CSF neurofilament light chain is elevated in OMS (decreasing with immunotherapy) and other pediatric neuroinflammatory disorders

•CSF NFL was the only one of 7 brain cell-specific markers elevated in untreated OMS.•During multimodal immunotherapy, the concentration dropped to control concentrations.•Astroglial markers were normal and unchanged by the same immunotherapies.•This is the first biochemical evidence of neuronal/axonal injury in some OMS.•Other pediatric neuroimmunological disorders had the highest CSF NFL concentrations.

Using a panel of seven brain cell-specific biomarkers in cerebrospinal fluid (CSF), pediatric opsoclonus–myoclonus syndrome (OMS) (n = 234) was compared to pediatric non-inflammatory neurological controls (n = 84) and other inflammatory neurological disorders (OIND) (n = 44). Only CSF NFL was elevated in untreated OMS versus controls (+ 83%). It was 87% higher in OIND than in OMS. On combination treatment with front-loaded ACTH, IVIg, rituximab, median CSF NFL decreased by 60% to control levels. These biochemical data suggest neuronal/axonal injury in some children with OMS without indicators of astrogliosis, and reduction on sufficient immunotherapy.