The risk of a serious etiology in pediatric Horner syndrome: indications for a workup and which investigations to perform.

PURPOSE:To report the risk of a serious etiology in a cohort of children with Horner syndrome without a known cause at presentation. METHODS:The medical records of children (<18 years of age) with Horner syndrome of unknown etiology at presentation who underwent a workup at a single tertiary-care pediatric hospital over a 20-year period were reviewed retrospectively. RESULTS:A total of 48 patients with Horner syndrome were included. Median age at diagnosis was 12 months (range, 1 month to 17 years). A serious etiology was discovered in 7 (15%): neuroblastoma in 5, nasopharyngeal carcinoma in 1, and desmoid tumor in 1. Other causes were congenital/idiopathic (27 [56%]), acquired/idiopathic (10 [21%]), and likely birth trauma (4 [8%]). In 3 patients with a serious etiology, there were significant clinical manifestations of the pathology in addition to Horner syndrome. In the other 4 cases with a serious etiology (all neuroblastoma), the patients presented with Horner syndrome in isolation, and the tumor was discovered during a routine workup. All 5 neuroblastoma cases presented before 5 years of age; urine catecholamines were elevated in 4 of the 5. Imaging revealed mass lesions in the neck or upper chest in all 7 cases with a serious etiology. CONCLUSIONS:In children presenting with Horner syndrome of unknown cause, there is a small but nontrivial risk of a serious underlying etiology. When a young child presents with Horner syndrome in isolation, urine catecholamine testing and imaging of the oculosympathetic pathway are recommended to rule out neuroblastoma.