Lower limb muscle magnetic resonance imaging in Chinese patients with myotonic dystrophy type 1

Objectives: Muscle magnetic resonance imaging (MRI) is a reliable noninvasion tool for detecting muscle abnormalities of myopathies. This study aimed to investigate the MRI features of lower limb muscles in Chinese patients with myotonic dystrophy type 1 (DM1) and to evaluate the correlation between clinical factors and muscle MRI.Methods: We retrospectively reviewed the medical records and lower limb muscle MRI in 24 Chinese DM1 patients. Muscular Impairment Rating Scale (MIRS) was used to assess the clinical muscular impairment. Modified Mercuri's scale was used to assess the degree of fatty infiltration. Spearman rank correlation test was used to analyze the relationship between fatty degeneration score with age, age of onset, disease duration, MIRS grading and creatinine kinase (CK) level.Results: Fatty infiltration was found in 22 of 24 DM1 patients and 8 patients were asymmetrically affected. The medial gastrocnemius was the most affected muscle, followed by soleus and tibialis anterior muscles in lower legs. At thigh level, the anterior compartment was usually the most affected region with the rectus femoris relatively spared. 79.2% of DM1 patients had edema in lower limb muscles. The total mean score of fatty infiltration correlated with MIRS grading, age and disease duration but did not correlate with the age of onset or CK level.Conclusion: Here, we found fatty infiltration present in most Chinese DM1 patients with a selective involvement pattern. There is a correlation between the total mean score of fatty infiltration and MIRS grading, age and disease duration.