Uncontrolled, purposeless motions. Tremor (involuntary, rhythmic muscle movement caused by alternate contraction and relaxation of the muscles) is the most common involuntary movement disorder. Others include chorea (involuntary, purposeless, rapid, jerking movements), athetosis (slow, writhing, continuous movements of the extremities), ballismus (involuntary, irregular, and uncontrollable flinging and jerking movements), and tics (involuntary, repetitive muscle movements, such as blinking or twitching). In many cases, involuntary movements are a symptom of an underlying medical problem, such as Parkinson disease, multiple sclerosis, head injury, or emotional disorders.
Involuntary body movements can arise on their own. These movements might be slow and twisting, fast and erratic, or consistent and repetitive, often seen in specific body parts like the face. Such movements can be symptoms of illnesses, like Huntington’s disease, or side effects of some medications used for mental health conditions.