AQP4 and Autoimmunity: Such descriptive nomenclature would distinguish between AQP4-Ab-positive NMO and AQP4-Ab-negative NMO, AQP4-Ab-positive and AQP4-Ab-negative (longitudinally extensive) myelitis, AQP4-Ab-positive and AQP4-Ab-negative optic neuritis, AQP4-Ab-positive and AQP4-Ab-negative brainstem encephalitis, etc. In addition, the disease course (monophasic/first attack, relapsing) should be specified and information should be provided regarding co-existing autoimmunity as well as regarding the suspected aetiology in seronegative patients.