BACKGROUNDDespite the large scale technical innovations that have been made, a number of patients with neuromyelitis optica (NMO) are lacking NMO-IgG in both serum and cerebrospinal fluid. Longitudinally extensive spinal cord (LESC) lesions and linear lesions are associated with NMO. However, differences of spinal cord magnetic resonance imaging (MRI) features, including LESC lesions and linear lesions, between NMO-IgG positive and negative patients still remain unknown. The aim of the present study was to analyze the relationship between NMO-IgG status and spinal cord MRI features in NMO patients, particularly concerned about LESC lesions and linear lesions.

METHODSClinical data and spinal cord MRI of 52 NMO patients were retrospectively analyzed. Eight patients were NMO-IgG negative in both serum and cerebrospinal fluid, while 44 were NMO-IgG positive. Quantitative data between the two cohorts were compared by the Student's t test or Mann-Whitney U test, the chi-square test or Fisher's exact test was used to evaluate qualitative data.

RESULTSNMO-IgG negative patients had a higher sex ratio (male/female) (P = 0.014). On axial MRI, lesions in the NMO-IgG negative group were mostly located in the peripheral cord (50%), and central lesions (55%) were more common in the NMO-IgG positive group (P = 0.051). LESC lesions were common in both cohorts. None of linear lesions was found in NMO-IgG negative patients, while the NMO-IgG positive cohort had significantly more linear lesions (48%) (P = 0.016).

CONCLUSIONSPatients with NMO-IgG negativity may have different spinal cord lesion features compared to NMO-IgG positive patients. Diagnosis of NMO cannot be excluded even when NMO-IgG negativity and non-specific spinal lesions occur.