Occupational hand cramps: professional disorders of motor control.

Occupational cramps affecting the upper extremities have been described for centuries, though only recently is light being shed on their pathogenesis, pathophysiology, and improved strategies for diagnosis and treatment. These dystonias represent localized stereotyped painless movement disorders affecting certain occupational groups in characteristic ways. We retrospectively reviewed 65 patients given a diagnosis of focal dystonias of the upper extremity and describe painless manual incoordination syndromes, insidious in onset, without objective sensory abnormalities, precipitated by certain repetitive actions of the upper extremity. This confirms previous clinical reports. Pathogenesis and pathophysiology are still uncertain, but evidence for altered higher order (basal ganglia and cortical) influences on spinal interneurons leading to ill-directed motor output is hypothesized. Therapeutic options are reviewed stressing the inadequacy of any one mode discovered to date.