SCA Functional Index: a useful compound performance measure for spinocerebellar ataxia.

OBJECTIVE: To evaluate the usefulness of functional measures in patients with spinocerebellar ataxia (SCA). METHODS: We assessed three functional measures-8 m walking time (8MW), 9-hole peg test (9HPT), and PATA repetition rate-in 412 patients with autosomal dominant SCA (genotypes 1, 2, 3, and 6) in a multicenter trial. RESULTS: While PATA rate was normally distributed (mean/median 21.7/20.5 per 10 s), the performance times for 8MW (mean/median 10.8/7.5 s) or 9HPT (mean/median 47.2/35.0 s in dominant, 52.2/37.9 s in nondominant hand) were markedly skewed. Possible learning effects were small and likely clinically irrelevant. A composite functional index (SCAFI) was formed after appropriate transformation of subtest results. The Z-scores of each subtest correlated well with the Scale for the Assessment and Rating of Ataxia (SARA), the Unified Huntington's disease Rating Scale functional assessment, and disease duration. Correlations for SCAFI with each of these parameters were stronger (Pearson r = -0.441 to -0.869) than for each subtest alone. Furthermore, SCAFI showed a linear decline over the whole range of disease severity, while 9HPT and 8MW had floor effects with respect to SARA. Analysis of possible confounders showed no effect of genotype or study site and only minor effects of age for 8MW. CONCLUSION: The proposed functional measures and their composite SCAFI have favorable properties to assess patients with spinocerebellar ataxia.

Spinocerebellar ataxia types 1, 2, 3, and 6: disease severity and nonataxia symptoms.

OBJECTIVE: To identify factors that determine disease severity and clinical phenotype of the most common spinocerebellar ataxias (SCAs), we studied 526 patients with SCA1, SCA2, SCA3. or SCA6. METHODS: To measure the severity of ataxia we used the Scale for the Assessment and Rating of Ataxia (SARA). In addition, nonataxia symptoms were assessed with the Inventory of Non-Ataxia Symptoms (INAS). The INAS count denotes the number of nonataxia symptoms in each patient. RESULTS: An analysis of covariance with SARA score as dependent variable and repeat lengths of the expanded and normal allele, age at onset, and disease duration as independent variables led to multivariate models that explained 60.4% of the SARA score variance in SCA1, 45.4% in SCA2, 46.8% in SCA3, and 33.7% in SCA6. In SCA1, SCA2, and SCA3, SARA was mainly determined by repeat length of the expanded allele, age at onset, and disease duration. The only factors determining the SARA score in SCA6 were age at onset and disease duration. The INAS count was 5.0 +/- 2.3 in SCA1, 4.6 +/- 2.2 in SCA2, 5.2 +/- 2.5 in SCA3, and 2.0 +/- 1.7 in SCA6. In SCA1, SCA2, and SCA3, SARA score and disease duration were the strongest predictors of the INAS count. In SCA6, only age at onset and disease duration had an effect on the INAS count. CONCLUSIONS: Our study suggests that spinocerebellar ataxia (SCA) 1, SCA2, and SCA3 share a number of common biologic properties, whereas SCA6 is distinct in that its phenotype is more determined by age than by disease-related factors.