P.207 Muscle magnetic resonance imaging in Myotonic dystrophy type 1: Longitudinal study for 5 years

Abstract

Myotonic dystrophy type 1 is the most common genetic muscle disease in adults, caused by increased expansion of CTG repeats in the DMPK gene. It is characterized by progressive distal dominant muscle weakness and myotonia. The aim of this study was to evaluate objective longitudinal changes in the muscle magnetic resonance imaging in DM1 patients over five years. Eighteen genetically diagnosed DM1 patients were enrolled at baseline. The mean age was 44.86±9.83, mean CTG repeat length was 465±328.86 and a disease duration of 18.29±9.43 years. The baseline motor function such as medical research council sum score, Muscular impairment rating scale and 6-minute walk test were evaluated at the baseline and after 5 years of follow up. The pulmonary function and serum creatine kinase levels were also evaluated. The muscle magnetic resonance imaging was performed at baseline and after 5 years. The individual muscles were semi-quantitatively graded using five-point Mercuri scores. The thirteen upper muscle groups and twenty one lower limb muscles were evaluated. The lower muscle groups including gluteus muscles. The fatty infiltrative changes progressed after 5 years of follow up, with significant score changes were most prominently observed in lower limb muscles including gastrocnemius, soleus, tibialis anterior, gastrocnemius and tensor fascia latae muscles. Among upper limb muscles, latissimus dorsi showed most significant fatty infiltrative changes, followed by serratus and rhomboid muscles. Bases on the longitudinal follow up of the muscle MRI, DM1 showed significant deterioration in the lower limb muscles, with prominent changes in the crural muscles. This is the first longitudinal muscle MRI study and more studies are warranted to understand muscle degeneration in DM1.