Nationwide population-based incidence and etiologies of pediatric and adult Horner syndrome

Purpose: To determine age- and sex-specific incidence and possible etiologies of pediatric and adult Horner syndrome in South Korea. Methods: A nationwide, population-based, cohort study using data from the Korean National Health Claims database from 2007 to 2018. All patients with Horner syndrome from the entire Korean population (n = 51,629,512) were included. To find possible causes of Horner syndrome, we searched concurrent codes for systemic diseases, trauma, or surgical procedures. Results: A total of 139 pediatric patients (59.7% male) and 1331 adults (51.0% male) were newly diagnosed as having Horner syndrome. The cumulative incidence was 2.12 (95% CI 2.08-2.17) per 100,000 pediatric population and 2.95 (2.94-2.96) per 100,000 adults. The peak incidence occurred at 0-4 years of age in the pediatric population, and at 50-54 years in the adult population. A total of 835 (56.8%) patients had underlying conditions or related surgical procedures associated with Horner syndrome. The underlying causes were recognized in 695 (83.2%) patients before the diagnosis of Horner syndrome, in 75 (9.0%) patients at the same time as the Horner syndrome diagnosis, and in 65 (7.8%) patients after the diagnosis of Horner syndrome. There were four cases of Horner syndrome that preceded neuroblastoma diagnosis. The most common tumor related with Horner syndrome was that of the thyroid in the adult population. Conclusions: This study determined the estimated incidence and possible causes of pediatric and adult Horner syndrome. As Horner syndrome with unknown etiologies may harbor serious malignancy, extensive evaluations are required, especially in children.restrictio