The diagnostic yield of advanced imaging in dogs with Horner's syndrome presenting with and without additional clinical signs: A retrospective study of 120 cases (2000–2018)

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