Abstract: A method for determination of an indicator representative of a change in the brain caused by a demyelinating disease, the method including, for each region of interest of the brain, determining a regional coefficient of one of the following diffusion coefficients: the radial diffusion, the axial diffusion, the mean diffusion, the anisotropy fraction, or a combination of several of these coefficients, the regional coefficients being determined from a diffusion MRI image; determining a number of changed regions, for which a condition relating to the value of the regional diffusion coefficient of each region is satisfied; and determining the indicator in accordance with the number of changed regions.