Ankle clonus. 
Clonus is a series of involuntary, rhythmic, muscular contractions, and relaxations. It may be caused by interruption of the upper motor neuron fibers such as stroke, multiple sclerosis, or by metabolic alterations such as severe hepatic failure or serotonin syndrome. We present a video case of impressive left ankle clonus in a patient with old right middle cerebral artery stroke.