Clonus

Clonus is a set of involuntary and rhythmic muscular contractions and relaxations. Clonus is a sign of certain neurological conditions, particularly associated with upper motor neuron lesions involving descending motor pathways and, in many cases, is accompanied by spasticity. Unlike small spontaneous twitches known as fasciculations, clonus causes large motions that are usually initiated by a reflex. Studies have shown clonus beat frequency to range from three to eight Hz on average and may last a few seconds to several minutes depending on the patient's condition.