A recent study identified limitations in the Expanded Disability Status Score scale's ability to capture full disability spectrum in neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein-antibody-associated disease.
Vivien Häußler, MD
(Credit: UKE Hamburg)
The Neuromyelitis Optica Study Group (NEMOS) recently had a study published in Annals of Neurology that showed patients with seropositive and seronegative neuromyelitis optica spectrum disorder (NMOSD), as well as myelin oligodendrocyte glycoprotein-antibody-associated disease (MOGAD), had distinctive relapse-associated disability progression, with MOGAD showing a less severe disease course. These results highlighted the increasing awareness and improvement of treatment strategies that appear to ameliorate disease outcomes for these disorders.1
Among 483 patients, 298 had AQP4-IgG+ NMOSD, 52 had AQP4-IgG-/MOG-IgG- NMOSD, and 133 had MOGAD. Despite comparable annualized attack rates, disability milestones occurred earlier and after fewer attacks in patients with NMOSD compared with patients who had MOGAD. For the estimated median time to reach an Expanded Disability Status Score (EDSS) of 3, patients with AQP4-IgG+ NMOSD took 7.7 years (95% CI 6.6-9.6), patients with AQP4-IgG-/MOG-IgG- NMOSD took 8.7 years, and patients with MOGAD took 14.1 years (95% CI 10.4-27.6).
“We found that MOGAD takes a less aggressive overall disease course than NMOSD despite the lack of established treatment concepts. Interestingly, the subgroups of patients with AQP4-IgG+ and AQP4-IgG−/MOG-IgG− NMOSD had a very similar treatment profile, with rituximab and azathioprine being used most frequently used, but showed some differences in disability accumulation," senior author Vivien Häußler, MD, neurologists at University Medical Center Hamburg-Eppendorf, in Germany, and colleagues wrote.1
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In this study, the NEMOs group investigated an accumulation of disability in NMOSD and MOGAD in an evolving treatment landscape. The researchers aimed to recognize risk factors for the development of disability milestones in relation to disease duration, the number of attacks, and age. Data was ultimately analyzed from patients with NMOSD and MOGAD from the German Neuromyelitis Optica Study Group registry. Using the data, authors estimated risk factors and computed time to disability milestones, as defined by the EDSS2, in an applied survival analyses.
For an EDSS of 4, the estimated times were 11.9 years (95% CI 9.7-14.7) for AQP4-IgG+ NMOSD, 11.6 years (95% lower CI 7.6) for AQP4-IgG-/MOG-IgG- NMOSD, and 20.4 years (95% lower CI 14.1) for MOGAD. To reach an EDSS of 6, it took 20.1 years (95% CI 16.5-32.1) for AQP4-IgG+ NMOSD, 20.7 years (95% lower CI 11.6) for AQP4-IgG-/MOG-IgG- NMOSD, and 37.3 years (95% lower CI 29.4) for MOGAD. Finally, the median time to reach an EDSS of 7 for patients with AQP4-IgG+ NMOSD was estimated as 34.2 years (95% lower CI, 31.1). Authors noted that higher age at onset increased the risk for all disability milestones and risk of disability decreased over time.
The current study has several limitations noted by the authors, including a small number of patients with high EDSS scores because of severe disability or death leading to loss of follow-up. Researchers noted that the EDSS itself has limitations, as it inadequately represents visual impairments and other functional disabilities, focusing mainly on mobility restrictions. Factors such as pain, cognitive changes, and mood were also not well-represented by the EDSS according to the authors. Additionally, the small cohort of patients with AQP4-IgG−/MOG-IgG− NMOSD limited the generalizability of these findings, and the recent differentiation of patients with MOGAD highlighted the need for further research and comprehensive diagnostic criteria. Lastly, the patient cohort underrepresented pediatric patients, especially those with acute disseminated encephalomyelitis.
“Despite a similar average time to reach disability milestones, AQP4-IgG−/MOG-IgG− NMOSD patients reached them with a larger number of attacks suggesting either less severe attacks or a better recovery in these patients. Moreover, we were able to extend the knowledge on the risk factors age and syndrome at manifestation, and to provide important evidence about the success of the scientific community to establish effective off-label treatment strategies in a rare disease,” Häußler et al noted.1
