Aquaporin-4 Antibody–Positive Cases Beyond Current Diagnostic Criteria for NMO Spectrum Disorders

Sato et al. published an article in 2013 describing patients who were positive for aquaporin-4 (AQP4) antibody but who did not otherwise fit the criteria for neuromyelitis optica or neuromyelitis optica spectrum disorders. Being AQP4 antibody-positive is a strong indicator that one has NMO or NMOSD, but NMO is also associated with “single or recurrent events of longitudinally extensive myelitis (3 vertebral segment spinal cord lesion seen on MRI) and recurrent or simultaneous bilateral optic neuritis.” They looked at the medical results of 298 consecutive patients who presented to Tohoku University Hospital in Japan with inflammatory central nervous system disorders. They then compared those who were positive for AQP4 antibody who did not fit the criteria for NMOor NMOSD, with those who were also AQP4 antibody-positive but who did fit the criteria for NMO or NMOSD. 72 of the 298 patients were AQP4 antibody-positive, and of these patients, 45.8% fit the criteria for NMO, 36.1% had some characteristics associated with NMOSD while18.1% of the patients did not fall into the NMO or NMOSD diagnostic category. More than half (53.8%) of the patients who were AQP4 antibody-positive did not fit into the diagnostic criteria for NMO or NMOSD and had monophasic optic neuritis, while 30.8% of them had lesions less than three vertebral lengths, and 15.4% had attacks solely in the brain stem. These patients had fewer attacks, lower levels of AQP4 antibody, and a lower disability score than patients who had NMO or NMOSD. Yet, there was a significant overlap in clinical and demographic features that suggested the presence of anti-AQP4 antibodies could be used to define a disease with variable presentations. As a result of this study, Sato et al. suggest that patients with AQP4 antibody positivity who have one or more attacks of optic neuritis, myelitis (whether short or longitudinally extensive), and/or brainstem involvement should be diagnosed with NMOSD and receive immunosuppressants.

This summary was written by Gabrielle (GG) deFiebre, Research Associate at a Public Health non-profit in New York City who was diagnosed with Transverse Myelitis in 2009. GG volunteers with the Transverse Myelitis Association.

Original research: Sato DK et al. Aquaporin-4 antibody–positive cases beyond current diagnostic criteria for NMO spectrum disorders. Neurology. 2013;80:2210-2216.