Axonal degeneration and inflammation in acute optic neuritis

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Abstract
Aims: To investigate whether plasma biomarkers for axonal injury and inflammation are related to loss and recovery of visual function in acute optic neuritis (ON). Methods: Eighteen patients with ON and 14 controls were investigated in a longitudinal, prospective study. Plasma phosphorylated neurofilament heavy chain (NfHSMI35; a surrogate marker of axonal injury), nitric oxide metabolites (NOx), and citrulline (surrogate markers of inflammation) were measured. Results: Patients with ON had higher median plasma NfHSMI35 values than controls (0.17 versus 0.005 ng/ml; p < 0.05) and higher NOx values (49 versus 35.5μM; p < 0.001). Plasma NfHSMI35 values correlated inversely with visual acuity at presentation (R = −0.67; p = 0.01). NfHSMI35 was higher in patients with poor recovery of visual acuity than in those with good recovery (0.25 ng/ml versus 0.09 ng/ml; p < 0.05). Three of four patients with high NfHSMI35 and high NOx values experienced a poor recovery as opposed to only one of five with high NOx but normal NfHSMI35 values. Conclusions: NfHSMI35, a surrogate marker for axonal damage, is a prognostic indicator and should be considered in the design of neuroprotective treatment strategies.