The National Institute of Health reports that<unk>  has a prevalence of approximately<unk>  or 2 per<unk> 00,000 however a review of literature has shown that these estimates vary significantly from study to study and can be less than<unk>  per<unk> 00,000 or as high as 6 per<unk> 00,000. Among all<unk> s of SCA,<unk>  is among the most common and the portion accounted for by<unk>  varies between geographic regions, with percentages as high as 40% of all<unk> iagnoses in populations in Russia and South Africa being<unk> . In the United States<unk>  accounts for 6% of<unk> iagnoses. Overall,<unk>  accounts for 6-27% of all cases dominant<unk> s. Because of its late onset, often appearing after reproductive age,<unk>  exerts low selection intensity, ranking about 0.19 on the Crow's index, but intensity may vary with time within a population or family, as anticipation increases the number of CAG repeats. One implication of this is that<unk>  is unlikely to disappear from a population by natural selection alone. Prevalence of each<unk>  of<unk> aries with geographic region and ethnicity, possibly because of founder effects and historic migration patterns. High prevalence regions include central Poland, where 68% of autosomal dominant cerebellar disorders are<unk> ; communities in Tamil Nadu, where up to 7.2% of the population has<unk>  in some small villages; the Tohoku region on the northern portion of Honshu Island, with 24.8% of cases being<unk> ; and among Yakut populations in eastern Siberia, with a prevalence 46 per<unk> 00,000 in rural populations.
Spinocerebellar ataxia type 1
Spinocerebellar ataxia type 6
Spinocerebellar ataxia type-13
Autosomal recessive cerebellar ataxia type 1
Metachromatic leukodystrophy
Benign hereditary chorea
Stratton Parker syndrome
Friedreich's ataxia