Spinal cord lesions and atrophy in NMOSD with AQP4-IgG and MOG-IgG associated autoimmunity

Background: Spinal cord (SC) affection is a hallmark symptom of neuromyelitis optica spectrum disorders (NMOSD). Patients with aquaporin-4 (AQP4-IgG+) or myelin oligodendrocyte glycoprotein (MOG-IgG+) antibody seropositivity show this overlapping clinical phenotype. Objective: Quantitative comparison of SC lesions and atrophy in AQP4-IgG+ and MOG-IgG+ NMOSD. Methods: AQP4-IgG+ (n=38), MOG-IgG+ (n=15) NMOSD patients and healthy controls (HC, n=24) were analysed for SC lesion (prevalence, length, location), atrophy as mean upper cervical cord area (MUCCA), Expanded Disability Status Scale (EDSS), timed 25-foot walk speed (T25FWS) and 9-hole peg test (9HPT) measures. Results: In total, 92% (35/38) of AQP4-IgG+ and 53% (8/15) of MOG-IgG+ patients had myelitis attacks (chi(2)=6.47, p=0.011). 65.8%/26.7% of AQP4-/MOG-IgG+ patients had chronic SC lesions (chi(2)=5.16, p=0.023), with similar proportions in cervical, upper thoracic and lower thoracic cord, and no length differences. MUCCA was decreased in AQP4-IgG+ (t=-2.27, p=0.028), but not MOG-IgG+ patients (t=0.58, p=0.57) compared to HC. MUCCA associated with myelitis attacks (rho=-0.33, p=0.016), EDSS (rho=-0.31, p=0.030), pyramidal functional score (rho=-0.42, p=0.003), T25FWS (r=0.43, p=0.010) and 9HPT Z-score (r=0.32, p=0.037), regardless of antibody status. Conclusion: AQP4-IgG+ patients had more myelitis attacks, SC lesions and SC atrophy was more pronounced than in MOG-IgG+ patients. MUCCA is associated with clinical myelitis attacks and disability in all NMOSD patients.