Ultrasound measures dynamic changes to upper extremity skeletal muscles in patients with neuromuscular disease


Translational Research

Poster Number: S54


Allison McCrady, University of Virginia, Chelsea Masterson, BA, University of Virginia, Laura Barnes, PhD, University of Virginia, Rebecca J. Scharf, MD, University of Virginia, Silvia S. Blemker, PhD, University of Virginia

Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA) are progressive neuromuscular diseases where inflammation and fibrosis or motor nerve degeneration lead to fatty infiltration and contribute to severe muscle weakness and functional decline. Current functional assessments using subjective ratings of participatory tasks are not inclusive to patients with cognitive challenges (45% of patients with DMD), young participants, or those stressed in a clinical environment. Image-based biomarkers of skeletal muscle can objectively quantify functional ability, however current studies largely focus on intramuscular fatty infiltration ignoring change to muscle size. Our previous work indicates the combination of muscle size and tissue quality is essential to predict skeletal muscle functional capacity in neuromuscular disease. This study aims to determine the ability of ultrasound to detect skeletal muscle size and quality changes over three years in patients with DMD or SMA. Ultrasound images of the dominant arm biceps brachii muscles of 27 participants (10 DMD, 9 SMA, 7 healthy controls) were collected. Muscle size was quantified through cross-sectional area (CSA), and tissue quality was quantified through echogenicity (image brightness), which corresponds to the intramuscular fibrosis and fat. Patients with DMD younger than 12 years showed maintenance of or >10% increase in biceps brachii CSA normalized by forearm length over time. Patients with SMA are less consistent in normalized CSA change over time, with some patients showing decreases greater than 10%, and others showing an increase of >30%. Patients with DMD across all ages indicated larger increases in echogenicity over time of >15% compared to patients with SMA and typically developing participants. Patients with SMA showed smaller increases or decreases in echogenicity over time. Future work will integrate these measurements to estimate changes to functional capacity over time. Ultrasound imaging allows tracking of functional changes objectively in the clinic, overcoming limitations of current assessments, and improving patient care.