Muscle MRI findings of X-linked spinal and bulbar muscular atrophy.

We report here muscle MRI findings of the lower limb in X-linked spinal and bulbar muscular atrophy (SBMA). T1-weighted imaging of muscle MRI disclosed that the thigh muscles, including the semimembranosus, biceps femoris longus and the vastus lateralis muscles, showed high intensity signals with atrophy. Contrarily, the sartorius, gracilis and rectus femoris muscles were comparably preserved. Not only the thigh muscles, but also the calf muscles including the gastrocnemius medialis and lateralis, and soleus muscles showed high intensity signals. In amyotrophic lateral sclerosis (ALS), the leg muscles are generally atrophic, but the selective pattern of fatty degeneration, seen in SBMA was not observed. Muscle MRI is a useful method of estimating the distribution and severity of SBMA in affected muscles.