Whole-body high-field magnetic resonance imaging in myotonic dystrophy type 1 and type 2

Background: The aim of the present study was to determine if whole-body high-field Magnetic Resonance Imaging (MRI) techniques may identify characteristic patterns of skeletal muscle affection and subclinical skeletal muscle involvement in Myotonic Dystrophy Type 1 (DM1) and Type 2 (DM2).

Methods: 15 DM1 (5m/10f; mean age 46+/-15 y) and 14 DM2 pat. (8m/6f; mean age 52+/-12 y) were studied by whole-body MRI of 3.0 T using a standard body coil and flexible table top extension (transversal slices, T1 TSE, T2 TSE, T2 TSE SPAIR). Skeletal muscle signal changes were graded on a 3 point scale. Clinical muscular impairment was assessed using clinical scores.

Results: All DM1 pat. presented with skeletal muscle fatty degeneration and edema. 11 pat. showed affection of distal as well as proximal lower limb muscles. Trunk muscle involvement was seen in 10 DM1 patients. The medial heads of gastrocnemius muscles were more severely affected compared with the lateral heads in 8/15 patients. Quadriceps muscle affection was characterized by a specific perifemoral semilunar pattern in all but one patient. Gastrocnemius, soleus and vastus medialis muscles were most frequently affected in DM1. 13 pat. showed moderate to severe esophageal dilation. In 12 pat., MRI data were in line with the clinical score. In further 3 pat., MRI was able to detect subclinical skeletal muscle involvement.

9 DM2 pat. showed normal MRI results. Erector spinae and gluteus maximus muscles were most frequently affected in the remaining 5 pat. with pathological MRI results. In 9 DM2 pat., MRI data were not in line with the clinical evaluation. In 2 of these pat., MRI was able to detect subclinical trunk muscle involvement. Further 7 pat. with normal MRI results clinically presented with mild hip girdle weakness. In contrast to DM1, pathological results emerged with increasing age and were restricted to women in DM2.

Conclusions: Whole-body 3.0 T MRI is a sensitive imaging technique and demonstrated a characteristic pattern of skeletal muscle affection in DM1. In contrast, MRI was no reliable indicator for skeletal muscle involvement in DM2. Myalgia and mild muscle weakness were usually not reflected by MRI signal alterations in this disease entity. MRI was able to detect subclinical skeletal muscle affection in a small subgroup of DM1 and DM2 pat. each. However, there were significant gender- and age-dependent differences between both disease entities. Esophageal involvement was exclusively seen in DM1.