28B. Choreas, Huntington disease
Chorea
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. The name comes from the Greek word “to dance”, referring to how the movements have a dance-like appearance.
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 can cause so-called hemichorea, chorea of one side of the body.
Huntington disease
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 or 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 the CAG repeats accumulate, causing the onset to be earlier and the features to be more severe.
Clinical features
The hallmark symptoms of HD are:
- Progressive generalised chorea
- Psychiatric symptoms – emotional incontinence
- Cognitive symptoms – 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 treatment. Multidisciplinary care is important. Tetrabenazine may improve the chorea and antipsychotics may improve the psychiatric symptoms.