Electromyography patterns of propriospinal myoclonus can be mimicked voluntarily.

In order to investigate the clinical impact of polymyographic evaluation on the diagnosis of propriospinal myoclonus (PSM), we performed electromyography recordings of various truncal muscles in eight healthy volunteers while they mimicked PSM symptoms. Before the experiment, each volunteer learned how to mimic PSM by watching a videotape that showed typical PSM characteristics, i.e., brief symmetric flexion of the trunk. The recorded polymyographic patterns of all volunteers were quite compatible with those found in the previous reports. The present study demonstrates that previously known polymyographic patterns of PSM can be voluntarily mimicked. Additional studies, such as jerk-locked cortical potential, are required to confirm the diagnosis of true PSM.