Contents
Electromyography (EMG) is a modern method for diagnosing the activity of muscle tissue. A technique is used to determine the functional abilities of nerves, muscles and soft tissues. With the help of EMG, the degree of damage after injuries 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 lesions are in soft tissues, diagnosis using radiography is not carried out: EMG shows the characteristic features of damage to muscle tissue and peripheral nerves.
For diagnostics, an apparatus is used – an electromyograph. The device consists of an integral computer system capable of recording certain signals (biopotentials) of muscle tissue. With the help of the device there is an increase in biopotentials, which allows you to determine the degree of damage to muscle tissue without a surgical diagnostic operation.
Diodes are attached to the computer system, which register deviations from the norm. With the help of the device, the signal is amplified, and an image is displayed on the screen that displays the state of the muscle tissue and peripheral nerves of the body area under study. Modern devices display the image directly on the monitor, but the old generation electromyograph captures the received impulses on paper.
During normal functioning, a certain muscle impulse is created – it is the change in the impulse (deviation from the norm) that fixes the device during the diagnosis. The doctor analyzes the resulting image, which allows you to identify damage and pathology of muscles or nerves.
Variety of EMG
Modern devices differ in the types of transmission diodes: the range of such details determines the accuracy of the results obtained. 2 types of devices are used for surface and local examination. Global diagnostics takes place in a non-invasive way (non-contact) and allows you to see the activity of muscle tissue over a large area of the body. This type of diagnosis is used in cases where the cause of pain or damage within the muscles is unknown. Examination of a large area allows you 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 part under study. Previously, the body area is anesthetized and treated with disinfectants. It is a thin needle electrode that makes a minimal puncture. An invasive technique is suitable for examining a small part of muscle tissue.
The choice of technique depends on the alleged problem and on the doctor’s prescriptions. The indications for EMG are patient complaints, injuries and injuries that affect walking and human mobility. In some cases, for an accurate diagnosis of the problem, 2 types of EMG are assigned at once: local and global.
The feasibility of an EMG
This safe technique is being used to examine patients suffering from muscle pain. EMG is used as an independent or auxiliary procedure. Weakness in the muscles and cramps are a common reason for visiting a neurologist.
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 the elderly who find it difficult to move around. It is advisable to conduct electromyography before competitions or heavy physical exertion.
Indications for the procedure
Pain is a direct indication for EMG. Sudden or frequent muscle pain is a warning sign that should be addressed immediately. 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, myoclonus or amyotrophic sclerosis. Electromyography is prescribed for suspected development of polymyositis.
It is advisable to diagnose muscles in case of loss of their tone (dystonia) or after injury to peripheral nerves. Damage to the central nervous system, brain or spine 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 poliomyelitis. For facial neuropathy or carpal tunnel syndrome, invasive electromyography is used. Direct appointment to the procedure are diseases: microstroke or tremor. For the safe introduction of Botox, an EMG is used beforehand.
The patient is assigned the required number of procedures that do not harm the surrounding tissues. The first examination falls on the initial stage of diagnosis before the appointment of treatment. During therapy, EMG is performed repeatedly. Electromyography is also used for prevention in adults and children.
Direct contraindications
In total, electromyography is a safe procedure that is prescribed to patients of different sex and age categories. EMG does not harm. Painful sensations during the introduction of diodes are removed with the help of local anesthetics. A diagnostic procedure is allowed even for children with muscle problems.
Contraindications to the procedure:
- infectious diseases with pronounced symptoms;
- non-communicable chronic diseases in the acute stage;
- epilepsy;
- a disease of the central nervous system that can interfere with the examination of muscle tissue;
- mental disorders (an invasive procedure is especially carefully performed for patients with mental disorders);
- acute heart failure;
- angina pectoris;
- the presence of an electrical stimulator;
- skin diseases.
In most cases, contraindications relate to the needle procedure. The technique is not prescribed for patients with diseases that are transmitted through the blood – AIDS, infectious diseases, hepatitis. For people with a blood clotting problem, an EMG is undesirable.
Insertion of the needle occurs with minimal bleeding, but the simple procedure can be a problem for people with impaired blood clotting. Hemophilia is a direct contraindication for invasive diagnostics. Individual pain threshold is a contraindication to EMG.
Possible complications
EMG is a safe research method. Cautions apply to the healing of the wound, which is formed at the site of the introduction of the diode. The hematoma formed at the puncture site heals within 10-15 days. After the puncture, the skin does not need additional processing.
If EMG is prescribed in combination with other procedures, the doctor talks about restrictions and warnings after the procedure. In addition, electroneuromyography is prescribed, which allows you to fully assess the degree of damage.
Contraindications to an additional diagnostic method are the same as to electromyography.
Preparing for an EMG
EMG does not need long preparation. Before prescribing the procedure, the features of its implementation are taken into account: before electromyography, psychotropic drugs or medications that affect the functioning of the nervous system are stopped. Before the start of the procedure (a couple of hours before the EMG), you should not eat or drink energy drinks. Avoid caffeine, chocolate and tea.
If during treatment the patient takes drugs that affect blood clotting, it is necessary to additionally consult with a doctor before the procedure. Any contraindications are taken into account before the start of the diagnosis. For small children, EMG is performed in the presence of parents.
Stages of the procedure
The procedure is carried out on an inpatient and outpatient basis. During the EMG, the patient should be in comfortable conditions (sitting, standing or lying down). Before the invasive technique, the skin area through which the diode is inserted is treated with an antibacterial agent. Antiseptics are used for processing. The health worker inserts the diode and fixes it for further diagnostics.
During the procedure, the patient experiences slight discomfort – this is how the diodes read the impulses of the muscle tissue. At the beginning of electromyography, the muscle potential is read in a relaxed form: these data will become the basis for the study of muscle tone. At the second stage of the procedure, the patient needs to tighten the muscles: the impulses are re-read.
Results
The results obtained are a snapshot (electronic image). The first to evaluate the state of muscle tissue is the specialist who conducts the diagnosis – the doctor of functional diagnostics. Based on his conclusion, the attending physician makes an accurate diagnosis and prescribes effective treatment.
The patient himself does not decipher the results of electromyography. The diagnostician does not prescribe further therapy: he assesses the condition of the muscular and nervous tissues located in the part of the body being studied.
An electromyogram looks like a picture of a cardiogram. It consists of oscillations: the amplitude of the oscillations is determined by the state of the human muscle tissue. For the diagnosis, the height and frequency of oscillations are important.
Decoding of the obtained results
Image interpretation begins with the analysis of amplitude fluctuations. Normally (average data), the magnitude of the oscillations is from 100 to 150 μV. The maximum reduction sets the rate equal to 3000 μV. The value of the indicators is determined by the patient’s age, muscle tone of the body and lifestyle. The results obtained may be distorted by a pronounced fatty layer (patients with obesity). Poor blood clotting also affects the results obtained.
Reduced amplitude indicates muscle pathologies. The lower the obtained indicators, the more severe the degree of pathology. At the initial stage, the amplitude decreases to 500 μV, and then to 20 μV – in such cases, the patient needs urgent hospitalization. On local EMG, the indicators may remain within the limiting norm (for such cases, it is advisable to conduct additional examinations).
Rare oscillations indicate pathologies of a toxic or hereditary nature. At the same time, polyphasic potentials are recorded on local electromyography. With a large number of dead fibers, muscle activity is absent. An increase in amplitude (sharp waves) indicates spinal amyotrophy. With the development of myasthenia, the amplitude decreases (after muscle stimulation). Low activity (low amplitude) at the time of exercise indicates the development of myotonic syndrome.