venerdì 7 dicembre 2007

Choanal atresia


There is bony obstruction of the right choana (Figure 1 and Figure 2) with an air fluid level in the meatus. Note the thickening of the vomer (Figure 1) and the hypoplastic right inferior turbinate (Figure 1).

Diagnosis: Choanal atresia

Choanal atresia is a predominately bony occlusion of the posterior choanae (the posterior nasal cavity transition to the nasophayrnx).
Unilateral choanal atresia presents with unilateral purulent rhinorrhea and a mild breathing obstruction. Patients with bilateral choanal atresia present with severe respiratory distress in the immediate newborn period.
Findings of choanal atresia include unilateral or bilateral narrowing of the posterior nasal cavity at the choanae with a membranous-osseous obstruction.

Choanal atresia results secondary to failure of perforation of the oronasal membrane during the seventh week of gestation. Bony choanal atresia (85-90%) is caused by incomplete canalization of the choanae while membranous choanal atresia (10-15%) results secondary to incomplete resorption of epithelial plugs. Unilateral choanal atresia is twice as common as bilateral choanal atresia. Choanal atresia is twice as common in females.

Patients with bilateral choanal atresia present with severe respiratory distress in the immediate newborn period. This respiratory distress is exacerbated because infants are obligate nasal breathers up until 6 months of age. Feeding aggravates the respiratory distress, while crying, which results in increased oral breathing, relieves it. Unilateral choanal atresia (or choanal stenosis) results in purulent unilateral rhinorrhea with mild respiratory obstruction and may present later in childhood. Failure to pass a nasogastric tube is diagnostic. A number of other associated abnormalities may be associated with choanal atresia, including CHARGE syndrome.

Thin-axial section CT of the maxillofacial bones is recommended to make the diagnosis. Narrowing of the posterior choana less then .34 mm in children less than 2 years old is diagnostic. Associated findings include thickening of the vomer and medial bowing of the posterior maxilla. The nasal cavity may be filled with soft tissue or fluid. If the diagnosis is suspected, suctioning of the child before scanning is recommended. A thick or thin obstructing membrane may also be present.

Membranous choanal atresia may be treated with passage of a nasogastric tube which perforates the obstruction. An oral airway should be established immediately upon suspicion of bilateral choanal atresia. Transnasal endoscopic surgical correction of bilateral choanal atresia should be initiated promptly after the diagnosis. Transpalatal resection of the vomer with choanal reconstruction may be required for bilateral bony atresia.

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