Hello, and welcome to our sixth and final week of the AANEM APP webinar series. Today our session is entitled, How to Read an EMG Report from an APP's Perspective by Dr. Andrew Dubin. Dr. Dubin is currently a professor of physical medicine and rehabilitation at the University of Florida, Department of Orthopedics and Rehabilitation Medicine in Gainesville. He is medical director of the Acute Inpatient Rehab Hospital at the University of Florida, Shands. Thank you, and enjoy. All right, so good afternoon. Today we're going to be discussing interpretation of an EMG report, and we're going to look at it from the perspective of an advanced practice provider, looking at the results that come back from an electrodiagnostic study relative to a patient that they have been taking care of. And I think it's imperative to understand that when you order an electrodiagnostic test or EDX or EMG study, the question that needs to be addressed is, what are you looking for? And probably the biggest mistake that gets made is the test is sort of used as a fishing expedition, not really sure what you're looking for. And the way to avoid that pitfall is to really make sure that you've secured an appropriate history and a detailed, yet focused neuromusculoskeletal exam that allows you as the provider to establish in your own mind what the most likely diagnosis is and what reasonable differentials are also in the equation. Then you can send the patient for an electrodiagnostic evaluation, asking the electromyographer to tailor the test to address the questions that you have, so that when you get the report back, the data should hopefully make sense and allow you to definitively answer the question in mind. Along that lines, I've brought with me today my PA, Rachel. Hello. Hello. Worked very closely with me, and I would actually ask her at this point, what questions does she have that run through her mind when she would consider ordering an electrodiagnostic study? So like you said, it's part of a full history, physical, and a workup for your patient. So I think that based on the history and physical that you've gotten, that's what's going to cue some of those, okay, maybe we need to actually get an EMG to differentiate between what we're finding in our physical and what could be possible based on the history. I think Rachel's point is very well taken, and it's worth emphasizing that the need for the electrodiagnostic study grows out of the history and physical, and that question of, is there something about the history in concert with the physical exam findings that leads to the conclusion that an electrodiagnostic study would in fact be an appropriate diagnostic tool or evaluation at that point? Just getting an EMG because you're looking for an answer without really knowing what the question is, is sort of the road to perdition, because if you look long enough and hard enough, you can probably get some abnormal data back on an EMG or an EDX study, but then you're left with the problem of, I have abnormal data, what's the significance of it? Is the data truly abnormal or is it spurious results, and am I now left chasing something that has no relevance at all? And I think along those lines, a case that was very illustrative for myself and my residents who were working with me years ago, was a 63-year-old lady who got sent to us, and I know Rachel has heard this story several times, and I think she found it very informative because it was very, it drove home the point of context. So it was a 63-year-old woman who presented to an outside institution with a six-month history of progressive weakness in the lower extremities. And based upon that snippet of information, she was sent for an MRI and an EMG. But what was evident when the rest of the data was collected at that point was there was a paucity of data that had been collected. The presentation was progressive six months, lower extremity weakness. There was no documentation of any significant physical exam being done, no documentation of reflexes or strength. The patient was sent merely for an MRI of the lumbar spine and an EMG. MRI of the lumbar spine was done and the patient was diagnosed with lumbar spinal stenosis. EMG was done and she was diagnosed with a polyperipheral neuropathy based upon small compound motor action potential amplitudes with distal amplitudes to the EDB as well as the abductor hallucis being below the lower limit of normal. Her abductor hallucis amplitude was down around two millivolts. Her EDB amplitude was down around a millivolt and her sural sensory amplitude was noted to be four microvolts with a superficial fibular amplitude of four microvolts and she was diagnosed with a polyperipheral neuropathy. She was sent to my office because of the diagnosis of lumbar stenosis to see what could be done for her lumbar stenosis because as a physiatrist that would be an area that we would take care of. What was interesting was that in the interim she had a second EMG done by another group out in the community at that time and their diagnosis was one of a profound axonal motor neuropathy. And what made this diagnosis so interesting and head scratching was that the compound motor action potentials were quite small. They had actually gotten smaller compared to the previous study which had been done three months earlier and they were now, for the abductor hallucis, down at no greater than a millivolt and the EDB was down around 500 microvolts and the sensory amplitudes looked reasonably well preserved at approximately four to six microvolts for the sural and the superficial fibular. The needle EMG however was totally unremarkable. There was no signs of active denervation. So it immediately throws into question the veracity of the diagnosis of a profound axonal motor neuropathy because one would expect that the needle EMG would be floridly abnormal. Yet how do we reconcile small amplitudes with a normal needle EMG? When the patient presented to the office she was noted to ambulate to the examining room with a walker with bilateral foot drop. So she clearly had weakness. When you asked her to change into a dressing gown, what was most notable was that the lower leg musculature was preserved in terms of muscle mass. There was no atrophy. One would have anticipated if this was an axonal motor neuropathy or a severe polyperipheral neuropathy resulting in foot drop, there should be atrophy of the lower leg muscle groups and there was not. So that already starts to get you to question the validity of either of those two diagnoses. On examination, she is clearly weak. Her dorsiflexors are less than anti-gravity grade. Her plantar flexors are less than anti-gravity grade. Her knee extensors are barely anti-gravity grade. Hip flexors are anti-gravity grade, three grade, no better. She's also weak in the upper extremities at approximately four. Additional history at that point reveals on query that this has been progressive now for more than six months because by the time she gets to us, she's now greater than six months. She's had a 20 pound weight loss unintended in six months time. She is a smoker. She also complains of a dry mouth on direct question. Question at this point is what now starts to come into your differential diagnosis? Well, the physical exam of preserved muscle mass with significant weakness, with a dry mouth, with diffuse weakness, with areflexia, no reflexes were elicited, starts to raise the question, particularly on a needle EMG study without signs of muscle injury of whether or not this is a neuromuscular junction defect. And in a smoker with a dry mouth raises the question of Lambert-Eaton myasthenic syndrome. This was a fun case because my resident was sitting in the room with me as we were examining the patient. I turned to him and I asked him, I said, what's the test you would like to do to confirm the clinical suspicion? Because he whispered in my ear, I think she might have LEMS. I said, well, I think you're right. What would you like to do? He says, well, can I take her into the EMG lab, obtain a median motor study to her hand, and then do isometric contraction of her thenar muscles for 15 seconds and repeat one stimulus and see if we get facilitation? And I looked at him and I said, I think that would be a wonderful thing to do. And we brought her into the EMG lab on a supermaximal stimulation, median motor to APB. We got a two millivolt response. We did 15 seconds of sustained isometric contraction, repeated the stimulation, same parameters, didn't change the stem intensity or stem duration at all, and a two millivolt response jumped to a 6.5 millivolt response. That degree of facilitation is seen in Lambert-Eaton myasthenic syndrome and really nothing else. We're not done, though, because now we know there's an increased incidence of underlying carcinoma in these patients, and we had to send her for additional studies, which included CT scan of chest, abdomen, and pelvis, and the CT scans, in fact, came back showing a lung lesion, which was appropriately treated. And to this day, the woman is still alive, and this is now 14 years later. So I think this case is illustrative of the fact that when you order a test, particularly an EDX or an EMG, it's incumbent upon the person ordering the test that they really have in their mind what their most likely diagnosis is, along with reasonable differential diagnoses, and they really need to be thinking about what questions do I have and what questions am I looking to be answered. Then when you get the EMG back, it becomes intuitive as to whether or not it was a good study. The first line should tell you, is this normal or abnormal? This is a normal study. This is an abnormal study. If it's an abnormal study, the next line should then say, this study is abnormal for the following reasons, and detail the abnormalities. And then there should be a summative line at the bottom, or a summative paragraph that says, the electrodiagnostic data, including the following, in concert with the physical exam findings, is all consistent with this potential diagnosis, or this potential group of diagnoses. And then it's easy to figure out whether or not it was a good study. So based upon that, Rachel, are there any questions that you would like to ask me at this moment? So I think for providers that are not specialized, especially for APPs, if you haven't worked in physiatry for a long time, you haven't worked with neuromuscular neurology for a long time, what are some signs early on in your workup, as far as your history, physical, even labs that you want to order, what are some signs of, maybe I should refer to a physiatrist to do an evaluation in the EMG, or I should go ahead and order the EMG myself? And I think that's an excellent question. And I think for an advanced practice provider, nurse practitioner, PA, the things that should get you to start thinking about, would an electrodiagnostic study be helpful, or should I consider sending this person either to a physiatrist or to a neurologist for additional workup, would be on the basis of your neuromuscular exam, are you seeing asymmetry in terms of reflexes? So are you seeing preservation of reflexes on one side of the body, let's say patella and Achilles in the left leg, but on the right leg, both are absent. And in concert with them being absent, are there sensory phenomenon, do those sensory phenomenon map out to a radicular distribution, a plexopathic distribution, or is sensation totally intact, but they're missing reflexes? And then, what are the reflexes elsewhere? I think a common mistake that gets made is the patient gets sent for the referral of right leg weakness, and the exam is limited to the right leg. We don't bother to look at the left leg and realize, oh, there are reflexes missing on the right, but on the left leg, they actually happen to be hyperreflexic. And in the upper extremity, they're hyperreflexic. And their sensory exam is totally normal. And now I actually have a constellation of findings that potentially become very worrisome. I have absent reflexes, which suggest lower motor neuron, and they may have some atrophy, which further supports lower motor neuron. I also have hyperreflexia, which is suggestive now of upper motor neuron, but I have preserved sensation. So I now have upper motor neuron, lower motor neuron, with preserved sensation. Motor neuron disease starts to percolate up fairly high in my differential diagnosis. I may have the same constellation of findings with some paresthesias in the hands, which could be concomitant carpal tunnel, or it may be a cervical radiculomyelopathy. But at least now I can start to organize in my head what are the possibilities. So I may, at that point, want to order a cervical MRI to see do they have significant spinal stenosis, which could easily cause a lot of these findings. And then they also have lumbar stenosis, which is causing the leg findings. Do they have carpal tunnel superimposed on top of motor neuron disease? Because I'm still going to order the cervical MRI. The cervical MRI, in one case, may come back with significant stenosis. I now have a pretty good explanation for what's going on. The cervical MRI comes back unremarkable. They do have carpal tunnel, but the remainder of the electrodiagnostic study shows diffuse denervation in lumbar distribution, cervical distribution, and at that point, I can do a cranial nerve innervated muscle for needle EMG, a sternocleidomastoid, and if that is showing signs of active denervation with preserved sensory studies on the electrodiagnostic test, my diagnostic paradigm now dramatically shifts towards motor neuron disease. But because I approach the test in an organized fashion based upon the history and the physical, I can rank order differential diagnoses, which makes it possible for me to obtain a cervical MRI, have that data while I'm getting the EMG done, and now I can take all of that data and put it together to arrive at, is this a cervical radiculomyelopathy in isolation? Is this bilateral carpal tunnel syndrome and lumbar stenosis causing the right leg problems? Is this bilateral carpal tunnel syndrome and motor neuron disease on top of it? But I've got those differentials already in my head, and as I start to get data back, I can rank order them, and as I start to do my electrodiagnostic test, I can adjust my test to help elucidate those findings. And I think the question you ask, and that I'm trying to answer, is the appreciation that the test is a dynamic test. It's not cookie cutter. It's not formulaic. It's a living, breathing test, and it actually evolves and changes as data comes back to the electrodiagnostic physician in real time. And then they adjust the test and modify the parameters of the test to help really focalize on the diagnosis. I like what you said earlier, too, which was facilitating the electromyographer, so you yourself can do EMGs. As an APP, it's more likely that someone else will be doing the EMG. So that differential is really critical in helping the EMGer actually first reduce the number of sticks, but also make them count. And I think that's also important for patient comfort and patient trust and preventing a prolonged workup for an issue that could possibly have a fairly quick treatment that should be started. So I think that that's important. You talked about some EMGers, you say, rule out one issue, and that's all they will do. But if you say, well, I'm really worried about, and you can give your full differential, you can give more of that physical exam that facilitates the EMGer to really give you the information that you actually need to make the diagnosis. And I think that point's well taken, in that if, as an electrodiagnostic physician, I know what the referring physician or APP is interested in, what their concerns are, in a very systematic fashion, I can go about addressing those questions and coming up with positives and negatives on the study that either, that will confirm one of those possibilities or effectively rule them all out. And then in a summative conclusion, I can say, we've effectively ruled out all of these things for the following reasons. This is still a possibility and may require further workup. And I can even give some suggestions as to what might be reasonable things to do to continue the workup. All right. I thank you for your questions. It's me to think about the best way to approach this. Hopefully, everybody found this to be informative. Thank you. Thank you. We appreciate it.

electrodiagnostic study

interpretation

advanced practice provider

diagnosis

context

collaboration