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Nerves Anatomy and Electrophysiology for Orthopaedic Exams
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Nerves Anatomy and Electrophysiology for Orthopaedic Exams
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Language: EN.
Segment:0 .
OK good evening, everyone. Welcome to the fastest teaching this Wednesday, September. You have, David today. David Hughes, who is presenting is being very brave actually to take on this very difficult topic of talking about the nerves. And that, to me, basic sciences and neurophysiology, and we appreciate that very good of him.
We have also with us, sichuan, as always, supporting and helping with running the session. And today, also, we have one of the senior mentors who has always been with us even, you know, he's not appeared on these webinars before, but he is always with us supporting us and advising and helping us set up everything. So he's behind the scene working for Hahn or Hahn said it was working in Coventry now, so it will come from.
He will have some hot seat waiver questions also, which will be very interesting. So just some housekeeping issues. If anyone wants to talk or have a question, you could write it in the chat box or raise your hand symbol next to your name. If you also would like to take part in the Viva, it's on first come, first served basis, again, there will be limited number of questions.
So please, if you're interested in taking part in Viva, we encourage you to make best use of this opportunity and please raise your hand simple. So I know you and put your name down. So I will leave it to you now, David. Go ahead. Thank you. We talk about nerves and neurology for the Sharks.
So I got to do a review of the anatomy a bit about nerve injury. I'm afraid I had a bit of an issue with my presentation. So the slides about repair are sort of missing, I'm afraid. And then I've got a bit more about neurophysiology, so we'll talk a bit about nerve conduction studies in particular, sort of to get you aware of that because I had a couple of questions on the exam myself with this, and it's not the best time to find out about it in the exam.
So it's a good way to warm up for you guys. OK, so. Obviously, in terms of the nervous system, it into a functional way, you've got your sensory and your motor. And we understand those, these are sort of basic principles, really. These are few things you might get thrown at New terms of somatic and autonomic sort of voluntary and involuntary and obviously again, visceral sort of receiving information.
OK, now this is a pet of a lot of examiners. They might ask you to draw a nerve and everyone starts drawing an accent. This is what they mean by a nerve. But they want you to talk about the different structures of nerve. So the epimysium, the engineering, the bundle, the bundles, connective tissue, the blood vessels. So if they ask to draw nerve, they start drawing a spindly thing with dendrites.
You're going down the wrong route. They might give you a subtle hint, you know, a nerve rather than an axle. OK that's the key thing. And remember the components of nerve. Arevery your motor and your sensory. All right. So it's almost like I always think of it as a fiber optic cable with lots of little bundles within.
OK, and here's a bit more detail with regards to nerve. So they may start saying the individual bits is good to have that ready, and that is a very easy start to question on this basic science table. These are your nerve. Ok? and we ask you about an accent, so again, this is again. Some candidates will end up drawing an accent when they say in.
But this is what they're quite, quite specific. So in particular, they might want to ask you some questions with regards to those around VA and in terms of conduction velocity around that. We will talk about it a bit later. Now, a term that often comes up in a neurophysiology is often ironic, and that means the correct direction. So this is a sensory nerve. So I get my arrow, the sense.
So the signal is going that direction. OK right. Most of the signals going that direction. And likewise, again, if I show you on the sensory nerve. OK, so getting that direction right? Then we talk about anti-drone. That's going the opposite direction. So this will come more apparent when we're talking about nerve conduction studies and imgs.
We tend to do more commonly antiarrhythmic nerve conduction studies when we're testing to see the. Right and again, the key thing is you types of axons, you've got your myelinated axons and your unmediated axons. And so it's all about with regard to the skipping the real speed of electrical nerve conduction. OK and again, I think you've seen this in ramachandran, you've seen all these pictures of the different types of groups.
If you understand there's a different there are different groups. They'll get quite forward at this stage. But don't worry, don't go too much into too much detail about this. The more interested with regards to nerve injury. So we want your classic is a certain classification. You're apraxia axilo nemesis and newer tenodesis. OK so a peripheral nerve injury, so that's what we're classically to see.
Maybe a new apraxia. Generally, it's a non degenerative lesion of a nerve characterized by complete or partial failure to propagate an action potential, a conduction defect long nerve resulting in a motor or sensory loss. So your carpal tunnel, your cubicle tunnels. Your crush injuries. And again, these are the classic things they're are usually caused by compression is skiing, it can be reversed if the interest agent is removed, so tourniquet time is very important.
Love remains intact, and key thing is there in two generations should not occur. OK again, usually the stimulation of the distal segment will evoke a response, the motor action potential expected is going to come back by day 10. Recovers by re-imagination of the distal segment can actually take a 2 to 2 to 12 weeks to recover. So it does take time.
Um, the assumption that the lesions in your practice practice rather more severe can sometimes lead to delay. I mean, these are things that need to be aware of going down this route. You're doing quite well. Potential diagnosis to make in a particularly if there's persistent pain, which would suggest that there's still a lot to conduction. Um, the diagnosis should not be made in the presence of a strong toenails test, which indicates the accents have been ruptured.
So these are things that they get you. Good points in terms of if they are push you further on a new apraxia. OK, now an accent. To me, this is a disruption of the accent and it's Mylan chief and the supporting structures are Schwann cells. The engineering perineum and the epimysium remain intact. OK this is the accent and smile smiling chief that's damaged, ok?
And it's usually again the result of severe compression or crush injury. Were there in degeneration occurs distally and proximate to the closest to the runway. Repair is by a combination of collateral sprouting of lesser injuries and axilo regeneration in more severe injuries. The latter occurs very, very slowly at 1 to 2 millimeters a day. This is the question they may ask when you get a nerve conduction report.
This is external damage. They want to know about Wallerian degeneration. They want to know that is going to take a long, long time. The nerve to recover. OK but again, as I say, nerve conduction studies will show a loss of conduction in the distal segment quite quickly. Three to four days after the injury, small or absent potential compound muscles may show some action.
Potential EMG studies will show potential sharp and sharp waves at a 2 to three week, which talks about accidental loss. So these are things they might talk about in the vyver degree of recovery depends on the age of the patient with any nerve injury. The younger the patient, the better the chance of recovery and also the amount of fibrosis that has occurred at the time. OK right near tenodesis is a complete destruction of the peripheral nerve by any means.
So that's your. An amateur surgeon cutting a median nerve doing a carpal tunnel. Simple but very rare, it might be a laceration deep penetration injury. And this case is a generational distal to the lesion reduction studies show a loss reduction at three to four days.
Emg studies show fibrillation again two to three weeks. The only sort of surgical intervention is to repair the nerve, or whether by direct suturing or grafting at the time of the injury. Or we've got 3, 2 five day window, to be honest. And then the next option would be to consider. Um, whether you need to do a grant, I'm not a plastic surgeon, I'm not going to talk about that today because I get confused.
But if you again, this is something you talk about in the exam with regards to having a multi team disciplinary approach to get help and get there. OK, so there's just this all talking about where the seven classification comes in. So we've got on your apraxia. Which the old Sunderland was called type 1. That is all that conduction block. Then you axilo on Mrs. Can be subdivided into two, 3 and four.
So you've got your accidental discontinuity, which is type 2. So accidental discontinuity and in engineering disruption is a type free area of her unusual disruption and physical disruption is a typo. And there are two Mrs. Everything's discontinued. OK and this signifies were there any degeneration. So you can see well there in degeneration and degeneration in all of those. But that's just meant to say axons.
The axon is intact. All right so that's the key thing when you're talking about these. Look, and just another sort of demonstration of how the action works, though, in terms of you've got your disruption there, compression your sheath, your sheaf is lost. That's what we do about your loss, the disconnection and you can see this is a clarion degeneration occurring here.
Ok? again, we talked a bit about axonal regeneration that can happen with severe disruption. And you can see you've got your degeneration here, lost their cut there. Everything's been broken down distally and occasionally you can get a bit of their axilo regeneration with adjacent nerves, and that can take a very slow process, which tends to happen with people.
OK now, one of my exams I did, I was given a nerve conduction study to talk about that was in the basic science thing, so it is something that will come up. It's worth when you're in your hand clinic or when you're looking at her or talking to a patient, or if you've got carpal tunnel on your left, looking at the nerve conduction studies just to familiarize yourself with it so you can know what you might get thrown at you.
Ok? typically, it's they may say, why do we do it plays a key role in the evaluation of patients with neuromuscular disorders and also peripheral nerve injuries, and also can help. Importantly, in people with brachial plexus injuries, it can or any other sort of severe injury. You can look to see if there's any changes or improvements, and there are some key things we're worried about wave and reflexes.
OK so nerve conduction and imgs are different from the core or the core of electro diagnosis. These studies are performed usually performed first and usually yield the greatest sort of diagnostic value if the forms are interpreted correctly. They can help us really work out what things are, but they are not all the be all and end all. We still have to think of our clinical scenarios. That's the key thing if the marriage of both of those.
I do somewhat controversial at the moment with the whole sort of nice and NHS England talking about. We don't want to do carpal tunnels anymore, but they still need to be done because in terms of preventative, whatever generation ulnar nerve, they are important for patients and we're going to be using these a lot more and/or to justify doing these. OK, so there really be this one.
OK, so nerve conduction velocity is electoral diagnostic test provides information about abnormal conditions. The nerves are stimulated with a small electrical impulses by one electrode or another. Electrode detects the electrical impulse downstream from the first electrode. This can even be autonomic or at hydraulic, so reverse or straightforward. OK so again, on the basic science table, we may ask you to draw a Allen nerve conduction velocity or ulnar nerve nerve way.
The key thing is 0 is here, and I've been a bit naughty. They do that. Quite a few textbooks do that, so it's important that you remember. If you see something like this, it is. That's not zero. 0 is up here. So we're starting the resting potential of minus 70. I hope we all know this.
And you've got your stimulus applied. Eventually gets to 55 is the threshold, which creates the huge voltage rises to go to plus 30. This is merely volts, not four volts, thank goodness. And then voltage slap flows. And then you have your repolarization. They might ask, why do you have repolarization? But we understand that this is a question I think we'll ask in the vyver because I want someone to talk about it.
And then you return to your resting potential. I haven't got it on here, but they may also want you to talk about sodium and potassium levels in terms of what's happening here. But so that's something you need to think about as well. That could be the second could ask you to draw this and then ask you to talk about the sodium and potassium. Right, OK, so we need to know a few things with nerve conduction studies, the distance from the electrodes and the time taken for impulses to pass, and that helps us in terms of working out the speed transmission slower than normal, but indicate damage from direct trauma, stimulation of diabetic or peripheral neuropathy or nerve.
So the key thing is we're worried, more worried about carpal tunnel. OK so an EMG is basically the same thing, but looking at the motor response. And it's looking at what's produced by muscles. A lot of the time we do get both of those. And it's quite easy to get confused. And it's about the tiny amounts generated by the muscle cells when they're activated by the nerves acting within.
So there's several types intramuscular and surface emg, which one we use as most common is the intramuscular one involves inserting a small needle into the skin. Sometimes you can see the surface ones when we look at them in the clinic, I don't know. We used to have them, but they're not very accurate. And that hopefully detects a muscle impulse as well.
That's right. I was not surprised we back to where I'm supposed to be. OK, so here we go. Our apologies about that. So here we have an A Century one of median nerve. This is typically at antiarrhythmic, right?
Yeah, so we've got our little sensory parts here passing signal there we're looking at the wrist, at the elbow. Axilo OK. Signal is going this way. That's why it's anti-drone and we're looking at the responses there. So you can see. As we go further back gets less because hopefully the signal is being dissipated a bit more.
OK this is not atomic, as I said, and this is often ironic at this time. We've got our sensors here, we're sending it along here. This is a distance and we're measuring them in the wrong way around politics. Been, it's been stimulations. It's been this way. We're measuring it this way. Ok? this is all for dramatic sensory because this is the way the signal is going right?
Motor conduction, this sort of I get confused with it, I apologize about it. That's why. So this is going to be often drunk again. But the signal is going at direction. Because that's the way because the muscles are distraught, and so we're looking at that response again. But you can see high response there, less and less as we go further away.
Right? so this is an example of a sensory one that you might see. OK and this is the usual spots where they may put it for the carpal tunnel. A reference point active on the ground. That's usually what they have. On a couple of these, they're very confusing. And as I say, I didn't.
It looks really good when it works, but it doesn't work very often. I think if Iran remembers what we did then at work a few times like. OK so looking at the risk, we're looking at a nerve conduction velocity, this is. More stimulus going along this route. The elbow.
We might show a little spike there. That's that's the stimulus. You're resting potential going, creating the officials, causing a response. And that is our latency period. OK now, these are key terms that they're going to ask you in there, but they won't ask what latency? Latency measures the time between the stimulus and the response in milliseconds.
This is sort of basically the talking about your speed. OK so the one that's going to be our distance, I think, isn't it correctly? Yeah right. So that's our next one. This is just so the formulas you may work out, they have different things, but the key thing is remembering latency is measuring the time between the onset of the stimulus, the time the stimulus response.
OK OK, so this is a classic one of the median nerve. These are very complicated. I wouldn't worry too much about them. Now, some of the ones you may have. So we're looking peripheral nervous systems, so we're going to have an even a motor nerve conduction, a sea map, which is the stimulation of peripheral nerve while recording a muscle that innervated by that nerve. I've never got a snap, which is a sensory nerve conduction.
And that is a stimulation of a mixed nerve when recording for a mixed or continuous flow. Basically, your ulnar nerve or your median nerve? These are the terminology that they want you to spout out at the time, so latency is the interval between the onset of stimulus and the onset of response and amplitude is the maximum voltage difference between the two points is proportional to the number and size of fibers are being vaporized.
It basically equates to how good the quality of the response is. It tells you how good that nerve is. It could have. It could have a good response, as in a good latency. But if it's got a small amplitude, it could be still being crushed. Duration again, the time frame onset determination total duration is talks about the dispersion of all components, and it measured the difference in production nerve fibers.
I mean, you've got your overall conduction velocity, which we're talking about, the speed at which the nerve fibers are carrying electrical stimulus between the two sides. Comparison of conduction between two segments that can help us localize the lesion, which is why we look at the wrist, the elbow and the axilo. So if we got a normal speed at the axilo and the elbow and the reduced speed of the wrist to be in the median nerve, but we know it's carpal tunnel rather than something at the elbow or the slap.
OK so are typically our type of. Ones are going to be one for the sensory ones because we're looking at. So stimulates nerve and classically Yuzuru. And these are the usual ones we do meet in their. And typically, we're looking for people, agencies, conduction velocities. And that the amplitude in those situations.
And that tells us, as I say, those are the key things for how quickly they're being the stimulus cause that causes response and how much of a response is generated. Those are the key things. So speed and quality. Most conduction studies, these are very much in terms of telling us if there's any external degeneration, so demyelination, so damage to the axon.
Typically, they're gone for proximal to distal, evaluate for construction velocity looking at block so that again, ulnar medial nerves, the ones, the other ones that we can do, but they're not. That's really above and beyond for this exam. Now, these are ones they may ask, what type of wave is this or reflex, and if waves and waves are rare, they're useful for helping intensify demyelination and when there's more.
And usually on the motor EMG if there's amplitude or greater than 1 mile a boat. Look, I depend on the patients, right? So what is it that way? We're looking at that sort of response to the door for both horn doppelganger against the heat reflex. OK so they look at proximal roots and the antigen motor response, the anterior horn, the spinal cord, often dramatically to the muscle.
It's a pure motor test. A prolonged asymmetrical wave is suggested of a proximal root lesion, and its chemical is established in terms of we're talking about prolonged in violation of external injuries. Less sensitive than EMG for ridicule, since we're only looking at short segment there. OK so that's what they might show you. That's your see map.
I talked about earlier the motor action potential. And that's the wave response. Happens a little bit further along that feedback loop was happening in that picture. Thanks says that feedback loop. OK but as I say, it's just it's just the pure motor test. It helps us identify demyelination. OK these are some abnormal waves.
It's not coming in, says it should do, but you'll be very lucky if they show you that. Again, reflex reflex to offer drama. So going in the direction of a flow of entry and motor boat motor and sensory is very good for philosophy and median nerve rest. By recording a copy, radio is apparently typically a unilateral delay absent will suggest a problem. What's abnormal may not normalize that wherever it isn't in people with lots of volume rock.
So anyone over 60 or someone who's diabetic? Right, so that is your wave. That's the reflex later on. So these are just some of the techniques they might talk about being. Lacked a needle being said to the muscle, disposable single use and typically multiple muscles accessible examination.
If you. I don't know if you're a teaching hospital, if you can't go and have a look at the nerve conduction study. And just so you know what you send your patients to. OK and it's basically looking at activity and social activities. There's activity, motor unit configuration and experience that I don't think we'll ask you too much about that. But just to show you. This is what you might.
These are some of the things you might get. Be honest, this again, if you're getting to this point in the video, you're doing quite well. I'll move, move on. What they want for this for that. OK this is one thing I was going to ask about. They may also like it, may this is another thing they may talk about in the emails you took to draw a neuromuscular junction.
But that's another topic for another day. But we may talk about that in the liver because there's not very much to talk about in the pilot. The question is why? But this is a key thing as well. OK, thank you very much. Oh, brilliant. David, thank you very much. I just to refer, I think Sean has given a nice.
Look, when we first started this webinar teaching about the neuromuscular junction and how the complex process works and its own YouTube channel and has promised that was very great of you. David, we know you are not a neurophysiologist, but I think you've reached that level. So if you had electro engineering, then. But actually, it does pop in the exam a lot. Yeah, and it's one of those.
Suddenly, the examiner suddenly seemed to know everything about electrophysiology for some reason. They do have the answers in front of them. Yeah, but remember that it's unfortunately something you have to memorize. It is useful for clinical practice, particularly if you're going into an upper lip job or also. The problem is with this type of topic is you don't use it in your everyday practice.
It's only when you've got a nerve conduction study and you're in a busy clinic, you want to. You just want to read the report of your colleagues and say that, OK, we're going ahead with the median nerve compression. David is correct. Please take the opportunity to actually study what a nerve conduction study looks like, because you will be given a sheet of paper with sometimes just the waves drawn on and they'll say, what?
What is this and what is that? And sometimes they'll give you the numbers and so on and you'll say, what can you interpret this without any of the interpretations from your neuro physiologists? So do take the opportunity to do that. Second, it's worth going over this topic a couple of times. Watch David's video when it goes up on YouTube the second time, so it's a bit more solid.
Get the definitions down correctly. It's a brilliant presentation. Well done, David. I think that I agree this presentation contains everything you need to know. You just have to listen to it again and again for three or four times to record everything because a lot of information there and you need to.
But I think you got everything you need there that all the terminology to use that, you know, the buzzwords, the differences of between nerve conduction and imgs, the waves, the different waves they do. Ask all these questions. Unfortunately, you might be surprised, guys, but unfortunately they do ask them very frequently, even in part two of the why? When so and yes, they are asked to draw a nerve.
So you could start practicing from now, how to draw a cross-section of the nerve. It is very simple, but you could answer that easily if you have practice, but you have to practice in advance. Any comments from you for harm about? But for me, it is one of those topics that I would put it down as to be device. For example, you won't be able to device the whole thing, but individually, if you are making notes, make sure you write down what are the 10 15 topics that you want to revise before exam and on me personally, this is one of those topics.
Yeah, I think people might feel a little bit out of depth at this, but but don't go, don't worry, none of us knows much about nerve conduction studies. More than that's what this lecture. And so please, if you have guys any questions, come forward. But we will. We do encourage you to, but we've got to have survivor in a minute. I just want to reassure you if you can start talk, if you can say some of the terminologies, the definitions like latency, aptitude and what they imply by that, you're doing it, you're going to do well in that section.
They're not going to expect you to be a neurophysiologist. If if you look like you lecture, you understood it and you read it a bit out of it, you're going to get a good six seven. Hopefully we're orthopedic surgeons. We're not comfortable in this. This is why I said I put my hand up. I said, I'll do it. Someone has to do it because it is something that was a bugbear that threw me, and I just want to make sure it doesn't throw you when it comes to the exam.
Yeah, I think these days they are encouraged to ask about the clinical implications of everything, so they'll ask you, when would you do nerve conduction studies? And when we do imgs and give an example, for example, for each one when you do it to make it more clinically oriented question. So that could be something to look into.
I don't know if you, David, have, you know, any quick answer to that. Well, the reality is, most of the time you will you'll get a combined, combined nerve. Are you're going to get a median nerve. So you have an EMG and a nerve conduction study. The key thing is, you will, if there is axonal degeneration, so the axon is damaged axon devices, you will see demand, you'll see changes in emg, which is important.
But from a clinical point of view, in terms of recovery for the nerve, that's the key thing. Yes, it's a rule of thumb, you always get a bit of both. You always you rarely a nerve conduction studies only really important in pure radiculopathy. But there's very rare. We ask for those. I mean, we're not.
Neurologists tend to be the guys. Neurosurgeons tend to be the guys who answer those. That's any time you get just a pure nerve conduction study, but most part you get a combined sensory and motor or your combined peripheral nerves, your median nerve and ulnar nerve. I think the one fact that sticks to my memory is with the imgs, as the one used for clinical use of it is in the cases of radial nerve palsy following humeral shaft fractures and seeing fibrillation on the imgs is a sign that the nerve is recovering.
Yeah, so. I think I try to remember something useful about images, and I think that's the one fact, I could remember. That's related. So so that's good. OK, guys, so any more questions to ask, so we'll move on.
Segment:0 .
OK good evening, everyone. Welcome to the fastest teaching this Wednesday, September. You have, David today. David Hughes, who is presenting is being very brave actually to take on this very difficult topic of talking about the nerves. And that, to me, basic sciences and neurophysiology, and we appreciate that very good of him.
We have also with us, sichuan, as always, supporting and helping with running the session. And today, also, we have one of the senior mentors who has always been with us even, you know, he's not appeared on these webinars before, but he is always with us supporting us and advising and helping us set up everything. So he's behind the scene working for Hahn or Hahn said it was working in Coventry now, so it will come from.
He will have some hot seat waiver questions also, which will be very interesting. So just some housekeeping issues. If anyone wants to talk or have a question, you could write it in the chat box or raise your hand symbol next to your name. If you also would like to take part in the Viva, it's on first come, first served basis, again, there will be limited number of questions.
So please, if you're interested in taking part in Viva, we encourage you to make best use of this opportunity and please raise your hand simple. So I know you and put your name down. So I will leave it to you now, David. Go ahead. Thank you. We talk about nerves and neurology for the Sharks.
So I got to do a review of the anatomy a bit about nerve injury. I'm afraid I had a bit of an issue with my presentation. So the slides about repair are sort of missing, I'm afraid. And then I've got a bit more about neurophysiology, so we'll talk a bit about nerve conduction studies in particular, sort of to get you aware of that because I had a couple of questions on the exam myself with this, and it's not the best time to find out about it in the exam.
So it's a good way to warm up for you guys. OK, so. Obviously, in terms of the nervous system, it into a functional way, you've got your sensory and your motor. And we understand those, these are sort of basic principles, really. These are few things you might get thrown at New terms of somatic and autonomic sort of voluntary and involuntary and obviously again, visceral sort of receiving information.
OK, now this is a pet of a lot of examiners. They might ask you to draw a nerve and everyone starts drawing an accent. This is what they mean by a nerve. But they want you to talk about the different structures of nerve. So the epimysium, the engineering, the bundle, the bundles, connective tissue, the blood vessels. So if they ask to draw nerve, they start drawing a spindly thing with dendrites.
You're going down the wrong route. They might give you a subtle hint, you know, a nerve rather than an axle. OK that's the key thing. And remember the components of nerve. Arevery your motor and your sensory. All right. So it's almost like I always think of it as a fiber optic cable with lots of little bundles within.
OK, and here's a bit more detail with regards to nerve. So they may start saying the individual bits is good to have that ready, and that is a very easy start to question on this basic science table. These are your nerve. Ok? and we ask you about an accent, so again, this is again. Some candidates will end up drawing an accent when they say in.
But this is what they're quite, quite specific. So in particular, they might want to ask you some questions with regards to those around VA and in terms of conduction velocity around that. We will talk about it a bit later. Now, a term that often comes up in a neurophysiology is often ironic, and that means the correct direction. So this is a sensory nerve. So I get my arrow, the sense.
So the signal is going that direction. OK right. Most of the signals going that direction. And likewise, again, if I show you on the sensory nerve. OK, so getting that direction right? Then we talk about anti-drone. That's going the opposite direction. So this will come more apparent when we're talking about nerve conduction studies and imgs.
We tend to do more commonly antiarrhythmic nerve conduction studies when we're testing to see the. Right and again, the key thing is you types of axons, you've got your myelinated axons and your unmediated axons. And so it's all about with regard to the skipping the real speed of electrical nerve conduction. OK and again, I think you've seen this in ramachandran, you've seen all these pictures of the different types of groups.
If you understand there's a different there are different groups. They'll get quite forward at this stage. But don't worry, don't go too much into too much detail about this. The more interested with regards to nerve injury. So we want your classic is a certain classification. You're apraxia axilo nemesis and newer tenodesis. OK so a peripheral nerve injury, so that's what we're classically to see.
Maybe a new apraxia. Generally, it's a non degenerative lesion of a nerve characterized by complete or partial failure to propagate an action potential, a conduction defect long nerve resulting in a motor or sensory loss. So your carpal tunnel, your cubicle tunnels. Your crush injuries. And again, these are the classic things they're are usually caused by compression is skiing, it can be reversed if the interest agent is removed, so tourniquet time is very important.
Love remains intact, and key thing is there in two generations should not occur. OK again, usually the stimulation of the distal segment will evoke a response, the motor action potential expected is going to come back by day 10. Recovers by re-imagination of the distal segment can actually take a 2 to 2 to 12 weeks to recover. So it does take time.
Um, the assumption that the lesions in your practice practice rather more severe can sometimes lead to delay. I mean, these are things that need to be aware of going down this route. You're doing quite well. Potential diagnosis to make in a particularly if there's persistent pain, which would suggest that there's still a lot to conduction. Um, the diagnosis should not be made in the presence of a strong toenails test, which indicates the accents have been ruptured.
So these are things that they get you. Good points in terms of if they are push you further on a new apraxia. OK, now an accent. To me, this is a disruption of the accent and it's Mylan chief and the supporting structures are Schwann cells. The engineering perineum and the epimysium remain intact. OK this is the accent and smile smiling chief that's damaged, ok?
And it's usually again the result of severe compression or crush injury. Were there in degeneration occurs distally and proximate to the closest to the runway. Repair is by a combination of collateral sprouting of lesser injuries and axilo regeneration in more severe injuries. The latter occurs very, very slowly at 1 to 2 millimeters a day. This is the question they may ask when you get a nerve conduction report.
This is external damage. They want to know about Wallerian degeneration. They want to know that is going to take a long, long time. The nerve to recover. OK but again, as I say, nerve conduction studies will show a loss of conduction in the distal segment quite quickly. Three to four days after the injury, small or absent potential compound muscles may show some action.
Potential EMG studies will show potential sharp and sharp waves at a 2 to three week, which talks about accidental loss. So these are things they might talk about in the vyver degree of recovery depends on the age of the patient with any nerve injury. The younger the patient, the better the chance of recovery and also the amount of fibrosis that has occurred at the time. OK right near tenodesis is a complete destruction of the peripheral nerve by any means.
So that's your. An amateur surgeon cutting a median nerve doing a carpal tunnel. Simple but very rare, it might be a laceration deep penetration injury. And this case is a generational distal to the lesion reduction studies show a loss reduction at three to four days.
Emg studies show fibrillation again two to three weeks. The only sort of surgical intervention is to repair the nerve, or whether by direct suturing or grafting at the time of the injury. Or we've got 3, 2 five day window, to be honest. And then the next option would be to consider. Um, whether you need to do a grant, I'm not a plastic surgeon, I'm not going to talk about that today because I get confused.
But if you again, this is something you talk about in the exam with regards to having a multi team disciplinary approach to get help and get there. OK, so there's just this all talking about where the seven classification comes in. So we've got on your apraxia. Which the old Sunderland was called type 1. That is all that conduction block. Then you axilo on Mrs. Can be subdivided into two, 3 and four.
So you've got your accidental discontinuity, which is type 2. So accidental discontinuity and in engineering disruption is a type free area of her unusual disruption and physical disruption is a typo. And there are two Mrs. Everything's discontinued. OK and this signifies were there any degeneration. So you can see well there in degeneration and degeneration in all of those. But that's just meant to say axons.
The axon is intact. All right so that's the key thing when you're talking about these. Look, and just another sort of demonstration of how the action works, though, in terms of you've got your disruption there, compression your sheath, your sheaf is lost. That's what we do about your loss, the disconnection and you can see this is a clarion degeneration occurring here.
Ok? again, we talked a bit about axonal regeneration that can happen with severe disruption. And you can see you've got your degeneration here, lost their cut there. Everything's been broken down distally and occasionally you can get a bit of their axilo regeneration with adjacent nerves, and that can take a very slow process, which tends to happen with people.
OK now, one of my exams I did, I was given a nerve conduction study to talk about that was in the basic science thing, so it is something that will come up. It's worth when you're in your hand clinic or when you're looking at her or talking to a patient, or if you've got carpal tunnel on your left, looking at the nerve conduction studies just to familiarize yourself with it so you can know what you might get thrown at you.
Ok? typically, it's they may say, why do we do it plays a key role in the evaluation of patients with neuromuscular disorders and also peripheral nerve injuries, and also can help. Importantly, in people with brachial plexus injuries, it can or any other sort of severe injury. You can look to see if there's any changes or improvements, and there are some key things we're worried about wave and reflexes.
OK so nerve conduction and imgs are different from the core or the core of electro diagnosis. These studies are performed usually performed first and usually yield the greatest sort of diagnostic value if the forms are interpreted correctly. They can help us really work out what things are, but they are not all the be all and end all. We still have to think of our clinical scenarios. That's the key thing if the marriage of both of those.
I do somewhat controversial at the moment with the whole sort of nice and NHS England talking about. We don't want to do carpal tunnels anymore, but they still need to be done because in terms of preventative, whatever generation ulnar nerve, they are important for patients and we're going to be using these a lot more and/or to justify doing these. OK, so there really be this one.
OK, so nerve conduction velocity is electoral diagnostic test provides information about abnormal conditions. The nerves are stimulated with a small electrical impulses by one electrode or another. Electrode detects the electrical impulse downstream from the first electrode. This can even be autonomic or at hydraulic, so reverse or straightforward. OK so again, on the basic science table, we may ask you to draw a Allen nerve conduction velocity or ulnar nerve nerve way.
The key thing is 0 is here, and I've been a bit naughty. They do that. Quite a few textbooks do that, so it's important that you remember. If you see something like this, it is. That's not zero. 0 is up here. So we're starting the resting potential of minus 70. I hope we all know this.
And you've got your stimulus applied. Eventually gets to 55 is the threshold, which creates the huge voltage rises to go to plus 30. This is merely volts, not four volts, thank goodness. And then voltage slap flows. And then you have your repolarization. They might ask, why do you have repolarization? But we understand that this is a question I think we'll ask in the vyver because I want someone to talk about it.
And then you return to your resting potential. I haven't got it on here, but they may also want you to talk about sodium and potassium levels in terms of what's happening here. But so that's something you need to think about as well. That could be the second could ask you to draw this and then ask you to talk about the sodium and potassium. Right, OK, so we need to know a few things with nerve conduction studies, the distance from the electrodes and the time taken for impulses to pass, and that helps us in terms of working out the speed transmission slower than normal, but indicate damage from direct trauma, stimulation of diabetic or peripheral neuropathy or nerve.
So the key thing is we're worried, more worried about carpal tunnel. OK so an EMG is basically the same thing, but looking at the motor response. And it's looking at what's produced by muscles. A lot of the time we do get both of those. And it's quite easy to get confused. And it's about the tiny amounts generated by the muscle cells when they're activated by the nerves acting within.
So there's several types intramuscular and surface emg, which one we use as most common is the intramuscular one involves inserting a small needle into the skin. Sometimes you can see the surface ones when we look at them in the clinic, I don't know. We used to have them, but they're not very accurate. And that hopefully detects a muscle impulse as well.
That's right. I was not surprised we back to where I'm supposed to be. OK, so here we go. Our apologies about that. So here we have an A Century one of median nerve. This is typically at antiarrhythmic, right?
Yeah, so we've got our little sensory parts here passing signal there we're looking at the wrist, at the elbow. Axilo OK. Signal is going this way. That's why it's anti-drone and we're looking at the responses there. So you can see. As we go further back gets less because hopefully the signal is being dissipated a bit more.
OK this is not atomic, as I said, and this is often ironic at this time. We've got our sensors here, we're sending it along here. This is a distance and we're measuring them in the wrong way around politics. Been, it's been stimulations. It's been this way. We're measuring it this way. Ok? this is all for dramatic sensory because this is the way the signal is going right?
Motor conduction, this sort of I get confused with it, I apologize about it. That's why. So this is going to be often drunk again. But the signal is going at direction. Because that's the way because the muscles are distraught, and so we're looking at that response again. But you can see high response there, less and less as we go further away.
Right? so this is an example of a sensory one that you might see. OK and this is the usual spots where they may put it for the carpal tunnel. A reference point active on the ground. That's usually what they have. On a couple of these, they're very confusing. And as I say, I didn't.
It looks really good when it works, but it doesn't work very often. I think if Iran remembers what we did then at work a few times like. OK so looking at the risk, we're looking at a nerve conduction velocity, this is. More stimulus going along this route. The elbow.
We might show a little spike there. That's that's the stimulus. You're resting potential going, creating the officials, causing a response. And that is our latency period. OK now, these are key terms that they're going to ask you in there, but they won't ask what latency? Latency measures the time between the stimulus and the response in milliseconds.
This is sort of basically the talking about your speed. OK so the one that's going to be our distance, I think, isn't it correctly? Yeah right. So that's our next one. This is just so the formulas you may work out, they have different things, but the key thing is remembering latency is measuring the time between the onset of the stimulus, the time the stimulus response.
OK OK, so this is a classic one of the median nerve. These are very complicated. I wouldn't worry too much about them. Now, some of the ones you may have. So we're looking peripheral nervous systems, so we're going to have an even a motor nerve conduction, a sea map, which is the stimulation of peripheral nerve while recording a muscle that innervated by that nerve. I've never got a snap, which is a sensory nerve conduction.
And that is a stimulation of a mixed nerve when recording for a mixed or continuous flow. Basically, your ulnar nerve or your median nerve? These are the terminology that they want you to spout out at the time, so latency is the interval between the onset of stimulus and the onset of response and amplitude is the maximum voltage difference between the two points is proportional to the number and size of fibers are being vaporized.
It basically equates to how good the quality of the response is. It tells you how good that nerve is. It could have. It could have a good response, as in a good latency. But if it's got a small amplitude, it could be still being crushed. Duration again, the time frame onset determination total duration is talks about the dispersion of all components, and it measured the difference in production nerve fibers.
I mean, you've got your overall conduction velocity, which we're talking about, the speed at which the nerve fibers are carrying electrical stimulus between the two sides. Comparison of conduction between two segments that can help us localize the lesion, which is why we look at the wrist, the elbow and the axilo. So if we got a normal speed at the axilo and the elbow and the reduced speed of the wrist to be in the median nerve, but we know it's carpal tunnel rather than something at the elbow or the slap.
OK so are typically our type of. Ones are going to be one for the sensory ones because we're looking at. So stimulates nerve and classically Yuzuru. And these are the usual ones we do meet in their. And typically, we're looking for people, agencies, conduction velocities. And that the amplitude in those situations.
And that tells us, as I say, those are the key things for how quickly they're being the stimulus cause that causes response and how much of a response is generated. Those are the key things. So speed and quality. Most conduction studies, these are very much in terms of telling us if there's any external degeneration, so demyelination, so damage to the axon.
Typically, they're gone for proximal to distal, evaluate for construction velocity looking at block so that again, ulnar medial nerves, the ones, the other ones that we can do, but they're not. That's really above and beyond for this exam. Now, these are ones they may ask, what type of wave is this or reflex, and if waves and waves are rare, they're useful for helping intensify demyelination and when there's more.
And usually on the motor EMG if there's amplitude or greater than 1 mile a boat. Look, I depend on the patients, right? So what is it that way? We're looking at that sort of response to the door for both horn doppelganger against the heat reflex. OK so they look at proximal roots and the antigen motor response, the anterior horn, the spinal cord, often dramatically to the muscle.
It's a pure motor test. A prolonged asymmetrical wave is suggested of a proximal root lesion, and its chemical is established in terms of we're talking about prolonged in violation of external injuries. Less sensitive than EMG for ridicule, since we're only looking at short segment there. OK so that's what they might show you. That's your see map.
I talked about earlier the motor action potential. And that's the wave response. Happens a little bit further along that feedback loop was happening in that picture. Thanks says that feedback loop. OK but as I say, it's just it's just the pure motor test. It helps us identify demyelination. OK these are some abnormal waves.
It's not coming in, says it should do, but you'll be very lucky if they show you that. Again, reflex reflex to offer drama. So going in the direction of a flow of entry and motor boat motor and sensory is very good for philosophy and median nerve rest. By recording a copy, radio is apparently typically a unilateral delay absent will suggest a problem. What's abnormal may not normalize that wherever it isn't in people with lots of volume rock.
So anyone over 60 or someone who's diabetic? Right, so that is your wave. That's the reflex later on. So these are just some of the techniques they might talk about being. Lacked a needle being said to the muscle, disposable single use and typically multiple muscles accessible examination.
If you. I don't know if you're a teaching hospital, if you can't go and have a look at the nerve conduction study. And just so you know what you send your patients to. OK and it's basically looking at activity and social activities. There's activity, motor unit configuration and experience that I don't think we'll ask you too much about that. But just to show you. This is what you might.
These are some of the things you might get. Be honest, this again, if you're getting to this point in the video, you're doing quite well. I'll move, move on. What they want for this for that. OK this is one thing I was going to ask about. They may also like it, may this is another thing they may talk about in the emails you took to draw a neuromuscular junction.
But that's another topic for another day. But we may talk about that in the liver because there's not very much to talk about in the pilot. The question is why? But this is a key thing as well. OK, thank you very much. Oh, brilliant. David, thank you very much. I just to refer, I think Sean has given a nice.
Look, when we first started this webinar teaching about the neuromuscular junction and how the complex process works and its own YouTube channel and has promised that was very great of you. David, we know you are not a neurophysiologist, but I think you've reached that level. So if you had electro engineering, then. But actually, it does pop in the exam a lot. Yeah, and it's one of those.
Suddenly, the examiner suddenly seemed to know everything about electrophysiology for some reason. They do have the answers in front of them. Yeah, but remember that it's unfortunately something you have to memorize. It is useful for clinical practice, particularly if you're going into an upper lip job or also. The problem is with this type of topic is you don't use it in your everyday practice.
It's only when you've got a nerve conduction study and you're in a busy clinic, you want to. You just want to read the report of your colleagues and say that, OK, we're going ahead with the median nerve compression. David is correct. Please take the opportunity to actually study what a nerve conduction study looks like, because you will be given a sheet of paper with sometimes just the waves drawn on and they'll say, what?
What is this and what is that? And sometimes they'll give you the numbers and so on and you'll say, what can you interpret this without any of the interpretations from your neuro physiologists? So do take the opportunity to do that. Second, it's worth going over this topic a couple of times. Watch David's video when it goes up on YouTube the second time, so it's a bit more solid.
Get the definitions down correctly. It's a brilliant presentation. Well done, David. I think that I agree this presentation contains everything you need to know. You just have to listen to it again and again for three or four times to record everything because a lot of information there and you need to.
But I think you got everything you need there that all the terminology to use that, you know, the buzzwords, the differences of between nerve conduction and imgs, the waves, the different waves they do. Ask all these questions. Unfortunately, you might be surprised, guys, but unfortunately they do ask them very frequently, even in part two of the why? When so and yes, they are asked to draw a nerve.
So you could start practicing from now, how to draw a cross-section of the nerve. It is very simple, but you could answer that easily if you have practice, but you have to practice in advance. Any comments from you for harm about? But for me, it is one of those topics that I would put it down as to be device. For example, you won't be able to device the whole thing, but individually, if you are making notes, make sure you write down what are the 10 15 topics that you want to revise before exam and on me personally, this is one of those topics.
Yeah, I think people might feel a little bit out of depth at this, but but don't go, don't worry, none of us knows much about nerve conduction studies. More than that's what this lecture. And so please, if you have guys any questions, come forward. But we will. We do encourage you to, but we've got to have survivor in a minute. I just want to reassure you if you can start talk, if you can say some of the terminologies, the definitions like latency, aptitude and what they imply by that, you're doing it, you're going to do well in that section.
They're not going to expect you to be a neurophysiologist. If if you look like you lecture, you understood it and you read it a bit out of it, you're going to get a good six seven. Hopefully we're orthopedic surgeons. We're not comfortable in this. This is why I said I put my hand up. I said, I'll do it. Someone has to do it because it is something that was a bugbear that threw me, and I just want to make sure it doesn't throw you when it comes to the exam.
Yeah, I think these days they are encouraged to ask about the clinical implications of everything, so they'll ask you, when would you do nerve conduction studies? And when we do imgs and give an example, for example, for each one when you do it to make it more clinically oriented question. So that could be something to look into.
I don't know if you, David, have, you know, any quick answer to that. Well, the reality is, most of the time you will you'll get a combined, combined nerve. Are you're going to get a median nerve. So you have an EMG and a nerve conduction study. The key thing is, you will, if there is axonal degeneration, so the axon is damaged axon devices, you will see demand, you'll see changes in emg, which is important.
But from a clinical point of view, in terms of recovery for the nerve, that's the key thing. Yes, it's a rule of thumb, you always get a bit of both. You always you rarely a nerve conduction studies only really important in pure radiculopathy. But there's very rare. We ask for those. I mean, we're not.
Neurologists tend to be the guys. Neurosurgeons tend to be the guys who answer those. That's any time you get just a pure nerve conduction study, but most part you get a combined sensory and motor or your combined peripheral nerves, your median nerve and ulnar nerve. I think the one fact that sticks to my memory is with the imgs, as the one used for clinical use of it is in the cases of radial nerve palsy following humeral shaft fractures and seeing fibrillation on the imgs is a sign that the nerve is recovering.
Yeah, so. I think I try to remember something useful about images, and I think that's the one fact, I could remember. That's related. So so that's good. OK, guys, so any more questions to ask, so we'll move on.
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