this. It's been interesting to learn more, and I know that many in this audience have far more experience with ultrasound than I do. So welcome any feedback and thoughts that you have. My name is Christopher D, I'm from Wash U in St. Louis. So everybody in this room knows about the decision-making after a nerve injury. The big high-level things that I want to know is, is the nerve in continuity? How extensive is that zone of injury? And will this injury recover without intervention? Those are the three things that I try to understand about each and every nerve injury that comes into the door. So how do we answer these questions now? And how can we get better? So peripheral nerve injury walks into the door. Katie, you get nerve studies? Why? Can't you answer these questions based on your clinical decision-making? We all would probably get nerve studies, but has anybody ever had a nerve study, personally? They hurt, they hurt. They're expensive, they hurt, and if it doesn't add a whole lot to your decision-making, why are you getting it? Admittedly, I still get them, and I have had one. So David asked me to talk about ultrasound. It has the advantage of filling the electrodiagnostic time gap, okay? So typically, we wait until malaria degeneration kicks in, and then we get ultrasound. Typically, we wait until malaria degeneration kicks in enough for us to get a result of denervation on a nerve study. We know that process starts pretty quickly on a basic science level. Probably clinically, it will show up on a nerve study at the earliest two to three weeks. To be safe, we usually go for that four to six-week window to get that first nerve study. An early nerve study will not tell you anything about the new nerve injury, except for maybe some baseline chronic changes. Say, for example, something from the neck or double crush kind of thing. Ultrasound is detailed and accurate. It is operator-dependent, so you really have to know your sonographer, or if you are doing it, you have to be good yourself. I would argue that as hand surgeons, we probably know the anatomy better than anybody else, and many hand therapists also know the anatomy better than anybody else. So ultrasound can be a powerful tool for all of us. You can see disruptions in fascicular pattern, and in looking at a survey, it contributes to treatment planning in 72% of cases. I would argue that I use the ultrasound as much as I can, and I try to get it for every peripheral nerve injury, if it's available. We talked about the disadvantages. It is totally dependent on the person doing it, and sometimes you don't have it available at your institution. So that's something that when you go home, I would say, try to understand who does this and who does it well. Prognostic data is not yet available. Now, I would hope as we, as hand surgeons and peripheral nerve specialists start to use this more, we will use the data in a way and publish it so that we can establish, you know, these characteristics on the ultrasound say that this is probably a Sunderland 2, 3, or 4, and this nerve injury is or is not going to get better. So here's a case example from St. Louis. People get shot in St. Louis. It's really good for training, I guess, but otherwise, you know, 35-year-old woman, multiple gunshot wounds to the right upper extremity, zero thenar function, notable atrophy already. She has no median nerve function for the extrinsic medians. Ulnar is fine. Two points are out in the expected median nerve distribution. So obviously, based on this picture, I've taken this patient to surgery, but we did obtain some information ahead of time that was super useful. I use the ultrasound right now to help me understand is the nerve actually in continuity or is there some kind of discontinuity injury that maybe I would intervene earlier on. So here's the approach that we did to the median nerve in the proximal forearm. Here is a superficial bullet that was present and removed and not put into a metal pan, but we missed that opportunity. So here we have exposed the median nerve. You can see the anterior neurosis nerve in the vessel loop. So here's where it starts to get less fun. So you can see the zone of injury by the discoloration of the soft tissue. You can see that there's a change in the nerve and the overlying FDS muscle. So you see the healthier nerve on the right-hand part of the screen. As you head into the middle part of the screen, you start to see the scar that's occurring, and we're basically getting into that area right underneath that fibrous arch of the FDS. So we dissected out further, and we can see that right underneath the pronator teres, which is in that penrose, you've got partial discontinuity to the median nerve. So ballistic injuries will have potentially an actual disruption, but then there's also this cavitation zone that you need to be aware of, too. Some of it's referred to as a penumbra. So we've got our partial disruption, and then we've got a very broad zone of injury to the AIN, which unfortunately has come off at the same exact level of the injury to the median nerve proper. The ultrasound ahead of time was super useful because we can see that we've got distinct enlargement at the distal bullet scar. So you can see the cross-sectional area is 41. And then in the long axis, you can see the disruption in the fascicles that matches very well to the intraoperative inspection. So as I am in my learning curve with use of ultrasound, I love seeing this correlation and bringing it back to the sonographer. So for this case, we've got a gap that's pretty sizable. We harvested SERL, and for the AIN, there's no way I was gonna be able to re-innervate at that level, so we have a plan for future tendon transfers. And this is not part of this talk, but in terms of reconstruction for the thenars, I found this nerve transfer that was described by Dr. Bertelli initially to be highly reliable, and I go to it whenever I have a high-median nerve that I know is unlikely to come back. Another ballistic injury in St. Louis, this time in the lower extremity. You can see here that there is a partial fracture of the distal femur that has been treated with an intramedullary device. You can see the zone of injury based on the X-ray itself. Patient has a sciatic nerve palsy, as expected at this level. So you can see the ultrasound shows clear enlargement of the sciatic nerve. And now we're starting to see that we're at the bifurcation of this nerve, so we're starting to split off into the tibial and into the perineal. So for me, with these findings, with the absence of recovery, we went ahead and performed an exploration. You can see the entry zone there in the very middle of the screen for one of the bullets. Tonell signs are marked with the Xs. So we explore and we find the common perineal nerve out on the right side of the screen, and then in the middle, we're starting to get into the zone of injury. The zone of injury there correlates with the entry scar that you saw preoperatively. And here's what we found. So this is a good example of both the cavitation injury as well as a direct trauma to the nerve. Got broad injury here. You've got a tibial that is structurally intact and a perineal that is disrupted. So the ultrasound is super useful for decision-making for us because now we know whether the nerve is in continuity, how extensive the zone of injury is. It's not perfect, but it's given us a high likelihood of what we're trying to understand. Is this gonna get better or not? And especially with some of these injuries that are more devastating than others, it does help us understand when we need to intervene. So will this injury recover without intervention? I don't know yet. I think we still need to collect more data, and I think that's the area where we're gonna grow as we go forward. So thank you for listening, and I welcome any questions, and I look forward to the rest of the panel that David has assembled. All right, Chris, quick question for you before you leave. So your first test of choice, somebody comes in with a nerve injury, do you always get an ultrasound? And if so, when do you get the ultrasound? So I think one of the advantages is that it does fill that electrodiagnostic time gap. So now our residents have become so good at recognizing these injuries that if the patient is in the hospital still for their polytrauma and we can get an ultrasound, it's really helpful. So if we can get it, it'll help us determine if we need to get a nerve study when they come back for that or when they come for their first visit. I typically wouldn't get a nerve study until about four to six weeks, but if I can get an ultrasound right away, we'll get it. When do you or do you ever see ultrasound fully supplanting nerve studies for a typical nerve injury or even a carpal or cubital tunnel? No, because you're gonna figure out the fluorophore stuff way before that happens. All right, moving on. Yeah, please. So, we're fortunate enough to have a really talented team of sonographers in our PM and our group. I mean, they're amazing, and they're a great resource for us. They bring the machine over and show us. We get really excited about it. And then I take these slides and I show it to them so they know what we're seeing and how helpful it is to us. Based on the ultrasound, we had consented and prepped out the leg, because we had a high suspicion that that's what we were going to find. Yes? Do you foresee using the ultrasound intraoperatively? I think that'd be fantastic, and that's an area where I want to grow personally and getting to that point. Which one, the perineal nerve or the? Yes, I cut out that lesion. Yeah, and I trimmed back to healthy vascules. Other questions? All right, excellent, thank you, Chris. All right, next up we have Dr. Murphy going to talk to us about his outcome measures for peripheral nerve regeneration using light and sound. Thank you. Great, well, thanks, Dr. Bergen, and thanks to my panel members for inviting me to talk today, it's a real honor. So my name's Ralph Murphy, I'm from Manchester in UK, and I'm gonna talk a bit about some of our work that we do with ultrasound and also measures using optical coherence tomography. So I've no disclosures personally, but this work was funded by grants from the Royal College of Surgeons, British Association of Plastic Surgeons, and Engineering and Physical Science Research Councils. So a little bit about Manchester. We do have a strong academic health science establishment. The two hospitals we work in are the top left and the bottom right, and the university in the top right and the bottom left. So some of our work that we did a few years ago was looking at developing a core outcome set in peripheral nerve injury of the upper limb. It's similar to some of Dr. Dai's work that we've seen, especially in the brachial plexus setting, but this is more generic to all peripheral nerve in the upper limb. One of the things we found in terms of domains of areas that we need to explore was neurotrophic measures that are becoming more widely available, mainly in terms of imaging, and this is what I'm gonna talk a bit more about now. So on a basic science level, we can look at proxies to what's going on at the area of injury, but it's the site of injury of surgeons that we wanna know about. We wanna know if the nerve's regenerating, and if it's not regenerating, why is it not regenerating? Often we will do our repairs or do our graphs, autographs, allographs, or converse, whatever you wanna put in, but we don't know exactly what's going on, and we'll often leave it and decide and give patients time to progress, but it would be useful to know what was actually happening in the early phases of nerve recovery. Ways to explore that, so you could look at proxies in the central nervous system or peripheral nervous system in terms of MRI, functional MRI, at the site of injury, ultrasound, we've just talked about, and also MRI, and then at the end, organ, so looking at skin changes in sensory nerves or muscular changes in motor nerves. So we're all very aware that the skin dries or thins after nerve injury, sensory nerve injury, and also becomes dry because the sweat ducts are switched off, the autonomic system is damaged, and that's what we see. So we looked at this and sort of ways we could measure or quantify what these changes that are going on are without obviously doing histology and taking biopsies of skin samples, which would be far too invasive for our patients. So we've used optical coherence tomography, which is a light-based imaging source. It's similar to ultrasound. It fires light at the tissues and measures the bounce back, and in finger skin or hand skin on the velar surface, you can get to a depth of about one to two millimeters, and an accuracy of about five to seven micrometers, so we can see sweat ducts and we can see the epidermis and the dermis, and the sort of bumpy layer, the line below is the dermal-epidermal junction, if you can just make it out, just going across here. So we started off by scanning a lot of normal people so we could figure out what is the normal ranges of patients or people in terms of their thickness of skin and their sweat ducts in their hands, and we found there's a significant decrease from the thumb to the little finger in terms of epidermal thickness, and a significant increase between thumb, middle, ring, and little in terms of sweat duct density. There was no real difference in terms of age, in terms of epidermal thickness, but sweat duct density decreased in the volar hand skin as patients got older. There was obviously a difference between females and males in terms of epidermal thickness, but no difference in sweat duct density. And in terms of racial background, we found that Afro-Caribbeans had thicker skin and less sweat ducts compared to white and Asian population. So we devised reference intervals that we could then work with in terms of nerve-injured patients and see in our nerve-injured patients whether they return to these normal ranges and at what time points they return to them. So sorry for the busy slide, but I'll talk through it. So on the top section, you've got the epidermal thickness and the sweat duct density, and what we saw, so this is straight after nerve injury and repair, so time points nought to six months. And immediately, we saw a reduction in epidermal thickness by one week, which continued to reduce by four weeks, and then that increased back towards normal by six months. Sweat ducts, they completely collapsed and were switched off because the orthorhombic nervous system towards the skin was cut and therefore didn't receive any support. And what we saw was that the injured side or the injured nerves returned towards the control side by six months. This correlated well with standard clinical outcome measures in sensory nerves, 2PD, WESS, lochagnosia, and also in terms of PROMS, DASH, and iHAND. And so we correlated, so within subject correlations between these measures, the epidermal thickness and sweat duct density, and PROMS, DASH, and iHAND, we found that sweat duct density was probably the best in terms of correlation to changes with DASH and iHAND over the six-month period in hand sensory nerve injuries. It correlated similarly to 2PD and similarly to WESS, but this is an objective tool that doesn't require any user-patient interface. It's the patients are putting their hand under an imaging tool that measures these measures and gives us the readouts that we need. So in terms of the PROMS, it's cheap. It's easy to use. It's quick to scan. You get real-time imaging. It is time-consuming image processing and certainly the learning curve in terms of using it, and it requires standardization, and hence why we did our normal work on injured patients. So the future work, I think, with OCT is diagnostic studies to compare two intraoperative findings to see if it can help us diagnose and prevent having to explore certain types of nerve injury, and also develop a finger scanner for point-of-use care so it's a lot easier and quicker to use. Moving on to ultrasound, so this is the other part of my talk, the site of injury. Again, probably one area that surgeons are often more interested in. We wanted to explore the capability of ultrasound and see what imaging we can get, the accuracy of the imaging, and also whether we can start to quantify nerve regrowth at the site of injury. So some work by Professor Chang's group in San Diego, he's a professor of neuroradiology. They've demonstrated that, through ultrasound of cadaveric nerves, that nerves with myelin and collagen have more backscatter or more hyperechoic than nerves with just collagen, so empty fascicles alone. So we worked on that principle to see if we could then quantify nerves with myelin and collagen, and therefore quantify regrowth. So through the site of injury and in the distal stump, the nerves with more myelin will have more backscatter. So what can you see with current advances with ultrasound? So high-frequency 3D tomographic ultrasound can give you some great pictures. This image on the left is a 3D recon, multi-planar recon, using ultrasound of a median nerve in the forearm, extending from the elbow to about mid-forearm level, where the branch coming off is the AIN. The images on the right are the multi-planar images, and you can see the nerve fascicles. So it's not playing quite as well. So it's not playing particularly well, but this is the median nerve on the right, and you get a multi-planar image as the nerve passes through, and then you can quantify within that the different sections of the injured nerve. So how do we do that? So we take a standard measurement of the proximal stump, the repair site, and the distal stump. We compare that baseline to the non-injured side as a control, an internal control of these patients, and then we followed them up for 12 months to see how the nerves are regenerating and what the ultrasound changes were. And what we found, this is one participant who had a razor blade injury to the left medial nerve that was repaired quite quickly, and they had good clinical outcomes. One month, you can see proximal stump here, the distal stump, there's incomplete regeneration across, and then hopefully by four months, you can start to see there's more complete regeneration, and it's more hypoechoic. So how do we quantify that? So within those sections of the nerve, the proximal stump, the repair site, and the distal stump, you can calculate the grayscale, or the backscatter, or the hypoechoic effect of what's going on in that area. So in the proximal stump, we saw an increase in the grayscale, or more hypoechoic, up to four months, and then it tailed off towards six months. The red is the volume change, which was pretty standard throughout, so it didn't show any increase in volume or worrying signs of a neuroma in continuity. At the repair site itself, what we saw was a gradual increase from one, two, to four months, as we expected, and then it started to plateau by six months, as nerve regeneration would be complete. Volume changes, it was slightly higher volume at the start, as you'd expect, some interoperative swelling in edema around the repair site, and this tailed off and plateaued back towards control levels by six months. At the distal stump, again, we saw a similar feature. We saw that gradual increase in grayscale, or backscatter, and that tailed off by six months, and again, minimal volume change, so we're happy there's no neuroma in continuity. Now, in a patient with poor clinical outcome, for example, this is a lady who had a glass laceration, high-median nerve injury, initially explored by vascular surgeons, had an arterial graph, vein graph, sorry, and then there was a delay to repair the nerve four days later. By six months, you can see on the transverse image, she's got a hypoechoic mass at the repair site, and she's got a neuroma in continuity. We later went back in and explored the nerve and cut it out and autographed it. So, this lady, in terms of what you can measure and the outcomes of grayscale, you can see at the proximal stump, there was minimal change in the grayscale, so there was no increase in myelin. We're not seeing that increase in myelin, and that stays true throughout the repair site and in the distal stump, so we can safely say that there doesn't appear to be any regeneration going on here, and what we are seeing is an increase in volume, especially at the repair site and in the distal stump, which is where this neuroma in continuity is developing. So, the other things you can do with ultrasound, this is a nerve conduit, a phase one study in Manchester of a novel nerve conduit called PolyNerve, which is a topographically enhanced synthetic nerve conduit, and you can measure it in vivo and see the degradation rate quite clearly, and it was a very useful tool to experimentally measure novel nerve treatments. So, the PROSE is cheap, it's relatively easy to use, it's quick to scan, you get good topography so you can see what's going on within the nerve. There's real-time functionality, and you can start to see blood flow and potential for contrast media use. It's definitely a user-dependent learning curve. The settings and the way we do it, we need large-volume, multi-center core studies to really achieve standardization of this, and it's not cross-sectional. You can't see behind bony structures. So, as I touched on, we need larger multi-center perspective core studies in health and disease to really understand the capability of ultrasound software automation, and ultimately, hopefully, what we're starting to look at soon in Manchester will be ultra-high-frequency assessment of the intravasicular blood flow. Thank you. That was fantastic. I'll start off with some questions, and I'm sure the audience has some. So, the first one, in terms of looking at the changes in the skin thickness and the sweat patterns and such, so that, to me, speaks to CRPS, right? So, is this the test, kind of the elusive test that we can use definitively for CRPS, and if so, when can we have it? Well, I mean, it's a good question. It would be great if we could use it in that cohort, and it's something we're looking to explore. We haven't looked at it so far, but I think it really does have some potential in that cohort of patients to give us an idea. Do they have CRPS? Do they not? And what we do next. And then, for your high-frequency ultrasound, do all patients who have nerve repairs get high-frequency ultrasound in Manchester now? No, this is very much experimental. We've started off doing this on a few patients, and we're hoping to expand it further, but it's sort of in the kind of pre-clinical phase of use, I think, at the moment. How long does it take to do a scan like this? So, the scan itself is 30 seconds. You can scan in time, median nerve from axilla down to the wrist. But it's the image processing afterwards that takes a bit of time. Sitting down, looking through the multi-planar images, and calculating what you need to calculate to quantify the gray scale and the volume. Excellent. Other questions from the audience? Lots, okay. So, I'll start right here. Yeah. Thanks for the great talk. I have two questions. First is, what's the megahertz for your high-frequency? So, we use a 20 megahertz probe as a compromise between frequency, so accuracy of image, and depth of scanning. Yeah, that's a very good question. It's the hardest point in terms of measuring and standardizing between patients. So we scan the load of normal nerves and we try to sort of set it in a way that was standardized, but ultimately we need prospective studies, large and multi-center cohort studies, so we can actually achieve what the setting should be and get a more accurate, you know, standardization of this. There's another question here, yeah. I mean, yeah, it'd be great, it'd be good to talk to you afterwards about it to be honest. So the stuff we've used before is like a microbubble ultrasound contrast agent. So you, you don't have to be cannulated to the patients, but you inject this microbubble contrast and then in the correct phase or time point after it's injected, you scan the nerves and what you get is the bubbles collapse with the sound waves from the ultrasound and that gives you a much greater image of the blood flow. Yeah, that's exactly what we use. So we always compare an internal control to the contractual hands as the normal. Other questions? All right. Ralph, thank you very much. That was fantastic. Thank you. It's going to be a long 10 minutes if I can't get it to open. Do it. OK. It opened before. It's just this thing's having issues, I think. All right. Sure. OK. We can see if pages will open. I can always go to moderate some questions, productive. How many people are using ultrasound in their practice currently? Show of hands. Okay. Are you using it for diagnosis? I guess the next question. How many are using it for diagnosis of chronic compressive lesions? So ultrasound, cubital tunnel, carpal tunnel, okay. How many are using it for early diagnosis of traumatic nerve injuries? Okay. What are you looking for when you do? Do it continuity, okay. Excellent. All right, and do you do it yourself or do Right Excellent Are people who are using ultrasound are you doing it yourself? Are you having a radiologist or a physiatrist to it? So who's doing it themselves in their in their clinic? Yes. Okay, and who's sending them out for radiology or physiatry? Okay, it's a mix in ours we have some access to an ultrasound machine you have a flash drive Just in case I'm gonna go find me, but do you have yours on a flash drive? Let's just hook it up to the we can do that You better close all those tabs David All right, we'll do this, that'll work. So I'm going to move towards something that's a little bit more preclinical in nature, so not quite the same that Dr. D and Dr. Murphy had, but hopefully some interest. These are my disclosures, mostly research support. So what we're all dealing with probably is struggling with the fact that the characterization of nerve injury is challenging. It's challenging in the clinic and it's challenging in the operating room. And ultimately what we're trying to figure out is that even if we can see a nerve that is mechanically intact, so let's say the trauma team fixes a humerus and they say, oh, the radial nerve was fine, I saw it, I looked at it, it's still not working. And then the struggle with that, sometimes you don't know if it's intact. Sometimes even if you know it's mechanically intact, you don't know how badly it's injured on the inside. Because what we can't do easily is look at that internal architecture of the nerve. And so what we've heard already today is attempts to kind of look at that internal architecture with greater detail. But there's also potentially some opportunities to exploit other aspects of a nerve and nerve health with our imaging. And when you think about imaging, just kind of take a step back, and what is imaging? Well, imaging is essentially the exploitation of some sort of physical property or process and then turning that into a visualized image, right? So x-ray being one of the first medical imaging from Sir Wilhelm von Rinken, and that's really just looking at x-rays passing through any sort of object and exploiting densities and changes in the density between the different tissues, right? Ultrasound is looking at the echo and the changes in the echo of sound waves, the echogenicity of that. And an MRI is really, if you kind of get down to the fundamentals of it, it's looking at how it's the proton content and how protons change, hydrogen atoms will change when they're hit by different gradients of magnetic fields, right? It doesn't actually, MRI is not anything other than just slightly different changes in proton signaling that we're able to detect at a very high resolution. So any sort of signal that you can exploit that's different from a healthy to a diseased state is a potential candidate for imaging. So then if you start thinking about it, if we're trying to look at imaging intramurally, what's the fundamentals of a good surgical tool? And as an inpatient surgeon myself, I would submit to you that probably the things that make a tool easy or make it attractive is that it's got to be easily available, that we can rapidly distribute to a number of people. It has to be a quick learning curve. I don't have the patience to sit there and go through hours upon hours of courses and things like that. It has to be somewhat cost effective, right? Or else I won't be able to get it approved through my hospital. And then it needs to require minimal effort and time out of my normal surgical routine. So if it's going to add an hour to my case and have only a marginal benefit, there's absolutely no way that I'm going to adopt that tool. So then we think about kind of properties for nerve imaging. How can we utilize nerve imaging? We can either look at the difference between a healthy nerve and an injured nerve. There's a number of different physical properties, molecular processes that you could potentially exploit. So everything from the actual composition of the nerve. So if you're looking for, say, trying to identify a nerve for navigation to avoid injury to a nerve during, say, a thyroidectomy or an ACDF, or when we're trying to look at changes in an injured nerve. And so things that we've already heard about, looking at the cross-sectional area, the echogenicity, the changes in the internal architecture. Also the changes in the epineural or intraneural vascularity are things that are currently being exploited. And then finally, you can potentially look at changes in the blood nerve barrier, that thing that kind of keeps us all safe, as well as potential excretion or secretion of proteins or cytokines that are involved with the inflammatory reaction from nerve injury. And so really, if you think about, how do we evaluate nerves intraoperatively now? Well, probably the current standard is that we kind of look and feel. Second generation, we'll talk about that. And I hope to discuss briefly with you some intraoperative molecular imaging techniques that we're hoping to use in the future. So what we'd all do now is we've talked about, you look and feel the nerve, you cut back to healthy fascicles. These are all crude techniques, but really, it's probably the best that we have. Ultrasound I think has a lot of promise for being both a preclinical, as well as an intraoperative tool for assessing nerve structure, particularly when the nerve looks like it's in continuity, but we know that the fascicles are somehow damaged. We can also look at the difference in changes in vascularity of the inside the nerve and outside the nerve. And that can be useful for compression injuries, such as carpal tunnel and cubital tunnel, as well as traumatic nerve injury. So this is a case with a gunshot wound to the sciatic nerve, and you can see this loss of the internal vesicular structure. We cut that back, and again, we see pretty significant damage with inside the nerve, despite being a continuity. So ultrasound has also been utilized to exploit intraneural and epineurovascularity. So the increased cross-section area, the intraneurovascularity has been correlated with increasing nerve dysfunction in both carpal tunnel syndrome and cubital tunnel syndrome. So that's, in my practice, one of the biggest uses of ultrasound is looking at use for diagnosing carpal and cubital tunnel syndrome, and it's really changed how I approach many of these patients. But given the fact that we know that nerves can potentially change their blood flow with different times of injury, we asked the question, could we actually crush a nerve and then look at the change in blood flow acutely and follow that over time? So we did this in a preclinical model with a rat using laser Doppler flowmetry. And for those who aren't familiar with laser Doppler flowmetry, it essentially operates on the same principle as an ultrasound or as a Doppler in an ultrasound, but instead of using sound waves, it uses a laser signal. And then the bounce back from anything that's moving within that will change the frequency, and then the detector can sense that. It's very similar to what we use for pulse ox. So laser Doppler flowmetry, we crush the nerve with differing degrees of mild, moderate, severe crush. You can see the control over here. Initially in the two weeks, it looks relatively the same. After crush injury, the pre-crush, and then up to even two weeks afterwards, we see increased hyperemia or an increased flux of the nerve after a severe crush. What we found is that immediately after the crush, this is a mild, a moderate, and a severe crush, this is the control, that everything increased a little bit, but there wasn't a really great way to discriminate the difference between the different types of crush. But up to six weeks later, if it still had hyperemia, that corresponded to incomplete recovery of the tibialis anterior strength. So a nerve that was injured and damaged that was still not functioning normally still had increased signal. And that's actually been shown on MRIs as well. So it occurred to us, is there a better way to look at changes in blood flow that don't require a laser Doppler flowmetry that nobody actually has in their operating room? And one of the most immediate and obvious answers is that we do have, most of us in our operating rooms, have access to something like the spy machine. So using endocyanin green for laser Doppler angiography. If you're not familiar with utilizing endocyanin green intraoperatively, it's a dye that's approved by the FDA. You give it, your anesthesia colleagues will give it. And then you can essentially image it. It will fluoresce at 800 nanometer wavelength. And then anywhere there's blood flow, you'll see the dye will be able to fluoresce essentially. So it's a nice, easy way. It's utilized a lot for tissue perfusion assessment, particularly, I think, in plastic surgery. So why do we use NIR? Well, NIR is attractive for a number of reasons, particularly because it's able to penetrate at least a few centimeters of depth. And so it's much better than visible light for doing that and allows us to create some contrast and discrimination in different tissue types. So this is a plexus case that we had, somebody who's got a severe lateral cord injury. The medial cord is working well, but the median nerve here has partial dysfunction. We happened to utilize ICG to look at the free-functioning muscle transfer that we were doing. And we just said, well, let's just put it on the nerve and see what we get. Because the question was, will this even get into the nerve and can we image a nerve with this? And the answer is yes. You can image a nerve. Certainly, the epineural blood flow on the nerve will show up. Interestingly enough, the functional medial cord worked. The lateral cord did not have as much vascularity. The significance of that, more to come on that. But intraoperative molecular imaging is more widely used currently for tumor resection. So neurosurgery utilizes, it's actually scorpion venom. It's a toxin that is highly sensitive to gliomas. And so they utilize this to identify the margins for a nerve tumor in the brain and then help improve the surgical resection margins and prevent intralesional resection. There are a number of agents that have been approved, 5-ALA, as well as hexaminolevulinate for bladder carcinoma. But there are multiple trials ongoing beyond just these. There are also dyes that are being developed. There's a group out in Oregon that is looking at development and screening of NIR dyes that are sensitive to nerves. And so the idea behind this is not just looking at nerve injury, but utilizing it for navigation. So if you're going to use laparoscopy and you're trying to avoid injuring a nerve that is kind of hidden behind the walls of the colon or the peritoneum, then you could give this dye and then with an NIR camera be able to identify a nerve that is really invisible in white light. So a number of groups have tried different things with this. They have probably the most success, signal to background ratios of 25 to 1, which is quite good. It could be a way to keep people safe during spine surgeries, neck dissections, things of that sort. Another group has looked at myelin basic protein and trying to have a dye that is able to conjugate and bind to that specifically. So again, to identify a nerve, a healthy nerve. And there are challenges with this because you have to deal with the blood nerve barrier. And so that changes. You have to consider both how the nerve interacts with fat, how it interacts with water, and then the size of the nerve, emission wavelengths, things of that sort. So it's not a simple or straightforward task to design a nerve-specific agent. What we looked at is could we identify nerve injury, right? So given some of our success with the laser Doppler flowmetry, we decided to try and identify MMP9. MMP9 is a protease that is excreted when nerves are injured and it's excreted early on in the first few days after a nerve injury. And so this utilizes a process called FRET imaging. And what FRET is, or FRET technique, so essentially this is a quencher dye. It sucks up, it's a black hole quencher, it sucks up all the fluorescence in the light nearby. This is a cypate dye that just in its natural state fluoresces at either 700 to 800 nanometers depending on which dye you use. When they're brought together in close proximity with this peptide chain, then the quencher dye will suck up all the fluorescence, nothing glows. You can specify and dial in this peptide chain to be whatever you want it to be essentially. And so what we did is made this sensitive to the effects of MMP9 as a protease. So in the presence of MMP9, it cleaves this peptide chain. The cypate is released and is able to glow on its own. And this is the concept. Essentially MMP9 comes in, gets rid of the sequence, and then the fluorophore glows. We tested this in a rat model with a severe crush injury and then looked at them at different time points, six hours, two days, two weeks. What we found is that we had some ability to image the zone of injury compared to a normal nerve. So the signal-to-noise ratio is not as high as what you would see in the, as I showed earlier in the 25 to 1, but still reasonable. So this crush injury up top, rat sciatic nerve, injured nerve, uninjured nerve, and a significant difference between them. What we actually found is we gave a nonspecific dye, which is just an unbound cypate at 700 nanometers, and then we gave ours, which glows at a different wavelength. So you can actually image both simultaneously and assign different colors to them. But even so, something like indecine and green would actually glow in the presence of an injured nerve. And we found that at 30, 60, and 90 minute time points after administration of the dye. So then we thought, well, can we do better? Can we get a better signal-to-noise ratio than what we had with MMP9? So this is a, LS301 is a probe that is actually currently in clinical trials at our institution for solid state tumors. And so they're using it for cancer resection. And we decided to try it on a rat, since there's a pathway to getting that into humans. And lo and behold, it actually was even more impressive. This is the uninjured nerve. This is the injured nerve after administration of that dye. And so a pretty stark, significant difference between those two. And when we looked at this with both a severe and a mild crush at five hours after injection and six hours after the nerve injury, we found a significant difference between the injured sides versus the control out controls in terms of the amount of fluorescence that we could see. What I think is part of this, most likely, is that the LS301, it goes to phosphorylated annexin A2, which is part of the endothelial tight cell junctions. And so when you have an injured nerve, it probably changes the blood nerve barrier, allows extravasation of the nerve into the, extravasation of the dye into the nerve. And so that helps to make the nerve glow. This has been shown in a rat model with even a chronic construction injury. So essentially what we're going to likely exploit is that change in the permeability of the nerve, the dye is able to egress into it, and that will allow us to see nerve injury. So more to come. We are currently looking at the use of indesign green for tissue injury after mangling injuries to limbs. And then hopefully we'll parlay that into expanded use for nerves specifically. So I think the accurate characterization of intraoperative nerve injury is still a challenge. Our hope is that with development of dyes and other techniques such as this, that we can hopefully move the needle in the future and improve our ability to detect nerve injury. And that's it. Thank you very much. All right. All right. Paige, do you want to come up? We'll try one more time with this. If not, we can load it on my... You want to see? All right. Yeah, Paige, you want to come up? We'll try one more time with this. If not, we can load it on my... You want to see? All right. You have your... Yeah. Perfect. Thank you. All right, not too many AV difficulties, but they're in every room. So thank you to Dr. Brogan for inviting me here. I'm going to talk a little bit about the role of MRI in evaluation of peripheral nerves, so something that is available to us now, and really about how we can use that. No disclosures here. So nerve injuries, as everybody mentioned, these are an important problem. Sometimes they are undertreated and underrecognized, and I think that's when we don't know there's a nerve injury. Sometimes someone has a laceration and that's an obvious nerve injury. But there are other times where people have, as David pointed out, a humerus fracture. They say the nerve is intact, and we say, is it intact? And we kind of wonder what's going on inside there. And so I'm going to talk a little bit about how we can use MRI and some advanced MRI imaging techniques to figure this out. And so we really need better diagnostics, and a lot of people up here have talked about how we're going to come up with better diagnostics, and I think I'm excited about that. But what can you guys go back and use today working with your radiologists? So this is the current standard diagnostics. You all know these, and we've talked about these in addition to ultrasound, and I've been charged with talking specifically about MRI. So let's just look a little bit at a standard MRI versus what's called an MR neurogram. So this is a standard T1-weighted image, and if I challenged you to say, find the ulnar nerve in this image, you would not know exactly where the ulnar nerve is without saying to yourself, what part of the body am I looking at? I know my anatomy, and that's how I'm going to find it, but you can't just find it. It doesn't just light up for you on here. But you know that the ulnar nerve runs just behind the medial epicondyle, and that, as you're scanning through this, is how you're going to find it, right? Then you're going to go to your T2 image, and same thing, now maybe you're starting to see it over there. It's on the bottom right at about the five o'clock position for anybody looking for it. The one thing about regular MRI is that nerve imaging is slightly inaccurate at the elbow, because any time the nerve takes a curve, it's going to light up a little bit. That's an inaccuracy in MRIs. So now, what if I move up? So you know where the ulnar nerve is at the elbow. This isn't super helpful. I don't need to tell you where that is, but now what if I show you a random slice of the upper arm somewhere in the humerus, and I say, now find the ulnar nerve? It's going to be a little bit more challenging for you without scanning through that whole sequence, because there's a lot of white dots lighting up here. So which one of these is the ulnar nerve? You're going to make some guesses. You're going to scan up and down. If you're like me, you're going to go to the elbow, find the ulnar nerve, and go back up, right? Well, let's say if we make that a little bit easier. So this is a T2 sequence, and I'm sorry it doesn't project perfectly up here. This is a T2 sequence, and now I'm going to move to what's called a DES sequence, or an MR neurogram. And here's what's happened. I think you guys can all see the white dot now, which is located at about the 7 o'clock position there. That's the ulnar nerve. It's been lit up by the sequencing and the processing of this MRI. They've turned down the volume on a lot of things that are normally turned up in your T2 image. So here, all of our blood vessels have disappeared, right? And if you have a normal nerve on an MR neurogram, it should be iso-intense to muscle. So it should disappear in this image. You actually shouldn't be able to see it. And so here, you know that there's something wrong with your ulnar nerve up at the humeral level, and you're going to start looking for that, because that's not normal, even for cubital tunnel syndrome, right, that this high up you see these changes. So this is how we can use MR neurogram to really help us focus down on an injured nerve. And it really does give some beautiful images. This is one here of the brachial plexus. And you can really, if you guys have looked at normal MRIs and brachial plexus, you don't get quite images like this all the time. And this is the MR neurogram where you can really see those nerves lighting up. You can see their injury. You can see their area of injury. And the nice thing about this is it is, like all MRIs, no radiation, but it does have a little bit of time for your patient to obtain them. And it's a little bit longer than a regular MRI. So you do have to warn your patients about that. So just like all MRIs, if they're moving in there, your image quality goes way down. So MR neurograms, specifically fat suppression, blood vessel suppression, and heavy G2 weighting is what lets us see those nerves. So this is just a case example. And I hope you guys will stick with me. We're going to go to the lower extremity. But I know a lot of orthopods in here still know where the lower extremity is located. So our plan for this patient, it's a 20-year-old volleyball player, left posterior knee pain. We can't figure that out. And we're going to ask them, we're going to do all kinds of imaging. And we get an MRI, and it doesn't really show anything. But it's still suspicious. It sounds like nerve pain to us. So now we're going to employ an MR neurogram. And here you can see the tibial nerve with our green arrow. And you can see the peroneal nerve with our red arrow. And you can see that those two are different. And if you look at your muscles here, you can see that the tibial nerve, in fact, is iso-intense or looks the same as your muscle. And your peroneal nerve looks much brighter. My radiologist always says it looks like a light on a Christmas tree. And so here you go. This is just a different slice right closer to the knee here. And you see that continued difference between the tibial nerve and the peroneal nerve, showing you that something's going on with your peroneal nerve here. And in fact, intraoperatively, you go in there to release the peroneal nerve. And you actually see a peroneuroma that was causing this patient's pain. And once removed, then they were able to get back to playing volleyball. And so the question really is, how valuable is MR neurography? So I work with a multidisciplinary nerve team. And we took 58 patients that we had performed MR neurograms on for specifically nerve-related pain, trying to figure out, do these people have a missed nerve injury? And you can kind of see the age range and demographics here. And many of them had had symptoms for a very long time here. You can see nine years is our average. And we looked at upper limbs, lower limbs. And then you can see all the different inciting events. And as David pointed out, all kinds of surgeries are causing this, hernia repairs, everything. Nerves are everywhere in the body. So lots of different places that we were able to find these. And so everybody got an MR neurogram as part of this. And then these are all the other studies that they got in part of their workup. And then these are all the different interventions that were tried for these patients. Nerve pain patients and nerve injury patients can be very challenging. If you do this kind of work, you know. And we went on to treat many of these surgically. 30% of them, after looking at our MR neurogram, we said there's a surgical solution to your pain or a surgical procedure that will help with your pain. And so you can see on the left here is the referral diagnosis. This is when they came to us. Most people had joint pain or CRPS 1. And you can see after we performed the MR neurogram, we were able to convert 19 of those people to a specific nerve injury and CRPS type 2. And those are the people that we were able to treat surgically. So what's on the horizon here? This is a NIH study by one of my colleagues in radiology. And here we're going to combine that MR skill with PET and the Sigma-1 tracer. And so Sigma-1 plays a critical role in pain. So a lot of times our patients will come to us. And I think we all know this, that nerve injury doesn't always present itself as motor injury, motor deficit, or sensory deficit. Sometimes patients just say, I have pain. And some patients will even describe their carpal tunnel as just pain. And so how can we use that descriptor to help us find this location, figure out what is and isn't painful? And so Sigma-1 usually presides in the endoplasmic reticula if you don't have any pain. But it turns out if you have a painful injury, then the Sigma-1 receptor will be released. And it will go to the cell surface. And then you will be able to detect that using MR and PET combined. So the patients get a whole PET sweep. And they get an MRI of just the local area. And then we put those things together. I say we. That's the royal we. My radiologist puts those together. And then we get images that look like this. So up in the left, you see an axial T2 FAT-SAT image. And then on the bottom, the coronal desk, that's your MR neurogram there on the left. And you can see how beautifully you can see a sciatic nerve sheath tumor lit up there. And then the question is, is this what's causing the patient's pain? And you see your PET on the right there. It's PET-AVID. This is with the Sigma-1 tracer. And when you put those together, you know that the patient has a painful sciatic neuroma or nerve sheath tumor, excuse me. Another example of that here is in the right sural nerve. You have your MR neurogram on the upper left, your PET MRI together on the right. And you see your PET alone. It doesn't light up. So this is a non-painful right sural neuroma. And so how does this help us? A good example of this would be like your neurofibroma patient who has a lot of peripheral nerve sheath tumors. And they say, I'm having pain in this area. And you want to figure out, which one of these am I going to go in and resect? And I think this is really important in somewhere like the brachial plexus, where resecting the wrong one is going to cause a lot of difficulty. But a lot of times, these are so painful that they're very dysfunctional for the patient. So this is a great example of a patient of my colleagues that had a peripheral nerve sheath tumor. Tons of them trying to figure out which ones are painful here. And you can really see this is an example. Sorry, this is an example of a non-painful one. You don't see the uptake that you would expect. And then if you go down here, you can really see the significant difference there. Your MR neurogram beautifully lighting up that nerve. And then is it painful, answered in your sigma-1 receptor PET. And so I work with an interdisciplinary team to do all this work. I do not do this work alone. And so I think partnering with our colleagues in radiology. So if you want an MR neurogram, it's super important that you don't just send someone to sort of your local facility and say, MR neurogram. Because these are difficult sequences to obtain and read. So this is really a hands-on process. You really want to work closely with your radiologists to get the protocols and to make sure that you have an experienced radiologist. We have two experienced radiologists that read them all for us. But if your average radiologist that is not trained in reading MR neurograms reads them for you, you don't get the same results that you do in someone who's really experienced reading them, knowing normal from abnormal. Thank you. Thank you. Paige, that was fantastic. I'm excited to learn that you have a special interest in CRPS diagnosis and treatment. I'm not writing that up. Tell us about your experience. Because for those of us who may or may not have access to this, how did you go about getting the MR neurograms and establishing that collaboration? And did you approach radiology? Did they approach you? What's the process for that in your institution? Luckily, before me, I had a colleague that was interested in nerve pain. And we helped work together with our radiologists. But I really think it is about reaching out to your musculoskeletal radiologists. They have really been very interested and excited about partnering with this, both our ultrasound. And so that's why I use them for ultrasound. Because as we talked about, some of the techniques, they're very time intensive. And I don't have time to slide that really intensive view of ultrasound into my clinic. And they've been excited to up their skill set as far as, we have this MR neurogram. How does it correlate to an ultrasound? And really upping their skill set. So reaching out to musculoskeletal radiologists and really working closely with them. This should be the same MRI machine. It's just a different protocol or software that they have to load. Exactly. So it's a different sequence that they have to gather and then a different processing of the image. But it is not a different machine. It's your same machine. You do need it to be three Tesla or MR neurograms. Some parts of the body, 1.5 is OK. But in general, three. All right, any questions for Dr. Fox? Yeah, so that is part of a clinical trial, so that is not the Sigma-1 receptor is a novel receptor by Sandeep Biswal, who's one of our musculoskeletal radiologists. He developed that, and that is a clinical trial. So that is not something, that is something we set the patients up for, specifically they enroll in the trial and get that. So far, you know, these are patients that have struggled with pain for a really long time, so they're up for the day-long, you know, half-day-long set of imaging, but you're absolutely right. That is not something that you, you know, write down, you know, type in Epic and it comes up, so. Yeah, for anyone who couldn't hear that comment, he just was stating, you know, once a week, once a month, working with your radiology colleagues, that that really improves your relationship with them. I'll echo that and say that one other thing we do is actually make a clinical case conference. And if, you know, while we're talking about nerves in this room, but, you know, if you're looking at TFCC injuries or something like that, and then you show them the arthroscopy images and what it looked like, they love that feedback loop of saying, this is what I found, this is what you read, you know, how do we get this to be you more accurate and me more accurate? How do we get to the same place? And they love those clinical cases. And so I would definitely encourage that if you have, if you're at an institution where that's possible. Excellent. All right, I think that's a great place to end. So thank you all for your attendance this morning. I really want to thank our presenters for a fantastic session. So have a great day. Thank you.

nerve imaging

ultrasound techniques

MRI techniques

nerve conduction studies

traumatic nerve injury

ultrasound advantages

MR neurograms

nerve injuries

lesions causing pain

molecular imaging techniques