Background: Neuromyelitis Optica (NMO) is a demyelinating disease of the central nervous system which preferentially involves the optic nerve and the spinal cord. This is the first inflammatory disease of the CNS in which a specific antibody (NMO-IgG) has been detected. However, even if NMO-IgG positivity has high sensitivity and specificity its prognostic value has yet to be determined. Methods: We retrospectively collected patients affected by NMO according to 2006 revised criteria attending S. Raffaele Hospital from January 2009 to March 2010. All clinical, neuroradiological, neurophysiological and immunological characteristics were recorded. Results: we recruited 29 patients (26 females). Mean age at onset and disease duration were 33 years and 9 years respectively. The second attack occurred after a mean interval of 1,3 years (range 0,2-10) whereas the sentinel event developed after 3 years (range 0-26). Optic Neuritis was the presenting symptom in 55% of patients. Brain MRI abnormalities were present in 50% of patients at the end of follow-up. Mean EDSS at the end of follow-up was 5,3 and 48% of patients reached an EDSS of 6.0. after a mean time of 6,8 years. Mortality rate was 7%. The proportion of NMO-IgG positive patients was 76%. We found that NMO-IgG positive patients showed a significant higher EDSS at the end of follow-up (5,7 vs 2,4 p< 0,05). Moreover, no NMO-IgG negative patients reached an EDSS of 6.0 at the last follow-up evaluation versus the 58% of NMOIgG positive patients (p< 0,05). Neither the presence of brain abnormalities, nor the symptoms at onset were predictive of the disease severity. Finally, the patients with age at onset > 40 years showed a worse response to high dose i.v. steroids.
Conclusions: Our study confirms that NMO is a severe disease: about 50% of our patients were unable to walk without assistance after 6 years from disease onset. The NMO-IgG prevalence found in our patients was 76%, confirming the importance of this antibody in the diagnosis of Devic disease. Moreover, our study has shown a significant association between NMO-IgG + status and the severity of the disease suggesting that this antibody can be also considered a prognostic marker of disease severity.
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