Spinocerebellar Ataxia

With an estimated 150’000 people affected in the United States spinocerebellar ataxia (SCA) is the most common, hereditary, progressive degenerative disorder, which is subdivided into several different types based on the affected gene. SCA 1, 2, 3, 6, 7 and 17 are caused by the expansion of the polyglutamine (polyQ)-coding CAG-triplet in the respective gene. 

General Symptoms

General symptoms of SCA include postural instability, uncoordinated stance and gait, neuropathy, dysmetria, dysarthria, dysphagia and dysdiadochokinesia.

Ocular motor disorders are also  common in SCA, it is however not possible to distinguish between different types of SCA based on eye movement examinations, even though they can point to a certain type in some cases. 

Diagnosis

Neurological examination including an eye movement examination is vital for the diagnosis of SCA. Molecular genetic testing to detect an abnormal CAG extension in one of ATXN genes used to rule out any other causes for the neurological findings.

Observable ocular motor disorders

  • Horizontal supranuclear gaze palsy
  • Slowing of horizontal saccades (SCA7)

References

Strupp M, et al. Central ocular motor disorders, including gaze palsy and nystagmus. J Neurol, 2014, 261(2):542-558. PubMed

Seidel K, et al. Brain pathology of spinocerebellar ataxias. Acta Neuropathol., 2012, 124(1):1-21. PubMed

Lastres-Becker I, et al. Spinocerebellar ataxia 2 (SCA2). Cerebellum, 2008 7(2):115-124. PubMed