Electromyography General Remarks (Content and Purpose)

This content includes a lot of grammatical and vocabulary errors.Please cut me some slack from Japan.

Electromyogram is a very painful and much-disliked test. The patient says, “I’ll never come back! This was the first time in my life that I was told to do an electromyogram (laugh). I studied this EMG for a moment when I was a student. But I hardly need it, so it is immediately beyond my memory. I never thought that electromyography would become one of my jobs (laughs).

Outline of the examination

An electromyogram consists of the following two tests

(1) Nerve conduction test (≒Nerve conduction velocity test) which conducts electricity to the nerves. It doesn’t just look at speed! Get a nerve conduction test! There is a school of thought that says, “Ignore it, it doesn’t matter.” Since the EMG is only for CMAP, the inclusion of SNAP is still a nerve conduction test… !!!! It seems to me that the)

2) Needle electromyography, in which a needle is inserted into the muscle

Both (1) and (2) are painful. (1) is a slapping and pinching feeling. (2) is a pain like being gouged in the back. It looks painful just by writing it.

But anesthesia cannot be used. Anesthesia puts the nerves to sleep. And because the nerves are asleep, muscle movement is also slowed down. Then it is no longer clear whether it is normal or abnormal, so there is no point in doing (1) and (2). You have to endure the pain. So they hate it even more.

Nerve conduction test

This test is performed on patients who complain of “tingling or numbness,” “dull sensation, as if being touched on the clothes,” etc. As mentioned earlier, electricity is passed through the nerves to check the speed and difficulty of the transmission of electricity. The most common causes are diabetes and carpal tunnel syndrome. Both of these diseases cause damage to peripheral nerves.

It takes about 5-10 electrical stimulations to examine one nerve. The number of nerves to be examined is about two, but for some cases, two types of nerves, motor and sensory, are examined, so a total of about four nerves are examined. In addition, the F-wave test requires continuous stimulation of 16 to 20 times, which is a bit tiring.

But depending on the disease, we may examine more than that number of nerves. How many do you often do? The answer is, “I don’t know. The answer is, “I don’t know.” As I do, I decide whether to increase or decrease the number.

Needle electromyography

As the name implies, a needle is inserted into a muscle to study electricity. Unlike a nerve conduction test, this test does not apply electricity, but rather examines the electricity emitted by our muscles.

The pain of a needle electromyogram varies greatly depending on the muscle to which the needle is pointed. A prick at the base of the thumb or between the thumb and index finger will cause sharp pain. However, if the pain is in the shoulder or thigh muscles, the pain is relatively light and dull.

The most important result of the needle EMG is the “at rest” result. It is no exaggeration to say that this is the purpose of this test. By the way, “at rest” is when the muscles are not contracted, relaxed, and relaxed. If this can be done smoothly, the examination time and pain time will be shortened.

However, it is quite difficult to relax when a needle is inserted. When I instructed a foreigner to do this before, he said, “Relax with a needle in you? You can’t do it, you’re crazy! I didn’t listen to him because he was speaking English (lol).

But the most important thing to know when you are “at rest” is whether your nerves and muscles are “hit right now” or “hit all the way through. If they are “damaged right now,” this result is very important because there is a possibility that the disease can be cured or progression can be prevented by treatment. On the other hand, if the disease is “already beaten up,” it will be difficult to recover even with treatment.

Once the patient is at rest, the next two instructions, “exert yourself a little” and “exert yourself to the utmost,” are given and the examination is over. These two are not that difficult. All you have to do is to put in some force.

The above is the sequence of events. At least two muscles are inserted during the examination, and at most eight to ten muscles are inserted. The needle itself is actually very thin, thinner than a needle used for an intravenous drip or blood collection. However, it does sting the muscle (fascia), which causes pain.

Purpose of the examination

So why such a painful test? The reason is that electromyography is the only test that can examine nerves and muscles easily and directly.

There is also a biopsy, in which the nerve or muscle itself is cut and removed, but it is much more painful and time-consuming than an electromyogram. Incidentally, anesthesia is not available for biopsies either. (General anesthesia and transmissible anesthesia are acceptable.)

Therefore, even if it is a little painful, a simple electromyogram is chosen. There are imaging tests such as X-rays, CT, and MRI, but as mentioned previously, these are only “reference findings” or indirect findings. MRI is looking at the rotation (spin) of hydrogen atoms. It does not look directly at the disease itself. Therefore, EMG, which can directly examine the disease itself, is a very important and meaningful test. Also, being able to know “what is being done right now” as mentioned above is very important in terms of prognosis, and treatment methods will change drastically.


I wrote this in a slightly threatening manner, but there is no use in lying, because what hurts hurts. However, if a medical professional thinks carefully and performs the EMG appropriately, it can be a very useful test and reduce the amount of time spent in pain. There is no need to be overly fearful. On the contrary, it is more painful to miss a treatment opportunity because of fear.

That’s all. Thank you again.