Medical research and diagnostics

Electromyography (EMG)

Electromyography (EMG) is a modern method for diagnosing the activity of muscle tissue. The technique used to determine the functional abilities of nerves, muscles and soft tissues. With the help of EMG, the degree of damage after trauma is diagnosed or the dynamics of long-term treatment of muscle tissue is determined.

The essence of the method

Electromyography is a research method that determines the localization of possible damage. If the foci of inflammation are in the soft tissues, no X-ray diagnostics is performed: the EMG shows the severity of the disease, the characteristic features of damage to the muscle tissue and peripheral nerves.

For the diagnosis used apparatus - electromyograph. The device consists of a complete computer system capable of recording certain signals (biopotentials) of muscle tissue. Using the device, biopotential amplification occurs, which allows determining the degree of soft tissue damage without surgical diagnostic operation.

Diodes are connected to the computer system, which register deviations from the norm. With the help of the apparatus, the signal is amplified, and an image is displayed on the screen that displays the state of the muscular tissue and peripheral nerves of the investigated body region. Modern devices display the image directly on the monitor, while the electromyograph of the old generation captures the received pulses on paper.

During normal operation, a certain impulse of the muscles is created - it is the change of impulse (deviation from the norm) that fixes the device during the diagnostics. The doctor analyzes the resulting image, which allows you to identify damage and pathology of muscles or nerves.


Modern devices differ in the types of throughput diodes: the range of such parts determines the accuracy of the results obtained. Used 2 types of devices for surface and local examination. Global diagnosis is non-invasive way (contactless) and allows you to see the activity of muscle tissue in a large area of ​​the body. This type of diagnosis is used in cases where the cause of pain or damage inside the muscles is unknown. Examination of a vast area allows us to trace the dynamics in the treatment of chronic diseases.

Local EMG is carried out using the contact method: the electrode is inserted directly into the test part. Pre-section of the body is anesthetized and treated with disinfectants. It is a thin needle electrode that makes a minimal puncture. The invasive technique is suitable for examining a small portion of muscle tissue.

The choice of method depends on the doctor's prescription. The indications for EMG are patient complaints, injuries and injuries that affect the walking and mobility of a person. In some cases, for the exact diagnosis of the problem, 2 types of EMG are assigned at once: local and global.

The feasibility of EMG

A safe procedure is used to examine a patient who suffers from muscle pain. EMG is used as an independent or auxiliary procedure. Muscle weakness and cramps are a common cause of contacting a specialist.

If there are no additional symptoms in the patient, a safe and simple procedure is prescribed by the doctor. EMG is indicated for children and older people who find it difficult to move. It is advisable to conduct electromyography before the competition or heavy physical exertion.

Indications for the procedure

Direct indication for EMG is pain syndrome. Sudden or frequent muscle pain is an alarming sign that should be immediately responded to. Intense muscle pain and muscle twitching require additional examination of muscle tissue. With the help of the EMG procedure, the diagnoses are confirmed: myasthenia gravis, myoclonium, or amyotrophic sclerosis. Electromyography is prescribed for suspected polymitosis.

It is advisable to diagnose the muscles in case of loss of their tone (dystonia) or after injury to peripheral nerves. Damage to the central nervous system, brain, or spinal cord is the reason for a complete examination of muscle tissue using EMG.

Diagnosis is prescribed with the introduction of diodes for suspected multiple sclerosis, for botulism, after suffering poliomyelitis. In neuropathy of the facial nerve or tunnel syndrome, invasive electromyography is used. The direct appointment to the procedure are diseases: spinal hernia or tremor. For the safe introduction of Botox, pre-EMG is used.

The patient is assigned the required number of procedures that do not harm the neighboring tissues. The first examination occurs at the initial stage of diagnosis prior to treatment. During therapy, EMG is performed repeatedly. In order to prevent electromyography is used for adults and children.

Direct contraindications

In total, electromyography is a safe procedure that is prescribed to patients of different gender and age categories. Harm EMG does not cause. Painful sensations during the introduction of the diodes are removed with the help of local anesthetics. The procedure is allowed to diagnose even children with muscle problems.

Contraindications to the procedure:

  • infectious diseases with pronounced symptoms;
  • noncommunicable chronic diseases;
  • epilepsy;
  • a disease of the central nervous system that may interfere with the examination of muscle tissue;
  • mental disorders (an invasive procedure is especially carefully carried out for patients with mental disabilities);
  • acute heart failure;
  • angina pectoris;
  • the presence of an electrostimulator;
  • diseases of the skin.

In most cases, contraindications relate to the needle procedure. The method is not assigned to patients with diseases that are transmitted through the blood - AIDS, infectious diseases, hepatitis. For people with a blood clotting problem, EMG is undesirable.

Needle insertion occurs with minimal bleeding, but a simple procedure can be a problem for people with platelet disruption. Hemophilia is a direct contraindication for invasive diagnosis. An individual pain threshold is a contraindication for EMG.

Possible complications

EMG is a safe method of investigation. Cautions relate to the healing of wounds, which is formed at the site of introduction of the diode. The hematoma formed at the puncture site lasts for 10-15 days. The skin does not need additional treatment after the puncture.

If an EMG is prescribed in conjunction with other procedures, the doctor tells you about the limitations and cautions after the procedure. In addition, electroneuromyography is prescribed, which allows you to fully assess the degree of damage.

Contraindications to the additional diagnostic method are the same as for electromyography.

Preparing for EMG

In the long preparation of the EMG does not need. Before the appointment of the procedure, the specifics of its implementation are taken into account: before electromyography, psychotropic drugs or medications that affect the nervous system function are stopped. Before the procedure begins (a few hours before the EMG), one should not eat food or drink energy drinks. Caffeine, chocolate and tea are excluded.

If during the treatment the patient takes drugs that affect blood clotting, before the procedure, you must additionally consult with your doctor. Any contraindications taken into account before the start of diagnosis. EMG is conducted in the presence of parents for small children.

Stages of the procedure

The procedure is carried out in inpatient and outpatient settings. During an EMG, the patient must be in comfortable conditions (sitting, standing, or lying). Before the invasive technique, the skin area through which the diode is inserted is treated with an antibacterial agent. Used for the treatment of antiseptics. The health worker inserts a diode and fixes it for further diagnosis.

During the procedure, the patient experiences a little discomfort - this is how diodes read pulses of muscle tissue. At the beginning of electromyography, the potential of the muscles is read in a relaxed way: this data will be the basis for the study of muscle tone. At the second stage of the procedure, the patient must strain the muscles: the pulses are re-read.


The results obtained are a snapshot (electronic image). The first condition of the muscle tissue is assessed by a specialist who carries out the diagnosis. Based on his opinion, the attending physician makes an accurate diagnosis and prescribes an effective treatment.

The patient himself does not decipher the results of electromyography. The diagnostician is not engaged in the appointment of further therapy: he assesses the state of the muscles and nerves located in the studied part of the body.

Electromyogram looks like a cardiogram image. It consists of oscillations: the amplitude of oscillations is determined by the state of human muscle tissue. The height and frequency of oscillations are important for diagnosis.

Interpretation of the results

Decoding the snapshot begins with an analysis of amplitude oscillations. Normally (average data), the magnitude of oscillations ranges from 100 to 150 µV. The maximum reduction sets the rate to 3000 µV. The value of the indicators is determined by the patient's age, muscle tone of the body and lifestyle. The results may be distorted by a large body fat (patients with obesity). Poor blood clotting affects the results obtained through diodes.

Reduced amplitude indicates muscle diseases. The lower the scores, the harder the degree of neglect of pathology. At the initial stage, the amplitude is reduced to 500 μV, and then to 20 μV - in such cases, the patient needs urgent hospitalization. On the local EMG, the indicators may remain at the maximum rate (for such cases it is advisable to conduct additional examinations).

Rare oscillations indicate toxic or hereditary pathologies. At the same time, polyphase potentials are fixed on local electromyography. With a large number of dead fibers muscle activity is absent. An increase in amplitude (sharp waves) indicates amyotrophy. With the development of myasthenia, the amplitude decreases (after muscle stimulation). Low activity (low amplitude) at the time of loading indicates the development of myotonic syndrome.

Watch the video: What is an electromyography EMGNerve Conduction Test NCT? (February 2020).