[Distribution of skeletal muscle involvement in myotonic dystrophy--a computed tomographic study]

The computed tomography (CT) scan was performed on 8 myotonic dystrophy (MD) and 3 congenital myotonic dystrophy (CMD) patients on the following seven levels; the jaw, the neck, the shoulder girdle, the abdomen, the pelvic girdle, the thigh and the lower leg. Muscle atrophy was shown as low density areas or a reduction in the cross-sectional area of the muscles. The earliest finding in the disease was severe atrophy of the sternocleidomastoid and mild atrophy of the masseter and the pterygoid medialis. In addition, spinal, abdominal wall and lower leg muscles were involved. The distal muscles were more markedly affected than the proximal in the lower limbs. These changes were characteristically observed in cases without apparent muscle symptoms. Levator scapulae, psoas major, rectus femoris, peroneal longus et brevis and tibialis posterior were relatively well preserved and were even hypertrophic in some cases. The shoulder girdle muscles were more markedly affected than the pelvic girdle muscles. There was no substantial difference in the CT findings between MD and CMD.