Neuromuscular Ultrasound and Electrodiagnostic Correlates: Upper Limb, Lower Limb, and Disorders of the Phrenic Nerve/Diaphragm Muscle-Neuromuscular Ultrasound and Electrodiagnostic Correlates: Upper Limb, Lower Limb, and Disorders of the Phrenic Nerve/ Diaphragm Muscle

Neuromuscular Ultrasound and Electrodiagnostic Correlates: Upper Limb, Lower Limb, and Disorders of the Phrenic Nerve/ Diaphragm Muscle
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Good morning everyone. It is a great pleasure to present Neuromuscular Ultrasound and Electrodiagnostic  Correlates in Focal Entrapment Neuropathies. This is going to be a total of three presentations.  First by Dr. Todd Lakowitz, who is Assistant Professor and Associate Program Director at Department of Rehab Medicine at Zucker School of Medicine at Hofstra and Northwell in New  York. And second talk will be given by me. I'm Dr. Kim at UTHealth San Antonio, Texas.  I'll be covering ultrasound and electrodiagnostic correlates in lower extremity entrapment neuropathies.  And lastly by Dr. Colin Franz, who is a physician scientist at Shirley Ryan Ability Lab in Chicago,  Illinois. He will assess ultrasound exam of diaphragm muscles in phrenic motor neuropathies. And please hold your questions until the end of three presentations. We will have  question and answer sessions. Okay. Without further ado, Dr. Lakowitz. Thank you Dr. Kim and good morning everyone. I'm going to be doing the talk on Neuromuscular  Ultrasound and Electrodiagnostic Correlates of the Upper Extremity. I have no financial disclosures.  So the objectives of today is to appreciate the strengths and shortcomings of electrodiagnostic  techniques and diagnosing common entrapment neuropathies in the upper limb. And the second  objective would be to understand how ultrasound can complement the electrodiagnostic evaluation  of entrapment neuropathies. Third is to learn to visualize the normal and pathological ultrasound  appearances of the median ulnar and radial nerves. So just as a quick review of the volar wrist cross-sectional anatomy, I'm just going to see if we have, do we have a red light?  We have a green one there. Green. Ah, yes. Thank you. Carpal tunnel, the volar wrist, carpal bones. So I'm not going to spend too much time. This is for your review.  So electrodiagnostic and ultrasound evaluation of the median nerve. Common nerve conduction studies are highly sensitive for detecting subtle nerve conduction slowing, especially  when you use comparison nerves, radial or ulnar for references. Robinson's combined sensory index has been documented previously with a total sensory index which should be  less than 0.9 milliseconds. I'm going to show you a little bit of that coming up. There's a rather dramatic lack of consensus regarding what constitutes mild, moderate,  and severe median mononeuropathy at the wrist. Neuropathy with slowing, but little or no  conduction block may be considered mild. Neuropathy with slowing and conduction block, but little  or no axonal loss may be considered moderate. And neuropathy with significant axonal death may be considered severe. And that's from Dr. Strakowski's book.  So how do we gauge the severity of median mononeuropathy at the wrist? Well, most of us use Bland's criteria which was published about 20 years ago. And this is just the montages  that we use to do some of the comparisons. I just wanted to show that to you. This is the numb thumb study where difference of distal sensory index should be less than about 0.5  milliseconds. So this is the invaluable ring study, the distal sensory latency difference between equiline segments of the median and the ulnar nerve should be about less than  0.4 milliseconds. So we'll get to the ultrasound in just a little bit. This is a mixed nerve  study which you can use, also called the transcarpal 8. Value should be less than about 0.3 milliseconds.  It's orthodromic. As you know, it may include both. It includes both motor to lumbricals and sensory fibers. I don't like using this particular study because you're operating  under the assumption that the motor and sensory branches are equally affected. So another technique you can use to try to localize the lesion to the wrist is Kimura's  inching technique described 25 years ago. But it's very time-consuming and tedious, but you certainly can use it. So this is one of my favorite teaching slides, how we  incorporate ultrasound. And really what I wanted to show with this slide is the effects of fascicular anatomy, fascicular involvement of peripheral nerve lesions. And you can see  how a space-occupying lesion on the ulnar side of the radial nerve will preferentially affect different fingers. So a decreased third finger snap, fourth finger snap.  So, the best electrodiagnostic determinant of the extent of axonal loss is the size of the distal snap and CMAP, okay?  Comparison of proximal and distal sensory and motor nerve action potentials enables determination of axonal injury versus neuropraxia, and therefore relative severity.  That's by Kimura, and that's how we teach. Needle exam can be helpful, but it's helpful for identifying lesions proximal to the site  of entrapment, i.e. a cervical radiculopathy or a brachial plexus lesion, because those  disease states will cause numbness and tingling in the hand and or pain that can mimic a carpal tunnel.  The needle examination can also be helpful in identifying more proximal median nerve lesions above the level of the wrist.  Ultrasound has good correlation with electrodiagnostic findings and median neuropathy at the carpal tunnel, good sensitivity and specificity. I have some references for you here.  It's very reliable in identifying the anatomical landmarks and their relationship to the median  nerve in the carpal tunnel, especially useful if you are planning needle-based interventions. The most common site of enlargement of the median nerve is proximal to the tunnel, what  we call the carpal inlet, and I'm going to show you the ultrasound boundaries of that. The cross-sectional area or the CSA of the median nerve at the inlet is the most consistently  used measure and appears to have the highest correlation with clinical and electrodiagnostic abnormalities.  Measurement of the outlet is more technically challenging and tends to have less inter-rater  reliability because the nerve dives deep and you really have to toggle the transducer back and forth to isonate that nerve and to light it up so you can see it and measure it.  Side-to-side comparisons, not very useful in a disease entity such as median mononeuropathy at the wrist because it tends to be bilateral.  You can calculate a ratio of the CSA of the median nerve from the inlet to the forearm and that, if it's greater than 1.4, is abnormal, that has a high sensitivity for median nerve  entrapment at the wrist. And how we teach how you want to do this calculation is to measure the CSA around the inner border  of the bright or echogenic epineurium surrounding the fascicles and I'm going to show you how to do that.  Most studies suggest that a CSA greater than 11 at the inlet is abnormal, borderline is between 10 and 13.  If you find a really enlarged nerve, it's dark, it's swollen, there are hypolacoic fascicles  and it's over 13, that is abnormal across all patient groups. What you have to understand is that ultrasound has not been shown to be as effective in determining  severity of median mononeuropathy at the wrist as compared to electrodiagnostic studies. So it is complementary.  The degree of swelling frequently does not reliably affect the extent of neuropathy, i.e. the degree of axonal loss and this is a gray area, especially when we move into  the ulnar neuropathy at the elbow, which I'm going to get to next. Demyelinating lesions can often display larger nerve cross-sectional areas than nerves with  severe axonal injury and that's from Strakowski's book. But patients with axonal degeneration, on the other hand, some have significantly larger  CSAs and wrist to forearm ratios than those with conduction block. One study showed the increased wrist to forearm ratio correlated with reduced snap amplitude,  which did reflect the degree of axonal degeneration. So I'm kind of giving you conflicting information, but this is the state of the science as it is now.  So the newest evidence in PMNR 2021, prospective study, 95 patients referred for electrodiagnostic  testing of carpal tunnel, used both Robinson's and Bland's criteria, measured the median nerve cross-sectional areas at four sites, you know, commonly I do two.  All ultrasound measurements had high diagnostic accuracy for CTS, but poor concordance with the severity via the clinical scales we use, Bland's and the CSA severity grades.  However, the change in the CSA had the highest diagnostic accuracy. I'm sorry if I'm going a little bit fast, but I want to leave time for my colleagues  for their presentations as well. So scanning tips, you need a high frequency transducer, at least 10 megahertz with a small footprint.  Normal peripheral nerves do have this honeycomb appearance when imaged in short axis secondary to the hypoechoic fascicles surrounded by hyperechoic perineural tissue.  And you need to toggle the transducer and to use anisotropy, which is an artifact to help differentiate the nerve from the underlying flexor tendon.  So it's really kind of the art more than the science of how to image nerve tissue.  And this may be a little bit contrary. You know, you want to scan quickly in short axis, proximal to distal. Why?  Because nerves dive and you can very, your eye can see the nerve diving as you scan proximal to distal to identify the structure of interest, right?  The median nerve will cross radial to the flexor tendons and then ulnarly and deep between the FDS and the FTP.  Normally the median nerve will glide in transverse and longitudinal views. This may be decreased secondary to increased pressure across the tunnel. And you want to use your machine.  You know, what we teach in EMG is that, you know, EMG is not TV.  You need to know how to, you know, utilize the machine, gain, sweep. Same thing with ultrasound.  You want to use all the capabilities of your ultrasound machine to draw out the pathology of the tissue that you're looking at. So look for increased Doppler flow as an example.  Look for relatively swollen hypoechoic fascicles, right? These are believed to be consistent findings in medium mononeuropathy at the wrist.  So I'm going to show you some nice kind of pictures and then I'm going to show you some pictures from my academic practice.  So this is kind of where we are at the anterior elbow and this is, these are normal size nerves,  median nerves, and it should be a little hard to see a normal nerve on ultrasound up proximal  in the arm that's not pathological, should be a little difficult to see and that's normal. Okay.  So here down at the wrist, okay, transverse carpal ligament, median nerve, flexor tendons. Here are the borders of the inlet, right? Pissiform here, outlet is here.  entrapments. This is at the level of the distal radial ulnar joint. CSA is 15. It's proximal to the inlet. It's enlarged. And then when you get to the inlet, it doubles, okay? And  at the outlet, and then it becomes relatively constricted. So it swells proximal to the entrapment, tapers a little bit distally. And if you spin the probe longitudinally,  you can see what's called a notch sign. And I'm going to show you that. So this is one of my patients. This was a median nerve entrapped at the wrist, at the  inlet measured out to be 22. Just look how large that nerve is. It's dark. It's hypoechoic.  It measured out to be 22 millimeters square. That's very enlarged. And then at the outlet, right, the nerve is deeper. It is relatively compressed, right? So it goes down to 16.  And then what I do, you spin the probe, okay? And you can look for right up here is the thickened transverse carpal ligament. And then you can hand this information over to  your referring, let's say, orthopedic hand surgeon and say, well, look, here is the thickened ligament. Here is your notch sign. Operate here. You know, obviously they have their  own standardized protocols of how, where they make their incision. But you can tell them where is the relative site of compression. And that's why we like to do this. Okay. So  here's another one of my patients. I'm sorry. I'm just going to come around because I have a better view of the monitor here. So this is a bifid median nerve. This is a variant  of anatomy. And if you're not sure what you're looking at, that's okay. That's another reason  to use ultrasound because it can help orient you. So, I mean, even if you measure one fascicle of this bifid median nerve, it measures out at 18, but I wasn't sure what this was at  the time when I was doing it. So that's okay. I put the color on it. I put the Doppler on. Well, that's the ulnar artery. Okay. So, well, and convention is now, so you're not going  to do a CSA on the whole structure. You're going to do a CSA on each of the divisions and then cemate them. And that's how we do it. So this is an example of a median, a bifid  median nerve.  very crucial because on this view here, cross-section and longitudinal view, this is the hypoechoic enlarged abnormal echo features is a part of the nerve.  It is quite fun, to be honest, and surprising at times.  All right, I'd like to just  So how do we assess the diaphragm? Ultrasound is a great option.  Breathing out, it's relaxing.  and it's like a paper-thin diaphragm, there is muscle, but you see the two bright lines  and you have to be a really keen observer to pick out that that is actually the muscle because it's also not contracting. And so Ali Farr, who's now in practice  So, you know, we could go ahead and confirm.  on this side. So I think putting it together, uh, we  out there. The protocol is published. It's a pretty good one.  of it I really like I will I will venture into  72 year old. Prolonged COVID.  Uh, there's our workhorse, Ellie Farr. There she is.  So can we take them off the ventilator? When should we start to try this?  Thank you.