Spin-lock magnetic resonance imaging of muscle in patients with autosomal recessive limb girdle muscular dystrophy

Spin-lock imaging is a new magnetic resonance imaging (MRI) technique used to reflect the microstructural integrity of muscle. The purpose of this stu dy was to characterize spin-lock contrast (SLC) of calf muscles in limb gir dle muscular dystrophy (LGMD). The calf muscles of 5 patients with LGMD and 10 healthy volunteers were imaged with an off-resonance magnetic resonance (MR) spin-lock suppression pulse. Spin-lock suppression ratios were calcul ated for anterior tibialis, posterior tibialis, soleus, and gastrocnemius m uscles. Clinical assessments of muscle strength were compared to the spin-l ock suppression ratios in the LGMD group. Strong SLC was observed in health y muscles, with mean (+/- SD) suppression ratios ranging from 51.2% (+/-3.6 %) to 56.3% (+/- 1.3%). In diseased muscle, spin-lock signal suppression wa s reduced by 8%-70%, demonstrating an inverse correlation between symptom d uration and suppression ratios. Spin-lock contrast in the patients with LGM D, as a reflection of tissue integrity, was best preserved in posterior tib ialis, anterior tibialis, soleus, and gastrocnemius muscles in descending o rder. Clinical assessments did a poorer job of differentiating than SLC did and were in poor agreement with spin-lock suppression ratios. Spin-lock MR I can quantify microstructural changes in LGMD and appears to provide infor mation not obtainable from clinical evaluations. This suggests that this no ninvasive technique may be useful in evaluating the extent, progression, an d response to therapy of LGMD.