Bo Chen1, Francis Anna2, Jacqueline Palace2
1Tongji Hospital of Tongji Medical College, Huazhong University of Science and Te, 2Clinical neurology, John Radcliffe Hospital, University of Oxford
Objective:
To quantify the contribution of clinical attacks to the irreversible disability in patients with aquaporin-4 antibody positive neuromyelitis optica spectrum disorder (NMOSD).
Background:
The clinical attack is primarily responsible for the disability in NMOSD, but research based on the irreversible neurological deficit and considering the intra-individual variations are scarce.
Design/Methods:
The data on each clinical attack (including the phenotype), repeatedly measured disability (by European Database for Multiple Sclerosis [EDMUS] score), and demographics were abstracted from the observational longitudinal Oxford cohort. Disability assessed more than 6 months following the previous episode was considered irreversible. A linear mixed-effects model with random intercepts for individual participants was employed to evaluate the contribution of attacks to the disability.
Results:
A total of 174 patients were included, with 26 having repeated EDMUS scores. The median time of disability measurement to the last attack was 41 months (range: 6 - 197 months). The EDMUS score was significantly associated with the number of attacks and the age at disease onset (both p values < 0.001), among which every attack contributed to a mean increase of 0.362 while age accounted for 0.066 annually. Besides, on average, male patients tended to achieve 0.759 scores lower than females (p < 0.080). No statistical difference was found between the white and non-white individuals in disability measurement. Further analysis showed that transverse myelitis (TM) contributed most to the EDMUS score, with an increase of 0.415 per attack (p < 0.001), followed by the brain/stem attack (0.302, p = 0.044), while optic neuritis (ON) had the least influence (0.212, p = 0.084).
Conclusions:
Clinical attacks, especially the TM and brain/stem episode, are the main contributors to the irreversible disability, while elderly people at onset may be more vulnerable to being disabled than younger individuals. This quantitative study may help clinicians to better predict the outcome of their patients.