Electromyography: what is it, indications and contraindications

Electromyography is a method of diagnostics that allows estimating the bioelectric activity of muscles, based on which can be concluded on the functional state of the nerve innervating the injured muscle. This study will help the specialist to determine the localization and spread of the lesion, the severity and nature of damage to the muscles and peripheral nerves. About what is electromyography, what are the indications and contraindications to this research, and also about measures of preparation for it and about a procedure procedure we will talk in our article.

Electromyography: the essence of the method

This study is carried out using a special apparatus - an electromyograph. Today it is a whole computer system that records the biopotentials of muscles, strengthens them, and then evaluates the obtained data.

The electrodes register the potentials of the muscles and transfer them to the electromyograph. The device amplifies the signal and sends it either to the computer monitor in the form of an image, or to an oscilloscope for subsequent recording on paper.

There are certain norms of electrical activity of muscles, which testify to their satisfactory function. If the parameters of the electromyogram go beyond these norms, they say about any disease of the muscle itself or the peripheral nerve that innervates it.

Types of electromyography

Depending on the type of electrodes, electromyography is divided into surface (global) and local.

• The superficial is a non-invasive study and allows the registration of muscle activity on its extensive site.
• When carrying out local electromyography, a thin needle is transdermally introduced into the muscle. This is an invasive technique that is used to study the function of individual muscle elements.

For each type of procedure, there are indications, therefore the question of which one should be used is decided individually by the attending physician. Often appoint both types of electromyography simultaneously.

Indications

The basis for electromyography is frequent muscle pain.

Electromyography can be given to a patient if he has the following symptoms or if he suspects the following diseases:

• a feeling of weakness in the muscles;
• frequent intense muscle pain;
• frequent twitching of muscles, convulsions;
• disease and Parkinson's syndrome;
• ALS (amyotrophic lateral sclerosis);
• myoclonus;
• myasthenia gravis;
• polymyositis;
• violation of muscle tone (dystonia);
• traumatic injuries of the peripheral nerves or organs of the central nervous system - the brain or spinal cord;
• multiple sclerosis;
• botulism;
• residual effects after a history of poliomyelitis;
• facial nerve neuropathy;
• tunnel syndromes;
• radiculopathy in spine traumas or hernias of the spinal cord;
• polyneuropathy;
• essential tremor;
• in cosmetology - to determine the areas of the body where botox should be introduced.

As a rule, the same patient is electromyographed repeatedly. The first examination - at the stage of diagnosis before treatment, and further - in the process of therapy in order to assess its effectiveness.

Are there any contraindications?

In general, electromyography is an absolutely safe, harmless and painless study, allowed even for children of childhood. However, for its implementation, there are contraindications common to many diagnostic manipulations:

• acute infectious or non-infectious diseases;
• epilepsy or other organic pathology of the central nervous system;
• diseases of the mental sphere, especially those in which the patient can not adequately control himself and perform certain actions;
• acute cardiovascular pathology (hypertensive crisis, attack of angina pectoris, acute stage of myocardial infarction and others);
• pacemaker;
• skin defects, pustular eruptions at the site of the intended effect.

Separately it is necessary to tell about contraindications to carrying out local (needle) electrostimulation, which are:

• the presence of the infection that is transmitted through the blood (HIV / AIDS, hepatitis and others);
• diseases of the blood coagulation system with increased bleeding (hemophilia and others);
• high individual pain sensitivity.

Electromyography: preparation for the study

Unlike many other diagnostic methods, there are no special preparatory measures for electromyography. However, when planning to go on research, it is worth considering the following points:

• stop taking drugs that affect the nervous or muscular system;
• a few hours before electromyography do not eat foods that increase excitability (such as chocolate, coca-cola, tea, coffee, energy drinks).

If in connection with a physical illness you should take a daily medication that reduces blood clotting, be sure to inform your doctor about it.

How is electromyography performed

The study can be conducted both in hospital and outpatient settings. During it, the patient is in a comfortable sitting position, half-sitting or lying down. The health worker processes the skin areas that will contact the electrodes, the antiseptic, and places the electrodes connected to the electromyograph on the muscle to be examined. During the introduction of a needle electrode into the muscle, a person feels non-intensive pain.

At the beginning of the study, the potentials of the relaxed muscle are recorded, after which the patient is asked to slowly strain it and at that time also fix the impulses.

The received record - an electromyogram - is estimated by the expert of a cabinet of diagnostics, and then transfers the conclusion to the patient or directly to the attending physician.

Explanation

The electromyogram looks a little like an electrocardiogram. It determines oscillations (oscillations) with different amplitude, frequency and periodicity. When the muscle only begins to contract, the magnitude of the amplitude of these oscillations is of the order of 100-150 μV, and in the state of maximum contraction it is 100-3000 μV. These indicators directly depend on the person's age and physical development. Distort the result can a thick layer of subcutaneous fat in the field of research and disease of the blood coagulation system.

• Myositis, muscular dystrophy and other primary muscular diseases cause a decrease in the amplitude of the oscillations, respectively severity of the disease (in the initial stage up to 500 μV, and in the terminal stage - even up to 20 μV with maximum excitation). At the local EMG at the same time, the number of potentials is within the normal range, however, their amplitude and duration are reduced.
• With polyneuropathies of any nature - toxic, metabolic, hereditary - surface electromyography registers the decrease in the oscillations, and also the single biopotentials that are different in amplitude and frequency. On the local EMG, polyphase relatively normal biopotentials are visualized. In the case if most of the nerve fibers died, muscle activity is minimal or absent altogether.
• Spinal amyotrophies on the local EMG are characterized by an increase in the amplitude of the oscillations, with acute waves. With surface electromyography, fasciculations are determined at rest, and when the muscle tension is pronounced, the so-called "pyloric rhythm" - potentials with high frequency and amplitude.
• Myasthenia gravis on EMG is characterized by a decrease in the amplitude of oscillations with repeated rhythmic stimulation of the muscle.
• Myotonic syndromes cause electrical activity of low amplitude and high frequency during muscle relaxation after its contraction, which gradually fades. Local electromyography registers hyperexcitability of the muscle - the emergence of a series of biopotentials after the introduction of an electrode into it.
• Essential tremor and Parkinson's disease appear on the surface EMG, as a series of rhythmic "volleys" to increase the amplitude of the oscillations and then reduce it. The duration and frequency of such volleys directly depends on where the pathological process is localized.

Are there any complications?

As it was said above, electromyography is absolutely safe for the examined diagnostic method, so it will not lead to any negative consequences. The only thing, in the case of carrying out a local type of procedure in the area of ​​puncture, sometimes a small size of the hematoma that can be accompanied by non-intensive pain sensations. This bruise in 100% of cases for 7-10 days passes independently and without a trace.

Often, electromyography is used in conjunction with a similar study of the function of nerves - electroneurography. These diagnostic methods complement each other and allow the specialist to see the full picture of a disease.

Presentation on "The concept of electromyography as a diagnostic process":

Electromyography as a diagnostic process

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