Epidemiologic and clinical characteristics of neuromyelitis optica spectrum disorder patients, A seven years follow-up study from Iran.

Background: Neuromyelitis Optica Spectrum Disorder (NMOSD) is a rare neuroinflammatory disease characterized by recurrent relapses. The most common signs are myelitis and optic neuritis. It can also present by cerebral or brain stem syndromes. There are still many challenges in its diagnosis and treatment, and long-term follow-up studies are needed to see the disease course over time.

Methods: We established an electronic registration system of NMOSD patients starting from October 2015 in Kashani hospital, Isfahan, Iran. Every suspected patient was documented and included in the follow-up system to survey their disease course. Anti-aquaporine 4 (AQP4) antibody checked for all by cell-based assay method. All information such as demographic and clinical data and laboratory and MRI findings were documented. Participants were followed up for any relapses, new paraclinical tests and drug changes. This study is based on the definite NMOSD cases (according to the 2015 criteria) characteristics and clinical course during 7 years of registration.

Results: The study included 173 NMOSD cases and 56 ones were seropositive for AQP4 Ab. Their mean age was 40.02±11.11 years (45.78 in the seropositive group). The mean age at disease onset was about 30.16 years. The mean time of follow-up by our registration system is 55.84 ± 18.94 months (54.82 months in seropositive ones). The annual relapse rate is estimated as 0.47±0.36. Long extended transvers myelitis (LETM) was present in the baseline MRI of 77 patients (44.5%), while 32 of them did not show any related clinical symptoms. 124 patients revealed an abnormality in the first brain MRI. 27 individuals suffer hypothyroidism as the most common comorbid disease. The disease seems to be more prevalent in the west and southwest areas of Isfahan province.

Conclusion: The mean age of onset is higher than Multiple Sclerosis (MS) patients, but there are notable pediatric cases too. It should also be noticed that cervical LETM can be asymptomatic at first. Brain MRI abnormalities are frequently observed. The disease is more prevalent in the geographical areas where showing high MS prevalence.