- Last Update On : 2013-10-28
Neuromyelitis optica (NMO), also known as Devic's disease and optic-spinal multiple sclerosis, is a severe idiopathic inflammatory demyelinating disease that selectively affects optic nerves and the spinal cord. It typically spares the brain, and generally follows a relapsing course. Within 5 years, 50% of patients lose functional vision in at least 1 eye or are unable to walk independently. In North America, the proportion of nonwhite individuals is higher among patients with NMO than among those with classic multiple sclerosis.
Many patients with NMO are misdiagnosed as having multiple sclerosis. Accurate diagnosis is important because prognosis and treatment for the two diseases differ. NMO typically has a worse outcome than multiple sclerosis due to early and frequent relapses. NMO is treated with immunosuppression while multiple sclerosis is treated with immunodulation. Plasmapheresis is more beneficial for patients with NMO than for those with multiple sclerosis.
Early diagnosis and treatment are important to reduce the morbidity of NMO. Patients with NMO produce an antibody to aquaporin-4, a water channel protein located in astrocytes. Seropositivity for NMO autoantibody IgG (NMO-IgG) allows early
diagnosis of NMO (73% positive; 91% specific). NMO-IgG is uniformly negative inpatients with classical multiple sclerosis. A positive value is consistent with NMO or a related disorder and justifies initiation of early immunosuppressive therapy.
Approximately 40% of adult patients with longitudinally-extensive transverse myelitis are seropositive for NMO-IgG, while approximately 15-20% of patients with multiple episodes of optic neuritis test positive. Seropositive patients are much more likely to relapse or progress within 2 years than seronegative patients. Seronegativity does not exclude the diagnosis of NMO. Patients already treated with immmunosuppressive therapy may not have detectable antibody.