Chapter 29: The Nose, Nasal Cavity, and Nasopharynx

DEVELOPMENTAL ABNORMALITIES

Choanal Stenosis and Atresia

Posterior choanal stenosis or atresia is the most common developmental narrowing of the nasal cavity, and is the most common cause of symptomatic neonatal nasal obstruction (Table 29-1). Choanal stenosis and atresia are due to failure of breakdown of the embryologic nasobuccal membrane at the level of the posterior choanae. In approximately 30% of cases, the narrowing or occlusion is purely bony. Most other patients have membranous occlusion in combination with bony narrowing. A pure membranous atresia is rare. Approximately 40% of children with choanal atresia have bilateral involvement. Choanal atresia occurs in approximately 1 in 5000 births.^1,2

In the neonate, bilateral choanal obstruction results in respiratory distress that is mitigated by crying (paradoxical cyanosis). Feeding difficulty is common because the infant cannot nurse and breathe at the same time. Because neonates are obligate nose breathers, immediate therapy is required in the presence of bilateral high-grade nasal airway obstruction. Unilateral choanal obstruction may not become clinically apparent until later in childhood. Potential symptoms of unilateral obstruction include nasal stuffiness, rhinorrhea, sleep apnea, and recurrent infection. In the young infant, passage of a nasal catheter of at least an 8 Fr diameter excludes the presence of clinically significant choanal obstruction.

The diagnostic imaging evaluation of choanal stenosis and atresia is best achieved with thin-section CT. Suctioning of the nasal cavity and the instillation of vasoconstrictive nasal drops prior to image acquisition improve the diagnostic quality of the examination. An air–fluid level is often present within the obstructed nasal cavity. The osseous alterations consist of medial deviation of the medial maxillary wall, lateral deviation and thickening of the vomer, and fusion or bridging of the vomer to the perpendicular plate of the palatine bone (Figures 29-1 and 29-2). By definition, abnormal narrowing is indicated by the demonstration of a posterior choanal width of less than 3.4 mm in a child younger than 2 years. A vomer width of more than 3.4 mm in a child less than 8 years of age is abnormal. Membranous obstruction occurs at the level of the junction of the perpendicular portion of the palatine bone with the pterygoid processes, anterior to the pterygoid plates.^3–5