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Patients with recurrent optic neuritis who are seropositive for NMO-IgG are at high risk for poor visual outcome and the development of neuromyelitis optica, research shows.

Patients with recurrent optic neuritis who are seropositive for the autoantibody neuromyelitis optica-immunoglobulin G (NMO-IgG) are at high risk for poor visual outcome and the development of neuromyelitis optica, research shows.

"Therefore, we advocate testing patients with recurrent optic neuritis for NMO-IgG and favor use of immunosuppressive therapy in treating NMO-IgG seropositive patients with recurrent optic neuritis, as we also recommend for patients with longitudinally extensive transverse myelitis who are NMO-IgG seropositive," conclude researchers in a report of the study in the June 3 issue of Neurology.

The research team, based at the Mayo Clinic in Rochester, Minnesota and Scottsdale, Arizona, notes that NMO-IgG is a biomarker for neuromyelitis optica and relapsing transverse myelitis. "Recurrent optic neuritis may herald multiple sclerosis or neuromyelitis optica, or it may occur as an isolated syndrome."

Dr. Brian G. Weinshenker and colleagues evaluated 34 patients who were tested for NMO-IgG and who had two or more episodes of optic neuritis without satisfying a diagnosis of MS or neuromyelitis optica prior to serologic testing.

Analyses focused on 25 Mayo Clinic patients (five NMO-IgG-positive and 20 NMO-IgG-negative) and nine seropositive patients whose serum was referred to the Mayo Clinic Neuroimmunology laboratory for testing.

Dr. Weinshenker, at Mayo Clinic Rochester, and colleagues found that 20 per cent of the patients with recurrent optic neuritis were NMO-IgG-positive. All NMO-IgG-positive patients (versus 65 per cent of NMO-IgG-negative patients) had at least one attack with visual acuity in the affected eye worse than 20/200 (p = 0.05).

After a median follow-up of 8.9 years, six of 12 patients (50 per cent) presenting with recurrent optic neuritis who tested positive for NMO-IgG went on to have an episode of myelitis and fulfill diagnostic criteria for neuromyelitis optica, compared with only one of 15 seronegative patients (7 per cent).

Consistent with prior studies, the NMO-IgG-positive patients had a poorer visual outcome than the NMO-IgG-negative patients (p = 0.02).

In an editorial, Dr. Gavin Giovannoni from The Royal London Hospital, UK, says that based on this study and others, and given that NMO-IgG assays have become more widely available, "I would advocate routine testing for NMO-IgG or anti-APQ4 antibodies in patients presenting with recurrent or bilateral optic neuritis, poor recovery from unilateral isolated optic neuritis, longitudinal extensive transverse myelitis, or unexplained acute brainstem or hypothalamic syndromes with appropriate changes on imaging."

Neurology 2008;70:2192-2193,2197-2200