Transverse T1-weighted (upper row) and spectral fat-suppressed T2-weighted MR image (bottom row) of the thighs of a 48-year-old woman presenting with myotonic dystrophy type 1. Note the different degrees of fatty degeneration within the gastrocnemius muscle. The medial head shows an end-stage fatty degeneration (grade 4 according to the Mercuri and Fischer scale, grade 3 according to the Kornblum scale, Table 1). The muscle tissue is completely replaced by fat. The lateral head shows a moth-eaten appearance with scattered small areas of increased signal (fatty degeneration grade 2 according to the rating scales established by Mercuri et al., Kornblum et al. and Fischer et al., Table 1). The fat-suppressed T2-weighted image shows a high signal in the medial head of the gastrocnemius muscle indicating oedema because of inflammatory changes before and during the degenerative disease stages