MOG and multiple sclerosis: In fact, 50 % of the MOG-IgG-positive patients in this study had clinical or radiological involvement of the brain in addition to ON and/or myelitis and the Barkhof and McDonald criteria for multiple sclerosis (MS) were met by 15 % and 33 %, respectively, as shown in parts 2 and 3 of this series [36, 37].