Electromyography (EMG) is a diagnostic procedure to assess the condition of muscles and the nerve cells that control them (motor neurons). EMG results may reveal nerve dysfunction, muscle dysfunction, or problems with signal transmission from nerve to muscle.

 

Motor neurons transmit electrical signals that cause muscles to contract. In an EMG, tiny devices called electrodes are used to convert these signals into graphs, sounds or digital values, which are then interpreted by a specialist.

During a needle EMG, an electrode inserted directly into a muscle records the electrical activity in that muscle.

Nerve conduction studies, another part of EMG, use electrode stickers placed on the skin (surface electrodes) to measure the speed and strength of signals traveling between two or more points.

For more information about the team of neurologists at SanaMedic Medical Center, visit the services section of our website!

How do you prepare?

Food and medicine
When scheduling an EMG, ask if you should stop taking prescription or over-the-counter medications before the test. If you are taking a medicine called Mestinon (pyridostigmine), you should specifically ask if this medicine should be stopped for the study.

Bathing
Take a shower or bath shortly before the examination to remove oils from your skin. Do not apply lotions or creams before the examination.

Other precautions
The nervous system specialist (neurologist) who performs the EMG will need to know if you have certain diseases. Tell the neurologist and other EMG lab staff if:

1. you have a pacemaker or other electrical medical device
2. taking blood thinners
3. Have haemophilia - a bleeding disorder that causes prolonged bleeding

Before the procedure
You will probably be asked to change into a hospital gown for the procedure and lie on the examination table. To prepare for the examination, the neurologist or technician will place surface electrodes in different locations on your skin depending on where you are experiencing symptoms. Or the neurologist may place needle electrodes in different places depending on your symptoms.

During the procedureа

When the study is in progress, the surface electrodes will sometimes transmit a small electric current that you may feel as a prickling or spasm. The needled electrode may cause discomfort or pain, which usually subsides soon after the needle is removed.

During the needle EMG, the neurologist will assess whether there is spontaneous electrical activity when the muscle is at rest - activity that is not present in healthy muscle tissue - and the degree of activity when you gently contract the muscle.

He or she will give you instructions for resting and shortening the muscle at appropriate times. Depending on what muscles and nerves the neurologist is examining, he or she may ask you to change your position during the examination.

If you are concerned about discomfort or pain at any time during the study, you may want to talk to the neurologist about taking a short break.

After the procedure

You may have temporary, minor bruising where the electrode was inserted into the muscle. These bruises should disappear within a few days. If they continue to appear, contact your GP.

Results

The neurologist will interpret the results of your examination and prepare a report. Your primary care physician or the physician who ordered the EMG will discuss the report with you at a follow-up appointment.

Изотчници:

1. Rubin DI. Needle electromyography: Basic concepts. Handb Clin Neurol. 2019;160:243-256. doi: 10.1016/B978-0-444-64032-1.00016-3. PMID: 31277852.
2. Dondelinger RM. Electromyography–an overview. Biomed Instrum Technol. 2010 Mar-Apr;44(2):128-31. doi: 10.2345/0899-8205-44.2.128. PMID: 20586391.