Treatment response, risk of relapse and clinical characteristics of Taiwanese patients with neuromyelitis optica spectrum disorder

Abstract

The long-term disease course and efficacy of maintenance therapies have rarely been investigated in Asian patients with neuromyelitis optica spectrum disorder (NMOSD). Medical records of patients fulfilling the 2015 International Consensus Diagnostic Criteria for NMOSD at three medical centers in Taiwan were systematically analyzed. Linear regression analysis was performed to investigate factors related to annualized relapse rate (ARR); survival analysis was used to estimate the relapse-free intervals among therapies. A total of 557 relapses affecting 648 regions (202 optic neuritis, 352 acute myelitis, and 94 brain syndromes) in 204 patients were analyzed during a follow-up period of 69.5 months (range, 1-420). Up to 36.1% of myelitis-onset patients and 24.0% of optic neuritis-onset patients exhibited a limited form disease, defined as having one or more relapses confined to the same region. The median ARR was significantly lower in patients with limited form disease than those with relapses involving multiple regions (0.30 vs. 0.47, respectively). An older age at disease onset was associated with a lower ARR (p=0.023). Kaplan-Meier analysis showed that the estimated time (months) to next relapse was longest in rituximab-treatment group (58.0±13.2), followed by immunosuppressant (48.5±4.8) or prednisone (29.6±4.6) groups, and shortest in those without maintenance therapy (27.6±4.2) (p=8.1×10-7). Limited form disease and older age at disease onset are associated with a lower relapse rate in NMOSD. Compared to no maintenance therapy, rituximab and immunosuppressant significantly reduce the relapse risks.