Diffusion-weighted imaging correlates of cognitive dysfunction in relapsing-remitting multiple sclerosis

Introduction. Conflicting results have been obtained when studying the imaging correlates of cognitive dysfunction in multiple sclerosis (MS). Diffusion-weighted imaging (DWI) provide metrics which are sensitive to the macro- and microscopic MS lesion burden. We assessed the correlations between various metrics derived from DWI and the presence and severity of cognitive impairment in patients with relapsing-remitting (RR) MS. Materials and methods. T2, T1 and DWI scans of the brain were obtained from 31 RRMS patients. All subjects also underwent a complete battery of neuropsychological tests exploring memory, attention and frontal lobe cognitive domains. Seven patients were found to be cognitively impaired. We measured T2 and T1 lesion volumes (LV) and obtained diffusivity (D) histograms from the whole brain tissue (WBT), the normal-appearing brain tissue (NABT), the white matter (WM) and the gray matter (GM). Results. T2 LV, Tl LV and average D values were not significantly different between cognitively unimpaired and impaired patients. Significant, inverse correlations were found between symbol digit test scores and T2/T1 LV and average WBT/NABT/WM/GM-D values, as well as between semantic fluency test scores and average WBT/NABT/GM-D values (r values ranged from -0.35 to -0.48). Conclusions. DWI provides quantitative metrics that are correlated with the severity of attention and frontal lobe deficits in patients with RRMS.