Choanal atresia

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Jaspinder Kaur, MBBS[2]

Synonyms and keywords: Atresia, Choanal; Atresias, Choanal; Choanal Atresias; Bosma arhinia microphthalmia syndrome; Bosma Henkin Christiansen syndrome; Congenital absence of nose and anterior nasopharynx (OMIM: 603457)

Overview

The word “Choana” is derivative of a greek word “Xovan” which states the funnel and hence, the term “Posterior Choana” is known as posterior nasal aperture or posterior funnel. Choanal atresia (CA) is the most common form of congenital nasal airway abnormality which presents with variable clinical features ranging from acute airway obstruction to chronic recurrent sinusitis depending upon the degree of obstruction. It is caused by the abnormal rupturing of the buccopharyngeal or naso-buccal membrane which results in the failed recanalization of the nasal fossae during the embryological period and hence, occlude the posterior nasal cavity to communicate with the nasopharynx. CA presents with severe respiratory distress, difficulty feeding, and failure to thrive when the obstruction is bilateral; and chronic persistent nasal discharge in unilateral cases. Establishing an airway is an acute otolaryngological emergency because newborns are obligate nasal breathers and experiences the paradoxical cyanosis episodes while feeding. The diagnosis requires a high index of suspicion and usually initial clinical evaluation done by introduction of a six or eight Fr suction catheter via the nostrils, methylene blue dye test, cotton wisp test, and laryngeal mirror test. The obstruction may be further visualized with a narrow flexible nasopharyngoscope after the nasal cavity has been suctioned of mucus and the nasal mucosa has been constricted with a nasal decongestant (e.g., oxymetazoline). However, the final confirmation of the diagnosis is done by CT scan of the nasal cavity which will demonstrate the atresia, define the type of tissue (bony or membranous), and show the configuration of the entire nasal cavity. The treatment of choanal atresia is essentially surgical which can be divided into emergent and elective definitive categories. It may be successfully treated by removing the obstructing tissue by using the nasal endoscopic approach via transnasal route. However, when the thick bony plate extremely narrows posterior nasal cavity, a transpalatal repair technique is more direct. An intraoperative topical application of mitomycin to inhibit fibroblast proliferation has shown to be an effective adjunct to the surgical repair of choanal atresia. Stents fashioned from endotracheal tubes are placed and secured alongwith sutures to the septum in order to prevent postoperative re-stenosis chances which are removed after 6 weeks of duration. The stents must be moistened with saline and suctioned several times daily to prevent mucus plugging and acute respiratory distress.

Historical Perspective

• 1755: Johann Roderer noticed total obstruction of the posterior nasal choana while examining a newborn and hence was the first to describe the CA.
• 1829: Oto et al. further characterized the CA anomalies in relation to the deformity of the palatine bones during an autopsy.
• 1854: Carl Emmert was the first to use the curved trochar through the choanal obstruction in transnasal surgical repair of bilateral CA in a 7- year-old boy and thus, successfully corrected CA surgically.
• 1880: Ronaldson described an importance of CA in his autopsy findings of the newborns who had died from asphyxia and acute respiratory distress.
• 1979: Hall first reports the “CHARGE” syndrome association in 17 children with multiple congenital anomalies who were ascertained by CA. In the same year, Hittner et al found the same syndrome in 10 children with ocular colobomas and multiple congenital anomalies, hence coined the syndrome as “Hall-Hittner syndrome”.
• 1981: Pagon et al. first elaborated the acronym "CHARGE" association (Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, Ear anomalies/deafness).
• 1985: Dehaen conducted the first transnasal endoscopic repair of CA.
• 2008: Barbero et al found the association of CA with the maternal use of an antithyroid drug methimazole.

Embryology

Origin: Development of the nasal cavity starts with neural crest cells migration from their origin in the dorsal neural folds and hence, the development of choanae takes place between the 4th and 11th weeks of gestation.

Gestational week	Developmental process
3rd and 4th week	Neural crest cells commence their caudal migration to reach the midface by the 4th week of gestation. The nasal processes or placodes on the lateral surface of head invaginate to form the nasal pits.
5th week	The nasal pits begin to fold inwards into the mesenchyme forming nasal sacs. These primitive nasal sacs are separated from oral cavity by oronasal membrane.
8th week	The oronasal membrane ruptures creating nasal cavity and a primitive choana located at the junction of nasal cavities and nasopharynx. During this phase of development, there is gradual proliferation of neural crest cells which contribute to the formation of skull base and nasal vaults. The lateral palatal shelves fuse in an anterior-to-posterior direction which forms the hard and soft palate.
10th week	The nasal septum and developing palate fuse. The primitive choanae gets pushed posteriorly and forms “Secondary choanae”. In normal fetus, these secondary choanae are patent for a functioning airway between the anterior nasal cavity and nasopharynx.

Diagnosis

History and Symptoms | Physical Examination | Laboratory Findings | Chest X Ray | CT | MRI | Other Imaging Findings | Other Diagnostic Studies

Presentation

It can be unilateral or bilateral.

Sometimes, a unilateral choanal atresia is not detected until much later in life because the baby manages to get along with only one nostril available for breathing.

Bilateral choanal atresia is a very serious life-threatening condition because the baby will then be unable to breathe directly after birth as babies are obligate nasal breathers (they must use their noses to breathe). These babies usually require airway resuscitation right after birth.

Treatment

The only possible treatment is surgery to correct the defect.

See also

• CHARGE syndrome
• choana

References

Template:Congenital malformations and deformations of respiratory system

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