What is electromyography?
Electromyography (EMG) is a diagnostic technique that makes it possible to investigate the electrical activity of the muscular system: to find out the state of the peripheral nerves, spinal roots, and so on. The main objective of the method is to assess the electrical excitability and conductivity of nerve structures and endings. Using this method, it is possible to diagnose many diseases of the muscles, spinal column and musculoskeletal system.
When applying the electromyography method, the biopotentials of muscle fibers are read and recorded. The program itself analyzes the parameters of the study: the frequency of potentials, amplitude, spontaneous and evoked potentials of muscles and nerves are also studied.
In particular, electromyography reveals such health problems as:
- diabetic polyneuropathies
- toxic polyneuropathies
- traumatic neuropathies
- compression-ischemic neuropathy
- myasthenia gravis
- nerve neuropathy
- bone fractures
- amyotrophic lateral sclerosis
- muscle atrophy and wasting
- motor and sensory disturbances after various operations
- Parkinson's syndrome
Such diseases are most often accompanied by certain symptoms, for example:
- weakness and fatigue in the limbs
- numbness of hands and feet
- muscle spasms and limited mobility
- increased muscle tone
- frequent spontaneous fibrillation (twitching) of muscles in different parts of the body
- limb pain associated with sensory disturbances
Electromyography (EMG) is divided into two main types of techniques - stimulation and needle.
Stimulation EMG makes it possible to study muscle biopotentials and is carried out by applying surface disposable electrodes (on the skin area of the muscle under study) and recording muscle biopotentials with their help. The intensity of the applied pulses is selected individually for the patient; with a correctly selected pulse amplitude, the accuracy of the study will be very high.
There are a number of contraindications for the stimulation EMG method. It is recommended to temporarily postpone EMG treatment for patients in the acute period of such conditions as: angina pectoris, hypertensive crisis, etc., as well as at elevated body temperature. If there are wounds on the area of the body where the electrodes need to be installed, the procedure should be postponed.
Needle EMG is performed using needle disposable electrodes for recording intramuscular potentials (introduced into the muscle). Needle electrodes are used to study local or generalized muscle pathology. The procedure is carried out without the introduction of medications, it feels comparable to an intramuscular injection, under the supervision of a doctor, it is necessary to strain or relax the muscle on which the EMG is performed. This type of electromyography is of decisive importance in the differential diagnosis of neurogenic and primary muscular diseases and is used in neurology, orthopedics, endocrinology, dentistry, rheumatology, and some other medical fields.
As with the stimulation examination, needle EMG has contraindications: any infectious diseases transmitted through the blood (including HIV, hepatitis), violations of the rheological properties of blood, an increased pain threshold and children under 8 years of age.
As a rule, for correct diagnosis, these two methods (needle and stimulation EMG) are required together. The volume and order of the study is selected exclusively by the doctor who performs it, based on the preliminary diagnosis of the referring doctor and on the data obtained during electromyography.
In preparation for electromyography, there are no special restrictions on food, you can take medications with the exception of anticholinesterase drugs. It is necessary to follow the rules of hygiene, do not apply lotions or creams to the skin; the body must be clean. It is important not to overcool the legs and arms on the eve of the study.