Anatomy of self-injurious, stereotypic, and aggressive movements: evidence for involuntary explanation.

Self-injurious movements, common in persons diagnosed with Tourette syndrome, or mental retardation, are typically difficult to eliminate. The author considers the possibility that certain self-injurious movements are involuntary phenomena. An anatomical analysis of high-frequency movements in a patient with severe head slapping is presented by tracing the muscles and nerves involved. The median nerve innervates muscles that bring the hand/arm to the head and also muscles that control this patient's other frequent movements, viz., pill-rolling, thumb-gouging, wrist-flapping, and pinching the neck or cheek. Other patients underwent similar investigation: one who headbangs, one who hits out repetitively, and one with non-injurious stereotypic movements. An anatomical explanation suggests that certain self-injurious, aggressive, and stereotypic movements are involuntary muscle contractions that reflect abnormal innervation along specific nerves.