Reduced intramuscular blood flow correlates with more severe pathology in boys with Duchenne/Becker muscular dystrophy

Objective: To relate intramuscular blood flow to the degree of muscle pathology in two ways: by comparing Duchenne muscular dystrophy (DMD) to Becker muscular dystrophy (BMD) and by correlation with muscle echointensity. Background: Intramuscular blood flow is thought to be reduced in D/BMD and may contribute to the pathology. Blood flow in small intramuscular vessels, unlike large vessels, cannot be quantified using color Doppler sonography. We use a previously developed protocol to quantify blood flow in small intramuscular vessels using power Doppler sonography in muscular dystrophy patients. Design/Methods: We obtained ultrasound images of the anterior forearm (AF) and tibialis anterior (TA) muscles of boys with D/BMD. We quantified the change in intramuscular blood flow between rest and after one minute of exercise, measured as a percentage of muscle area. We compared the change in blood flow between boys with DMD, BMD, and historic controls, and correlate blood flow to the mean echointensity (grey scale level) measured from the same muscle. Results: We imaged 8 boys with DMD and 3 boys with BMD ages 6–19 years old. Intramuscular blood flow (% median change (range)) in the AF was less in 7 of 8 forearms in DMD (0.25% (−0.47 – 2.19)) than the lowest BMD (2.46%(2.02 – 3.38), n=3) and the lowest historic control (2.16%). Intramuscular blood flow in the TA was lower in all (4/4) DMD (0.70% (0.16 – 1.89)) than the lowest BMD (5.08% (2.28 – 9.51), n=3) and the lowest historic control (3.91%). Intramuscular blood flow in boys with D/BMD decreased with higher muscle echogenicity (rs= −0.6, p=0.007). Conclusions: Intramuscular blood flow in boys with D/BMD can be quantified using power Doppler, and reduction correlates with more severe pathology in DMD compared to BMD and as measured by echointensity. Disclosure: Dr. Dietz has nothing to disclose. Dr. Connolly has received personal compensation for activities with Catabasis, Sarepta, BMSquibb, Fibrogen Therapeutics, Cytokinetics, Avexis, and Bamboo. Dr. Connolly has received research support from PTC Therapeutics, Serapta Therapeutics, Lilly, Fibrogen, Cytokinetics, Ionis, ISIS, Halo Therapeutics Dr. Golumbek has nothing to disclose. Dr. Zaidman has nothing to disclose.