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

Abstract

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.

Diaphragmatic and Rectus Femoris Muscles Ultrasonography in Relation to Motor and Respiratory Functions in Ambulatory Boys with Duchenne Muscular Dystrophy

“…A significant higher difference in the median and IQR of the total score of GSGC of patients with grade IV modified Heckmatt scale was found in comparison to grade II and III (15 [12][13][14][15][16][17] vs. 8 [7][8][9][10], 11 [11][12][13], p < 0.001).…”

“…Furthermore, it has the potential to act as a substitute to functional assessment tools. 12 The aim of the current research was to study the correlation between GSGC (Gait, Stairs, Gower, Chair) motor functional score and the US findings of RF (modified Heckmatt and quantitative gray scale analysis). In view of the emerging therapeutic interventions for DMD, more valid tools for clinical assessment of patients are entailed.…”

Generation of percentile curves for strength and functional abilities for boys with Duchenne muscular dystrophy

“…6 This may be explained by the fact that the 6 MWT and muscle strength of the knee extensor have a negative and significant correlation with muscle fat. 21,26 Thus, as the disease progresses, the amount of fat in the muscle tissue increases, emphasizing knee extensor weakness and, consequently, worsening of the patient's performance on the 6 MWT.…”

“…The decline in walking ability measured by the 6 MWT occurs despite small changes in strength values of the knee extensor muscles across 1 year of longitudinal evaluation 6 . This may be explained by the fact that the 6 MWT and muscle strength of the knee extensor have a negative and significant correlation with muscle fat 21,26 . Thus, as the disease progresses, the amount of fat in the muscle tissue increases, emphasizing knee extensor weakness and, consequently, worsening of the patient's performance on the 6 MWT.…”

Quantitative ultrasonography reveals skeletal muscle abnormalities in carriers of DMD pathogenic variants

“…In-depth characterization of skeletal as well as cardiac involvement in cDMD deserves investigation, and advanced imaging techniques could facilitate this. 5,[9][10][11][12][13][14][15] For instance, cardiac magnetic resonance imaging (MRI) studies revealed myocardial fibrosis in up to 49% of cDMD (even in early stages), compared with 5% of noncarriers, highlighting the importance of imaging follow-up of this population. 15 Fornander et al 8 found in a cross-sectional study that both clinically symptomatic and asymptomatic cDMD have a higher fat fraction in muscles detectable by magnetic resonance imaging.…”