Objective: To investigate the temporal dynamics of Scale for the Assessment and Rating of Ataxia (SARA) item scores in patients with spinocerebellar ataxia type 3 (SCA3) and evaluate if clinical and demographic factors are differentially associated with evolution of axial and appendicular ataxia.

Background: Disease severity in SCA3 is commonly defined by the SARA sum score, but little is known about the contributions and progression patterns of single SARA items.

Method: In a prospective, multinational cohort study involving eleven European and two US sites, SARA scores were determined longitudinally in 223 SCA3 patients with a follow-up assessment after one year.

Results: An increase in SARA score from 10 to 20 points was mainly driven by axial and speech items, with a markedly smaller contribution of appendicular items. Finger chase and nose-finger test scores not only showed the lowest variability at baseline but also the least deterioration at follow-up. Compared with the full set of SARA items, omission of both tests would result in lower sample size requirements for therapeutic trials. Sex was associated with change in SARA sum score and appendicular, but not axial, subscore, with a significantly faster progression in men. The average annual progression rate in SARA score was approximately three times higher in individuals with a disease duration over ten years than in those within ten years from onset.

Conclusion: Our data provide evidence for a difference in temporal dynamics between axial and appendicular ataxia in SCA3 patients, which will help inform the design of clinical trials and development of new (etiology-specific) outcome measures.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/differential-temporal-dynamics-of-axial-and-appendicular-ataxia-in-sca3/