Myoclonus is a term that refers to brief, involuntary twitching of a muscle or a group of muscles.
It describes a symptom and, generally, is not a diagnosis of a disease. Myoclonic jerks may occur alone or in sequence, in a pattern or without pattern. They may occur infrequently or many times each minute. Most often myoclonus is one of several symptoms in a wide variety of nervous system disorders such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, or Creutzfeldt-Jakob disease. Severe cases of pathologic myoclonus can distort movement and severely limit a person's ability to eat, talk, and walk.