Educational scope notice: This is a study note for medical students, not medical advice, diagnosis, or treatment guidance. Clinical management should follow local protocols and current guidelines.
Chorea, athetosis, and ballismus form one clinical continuum of basal ganglia dysfunction, distinguished by speed, amplitude, and distribution rather than by separate disease biology. A useful shorthand is that athetosis is chorea slowed down and ballismus is chorea amplified: flowing irregular movements at the center, slow writhing distally at one end, violent proximal flinging at the other. The general assessment framework sits in /notes/neurology/hyperkinetic-movement-disorders-classification/.
Chorea
Chorea, from the Greek word for dance, consists of involuntary, irregular, purposeless movements that flow unpredictably between body parts. Individual fragments are abrupt, brief, and jerky; the overall picture is constantly changing, so the patient is never still yet never repeats the same movement twice.
Typical behavior includes presence at rest with marked worsening during activity, tension, and self-consciousness; disappearance in sleep; and a highly variable distribution across distal limbs, face (grimacing, lip pursing, tongue protrusion), trunk, and occasionally the vocal tract.
Two bedside signs deserve attention. Outstretched hands show a piano-playing restlessness, and voluntary action with one limb worsens chorea elsewhere (motor overflow). Patients also fold choreic fragments into gestures, the parakinesia described in the classification note, which makes early chorea look like fidgeting until the ever-changing, goal-less pattern gives it away. Generalized chorea keeps the patient in near-constant motion with high energy expenditure.
The standard circuit model is striatal disinhibition: loss of inhibitory striatal output releases thalamic drive to motor cortex. The genetic prototype is Huntington disease, caused by a CAG trinucleotide repeat expansion in the HTT gene on chromosome 4 and inherited in an autosomal dominant pattern, with selective degeneration of striatal GABAergic neurons. Behavioral changes such as depression, apathy, irritability, or suicidal thinking often precede motor onset by years, and late disease characteristically transitions from chorea into rigidity and bradykinesia as degeneration advances.
Causes of chorea beyond Huntington disease
| Cause | Distinguishing points |
|---|---|
| Sydenham chorea | Post-streptococcal autoimmune disorder of children and adolescents; self-limiting over weeks to months; a major Jones criterion for acute rheumatic fever |
| Chorea gravidarum | Onset during pregnancy, usually reversible after delivery; more likely with prior Sydenham chorea |
| Drug-induced chorea | Levodopa excess in Parkinson disease (peak-dose dyskinesia), dopamine-blocking agents including antipsychotics and metoclopramide (tardive oro-facial patterns), lithium, stimulants such as cocaine and amphetamines, and estrogens |
| Vascular chorea | Acute hemichorea contralateral to a striatal stroke lesion |
| Metabolic chorea | Thyroid dysfunction, glycemic extremes, polycythemia |
| Autoimmune chorea | Systemic lupus erythematosus and antiphospholipid syndrome; the antibody mechanism against striatal targets remains unestablished |
| Paraneoplastic chorea | Remote effect of systemic carcinoma, often bilateral |
| Neuroacanthocytosis | Chorea with acanthocytes on the peripheral blood smear |
Metoclopramide deserves explicit mention because it is easily overlooked: as a dopamine D2 receptor blocker it can produce the same tardive dyskinesia and akathisia syndromes as antipsychotics, so orofacial chorea in a patient who never took antipsychotics still calls for an antiemetic history.
Athetosis
Athetosis is slower, more sustained, and writhing, with a snake-like flow through flexion, extension, pronation, and supination that favors the distal limbs, especially fingers, hands, and toes. It is often unilateral, overflow intensifies it when another part moves voluntarily, coordination is severely impaired, and it generally disappears in sleep. Overlap with chorea is so frequent that choreoathetosis is routine clinical language.
Causes divide into congenital basal ganglia injury from perinatal anoxia or birth injury (bilateral disease with marble-like basal ganglia changes called status marmoratus is termed double athetosis), acquired lesions such as trauma or vascular injury, and pseudoathetosis: similar writhing from lost position sense (parietal lesions, tabes dorsalis, severe neuropathy) that worsens with eyes closed and carries no increased tone.
Ballismus and hemiballismus
Ballismus is the violent end of the spectrum: large-amplitude flinging of the proximal limbs with enough force to injure patient or bystander. Unilateral disease (hemiballismus, contralateral to the lesion) is the classic form; bilateral ballismus sparing face and trunk is rare. Onset is typically abrupt enough that the patient can date it, and many cases improve substantially over days to weeks, sometimes resolving. Persistent or dangerous cases are managed by specialists, with dopamine-depleting agents and antipsychotics among the options.
Hemiballismus is classically associated with a contralateral subthalamic lesion, but lesions elsewhere in basal ganglia circuitry also occur. Clinically, ballismus shares chorea’s irregularity at far greater amplitude, and management principles overlap rather than forming a separate doctrine.
The spectrum at a glance
| Feature | Chorea | Athetosis | Ballismus |
|---|---|---|---|
| Speed | Rapid | Slow | Very rapid and violent |
| Amplitude | Small to moderate | Small, distal | Large, proximal |
| Distribution | Distal more than proximal, plus face and trunk | Fingers, hands, toes | Shoulder and hip girdles |
| Rhythm | Irregular and unpredictable | Writhing and flowing | Irregular flinging |
| Substrate | Caudate and putamen | Basal ganglia, often developmental injury | Subthalamic nucleus region |
| Prototype | Huntington disease | Cerebral palsy with status marmoratus | Lacunar stroke |
Evidence anchors
- National Institute of Neurological Disorders and Stroke. Huntington’s Disease: https://www.ninds.nih.gov/health-information/disorders/huntingtons-disease
- MedlinePlus Genetics. Huntington’s disease (CAG repeat, autosomal dominant inheritance): https://medlineplus.gov/genetics/condition/huntingtons-disease/
- Centers for Disease Control and Prevention. Diagnosing Acute Rheumatic Fever (Jones criteria): https://www.cdc.gov/group-a-strep/hcp/clinical-guidance/diagnosing-acute-rheumatic-fever.html
- Merck Manual Professional Edition. Chorea, Athetosis, and Hemiballismus: https://www.merckmanuals.com/professional/neurologic-disorders/movement-and-cerebellar-disorders/chorea-athetosis-and-hemiballismus
- U.S. Food and Drug Administration. Metoclopramide product label (tardive dyskinesia boxed warning): https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/022246s009lbl.pdf