To characterize the clinical, CSF and MRI features associated with spinal cord leptomeningeal enhancement (sLME) in children with myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD).

Leptomeningeal inflammation has been recently reported in children with MOGAD as evidenced by enhancement of the spinal leptomeninges on post-contrast MRI. Whether sLME is associated with disease severity in MOGAD myelitis is unknown.

We included participants in the prospective Canadian Pediatric Demyelinating disease study with evidence of spinal lesion(s) on MRI, and for whom both gadolinium-enhanced MRI and serum MOG-IgG testing results were available. We compared clinical and MRI findings between participants with MOGAD myelitis and seronegative monophasic myelitis with and without evidence of sLME.

We included 33 children with MOGAD myelitis and 45 with seronegative monophasic myelitis. Spinal cord LME was observed in 20/33 children with MOGAD and in 13/45 children with seronegative myelitis.  Among children with MOGAD, sLME associated with higher frequency of longitudinally extensive lesions (95 vs 62%), H sign (75% vs 38%), spinal cord tumefactive lesions (50% vs 8%), complete cross-sectional involvement (80% vs 38%), nodular enhancement (35% vs 0%) and more spinal lesions (median 2 vs 1), (all p<0.05). No significant differences were found in the frequency of CSF oligoclonal bands (21% vs 13%). Only 5 children with MOGAD, all with sLME, experienced clinical relapses, while no relapses were reported among the 33 MOGAD children without sLME (p=0.13). Among children with seronegative myelitis, sLME associated with more spinal cord tumefactive lesions (40% vs 13%) and complete cross-section involvement (79% vs 42%) (all p<0.05).

Spinal cord LME, irrespective of MOG-IgG status, associates with more extensive spinal cord lesion severity (as defined by more extensive cross-sectional involvement and a tumefactive cord lesion appearance). The mechanism behind this association might provide insights into determinants of outcome and deserves further studies.