steeple sign steeple sign in radiology, the steeple sign is a radiologic sign found on a frontal neck radiograph where subglottic tracheal narrowing produces the shape of a church steeple within the trachea itself. the presence of the steeple sign supports a diagnosis of croup, usually caused by paramyxoviruses. it can also be defined as the replacement of the usual squared-shoulder appearance of the subglottic area by cone-shaped narrowing just distal to the vocal cords. this is called the steeple or pencil-point sign. steeple signthe steeple sign as seen on an anteroposterior neck x-ray of a child with croupdifferential diagnosiscroup