Chorea

Chorea is a hyperkinetic movement disorder consisting of brief, irregular, unpredictable, and flowing involuntary movements that seem to move randomly from one body part to another. The movements are non-rhythmic and may be partly incorporated into purposeful actions, giving an appearance of restlessness or fidgetiness. Chorea has many causes; among the inherited causes, Huntington's disease is the most widely recognised.

Definition

Chorea is an involuntary, hyperkinetic movement disorder characterised by a continuous flow of brief, irregular, non-rhythmic, unpredictable movements that pass randomly between body parts and may be partially blended into voluntary action.

Scope

This entry covers the definition of chorea as a flowing, unpredictable hyperkinesia, the basal-ganglia circuitry implicated in its generation, and its broad range of causes with Huntington's disease as the archetypal inherited example. It is a reference description of the phenomenology and its representative causes and does not provide diagnostic criteria or treatment guidance for any individual.

Core questions

• Are the movements brief, irregular, and unpredictable in their flow between body parts?
• Is the chorea inherited or acquired?
• Does it occur in isolation or with other neurological and systemic features?
• Which basal-ganglia circuits are implicated by the hyperkinetic phenomenology?

Key concepts

• Brief, irregular, flowing movements
• Non-rhythmic hyperkinesia
• Random migration between body parts
• Hereditary versus acquired chorea
• Huntington's disease
• Basal-ganglia disinhibition

Key theories

Indirect-pathway disinhibition in hyperkinesia

In the basal-ganglia model of Albin and colleagues, loss of indirect-pathway output reduces the suppression of unwanted movement, releasing excessive motor activity; chorea is interpreted within this framework as a hyperkinetic state arising when the balance shifts away from movement suppression.

Trinucleotide repeat expansion in Huntington's disease

Huntington's disease, the archetypal hereditary cause of chorea, results from an expanded and unstable CAG trinucleotide repeat in the huntingtin gene, identified by the Huntington's Disease Collaborative Research Group; this discovery linked the inherited chorea to a defined genetic mechanism.

Mechanisms

Chorea is generally attributed to dysfunction within the basal-ganglia motor circuits that normally suppress unwanted movement. In the functional-anatomical model of Albin and colleagues, reduced output of the movement-suppressing indirect pathway disinhibits downstream motor activity, producing a hyperkinetic state consistent with the flowing, unpredictable movements of chorea. In Huntington's disease — the best-characterised inherited cause — an expanded CAG trinucleotide repeat in the huntingtin gene, identified in 1993, leads to degeneration of striatal neurons; Walker and Bates and colleagues describe how this neurodegeneration underlies the chorea and the broader features of the disease.

Clinical relevance

Recognising the brief, irregular, flowing quality of choreic movements distinguishes chorea from other hyperkinesias and orients the wide differential of inherited and acquired causes. This entry describes how chorea is defined and how its representative causes are understood for reference and educational purposes; it does not provide individualised diagnostic or treatment advice.

Epidemiology

Chorea arises from a broad range of inherited and acquired causes, so its frequency is reported for specific aetiologies rather than as a single figure. Huntington's disease is the most widely recognised inherited cause and is reviewed in detail by Walker (2007) and Bates and colleagues (2015), who describe its autosomal dominant inheritance and characteristic course.

Evidence & guidelines

The reference accounts for this topic include the basal-ganglia framework of Albin and colleagues (1989) for the mechanism of hyperkinesia, the identification of the Huntington's disease gene by the Huntington's Disease Collaborative Research Group (MacDonald et al., 1993), and the comprehensive reviews of Huntington's disease by Walker (2007) and Bates and colleagues (2015). No prescriptive guideline is summarised here.

History

Chorea has been described since antiquity, and George Huntington's 1872 account of hereditary chorea defined the disease that bears his name. The field was transformed in 1993 when the Huntington's Disease Collaborative Research Group identified the expanded CAG repeat in the huntingtin gene, converting a clinical description into a defined genetic disorder and anchoring the inherited chorea within molecular neuroscience.

Key figures

• George Huntington
• Roger Albin
• Anne Young
• Francis Walker
• Gillian Bates

Seminal works

• macdonald-1993
• walker-2007
• albin-1989

Frequently asked questions

How does chorea differ from tremor?

Tremor is a rhythmic, roughly regular oscillation, whereas chorea consists of brief, irregular, non-rhythmic movements that flow unpredictably from one body part to another. The irregular, flowing quality is the defining feature that separates chorea from rhythmic hyperkinesias.

Is chorea always due to Huntington's disease?

No. Huntington's disease is the most widely recognised inherited cause of chorea, but chorea has many other inherited and acquired causes. Identifying chorea is the first step; determining its specific cause requires further evaluation.