Neuromyelitis optica and AQP4 antibodies in consecutive optic neuritis patients

Abstract

Abstract Purpose To analyse the frequency of neuromyelitis optica (NMO) among consecutive optic neuritis (ON) patients in Southern Finland and to analyse correlation of Aquaporin‐4 (AQP4) antibody titre with the severity of ON and with the diagnosis of NMO. Methods All patients with symptoms suggestive of acute ON and treated in the Helsinki Eye Hospital have been screened for AQP4 antibodies from May 2008 onwards. Diagnosis of NMO among the ON patients was evaluated prospectively and retrospectively. AQP4 antibodies were measured using Radioimmunoprecipitation assay (Seelig‐lab). Antibody titres >15 were considered pathological, 10‐15 borderline, and <10 were considered normal. Brain magnetic resonance imaging (MRI) was performed in all patients. Results We screened 131 patients who had symptoms suggesting ON. Of the 131 patients 24 (18%) were eventually diagnosed with a condition other than ON. Of the remaining 107 patients classified as ON (77% females), 35 (33%) had multiple sclerosis (MS), 25 (23%) had demyelination by MRI, but did not fulfill the criteria for MS, and 47 (44%) had no MRI evidence of demyelination. The median AQP4 anti‐body titer was 7.3 (range 4.8‐53.5). Pathological AQP4 antibody titres were found in three cases, one with NMO, one with MS and one with a clinically isolated syndrome suggestive of MS fulfilling Barkhof’s MRI criteria. Borderline AQP4 antibody titres were found in 8 cases. Only one patient with NMO was found and he had pathological AQP4 antibody titer. Conclusion In the southern Finnish population, NMO is rare among ON patients. In this cohort the AQP4 antibody test was not specific for NMO.