Using magnetization transfer (MT) and diffusion tensor (DT) MRI, the authors assessed the extent of tissue damage of the brain normal-appearing white and gray matter (NAGM) in patients with neuromyelitis optica (NMO). Compared to healthy controls, patients with NMO showed reduced MT ratio and increased mean diffusivity of the NAGM. This challenges the classic notion of a sparing of the brain tissue in the course of NMO.