Corticosteroid therapy in avian muscular dystrophy: evaluation by magnetic resonance relaxation times

Genetically dystrophic chicks (line 413) were administered 0.3 mg/kg dexamethasone (DEX), a corticosteroid, from 2 to 28 days ex ovo. Diluent-injected dystrophic and normal (line 412) chicks served as controls. The effects of DEX on muscle function were evaluated weekly by the exhaustion score (ES) method. Proton magnetic resonance relaxation times, T1 and T2, of excised pectoral muscles of all chicks were measured at 31 days of age. There were two measurable components of T1 and T2 relaxation times, all of which were significantly prolonged in control dystrophic muscles. DEX improved ESs of dystrophic chicks and these functional improvements were reflected in significant reductions in the short and long components of T1 and T2. This study suggests that magnetic resonance techniques, including imaging, can complement and extend the information obtained by other methods that are commonly used in therapeutic studies of muscle disorders.