Patterns of selective involvement of thigh muscles in neuromuscular disease.

In 14 patients with limb girdle muscular dystrophy, polymyositis, and type 3 spinal muscular atrophy, CT scans of the thigh muscles were correlated with single fiber EMG studies in vastus lateralis, semimembranosus and biceps femoris muscles. There was a relation between the extent of CT scan abnormality and increased fiber density in the three muscles studied, except in the most severely affected muscles in which in some muscles the fiber density values were lower than expected. These results were independent of the underlying pathology. Correlative CT/SFEMG studies provide insights into the pattern of selective involvement of certain muscles in neuromuscular disorders.