A 6-month-old male neutered Boxer presented to the Cornell University Hospital for Animals Neurology Service for a 1-week history of progressive pain and right thoracic lameness and a 24-hour history of right-sided Horner syndrome. On presentation he was quiet but alert and responsive. Vital parameters were within normal limits and point of care blood work revealed no significant abnormalities. General, neurologic, and orthopedic exams were performed but somewhat limited due to patient discomfort. Examination revealed enophthalmos, ptosis, and miosis of the right eye; stiff/careful gait in all four limbs with a right thoracic limb weight-bearing lameness and discomfort with right thoracic palpation; mild pain on mid cervical spinal palpation and severe pain evaluation of cervical range of motion. He was neurolocalized to spinal cord segments C6-T2 +/- brachial plexus, right-lateralizing. Lateral cervical radiographs revealed no vertebral lesions. Cervical magnetic resonance imaging revealed no abnormalities in the spinal cord, but revealed an esophageal perforation with marked inflammation of surrounding soft tissues in the right thorax. Full body computed tomography scan was performed and revealed a stick foreign body extending from the cervical esophagus into the stomach and a perforation of the esophagus at the level of the second rib. The patient was taken to surgery where a median sternotomy and gastrotomy were performed to remove the foreign body and repair the damage. This seminar will explore the differentials and work-up for Horner syndrome in the dog as well as the management and outcome of the above case.