Chorea is an ongoing random-appearing sequence of one or more discrete involuntary movements or movement fragments.
Movements appear random due to variability in timing, duration, direction, or anatomic location. Each movement may have a distinct start and end point, although these may be difficult to identify since movements are often strung together one immediately following or overlapping with another. Movements may therefore appear to flow randomly from one muscle group to another, and can involve trunk, neck, face, tongue, and extremities.
Chorea is distinguished from dystonia due to the apparently random, unpredictable, and continuously ongoing nature of the movements, compared with the more predictable and stereotyped movements or postures of dystonia. The movements of chorea often appear more rapid than those associated with dystonia. Although chorea may be worsened by movement, attempts at movement, or stress, particular movements are not triggered by voluntary attempts with the same degree of temporal specificity as in dystonia. Therefore chorea does not appear as a temporally linked overflow from a voluntary movement, and it usually does not stop with attempted relaxation. As a result, children with chorea appear to be in constant motion or fidgety. Chorea sometimes results in “parakinesias”, in which children may incorporate the involuntary movement into a more purposeful movement in an attempt to hide the disorder. Unlike dystonia, chorea is not characterized by specific inserted postures, but rather by inserted movements. This distinction may not always be meaningful when a dystonic posture is brief or a choreatic movement involves pulling a limb toward an unwanted posture, but the fundamental distinction is that chorea includes repeated recognizable movements without necessarily any repeated postures.
Chorea is distinguished from athetosis by the ability to identify discrete movements or movement fragments within the ongoing sequence of chorea. The individual movement fragments in chorea are brief and often appear jerky. In contrast, the ongoing movement in athetosis is not composed of discrete movements, and athetosis thus appears to be a sinuous, continuously flowing, ongoing, random movement as opposed to a sequence of randomly selected brief movements.
Chorea is distinguished from tremor by its lack of rhythmicity and predictability. Chorea is distinguished from myoclonus by the fact that in myoclonus all the movements are quick, whereas in chorea only some are. Movements due to myoclonus may appear more stereotyped, as a consistent pattern of muscles is often involved. In some cases chorea and myoclonus may appear very similar when myoclonus is non-synchronous and multifocal. Chorea is distinguished from tics by the fact that chorea is usually not voluntarily suppressible. In addition, tics are more commonly stereotyped in appearance (see below). Chorea is distinguished from tremor associated with ataxia by the fact that abnormal movements in ataxia increase near a target (intention tremor and dysmetria) and improve with stabilization of proximal joints or other interventions that lower the degrees of freedom for movement.
We define ballism as chorea that affects proximal joints such as shoulder or hip. This leads to large-amplitude movements of the limbs, sometimes with a flinging or flailing quality.
Chorea is associated with disorders of the cerebral cortex, basal ganglia, cerebellum, and thalamus. Different causes of chorea often lead to different phenomenology. For instance, streptococcal-associated chorea as seen in Sydenham’s chorea often causes a distal “piano-playing” chorea with movements of the metacarpophalangeal joints of both hands 22, 23
. Lesions in the subthalamic nucleus are associated with chorea and ballism 24
. Encephalitis with diffuse gray-matter destruction is associated with a combination of chorea and myoclonus that affects proximal and distal muscles of the limbs as well as the neck, trunk, and face 25
. Chorea can be caused by other disorders, including hyperthyroidism, anticholinergic toxicity, and genetic and metabolic diseases 25
. Motor impersistence (the inability to maintain a voluntary posture such as tongue protrusion, arm extension, or grip) is a common association 26