This post was written by Lawrence “Larry” Kennedy, MD, PPG – Parkview Physical Medicine & Rehabilitation.
In a previous post, we explained what Electromyography (EMG) is and the diagnoses often associated with it. In this post, I dig into what patients can expect and how the testing plays into the broader diagnostic puzzle.
What is EMG testing like for the patient?
The patient comes in, and we take them back to the room. My nurse goes over their medication list and what they can expect during the procedure. If they’re cold, we might have to warm the extremity being tested.
I come in and explain the procedure and answer any questions they might have. I collect a detailed history of their symptoms and perform a detailed pertinent physical exam based on their history.
When it’s time to perform the procedure, I let the patient know that they are in control. In my 30-year career, I’ve done approximately 12,000 EMG procedures. It’s rare, but if they tell me they cannot complete the test, we stop. We have had a patient return at a later date after receiving medication to decrease their anxiety, but this is rarely required.
I usually start with the nerve conduction study, which is somewhat uncomfortable. We use two electrodes to record. The electrodes are a few centimeters apart. A stimulator is placed on the skin to provide the electrical current.
If I knew exactly how much stimulus to give a patient to obtain the complete response, I would just give them one shock and that'd be it. But I don't know. So, we start with very low stimulation and then gradually turn the stimulus up and monitor the response. We continue till the maximum response is obtained.
For the needle exam, we insert a special needle electrode through the skin. We advance the electrode into the muscle and study different areas of the muscle at rest. When this is completed, I have the patient activate the muscle and monitor the response.
After the testing is done, I explain the results to the patient and answer any questions. My report is sent to their provider.
What kind of information does an EMG provide to the clinical team?
Our goal is to answer the provider’s question.
We let the provider know if there is evidence of disease of the peripheral nervous system or not. Often this test tell us the result, but in some cases, they indicate that we additional data, such as imaging, blood work, or a muscle biopsy is needed for a conclusive diagnosis.
There are instances where the testing tells us what is wrong, but not why. Our job is to provide information including the location and extent of the muscle and/or nerve damage and the prognosis.
Are there any risks or side effects associated with EMG?
The risks and side effects are very low. As you would expect, patients can experience pinpoint bleeding at puncture sites and mild bruising or muscle soreness. EMG’s can be done in patients on blood thinners and in patients with pacemakers.
How does an EMG differ from other diagnostic tools, like an MRI or a CT scan?
All these tools are different, and they all have their place. EMG is a test of the function of muscles and peripheral nerves, while imaging studies are pictures of the anatomy.
With our EMG testing, we can determine, at times, the chronicity and severity of the disease. For entrapment neuropathies such as carpal tunnel syndrome, nerve conduction studies are the gold standard.
EMG and imaging studies are often complementary and together can be very helpful at arriving at the correct diagnosis.
But let’s say you had a pinched nerve in your back or your neck, or a muscle disease. In those instances, if I could only do one test in that case, I would do an MRI.
What should a patient do to prepare for an EMG?
They will need to take a bath or a shower the morning of the test. They shouldn’t use any lotions, because the electrodes won't stick properly on the skin. I recommend loose clothing that won’t restrict their movement. Gowns are provided if needed.
Is there any aftercare required following the procedure?
None.
What are some examples of diagnoses guided by EMG testing?
Nerve conduction studies are the gold standard in confirming suspected carpal tunnel syndrome.
I had a woman who was a habitual leg crosser and she developed a foot drop. We did the EMG and noticed her nerve signal was getting partially blocked. Below your knee on the lateral side, if you run your finger down, there's this little bony knot. That's the fibular head. And the peroneal nerve comes around that knot. If you cross your legs too long, it can damage that nerve. Our testing revealed her nerve was getting partially blocked at that knot.
Another example that I still remember from years ago - the patient came in with extreme pain in his right arm and armpit. I examined him and learned that he was a smoker. His eyelid was drooping, and his pupil was very small. I suspected he had a condition called Horner’s syndrome, where the sympathetic nerve fibers in the upper chest are damaged. I was highly suspicious of a tumor in his upper lung. The man was in severe pain, and I felt an EMG was not necessary and instead, I sent him down for a CT scan, and they did find a tumor. This was an example of identifying the most appropriate testing for the individual.
EMGs can be helpful in determining the correct diagnosis.
Want to learn more?
If you are experiencing symptoms, speak to your primary care provider. Patients do not need a referral to undergo EMG testing, but it is important to work with your full care team in your pursuit of a diagnosis and subsequent treatment plan.
