Neuromyelitis optica spectrum disorder in Western Mexico

Neuromyelitis Optica Spectrum Disorders (NMOSD) are a group of inflammatory diseases of the Central Nervous System (CNS) that primarily affect the optic nerve and spinal cord, usually with a severe and relapsing course. Due to the scarce information in non-Caucasian populations, we aimed to describe incidence, prevalence, and main clinical characteristics of NMOSD in a defined region in Mexico.

Descriptive, retrospective analysis of all reported cases of NMOSD attended in the neurology department of the UMAE-HE, CMNO, IMSS, the biggest third level hospital in Western Mexico. We searched the electronic medical records of the hospital for patients with a diagnosis of NMO, and reviewed all cases to confirm if they fulfilled NMOSD 2015 diagnostic criteria. Data were collected through a structured form. We described adjusted incidence and prevalence according to the WHO method, for the IMSS affiliated total population in Jalisco state in 2019.

67 NMOSD patients were included in the analysis of clinical data, with a mean age at onset of symptoms of 36 years ((Rivera et al., 2008-65). Most patients were female (74.6%). 53 patients living in Jalisco by the end of 2019 were included in the analysis of prevalence and incidence. Adjusted prevalence was 0.71/100,000 (95% CI 0.55-0.92), while adjusted incidence was 1.87/1,000,000 person-years (95% CI 1.11-3.16). In the full cohort, the first symptom of NMOSD was optic neuritis in 49.3% of the patients, followed by transverse myelitis (23.9%) and area postrema syndrome (10.4%). 62 patients relapsed in a mean follow-up of 2 years (0-7). 5 patients with less than 6 months of follow up had not relapsed. 55.2% of the patients were AQP4-IgG +, 14.9% AQP4-IgG -, and 29.9% unknown status.

Although NMOSD prevalence is similar to other reports around the world, incidence is higher than in Caucasian populations. We believe that this high incidence is related to an increased awareness of the disease in the era of new NMOSD treatments. Recurrent disease is very frequent in our cohort.