Chloride imbalance is involved in the pathogenesis of optic neuritis in neuromyelitis optica.

Chloride imbalance between the serum and the cerebrospinal fluid (CSF) has been recently shown to exist in the acute phase of neuromyelitis optica (NMO). In this report, we studied the relation between the quotient of chloride (QCl) and the severity of optic neuritis (ON) in NMO patients. There was a positive correlation (R = 0.67; p < 0.05) between QCl and the length of ON-lesion. The visual prognosis also showed a positive correlation with QCl in the acute phase (R = 0.58; p < 0.05). These results support the theory that chloride imbalance between serum and CSF may trigger the ON in NMO spectrum disorders.