Spino-cerebellar ataxias (SCA) testing

Last updated: Wednesday, 11, March, 2009

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Item Process
Specimen

10-20 mL blood in EDTA tube.

Method

PCR-based analyses to detect expanded triplet repeat mutations known to cause various autosomal dominant spinocerebellar ataxias (eg, SCA1, Machado-Joseph disease).

Application

Used to detect a triplet repeat mutation in symptomatic or asymptomatic individuals.

Predictive tests in asymptomatic family members should only be arranged after consultation with the pathologist and a clinical genetics service.

Prenatal diagnosis is available.

Interpretation

Expanded triplet repeats in one of the genes account for approximately half of the cases of autosomal dominant SCA.

The identification of the characteristic expansion of the triplet repeat is diagnostic for the presence of a mutation that can cause the particular SCA.

There is some correlation between the specific mutation and the age of onset and severity of the disorder. However, considerable variation exists.

Molecular genetic studies may be indicated in other family members.

Reference

Muller U et al. J Neurol Sci 1994; 124: 119-140.

La Spada AR et al. Ann Neurol 1994; 36: 814-822.