Linking Downbeat Nystagmus and Aquaporin-4-Positive Neuromyelitis Optica: A Closer Look at Their Hidden Relationship.

Neuromyelitis optica (NMO), an autoimmune disease, typically presents with loss of vision and myelopathic signs. NMO may be associated with antibodies selective for aquaporin-4 (AQP4), a water channel located within the optic nerves and spinal cord.AQP4 is distributed in the periventricular region, corpus callosum, magnocellular nuclei of the hypothalamus, and brain stem.