 This compresses the esophagus and trachea because of the persistence of a ductal ligament (from fetal circulation) that may connect between the aorta on the front and the left subclavian artery posteriorly going to the left arm.Infants with vascular rings typically present before 12 months with respiratory or esophageal symptoms like stridor, wheezing, cough, dysphagia, or difficulty feeding.The stridor improves with neck extension, differentiating from laryngomalacia which is relieved by prone or upright positioning, and will not be relieved with corticosteroids or epinephrine, unlike croup.