Computed tomography of the skeletal musculature in Becker-type muscular dystrophy and benign infantile spinal muscular atrophy.

Results of computed tomographic (CT) examination of the skeletal musculature in 26 patients with Becker-type muscular dystrophy (BMD) and 12 patients with benign infantile spinal muscular atrophy (BISMA) are presented. Both disorders revealed strikingly different changes that may have important clinical significance. First, in BMD, CT abnormalities consisted of areas of decreased densities, at first appearing in part of the muscle, and then gradually spreading until the whole muscle was replaced by low-density tissue. In BISMA, however, low-density lesions were scattered throughout the muscle. Second, in BMD, some muscles were preferentially affected in an early stage of the disease and others were relatively spared, whereas in BISMA, the muscles were involved more or less simultaneously. Third, an enlargement in size (hypertrophy) was frequently observed in BMD in various muscles of the legs, whereas in BISMA, this phenomenon can sometimes be noted only in the gastrocnemius muscles.