1991-03-11-21 Larynx, atresia © Furness http://www.thefetus.net/
Margaret E. Furness FRACR, DDU*, Brian W. Donnelley FRACR, Jill Lipsett BM BS, PhD
Prevalence: About 60 reported cases of congenital laryngeal atresia, many with other abnormalities. M1:F1.
Definition: A spectrum of abnormalities, ranging from complete occlusion of the larynx, to web-like occlusion at the glottis. Three types have been described: supra- and infraglottic (type I), infraglottic (type II), and glottic (type III).
Etiology: Some cases suggest an autosomal dominant transmission11.
Pathogenesis: Probably arrest of normal development.
Associated anomalies: Present in at least 50% of cases, they include tracheo- or bronchoesophageal fistula, tracheal agenesis, VACTERL, hydrocephalus with absent cervical vertebrae, hypoplastic kidneys, urethral agenesis and skeletal deformities (absent radius, syndactyly).
Differential diagnosis: Extrinsic airway obstruction, bilateral type III cystic adenomatoid malformation of lung.
Prognosis: Depends on tracheostomy, and associated abnormalities.
Recurrence risk: Nil for isolated atresia, otherwise Mendelian inheritance.
Management: As for disorders with fatal outcome.
MESH Larynx-abnormalities, -pathology; Laryngostenosis-congenital BDE 0571 MIM 150300 ICD9 748.3 CDC 748.305
* Address correspondence to Margaret E. Furness, FRACR, DDU, The Queen Victoria Hospital, 160 Fullarton Road, Rose Park, South Australia 5067, Phone 61-8-333 9105 Fax 61-8-333 9184
The mother was aged 29, and had three normal children; this was her first pregnancy by a new partner. Vaginal bleeding occurred at 6 and 8 weeks" gestation. Ultrasound scan at 16 weeks showed an appropriately-grown live fetus, with ascites and edema, large echogenic lungs inverting the diaphragms, dilated trachea and major bronchi, and a relatively small heart (figs 1, 2.)
Fig. 1: Paired coronal scans of fetal trunk, caudad to right. Left: through aorta. Right: through trachea and bronchi (arrowheads). Compare echogenicity of lungs with kidney (arrow).
Fig. 2: Transverse section of fetal thorax at level of four-chamber view of heart. P, posterior.
The amniotic fluid volume, the karyotype and the amniotic fluid alpha-feto-protein were normal.
The appearances were considered to reflect upper airway obstruction, most likely due to laryngeal atresia, as there was no evidence of a tumor or a vascular ring to cause compression. Following counseling, the parents opted for termination of pregnancy.
The autopsy showed a male fetus, weighing 164g, with gross edema of neck and trunk. The lungs were pale and voluminous (fig. 3) with a combined weight of 14g (normal 5.3 - 5.6).
Fig. 3: Anterior view of opened thorax and abdomen, showing large pale lungs almost obscuring the heart and displacing the diaphragm downwards.
The heart was small, weighing 0.74g (normal 1.4), but anatomically normal. There was type ll laryngeal atresia1 with the infraglottic region almost occluded by a dome-shaped cricoid, (fig. 4) leaving a pharyngo-tracheal duct of approximately 15 microns maximal diameter.
Fig. 4: Left: Three-dimensional reconstruction image of the larynx and trachea at necropsy, viewed from 30 degree anterolaterally. (PC - 3D - 3D Reconstruction Software, Jandel Scientific, California). Right: Sagittal section through larynx. H & E x 10. Arrow, cartilage bar (cricoid) occluding airway.
The other laryngeal cartilages were normal. Histologic examination of the lungs revealed marked interstitial edema and striking distension of the developing airspaces. There was 5ml of serous ascites. The esophagus and other organs were normal.
Fluid aspirated from the trachea contained no detectable epidermal growth factor (epidermal growth factor is known to influence lung development) or IGF-1 (insulin-like growth factor) on radioimmunoassay. It is not known whether, or when, these substances are secreted into lung fluid, since it is rarely available for assessment.
The fetus of their subsequent pregnancy appears normal.
Laryngeal atresia is rare, with only 60 reported cases. A case similar to ours, but with tetralogy of Fallot and polyhydramnios, has been diagnosed by ultrasound at 28 weeks" gestation3, and atresia of one mainstem bronchus has been diagnosed at 24 weeks4.
Associated anomalies include tracheoesophageal or bronchoesophageal fistula, tracheal agenesis, the VACTERL association, and hydrocephalus with absence of cervical vertebrae1, hypoplastic kidneys, urethral agenesis and skeletal deformities (absent radius, syndactyly).
A familial tendency has been reported for partial laryngeal atresia (laryngeal web)2, and an autosomal dominant transmission has been suggested11, but complete atresia is usually sporadic.
It has been suggested, by analogy with rat embryology, that the different types of laryngeal atresia (supraglottic plus infraglottic, infraglottic, and glottic) reflect arrest of normal development at different embryologic stages.1
Production of lung fluid begins early, with a net outward flow through the larynx. Complete obstruction therefore causes retention of lung fluid under pressure, and the lungs become expanded, edematous, and echogenic. In addition, air space development is accelerated5, and the lungs may become hyperplastic6. Appearances may differ (table 1) if there is also a tracheoesophageal fistula or a persistent pharyngo-tracheal duct of sufficient size 5,6, or tracheal agenesis3, but it is not known whether ultrasound can differentiate reliably between these situations or distinguish them from bilateral type III cystic adenomatoid malformation7.
Table 1: Differential diagnosis of laryngeal atresia.
Isolated laryngeal atresia
Atresia with fistula
Associated hydrops may reflect compression of the lymphatics, the heart or the intrathoracic vessels. Associated polyhydramnios is common. However, hydrops does not predict fetal death in utero. Ascites has been observed to regress in a fetus with laryngeal atresia and tracheoesophageal fistula7, and an association with “prune belly” has been reported8, which we suggest may have been due to transient ascites.
Survival with isolated laryngeal atresia has been described.10 However, although speech may be achievable, complete laryngeal reconstruction for major atresias is not feasible at present, and the parents should be counselled about the need for lifelong tracheostomy. If they request active treatment, appropriate staff and equipment should be available in the delivery room to allow urgent neonatal tracheostomy, with clamping of the umbilical cord delayed until the airway is secured.
We are grateful to Dr. Leanna Read of the Child Health Research Institute of South Australia for performing assays on the tracheal fluid.
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