Neuromuscular diseases: evaluation with high-frequency sonography. Forty-four patients with clinically suspected neuromuscular disease and 12 healthy volunteers underwent high-frequency ultrasound examination of the rectus femoris, vastus medialis, vastus lateralis, and biceps brachii muscles, and the number of perimysial septa was determined. These numbers and muscle/soft-tissue ratios of the lower extremity were compared. Findings were correlated with results of muscle biopsy in all patients with suspected disease. Using the number of perimysial septa in the lower extremity, the authors found significant differences between the muscles of healthy volunteers and those of patients with Duchenne muscular dystrophies, other muscular dystrophies, and spinal muscular atrophies: The receiver operating characteristic curve showed that an average of 12 perimysial septa within 1 cm of muscle is the ideal cutoff value to differentiate subjects without morphologic changes from those with pathologic findings. The authors conclude that this measurement is useful for differentiation of neuromuscular diseases and may be a noninvasive, reproducible means with which to evaluate disease progression. 