Lower extremity muscle pathology in myotonic dystrophy type 1 assessed by quantitative MRI

Objective: To determine the value of quantitative MRI to provide imaging biomarkers for disease in 20 different upper and lower leg muscles of myotonic dystrophy type 1 (DM1) patients.

Methods: We acquired images covering these muscles in 33 genetically and clinically well-characterized DM1 patients and 10 unaffected controls. MR images were recorded with a Dixon method to determine muscle fat fraction, muscle volume and contractile muscle volume, and a multi-spin echo sequence to determine T2 water relaxation time (T2water), reflecting putative oedema.

Results: Muscles in DM1 patients had higher fat fractions than muscles of controls (15.6%±11.1% vs. 3.7%±1.5%). Also, patients had smaller muscle volumes (902±232 cm3 vs. 1097±251 cm3), contractile muscle volumes (779±247 cm3 vs. 1054±246 cm3), and increased T2water (33.4±1.0 ms vs. 31.9±0.6 ms), indicating atrophy and oedema, respectively. Lower leg muscles were affected most frequently, especially the gastrocnemius medialis and ...