Athetosis causes slow movements of your arms, legs, hands, feet, neck, tongue, face, or torso. These movements are often described as "writhing" or "worm-like." They are often continuous and you can't control them. In fact, athetosis usually gets worse when you try to control it.
In many cases, athetosis is caused by birth complications. It can also be a symptom of another neurological condition, usually damage to the basal ganglia, which is part of your brain.