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Electroneuromyography
Last reviewed: 23.04.2024
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[Indications for electroneuromyography
- Development of motor deficiency in infectious disease, associated (in the opinion of the attending physician) with peripheral nerve and / or muscle involvement, early preclinical diagnosis of motor deficiency.
- Evaluation of the effectiveness of ongoing therapy in a patient with neuroinfection with the presence of lesions of the peripheral nervous system.
Preparation for the study of electroneuromyography
Before the study, the doctor is advised to stop 8 to 12 hours before the study of the appointment of drugs that affect neuromuscular transmission (proserin).
The study is carried out in the morning, before meals or after 1,5-2 hours. Before the electroneuromyography, the patient is calmed and informed about the procedure, the sensations that he will experience, including the painfulness of carrying out electrical stimulation.
The procedure for the study of electroneuromyography
The study is carried out in the lying position on the back or in the semi-base in a chair in a relaxed state.
In electroneuromyography, two types of electrodes are used: surface (dermal) and needle. Electromyographic recording of the action potentials of individual neuromuscular motor units is performed with needle electrodes. The called muscle potential (M-response) is recorded with the help of surface discharge electrodes, which more objectively, in comparison with needle, reflect the total activity of the muscle. Atraumaticity, absence of infection risk, ease of treatment and relative painlessness of the study are the advantages of surface electrodes. To find the locations of the stimulating and tapping electrodes, use the manuals and diagrams of JA DeLisa, K. Mackenzie, B.M. Gekhta, L.O. Badalyan, I.A. Skvortsova.
When carrying out electroneuromyography of the upper and lower extremities, stimulating bipolar wick and standard bipolar cutaneous recording electrodes are used. They are placed on the skin over the area of the locomotive point of the muscle: the main one - on the skin above the abdomen of the muscle being examined, and indifferent - on its tendon. The skin is rubbed with alcohol before applying the electrode, and a special electrode gel is applied to the skin-electrode contact area. The potential difference from the cutaneous electrodes is fed to the input of the electroneuromyography amplifier. Between the recording and stimulating electrodes, a surface ground electrode is mounted on the skin of the subject. The felt wicks of the stimulating bipolar electrode are moistened with an isotonic solution of sodium chloride before the beginning of the study. The cathode of the stimulating electrode is placed above the motor point, the anode is distal.
When conducting a complex electrophysiological study, standard methods of stimulation electroneuromyography are used, with determination of the speed of impulse conduction along motor fibers of peripheral nerves, terminal latency and amplitude of muscle potential (M-response).
Contraindications to electroneuromyography
Contraindications to electroneuromyography (ENMG) are not, but do not recommend the use of needle electrodes in patients with HIV infection, which is associated with a high risk of infection of medical personnel during the study.
Interpretation of results of electroneuromyography
With the help of electroneuromyography, a decrease in the speed of the impulse along the nerves and a decrease in the amplitude of the action potential of the nerve are revealed not only with obvious clinical signs of mono- and polyneuropathy, but also in their absence. The decrease in the rate of impulse conduction observed in polyneuritis is used in the differential diagnosis of flaccid paralysis caused by acute neuroinfections ( poliomyelitis or polyneuritis).
In electroneuromyography, it is possible to distinguish the nature of peripheral nerve damage-demyelinating (a marked decrease in the rate of impulse conduction) or axonal (decrease in the amplitude of the M-response).
The extreme expression of the pathology of the peripheral neuromotor apparatus is the absence of an M-response in electroneuromyography.