Trainee Talk: Neuromuscular Ultrasound Applications in an Electrodiagnostic Laboratory

Meiling: My name is Dr. James Meiling, and I am a physiatrist and a current PGY-5 fellow in neuromuscular medicine (NM) at Wake Forest University School of Medicine in Winston-Salem, NC. In recent years, ultrasound (US) has become an increasingly useful tool in medicine. Medical schools, residencies, and fellowships alike are introducing US for practical clinical uses. For many specialties and subspecialties, learning how to properly use US has become a cornerstone in education. This is the case with neuromuscular ultrasound (NMUS) in the fields of NM and electrodiagnostic (EDX) medicine. Today we will be discussing how to apply and use NMUS in an EDX laboratory. My expert guest for this discussion is Dr. Michael Cartwright, a double board-certified neurologist and NM medicine specialist and professor in the Department of Neurology at the Wake Forest University School of Medicine in Winston Salem, NC. Dr. Cartwright has published and presented extensively on the use of NMUS, and I am excited to have him in our discussion today. For our first question, what is NMUS?

Cartwright: NMUS is, as it sounds, the use of a linear-array US transducer to visualize nerve and muscle. It is fairly straightforward; it is just using US to look at the peripheral nervous system.

Meiling: How does this differ from musculoskeletal US?

Cartwright: In a lot of ways, it doesn’t. They are very similar and there is a lot of overlap between the two. The people who first started looking at nerve and muscle called this “neuromuscular ultrasound,” while the people who first started looking at bones, tendons, ligaments, and joints called it “musculoskeletal ultrasound.” But now there is really a lot of overlap between the two. Physicians that are doing “neuromuscular ultrasound” may look at bone and those doing “musculoskeletal ultrasound” may look at nerve. There might be a little bit of an artificial divide at this point, but in clinical practice there is quite a lot of overlap between the two.

Meiling: I am coming from a background in physiatry, so I am used to musculoskeletal US. I know that it can be used in both diagnostic and interventional ways. Does NMUS tend to be more diagnostic, more interventional, or can it be applied in both ways?

Cartwright: It tends to be more diagnostic, but it can be used interventionally as well. Musculoskeletal US might have a little bit more of an interventional angle to it than NMUS does, but in NMUS, for example, you could use US to guide the needle for steroid injections into the carpal tunnel. NMUS does have a little bit more of a diagnostic focus, but you can use it for needle guidance and intervention.

Meiling: You have been using US, especially NMUS, for quite a while. What got you started in NMUS?

Cartwright: I started as a medical student in 2001. I had just decided I wanted to go into Neurology [for residency], so I approached Dr. Francis Walker here at Wake Forest and asked if there were any research projects that he would recommend for me to become involved with. He told me that he had been imaging muscle for about 10 years with US and that now US was at the point that you could see nerve, so he suggested I do a project to look at nerve. I scanned all my classmates and looked at their median nerve at the wrists. Then I scanned a handful of patients with carpal tunnel syndrome (CTS) to see what differences the median nerve demonstrated in those with CTS compared to healthy controls. I did that as a 4th year medical student, and it was a great project! I really enjoyed doing it and really enjoyed the US aspect. I wasn’t able to do much US as an intern but later in my residency I was able to get back into more nerve and muscle imaging. We first started with a special interest group at the AANEM annual meeting, added an “Ask the Expert” session, and then started holding workshops. It kind of took off from there. It went from a few workshops to more workshops, then courses, and then went to full courses exclusively based on US, like the UltraEMG course. So, it was really just a project that I started as a medical student, and it took off from there.

Meiling: Now that you’ve been using US for so long, how do you use NMUS in an EMG lab?

Cartwright: We use it, as you know, on a daily basis. We have US in our EMG lab. We have 4-6 EMG rooms going at one time and have a set up where the US is always on so we can wheel it from one room to another. You could also have it set up that you have an US machine in each room. It depends on the setup of your lab. But we use it on a regular daily basis in our EMG lab in combination with electrodiagnosis to look at focal mononeuropathies, muscle disease, polyneuropathies, motor neuron disease, traumatic nerve injuries, brachial plexopathies, and evaluation of dyspnea. All kinds of different conditions!

Meiling: As you’ve been using NMUS in the EMG lab, do you find that using US has kind of changed the traditional way that an EMG study is run?

Cartwright: Yeah, I think it definitely has. It adds the imaging component to the electrodiagnosis, which is a whole other area that we didn’t have in the EDX lab before US. It has changed the practice a little bit. For example, if there is a median mononeuropathy at the wrist by nerve conduction studies and I do US to find the median nerve is enlarged at the wrist, I might not do as much or any [needle] EMG to look for a C6 radiculopathy or to assess the severity of the median mononeuropathy at the wrist. US is an addition to the EDX practice, and it changed how the EDX practice is conducted.

Meiling: For those who may be reading this and worry that having nerve conduction studies, [needle] EMG, and adding in yet another component in that visit, do you find that it takes up more time and how do you manage adding in that third part?

Cartwright: Before we did US [in the EMG lab], which was more than 20 years ago, we saw 6 patients in a half day. Once we added US, we kept that number the same, so we still see 6 patients [in a half day] in the EMG lab. A lot of times the US doesn’t take that long. As I mentioned, you might do a little bit less electrodiagnosis if you do have US, so that subtracts some time there. You’ll have to figure out how to incorporate it into your practice, since every practice is different, but it is definitely feasible. I think it will help you to focus some of your diagnostic capabilities which may speed things up a little bit in the lab. There can be challenges but it is very doable.

Meiling: Now, NMUS is a billable procedure. What kind of things need to be included in your reports to be able to bill [for the US]?

Cartwright: You want to think about your imaging first. At the site of interest, you want orthogonal views, so at least two different planes of imaging. You will need to document these. For our documentation, we often will measure the nerve cross-sectional area and comment on the nerve echogenicity, vascularity, and mobility. You want to document all that information. We do a combination report, which includes the nerve conduction studies, [needle] EMG, and NMUS together in a single report, all at one time. Once you document it, you want to think about the coding. There are three main codes that we use in the EMG lab. We use a limited US code (76882), a complete US code (76881), and then a new code as of January 2023 which is a NMUS code (76883). The limited US code is for really just looking at one site and one site only. The complete US code is a radiologic code that we use but it is looking more extensively at a limb. The new NMUS code is for looking at a nerve throughout the course of a limb. The key to this new code is that you need to save a video clip in order to bill.

Meiling: If I were to scan the median nerve, I don’t need to save a video clip from the wrist all the way up to the axilla, right? I can just do it in a certain section, correct?

Cartwright: You need to look at the entire course of the nerve [with the US], but you only need to save the video clip over the site of interest.

Meiling: Where do you think NMUS might go in the future?

Cartwright: The future is wide open. It is imaging and it is all driven by computer technology. The computer technology keeps getting faster, stronger, less expensive, and more portable, so the imaging is just going to keep getting better and better. I oftentimes say that we want the imaging to be at the level of a biopsy. US imaging does keep getting closer and closer to that, you know, almost like a muscle biopsy or nerve biopsy which would be great because we can’t biopsy motor nerves. Getting the imaging to the point where it is close to the resolution of histopathology is the goal. There are a whole bunch of different imaging techniques, like elastography, 3-dimensional, and even 4-dimensional imaging, which will add information to our diagnostic tests as time goes on.

Meiling: As we come to a close, this may seem kind of daunting for the neurologist or physiatrist who hasn’t ever used US in this practice or in this way before. What kind of advice or tips do you have for them to get started?

Cartwright: I would say that people who do nerve conduction studies and EMG, physiatrists and neurologists, are trained and ready to do this type of imaging. They know the anatomy. They know the physiology. They know the pathophysiology. That is who should be doing these studies. That is point #1. Point #2 is that it is painless. You can practice on yourself. You can practice on colleagues, family, and friends if they have the time and patience. You can learn a lot by just scanning yourself with an anatomy textbook or app and using those in combination. I usually recommend starting by scanning the median nerve at the wrist. You are going to see a lot of suspected CTS in EMG labs so that’s where I recommend starting. After the median nerve at the wrist, then move to the ulnar nerve at the elbow. From there you can really take off and look at fibular mononeuropathies, more complex anatomical areas like the brachial plexus, or areas you may not be used to looking at like the diaphragm. I think once you have kind of mastered two sites, the median nerve at the wrist and ulnar nerve at the elbow, you can really expand from there.

Meiling: Well, thank you again for your time and discussion today. I really appreciate it.