Surface EMG and myosonography in the detection of fasciculations: a comparative study

Surface electromyography (EMG) and muscle sonography both facilitate the detection of fasciculations. This study was conducted to evaluate the prevalence of fasciculations in 10 lower extremity muscles in 58 subjects 47 +/- 18 years of age without and 54 patients 52 +/- 15 years of age with various neuromuscular diseases (3 with inflammatory myopathy, 15 with lower motor neuron disease, 22 with acquired and 11 with hereditary motor and sensory neuropathy (HMSN), and 3 with adrenomyeloneuropathy). When each muscle was screened by means of myosonography for 10 seconds, fasciculations were found in up to 8 muscles in 11 control subjects (19%) and in up to 10 muscles in 41 patients (76%). Within the same recording period surface EMG revealed fasciculations in 5 control subjects (9%) and 30 patients (56%), whereas during a recording time of 20 minutes fasciculations were detected in 55 (95%) control subjects and all patients. An amplitude of 400 microV proved to be the optimum cutoff between fasciculations for healthy subjects and patients with neuromuscular disease (accuracy, 74%). Myosonography allowed differentiation of both groups with an accuracy of 79%. Surface EMG was more liable to artifacts than myosonography. The average interval between subsequent fasciculations cannot be used to differentiate patients with acquired and hereditary polyneuropathy and with lower motor neuron disease. Long-term surface EMG recording indicates fasciculations to occur in almost all patients with neuromuscular disease and the vast majority of healthy subjects. Muscle ultrasonography was more convenient and reliable than surface EMG in differentiating patients and healthy subjects.