myoclonus

Myoclonus is a brief, involuntary, irregular (lacking rhythm) twitching (different from clonus, which is rhythmic/ regular) of a muscle or a group of muscles. It describes a medical sign and, generally, is not a diagnosis of a disease. These myoclonic twitches, jerks, or seizures are usually caused by sudden muscle contractions (positive myoclonus) or brief lapses of contraction (negative myoclonus). The most common circumstance under which they occur is while falling asleep (hypnic jerk). Myoclonic ...