Annals of Indian Academy of Neurology
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This study found that muscle fat fraction (MFF) measured by Dixon MRI correlates strongly with clinical severity in Duchenne muscular dystrophy (DMD). The gluteus maximus had the highest fat fraction, while quadriceps MFF showed the strongest correlation with clinical scores. This suggests Dixon MRI can serve as a reliable biomarker for disease progression in DMD.
**Background:** Duchenne muscular dystrophy (DMD) is a severe X-linked recessive disorder characterized by progressive muscle degeneration and weakness. Quantitative MRI using the Dixon technique to measure muscle fat fraction (MFF) is a more precise and reliable method than visual assessment for longitudinal follow-up. This study aimed to detect any correlation between a one-time MFF estimation using Dixon MRI and clinical phenotype in DMD.
**Methods:** This was a single-centre prospective observational study. Boys with genetically confirmed DMD, aged between 6 and 18 years with independent ambulation, were recruited. Age, muscle strength assessment, MRC sum score, North Star Ambulatory Assessment (NSAA), and 6-minute walk test (6MWT) were evaluated. MRI was obtained, and a single axial slice at 50% distance between the hip and knee joint was chosen for examining the quadriceps, adductors, and hamstrings. Another axial section at the femoral head was chosen for the gluteus maximus. The images were processed by MATLAB-based codes.
**Key Results:** Thirty-five boys with a median age of 8 years (mean 8.34 years, range 6-12 years) were included. The highest MFF was found for the gluteus maximus (mean 51.11 ± 23.56 and 49.38 ± 24.85 for right and left, respectively), followed by the quadriceps (mean 26.51 ± 20.58 and 26.35 ± 21.25 for right and left, respectively). There was a positive correlation between MFF of muscle groups and age, strongest for the quadriceps (r = 0.619, p < 0.001 and r = 0.597, p < 0.001 for right and left quadriceps, respectively). The MFF of all muscle groups correlated significantly with all clinical parameters (MRC sum score, NSAA, 6MWT).
**Clinical Implications:** This study demonstrates that MFF measured by Dixon MRI correlates strongly with clinical measures of disease severity in DMD. The gluteus maximus showed the highest fat infiltration, while quadriceps MFF had the strongest correlation with functional outcomes. These findings suggest that Dixon MRI can serve as a reliable, non-invasive biomarker for disease progression and treatment response in DMD clinical trials and patient management.