AQP4 and optic neuritis: All 13 patients with AQP4-IgG-positive NMOSD experienced their first clinical attack (i.e., onset episode) at the blood test, whereas 3 out of the 26 patients with MOGAD experienced an undiagnosed neurological episode (one with myelitis and two with optic neuritis) more than 10 years ago without subsequent relapse preventions.