Material and Method: Conventional MRI and DWI were performed in 37 multiple sclerosis patients and 31 control subjects, matched for age and sex. Quantitative diffusivity values were obtained from variable locations of normal appearing white and gray matter from both hemispheres by using a standardized region of interest template.

Results: Mean diffusivity was higher in both normal appearing white matter (NAWM) and normal appearing gray matter (NAGM) of MS patients (mean + SD: 85.71 x 10-5 + 2.9 x 10-5 mm2/s and 85.90 x 10-5 + 2.45 x 10-5 mm2/s) than normal control subjects (NAWM: 73.46 X 10-5 + 1.77 x 10-5 mm2/s and NAGM: 82.90 x 10-5 + 0.91 x 10-5 mm2/s ) with p-value < 0.0001.

Conclusion: Water diffusivity was higher in all NAWM regions, deep gray matter regions, and some cortical gray matter region of MS patients than normal controls. DWI can quantify the presence and extent of MRIundetectable pathology in the normal appearing brain tissue that were the disease burden.

Keywords: Diffusivity, Multiple sclerosis (MS), Diffusion-weighted imaging (DWI), Normal appearing white matter (NAWM), Normal appearing gray matter (NAGM)