A small fraction of strokes do the opposite. The patient's arm and leg on one side begin moving on their own, in irregular, flowing, unpredictable motions that observers often describe as dance-like. The person is fully awake, fully aware, and cannot stop it. The condition is called hemichorea, and when the movements become wide and forceful, it is called hemiballismus.
It occurs in fewer than 1 percent of strokes, with published estimates ranging from 0.4 to 0.54 percent. It is rare enough that it gets mistaken for intoxication, a seizure, or a psychiatric problem, and rare enough that a normal first scan can send the patient home.
