Chorea (or choreia, occasionally) is an abnormal involuntary movement disorder, one of a group of neurological disorders called dyskinesias. The term chorea is derived from the Greek word χορεία (=dance; see choreia), as the quick movements of the feet or hands are comparable to dancing.
The term hemichorea refers to chorea of one side of the body, such as chorea of one arm but not both (comparable to hemiballismus).
Chorea is characterized by brief, semi-directed, irregular movements that are not repetitive or rhythmic, but appear to flow from one muscle to the next.
These 'dance-like' movements of chorea often occur with athetosis, which adds twisting and writhing movements. Walking may become difficult, and include odd postures and leg movements.
Unlike ataxia, which affects the quality of voluntary movements, or parkinsonism, which is a hindrance of voluntary movements, the movements of chorea and ballism occur on their own, without conscious effort. Thus, chorea is said to be a hyperkinetic movement disorder.