Morning, everybody. My name is Doug Hoffman, along myself and Ryan Kruse and Derek Hall. We're hosting the Ultrasound Case Series that started back in June. This morning, we have Dr. Jay Smith presenting carpal tunnel. But before I introduce him, just a reminder that our next Ultrasound Case Series case will be on January 8th, bringing the new year. It'll be a case by Dr. Jeremiah Ray out in California on the Achilles tendon. And we have two others, January 22nd and February 5th on the schedule. And then we're gonna go to start having the Sports Medicine Fellows present. So really looking forward to that. But today we have Dr. Jay Smith. To most of us, Jay does not need an introduction. Jay has been at the forefront of MSK Ultrasound going back 15 years. For many of us, Jay has been a mentor and a colleague. Jay has high standards for himself, I would describe, but speaking to his ability to teach and collaborate, he brings us all up. He's brought the level of MSK Ultrasound to a different level and has brought a whole cohort of people with him. I didn't get that. Could you try again? Oops, that was my phone. They don't believe you, Doug, obviously. So anyway, without further ado, I'm gonna turn this over to Jay Smith, who's gonna present the carpal tunnel case. Great, and thanks, Doug. And thanks everyone for tuning in today. And really thanks for that introduction, Doug. I mean, there are many great things about this field of MSK Ultrasound, but I think to most of us, one of the best things about the field is it continues to evolve. And it's a journey. And we're always learning from each other. And every time I tune into one of these cases, I'm always learning something. I tell everyone there's something you're gonna learn in every lecture for MSK Ultrasound, no matter how foundational it may be. And thanks to Doug and Maderic and Ryan for putting this case series together. And I'm pleased to be here today and talk about carpal tunnel. So the topic was carpal tunnel. And of course, the focus of these cases is to review the complete examination of a particular region. And there is no complete examination of the carpal tunnel per se. It's part of the bolar wrist examination. So we're gonna focus our attention on the bolar wrist region. And we're gonna follow along the same outlines. We're gonna review some anatomy and some pathology, but really focus on demonstrating the complete examination of the bolar wrist region. Of course, the carpal tunnel and the median nerve are the stars of the bolar wrist region. And so we'll spend a fair bit of time on those. We're gonna do something a little bit different today, and we'll see how that works. And all feedback is appreciated. I'm sitting in the anatomy lab on a Friday morning here, and I have an unembalmed cadaveric specimen that I've dissected to demonstrate some anatomy. And then I'll be doing the scanning protocol somewhat live. I'll be doing it live, but it'll be on another unembalmed cadaveric specimen so that we can talk about checklists and see checklists, but sometimes it's good to see how someone puts that checklist together into an efficient examination. So we'll do a case-based presentation, and then we'll get all of our material reviewed and come back to the case and then talk a little bit about the report. So bread-and-butter case, everyone probably thinks I'm gonna throw a zebra, but not really. This is the kind of patient that we all see, other than maybe a little bit young, but a 42-year-old right-hand dominant male. He's a manual laborer. He's had ongoing median nerve predominant symptoms, not involving the base of the palm, so outside of the palmar cutaneous branch distribution. And it's bothering him at night. It's bothering him during activity. He has positive provocative maneuvers for carpal tunnel syndrome, tunnels, and phalans, and so on. He has minimally reduced sensation in the index finger and long finger. No motor symptoms or signs. And his CTS-6 score is a 17. Now, those of you that aren't familiar with the CTS-6 score, it is a validated clinical tool to help diagnose carpal tunnel syndrome based on history and physical examination. And I'll refer you to John Fowler's paper in JBJS in 2015, and I'll refer to that again shortly. But that's a nice clinical tool if you're looking for some objectification of the clinical diagnosis of carpal tunnel syndrome. And a normal score would be less than 12. If you're greater than 12, it's highly predictive of carpal tunnel syndrome based on a clinical standard. His X-rays were normal, and he's tried activity modification, splinting, and a non-guided injection. And so he's sent to evaluate diagnostic ultrasound, see what's going on with his median nerve. He's a little bit young. He didn't respond well to the intervention. So is there something else going on? So let's talk about the role of ultrasound in the diagnosis of carpal tunnel syndrome. And one of the most important points that I'd like to make today is that the role of ultrasound in the diagnosis of carpal tunnel syndrome is evidence-based. There's a large amount of literature documenting the role of ultrasound to assist in the diagnosis of carpal tunnel syndrome by documenting median nerve enlargement, that is, swelling of the nerve in the proximal carpal tunnel region. And we'll see that today. And the most common cutoff that is promoted in the literature is 10 millimeters squared, meaning if the nerve is greater than 10 millimeters squared, then that would be consistent with median nerve enlargement and would support a diagnosis of carpal tunnel syndrome. As I mentioned, John Fowler's paper, I Like the Best, published a few years ago in JBJS, and he used the CTS-6 score as a clinical gold standard and compared the sensitivity and specificity of nerve conduction studies, ultrasound with a median nerve cross-sectional area of 10, and the CTS-6 and demonstrated that the ultrasound performed equally well to nerve conduction studies to diagnose carpal tunnel syndrome. Actually, the actual numbers were a little bit better for the ultrasound compared to the nerve conduction studies, but they weren't depreciably different. But the bottom line is, his conclusion was you could substitute ultrasound in the appropriate cases for nerve conduction studies. And that's not the only piece of literature that really promotes that. In addition to documenting median nerve involvement in terms of increased cross-sectional area, ultrasound can also allow us to identify causes and confounders. These are the masqueraders. These are the things that could be causing carpal tunnel syndrome or could be presenting like carpal tunnel syndrome, but are really not. Anatomic variations, tenosynovitis, masses, like ganglion and so on. And then finally, there is some discussion that ultrasound can help assess severity. Some individuals promote that if the median nerve is really enlarged, 15, 16 millimeters squared or greater in middle-aged and younger individuals, then that correlates with electrodiagnostically severe carpal tunnel syndrome. It doesn't necessarily hold up in older people. But certainly if you see thenar muscle atrophy or denervation change in the median innervated muscles, then you know you have axonal involvement and that would classify someone as being severe. So this is our checklist for the volar wrist region. This is right out of the AMSSM guidelines and no surprises here. The carpal tunnel contents are the highlight and we have the flexor retinaculum and it actually has three pieces to it, but we generally focus on the transverse carpal ligament, which spans from the hamate to the trapezium and the pisiform to the scaphoid in the middle carpal tunnel region. So I have that diagrammed here, the hamate to trapezium, the scaphoid and the pisiform and this is the transverse carpal ligament. The median nerve, of course, and not in the protocol, but what we are gonna review today are the branches, the important branches of the median nerve, the palmar cutaneous branch, the thenar motor branch and the digital nerves. And of course, the tendons in the carpal tunnel, the flexor pollicis longus tendon, not listed there, but obviously the finger flexor tendons and then dynamic examination. And then outside of the carpal tunnel, you have several structures of interest for the bolar wrist examination, the FCR tendon and the radial artery, primarily to remind us to look in this region because this is where the bolar ganglion cysts hide. In the center of the superficial part of the carpal tunnel region, you have the palmaris longus if it's present and on the ulnar side, you've got the ulnar neurovascular bundle with the flexor carpi ulnaris. And then surrounding all this are the bones of the carpal tunnel as well as the bolar recesses. So this is our protocol. So let's go ahead. And before we get into that, we're gonna go overhead camera and I'm gonna demonstrate some anatomy in this unembalmed cadaveric specimen for us today. Like I said, a little special treat because I know many of you may not have access to anatomy lab on a regular basis. So this is a bird's eye view, an overhead camera view of a dissection of an unembalmed specimen. And we're gonna focus on the median nerve, but you can see distal is to the left and proximal is to the right. Here's the thumb. So radials up towards the top of your screen. And what I have here first is here's the palmaris longus tendon. This individual did have a palmaris longus tendon that spread out to become the palmar aponeurosis, which is the distal continuation. I've taken all the skin and subcutaneous fat off, obviously. And over here on the radial side, we can see the robust flexor carpi radialis tendon that would be on its way to insert under the scaphoid. And on the ulnar side, bordering the volar wrist region is the FCU, the flexor carpi ulnaris, coursing to the pisiform where it has a partial attachment to the pisiform. I'm gonna reflect the palmar aponeurosis and the palmaris longus. And we're gonna focus our attention on the median nerve. First, I'll go on to this side of it. The median nerve, as I move the flexor carpi radialis out of the way and move the superficial flexor muscles out of the way, and I'm gonna loop around the median nerve. So I've got this elevator around the median nerve. The median nerve will exit between the superficial, which we see in the deep form flexor muscles in the mid to distal form. And then it will take off towards the carpal tunnel. Its first branch of importance is the palmar cutaneous branch, which I have the pickups under the palmar cutaneous branch. It'll arise from the median nerve about five to seven centimeters proximal to the wrist crease. The distal wrist crease is where the palm meets the form and is an important anatomic landmark. So it originates on the radial side typically, will course next to the median nerve and then take off superficial and radial. It'll eventually penetrate the fascia. So it lies outside of the carpal tunnel importantly. And then it will course next to or in the sheath of the flexor carpi radialis. So if you're gonna try to find this nerve, you find it at its origin, or you find it next to the flexor carpi radialis at the level of the distal wrist crease. Very small, this person had one fascicle, but you can have multiple fascicles. So now let's draw our attention to the main trunk of the median nerve as we get into the carpal tunnel region. So we're going towards the carpal tunnel region. I'm now gonna reflect this. Matter of fact, I'm gonna cut the palmaris longus and get this out of the way. So we're approaching the carpal tunnel region. Notice how the median nerve is centrally located and superficial in the carpal tunnel region. And I'm gonna twist this cadaver here to give us a view from, we're gonna move in and look on the radial side cause I wanna look underneath the transverse carpal ligament. So this is the transverse carpal ligament, the ulnar side of the transverse carpal ligament and the radial side of the transverse carpal ligament. And I'm simply going to flip this over so we can look underneath here and I'll rotate this. And I'm gonna pull on this median nerve here so we can see all the branches of the median nerve. As we get into the distal carpal tunnel region, this actual specimen has an early division of the third common palmar digital nerve. So this is the third common palmar digital nerve. The median nerve will divide up into its digital branches, its terminal branches, which are the three digital branches, third, second, and then the branches that are going into the first web space. And also importantly, as we're gonna see now, the recurrent motor branch. So if I pull, I'm gonna let this fall down here. And if I lift around, you'll see coming off of the radial side of the median nerve is this branch, which courses, takes a U-turn and has a vertical segment and courses back up into the thenar musculature. And this is the important thenar motor branch or recurrent motor branch. And this vertical orientation is important to note as we're gonna recognize this during our scan, because as you're scanning down the carpal tunnel, looking at a cross section of the median nerve and ultimately cross sections of the digital nerves, you're gonna see a vertical shadow come up from the median nerve and course into the thenar muscles. So that's the median nerve. I'll just point out here, we have on the ulnar side of the wrist, the pisiform on the ulnar side with the flexor carpi ulnaris. And I actually have here dissected out just for reference purposes, the ulnar nerve with the dividing into its superficial and deep branches and the ulnar artery, which eventually becomes the superficial palmar arterial arch and goes across. So that'll be the end of that demonstration. So we'll go back to, we're gonna move on to the cadaveric specimen and talk about the scanning protocol. So let me move this out of the way and we'll go to all probably, and actually the double picture for us. So let's talk about the scanning protocol. And you'll see here that we're gonna have, we're gonna be using some slides plus some, we'll have some camera views that show the angle of the transducer. Next slide. And let's go to all first. So what we have here is an overhead view and a cross table view. So you can see how I'm manipulating the transducer. And when I'm starting my examination of the carpal tunnel region, I always start at the distal wrist crease. I place the transducer right across the distal wrist crease as shown in the left lower corner. And that would bring me right to the pisiform and the scaphoid, which are the proximal osseous borders of the carpal tunnel region. And these are gonna give us our two pictures that we're most interested in for the diagnostic examination. So what you have there on the screen is, as I place the transducer right horizontally over the distal wrist crease, I look as we always do for osseous landmarks, we've heard it before at different times for these sessions. And I'm gonna freeze this screen. And what we have on the screen is, we'll go to the double now. Yep, two. So we have the ultrasound image and then a correlative cross-sectional image. So let's look at the anatomy because everything on your protocol is actually right here with the exception of the radial artery. So this is the osseous border of the scaphoid, which is here and then superficial, but I got a little anisotropy here, but this would be the flexor carpi radialis tendon and cross-section. On the ulnar side, we've got the rounded border of the pisiform. Now note how the proximal borders of the osseous tunnel are rounded, right? The pisiform and the scaphoid are round and they both have a tendon on top. The FCU tendon is a little bit flatter than the FCR tendon, but these are very distinctive landmarks. And then in the center here, which is not resolved on this image, but you'll see as we get dynamic palmaris longus right in this area. Now, deep to that, you have the arcing of the transverse carpal ligament, which is starting to form. It's thicker in the distal tunnel. Right here on the left side, which is radial, you're gonna have the median nerve that's tucked in, and here's the median nerve on the cross-section. And these are all the typical fibular echogenic short axis views of flexor tendons. The FPL tendon tucked in over here is a little bit anisotropic, but you basically, and then the ulnar neurovascular bundle is right next to the pisiform. So in a live person, of course, you'd see the beating of the ulnar artery here, and these are fascicles of the ulnar nerve. So you actually have all the structures on the checklist with the exception of the radial artery right here. And this is one of the two views that everyone is expecting to see in the tunnel. So let's go to all. Now I'll go live, and I'm gonna scan to the distal tunnel, which is the second view I get. Now, I want you to keep your eye on the ulnar side of the image, because the pisiform is gonna give way to the hamate. As I scan distally, I'm looking for the pisiform to disappear, and I'm watching the lumen of the ulnar artery, and the lumen of the ulnar artery will lead me to the hamate. Now, this is important because a lot of people miss the hamate because it's kind of deep, and you only see the peak of it because it's not round like the pisiform, it's angulated. And so a lot of people blow by the hamate and get very confused. And I instruct people, follow the ulnar artery, because the ulnar artery will lead you to the top of the mountain. It'll lead you to the top of the hamate. So I find the hamate, and once I get the hamate in view, another important thing to do is to make sure that we get the trapezium, which is on the radial side, and the hamate horizontal across the screen. And this may require a little bit of a heel-toe maneuver if you look at the cross-table view here. And then you're gonna do your tilting maneuver, as you can see in the cross-table image, to make sure that you control the anisotropy. And we're gonna stop with this image here, and I'll freeze this, and we'll talk about it. So let's go to the two. So now we have our correlative cross-sectional image, and the next slide on the next, there we go, yep. So we have our correlative cross-sectional image here with our ultrasound image, and we have the hamate on the ulnar side with the ulnar artery on top. Here's the ulnar artery. Now the ulnar nerve has divided into its superficial and deep branches, and we can see those in the cross section here. And then on the left side, which is radial, we see some of the thenar muscles coming into view over the transverse carpal ligament and the trapezium. We can't see it here, but the FCR is anisotropic tucked in under the tubercle, the trapezium, and then the FPL and the flexor tendons and the median nerve in the distal tunnel. Now, sometimes, we did a good job here today, but sometimes lucky better than good, because sometimes it's really difficult to see the median nerve in the distal tunnel. And there are two kind of scanning things I wanna convey here. First of all, in the distal carpal tunnel, I often will increase the gain in the far field by using the TGC, because the distal tunnel is deeper, and there's a lot more soft tissue interfaces superficial to the distal structures here at the level of the hamate. So I don't wanna increase the gain throughout the field, because that makes everything too bright. But I'll take the TGC or DGC, or however you have it on your machine, and I will adjust the image to optimize the ability to visualize the carpal tunnel contents in the distal tunnel. And then I'll keep that setting throughout the remainder of the examination. The second thing is if you have trouble seeing the, as I go live, and you can stay on that slide there, Jacob. As I go live here, if you have trouble seeing the median nerve in the distal tunnel, then simply go proximal till you see it. So go back to the proximal tunnel, and you'll see it very well in the proximal tunnel region, and get your eye on it, and then just follow it into the distal tunnel. And you'll be able to see it better once you get your eye on it. And so that's another trick for individuals who are having trouble in a particular patient seeing the distal tunnel region. So I saved both of those views, and now we'll continue on with the next slide. And then I'm going to go to the median nerve. So I've taken my standard views of the proximal and distal carpal tunnel regions and documented that, and now I'm going to go find, do what I need to do in the median nerve. So I'm scanning proximally as you're watching the video, and the bone on the bottom of the center of the screen is the lunate bone, and the lunate really marks the carpal tunnel inlet. So this is the lunate bone. Notice that the lunate is proximal to the pisiform. I've scanned distally to see, and you can go all for now, actually, yeah. So I've scanned distally to see the pisiform. I'm going to go proximal and distal in this region until I find where the median nerve is the maximal cross-sectional area. So I say right here, well, this median nerve looks like it's getting a little big here, and so I'm going to freeze my image here, and I'm going to measure the median nerve cross-sectional area, and you can go to the next slide. And my algorithm for measuring cross-sectional areas on the bottom right of the screen, and I'm going to get my cursor on the ultrasound machine, and I'm going to use the continuous trace function. I'm not going to really try to be precise in the interest of time today, but I'll circle this nerve, and the cross-sectional area of this nerve is 10 1⁄2. So I say if it's less than 10, it's normal. If it's greater than 12, it's abnormal. If it's between 10 and 12, I like to get a second test to kind of help me increase my accuracy. And so in this case, I will go to the pronator quadratus and measure the wrist pronator quadratus difference. So I'm going to go live, and I'm going to move from this area where I measured the nerve proximally to the pronator quadratus. Now, what you see on the bottom of the screen, on the left is the volar surface of the radius, and on the right is the volar surface of the ulna, and then you have the horizontal fibers of the... I'm going to reduce the overall gain here a little bit. You see the horizontal fibers of the pronator quadratus, and the median nerve is right in the center, and I will measure here once I get a good perimeter around the median nerve. Technically, you can measure all different places on the pronator quadratus. I just consider anywhere on the pronator quadratus sufficient. And so the median nerve here is six, and the wrist pronator quadratus difference in a non-BiFID nerve should normally be less than two. So the difference here is actually 4 1⁄2, right? It was 10 1⁄2 at the wrist and six at the pronator quadratus. So the wrist pronator quadratus difference is 4 1⁄2, which exceeds the limit. So I would call this median nerve enlarged at the carpal tunnel inlet. So that's the algorithm for measuring the median nerve, and we'll go to the next slide in the right lower corner. So I'm going to bring your attention to one other thing. Some of you, the astute observers, may already have noticed there's something funny about the median nerve in our cadaveric specimen. I'll get you a better picture of it because right here just to the ulnar side of the median nerve is another thing, right? And this could be a couple of things. It could be a persistent median artery. It could be a palmar cutaneous branch of the median nerve that lost its way, or it could be a fascicle of the median nerve that left early, which I'll call a rogue fascicle. In this case, I can tell you I traced it because that's what you would do, and it's a persistent median artery. So that leads us to this discussion of a BiFID median nerve. And the picture of the BiFID median nerve on the bottom right, and we can go to two, yep. And so what we have here is a BiFID median nerve. You will encounter these during your scans. They're very common. They're typically accompanied by a persistent median artery of variable size in the middle of the two branches. And oftentimes the radial branch is bigger than the ulnar branch, but they can be variable. This whole relationship can be variable. And you just need to note these things because you need to know where these things are. Importantly, if you're measuring cross-sectional area, you measure each one independently and you add them. I still use my same criteria for the basic measurement, meaning greater than 12 abnormal, less than 10 normal. 10 to 12, I get the wrist pronator quadratus difference. And here, greater than four millimeters difference, I give it a little bit more leeway based on the literature, greater than four millimeters difference would be enlarged. So just recognize that this will occur. This happens to be a non-BiFID median nerve with a persistent ulnar artery, with persistent median artery, which can occur. And typically if there is a persistent median artery, it's on the ulnar side of the median nerve as it is here. And in a live individual, you may see this even pulsate. And of course you would follow it proximally and distally and determine unequivocally that it is an artery. And so I didn't include it in our cross-sectional measurement. So we'll go to the next slide. We'll continue on with the scan now, and we're gonna find the palmer cutaneous branch. So we measured cross-sectional area approximately. And after I get this cross-sectional area measurement, I simply scan proximally and look for the point at which the median nerve is whole in the distal form. And then I scan distally, and I look for one or more fascicles to come off the radial side of the median nerve and start making their own way up towards the flexor carpi radialis. And you can see one fascicle right here above the pointer. And that, if I continue distally, you can see that the median nerve is gonna take a turn to the right and go into the carpal tunnel. But this fascicle here is gonna stay. Look at the flexor carpi radialis and the palmaris longus here. It's gonna penetrate the antebrachial fascia eventually and go right next to the flexor carpi radialis. And so this is a palmer cutaneous branch in a typical location and with a typical appearance. As I'm looking for the palmer cutaneous branch, I can pick up the radial artery and look for volar wrist ganglions that are located in this region. So that kind of helps me finish the checklist there. So let's do the next slide. So on the right lower corner here, as I keep the palmar cutaneous branch in view, I'll get a nice picture of it here for you and freeze my ultrasound image. The palmar cutaneous branch in the ultrasound picture is here. This is demonstrating a palmar cutaneous branch neuroma. This nerve can be injured iatrogenically. It can be injured with acute trauma. It can be injured with chronic repetitive trauma. And you can also have asymptomatic findings. You can see that as this, there are three branches of the palmar cutaneous nerve here between the FCR and the median nerve. And as I'm moving back and forth, there's a branch going through the transverse carpal ligament that gets acutely thickened as you'll see. And that any focal enlargement of a nerve by definition is a neuroma. And so you have to call that a neuroma. They're not always symptomatic, but you have to know that it's there. And document that it's there. And then you need to decide clinically whether you think that's contributory or not. As we said, that's not part of carpal tunnel syndrome, but can certainly confound it. So we'll go next. So then we're gonna move on to the thenar motor branch and I'm gonna go live. And I'm gonna keep following our median nerve. I'm back into the tunnel. Notice I have a V at the top of the screen on the ultrasound image. And I'm gonna keep the median nerve under the V as I move through the carpal tunnel. So now I'm kind of getting into the distal carpal tunnel region. And as I get to the distal carpal tunnel region, I'm gonna notice again, the trapezium on the left side, the thenar muscles, a very thick transverse carpal ligament. And I'm gonna start looking for this median nerve to widen because it's gonna start dividing into its terminal divisions, right? And we can see it widening right now. It's gonna be a third, a second, and a first digital nerve. But here, and we'll go to next slide, on the right lower corner, we have a down the pipe view of the hand of the carpal tunnel from the perspective of the second inner space. And what you'll see is you can see that this is the recurrent motor branch going vertically as we pointed out in the cadaver. So I'm seeing cross sections and you can see this on the screen right now. I'm seeing cross sections of all this, but I'm looking for a shadow to come out from the median nerve. And right here, that's what we're seeing. This is a shadow, the refraction shadow of the thenar motor or recurrent motor branch arising from the median nerve and coursing up into the thenar muscles. And there's a couple of different ways you can optimize that image. If I'm rotating on it, you can kind of see a curve right around. Thank you, Jacob. And I refer you to any of the papers that have been written on this. But we need to evaluate this for dramatic thickening, compressive lesions, tumors, all sorts of things. I think it behooves us to include this in our protocols when we're doing carpal tunnel. Yep, so we'll go to the next. And so this is the thenar muscles and this always reminds me to look at the thenar muscles for atrophy. And we'll go to the slide here. It'll switch here in a second. Sorry about that. And what we have here in the screen is an extended field of view image demonstrating thenar muscle atrophy relative to the hypothenar muscles. And if you see this, as I mentioned earlier, this definitely tells you that there's axonal involvement of the median nerve. So we'll go to the next slide. And then I take a look at, then I do some proximal distal scanning. So we'll go to all. And the last thing I do in the transverse view, and we're not gonna spend much time today on the longitudinal view because it's just really correlative image, is that I scan proximally and distally. So we've kind of looked at the median nerve and all its branches. And I scan proximally and distally, looking at everything to make sure I didn't miss anything. Is there any anatomic variations, anything that strikes me that I wasn't seeing when I focused on things before? And this is where I'll do my flexion extension of the fingers to see if there are any masses or evaluate the subsynovial connective tissue. And we'll go to the next slide in the bottom right-hand corner. And what you'll see in the bottom right-hand corner is an example of lumbrical muscle intrusion. So what we can see here on the screen is when the person flexes, there's this large muscle belly that comes into the carpal tunnel and actually makes it to the proximal carpal tunnel in this individual who has lumbrical muscle intrusion. Muscle intrusion is very common. I usually only call it potentially significant if the lumbrical makes it to the proximal tunnel or the FDS makes it to the distal tunnel or there's obvious mass effect. So let's go to the next. And we'll go to the next slide after this. Because I'm going to just rotate here and show you a longitudinal view of the carpal tunnel. I have distal to the left and proximal to the right. And across the center of the screen, you can see the median nerve underneath the transverse carpal ligament. Now, normally the median nerve is going to be a uniform thickness, but you may see here what we call an hourglass deformity or a notch sign. You can see thickening proximal to the tunnel, narrowing in the tunnel, and thickening distal to the tunnel. Otherwise, this longitudinal view is really just confirming what we've seen in a transverse view, which is why I'm not spending any time on it today. And we can go next. And so finishing up with our patient, going back and we go to just straight slides. So this is the transverse scan of our patient, which is the primary view here. It'll take a second to boot up. And what this individual had is median nerve enlargement in the proximal tunnel. So it definitely fit the bill for carpal tunnel syndrome. He had a little bit of eccentric fluid around the flexor carpi radialis tendon sheath, but the FCR was otherwise normal. This was so loculated, it might even be called a ganglion, but it was inconsequential and everything else about his exam was entirely normal. So let's talk about his report as we finish up. So I, like Jake, two weeks ago, I usually use a prose type of report and I start out with what I did, what the procedure was, complete diagnostic ultrasound of the right volar wrist region. I have the indication, and this is kind of my cookie cutter. This tells them what I did. So this usually doesn't change, but you'll see all the verbiage for the checklist is in here. It basically says, I did all these things. I looked at all these things. I checked all the boxes. And then I go to the next slide and then I get into my findings. So in this case, the median nerve is enlarged at the inlet where the nerve measures 14 millimeters squared. I give the normal values. It's hypoechoic with reduction in the normal fascicular architecture, small amount of eccentric fluid around the FCR sheath and no other FCR pathology. And then the final impression. So take home points today that ultrasound is a very powerful clinical problem-solving tool in the volar wrist. There is a strong evidence base for using ultrasound to help in the diagnosis of carpal tunnel syndrome. And most of the time, I think that we're doing complete examinations. You could always measure the median nerve and just leave it at that, but I think you're missing the boat on a lot. And you could efficiently perform a complete examination in really less than five minutes when you get your rhythm down. So with that, I'll thank Doug and Maderek and Ryan again. I guess if we have time, we'll take a question or two. All right, Jay. Well, you just set the new bar for the presentations. I'm expecting all the fellows to have Dr. Smith's format here. So I do- People drop off the list. Yeah, I do have one question, Jay. So I morphed into just measuring the maximal cross-sectional area of the median nerve wherever it lies. And I would say a significant amount of time it's proximal to the transverse carpal ligament. And so I know a lot of the studies probably just because of study design have exactly a specific point that they measure. But for me, I just measure the largest area wherever I see it. What are your thoughts on that? Yeah, I mean, I agree. And everything you said is true. Many studies will choose to measure it at the pisiform no matter what, even though that might not be where it's maximally enlarged. And I guess they do that for reproducibility, and that's fine. I agree with you. And between the lunate, which is proximal to the pisiform and the pisiform itself, that area I call the carpal tunnel inlet, and I will measure it there. And wherever it's maximal is where I'm going to take it. And if it's right at the pisiform, I'll certainly dictate that in my report just in case I do a follow-up later. Otherwise, I'll say it's at the inlet, which means it's probably proximal to the pisiform. And I think it's important to note that although some of them may be swollen distally as well, it's hard to standardize cross-sectional area measurements distally because the nerve divides into its terminal branches very variably. And so it always looks big when it's dividing into its terminal branches. And so it's hard to kind of standardize that cross-sectional measurement. So I agree. And I think it makes the most clinical sense to me to just measure it at its maximal cross-sectional area in the proximal carpal tunnel region. Yeah. Well, I just want to echo your points about efficiency. I know in our organization, a large organization, we are slowly transforming the workup of carpal tunnel, and it's now a minority of people that are getting electrodiagnostic studies. And again, echoing Jay's point here, I mean, you can efficiently do this in five to 10 minutes. And also anatomically identify any lesions that might affect the choice of, let's say a carpal tunnel release or so. So any other questions from anybody else? Well, again, Jay, thank you very much. And again, this is going to be on the AMSSM YouTube website, and we look forward to seeing you in a couple of weeks on January 8th for Achilles tendon case from Jeremiah Ray. All right, thanks everyone.

3rd Edition, CASE 58

3rd Edition

Wrist

musculoskeletal ultrasound

carpal tunnel syndrome

median nerve enlargement

ultrasound diagnosis

anatomical structures

muscle atrophy

electrodiagnostic studies