Needle EMG involves penetration of muscle with an electrode and recording electrical potentials at rest and during variable degrees of voluntary muscle contraction. Conventional needle EMG techniques record potentials generated by the near simultaneous depolarization of many muscle fibers in a single motor unit, a motor unit action potential (MUAP). MUAP’s recorded during needle EMG has several characteristics that can be described both qualitatively and quantitatively. The general term of ‘qualitatively or subjective’ needle EMG define a passive process of watching the screen with minimal to no interference from the operator. MUAP assessments are made on general impression (particularly amplitude) and the only movement is when the needle electrode is displaced to a different recording site. At the other extreme is computer-assisted MUAP quantitative analysis where a great deal of operator input is required. This approach requires training, takes time, and is not indicated in most studies. There is a middle ground, however, which we have called ‘objective-interactive’ needle EMG. This disciplines the EDX consultant to truly monitor the signals being acquired on the screen and to make ongoing semi-quantitative or ‘objective’ assessments of amplitude, duration, complexity, area, and stability. But these assessments are usually not achieved with a single instrumentation setting. This workshop will focus on motor unit action potential (MUAP) quantitation. It is assumed that the participant becomes familiar with the basic, routine needle electromyography (EMG) examination. The goal of this workshop is to enhance his/her ability to maximize the data they acquire in routine needle EMG. This will be achieved in 4 general steps: review of basic MUAP features, demonstration of acquisition techniques, analysis of the MUAPs that are acquired and interference EMG pattern analysis.
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