Myotonic dystrophy types 1 and 2 (DM1, DM2) are autosomal dominantly inherited multisystem disorders and genetically characterised by pathogenic repeat mutations. DM1 is—with an estimated prevalence of 1 in 8,000—the second most common muscular dystrophy worldwide [52]. The clinical phenotype and pattern of muscle affliction differ between DM1 and DM2 (or proximal myotonic myopathy = PROMM) but also show some overlap. Almost all DM1 patients show signs of fatty degeneration and/or oedematous changes in the striated muscles on muscular MRI. Most of the patients show severe fatty degeneration of the proximal and distal lower limb muscles. There is a predominant affliction of the anterior compartment of the thighs compared with the posterior compartment with a relative sparing of the rectus femoris muscles [27, 53, 54]. Particularly, the vastus muscles frequently show a semi-lunar peri-femoral area of fatty degeneration [53, 55]. In the lower legs of DM1 patients, the gastrocnemius muscles show early and frequent involvement, whereas the posterior tibial muscles are relatively unaffected. In addition, whole-body MRI protocols can frequently detect the involvement of other organs in DM1 patients. Dypshagia is a common clinical finding in DM1 patients, which is reflected by a substantial dilatation of the oesophagus that can be easily detected and rated on MRI (Fig. 2).