BackgroundNeurofilament light chain (NfL) reflects axonal damage in neurological disorders. It has recently been evaluated in idiopathic intracranial hypertension (IIH). A biomarker indicating the severity of optic nerve damage in IIH could support diagnostic accuracy and therapeutic decisions.MethodsWe retrospectively reviewed NfL concentrations in the cerebrospinal fluid (CSF) of 35 IIH patients and 12 healthy controls, who had received diagnostic workup for IIH in our clinic. The diagnosis of IIH was made according to the modified Friedman criteria for IIH and for IIH without papilledema Friedman DI et al Neurol 81:1159–1165 (2013) [1]. NfL in the CSF (CSF-NfL) was correlated with the severity of papilledema and with CSF opening pressure.ResultsCSF-NfL correlated with CSF opening pressure at the time of collection. In patients with IIH and moderate or severe papilledema, CSF-NfL was significantly increased compared to patients with mild or no papilledema. Healthy controls with raised intracranial pressure showed no relevant elevation of CSF-NfL.ConclusionCSF-NfL appears to correlate with the severity of papilledema in IIH and with CSF opening pressure and may therefore be a predictor of optic nerve damage in IIH patients.