Needle Electromyography |
Dae-Seong Kim |
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Copyright © 1999 The Korean Society of Clinical Neurophysiology |
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium,
provided the original work is properly cited. |
ABSTRACT |
The needle EMG study became a routine diagnostic work-up for various neuromuscular disorders including myopathies, neuromuscular junction disease, motor neuron diseases and other lower motor neuron disorders. The development of the computerized modern EMG machines also enabled accurate and detailed analysis of the motor unit physiology available in most of the electrophysiology laboratory. The main purpose of this article is to illustrate the technique and interpretation of the needle EMG finding. In the first part of the article, the basic anatomy and physiology of the motor unit, technique of the needle EMG examination and motor unit potential(MUP) analysis is reviewed. A MUP, which can be identified with conventional needle EMG study, is composed of action potentials of individual muscle fibers belonging to the same motor unit, and thus, its morphological changes reflect physiological and pathological alterations of the motor unit. In the second part of the article, single fiber electromyography (SFEMG) technique is briefly reviewed. As the action potentials of individual muscle fibers cannot be recorded with the conventional needle EMG technique, this technique requires specialized needle electrode and higher filter setting for the selective recording of the single fiber action potential(SFAP), and lower sweep velocity for the better separation of different SFAPs. Although SFEMG technique can be used for the estimation of the motor unit size and territory, it is practically most useful for the study of the neuromuscular transmission. In conclusion, the thorough understanding of the motor unit physiology and MUP electrophysiology is essential for the correct application and interpretation of the needle EMG. |
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