This patient has prominent fasciculations of the left thigh, manifested as irregular, wormlike movement.
About fasciculations
Fasciculations are visible, involuntary contractions of groups of muscle fibers. When pathologic, such as in amyotrophic lateral sclerosis, fasciculations are associated with atrophy and weakness. The syndrome of benign fasciculations is not associated with atrophy or weakness.
Localization
Fasciculations arise from the spontaneous discharge of a motor unit. A motor unit consists of an anterior horn cell and all the muscle fibers it innervates.