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. CASE REPORT We describe the case of a 27-year-old female who presented to our hospital with new onset of sudden unexplained vomiting, dysphagia, dysphonia, and food regurgitation. Extensive investigations were done and brain magnetic resonance imaging (MRI) showed a small nonspecific area of signal abnormality in the right dorsal medulla. Aquaporin-4 antibodies were negative, and the patient was diagnosed with seronegative NMOSD with acute brainstem syndrome after meeting the diagnostic criteria. The patient's condition improved after steroids administration. CONCLUSIONS We report an unusual presentation of seronegative NMOSD presenting with acute brainstem syndrome.