Radiology Quiz Case 1—Diagnosis

The normal anatomy of the central mediastinal great artery system derives from several complex steps of embryonic differentiation, subsequent involutions, and remaining patencies of primary vascular arches.¹ Abnormal embryological differentiation of the aortic arch and central pulmonary arterial system may lead to complex pathologic relationships between these vessels and the tracheobronchial tree. Because of the considerable topographic variability of their origin and course in the mediastinum, some of these vascular malpositions can cause significant compression of the trachea, mainstem bronchi, or esophagus.² These malformations are rare, accounting for 1.0% to 1.6% of all congenital cardiac anomalies.² The disarranged patterns of the great arteries all share a common form of a complete ring or a sling with subsequent tracheal compression.² Approximately 20% of children with symptomatic vascular rings have other associated congenital heart anomalies.³ The anomalies that most often cause airway compression are a double aortic arch or a right aortic arch with an aberrant left subclavian artery and a left ligamentum arteriosum.⁴

The amount of compression dictates the severity and onset of symptoms,² including stridor, acute or chronic respiratory infections, septic retention pneumonias, atelectasis, acute respiratory distress syndrome, and dysphagia.^{5 - 6} Timely diagnosis and treatment are of paramount importance, and delay may result in long-term intubation and ventilator dependence or even tracheotomy, all of which have been shown to increase preoperative morbidity.² Of special concern and prognostic implication is the impending malacia of the compressed airway segments.⁷ Although the onset of secondary malacia often cannot be predicted, it can develop within weeks or even months and render repair difficult.⁷ Even after successful decompression, however, these malacia segments may require repeated reconstructive procedures.⁷

Traditionally, angiocardiography combined with tracheobronchoscopy has been the "gold standard" for diagnosis.² However, with the development of high-resolution computed tomography (CT) and magnetic resonance imaging (MRI) techniques, which are noninvasive, the use of angiocardiography, which is more invasive, has become less prevalent.⁶ Also, CT and MRI are especially valuable for detecting pulmonary artery slings.³ Despite the diagnostic power of CT and MRI, distinct limitations are associated with their use. For example, atretic segments can be ill defined,³ and because young children often need sedation to undergo these studies, there will be an increase in morbidity and cost.³ Therefore, cross-sectional imaging is recommended only when other diagnostic modalities fail to delineate the abnormality.²

Other authors have championed barium esophagography as a less invasive and less expensive alternative to CT and MRI for providing essential preoperative information.^{3 ,8} Echocardiography is the least invasive procedure.³ It should be performed in all patients with suspected aortic arch anomalies, because the therapeutic approach may change radically in the presence of associated intracardiac anomalies.^{3 ,9} In the present case, echocardiography (Figure 2) clearly demonstrated a double aortic arch (solid arrows) surrounding the trachea (dashed arrow). Ultimately, successful surgical repair mandates definitive intraoperative delineation of the anatomy to minimize the risk of inaccurate diagnosis and incomplete or inappropriate treatment.³ Such a procedure often entails intraoperative tracheobronchoscopy.²

Because prompt diagnosis and treatment of a double aortic arch with tracheal compression is crucial in preventing increased preoperative morbidity, otolaryngologists should be aware of this malformation and include it in the differential diagnosis in cases involving airway distress.

Residents and fellows in otolaryngology are invited to submit quiz cases for this section and to write letters to the ARCHIVES commenting on cases presented. Quiz cases should follow the patterns established. See "Instructions for Authors."

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