T2 relaxation times are increased in Skeletal muscle of DMD but not BMD patients.

Abstract

Exon-skipping drugs in Duchenne muscular dystrophy (DMD) aim to restore truncated dystrophin expression, which is present in the milder Becker muscular dystrophy (BMD). MRI skeletal muscle T2 relaxation times as a representation of edema/inflammation could be quantitative outcome parameters for such trials. We studied T2 relaxation times, adjusted for muscle fat fraction using Dixon MRI, in lower leg muscles of DMD and BMD patients and healthy controls. T2 relaxation times correlated significantly with fat fractions in patients only (P < 0.001). After adjusting for muscle fat, T2 relaxation times were significantly increased in 6 muscles of DMD patients (P < 0.01), except for the extensor digitorum longus. In BMD, T2 relaxation times were unchanged. T2 relaxation times could be a useful outcome parameter in exon-skipping trials in DMD but are influenced by fat despite fat suppression. This should be accounted for when using quantitative T2 mapping to investigate edema/inflammation.