Downbeat Nystagmus In Patient With AQP4-Positive Neuromyelitis Optica

Neuromyelitis optica (NMO) is characterized as a rare autoimmune inflammatory disease typically presenting with loss of vision and paralysis. NMO differentiates from other autoimmune diseases with antibodies selective for aquaporin-4 (AQP4), a water channel located within the optic nerves and spinal cord. It is hypothesized that AQP4-IgG can more readily enter the perivascular space rather than breaching the blood-brain barrier encountering AQP4 on the surface of choroid epithelial cells. Downbeat nystagmus (DBN) is associated with structural, metabolic, and autoimmune causes like multiple sclerosis. Clearly documented DBN is rarely reported in NMO.