Other muscular dystrophies
Diagnosis of common muscular dystrophies such as myotonic dystrophy type 1, facio-scapulo-humeral muscular dystrophy and oculopharyngeal muscular dystrophy is usually based on classical clinical findings. Therefore, in these muscular dystrophies the role of muscle imaging has yet to be defined. Recent studies performed on these myopathies suggested that some characteristic findings are present, even if there is less diagnostic value compared with CM, LGMD and MFM (Fig. 6).
Fig. 6 Muscle MRI of lower extremities in other muscular dystrophies. Myotonic dystrophy type I (a) is typically characterised by distal more than proximal muscle involvement showing predominant affliction of the soleus, medial gastrocnemius and proximally the anterior thigh compartment with relative sparing of the rectus femoris. Patients with myotonic dystrophy type II (or proximal myotonic myopathy = PROMM) (b) are often less affected and show no fatty degeneration. Affected patients show more involvement of the proximal muscles with affliction of the quadriceps and sparing of the rectus femoris and gracilis muscles. FSHD (c) patients are often characterised by marked asymmetry with the adductor magnus, hamstrings, rectus femoris and tibial anterior being the most frequently affected muscles. OPMD (d) patients show predominantly posterior thigh (adductor magnus, semimembranosus and biceps femoris muscles) and posterior lower leg (soleus) muscle involvement

Myotonic dystrophy
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).
Contrary to DM1, patients with DM2 are less affected based on MRI findings. A recently published whole-body MRI study including DM1 and DM2 patients showed that most of the DM2 patients showed no fatty degeneration, and none of the patients showed any inflammatory changes. The affected patients were exclusively men and showed damage predominantly of the trunk muscles (such as the erector spinae and gluteus) and in some cases involvement of the proximal and lower leg muscles with sparing of the rectus femoris and gracilis muscles in all DM2 patients [27].

Facio-scapulo-humeral muscular dystrophy
Facio-scapulo-humeral muscular dystrophy (FSHD) is the third most common muscular dystrophy (worldwide prevalence 1:20,000) [52]. FSHD is characterised by asymmetric loss of strength and atrophy of muscular tissue starting in the face and shoulder region [56]. These typical clinical findings are also mirrored on muscle imaging, which shows marked asymmetry and involvement of the medial gastrocnemius, the tibial anterior and the soleus muscles in the lower legs. At the thigh, the most frequently involved muscles are the semimembranosus, followed by the biceps femoris, the semitendinosus muscle and the adductor group muscles [57, 58].

Oculopharyngeal muscular dystrophy
Oculopharyngeal muscular dystrophy (OPMD) is a late-onset autosomal dominant dystrophy, and is clinically characterised by slowly progressive ptosis, dysphagia and dysphonia. Proximal limb weakness often develops subsequently [59]. There are few reports on muscle imaging in OPMD. Abnormal fatty infiltration of the tongue, masseter, neck, shoulder girdle, lumbar paraspinous and the gluteus muscles have been described [60].