Assessment of quadriceps femoris muscle atrophy and hypertrophy in neuromuscular disease in children.

Midthigh muscle and subcutaneous tissue thickness were measured using a real-time linear array ultrasound scanner in 50 patients attending our Muscle Clinic; 28 had muscular dystrophy and 21 spinal muscular atrophy. In muscular dystrophy the muscle thickness was found to be normal or increased, whereas in spinal muscular atrophy it was reduced, with an associated increase in subcutaneous tissue thickness that did not relate to obesity. Measurement of muscle and subcutaneous tissue thickness provides a more accurate way of assessing muscle atrophy and hypertrophy than clinical assessment, and is a useful guide in the discrimination between muscular dystrophy and spinal muscular atrophy.