Predictive value of MRI parameters in severity and recovery of first-episode myelitis in aquaporin-4 antibody disease

•Cord lesions in NMO are usually cervicothoracic and involve central grey matter.•Total lesion length on MRI correlates with attack severity.•Lesion length on MRI does not predict eventual disability.•Cord atrophy is rare after a single myelitis attack in aquaporin-4 antibody disease.

BackgroundNeuromyelitis optica spectrum disorder (NMOSD) associated with aquaporin-4 antibodies (AQP4-Ab) typically causes longitudinally-extensive transverse myelitis (LETM). Few data exist about the association of MRI features with LETM attack severity and recovery.MethodsAQP4-Ab positive NMOSD patients with a first myelitis attack were retrospectively identified and spinal MRI scans reviewed. Association of MRI features with EDSS scores at attack nadir and recovery was evaluated.Results22 patients were included. Median nadir EDSS score was 8 (range 1 to 8.5). Nadir EDSS scores correlated with total MRI lesion length (r = 0.48, p = 0.025), higher scores were seen in those with gadolinium enhancement (p = 0.025) and there was a trend towards higher scores with central cord involvement. The median recovery EDSS was 6 (range 0 to 10). Total lesion length correlated with poor recovery (r = 0.48, p = 0.027) but this was confounded by correlation between nadir and recovery EDSS scores.ConclusionWe confirm that myelitis in AQP4-Ab disease is severe and show that the severity correlates with lesion length and residual disability. Spinal cord lesions in first myelitis attacks are similar to appearances reported later in the disease course, with propensity to involve the central grey matter and high frequency of cord oedema and T1 hypointensity.