ACR Appropriateness Criteria® Horner Syndrome.

Horner syndrome is a combination of signs and symptoms caused by abnormalities in the oculosympathetic pathway. Typically, patients present with ipsilateral miosis, ptosis, and anhidrosis. Imaging the oculosympathetic pathway is complex because of its extensive course, need for targeted protocols, and the wide range of pathology that can cause it. For this document, we focus our attention on workup guidelines based on clinical features: 1) acuity (acute, nonacute including chronic, insidious, and unknown onset), 2) painless or painful (neck pain, occipital region pain, or headaches), 3) whether there is a history of trauma (any form of injury to the chest, neck, or head area, including iatrogenic injury from recent procedure and surgery), and 4) absence or presence of localizing brain, cranial nerve, or spinal cord neurological signs or symptoms. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.