Quantitative Muscle Ultrasound: A Non-Invasive Biomarker for Monitoring Duchenne Muscular Dystrophy

Introduction/Aims: Quantitative muscle ultrasound (QMUS) shows promise as a non-invasive biomarker for monitoring functional status in Duchenne muscular dystrophy (DMD). We evaluated the correlation between QMUS in various muscles and functional capacity assessments. Additionally, we compared the utility of composite QMUS scores as a comprehensive measure of disease progression to that of single-muscle analyses. Methods: We analyzed baseline data from an ongoing prospective study involving 23 patients with DMD (aged 5–18 years; mean 10.7; SD 4.2). High-resolution ultrasound scans of muscle groups across the upper and lower limbs, head and neck, and diaphragm were assessed for muscle echogenicity using mean grayscale values (MGV). Functional capacity assessments included the 6-min walk test (6MWT), North Star Ambulatory Assessment (NSAA), Performance of Upper Limb (PUL) module, timed function tests, quantitative muscle strength tests, and respiratory muscle strength tests. Results: The composite MGV for upper and lower limbs demonstrated moderate to strong negative correlations with the 6MWT and NSAA scores (correlation coefficient [CC]: −0.44 to −0.74; p < 0.01) and strong to very strong positive correlations with rise-from-floor, 4-stair climb, and 10-m walk/run times (CC: 0.65 to 0.87; p < 0.01). For upper limb function, the MGV of the flexor carpi radialis muscle was negatively correlated with PUL scores (CC = −0.35, p = 0.02). However, no significant correlations were observed between QMUS parameters and muscle strength test (p > 0.05). Discussion: QMUS offers a non-invasive method for assessing muscle changes and tracking disease progression in DMD. Trial Registration: ClinicalTrials.gov identifier: NCT05249361.