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Spinocerebellar ataxia

Last updated: December 3, 2019

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Spinocerebellar ataxia (SCA) refers to a group of progressive neurodegenerative diseases of genetic origin. Currently, more than 30 types have been identified, most of which are autosomal dominant, such as SCA3. Trinucleotide repeat expansions in a disease-associated protein (e.g., CAG repeats in ataxin-1) are commonly the underlying genetic anomaly. Patients usually present between the ages of 30–50 with slowly progressive symptoms of cerebellar ataxia, including incoordination of gait, hand, speech, and eye movements. The diagnosis is reached on the basis of family history and neurological examination, but neuroimaging and molecular genetic testing help identify the specific cause and type of SCA. To date, there is no effective treatment. Therapy is directed towards alleviating symptoms. The prognosis depends on individual genetic properties, but most patients progressively develop severe, irreversible disability, while retaining full mental capacity, within 15 years of symptom onset.

  • Prevalence: ∼ 1–4/100,000
  • Age of onset: 30–55 years
  • Most common type (worldwide): SCA3

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

References:[3][4][5]

Type of ADCA Important SCA types Clinical features
Type I SCA1­–SCA4, SCA8, SCA10, SCA12–SCA23, SCA25, SCA27, SCA28
Type II SCA7
  • Ataxia
  • Pigmentary maculopathy and subsequent blindness
Type III SCA5, SCA6, SCA11, SCA26, SCA29, SCA30, and SCA31
  • Only ataxia; usually late onset

References:[4]

The diagnosis is based on family history and neurological examination. Further tests help identify the specific cause and type of SCA.

References:[5]

There is currently no effective causative therapy available and therefore treatment focuses on symptom management.

  • Canes, braces, and wheelchairs for gait ataxia
  • Use of special devices to assist with fine movements (e.g., handwriting, buttoning clothes, use of eating utensils)
  • Speech therapy for dysarthria and severe speech deficits

References:[1][4]

  • Variable for each SCA type, but generally poor
  1. Revilla FJ. Ataxia with Identified Genetic and Biochemical Defects. Ataxia with Identified Genetic and Biochemical Defects. New York, NY: WebMD. http://emedicine.medscape.com/article/1153370-overview. Updated: October 12, 2015. Accessed: April 3, 2017.
  2. Hereditary Ataxia Overview. https://www.ncbi.nlm.nih.gov/books/NBK1138/. Updated: November 3, 2016. Accessed: April 3, 2017.
  3. The wide spectrum of spinocerebellar ataxias (SCAs). https://link.springer.com/article/10.1080%2F14734220510007914. Updated: March 1, 2005. Accessed: April 3, 2017.
  4. Spinocerebellar Ataxia. https://omim.org/entry/302500. Updated: January 1, 2017. Accessed: April 3, 2017.
  5. Opal P, Zoghbi HY. The spinocerebellar ataxias. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/the-spinocerebellar-ataxias?source=search_result&search=spinocerebellar%20ataxia&selectedTitle=1~30.Last updated: January 6, 2017. Accessed: April 3, 2017.