RESUMO
PURPOSE: To evaluate the diagnostic yield of advanced imaging in dogs with Horner's syndrome (HS) both with and without additional clinical signs. METHODS: Retrospective review of clinical records from a UK referral hospital (2000-2018). Cases were excluded if HS was trauma- or surgery-related and if no advanced imaging with MRI or CT was performed. Imaging findings were assessed as well as any additional investigations performed. RESULTS: One hundred twenty cases met the inclusion criteria; 88 with additional clinical signs and 32 with isolated HS. MRI or CT of head and neck was performed in 115 cases and/or thoracic CT in eight cases. Causative lesions were identified in 98% (86/88) of cases with additional clinical signs and 3% (1/32) of cases with isolated HS. This was statistically significant (p < .001). Pharmacological localization using phenylephrine (0.1%-10%) was accurate in predicting the site of a causative lesion in 79% (19/24) of tested cases. Overall, 28% (33/120) of cases were idiopathic, of which 49% (16/33) were golden retrievers. When compared to the overall hospital population, and UK Kennel Club records, this confirmed a significant predisposition in this breed (p < .001). No associations between idiopathic HS and concurrent systemic disease were identified. CONCLUSION: This is the first study to evaluate the diagnostic yield of advanced imaging in dogs with HS. Isolated HS is significantly more likely to be idiopathic than cases presenting with additional clinical signs; this could guide decision-making regarding further investigations performed in a clinical setting. Idiopathic HS is over-represented in the golden retriever.