Normal-appearing white and grey matter damage in MS: A volumetric and diffusion tensor MRI study at 3.0 Tesla

The aims of this study were to improve, using a 3.0 Tesla (T) scanner and diffusion tensor (DT) magnetic resonance imaging (MRI) with sensitivity encoding, our understanding of: 1) the possible pathological substrates of normal-appearing white matter (NAWM) and grey matter (GM) damage in multiple sclerosis (MS) and 2) the factors associated to WM and GM atrophy in this condition. Conventional and DT MRI of the brain were acquired from 32 relapsing-remitting (RR) MS patients and 16 controls. Lesion load, WM (WMV), overall GM (GMV), and neocortical GM (NCV) volumes were measured. NAWM mean diffusivity (MD) and fractional anisotropy (FA), and GM MD were calculated. GMV and NCV were lower (p ≤ 0.001) in MS patients than controls, whereas WMV did not differ significantly. MS patients had higher NAWM and GM average MD and lower NAWM average FA (p ≤ 0.001) than controls. Moderate correlations were found between intrinsic lesion and tissue damage with both GM volumetric and diffusivity changes (-0.41 ≤ r ≤ 0.42, p ≤ 0.04). DT MRI and volumetry measurements at 3.0 T confirm the presence of NAWM and GM abnormalities in RRMS patients. Although histopathology was not available, axonal and neuronal damage and consequent reactive glial proliferation are the most likely substrates of the changes observed.