Characterizing double-negative neuromyelitis optica spectrum disorder: A meta-analysis

Neuromyelitis-optica spectrum disorders (NMOSD) usually associate with aquaporin-4 (AQP4) or myelin oligodendrocyte glycoprotein (MOG) antibodies. Seronegative-NMOSD (SN-NMOSD) has been described, but the clinical-therapeutic profile is poorly defined.We searched PubMed, Scopus and Google Scholar databases for studies reporting SN-NMOSD patients, on which anti-MOG-Abs and AQP4-Abs were tested. PRISMA guidelines and methodological quality control were assessed. Fixed or random-effects models were used to pool results across studies.We included 36/1027 articles screened and analyzed 591 SN-NMOSD patients (mean age: 30.3 [range 6-78]; female:male ratio; 2:1). Disease course was relapsing in 66% of cases. Brain MRI at onset showed brain abnormalities in 165/241 patients (69%) including tumefactive brain lesions in 19/241 (8%). Spinal cord MRI showed cervicothoracic lesions (99/241, 41%) and LETM (89/241, 37%). CSF analysis showed OCBs in 58/300 patients (19,3%). Mean annualized relapse ratio (ARR) was 0.77 (95%CI 0,10-1.8), and was higher in patients with late onset (>50 years, p<0.001). Mean EDSS and late-onset were associated with a relapsing course (p<0.05). Relapsing SN-NMOSD patients had a higher ARR and a worse outcome compared to AQP4-NMOSD or MOG-NMOSD. Among relapsing patients, 147/247 (60%) received a disease-modifying treatment (DMT). The administration of any DMT led to a reduction of ARR (pre-treatment: 0.83±0.21[95%CI 0.62–1.04, I^2=66.19%, p<0.0001]; post-treatment: 0.44±0.17[95%CI 0.27–0.60, I^2=85.81%, p<0.0001]).DN-NMOSD is a severe condition with distinctive features compared to AQP4-NMOSD. The administration of DMTs seems to be effective in this group of patients, but randomized clinical trials are needed.