Functional impairment in patients with myotonic dystrophy type 1 can be assessed by an ataxia rating scale (SARA)

DiPaolo, G., Jimenez-Moreno, C., Nikolenko, N., Atalaia, A., Monckton, D. G. , Guglieri, M. and Lochmüller, H. (2017) Functional impairment in patients with myotonic dystrophy type 1 can be assessed by an ataxia rating scale (SARA). Journal of Neurology, 264(4), pp. 701-708. (doi: 10.1007/s00415-017-8399-x) (PMID:28168524)

Abstract

Myotonic dystrophy type 1 (DM1) is not characterised by ataxia per se; however, DM1 and ataxia patients show similar disturbances in movement coordination often experiencing walking and balance difficulties, although caused by different underlying pathologies. This study aims to investigate the use of a scale previously described for the assessment and rating of ataxia (SARA) with the hypothesis that it could have utility in DM1 patients as a measure of disease severity and risk of falling. Data from 54 DM1 patients were pulled from the PHENO-DM1 natural history study for analysis. Mean SARA score in the DM1 population was 5.45 relative to the maximum score of eight. A flooring effect (score 0) was observed in mild cases within the sample. Inter-rater and test–retest reliability was high with intraclass coefficients (ICC) of 0.983 and 1.00, respectively. Internal consistency was acceptable as indicated by a Cronbach’s alpha of 0.761. Component analysis revealed two principle components. SARA correlated with: (1) all measures of muscle function tested, including quantitative muscle testing of ankle dorsiflexion (r = −0.584*), the 6 min walk test (r = −0.739*), 10 m walk test (r = 0.741*), and the nine hole peg test (r = 0.602*) and (2) measures of disease severity/burden, such as MIRS (r = 0.718*), MDHI (r = 0.483*), and DM1-Activ (r = −0.749*) (*p < 0.001). The SARA score was predicted by an interaction between modal CTG repeat length and age at sampling (r = 0.678, p = 0.003). A score of eight or above predicted the use of a walking aid with a sensitivity of 100% and a specificity of 85.7%. We suggest that further research is warranted to ascertain whether SARA or components of SARA are useful outcome measures for clinical trials in DM1. As a tool, it can be used for gathering information about disease severity/burden and helping to identify patients in need of a walking aid, and can potentially be applied in both research and healthcare settings.

• Item Type: Articles
• Additional Information: This study has been supported by the National Institute of Health Research NIHR under the RD-TRC programme and by the Wyck Foundation . HL is an investigator of the Medical Research Council UK Centre for Neuromuscular Diseases (Reference G1002274, Grant ID 98482).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Monckton, Professor Darren
• Authors: DiPaolo, G., Jimenez-Moreno, C., Nikolenko, N., Atalaia, A., Monckton, D. G., Guglieri, M., and Lochmüller, H.
• College/School: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
• Journal Name: Journal of Neurology
• Publisher: Springer
• ISSN: 0340-5354
• ISSN (Online): 1432-1459
• Published Online: 06 February 2017
• Copyright Holders: Copyright © 2017 The Authors
• First Published: First published in Journal of Neurology 264(4): 701-708
• Publisher Policy: Reproduced under a Creative Commons license