brain, spinal cord, and nerve disorders
Myoclonus
Symptoms of Myoclonus
Myoclonus can be mild or severe. Muscles may jerk quickly or slowly, rhythmically or not. Myoclonus may occur once in a while or frequently. It may occur spontaneously or be triggered by a stimulus, such as a sudden noise, light, or a movement. For example, reaching for an object or taking a step may trigger jerks that disrupt the movement. Myoclonus that occurs when people are suddenly startled (startle myoclonus) may be an early symptom of Creutzfeldt-Jakob Disease (CJD) (a rare disorder that causes the brain to degenerate). If myoclonus is due to a metabolic disorder, the face, upper arms, and thighs are usually affected. If it persists, it may affect muscles throughout the body, sometimes leading to seizures. Some types of myoclonus—such as the quick twitches of muscles as a person falls asleep—are normal. 