Abstract
ObjectiveTo translate the quantitative MRC Centre MRI protocol in Charcot-Marie-Tooth disease type 1A (CMT1A) to a second site; validate its responsiveness in an independent cohort; and test the benefit of participant stratification to increase outcome measure responsiveness.MethodsThree healthy volunteers were scanned for intersite standardization. For the longitudinal patient study, 11 patients with CMT1A were recruited with 10 patients rescanned at a 12-month interval. Three-point Dixon MRI of leg muscles was performed to generate fat fraction (FF) maps, transferred to a central site for quality control and analysis. Clinical data collected included CMT Neuropathy Score.ResultsTest-retest reliability of FF within individual healthy calf muscles at the remote site was excellent: intraclass correlation coefficient 0.79, limits of agreement −0.67 to +0.85 %FF. In patients, mean calf muscle FF was 21.0% and correlated strongly with disease severity and age. Calf muscle FF significantly increased over 12 months (+1.8 ± 1.7 %FF, p = 0.009). Patients with baseline FF >10% showed a 12-month FF increase of 2.9% ± 1.3% (standardized response mean = 2.19).ConclusionsWe have validated calf muscle FF as an outcome measure in an independent cohort of patients with CMT1A. Responsiveness is significantly improved by enrolling a stratified patient cohort with baseline calf FF >10%.
Highlights
Three healthy volunteers were scanned for intersite standardization
Responsiveness is significantly improved by enrolling a stratified patient cohort with baseline calf fat fraction (FF) >10%
Quantitative skeletal muscle MRI has been widely studied as an outcome measure in muscle diseases,[4,5] and we recently reported high responsiveness over 12 months in Charcot-Marie-Tooth disease type 1A (CMT1A) in a UK cohort.[6]
Summary
For the longitudinal patient study, 11 patients with CMT1A were recruited with 10 patients rescanned at a 12month interval. Three-point Dixon MRI of leg muscles was performed to generate fat fraction (FF) maps, transferred to a central site for quality control and analysis. Clinical data collected included CMT Neuropathy Score. MRI was performed at the University of Iowa, Iowa City, with anonymized MRI data transferred for analysis at the MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, UK. Eleven patients with genetically confirmed CMT1A were recruited for examination at baseline and 12 months. Disease duration, and the CMT Neuropathy Score (CMTNS) (a composite disease severity scale ranging from 0 = normal to 36 = maximum severity) were recorded. The examination score (CMTES) component was used. The MRC Centre MRI protocol, identical to that used previously,[4] was performed using a similar scanner
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