Natural history of 441 cases of bulbar onset motor neuron disease (MND) in China: a single-center retrospective study.

OBJECTIVE: To describe the natural history and identify prognostic factors of bulbar onset motor neuron disease (MND). METHODS: Bulbar onset MND patients with regular follow-up between January 2014 and December 2023 were included. Clinical features at initial evaluation, duration from onset to next region and time to death or tracheotomy were retrospectively collected. Survival analysis was performed by Kaplan-Meier method and Cox regression model. RESULTS: A total of 441 patients were included. Disease progression occurred most frequently from bulbar region to upper limbs (77.1%), followed by lower limbs (16.4%) and respiratory muscles (6.5%), with a median time interval of 6.0 (1.0, 48.0) months. 215 patients died or underwent tracheotomy. The median duration to death or tracheotomy was 43.0 (95% CI 39.1-46.9) months, the 1-year, 2-year, 3-year, 4-year and 5-year survival rates (95%CI) were 96.6% (94.9-98.3), 79.9% (76.0-83.9%), 59.1% (54.0-64.7), 42.2% (36.6-48.6) and 29.9% (24.3-36.7), respectively. Younger onset age, slower ALSFRS-R decreasing rate, longer diagnostic delay, longer duration to next region and pure upper motor neuron involvement at initial evaluation were associated with favorable prognosis. Upper limbs involvement secondly to bulbar region was independently associated with better outcomes compared with respiratory muscles spreading. CONCLUSIONS: The natural history of bulbar-onset ALS exhibits substantial heterogeneity. Patients with only upper motor neuron involvement in bulbar region at onset and subsequent upper limbs involvement as the second region tend to have a favorable prognosis.