NORMAL NEEDLE ELECTROMYOGRAPHIC INSERTIONAL ACTIVITY MORPHOLOGY - A CLINICAL AND SIMULATION STUDY

Needle electromyographic insertional activity waveform morphology, and mechanisms of generation, have received little attention. This study analyzes the individual component waveforms that contribute to the bur st of electrical activity known as insertional activity. One hundred m onopolar needle insertions were slowly performed and high speed record ed to allow better separation of the contributing individual component waveforms. Analysis of the many waveforms recorded demonstrates sever al classes of potentials. Ail of these could be reconstructed by the s ummation of two basic or elementary waveform patterns: a biphasic init ially negative spike with or without a ''prepotential'' similar to an end-plate spike, and the biphasic initially positive spike with a slow ly declining negative phase, similar to a positive sharp wave, though shorter in duration. The relationship between these elementary wavefor ms and their hypothesized generator sources is discussed. (C) 1998 Joh n Wiley & Sons, Inc.