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Neuromyelitis Optica Spectrum Disorder: the importance of the NMO IgG in clinical practice.

Multiple sclerosis: clinical aspects

Sunday, May 29, 2011, 12:00 – 13:00

Neuromyelitis optica spectrum disorder: the importance of NMO-IgG in clinical practice

M. Radaelli, V. Martinelli, L. Moiola, D. Privitera, D. Dalla Libera, M. Rodegher, B. Colombo, R. Fazio, R. Furlan, G. Comi (Milan, IT)

Background: Neuromyelitis Optica (NMO) is the first demyelinating disease of the CNS in which a specific biomarker has been found. The discovery of the antibody (NMO-IgG) has brought to consider NMO a syndrome (NMO Spectrum Disorder) which includes also limited forms of the disease such as Longitudinally Extensive Transverse Myelitis (LETM) and Recurrent Optic Neuritis (rON). The aim of our study was to characterize patients affected by optico-spinal diseases and to investigate the prognostic value of the NMOsd classification.
Methods: We collected patients affected by recurrent myelitis, rON or both with an onset brain MRI not fulfilling the criteria for MS. Patients that at the end of the investigations reached a diagnosis of MS or other alternative diagnosis were excluded by the study.
Results: We recruited 79 patients: compatible clinical findings and NMO-IgG positivity led to a diagnosis of NMO Spectrum Disorder (NMOsd) in 48 of these patients. The mean age of onset and the mean disease duration were 36 years and 7,5 years respectively. Twenty patients (42%) developed brain MRI lesions during the follow-up. A LETM was present in 80% of patients. After 6 years from the onset half of our patients showed a severe disability defined as an EDSS of 6 or a blindness in at least one eye. When we compared patients with a defined NMO (n=32) with patients with limited forms of the disease (n=16) we didn’t find any significant difference both in terms of baseline characteristics and in the clinical outcome except for an earlier age at onset. On the contrary when we compared our 48 patients with NMOsd with the other 31 patients of the original cohort with recurrent myelitis or rON who didn’t satisfy the criteria for NMOsd, we found that the first group presented a higher prevalence of female gender and a higher frequency of extensive spinal cord lesions. Moreover they showed a significant lower rate of response to the first immunosuppressive drug, a higher ARR, and a higher rate of severe disability.
Conclusion: Our study shows that limited forms of NMO such as LETM and rON share the same unfavorable outcome of Definite NMO and the use of NMO-IgG antibody allows identifying patients with a worse prognosis at early stages of the disease. NMO-IgG determination is strictly recommended in the presence of a first attack of Myelitis or Optic Neuritis and in the presence of a positive status an immunosuppressive therapy has to be start as soon as possible.

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