Axonal degeneration and inflammation in acute optic neuritis

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 ( NfH(SMI35); 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 NfH(SMI35) values than controls (0.17 versus 0.005 ng/ml; p< 0.05) and higher NOx values (49 versus 35.5 mu M; p< 0.001). Plasma NfH(SMI35) values correlated inversely with visual acuity at presentation ( R = -0.67; p = 0.01). NfH(SMI35) 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 NfH(SMI35) and high NOx values experienced a poor recovery as opposed to only one of five with high NOx but normal NfH(SMI35) values. Conclusions: NfH(SMI35), a surrogate marker for axonal damage, is a prognostic indicator and should be considered in the design of neuroprotective treatment strategies.