Paroxysmal axial spasms of spinal origin.

A 55-year-old man with a 4 1/2-year history of paroxysmal bouts of involuntary large-amplitude flexion jerks of the trunk and a 1-year history of persistent rhythmic small-amplitude movements of the anterior abdominal wall is described. Clinical and electrophysiological evidence suggested that the paroxysmal myoclonus arose in propriospinal systems intrinsic to the spinal cord.