Ambulatory Duchenne Muscular Dystrophy Children: Cross-sectional Correlation between Function, Quantitative Muscle Ultrasound and MRI

Introduction/Aims: Duchenne muscular dystrophy (DMD) is a progressive genetic muscle disease. Quantitative muscle ultrasound (MUS), muscle MRI, and functional tools are important to delineate characteristics of muscle involvement. We aimed to establish correlations between clinical/functional and above-named imaging tools respecting their diagnostic and prognostic role in DMD children. Methods: A Prognostic cross-sectional retrospective study of 27 steroid-naive, ambulant male children/adolescents with genetically-confirmed DMD (mean age, 8.8 +/- 3.3 years). Functional performance was assessed using motor function measure (MFM) which assess standing/transfer (D1), proximal (D2) and distal (D3) motor function. And six-minute-walk test (6MWT). Imaging evaluation included quantitative muscle MRI which measured muscle fat content in a specific location of right rectus femoris by mDixon sequence. Quantitative MUS measured muscle brightness in standardized US image as an indicator of muscle fat content. Results: We found a highly significant positive correlation between the mean MFM total score and 6MWT (R=0.537, P=0.007). And a highly significant negative correlation between fat content by MUS and MFM total score (R=-0.603, P=0.006) and its D1 subscore (R=-0.712, P=0.001). And a significant negative correlation between fat content by US and 6MWT (R=-0.529, P=0.02). And a significant positive correlation between muscle fat content by mDixon MRI and patient's age (R=0.617, P=0.01). Discussion: Quantitative MUS correlates significantly with clinical/functional assessment tools as MFM and 6MWT, and augments their role in disease-tracking of DMD. Quantitative MUS has the potential to act as a substitute to functional assessment tools. The role for quantitative muscle MRI in disease-tracking should be further explored after elimination of confounding factors.