Spinocerebellar Ataxia Type 2

Spinocerebellar Ataxia Type 2

Spinocerebellar ataxia type 2 (SCA2) is a subtype of type I autosomal dominant cerebellar ataxia (ADCA type I; see this term) characterized by truncal ataxia, dysarthria, slowed saccades and less commonly ophthalmoparesis and chorea.

Synonyms

SCA2

Incidence

How common is Spinocerebellar Ataxia Type 2?

  • Prevalence is estimated to be 1-2 in 100,000 with significant geographical and ethnic variations: the highest prevalence has been found in the Azores (Flores Island (1/239)), intermediate prevalence rates in Portugal, Germany, the Netherlands, China and Japan, and lower prevalence in North America, Australia and India.
  • Accurate estimates of prevalence are not available. However, SCA3 is the most common form of ADCA1 in most genetically characterized populations and accounts for up to 72 % of families with ataxia.
  • Based on an English language literature review about 600 cases have been published.

Inheritance

Autosomal dominant 

Age of Onset

All ages

What causes SCA2?

The disease is caused by mutations in the ataxin 2 gene ATXN2 (12q23-q24.1). The normal CAG repeat length is 15-24; repeats 35 and longer are associated with the clinical manifestations of SCA2.

What are the symptoms of Spinocerebellar Ataxia Type 2?

  • SCA2 presents in the 3rd or 4th decade (average age = 30 years; age range = 2-65 years). Parkinsonism is also a less common but well-documented manifestation. There is no distinct clinical feature that reliably distinguishes SCA2 from SCA1 although tremor and autonomic dysfunction are more common in SCA2. Disease course is similar in both SCA1 and SCA2.

Very Common Symptoms

  • Abnormality of the substantia nigra
  • Progressive cerebellar ataxia

Common Symptoms

  • Abnormal cell morphology
  • Abnormality of the spinocerebellar tracts
  • Cerebellar Purkinje layer atrophy
  • Chorea
  • Dementia
  • Dysarthria
  • Dystonia
  • Fasciculations
  • Gait ataxia
  • Generalized hypotonia
  • Hyporeflexia
  • Kinetic tremor
  • Muscle spasm
  • Nystagmus
  • Olivopontocerebellar hypoplasia
  • Postural tremor
  • Slow saccadic eye movements
  • Spinal cord posterior columns myelin loss
  • Supranuclear ophthalmoplegia 

Occasional Symptoms

  • Abnormal cortical gyration
  • Cerebral cortical atrophy
  • Cerebral white matter atrophy
  • Hyperactive deep tendon reflexes
  • Ophthalmoparesis
  • Parkinsonism

What is the prognosis?

Prognosis is relatively good in most cases. Cases with disease duration of longer than 20 years have been described. However, in some cases, especially those with younger age of symptomatic disease onset (under 20 years), progression may be rapid.

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