Objective: As gene-based therapies may soon arise for patients with spinocerebellar ataxia (SCA), there is a critical need to identify biomarkers of disease progression with effect sizes greater than clinical scores, enabling trials with smaller sample sizes. Methods: We enrolled a unique cohort of patients with SCA1 (n = 15), SCA2 (n = 12), SCA3 (n = 20) and SCA7 (n = 10) and 24 healthy controls of similar age, sex and body mass index. We collected longitudinal clinical and imaging data at baseline and follow-up (mean interval of 24 months). We performed both manual and automated volumetric analyses. Diffusion tensor imaging (DTI) and a novel tractography method, called fixel-based analysis (FBA), were assessed at follow-up. Effect sizes were calculated for clinical scores and imaging parameters. Results: Clinical scores worsened as atrophy increased over time (p < 0.05). However, atrophy of cerebellum and pons showed very large effect sizes (>1.2) compared to clinical scores (<0.8). FBA, applied for the first time to SCA, was sensitive to microstructural cross-sectional differences that were not captured by conventional DTI metrics, especially in the less studied SCA7 group. FBA also showed larger effect sizes than DTI metrics. Conclusion: This study showed that volumetry outperformed clinical scores to measure disease progression in SCA1, SCA2, SCA3 and SCA7. Therefore, we advocate the use of volumetric biomarkers in therapeutic trials of autosomal dominant ataxias. In addition, FBA showed larger effect size than DTI to detect cross-sectional microstructural alterations in patients relative to controls.
Bibliographical noteFunding Information:
This study was sponsored by the Assistance-Publique des Hôpitaux de Paris and supported by a grant from the French Ministry of Health – “ Programme Hospitalier de Recherche Clinique ” [PHRC BIOSCA - ID RCB: 2010-A01324-35 , AOM10094 , NCT01470729 ] and the program “ Investissements d'avenir ” [ ANR-10-IAIHU-06 ]. The Center for Magnetic Resonance Research is funded by the National Institute of Biomedical Imaging and Bioengineering (NIBIB) [ P41 EB015894 ] and the Institutional Center Cores for Advanced Neuroimaging award [ P30 NS076408 ].
© 2018 The Authors
- Apparent fiber density
- Diffusion imaging.
- Fixel analysis
- Imaging biomarkers
- Spinocerebellar ataxia