Ultrasound myography: application in nerve conduction velocity assessment and muscle cooling

A new application of ultrasound for studying muscle twitch induced by electrical stimulation is described and some preliminary results are presented. The method, called "ultrasound myography" (UMG), uses Doppler ultrasound to measure muscle movement velocity. The Doppler signals were measured simultaneously with the electromyography (EMG) signals from the thenar muscle of a healthy subject. Averaged EMG and full-wave rectified UMG responses to repeated electrical stimuli were measured after cooling of the hand and adaptation to room temperature. Latency times over the wrist of cold hands adapted to a surrounding temperature of 8 degrees C were 4.5 ms and 16.9 ms for the EMG and averaged rectified UMG responses, respectively. Both latency times decreased considerably after 1 h adaptation to a room temperature of 21 degrees C:20% for the EMG response and 35% for the UMG response. The conduction velocities of the median nerve in the forearm determined by both methods yield comparable results. The results of both methods are discussed. It is concluded that UMG possibly offers a new method in clinical practice for the assessment of nerve conduction velocities in the forearm, and basically is a new simple-to-use technique for noninvasive analysis of deep biomechanical processes.