Muscle MRI and functional outcome measures in Becker muscular dystrophy

Abstract

Becker muscular dystrophy (BMD) is a neuromuscular disorder allelic to Duchenne muscular dystrophy (DMD), caused by in-frame mutations in the dystrophin gene, and characterized by a clinical progression that is both milder and more heterogeneous than DMD. Muscle magnetic resonance imaging (MRI) has been proposed as biomarker of disease progression in dystrophinopathies. Correlation with clinically meaningful outcome measures such as North Star Ambulatory Assessment (NSAA) and 6 minute walk test (6MWT) is paramount for biomarker qualification. In this study, 51 molecularly confirmed BMD patients (aged 7–69 years) underwent muscle MRI and were evaluated with functional measures (NSAA and 6MWT) at the time of the MRI, and subsequently after one year. We confirmed a pattern of fatty substitution involving mainly the hip extensors and most thigh muscles. Severity of muscle fatty substitution was significantly correlated with specific DMD mutations: in particular, patients with an isolated deletion of exon 48, or deletions bordering exon 51, showed milder involvement. Fat infiltration scores correlated with baseline functional measures, and predicted changes after 1 year. We conclude that in BMD, skeletal muscle MRI not only strongly correlates with motor function, but also helps in predicting functional deterioration within a 12-month time frame.

The value of qualitative muscle MRI in the diagnostic procedures of myopathies: a biopsy-controlled study in 191 patients

“… 22 In hereditary muscular disorders, MRI has also been proposed as a tool for identifying patterns of muscular involvement and as a biomarker of disease progression. 2 , 25 – 27 However, it remains an unsolved question whether MRI findings can provide enough information to deduce a diagnosis. Since the underlying pathophysiology cannot be differentiated, muscle MRI can qualitatively only differentiate severity and distribution of morphological changes in size and shape, severity and distribution of lipomatous changes, and presence of muscle edema.…”

Duchenne Muscular Dystrophy: recent advances in protein biomarkers and the clinical application

“…These aspects have consequences on the sensitivity and accuracy of the functional tests. Beside physical tests, skeletal muscle composition in terms of Magnetic Resonance Imaging (MRI) measured fat fraction is currently used as an exploratory biomarkers for DMD [28,29]. The fat fraction in muscles correlates with functional outcomes [30], physical tests, and predict deterioration of patient mobility [29,31,32].…”

Advances in Quantitative Imaging of Genetic and Acquired Myopathies: Clinical Applications and Perspectives

“…In 51 molecularly confirmed Becker Muscular Dystrophy (BMD) patients, muscle MRI showed a pattern of fatty substitution involving mainly the hip extensors and most thigh muscles (12). The severity of muscle fatty substitution significantly correlated with specific DMD gene mutations (i.e., patients harboring deletion of exon 48 or deletions bordering exon 51 presented a milder involvement).…”