title: [Pathophysiology of spasticity].
abstract: Spasticity is characterized by abnormal increase in phasic and velocity-dependent response to muscle stretching, such as exaggerated tendon jerks and clonus. Clasp-knife phenomenon is often observed in the affected muscles. Spasticity is caused by either an excess input to the spinal cord or a disordered descending control of the spinal motor system including the myotatic reflex arc. The increased input due to hyperactivity of γ motor neurons has not been demonstrated in human subjects. The hyperactivity of excitatory interneurons and decreased function of the inhibitory system interneurons in the spinal cord as well as the uncoupling of the inhibitory system from the central system are believed to be involved in spasticity; however, the underlying pathology may differ based on the lesion site and the time elapsed since loss of reciprocal inhibition.
authors.affiliation: Medical Corporation Taiheikai, Coral Clinic.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kagamihara
mesh_terms: D006801:Humans; D009069:Movement Disorders / Q000503:physiopathology; D009128:Muscle Spasticity / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission