Neuromyelitis optica IgG predicts relapse after longitudinally extensive transverse myelitis

Objective. We investigated whether neuromyelitis optica (NMO) IgG seropositivity at the initial presentation of longitudinally extensive transverse myelitis (LETM) predicts relapse of myelitis or development of optic neuritis. Methods: Prospective study of patients with initial LETM who were tested for the presence of NMO-IgG. Results: Eleven of 29 patients (37.9%) were seropositive after a first attack of LETM spanning three or more vertebral segments on magnetic resonance imaging. Of 23 patients followed up for I year, none of 14 who were seronegative experienced a relapse or developed optic neuritis. Of 9 scropositive patients, 5 developed a second event: 4 of 9 (44%) developed recurrent transverse myelitis and 1 of 9 (11%) developed optic neuritis (p = 0.004). Interpretation: LETM represents an inaugural or limited form of NMO in a high proportion of patients. The 40% of patients who are seropositive for NMO-IgG arc at high risk for relapse.