Trachea: Developmental Abnormalities
KEY POINTS
- Imaging may make a precise diagnosis in these anomalies but is only adjunctive to the endoscopic examination, with the latter being definitive in the vast majority of cases.
- Imaging might significantly affect medical decision making in some of these developmental conditions.
- Computed tomography and/or magnetic resonance imaging are typically the main and frequently the only studies required aside from a chest x-ray.
Most congenital abnormalities of the trachea will not come to imaging. They will present as airway problems or occasionally neck masses and will be evaluated clinically with direct endoscopy as directed by the clinical setting. These anomalies include those that are mainly structural (but could also be acquired), such as tracheal esophageal clefts and fistulas that may be suspected in the context of other anomalies or syndromes (Figs. 210.1–210.3). Tracheal-related anomalies also include a variety of developmental cysts and vascular malformations that, for the most part, secondarily affect the trachea and only very rarely arise from it (Fig. 210.4). Imaging follows the initial clinical evaluation in selected cases. Imaging usually includes the larynx since subglottic stenosis and laryngeal anomalies will need to be excluded, as they might be associated with tracheal problems and/or produce the same symptoms and clinical problems. For this reason, this chapter should be considered along with Chapter 202 on laryngeal anomalies.
Congenital or early childhood tracheal stenosis or tracheomalacia may arise independent of any identifiable cause; however, it may come to imaging to exclude a mass compressing the trachea or to exclude a tracheal mass (Fig. 210.5). Anomalous vessels associated with congenital heart and great vessel anomalies can cause tracheomalacia (Fig. 210.3A); those conditions are beyond the scope of this text.
In general, developmental abnormalities of the trachea present during childhood. Some manifest in infancy; however, the presentation may be delayed until sometime beyond infancy well into the early adult years and even into middle age (Fig. 210.6). If the lesion has growth potential, it tends to be at the same rate of normal structures, including a possible rapid growth phase at times of accelerated growth of the individual, such as in adolescence. Some, such as high-flow vascular malformations, have internal physiologic dynamics that will allow them to enlarge more rapidly than normal tissues rather than truly proliferate. Truly neoplastic conditions, such as a proliferative hemangioma (Chapters 8 and 9), will manifest growth out of proportion to normal structures; these vascular malformations rarely affect the trachea.
Developmental abnormalities may be discovered incidentally on imaging studies done for other purposes (Figs. 210.3B, 210.4C, and 210.7), but they more typically present as a neck mass or because they interfere with airway function, producing noisy breathing or, in an infant, sleep apnea. These are all rare occurrences except for tracheoceles, which are seen incidentally in a fraction of a percent of the population that come to imaging for other reasons (Fig. 210.7). They are typically not painful unless there is some present complicating factor. Developmental abnormalities may also manifest because of such complicating factors. Examples include infection in a cyst or diverticulum that connects to the trachea and bleeding, thrombosis, or infection of a vascular malformation.