Downbeat Nystagmus in Patient with AQP4-positive Neuromyelitis Optica
Isabella Canut1, Blaire Cote2
1Philadelphia College of Osteopathic Medicine, 2General Pediatrics, University of Florida
Objective:
NA
Background:

Neuromyelitis optica (NMO) is a rare autoimmune inflammatory disease primarily characterized by vision loss and paralysis. What distinguishes NMO from other autoimmune conditions are its specific antibodies targeting aquaporin-4 (AQP4), a water channel found in the optic nerves and spinal cord. It is theorized that AQP4-IgG antibodies have an easier route to the perivascular space, interacting with AQP4 on the surface of choroid epithelial cells, rather than directly breaching the blood-brain barrier. Interestingly, well-documented cases of DBN in the context of NMO are rarely reported.

Presentation

A 33-year-old female with confirmed diagnosis of NMO presented with lower extremity pain, numbness, and loss of function, followed by staggered optic neuropathies in both eyes. Previous treatments included steroids, plasmapheresis, and inebilizumab-cdon. During physical examination, the patient exhibited central scotomas in both eyes, absent color vision, absolute atrophy in both eyes, saccadic tracking, but no nystagmus.

Twenty-three months later, the patient reported a sensation of the environment shifting, exacerbated by head movements. A follow-up physical examination revealed persistent poor vision (20/400 OD and 20/600 OS) and an oblique DBN more pronounced in left gaze than in right gaze. Brain and orbit MRI with contrast showed reduced caliber of the optic nerves and chiasm, with no notable abnormalities in total brain imaging.

Design/Methods:

NA

Results:
NA
Conclusions:

DBN has various underlying causes, and in our patient, it was a new development. AQP4-specific T cells are distributed throughout the CNS, with characteristic patterns of increased infiltration in NMO. These regions commonly include the optic nerves and the medulla.

NMO involves the brainstem, particularly the area postrema, leading to nausea, vomiting, or hiccups. These symptoms are believed to stem from lesions in the dorsal medulla. It's plausible that the higher expression of AQP4 in these regions enables increased binding of AQP4-IgG, resulting in activation of medullary cerebellar pathways.

10.1212/WNL.0000000000205381