Objectives: To evaluate the spectrum of neuromyelitis optica (NMO), including characteristics of the index events (optic neuritis [ON]) and myelitis), neuroimaging, CSF, and serologic studies, and to evaluate the long-term course.
Methods: Review of 71 patients with NMO evaluated at the Mayo Clinic between 1950 and 1997.
Results: NMO was either monophasic or relapsing. Patients with a monophasic course (n = 23) usually presented with rapidly sequential index events (median 5 days) with moderate recovery. Most with a relapsing course (n = 48) had an extended interval between index events (median 166 days) followed within 3 years by clusters of severe relapses isolated to the optic nerves and spinal cord. Most relapsing patients developed severe disability in a stepwise manner, and one-third died because of respiratory failure. Features of NMO distinct from "typical" MS included >50 cells/mm3 in CSF (often polymorphonuclear), normal initial brain MRI, and lesions extending over three or more vertebral segments on spinal cord MRI.
Conclusions: Clinical, laboratory, and imaging features generally distinguish neuromyelitis optica from MS. Patients with relapsing optic neuritis and myelitis may have neuromyelitis optica rather than MS. Patients with a relapsing course of neuromyelitis optica have a poor prognosis and frequently develop respiratory failure during attacks of cervical myelitis.