Propriospinal myoclonus: report of a case

Propriospinal myoclonus is an unusual movement disorder. Here we reported a patient with electrophysiological data. The 32-year-old man had spontaneous, intermittent and brief jerks over the trunk, hip and lower limbs muscles for 4 years. The jerks were not sensitive to external stimuli and usually exacerbated whenever the patient felt relaxed, particularly preceding the onset of sleep. Electromyographic (EMG) recordings showed a long duration in each EMG burst (over 200 milliseconds) with a slow propagating pattern initiating from the rectus abdominis muscles. There was no time-locked cortical potential before the spontaneous jerks; however, we found movement-related cortical potential, while the patient was requested to mimic the jerks voluntarily. These results provided evidence to demonstrate that the jerks were not cortical origin and supported the diagnosis of propriospinal myoclonus. A comprehensive clinical evaluation including distinctive electrophysiological findings is important for the diagnosis.