28B. Choreas, Huntington disease

Last updated on June 5, 2021 at 10:55

Chorea

Definition

Chorea refers to involuntary, sudden, irregular, nonrepetitive, arrhythmic movements of limbs or head. This is usually due to increased dopaminergic transmission in the basal ganglia.

Etiology

  • Huntington disease
  • Sydenham chorea (chorea minor)
  • Wilson disease
  • Levodopa
  • Stroke

Huntington disease is the most common cause of chorea. Sydenham chorea is a rare, reversible, postinfectious cause of chorea.

Stroke causes so-called hemichorea, chorea of one side of the body.

Huntington disease

Definition and epidemiology

Huntington disease (HD) is an autosomal dominant neurodegenerative disorder of the central nervous system. It occurs due to a mutation resulting in trinucleotide expansion of CAG repeats on chromosome 4. The manifestations include chorea, dementia and personality changes.

HD begins in the 30s, 40s. The average patient lives 20 years after the diagnosis.

Pathomechanism

Increased number of CAG repeats in the huntingtin (HTT) gene increases risk for Huntington disease. 10 – 35 CAG repeats are physiological, 36 – 39 is high risk for HD, while > 40 invariably causes HD. The higher the number of repeats, the earlier the onset and more severe the disease.

HD has anticipation, which means that which each generation CAG repeats accumulate, causing the onset to be earlier and the features to be more severe.

Clinical features

The hallmark of HD is progressive generalised chorea, psychiatric symptoms, and cognitive symptoms like dementia.

Diagnosis and evaluation

Caudate atrophy on neuroimaging is characteristic. Genetic testing confirms the diagnosis.

It’s important to exclude other causes of extrapyramidal symptoms, like Wilson disease and Parkinson disease. Parkinson disease can be ruled out by giving a trial of levodopa, as levodopa worsens HD but improves PD.

Treatment

There is no cure, only symptomatic and progression-slowing treatment. Multidisciplinary care is important.

Tetrabenazine and antipsychotics may improve the chorea.


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