Characterizing white matter hyperintensities in myotonic dystrophy type 1 through IVIM derived metrics

Myotonic dystrophy type 1 (DM1) is a genetic disease which affects multiple systems including the central nervous system. One of its key neuroimaging biomarkers are white matter hyperintensities (WMHs). The clinical relevance of WMHs remains unclear, and treating them as a uniform entity may overlook their heterogeneous composition and spatial distribution. To assess WMHs heterogeneity we applied intra-voxel incoherent motion (IVIM) modelling, an advanced magnetic resonance imaging technique, to a cohort of 23 patients with DM1 (age [mean ± std]: 44.1 ± 11.9 years; M/F = 8/15). WMHs were distinguished into periventricular (PWMHs) and deep (DWMHs) subtypes using criteria based on continuity and distance rules. A quantitative evaluation of their distribution among white matter tracts was conducted, together with correlation analysis between WMHs and clinical scales. Our research reveals that PWMHs have higher parenchymal diffusivity than DWMHs, consistently with their closeness to the ventricles. Significant positive correlation is identified between PWMH volumes and age, while DWMHs seem to be more strongly associated with an impairment of cognitive functions. Overall, these findings could have possible implications in clinics, highlighting the importance of considering WMHs heterogeneity and opening the door to a better comprehension of their role in the disease.