Vascular ring: a cause of congenital stridor.

Stridor beginning at, or soon after, birth is not an uncommon symptom Such stridor is seldom severe, has a natural tendency to become progressively less marked, and in the majority of infants disappears entirely at the end of the first, or early in the second, year of life. Occasionally, some cause of laryngeal or tracheal obstruction is found and can, where possible and when necessary, be eliminated. Finally, a number of babies with congenital stridor succumb to asphyxia or recurrent pulmonary infections, usually before the age of 1 year. It must be admitted that in the majority of cases where recovery is spontaneous, and of those who die, no satisfactory cause for the stridor is ever found. The possible causes fall into two main groups according to whether the larynx or the trachea is the site of obstruction. Laryngeal stridor in the newborn may be due to an exaggeration of the infantile shape of the upper aperture of the larynx. The aryepiglottic folds are almost in contact, producing a purring, inspiratory stridor. There is no dyspnoea, no distress and no dysphagia, and the condition is recognized on laryngoscopy. Webs, cysts and tumours of the larynx are all excessively uncommon, and can be seen on laryngoscopic examination. Neuromuscular incoordination of the larynx has been suggested as a possible cause of congenital stridor: the condition, if it exists, should be recognizable on laryngoscopy. Tracheal stridor in the newborn may be due to tracheal stenosis, but this condition is extremely rare, and the majority of cases are not sufficiently severe to cause symptoms. Bronchoscopy and contrast radiography will demonstrate the condition. The trachea may be pressed upon by an enlarged thymus, a congenital goitre, or anomalous great vessels in the superior mediastinum. These three conditions will be considered in more detail. Thymic stridor is described by Cockayne (1947) as