Proceedings of the 25th BCTRIMS Annual Meeting

Introduction: Neuromyelitis Optica Spectrum Disorder (NMOSD) is a leading cause of Longitudinally Extensive Transverse Myelitis (LETM). Due to advancements in early diagnosis and treatment, NMOSD mortality has declined. However, mortality data for patients with first-episode LETM are scarce. Objective: To assess final diagnosis, and long term prognosis of patients with first-episode LETM. Methods: This is an observational retrospective study involving all consecutive patients diagnosed with longitudinally extensive myelopathy who were sequentially referred to the clinical neurology department of a brazilian tertiary hospital between January 2005 and December 2011. Only patients meeting the criteria for the first episode of idiopathic LETM were included. Data were retrieved from electronic medical records from October 2023 to January 2024. Statistical analysis used Mann-Whitney and Fisher's exact tests in R Studio. Results: 39 patients met the inclusion criteria. After a median 12-year follow-up, the final diagnoses were as follows: 51% isolated monophasic seronegative LETM, 28% NMOSD AQP4-IgG positive, 7.7% NMOSD AQP4-IgG negative, 5% myelin oligodendrocyte glycoprotein antibody associated disease, 5% recurrent seronegative LETM and 2.6% multiple sclerosis. The mortality rate was 10% at the end of the follow-up, with a median (m) time to death of 3 years and deceased patients had a higher age at onset of LETM (m=56; IQR=42-69; OR=1.09, 95% CI=1.01-1.21, p=0.043). Among survivors, 17% had an Expanded Disability Status Scale (EDSS) greater than or equal to 7 at the last clinical follow-up. Predictors of severe sequelae included higher EDSS at nadir (m=8.5; IQR=8.5-8.88; OR=5.29; 95% CI=1.38-39; p= 0.011), pain as an initial myelitis symptom (83%; OR=11.1; 95% CI=1.51-230; p = 0.028), and spinal shock during the first myelitis (100%; p < 0.001). Conclusion: In this cohort,  half of the patients remained as isolated monophasic seronegative LETM, mortality reached 10% and 83% of survivors were ambulatory after a median 12-year follow. Prognostic factors included age, pain, and initial severity.