A comparative study of the fatty infiltration of thigh muscles in Becker and Duchenne muscular dystrophy

Abstract

Objective To analyze the characteristics of fat infiltration into the muscles of patients with Becker and Duchenne muscular dystrophy (DMD) so as to provide a guide for rehabilitation therapy. Methods Twenty-three children with Becker muscular dystrophy (BMD) and 47 with DMD who had never been treated with glucocorticoids were enrolled. MRI was performed on both of their thigh muscles. T1 weighted images were used to assess the fat infiltration of their thigh muscles using a 0-5 modified version of Mercuri′s scale. The progression of fatty infiltration of the thigh muscles in BMD was analyzed using descriptive statistics. The differences in fat infiltration between BMD and DMD were analyzed using rank sum tests. Results In patients with BMD the adductor magnus most often showed severe fat infiltration, followed by the biceps femoris, quadriceps, semimembranosus and semitendinosus, while the sartorius, gracilis and adductor longus had the lowest percentages of severe fat infiltration. Among the BMD patients the adductor magnus, biceps femoris and quadriceps showed moderate to severe involvement at the age of 8 to 9. The semimembranosus and semitendinosus showed moderate to severe involvement at the age of 10 to 11, and the sartorius, gracilis and adductor longus showed mild to moderate involvement after 15 years of age. Among the age groups of 8, 9, 10 and 11 years old, the median total fat infiltration scores were 10, 22, 28 and 25 respectively among the BMD patients, and 29, 34, 34 and 30 respectively among the DMD patients. At age 8 significant differences between the BMD and DMD patients were observed in the infiltration scores of the adductor magnus, biceps femoris, vastus lateralis, rectus femoris, vastus medialis, vastus intermedius and in the total scores. At age 9 significant differences persisted in the scores of the adductor magnus, rectus femoris, vastus medialis, vastus intermedius and the total scores. Conclusions The muscle MRIs showed significant differences in the degree of fatty infiltration between BMD and DMD patients. These findings may be useful when designing therapeutic regimens and rehabilitation programs for patients with BMD and DMD. Key words: Muscular dystrophy; Muscles, Skeletal; Fatty infiltration