Magnetization transfer imaging of skeletal muscle in autosomal recessive limb girdle muscular dystrophy

Purpose: The purpose of this work was to characterize magnetization transfe r (MT) contrast of skeletal muscles in limb girdle muscular dystrophy (LGMD ). Method: The calf muscles of five LGMD patients and 10 normal volunteers wer e imaged with an off-resonance MT suppression pulse applied to T1-weighted images. MT suppression ratios were calculated for anterior tibialis. poster ior tibialis, soleus, and gastrocnemius muscles in the LGMD and control gro ups. The relationship between MT of individual muscles and the duration of LGMD symptoms was determined. Results: Strong MT contrast was observed in normal calf muscles, with mean (I-SD) suppression ratios ranging from 37.9% (+/-3.0) to 41.1% (+/-2.1). In diseased muscle, MT signal suppression ranged from 11 to 38%, demonstratin g an inverse relationship between symptom duration and suppression ratios. MT contrast in the LGMD patients, as a reflection of muscle tissue integrit y, was preserved in posterior or anterior tibialis, soleus, and gastrocnemi us muscles, respectively. Suppression ratios were dramatically reduced in m uscles with gross fatty infiltration but also were reduced in muscle tissue s without visual evidence of fatty infiltration. Conclusion: MT imaging provides a quantitative measure of pathologic change s occurring within the skeletal muscles of patients with LGMD relative to n ormal and may be useful in evaluating disease extent, progression, and resp onse to new therapies as they become available.