Seronegative Neuromyelitis Optica Spectrum Disorder: An Unusual Presentation of Acute Brainstem Syndrome.

BACKGROUND Neuromyelitis optica (NMO) is an autoimmune, demyelinating, inflammatory disorder affecting the central nervous system, mostly targeting optic nerves and the spinal cord. NMO spectrum disorder (NMOSD) is a newly revised nomenclature in which new diagnostic criteria have been developed, including serological testing of serum aquaporin-4 immunoglobulin G (AQP4-IgG) antibodies. Results of a negative antibody will group the patient in a seronegative subgroup.