Huntington disease
Description
- Autosomal dominant neurodegenerative disease - chorea + cognitive decline + neuropsychiatric disturbance
- Progressive striatal (caudate > putamen) medium spiny neurone loss
- The clinical triad is motor, cognitive and psychiatric - and the psychiatric features usually come first
Motor phenotype
- Chorea - brief, non-stereotyped, flowing, unpredictable involuntary movements; incorporated into semi-purposeful movement (parakinesia)
- Motor impersistence - inability to sustain tongue protrusion or grip ("milkmaid grip")
- Saccadic abnormalities - slow, hypometric saccades with head thrusts; impaired initiation (often the earliest motor sign)
- Later: dystonia, bradykinesia, rigidity replace chorea; dysarthria, dysphagia, gait ataxia
- Westphal variant - juvenile-onset (<20 yrs), akinetic-rigid rather than choreiform, with seizures, cerebellar signs and rapid decline; almost always paternally transmitted
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