P.13.5 Magnetic resonance imaging and spectroscopy detect changes with age, corticosteroid treatment, and functional progression in DMD.

Magnetic resonance imaging (MRI) and spectroscopy (MRS) show promise as unbiased non-invasive measures of disease progression in neuromuscular diseases. The ImagingDMD study is a longitudinal study that aims to validate the use of MRI and MRS at multiple sites in a large cohort of boys with Duchenne muscular dystrophy (DMD). To date, 121 boys with DMD, aged 5–14years, and 24 unaffected boys have completed baseline measures for this study. All boys could walk and climb stairs at the time of enrollment. The boys completed an MR exam that included MRI measures of muscle transverse relaxation time (MRI T2) and MRS measures of muscle composition (lipid: (lipid+water)) and the T2 of the water component of muscle (MRS T2). MRS T2 and MRI T2 are elevated by muscle damage, edema, and inflammation, and MRI T2 is also affected by intramuscular fat. Boys with DMD had greater MRI T2 (soleus (Sol): DMD 42.9±5.4ms, Con 33.6±1.6ms, vastus lateralis (VL): DMD 49.0±9.8ms, Con 34.2±2.2ms), MRS T2 (Sol: DMD 31.7±2.3ms, Con 28.2±0.6ms, VL: DMD 31.6±2.4ms, 29.0±0.8ms), and lipid: (lipid+water) (Sol: DMD 0.37±0.16, Con 0.22±0.08, VL: DMD 0.48±0.25, Con 0.20±0.07) than unaffected boys (p<0.001). While MRI T2 (VL: r=0.54) and lipid: (lipid+water) (Sol: r=0.39, VL: r=0.65) were positively correlated with age in boys with DMD, MRS T2 was negatively correlated with age (Sol: r=−0.30, VL: r=−0.32), possibly due to damage/edema in younger boys and increased fibrosis with disease progression. 26 boys with DMD were not taking corticosteroids, and had significantly greater MRS T2 and MRI T2 values than age-matched, corticosteroid treated boys. Boys also completed functional tests including the 6min walk test. These measures were significantly related to MRI T2 and lipid: (lipid+water) (R2 ranged from 0.12 to 0.41, with stronger correlations in VL). These cross-sectional data show that MRI and MRS can detect changes with age, corticosteroid treatment, and functional progression in DMD. [ABSTRACT FROM AUTHOR]