Rare Spinocerebellar Ataxia Types in Canada: A Case Series and Review of the Literature

Background:There is limited information on rare spinocerebellar ataxia (SCA) variants, particularly in the Canadian population.This study aimed to describe the demographic and clinical features of uncommon SCA subtypes in Canada and compare them withinternational data.Methods:We conducted a case series and literature review of adult patients with rare SCA subtypes, including SCA5,SCA7, SCA12, SCA14, SCA15, SCA28, SCA34, SCA35 and SCA36. Data were collected from medical centers in Ontario, Alberta and Quebecbetween January 2000 and February 2021.Results:We analyzed 25 patients with rare SCA subtypes, with onset ages ranging from birth to67 years. Infantile and juvenile-onset cases were observed in SCA5, SCA7, SCA14 and SCA34. Most patients presented with gait ataxia, with nosignificant differences across groups. Additional common features included saccadic abnormalities (22 of 25), dysarthria (19 of 25) andnystagmus (12 of 22, except in SCA7). Less common findings included dystonia (8 of 25), cognitive impairment (7 of 25), tremor (9 of 25) andparkinsonism (3 of 25).Conclusion:Our study highlights the heterogeneity of rare SCA subtypes in Canada. Ongoing longitudinal analysiswill improve the understanding, management and screening of these disorders.