Should most patients with optic neuritis be tested for neuromyelitis optica antibodies and should this affect their treatment?

Neuromyelitis optica (NMO) antibodies (aquaporin-4 antibodies) can be routinely tested and have become a major diagnostic criteria for NMO (1-4). These antibodies have recently been described in patients with isolated optic neuritis who do not have any neurologic symptoms and who do not fulfill the diagnostic criteria for NMO (3-5). However, recent studies have suggested that patients with isolated optic neuritis who have positive NMO antibody have a worse visual prognosis and more recurrences than those who are negative for NMO antibodies (5,6). Isolated optic neuritis with positive NMO antibodies might also be the first sign of NMO (3-8). However, it is still unclear whether NMO antibodies should be routinely tested in some or most patients with isolated optic neuritis. Indeed, whether positive NMO antibodies titers affect the management of patients with isolated optic neuritis remains debated.