of our technologist courses. It's open, of course, to everyone. I'm Sam Berner. I'm the outgoing chair of the Technologist Education Committee, co-chair of that. I want to welcome everybody to Phoenix. We're going to have three speakers. We're going to allow 25 minutes for each speaker and then time at the end for questions. Jot them down and save your questions for the end, please. We have our first speaker is Jim from Minnesota. It's always nice to be introduced. Why do I do that, by the way? Does anybody know why I hate to be introduced? If you try to sit up there and read my accolades and all that stuff, I'm going to interrupt you. Do you know why that is? Because I'm exactly the same as you. I'm no different. I've lost more hair, but we all started doing the fundamentals. That's really what this is. This is talking about those things that we do to get the best data to do the right things for our patients. This quote, I always start every presentation with a quote. What does this quote have to do with anything? Does that say nerve conduction anywhere on there? Why is this relevant? Because I've been doing this for 125 years now, what's the difference between me as a technologist and a physician who's going to come in and do the needle portion? What's the difference? It's how we look at things, isn't it? See, as a technologist, I'm going to give the very, very best waveforms I can. I'm going to struggle to give the best waveforms. Has anybody ever done that? You've spent 10 minutes getting that perfect lateral cutaneous nerve of the forearm. Has anybody spent 10 minutes getting that, and then you've got a paper and you present it to your physician, they say, that's okay, I kind of expected that. You sit there and say, I spent 10 minutes getting that. It's because our physicians think differently than we do, don't we? We think like techs. They think like clinicians. They're putting pieces together differently than we do. That's a good thing. That makes us a great team. There we go. That's why this presentation, because the way we look at things, it's really important. When I talk about this presentation, it's really all about the fundamentals. We were just talking up here. How many of you guys, when you drive home from work, there's a stop sign somewhere along the line. Maybe it's a couple blocks from your house as you enter your neighborhood or something like that. Then you get on home. You park and you get busy doing the things we do like fixing dinner, making sure the kids get to where they need to be, or whatever it is. If I were to ask you, did you stop at the stop sign, what would you say? I don't know. Because you do it every time. It becomes a fundamental. That's what we do in nerve conductions too. Here we go. Raise of hands. Everybody ready? You woke up this morning. You're probably having a great dream. It's a fantastic dream. You wake up and what's the very first thing you thought about? Ohm's Law, right? No? This might be why I don't go to very many parties on Saturday night. It is one of those stop signs in our business, isn't it? If I'm going to get good quality data, I got to follow the law. In this case, Ohm's Law. If I'm going to get good data, what do I have to do? I have to make sure that the surface is clean, so I might have to wipe up my patient a little bit. I might have to take a little alcohol, especially in the feet. How many people have seen a diabetic foot lately? Oh boy, they're fun. We have to make sure our electrodes are, we have gel on our electrodes, that they're nice and secure. These are the fundamentals. This is the principle of Ohm's Law. Because if I can't do that, I can't get good data, and then I'm going to walk in with those ideas for my physician, and what are they going to say to me? Go back and try it again. That's what this is all about. What is the number one thing we struggle with? By the way, has everybody got Preston Shapiro's book? This is on about page six. If you'll notice on the flow chart here, it says Cardinal Rules of Nerve Conduction, EMG. It says, when in doubt, think about technical factors. I will say that over and over and over again, because you know, a lot of times, the problem is between the keyboard and the back of the chair, isn't it? That's why I'm qualified to stand around here and talk about this. You know why? Because I bet you I've made more mistakes than all of you combined. I've made a ton of mistakes. I live this. The problem's between the keyboard and the back of the chair. The number one problem we struggle with in our labs, anybody got a guess? Electrical interference. Anybody struggle with that? Certainly in the needle, when we're using monopolar needles. Oh gosh, is that tough sometimes, right? We got to move the reference? You can't just leave it in one place? Holy cow. Electrical interference is probably the thing I deal with most. There you go, Ohm's Law. This is the fundamental. This is the stop sign. We got to be able to put the wires on. Electrical interference, called noise. There's really two kinds of noise that we see in our EMG lab. There's the electromagnetic force. That's the noise all around us. If I hooked up a sensory nerve on you right here, right now, what do you think I'm going to see in this room? Noise. I mean, I've got 120 volts everywhere. Every outlet. And just to get the system over here close enough to you, I'm going to have to run an extension cord. That's bad too. I get a lot of electrical noise from the environment. That's EMF. The other noise is, oh, and it makes sense. If you were to call me up on the phone and say, Jim, I'm getting electrical interference in my machine. What am I going to say to you? Of course you are. Of course you are. If you think about this for a minute, you're measuring serial nerves that the normal values might be 5 or 10 microvolts. And you're recording them in a room surrounded by 120 volts. Of course you have electrical noise. Electrical noise is all around you. What I think is amazing is when we get good data. Because that's actually quite a bit harder. Again, we're practicing the fundamentals. What's the other kind of noise besides the oh, so here's how I describe this. If you guys were a bunch of 8th graders and I was giving this talk to you guys, because you're all smarter than 8th graders. There used to be a game show. Did anybody see it? Are you smarter than an 8th grader? No, that was a 5th grader. I would say to you, you're on your way to work this morning and you hear a good song on the radio. What do you do? You turn it up. You turn it up to listen to it. Picture this. It's a great song on the radio. Instead of turning the radio dial all the way around once, you turn it all the way around 100,000 times. Is it still a good song? Probably not. And yet that's what we do every single day. Every single day in our labs, that's what we do. We do it. This is just a busy, busy slide. First rule of PowerPoint presentations is don't put too much information on a slide. I broke my own rule. So these are just some of the things we can do. How many people struggled with noise in your labs? I was going to say, if you don't raise your hand, I think you need to go back and try harder, because it is everywhere. So here's an example. What do you see here? Problems? I get a couple of seral nerves. It's pretty good, right? Pretty good. I can turn that in. Everybody agree? Yeah, you can. You know, one of the funny things in my...you know, when I do presentations, I often go back and look at data I've recorded before. And I'm finding stuff, right? And what I find is as I look at it in reverse, I look, I accepted that. I can't believe I accepted that. But I kind of know in my head, maybe that's been the best I could get at the time, or I wouldn't have quit. I would keep going and keep going until I got it perfect. That's my job. Well, here, you see that sloping baseline? You see how it kind of slopes? Well, in sensory nerve conductions, we're recording with a sweep speed of only about 10 milliseconds on the screen. So if I've got 60 hertz artifact, and since we're all from either Canada or the U.S., that's why I had to walk around, this is what we would see if we have electrical artifact, if we have EMF noise. Okay? So what would I see in a sensory nerve conduction if I'm looking at 10 milliseconds? I'd see one-sixth of one cycle. I don't see the 60 cycle. Okay? So if I change the sweep speed and turn it out so I can see 10 milliseconds or 100 milliseconds on the screen, what do I see? I count them. I have six of them. And now I've got 100 milliseconds. That's 60 cycle interference. Okay? That's electrical interference. Okay? And that's when I move the bed away from the wall. I unplug the bed. Holy cow. I had one just a couple weeks ago. Somebody called me. I happened to be in California visiting my grandkids. And the call came in from somebody in Florida. I said, did you unplug the bed? Oh. I don't know. These things. So that's 60 cycle. And that's why in sensories we don't always see it. Now picture yourself with the EMGers in the room. You've got a needle and you've got it in their arm. What would you see? A whole gob more of those. You'd see a lot of them, wouldn't you? Because you're looking at a longer sweep speed. And they're easier to see. So why does that work the way it is? Well, we talked about amplification. We certainly amplify these signals. But wait a minute. I just said that these signals that we're amplifying are 100,000 times bigger than the physiological signals I'm getting from the patient. How in the world can we do that? Ready? Practicing the fundamentals. Right? Getting those electrodes on in the right place. Getting them on securely. Plugging them into the right place on the amplifier. And then letting the amplifier do its job. Okay? And in all the systems out there today, we're all using digital amplifiers. Okay? Now, anybody old enough to remember the first cell phone you had? You know, nine pounds. You had to wear it across, you know, like a purse. And it was analog. You couldn't even talk on it. You couldn't hear a word. Because all you hear is in the background. Well, the same things happen. When I got in this business, that's exactly what we used. All I saw was this. Now, we have these really great amplifiers. And we measure the difference between the active recording electrode and the reference recording electrode. That's what we're doing. We're measuring the difference between those two. Okay? So we need them to be relatively equal. Going into the amplifier so that when I amplify it 100,000 times, I can actually see something. Right? That's the principle. And so what we do is we reject the common signals, which is the noise, we send them to ground, and then we record just the difference between the two, which is that 5 microvolt seal. Okay? Simple. Right? By the way, I'm just about getting warmed up now. And the last time I looked at that clock, I had about five minutes. Has anybody ever seen me talk before? Has anybody ever seen me finish on time? That's exactly right. It's never happened ever in my life. So not a problem. Okay? So a couple of things. First off, this is really, really, really, really very common sense stuff. How many people played sports at some time in your life? Maybe in high school or college. And what's the first thing you did at the new season? Okay? So let's say it's soccer. How many of you went the very first practice in the new season, and you started kicking goals? No. You go back and practice the fundamentals. First you learn how to pass. First you learn how to work as a team. Then those things come later. What I'm saying is all of this stuff is the fundamentals. Okay? So what's my time say up there? I have 11 and a half minutes? Oh, I'm not even late. Oh, it's counting backwards. Ah, very good. Oh, we're in great shape, guys. So that's a differential amplifier. I have my active recording electrode over the point of interest, whether it's a motor or a sensory. The reference electrode is going to be more neutral. We can all debate on what neutral is some time, probably after a couple of dull beverages, because we won't necessarily agree. But this is a differential amplifier. Okay? And that's why impedance, and that's why the first thing you'll think about when you wake up is Ohm's Law. Because if I have an equal impedance in those two, the common mode rejection and differential amplifier is going to work better and I'm going to get better data. Cool. And I'm going to have less electrical noise. How is that? And you do it all the time. So common mode rejection ratio. Filters, we use filters. How many people remember the filters you use? Can anybody tell me the sensories? Okay, so just like that analog cell phone camera, or that cell phone, analog cell phone that we carry around, you can make calls by the way, you can check in your email, no way. When I've gotten this business, we did dial those in. We had to. We used an oscilloscope. If you wanted to make a permanent record of what you did, you had to take a camera and take a picture of the oscilloscope. Now that was fun. We also had two hours for every patient. We didn't do this half hour patient stuff, but that's okay. So know your filters. How many of you use notch filter? Good. I love that answer. Because what happens when we're doing long latency responses and use a notch filter? Has anybody done it? Anybody record F waves and turn on the notch filter? Don't do it to your patients, but do it to yourself just for fun to see what happens. It's what we call a ringing effect. It actually causes noise. So this is with the notch filter off, and you see the F wave. I turn on the notch filter and I get this ringing effect. And I look at these reports. Somebody sends me a report and says, what do you think here, Jim? And I look at that and they've got the marker on that second little cycle. I say, yeah, do notch filter on. Turn it off. He said, I can't turn it off. I can't record. And what do I say? Practice the fundamentals. Go back. Clean off. And every single resident, every single fellow that ever rotated through my lab, they would say, I'm not getting the data I expect. What's the first thing I say to them? Take all the wires off. Scrub the patient up. Put all the wires back on and try again. Practice the fundamentals. Okay? It is so, so important. So, some pitfalls. Here we go. We're finally to the lecture, by the way. What have we done so far? Everybody remember your grandfather when you were a kid? You remember the stories your grandfather told you? I became my grandfather. If you want to hear stories, let me know. I can tell you. I can tell you about that doctor I went to see in Southern California who didn't put a reference on at all using a monopolar needle. I've got the stories. Or the one who took the, you know that power brick on your laptop computers? That brick that converts the different energy for the different countries? Tied his amplifier cable to it. These are great stories. I have till midnight, right? Okay. Okay. So, what's wrong here? This is real data. What's wrong? What's that? Where do we start? What could it be? Well, where's the ground? If I can't put the ground on, how can I record the data? Well, it's better today than it used to be, believe it or not. You can actually get by with it sometimes today, especially on motors, but you can't even check the impedance. You have no idea what the impedance is because that ground is what it uses. So what is the ground's most important job? It's to take out some of that electrical energy, some of that shock artifact, okay? Just like the ground on the plug takes out the excessive energy in the room or in the circuit and it grounds it, sends it to ground, so does that ground take out some of that excessive electrical energy from the stimulus, okay? So put the ground on. Oh, what did we forget here? Everybody ready? Impedance! Impedance! Now, we don't often abrade the skin like we do in some other procedures, but we must. We absolutely must use gel. Now a lot of us have moved to the disposable electrodes and they're pre-gelled, so we kind of forget this step, right? It's the stop sign. We forget this step, but if you don't do this, you're not making a good contact with the skin. If you don't make a good contact with the skin, you're probably recording with a high impedance and your common motor ejection ratio is not working like it should and you get it. Everybody know what that waveform was called? I'm from Minnesota, so you can forgive me. It's called poopy. That was a poopy waveform. I can't give that to my doctor. He's going to send me back in there and make me do it again. How many of you guys have ever done a lateral femoral cutaneous nerve or the lateral cutaneous nerve? And you love them, right? You so want to do more tomorrow. And so here's a great technologist, okay? This is Jim, sorry, not a great technologist. So I go in there and I go, stim, stim. No response. Sorry, doc. I couldn't get it. And what's my doctor say? Jim, how hard did you try? Go in and try again. Hate him. Anyway, so now I just put some gel on and look at that. I've got a better waveform, right? I can turn that into my doc, right? So I got a thousand examples. What's wrong here? Same principle. I've got a high impedance. In this case, I just have a wire that's hanging half off. So look at all the things I have to remember. I have to remember to put my wires at the right place anatomically. I have to remember to put them on securely. I have to use gel. And here it is. I have to tape them down too. Holy cow, there's a lot to remember, okay? This has to be low amplitude, right? Axonal loss. I'm going to send them off to the internist for maybe some insulin or something, right? Well, in a differential amplifier, I can get phase cancellation if I put my electrodes too close together. Oh, wait a minute. I've got to put my wires on. I've got to put them on good. I've got to put them on in the right place and I've got to put them with the right separation too. Holy cow, there's a lot to remember, okay? Same thing here. What happened? So in this case, my reference electrode in a motor nerve conduction is actually in the hot zone, isn't it? It's in the active recording zone. So here I've got a signal and I've got a signal in the reference that looks similar and they phase cancel themselves, don't they? So I get a smaller amplitude than I should. So our reference electrode in motor nerve conductions needs to be off the motor point, usually a bone or tendon, right? It needs to be as neutral as we can make it, okay? Is this all review? This is why we talk about it because of course it's review, but yet it's so important and every time someone calls me up, says, Jim, I have a problem, I go back to my fundamentals. This is where I start every time, okay? So if that's the truth, why don't I just put the reference electrode right here on the nose? Won't that work? Well, it doesn't work either, does it? Because in this case, if I have too much separation, I'm going to allow in more other extraneous noise and guess what? I get a smaller amplitude, okay? So I can't do that either. It's all about consistency. Be consistent. Be consistent. I have a lot of folks, you know, when I'm doing a training thing and you're talking about measuring for your distal motor latency, here's where you stimulate. Here's the electrode you're measuring from, you know, eight centimeters, seven centimeters, whatever you use. If you're at Mayo, 6.5 centimeters because of course they're Mayo. So do you measure from the edge of the electrode or from the middle of the electrode? Are you ready for this? I don't care. Do it the same way every single time. Every single time be consistent, okay? And that's the key. Oh, what happened here? Same intensity. Why is the second trace so much better than the first trace? I don't have the ground in the right place, okay? Remember that ground's going to take out that extra electrical energy just like the extra electrical energy that the ground does in the wall. And if I don't have it in the right place, that's going to be recorded. Now modern machines are a lot more forgiving. It's not like the old days. That's what I had to do to make it really happen. And this, guys, is why I love working with residents and fellows. If you say, hey, come in here. I want to take a picture of you of me making a really bad mistake. They say yes. Okay, anybody who's been in practice for a couple years, how many of you guys would say yes? You'd say, no way, Jim. I know better. Okay, so position of ground. What's it say? What's that? One and a half minutes. Okay, so the good, do it right every time. Do it right every time. So what keeps us from doing it right every time? Usually it's time. Time is our biggest enemy, right? And I was actually using this excuse this morning because this is a real life excuse. You come in in the morning. You've got 18 patients on your schedule, God, I hope not, but you've got a full schedule of patients. And what happens? Your very first patient, they show up 30 minutes late, right, bad traffic. So what does the rest of your day look like? Holy crap, I'm behind, oh my God, I've got to hurry. And then things start to happen, okay, because we quit practicing the fundamentals. You eat lunch over the sink in five minutes flat and then you've got an upset stomach for the rest of the day. That's the way it goes. What did I do wrong here? Here I have my active recording electrode isn't in the right place, right, it's not over the motor point. So I'm getting volume conducted from another motor. Okay, so we have about five minutes for questions. So here's the problem, and this actually kept me awake last night, sad, isn't it, that I have such an unbelievably dull life that this keeps me awake. There will be questions that you get to answer. Guess how many of them I covered, not very many. You'll do fine because just remember the principle of practicing the fundamentals, okay. Now the good, we talked a lot about the bad and how to make it good, and the ugly are just the two examples of accessory fibular, not accessory perineal, old dogs hard to change, and Martin Gruber and Asimov, so that's the ugly part of the conversation. So anyway, here we go. Upside down waveforms, oops. What about the stimulator? What happens if you turn around your active and recording electrodes, two, ten, five, four, three, four, four seconds. Oh, we're done. That's right, we're done. If you reverse your cathode and anode, we used to talk about this a lot over a couple of adult beverages, axonal hyperpolarization and fun words like that. This is why I don't get invited to parties because I talk about anodal hyperpolarization at the party and then I don't get invited back, okay. Definitely you will have an invalid latency measurement, but how much of the negative ions cancel positive ions, really it's probably insignificant, okay. So volume reduction, we talked about that, the problem, got it, and error, the mistake we made, cool temperature, I mean, how many people, there we go, yeah, we're doing great. Okay, there we go. All right, oh, I'm supposed to show this slide, sorry, how do I go backwards, how do I go backwards? I'm supposed to show this slide. Oh, there it is, to claim your credits, I've got to show you that, okay. So, I apologize, but anyone who's ever seen me before knows if they gave me three and a half hours, I would still have the same problem. I would just tell you more jokes along the way. That is true, see, candy nose. Well, thank you very much, Jim, and for those who came in late, we're going to hold questions to the end, and we'll allow time at the very end for all three speakers. Our next speaker is Dr. Dan Simmons, a neurologist from Idaho who is the incoming co-chair of the Technologist Education Committee, and I'll let him get started, we'll have five minutes, and then again, we'll save questions for the end. All right, thanks, Dr. Berner. Like I said, I'm Dan Simmons, let's see, I think he's loading my slides, but I have a, just out of curiosity, how many of you are technologists, just by show of hands, and do we have any residents or fellows? And how about faculty or attendings? A couple, okay. Well, I think this talk is equally relevant to residents, fellows, techs, and also for those faculty or attendings that are coming back into practice that just need a refresher. I have a lot of experience in training residents who have, you know, essentially zero knowledge, coming in with nothing, and taking them to competence, and also the same with techs. As part of my previous position, we had a neurodiagnostic training program across the street that would send us techs, and we would go from really zero to registry. And currently, I have since moved out of that state, and I'm in Boise now, but I'm training my MA to do nerve conduction studies, and it's, again, starting with zero, and hopefully getting to that registry standard. And my hope today is not to necessarily give you an algorithm. I would like you to be able to understand the, like Jim said, the fundamentals, and intuitively know if I get this result, then this is my next step. And even though, you know, many of you are technologists, you still are able to take that initial history, get the where are the symptoms, what are the symptoms, and then design your tests from there. And that can make your clinic encounter much more efficient. All right. So I have no disclosures. And this is a CNCT checkpoint activity, so there is an exam that you can get credit for, and just take note of the highlighted items from this talk as particularly important for that. Okay. So why not this? Why not every patient you see, if they have an upper limb complaint, you just do this for every patient? And I've seen this, and I understand why it's done. It's, you know, in some ways it's more efficient. You don't have to do necessarily, you know, to think about it. You just do the same thing for every patient. Well, one is, you know, obvious. We don't want to be putting the patient under more discomfort than needed. Also, cost to the patient. Every additional nerve conduction study is more expensive to them. And then, you know, there's the problem of false positives. So every test you do, there's a potential to get a falsely positive result. And the more tests you perform, they can add up. There's also this. How many have ever seen this? This is the maximum number table that's produced by the AEM. And this is basically guidelines. So I think more from the auditing standpoint that for a particular symptom or diagnosis, this is what you should be able to get by with 90% of the time. And this can be found on the AEM website. So just a note about false positives. I think it's really important when you're deciding, you know, how many nerve conductions do I need to do to answer the question. So what is a false positive? It's just an abnormal test in otherwise asymptomatic patients. And this is defined by reference ranges in a control population. And the way that this is done is that you get a control population. You find whatever parameter you're looking at. You find the mean. You take a standard deviation. You set the cutoff value if that's where it is, either below or above, depending on what parameter you're looking at. And so, for example, if I'm looking at medium motor amplitude, I take 100 normal controls. So these are patients. They're not patients. These are subjects without symptoms. And you arbitrarily, or maybe not arbitrarily, but you set the cutoff point to two standard deviations below. So you can get a histogram like this, where you're measuring amplitude in each patient or each subject. And then you can see along the bottom, that's the amplitude. And so most subjects are between 6 and 10 millivolts. You fit it to a standard curve. You take the mean. And then you go down two standard deviations, and that's your cutoff value. And you can see that there are some subjects that are going to fall under that cutoff value. And that's what we define as abnormal, even though there are some that are going to fall into that. So this is the false positive rate, and that's determined by your standard deviation. And so that's 2.5% by definition. So just keep that in mind, that a small 2.5% of your patients are going to have these abnormal values based on this methodology. Okay, so if we do a bunch of tests, and we require that only one test is abnormal out of all of them that we do, your false positives rate for each test add up. So if you're doing a carpal tunneling value, do every test you can think of, and you only require that one of them is abnormal, your false positive rate is going to be 15% if you do all these tests, which is obviously unacceptable. But if you require that two tests of those that you did are abnormal, your false positive rate remains low. So the take-home here is we need to recognize that there is error in everything we do. And like Jim was saying, the first thing you think of if you get an abnormal result, especially if you weren't expecting it, is go back and check your electrodes, check your distance, check the temperature. A lot of times it's what you did, not what the patient has done, to get that abnormal result. Limit your tests to the minimum number required to answer the question. Once you've answered the question, you can stop. And then avoid relying on just a single data point. And this is especially important for the clinicians. If your sole diagnosis hangs in the balance, All right, so I'm going to go through some cases here with some examples, and again, my goal is to try to help you understand how I'm thinking through these cases and why I'm deciding which tests to do. Okay, so we have a 40-year-old female presenting with bilateral hand-pair anesthesia for a year. The thumb, index, and middle fingers are most affected. The symptoms do wake her up at night. It's worse with driving and holding her phone. She's frequently dropping things, and she has no neck pain or weakness. So which test do you want to start with? We'll start with the APB. I meant to ask that question before I showed it, but we'll start with this one. So what do you notice here? You don't have to shout it out, but just think about what you're noticing here. So we have, hopefully this looks familiar. This is a representation of an anatus screen. So there's a long latency, right? It's highlighted there. That's a five milliseconds. Amplitude looks okay. Waveforms look okay. The conduction velocity between the wrist and elbow looks fine. So this is kind of going with what you thought it was, which was carpal tunnel. Most of you probably got that far. So what's the next test that you want to do? What do I go to next, and how do I decide that? So I would say the DIGIT-2, and I'm going to explain why I think we should go here. So the DIGIT-2 Antidromic Sensory Study. This is what we get in this case. The latency, again, it's long, 4.7. That's expected based on the median. Now, the amplitude is 9, so that's low, I think, by any definition. Conduction velocity is slow, also expected. Now what do we think about that amplitude? So this matters, right, because if we have axon loss, that makes it more severe. So is there axon loss here, assuming that technically you've done it correctly, you've done the fundamentals? So by show of hands, who says this is axon loss? Some. So if it's not that, then what could it be? Could be conduction block, right? So if you have a low amplitude, this could be conduction block. How do you tell? And this is the reason that I go to DIGIT-2 right after I do my median motor if it's abnormal, because this is the test that tells you about the pathophysiology. So we do the Palmer segment. So is anyone doing this test in practice, this segmental DIGIT-2 study? I see some head nodding, yeah. So this test has the advantage of stimulating in the palm, which bypasses the block if it's carpal tunnel syndrome. And so what do we have here is you see our amplitude in the palm goes up to 30, and that's a normal, right? At least we assume it's normal, and we could really verify that by checking the other side. But if it goes from 9 in the wrist to 30 at the palm, then that is diagnostic of conduction block, assuming you've done everything correctly. And does that have a better or worse prognosis than axon loss? Has a better prognosis, right? So this matters clinically to the patient, and in terms of what your provider is going to tell the patient, hey, if it's axon loss, it's going to take a long time, even if you get this release, to get better. If it's conduction block, that's a better prognosis. You might get relief in a couple of months or a couple of weeks. All right? So I'm a big fan of this segmental study. It's technically challenging. It's hard to do, but it's very useful. Okay, so just to drive home this point, here's the palm and the wrist responses. If we have slowing and the amplitudes are the same, palm and wrist, then you know it's demyelination. If the wrist is low and the palm is normal or higher than the wrist, you know there's demyelination with conduction block. And if there is low amplitude on both sides of the block, then you know it's axon loss. And really, this is the only test that I'm aware of that you can distinguish this, because you're stimulating on both sides of the block. And then I put in here, averaging is highly recommended, because as you're doing those stimulations, that onset latency, that initial dip, is where the computer is measuring the conduction velocity. The more, if you do, you know, say you do 5 or 10 stimulations, that's going to move a little bit. Your waveform might change a little bit. And so by averaging both sets of responses, you'll get just a more stable, more accurate result. Okay, so going back to this case, the ulnar motor and sensory studies are normal. And so the conclusion is that this is a moderate median neuropathy at the wrist. I use the Bland grading system. If you haven't heard of that, it's worth looking into. It's by Jeremy Bland. These papers are from the early 2000s. And I think it's a very nice quantitative grading system. All right, case two. We have a 78-year-old male with numbness and weakness in the hands. And with a decade of symptoms, the entire hand is numb. There's no triggers. It's constant, no neck pain. So I meant to ask you again, but we're going to start with the median APB. And this is the response that we get. So a little different from last time. We have a very long latency, 6.8. The amplitude is low. And the conduction velocity between the forearm and the wrist is a little bit slow, which you can see with carpal tunnel syndrome. This is looking like carpal tunnel, right, again, so more severe, definitely. So I know this is going to be controversial what I'm about to say. And there are experts, I would say, on both sides of this. But I fall on the side of palmar stimulation. So when you have a low amplitude, when you're stimulating at the wrist, it's the same principle as the last, as the DIGIT2 study. So how do you know if that's axon loss or conduction block? You really don't, unless you bypass that block and stimulate in the palm. The danger and why it's controversial is because when you stimulate in the palm, how do you know you're not co-stimulating ulnar? And that's a problem. But I think it can be done. So if you start kind of at the wrist, just past the carpal tunnel and the median area, and if you get a waveform, get super maximal, you're using very small increments. But if you march your stimulator across the wrist towards the ulnar side, you will see a loss of waveform. And then as you approach the ulnar side, you'll gain a new waveform, the ulnar waveform. So these are separate. And you can stimulate them independently. But if it's requiring a lot of current and you don't notice a waveform shift, then it may be difficult to distinguish co-stimulation from this conduction block. So you have to be really careful with it. And it is controversial. But give it a try, and then see what you think about it. OK. So that's just what I was saying here. Use great caution with this. And again, the same kind of thing applies, that if you get a, you know, this matters clinically. If you have someone with low amplitude, that's hand weakness, it helps temper their expectations if they have axon loss compared to if they have conduction block, which is more guarded. And then if you see a clear change in the waveform, then that's going to be ulnar co-stimulation. You don't want to use that. So just another tool in your toolbox. And you know, the providers, the residents and fellows, you're going to use your EMG, the needle EMG, to try to figure this out too. So if you have Fibs and positive sharp waves, and that tells you that there's axon loss there too. All right. So we'll do the median digit two next. And we don't get anything here. And remember that we want two tests to tell us the diagnosis. We don't want to just rely on that first test. So what do we do in this case? So a lot of our other comparison studies are based on this. So we're going to do the median digit two next. And we don't get anything here. And remember that we want two tests to tell us the diagnosis. We don't want to just rely on that first test. So what do we do in this case? So a lot of our other comparison studies are based on this. So we're going to do the median digit two next. And we don't get anything here. And remember that we want two tests to tell us the diagnosis. We don't want to just rely on that first test. So what do we do in this case? So a lot of our other comparison studies are sensory studies. So they're not really going to help us in this case. So pretty severe carpal tunnel, no digit two. What can we do? Yeah, lumbrical anorasia. So this is the ulnar-motor, median ulnar-motor comparison. And we don't get anything here. And remember that we want two tests to tell us the diagnosis. We don't want to just rely on that first test. So we're going to do the median digit two next. So this is the ulnar-motor, median ulnar-motor comparison, where we're stimulating the interosseous and the second lumbrical at the same time, well, not at the same time, but in the same place. We're recording the same place, stimulate median, and then stimulate ulnar. And this is what we'll get. The median is usually a kind of a low-amplitude, broad waveform. In the context of carpal tunnel, it's going to be prolonged, the latency, and then you'll have the ulnar-motor response that's usually more triangular and larger amplitude with a shorter latency. All right. And so the conclusion here is a very severe median erupted at the wrist, which is a blank grade five with both motor and sensory axon loss. Okay. This is a common scenario, a 28-year-old female with three months of hand paresthesias. The thumb and index finger are most affected, no daytime symptoms, no neck pain. Start with the median. I always like to start with the motor because I think it gives you This looks pretty good, right? The latency is normal, amplitude looks good, waveforms are stable. So, then what do we do next? Do a sensory. I would argue in this case that we start thinking about something called the combined sensory index. Anyone familiar with that? Anyone doing that in practice? So, I only recommend this, I think it's very helpful, very sensitive for mild carpal tunnel. If the carpal tunnel is moderate or severe, it's probably too much, and you may not get any responses anyways. But what this is, we start with the digit four comparison, and these are antidromic sensory studies, and you take the peak latency difference between the two. You write that down, remember it. Then you go to the D1. So, this is a median radial D1 comparison over the thumb. You take that peak latency difference, you write that one down. Then you do the palmar, the orthodromic transcarpal or the palmar stimulation, median ulnar comparison. You take that peak latency, write it down. Then you add them up. So, this is an index value that adds the differences between the latencies for all these three tests. That gives you the combined sensory index. This was developed by Larry Robinson, and has a lot of evidence behind its use. In my opinion, it's the most sensitive test for mild carpal tunnel. So, if you're doing your digit two, strolling is expecting carpal tunnel, and it's normal, you can always try this combined sensory index. And so, in these cases where the median motor is normal, it's automatically gonna be mild if it's carpal tunnel. And so, I go straight, if my median motor is normal, I go to the combined sensory index, and I do that one. So, again, we're looking at peak latency differences. Like I said, it's best reserved for mild carpal tunnel syndrome. It is resistant to cold temperatures, and this has been tested, because all those segments that you're testing are in the same areas. And so, the cold is gonna affect the median ulnar radial the same. And because it's an index value, it avoids that problem of additive false positive rates. And they've been able to show that the combined sensory index is more sensitive than using any one of those component exams alone. So, this is a very mild median neuropathy at the risk of bland grade one. Okay, we've got a couple more cases to show you. We have a 38-year-old male with numbness and paresthesia of the fingers for six months, involving the fingers you see there. Mild weakness for the last two months, and then intermittent discomfort of the medial elbow. So, I'm sure all of you are thinking this is probably gonna be a ulnar neuropathy at the elbow. So, I record ADM first. I think most of you probably do, too. And it's really important to have the elbow in a flexed position with the arm abducted, because that will lengthen out, or straighten out the nerve. It eliminates that redundancy that you can get if the limb is bent. And the ANAM reference values are probably a little bit different from what you might have in your lab. They're very conservative, I think, accounting for that possibility of error with measurement. So, with our patient, this is what we get. The waveforms look stable. The amplitude... Anybody have a problem with the amplitude dropping? Kind of non-committal. I mean, from 11.5 to 10.6, you kind of see that there's maybe some phase cancellation. What about from 10.6 to 9.4? Maybe a little more than you expect, but you kind of pass it, you're in a hurry, and maybe did it wrong. What about the conduction velocity? It's not really meeting that threshold. So go back to your history. You're expecting to see slowing here. So if this was a carpal tunnel patient, you may not chase this down, but you're expecting to see slowing here. So what's something that you can do to try to clarify this? Yeah, you can do inching studies. And so why would we do these? These are terrible, right? When you're attending comes in and says, can you do inching, you're like, yes, I would love to. So you can detect focal slowing that was otherwise diluted over a longer distance, and you can localize more precisely where the slowing is, and this has clinical implications. If it's more distal, then it's a higher likelihood it's entrapped in the cubital tunnel, whereas if it's more proximal, like proximal to the medial epicondyle, it's more likely to be a stretch or compression injury at the retrocondylar groove. And these are managed differently, potentially. So technically, it's helpful to do preliminary mapping with submaximal stimulations. You can do this all beforehand, or you can do it as you go, using that sliding stimulator technique where you're submaximally locating where exactly the nerve is. This is important for measurement. And you're marking off at the medial epicondyle, four centimeters distal, six centimeters proximal, and then making two centimeter increments along the nerve, and it's really, really important to just use just supermaximal stimulation. If you're starting out at 100 milliamps, then you don't know how far that current is traveling down on the nerve. And so that can really mess up your latencies and your distances. These are very small measurements, and so there's a lot of room for error here. And remember, we're using latency difference. We're not using conduction velocity, so don't even look at the conduction velocity. We're looking at the difference in onset latencies of these motor waveforms. And then you can take note of any amplitude area changes, see if there's conduction block. Excuse me. All right, so this is what we get, and you know, those amplitude changes that we looked at that were kind of unimpressive before, what do you think about them now? So it's not really an incremental decrement. This is a focal change, and we see that focal change, even though it's not very much, that's suggestive of partial conduction block. And then on the latency segment, there is a, at that same segment where we saw that drop in the amplitude, we see a prolongation of that latency at 0.8, all right? So initial study is kind of unimpressive. You could probably pass it if you're in a rush, but then doing the inching studies really helps bring that out. Okay, the D5, now you can do D5 sensory stimulations across the elbow, again, technically challenging, helps to average. But here, also, you know, we expect some phase cancellation to result in low amplitudes at below the elbow. But going from that short distance from below to above the elbow, we probably shouldn't have this much of a decrement, so that's, again, telling you that there's some conduction block there. And then the conduction velocity is also slow. I guess I'll use my time for questions here, just to get through some of the rest of these cases. All right. So this is a mild ulnar neuropathy of the elbow with primarily demyelinating physiology. And we can localize that to the retrocondylar groove based on our inching studies. All right. So when we do, so you can do sensory inching studies. I would say use extreme caution, again, they're very technically demanding. And if the snap is already low, then you're not going to want to do these. You do have to average several responses together, I would say five to ten per site, to make sure that you're getting the right onsets. And you're doing just supermaximal, again, because if you're too supermaximal, then that current can spread down the nerve and affect your conduction velocities. And the peak latency difference that you're using here is the same as the motor study. So there's evidence behind this, rarely done, you would only do it in a case of mild ulnar neuropathy. All right. Anyone do this study? It's the median ulnar comparison. It's an orthodromic study. You stimulate at the wrist and record. So you're up at the forearm there, the median ulnar nerves run pretty close to each other. So you can stimulate those sensory potentials using the same electrodes. You don't have to move them. But you're stimulating at the wrist and then also at the median at the wrist and the ulnar. And you're recording these orthodromic potentials. This, what we're looking for is a prolongation of the ulnar sensory response, or the ulnar mixed nerve response, compared to the median. And different cutoff values have been proposed. And again, this is a little bit unusual. We're using it with the arm extended rather than flexed, because that's how the reference values were developed. And I use a latency difference of less than 0.9 is normal, and then 0.9 to 1.1 is borderline, and anything above 1.1 is abnormal. So that's another tool they use. All right. I think this will be the last case here. So 55-year-old diabetic male with two years of progressive left-hand weakness and atrophy, constant numbness in the ring and small finger, funny bone feeling, and some neck pain. So again, starting with the ulnar ADM, and this is what we get. Remember, he's diabetic, which complicates things, right? So we've got a prolonged latency, could this be at the wrist? We have amplitude that's low. It's not, it doesn't really look like conduction block, so that's not really localizing, and the conduction velocity is not really localizing, is it? It's slow kind of diffusely, and so you see that with diabetic neuropathies. So not really able to localize this at this point. So what's the next thing that you would do? Think about that. What other, clinically, you're thinking this is probably ulnar neuropathy at the elbow, with that funny bone feeling, but this doesn't prove it. You could do the FDI. So you leave the, you stimulate the same places, you just change the electrodes around, different nerve segment. We get kind of the same responses, not really helping us that much. All right, D5, absent. Could this be the diabetic neuropathy, though? At this point, you're not really sure. How about the dorsal ulnar cutaneous? So that can have localizing value. If it's abnormal, that would tell you it's above the wrist, at least. Absent. Again, not sure if it's diabetic neuropathy. So in this case, you can do the other side, and that's intact. Okay, so it's, it can have a response, so now I'm not attributing these absent responses to a diabetic neuropathy. You could also do the median or radial. And so this is abnormal, and presumably it's the same thing that's causing the ulnar slowing. So this puts it above the wrist, right? So we're not thinking wrist anymore, because this is abnormal. Important to always check the MAC when you have absent ulnar responses, because you don't know if it's a brachial plexopathy. And so it's important to do this one. His was intact. Median motor, again, a little bit prolonged. I'm out of time, so I'm going to wrap up here. Again, do the median digit 2 sensory, and we see diffuse slowing. This is another use of that test. And so this is a non-localizable ulnar neuropathy at or above the dorsal ulnar cutaneous branch with sensory and motor axon loss. I'm going to skip through here, in case this is a radiculopathy, just showing that it's important to establish that you have intact sensory responses in the location of the paresthesias. I apologize for going too slow on this, but I wanted to get to the conclusion here. There we go. You can have lots of options. And so in summary, avoid the test everything strategy. You can really, you notice that I didn't do the same set of studies on any of these patients, or in the same order. So you want to select your test based on symptoms and location. And remember that two abnormal tests are better than one. And the last thing I just want to mention is that we really do want your feedback on these presentations. We want to know what you're thinking, how we can do better. So if you, after the talk, get out your phone and scroll down, select this talk, go down to the bottom, and there's a link that says share your feedback, and just a couple questions. Give us some feedback. We'd really appreciate that. Thank you. Thank you, Dan. Our final speaker is Dr. Daniel Pierce from Omaha, Nebraska, a physiatrist. And again, we'll try to allow a few minutes for questions at the end. Okay. Perfect. Thank you, Dr. Brunner. And so I know you already gave a little bit of, you know, find out about who you are, but I also wanted to find out about, you know, kind of your experience. You know, some of the people that I've known that have gone to these technologist-centered sessions have had kind of a wide range of experience. So how many of you, it doesn't matter whether you're a technologist, resident, a trainee, how many have done less than 100 studies so far? Okay. So a couple. How many, I would say, between 100 and 1,000? So getting well on your way. Okay. And then who over 1,000? Perfect. So I'll be the first one to say, you know, there are probably many of you in this room that have done more than I have. So really what I wanted to do today was, you know, give some more information on, you know, how I work through a study as a physician, kind of the reasoning that I have so that whether you're working with an attending physician or as you're building your own skill set and moving on to being able to kind of plan and kind of put together studies on your own, you'll kind of have that game plan in mind. And as we do so, we'll do it through some more cases. We talked, you know, we did a few cases of upper extremity. We're going to do a few cases of the lower extremity as well and really focus on, you know, some of the basics for maybe some, a few of you that, you know, maybe this is a little bit newer, trying to refresh from earlier. Do I have to put it again in those slides? Could we get it to the slides? To the actual. I don't want you all to find out all my secrets before they come up, you know? And so I'll be honest, we were able to listen to Jim earlier, and he has such a great presence about him, and I'll do my best to keep up that same energy. I can't promise anything. Hopefully, I have a few pictures in here to keep you interested, though. Nothing to disclose financially. Okay, so the whole title of this was The Good, the Bad, and the Ugly, and Jim gave us a bunch of great examples of, you know, the good, but then also a lot of the bad and the ugly, some of the things that we're trying to avoid, some of the pitfalls, some of the things that, you know, honestly, we do every single day, but we're able to recognize them, go back and fix them, and, you know, have a good study in the end, and, you know, we were able to hear, you know, about some of the upper extremity studies as well, and I'm going to talk about, you know, kind of the good of some of the lower extremity stuff. But I was thinking, I was like, okay, so the good, the bad, and the ugly, the ugly is the fun part, right? You know, good, maybe, you know, you always learn about good every single day, but I thought, okay, well, you know, it's Halloween, and so maybe instead of the good, the bad, and the ugly, I can try and do the scary as well, and so I don't see anybody dressed up for Halloween today, so this is, so I, a picture of my family, I have a new child, so he's about four weeks old, and so we went as Beanie Babies, and then, of course, our dog as well, so today I'm doing the good, the bad, the ugly, and the scary, hopefully we'll stay away from the scary as much as we can, with the, kind of using the lower extremity studies as the backdrop for that. So like I said, the good, so when we're doing kind of the entire electrodiagnostic evaluation, of course today we're going to be focusing on the nerve conduction portion of the test, but that's just one small piece, and so the things that we'll talk about today, they really do fall within kind of the entire framework of the entire study overall, and so we can't talk about nerve conduction studies without talking about the rest of the steps of the process as well. So like I said, for today we're talking about nerve conduction, so we'll go a little bit in the pre-NCS, so most of our time in the NCS, and then talk a little bit about the importance in the post-NCS, and why it helps guide some of the decisions that we do. So pre-NCS, so this is actually the AANEM physician statement who's qualified to practice electrodiagnostic medicine, and the only reason that I bring this up is I think some of the wording in it helps us really kind of go to what Dr. Simmons was saying earlier, and what I'm going to go into in a little bit about how we choose which nerve conduction studies we do as we're designing our studies. And so like I said, I'm not just going to sit here and read this to you, but the thing that I want to pull from here is kind of the second thing, where it says NCSs should be reviewed in real time as they are obtained, and the patient should remain in the examination room until the supervising physician has reviewed the NCS results, and it kind of goes on from there. And according to kind of Medicare guidelines, they have a difference between kind of general supervision or direct supervision, but AANEM recommends that there's direct supervision, meaning that the attending physician is there on-site and can review anything, and I think the real reason is because, just as Dr. Simmons said earlier, we don't want to just go in and do the exact same studies on every single person. And so you really have to have that kind of ongoing thought process of, you know, what have I seen so far, what are my differentials, update, and choose which study is going to do next. So like I said, so the goal of this kind of pre-NCS, like I said, we were talking with the referral, the chief complaint, the history, and everything, is to determine your pretest probability for your top differentials. And so a lot of things go into that. It goes on the population prevalence, and this isn't just like, oh, what's the prevalence of a given pathology across the United States? It's really for your specific referral population in your specific area and the people that you typically get referred for. The clinical history, of course, and the results of your physical examination maneuvers. All of that go into this pretest probability. Once again, you know, we already talked a little bit about false positive and everything. We won't go into that in detail. But just know that when you determine your kind of positive predictive value, negative predictive value, you want to keep that concept in mind as you're designing your test. Like what Dr. Simmons was saying earlier, somebody comes in with symptoms very similar to carpal tunnel syndrome in your first test is normal. Maybe your median motor is normal, maybe your median sensory is normal. You know, your post-test probability, your pretest probability was so high that even with these normal studies, you're still kind of assuming that they have carpal tunnel. And that's why you're like, okay, well, now I'm going to go to even more sensitive tests because my post-test probability was still very high. And so that's kind of why this kind of stepwise approach doing these studies. Like I said, once again, bilateral ham numbness. So, you know, clinic one, so like I said, it depends on the population prevalence for who you get referrals from. So you know, I've had clinics in the past where, you know, it's like we get the vast majority of our referrals from like one specific group of hand surgeons. And so they, of course, are sending a very narrow group of patients to us versus, you know, a clinic two where it's, you know, you're working in, right now I work in the VA. And so maybe the group of the population who's referred to our clinic is maybe a little bit different. And that goes into our pretest probability based on the population prevalence. Okay. So the nerve conduction studies. So like I said, we did the pre-NCS, now there's kind of the nerve conduction part of the test. And so you have your top list of differentials. Now you need to use NCS to start to rule in and rule out from that list. And we, like we all know, we're talking about nerve conduction studies today, and they go hand in hand with the needle EMG. So I'm not going to sit here and say that after you finish the nerve conduction studies, you know, you're going to be done, but we're going to do as best we can to rule in or rule out as many things from our differential list by choosing appropriate studies to do so. These are some of the common studies that we'll do. We're not going to, of course, talk about all of them today. But as part of your inner study, you're going to choose which ones you do. And this is a good list to pull from. Okay. So, and it all goes into kind of this Bayesian reasoning. Pretty much you start with an outlook of the world, and nothing is absolute right. There's always some probability of yes, some probability of no. And that's true when we make our diagnoses as physicians, as clinicians. There's a certain probability that our outlook is correct or our hypothesis is correct. And then we have new data that comes to us, whether it's the new studies, new tests, anything like that. And that will update kind of our outlook or our probability of what's going on. And so, you know, going back to, you know, kind of things that we do in real life, you know, as I was flying in yesterday, it was at the same time as the Arizona Diamondbacks game. So I apologize if any of you are from Phoenix, and I'm bringing up some, you know, kind of some sad things. But sometimes when you're going and you're watching these sports games, they talk about, oh, what's the probability that each of these teams are going to win? And so this is just the, I pulled the game up from yesterday, the win probability of Texas and Arizona. Again, sorry if there are any Diamondbacks here. But of course, you know, Texas jumped to an early lead. And then as you can see here from the win probability, it remained at pretty much 100% all the way till the very end. Didn't matter what Arizona was going to do. Our pre-test probability of Texas winning was so high because they had that early lead. It wasn't even at the end of the game where Arizona kind of jumped back, you know, had all these things. You know, it's not really going to change our post-test probability. Once again, just another example based on kind of this, the reason I chose this is because there was a big play at the end of the game that really changed this pre-test and post-test probability. But we do these exact same things when we're doing our nerve conduction studies. Just because one specific nerve conduction study gives you a specific result, you can't necessarily hang your entire study on that. It all goes into, like I said, your pre-test probability going into that study as well. So like I said, it looked like there were a couple of people that they said, you know, really early on. So this is just a picture from President Shapiro of doing your peroneal motor study to EDB, one of the most common studies that we do. I'm not going to talk about the ins and outs of how to do this test. Easier to kind of practice than talk about it up here in a lecture. Peroneal motor to TA. This is another really good one that can help to narrow our differentials based on what's going on at each different segment of this peroneal nerve. And I'm sorry, Jim, for using peroneal. You said we're not supposed to, but we'll bear with it today. Once again, the tibial motor study, the sural sensory, we do a couple of sensory studies, superficial peroneal sensory, and H-reflex. So like I said, just because it looks like most of you are very experienced, we're not going to go into the ins and outs of doing each of these tests, but these are some of the common ones that we have in our bag when we're doing kind of a lower extremity nerve conduction study or EDX. Okay, so we do the actual studies themselves, and Jim talked to us about some of the things we need to do, focus on the basics, clean everything off. And then what we're left with are our sensory nerve action potentials and our compound motor action potentials. And we want them to look great. And so when we come up, once again, in a stepwise approach, we're going to make sure that do we have a good baseline? Do we have good wave form? Does the morphology look good? And then after we're satisfied with all that, then we're going to go through and we're going to kind of make sure our markers are in the right place. And then after we're done with all that, then we're going to actually look to the results ourselves, look at the results themselves. Once again, just focusing on the basics every single time. And then kind of going on this, and so I said this is kind of the post-NCS or the interpretation, but this should really be going on as you're doing each of these tests. One, because it will help guide you as to determine which tests you're going to be doing, but also it makes it much more interesting. I think one of the reasons I like doing these tests is because, you know, it's kind of like a logic puzzle. It's like, oh, well, you know, if this is positive, this is high and this is low, and so you should really be kind of doing the interpretation as you're going. From Wilburn's article in 2002, these are just some of the steps that he suggested. He said, number one, first start assessing the distal amplitude. Then he said kind of looking at both the distal response duration, secondly, and then thirdly, the distal onset slash peak latency. So of course, first the distal amplitude is to start to think if there's an axonal lesion and then in the next two, see if there's any demyelinating injuries. And then lastly, he said if a proximal stimulation site is also used, assess the nerve conduction velocity between those two points. Once again, determine if there's any, you know, either focal or kind of segmental demyelination. And the interpretation, you know, lots of labs use different values, their normal values. This is just from the AENEM normal reference values. These are the lower extremity ones for motor. Again, these are for some kind of comparisons throughout the nerve and then the sensory nerves as well. But you know, once again, although these are the kind of the standardized normal values, make sure that you're doing what is accepted within your lab and just doing the same thing every single time. It's the most important thing. Once again, going to the interpretation, this is, I think, one of the things that, you know, nerve conduction does such a great job of helping us to determine the difference between an axonal and demyelinating lesion. And so once again, this is from Dr. Wilbourn's article talking about the difference between an axonal pattern, demyelinating pattern. I'm not going to jump into the entire explanation of it, but as you're going through doing these studies, these are some things that you can pick up and you don't have to wait till the attending physician to come in and do the needle EMG to already start to recognize a lot of these things that really do have very important diagnostic implications. And then, you know, at the end, we're going to put the report together. I'm not sure how much you all do in terms of the report generation. Once again, this is just from AENEM. So they put out some guidelines several times on to what the report should look like. And this is just a sample report that they have specifically for the nerve conduction portion of the test. You know, some of the things, you know, have it be in table format so it's much easier to read. You should have your reference normal values listed as well, and you should highlight any areas that are abnormal. Just that whoever comes and looks at the report later on will be able to see that as well. Okay, now jumping on to the actual case studies portion. So case one. So we're here in Phoenix. So you come to work here in Phoenix day one, and your first patient in the morning is a 43-year-old female with a four-month history of right foot drop. And so even, you know, before you see the patient for the first time, you see kind of that chief complaint. Oftentimes, you get it on the paper before you get in the room. You should already start to think about some of the primary differentials, and like I said, that goes back into what's your population prevalence, what's, you know, what's most common. And so you can start to think, oh, what should I ask them, what should I do to examine on the examination, and then what should I do in terms of nerve conduction, and then also later on in the needle EMG as well. So you should already start to be thinking about these things. And this specific patient, so when they came in, in addition to having the right foot drop, the foot drop was subacute onset without trauma, mild numbness to the right foot, hasn't had any falls recently, examination weak right ankle dorsiflexion and right ankle aversion. And so from that, like I said, you can kind of narrow your list of differentials. So using your history and your physical examination to kind of narrow or kind of move around some of that differential list that you had even before you saw the patient. And this goes into choosing which nerve conduction studies to do. And so choose the studies that are going to help rule in and rule out your top differentials. I think most of you are already probably having a good list in your mind at this point. So for this patient, like I said, so once again, I'm, you know, these are just highlighted. They're not supposed to be difficult. They're not supposed to, you know, trip you up or anything. But the main things that we see is, you know, somebody comes in with foot trouble, of course, we're going to want to start with the affected side and do their peroneal motor studies, doing both EDB and especially TA as well, because that's the muscle that's implicated in the foot drop. And so as you can see here, with the peroneal motor nerve, there's a little bit of a drop in amplitude across the knee and some slowed nerve conduction velocity across the knee as well for both that EDB and TA. So then you're thinking, well, so there are some kind of abnormal things, and that kind of strengthens my pretest prediction. But I still want to kind of, you know, make sure that that's true. And so I'll want to have some, like, reference studies to compare it to. And so what you can do is you can do an in-limb reference, so doing another nerve within that same limb. Here it's the right tibial motor, which looks pretty good. So now you're thinking, okay, so I can start to rule out some of these other differentials that are more global in nature, because I have this kind of internal limb control that looks good. You can also use a contralateral control, being kind of the same nerves that were abnormal on the right side. Do them on the left side, and they look pretty good here as well. That helps you kind of narrow that list of differentials, strengthens your post-test probability. Again, we'll go from that, we'll do sensory nerves, looking at the absence of the right superficial peroneal or fibular sensory nerve. And once again, I think still adds to your strength in your hypothesis and post-test probability of what's going on. Going through to the report, so like I said, going through the report, so there's a drop in CMAP. We already talked about that. So this is just kind of going on the findings that we had. And then the right peroneal motor NCS was not obtainable. And then now, like I said, we're not done. We will go on to the needle portion of the test, because that will give us more information. But now we really have a really strong top differential in our mind, and it's because of what we were able to do with the nerve conduction studies. Okay, case two. You finished that test, you did a great job. Another 43-year-old female with a four-month history of right foot drop kind of takes you back a little bit. But then when you go in and you see her, her history is a little bit different. This was a little bit more gradual onset, just bilateral foot numbness. On examination, there's some decrease in sensation and proprioception in bilateral feet, as well as some steppage gait. Once again, based on her history in physical examination, your list of differentials is probably maybe a little bit different. It's going to be very similar, but maybe a little bit different in terms of your top one or two. And then you're going to go on to the nerve conduction portion of the test. Once again, here, we see a pretty small amplitude in the right peroneal motor nerve, although the TA does look to be at least a little bit better. So you do your internal limb conduction. If you go to the contralateral side, it also is a little bit low. And then you couldn't get anything for the sensory studies. So then what you want to do, because you weren't able to find a good kind of control in the lower extremity, you go up to the upper extremity, and the right radial sensory nerve looks pretty good. So that's kind of the issue with planning the entire thing before you go in. Somebody comes in with kind of a lower extremity complaint, you don't necessarily want to be doing an upper extremity study on every single one of those, because a lot of times it would be superfluous. But because it really aligned with what we were finding in our study, and kind of going on with our top list of differentials, it was the appropriate thing to do. It's just reiterating what we saw in the report, and we'd move forward with the needle portion of the test. Then your third patient of the day, now you're really confused. You realize that there's an endemic going on of 43-year-olds with right foot drop. But you see this patient as well. This patient, however, has a history of severe back pain. Positive straight leg test. And once again. So, once again, you start with the peroneal motor nerve, both EDB and TA, because that's where our primary complaints are. Don't see too much there. Sensory study also looks pretty good. Then we realized that, oh, based on our differential, we're thinking that maybe this could be a radiculopathy. And so we decided that we were going to add in RH reflex. And honestly, don't see too much there. Then like the report, honestly, for this specific person, all the nerve conduction studies look to be pretty good for age and sex. And so we move forward with the needle EMG portion of the test, kind of trying to see if a radiculopathy is the issue. Okay, so pretty much in summary, the reason that I did this is, like I said, one, to kind of think about some of these lower extremity studies based on maybe the top differentials that we might get, but also kind of understand the thought process that goes into doing all these things. And it's not always necessarily like a step-wise approach that you take every single time. It all goes back to, what's my pretest probability based on what I know beforehand? The study that I'm choosing now, is that going to strengthen or weaken my differential? Can it rule something in? Can it rule something out? And then based on the results of that test, is it going to change my post-test probability as well? And if it's not really, if it's not kind of going to help you rule in or rule out anything else, then I'd say move on.

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