Excerpt from Choanal Atresia

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Complete nasal obstruction in a newborn may cause death from asphyxia. During attempted inspiration, the tongue is pulled to the palate, and obstruction of the oral airway results. Vigorous respiratory efforts produce marked chest retraction. Increased cyanosis and death may occur if appropriate treatments are not available; however, if the infant cries and takes a breath through the mouth, the airway obstruction is momentarily relieved. Then the crying stops, the mouth closes, and the cycle of obstruction is repeated.

History of the Procedure

In 1755, Roederer first described congenital choanal atresia; therefore, this condition has been recognized for more than 200 years. In 1854, Emmert reported the first successful surgical procedure for congenital choanal atresia in a 7-year-old boy using a curved trocar transnasally. Over the years, the necessity of serial dilatations to maintain patency of the choanae has been clearly recognized.

Frequency

The average rate of choanal atresia is 0.82 cases per 10,000 individuals. Unilateral atresia occurs more frequently on the right side. The ratio of unilateral to bilateral cases is 2:1. A slightly increased risk exists in twins. Maternal age or parity does not increase the frequency of occurrence. Chromosomal anomalies are found in 6% of infants with choanal atresia. Five percent of patients have monogenic syndromes or conditions.

Race: Choanal atresia occurs with equal frequency in people of all races.

Sex: More studies report significantly more females than males affected.

Etiology

The nasal cavities extend posteriorly during development under the influence of the posteriorly directed fusion of the palatal processes. Thinning of the membrane occurs, which separates the nasal cavities from the oral cavity. By the 38th day of development, the 2-layer membrane consisting of nasal and oral epithelia ruptures and forms the choanae (posterior nares). Failure of this rupture results in choanal atresia. Although these choanae are not in the same location as the definitive choanae, which are eventually located more posteriorly, the unexpectedly anterior extent of choanal atresia is explained.

Pathophysiology

A number of theories have been proposed to explain the occurrence of choanal atresia, and they can be summarized as follows:

• Persistence of the buccopharyngeal membrane
• Failure of the bucconasal membrane of Hochstetter to rupture
• Medial outgrowth of vertical and horizontal processes of the palatine bone
• Abnormal mesodermal adhesions forming in the choanal area
• Misdirection of mesodermal flow due to local factors

Clinical

The clinical evaluation includes a complete physical examination to assess for other congenital anomalies. A small feeding tube could be used to determine the patency of the choana, but a complete nasal and nasopharyngeal examination should be performed using a flexible fiberoptic endoscope to assess the deformity. A simple method using the automatic tympanometer to screen newborns for congenital choanal atresia was recently published. The sensitivity and specificity of the technique in diagnosing a patent nostril was reported as 100 per cent. However, a high level of suspicion is required to diagnose bilateral choanal atresia.

Symptoms of severe airway obstruction and cyclical cyanosis are the classic signs of neonatal bilateral atresia. When crying alleviates respiratory distress in an obligate nasal breather, the neonatologist should be alerted to the probability of bilateral choanal atresia. Unilateral atresia may not be detected for years, and patients may present with unilateral rhinorrhea or congestion.

Many patients have an associated narrowed nasopharynx, widened vomer, medialized lateral nasal wall, and/or arched hard palate. Associated malformations occur in 47% of infants without chromosome anomalies. Nonrandom association of malformations can be demonstrated using the CHARGE association, which appears to be overused in clinical practice. The components of the CHARGE association are as follows:

• Coloboma of the iris, choroid, and/or microphthalmia
• Heart defect such as atrial septal defect (ASD) and/or conotruncal lesion
• Atresia of choanae
• Retarded growth and development
• Genitourinary abnormalities such as cryptorchidism, microphallus, and/or hydronephrosis
• Ear defects with associated deafness (The external, middle, and/or inner ear may be involved. Only a small proportion of infants with choanal atresia and related components probably represent this entity.)

The percentages of the different anomalies in CHARGE association are as follows:

• Coloboma - 80%
• Heart defect - 58%
• Atresia of choanae - 100%
• Mental retardation - 94%
• Growth deficiency - 87%
• Genital hypoplasia in males - 75%
• Ear anomalies - 88%

Differential diagnosis

Deviated nasal septum

Dislocated nasal septum

Septal hematoma

Mucosal swelling

Turbinate hypertrophy

Encephalocele

Nasal dermoid

Hamartoma

Chordoma

Teratoma

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