Clonus (from the Greek for "violent, confuse motion") is a series of involuntary muscular contractions due to sudden stretching of the muscle. Clonus is a sign of certain neurological conditions, and is particularly associated with upper motor neuron lesions such as amyotrophic lateral sclerosis (ALS), stroke, multiple sclerosis, spinal cord damage and hepatic encephalopathy. Magnesium Sulphate overdose is also know to cause clonus. Unlike the small, spontaneous twitching known as fasciculations (usually caused by lower motor neuron pathology), clonus causes large motions that are usually initiated by a reflex.