P.82 - Long-term follow-up of MRI changes in thigh muscles of patients with facioscapulohumeral dystrophy: a quantitative study

E Salort-Campana,F Fatehi,A Le Troter,E Lareau-Trudel,M Bydder,M Guye,D Bendahan,S Attarian

doi:10.1016/j.nmd.2017.06.112

Abstract

Facioscapulohumeral muscular dystrophy (FSHD) has no known effective treatment. Determination of the efficacy of a therapy might be difficult in FSHD given the slow and highly variable disease progression. Our objective was to investigate longitudinally the time-dependent changes occurring in thigh muscles of FSHD patients using quantitative MRI and to assess the potential relationships with the clinical findings. 35 FSHD1 patients were enrolled. Clinical assessment including manual muscle testing (MRC) and motor function measure (MFM) were recorded each year for a period ranging from 1 to 2 years. For the MRI measurements, we used a new quantitative index i.e. the mean pixel intensity (MPI) calculated from the pixel-intensity distribution in T1 weighted images. The corresponding MPI scores were calculated for each thigh, for each compartment and for both thighs totally (MPItotal). The total mean pixel intensity (MPItotal) refers to the sum of each pixel signal intensity divided by the corresponding number of pixels. An increased MPItotal indicates both a raised fat infiltration together with a reduced muscle volume thereby illustrating disease progression. Clinical scores did not change significantly over time whereas MPItotal increased significantly from an initial averaged value of 39.6 to 41.1 with a corresponding rate of 0.62/year. While clinical scores and MPItotal measured at the start of study were significantly related, no correlation was found between the rate of MPItotal and MRC sum score changes, MFMtotal and MFM subscores. The relative rate of MPItotal change was 2.3% (0.5 – 4.3)/year and was significantly higher than the corresponding rates measured for MRCS 0% (0 – 1.7) /year and MFMtotal 0% (0 – 2.0) /year (p = 0.000). These results suggested that the MPItotal index could be used as a reliable biomarker and outcome measure of disease progression. In slowly progressive myopathies such as FSHD, the MPItotal index might reveal subclinical changes, which could not be evidenced using clinical scales over a short period of time.

Highlights

Facioscapulohumeral muscular dystrophy (FSHD, OMIM #158900) is one of the most common hereditary muscular disorders, with a reported prevalence of 3.2–4.6 per 100,000 [1,2,3]
We longitudinally investigated muscle changes in FSHD patients using traditional clinical scores and a new Magnetic resonance imaging (MRI) index i.e. mean pixel intensity (MPI) which is a quantitative index calculated from the pixel intensity distribution in T1W images and illustrating both muscle loss and fat infiltration
MPItotal significantly changed over the reported period in all the muscle compartments whereas the clinical scores (MFM, Clinical Severity Score (CSS), MRC sum score (MRCS)) did not

Summary

Introduction

Facioscapulohumeral muscular dystrophy (FSHD, OMIM #158900) is one of the most common hereditary muscular disorders, with a reported prevalence of 3.2–4.6 per 100,000 [1,2,3]. On the contrary to what has been concluded from the natural history study, there was an apparent increase in strength at 6 months in 2 of the 3 clinical trials in both the placebo and treatment groups, that persisted for up to 1 year for MVICT scores. These paradoxical results illustrate that patient motivation can confound the performance measurements such as MVICT and MMT which are effort dependent. Other outcome measures would be warranted for future clinical trials

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