Dr. Paget: My name is Dr. Stephen Paget, I’m the Physician in Chief at Hospital for Special Surgery, and I’m pleased today to introduce Dr. Joseph Feinberg, who’s an associate professor of rehabilitation medicine at the Weill Medical College of Cornell University. Just to start off, Dr. Feinberg, because some people might not know what a physiatrist is; could you let the audience know that?
Dr. Feinberg: Sure. Physiatry is a small specialty. There are probably 5,000 board certified physiatrists in the country. The specialty is young – it was established in the 1950s. It’s a specialty that overlaps with orthopedics and neurology.
We’re non-surgical specialists. We don’t perform any surgery, but see a lot of non-surgical orthopedic and neurologic problems. We’re also one of the two specialists that perform electrodiagnostic studies, the other specialists being neurologists.
Dr. Paget: What is an electrodiagnostic test?
Dr. Feinberg: An electrodiagnostic test, also commonly called an EMG, is a study that evaluates peripheral nerve and muscular function.
The testing is usually done to evaluate for peripheral nerve injuries from accidents, nerve entrapment syndromes like carpal tunnel syndrome, nerve diseases like Lou Gehrig’s Disease (otherwise known as ALS), and muscular disorders like muscular dystrophies. The test can also tell if symptoms are coming from a more generalized process called a peripheral polyneuropathy.
Dr. Paget: Or some combination of those, which we call a “double crush” type syndrome.
Dr. Feinberg: That’s right. That’s a condition where the same nerve is being injured at two different points, at the neck and wrist, for example. The patient could also have an underlying medical condition like diabetes that can cause a generalized peripheral polyneuropathy. This can make the nerve more susceptible to being injured from compression in the wrist and may lead to carpal tunnel syndrome. So the electrodiagnostic test allows us to localize where that site of compression is.
If a patient had neurological symptoms like weakness or numbness, electrodiagnostic testing might be the appropriate thing to do. But this is only after a thorough physical exam, and it should be correlated with the clinical findings of the patient. The test then helps identify if there is a peripheral neurological problem, where it’s coming from, whether it is localized to one spot, or whether it’s indicative of a more generalized condition.
After that diagnosis has been made, we then come up with a treatment plan. Sometimes that may include surgical intervention, some type of physical or occupational therapy, medication, an injection, or additional testing.
Dr. Feinberg: For electrodiagnostic testing, there are only two medical specialists that are trained to do that: neurologists and physiatrists. The training is pretty similar. It’s part of their residency or fellowship training.
There is an additional certification of specialty in performing electrodiagnostics one can obtain by passing an exam given by the AANEM [American Association of Neuromuscular & Electrodiagnostic Medicine].
Dr. Paget: That could be either a neurologist or a physiatrist.
Dr. Feinberg: That’s right.
Dr. Paget: And then you choose the one that you feel most comfortable with and have had experience with in the past.
Dr. Feinberg: That’s right. A patient might further inquire how specialized the physician is in performing this test.
Dr. Paget: So let’s go into one of the bread and butter things that you deal with, like carpal tunnel syndrome. Typically made worse by overuse, irritation, arthritis, something that presses the nerve.
A patient experiences some numbness and tingling in the distribution of the median nerve, they wake up at night, they shake their hands out, they may have problems dropping objects because they’re weak, and they go to their doctor, and their doctor makes the decision that carpal tunnel syndrome may exist. And their doctor refers them to you. What do you do?
Dr. Feinberg: Those types of symptoms would be classic for carpal tunnel syndrome, which is an entrapment of the median nerve in the wrist, but they could also be indicative of other types of nerve problems. A pinched nerve in the neck – cervical radiculopathy or generalized peripheral neuropathy could cause similar symptoms.
The electrodiagnostic evaluation allows you to isolate the problem and tell you if it is, in fact, carpal tunnel syndrome. This not only localizes it, but also allows us to determine how badly the nerve is damaged.
Dr. Paget: So tell us what EMG stands for.
Dr. Feinberg: EMG stands for electromyography. That’s usually the second component of the test, but the term is often used to describe the entire electrodiagnostic test.
We usually perform nerve conduction studies first. This is performed by stimulating the nerve at several points and recording the response.
EMG testing involves placing very small needles – almost acupuncture-like needles – into the muscles, which record electrical activity coming from the muscle. These electrical signals tell us if the nerve or muscles are functioning normally.
These needles are a little uncomfortable, a little unpleasant, but usually cause minimal bleeding. There are very rarely contraindications to performing nerve conduction studies or the needle exam.
Dr. Paget: So I see patients with carpal tunnel syndrome, I often try to decrease the over-activity which might be causing their problem, or treat their arthritis. I might give them an anti-inflammatory, I may even inject the area with steroids, and I give them a wrist splint to stop the pressure on that area.
So say somebody continues to have a problem, actually has weakness and may need to go to surgery. Does everyone who’s going into surgery for release of the carpal tunnel pressure need an EMG and nerve conduction study?
Dr. Feinberg: Carpal tunnel syndrome, like most other conditions we diagnose, is based on the clinical evaluation and the clinical assessment. And when problems are very straightforward, the patient does not need to undergo electrodiagnostic studies.
These studies are more commonly done if they’re suspicious that there’s another underlying problem, or if the symptoms may be coming from another area than the wrist. Sometimes the patient’s symptoms may not correlate with the severity of the carpal tunnel syndrome and electrodiagnostic testing may help the treating physician quantify the degree of nerve injury.
Dr. Paget: Thank you very much.
Dr. Feinberg: Thank you.
Reviewed: 10/21/2009 Published: 4/30/2007