The purpose of the present study was to elucidate the relative frequencies of fasciculations assessed by sonography in a large number of muscles in patients with amyotrophic lateral sclerosis (ALS). The patients diagnosed as having ALS were retrospectively assessed by muscle sonography. The frequencies of having fasciculations were compared among the 15 muscles and the subtypes according to the initially affected body region. Overall, approximately half of the muscles had fasciculations (48.8%), in the average of 11.4 muscles per patient. The frequency of fasciculations tended to be lower in the patients with longer disease durations upon testing. Biceps brachii had the highest frequency, followed by extensor digitorum communis, whereas sternocleidomastoid and rectus abdominis had the lowest frequencies. The frequencies of fasciculations were similar among the clinical subtypes. In conclusion, in patients with ALS, fasciculations were detected most frequently in proximal arm muscles by sonography, whereas truncal muscles had lower frequencies. Fasciculations tended to be less evident in the advanced disease stage, possibly reflecting muscle degeneration. Appropriate selection of muscles to observe fasciculations is important for diagnosis of ALS
