Sonographic imaging of muscle contraction and fasciculations: a correlation with electromyography

Precise quantitation of fasciculations with EMG is difficult because of their random location and discharge frequency in muscle. We studied the clinical value of real-time ultrasound in the study of normal voluntary muscle contraction and in the identification of fasciculations in 22 patients. Sonography effectively imaged fasciculations, demonstrating them in both resting and actively contracting extremity muscles and in less accessible muscles such as the tongue. In two instances ultrasound identified fasciculations not apparent on EMG. Analysis of the video images generated quantitative data on fasciculation duration (averaging 500 msec), size, and location and provided unique insight into the process of normal muscle contraction and motor unit physiology.