Background Neuromyelitis optica (NMO) is a relapsing inflammatory demyelinating disorder associated and mediated by aquaporin–4 antibody (AQP4–Ab), affecting predominantly the optic nerves, spinal cord (as longitudinally extensive myelitis) and often the brainstem. Relapses of NMO are usually severe and disabling. Respiratory failure, often due to brainstem or high cervical cord involvement, is a feared complication of NMO. We aimed to determine the causes and frequency of respiratory failure in NMO.

Methods Retrospective medical record review of all patients with a diagnosis of NMO fulfilling criteria (2006) seen by the Walton Centre NMO service, UK till March 2012, were reviewed.

Results We identified 85 patients (66 women, 69 with AQP4–Ab) with a median age of 51 (13.1–80.9) years. Between them they had 417 relapses over their disease course. Respiratory dysfunction that occurred after onset of NMO was reported in 19/85 (22.3%, 16 women, 17 with AQP4–Ab) patients. In 14/85 patients (16%) of these patients it was related to a relapse. This accounted for 3.36% (14/417) of all relapses. 6/85 (7%) patients required invasive ventilation. One patient died during the brainstem relapse.

Conclusions Though only a minority of relapses in NMO cause respiratory failure, about 20% of all NMO patients, will have some respiratory dysfunction during the course of their illness.