Chloride imbalance between serum and CSF in the acute phase of neuromyelitis optica.

We collected serum-cerebrospinal fluid (CSF)-paired samples during the acute phase of clinical episodes in MS and NMO patients, together with paired samples from non-MS/NMO patients, to compare the quotients of proteins and electrolytes among them. In NMO, the quotient of chloride was significantly higher in the acute phase of optic neuritis and brain lesions, but it was significantly lower in the acute phase of myelitis. Such findings were not observed in MS or in non-MS/NMO cases. With the coexistence of serum anti-AQP4-Ab, chloride imbalance between serum and CSF could be associated with the clinical episodes in NMO.