Volume 1, Issue 1 , Pages 45-49, March 2006
Congenital segmental absence of tracheal rings
Article Outline
Summary
Tracheomalacia is a well-described phenomenon in children with oesophageal anomalies, especially tracheo-oesophageal fistula, but congenital absence of cartilaginous tracheal rings is very rare. In the two patients with oesophageal atresia described in this report, bronchoscopy and radiological findings showed an abnormal segment of trachea. In this segment, the cartilaginous rings were absent, with bronchoscopic appearances resembling normal oesophagus. One patient was treated with a tracheostomy and the other by insertion of a balloon-expandable metal stent. They are both alive, aged three years and five years, respectively.
Keywords: Tracheal rings, Congenital anomaly, Tracheomalacia, Cartilage, Dyschondroplasia
1. Introduction
Congenital malformations of the trachea and bronchi may occur as a primary phenomenon, or may be secondary to abnormalities of the cardiovascular or gastrointestinal systems. Secondary tracheomalacia may occur with a tracheo-oesophageal fistula, oesophageal atresia, external compression, abnormalities of the chest wall or dyschondroplasia. Complete failure of development of the cartilaginous rings of the trachea has not previously been reported in the literature.
We describe two patients who appear to have complete absence of cartilaginous rings in a segment of the trachea, associated with oesophageal anomalies and an aberrant tracheal branching pattern. Both children presented at birth with a presumed diagnosis of severe tracheomalacia. Both direct examination of the trachea at microlaryngoscopy and bronchoscopy (MLB) and radiological imaging showed apparent absence of cartilaginous rings in the affected tracheal segment. This may represent a failure of cartilage formation during embryogenesis, in association with oesophageal atresia or tracheo-oesophageal fistula.
1.1. Case 1
A male infant born at 35 weeks gestation was diagnosed with oesophageal atresia with a long gap (approximately three vertebral bodies) shortly after birth. MLB performed at seven days of age appeared to show severe tracheomalacia. This was confirmed by a bronchogram performed a week later, which showed severe expiratory collapse of the middle third of the trachea, with marked kinking of the airway at the tip of the endotracheal tube, and also a tracheal trifurcation (Fig. 1). Tracheostomy was performed at four weeks, to facilitate weaning from ventilation. The oesophageal atresia was repaired at six weeks of age with a gastric pull-up procedure. The pull-up was revised when the child was 14 months old, at which time the lower cervical portion of the oesophagus was noted to have a very poor muscle coat. Following the revision procedure, the child was unable to vocalise, despite having consistent vocalisation preoperatively. Flexible bronchoscopy via the tracheostomy tube showed severe distal tracheomalacia, with complete collapse of the trachea on expiration. It was postulated that the high intra-tracheal air pressure required to prevent tracheal collapse during expiration was preventing vocalisation. MLB and flexible oesophagogastroscopy was performed at 27 months of age, to assess the tracheomalacia and the gastro-oesophageal anastomosis. There was grade III, mainly anterior, acquired subglottic stenosis, and a suprastomal granuloma. The middle third of the trachea (for 2.5
cm from the stoma) was found to collapse completely on expiration, and had no visible cartilaginous rings, being very similar to oesophagus in appearance (Fig. 2). The lower third of the trachea was grossly normal, but trifurcated into a common bronchus to the right upper and middle lobes, the right lower lobe bronchus, and a long, thin and floppy left main bronchus (Fig. 3, Fig. 4). There was no evidence of an oesophago-gastric anastomotic stricture. At last review, the child was three years old, with height on the 25th centile and weight on the 9th centile. He was tolerating formula milk and mashed food orally, and managing weak vocalisation. There are currently no plans for reconstruction of the subglottis, and the patient is being managed conservatively.
Fig. 1.
Case 1: Bronchogram demonstrating kinked trachea.
Fig. 2.
Case 1: MLB image demonstrating collapsed proximal trachea.
Fig. 3.
Case 1: MLB image proximal to carina.
Fig. 4.
Case 1: MLB image demonstrating trifurcation of trachea.
1.2. Case 2
A male infant was born at 36 weeks’ gestation to parents with a possible paternal family history of Turner's syndrome. The labour was uneventful, but the child was noted to be in poor condition at birth, although no Apgar scores were recorded. The baby was intubated with a 3.5-mm endotracheal tube two minutes after birth, at which time it was not possible to pass a nasogastric tube into the stomach. A chest radiograph taken shortly after birth showed over-expanded lungs. A diagnosis of tracheo-oesophageal fistula and oesophageal atresia was made, and a primary repair of the oesophagus was performed within 24h of birth. At surgery, a small fistula was noted arising from the lower trachea, and the oesophagus was found to be very thin-walled, especially in the proximal third. The anaesthetist noted that it was not possible to advance the endotracheal tube more than 1.5cm below the glottis. Postoperatively, the patient was electively paralysed and intubated for five days. Ventilation was complicated by rising carbon dioxide levels, and increasing over-expansion of the lungs on chest radiography. Flexible bronchoscopy showed almost complete obliteration of the tracheal lumen with a small central orifice. A 2.2-mm flexible bronchoscope was passed through this area of collapse to the distal trachea, and a 2.5-mm endotracheal tube was rail-roaded over the bronchoscope, with an immediate improvement in the arterial blood gas picture. Echocardiography demonstrated a small ventricular septal defect. A vascular ring was excluded by computed tomography. Ultrasound demonstrated a solitary kidney, and karyotyping showed no chromosomal abnormality. Rigid bronchoscopy and flexible oesophagoscopy on day 11 showed complete absence of tracheal cartilage rings, and a satisfactory oesophageal repair. Although a patent airway was maintained with a 3.0-mm endotracheal tube sited just above the collapsed segment of trachea, a trial of extubation failed after 30min, due to respiratory obstruction, and continuous positive airway pressure (CPAP) was also unsuccessful. At 24 days of age, a balloon-expandable metal stent (Palmaz P188, diameter 8–12mm, length 18mm) was inserted, and expanded to 8mm (Fig. 5, Fig. 6, Fig. 7). The child was successfully extubated later the same day, and discharged home. The patient suffered from aspiration pneumonitis, requiring three hospital admissions over the next six months. Bronchoscopy at the age of 10 months showed granulation tissue related to the stent. Oesophagoscopy showed an anastomotic stricture, which was dilated. There were no features of oesophagitis. Clinical progress was good until the age of 21 months, when the patient was noted to have increasingly noisy breathing, and a significant history of snoring. The stented segment of the trachea was dilated from a diameter of 3–4mm to 8mm, with an immediate improvement in symptoms.
Fig. 5.
Case 2: Lateral inspiratory bronchogram prior to stent insertion, demonstrating anteroposterior tracheal collapse.
Fig. 6.
Case 2: Lateral expiratory bronchogram prior to stent insertion.
Fig. 7.
Case 2: Lateral bronchogram following insertion of tracheal metal stent.
At the age of 22 months, bronchography and bronchoscopy showed moderate airway collapse proximal and distal to the stent. The lumen within the stent was narrowed by cobblestone granulations, which were crushed with a 10-mm balloon. An abnormal tracheobronchial branching pattern was noted, with a tracheal (porcine) bronchus to the right upper lobe. There was no evidence of bronchomalacia. The patient was most recently seen at the age of five years. He was doing well although his exercise tolerance was reduced compared to that of his peers.
2. Discussion
The embryological development of the trachea is first evident at three weeks [1]. The laryngotracheal groove forms in the foregut, and lengthens both caudad and cephalad to form the tracheal primordium. The pulmonary primordium bulges ventrally from the foregut. The tip of the tracheal primordium buds left and right to form the bronchial primordia. By the sixth week, the trachea and oesophagus have completely separated. The cells from which muscle, cartilage and connective tissue will develop are derived from mesenchymal proliferation of coelomic cavity cells. Cartilage appears in the trachea at about 10 weeks, as the tracheal bifurcation migrates caudad down the neck. The development of the thyroid and cricoid cartilages from the fourth and fifth arches occurs earlier, between the 5th and 7th weeks. The normal ratio of cartilaginous to membranous sectors of the trachea is about 4.5:1 at birth.
Congenital malformations of the trachea and bronchi may either be due to a primary embryological disturbance, or secondary to abnormalities of the central nervous system or gastrointestinal systems [2], [3]. Tracheomalacia may be primary (occurring in otherwise normal infants) or secondary to other abnormalities, including tracheo-oesophageal fistula and oesophageal atresia, dyschondroplasias, and external compression by cardiovascular anomalies, abnormalities of the bony thorax or neoplasms. In tracheomalacia the ratio of cartilaginous to membranous sectors may decrease to 2:1, and the walls of the trachea become less rigid, partially or completely collapsing during expiration and producing airway obstruction [4].
The two patients presented here are the first reported examples of the complete absence of cartilage in a segment of trachea. This anomaly produces clinical effects similar to severe tracheomalacia. Interestingly, in both patients this tracheal defect was accompanied by oesophageal abnormalities, suggesting that the absence of tracheal rings may be associated with abnormal gastrointestinal development. Both patients also had an abnormal tracheobronchial branching pattern, a finding also present in many children with congenital tracheal stenosis.
Although the bronchogram findings in these patients were very abnormal, MLB is better for evaluation of the cartilaginous rings of the trachea. It is possible that endoluminal ultrasound will show this anomaly, but this technique was not available to us when these patients presented.
Both patients continue to make good progress after two quite different forms of treatment. Resection of the abnormal segment or temporary stenting would be other possibilities. It is difficult to know which of these four treatments is best. The probability of successful decannulation following tracheostomy (case 1) is unknown, because it is not clear whether tracheal rigidity will improve with time. The same uncertainty would be present with temporary stenting. The disadvantage of permanent metal stenting, as in case 2, is that the stented segment may become a significant stenosis as the child grows. Resection with end-to-end anastomosis offers the possibility of curing the airway symptoms with a single procedure, but would risk damage to the repaired oesophageal atresia in separating the trachea from the thin-walled and probably adherent oesophagus.
References
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- . Congenital malformation of the trachea and bronchi. In: fourth ed.. Bluestone CD, Stool SE, Alper CM, Arjmand EM, Casselbrant ML, Dohar JE, et al. editor. Pediatric Otolaryngology. vol. 2:2003;p. 1482
- . The trachea in children with tracheo-oesophageal fistula. Histopathology. 1979;3:329–338
PII: S1871-4048(05)00016-X
doi:10.1016/j.pedex.2005.12.003
© 2005 Elsevier Ireland Ltd. All rights reserved.
Volume 1, Issue 1 , Pages 45-49, March 2006
