Electromyography (EMG) - a test to identify muscle disease. What is EMG?

Electromyography (EMG) is an electrophysiological test designed to evaluate the function of muscles and nerves. Consequently, EMG is helpful in diagnosing many neurological and muscular diseases. What is an electromyographic test and what are the indications for its performance?

Electromyography( EMG ) is aelectrophysiological testaimed at assessing the function of the muscular system as well as the peripheral nervous system. EMG is helpful in the diagnosis of many neuromuscular diseases because it allows to locate pathological changes in muscles, determine their size and nature, and determine the dynamics of the disease process in the examined muscle. Therefore,electromyographic examinationcan be used to diagnose, for example, muscular dystrophy, amyotrophic lateral sclerosis or spinal muscular atrophy. EMG is also used to diagnose diseases in which nerves have been damaged due to compression (e.g. carpal tunnel syndrome, tarsal syndrome), as well as neuromuscular junction diseases such as myasthenia gravis.

Electromyography - indications and contraindications for the test

The indications for EMG are symptoms of peripheral nerves and muscles malfunction, especially cervical and lumbosacral syndromes (shoulder, sciatica), stiffness syndromes of various etiologies, as well as excessive abnormal tension in the course of diseases nervous system (spasticity). Damage to individual muscles as a result of an injury or contusion is also an indication for the examination.

As in the case of electroneurography, contraindications to perform electromyographic examination are an implanted electric pacemaker, metal elements in the heart (e.g. an artificial valve) or in the area of ​​the body being examined.

Electromyography - how to prepare for the test?

On the day of the examination, wash the tested part of the body. It is contraindicated to use creams, ointments or lotions on the skin in the area where the test will be performed.

Immediately before the examination, inform your doctor about the medications you are currently taking.

Important

People taking oral anticoagulants (anticoagulants) should3 days before the test, start using low molecular weight heparin, of course with the prior consent of the attending physician.

In turn, patients with myasthenia gravis should not take anti-myasthenia drugs on the day of the examination.

Electromyography - what is the test?

There are four types of tests to complete EMG: Electroneurography (peripheral nerve conductivity test), muscle testing, neuromuscular transmission testing, and neuromuscular hyperactivity testing. In private clinics, each of the above-mentioned examinations is paid for separately.

Electroneurography is first performed, i.e. conductivity testing in peripheral nerves. After it, the actual test is carried out, i.e.muscle test , by means of which the efficiency of the tested muscle is assessed. 10 to 20 needle electrodes are inserted into the examined muscle (punctures are made at a distance of 1 - 2 cm from the previous one), which provide the muscle with an electrical stimulus, and then record the activity of the muscle during rest, any movement and maximum effort.

The neuromuscular transmission test(also known as the myasthenic test , boredomness testor fatigue test) aims to assess neuromuscular conduction, with the help of stimulation with a series of supramaximal stimuli, which is why it is used in the diagnosis of myasthenia gravis, i.e. muscle fatigue. The test is not invasive because it uses surface electrodes that are placed on the skin.

Neuromuscular hyperactivity test(akatetany test , ischemic test) is used to diagnose tetany, a disease that manifests itself increased neuromuscular excitability. The test is performed using a needle electrode, which is inserted into the muscle between the thumb and index finger. Then, for about 10 minutes, an elastic band is put on the patient's arm to stop the blood flow (the effect is no feeling in the hand and a strong tingling sensation, which is quite unpleasant). After the pressure cuff is released, it is monitored for the appearance of symptoms characteristic of tetany. The entire test takes about 15 minutes.

The results of the electromyography( EMG ) are provided immediately after the examination is completed.