Horner's Syndrome after Scalene Block and Carotid Dissection.

BACKGROUND: Horner's syndrome refers to the clinical triad of ptosis, miosis, and anhidrosis resulting from disruption of the ocular and facial sympathetic pathways. A myriad of etiologies can lead to Horner's syndrome; awareness of the underlying anatomy can assist physicians in identifying potential causes and initiating appropriate care. CASE REPORT: Two patients presented to our Nashville-area hospital in 2014. Patient 1 was a 26-year-old man who noticed facial asymmetry one day after an outpatient orthopedic procedure. His symptoms were attributed to his posterior interscalene anesthesia device; with deactivation of this device, the symptoms rapidly resolved. Patient 2 was a 42-year-old man who presented to our emergency department with persistent headache and ptosis over several weeks. Computed tomography angiography revealed ipsilateral carotid dissection and the patient was admitted for further management. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The pathologies underlying Horner's syndrome are exceedingly diverse. Although classic teaching often focuses on neoplastic causes, and more specifically Pancoast tumors, neoplasms are discovered only in a small minority of Horner's syndrome cases. Other etiologies include trauma, cervical artery dissection, and infarction. With a better understanding of the pertinent anatomy and array of possible etiologies, emergency physicians may have more success in identifying and treating the causes of Horner's syndrome.