Does an EMG Hurt?
YES.
How Much Does an EMG Hurt?
Now we're getting to a more pertinent question. Unfortunately, I don't have any good answer. To be more clear, I have done EMGs on myself, not for the entertainment value or to "understand the pain" my patients are going through, but typically to evaluate a new EMG machine, or maybe make sure it was working. And this includes sticking a needle in a muscle, always an interesting experience, since it seems I usually use a hand muscle to more easily relax it while I fiddle with the equipment. So on a personal level I have an understanding about how much it hurts, but that doesn't really help much.
The problem is, the reactions that one person has versus another are quite unpredictable and I have to say hard to make sense out of. Some tears are common; occasionally, not often, someone will bail out in the middle, saying, "That's enough, I'm done." But you can have a grown man crying, saying how awful the test is, and next do a child who hardly complains at all – what does that mean?
What About an EMG Hurts?
Nerve conduction studies amount to applying pulses of electricity at a point along the nerves, each pulse a fraction of a millisecond in duration, amounting to perhaps 200-300 volts, which sounds like a lot, but current only in the milliamperes. At first it's a little tickle perhaps, but it does get a bit of a "bite", shall we say, at higher intensities, and unfortunately we may need to stimulate a sick nerve more intensely to be sure we're getting the biggest response we can, since the biggest response assures that we are getting the fastest fibers stimulated. Most people seem to be able to tolerate this, maybe at worst shedding some tears. Having said this, we uncover histories of those whose older sibling, maybe even father, played a joke on them when they were young and had them touch a live electric fence or perhaps the wires hooked up to an old crank telephone. These people sometimes have a lifelong intense fear of electricity, and in the extreme cannot handle even low intensities of stimulation – a few seem to levitate off the table with each pulse. Oddly enough, one such man worked as an electrician.
The needle exam – well, a needle is a needle. On the other hand, this is a fine needle, a sharp needle. If we only needed to stick one spot it wouldn't be so bad, but unfortunately by the time the test is done we need to stick at least half a dozen sites, one for each muscle we evaluate. My theory is that everyone has their limit as to how many sites they will tolerate. For some that is one or less – rarely we get no farther than describing the needle part of the test. The two major pain-sensitive structures we deal with are the skin, and the fascia of the muscle. Once you're through the skin, there shouldn't be much more pain from that source.
Poking through the fascia isn't so bad, but as we have the patient activate the muscle, the needle starts tugging on the fascia and this increases pain. Once you're in the muscle, the pain is that deep, achey pain you get with an intramuscular shot, although since we're not injecting anything into the muscle, lacking that crescendo of pain from the actual injection part. Occasionally, not so often, you can actually manage to hit a relatively insensitive spot in skin and maybe even in fascia too, so a patient might say, "I didn't even feel that at all." In the end, about all I can say is that, when patients do sum things up, they might say, "Well, it wasn't as bad as I thought it was going to be." This is not true for those who have extreme reactions like passing out with the sight of blood or needle sticks. I have learned that while it is rare, it is possible to pass out while you are lying flat, given an intense enough degree of hypotension.
The Spiel
Here is what I tell my patients about the test before we start, and considering that I've been doing EMGs for 27 or so years I have said these words more times than I can imagine:
"We're going to do two different kinds of things in this test. The first part is to tape some wires on the skin, then put little electrical signals in the nerves to see how well these signals travel along the nerves. After that, I'm going to put a little needle in some of the muscles and see whether we can find any signs of nerve or muscle damage that might show up on this test."
I very purposely say "signals" rather than "pulses" or "shocks", since I think these are excessive terms for what is happening. At the same time, I don't mince words and do indicate this is electrical, and do specifically say the word "needle", usually with some verbal emphasis. Typically, this leads to one or more questions, may lead to questions about the pain issue, but if nothing else it's the start of getting a sense of how this person is going to tolerate the test.