White matter (WM) tract disruption accounts for a small percentage of atrophy in connected subcortical gray matter in multiple sclerosis (MS) when controlling for overall disease burden and is not the primary driver in most cases. This according to a recent study that sought to cross-sectionally and longitudinally characterize the unique impact of focal WM damage on the atrophy of connected subcortical gray matter regions, beyond what is explainable by global disease progression. 176 individuals with MS and 47 healthy controls underwent MR imaging at baseline and 5 years later. Atrophy and lesion-based disruption of connected WM tracts were evaluated for 14 subcortical gray matter regions. Researchers found:

• When controlled for whole-brain volume and T2-lesion volume, WM tract disruption explained little additional variance of subcortical gray matter atrophy and was a significant predictor for only 3 of 14 regions cross-sectionally (ΔR²=0.004) and 5 regions longitudinally (ΔR²=0.016).
• WM tract disruption was a significant predictor for even fewer regions when correcting for multiple comparisons.