Objective: To determine if magnetic resonance imaging (MR imaging) is useful in the diagnostic workup of muscular dystrophies and idiopathic inflammatory myopathies for describing the topography of muscle involvement.
Materials and methods: MR imaging was performed in 31 patients: 8 with dystrophic myotony types 1 (n = 4) or 2 (n = 4); 11 with limb-girdle muscular dystrophy, including dysferlinopathy, calpainopathy, sarcoglycanopathy, and dystrophy associated with fukutin-related protein mutation; 3 with Becker muscular dystrophy; and 9 with idiopathic inflammatory myopathies, including polymyositis, dermatomyositis, and sporadic inclusion body myositis.
Results: Analysis of T1 images enabled us to describe the most affected muscles and the muscles usually spared for each muscular disease. In particular, examination of pelvis, thigh, and leg muscles demonstrated significant differences between the muscular diseases. On STIR images, hyperintensities were present in 62% of our patients with muscular dystrophies.
Conclusion: A specific pattern of muscular involvement was established for each muscular disease. Hyperintensities observed on STIR images precede fatty degeneration and are not specific for inflammatory myopathies.