Essay answer for ENT PG exam - "Choanal Atresia - etiology, pathophysiology, management. Add note on Types & management" under 800 words - images/diagrams/

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Choanal Atresia — Etiology, Pathophysiology, Types & Management

Definition & Incidence

Choanal atresia is the absence of communication between the posterior nasal cavity and the nasopharynx due to persistence of an atretic plate at the posterior choana. It is one of the most common congenital nasal anomalies, with an incidence of 1 in 5,000–8,000 live births. Females are affected more than males (2:1). Up to two-thirds of cases are unilateral, with right-side predominance.

Etiology

The etiology is multifactorial — both genetic and environmental factors contribute:

Embryological basis: In normal development, the buccopharyngeal membrane ruptures at 6–7 weeks gestation, establishing posterior nasal communication. Several theories have been proposed for failure of this process:

Theory	Mechanism
Persistence of buccopharyngeal membrane	Failure of rupture of the nasobuccal membrane of Hochstetter
Abnormal mesodermal adhesions	Mesodermal ingrowth obliterating the posterior choana
Misdirected neural crest cell migration	Aberrant cell migration leads to abnormal bony/membranous plate
Local infection/trauma	Environmental insults during embryogenesis

Associated syndromes: Up to 50% of all choanal atresia patients — and 75% of bilateral cases — have associated congenital anomalies, most notably:

CHARGE syndrome (Coloboma, Heart defects, Atretic choana, Retardation of growth, Genitourinary disorders, Ear abnormalities) — the most important association
Crouzon syndrome, craniosynostosis, microcephaly
Cleft palate, hypertelorism, polydactyly
Hypoplasia of orbit and midface

Pathophysiology

The anatomic features constituting choanal atresia are:

Narrow nasal cavity
Lateral bony obstruction — medialisation of the pterygoid plates
Medial obstruction — thickening and broadening of the vomer
Membranous obstruction at the posterior choana

Because neonates are obligate nasal breathers, bilateral atresia produces a dramatic cyclic pattern: the infant attempts nasal breathing → obstruction causes respiratory distress and cyanosis → infant cries → oral breathing restores oxygenation → cycle repeats. This is the pathognomonic "cyclic cyanosis relieved by crying."

Types

Choanal atresia is classified by laterality and composition of the atretic plate:

By Laterality:

Type	Frequency	Presentation
Unilateral	~65%	Later in life; rhinorrhea, unilateral nasal obstruction, thick secretions
Bilateral	~35%	Neonatal emergency; cyclic cyanosis, respiratory distress

By Composition (Morgagni's classification):

Type	Frequency	Features
Bony (osseous)	~29%	Complete bony plate; dense on CT
Mixed (bony-membranous)	~71%	Bony + soft tissue component; most common
Membranous	Rare/nil	Pure membranous — practically absent per current studies

Per Cummings Otolaryngology: "No patients were found to have a purely membranous atresia" — the traditional teaching of 90% bony/10% membranous is now revised to ~29% bony and 71% mixed bony-membranous.

Diagnosis

Clinical: Failure to pass a 6-F catheter 32 mm into the nasopharynx. Pooling of secretions in the occluded nasal cavity.

Nasal endoscopy: Direct visualisation with a 120° nasopharyngoscope confirms the atretic plate and differentiates atresia from stenosis (choana < 6 mm = stenosis).

Bilateral choanal atresia viewed through a 120° nasopharyngoscope — the posterior nasal passages are completely occluded

Fig. 1 — Bilateral choanal atresia viewed through a 120° nasopharyngoscope (Cummings Otolaryngology)

CT scan (gold standard): Axial cuts at the level of the posterior choana confirm bony vs. membranous nature, plate thickness, and vomerine broadening. Nasal decongestion/suctioning before imaging improves resolution.

Axial CT — unilateral choanal atresia: bony atretic plate with associated soft tissue on the right

Fig. 2 — Axial CT: unilateral bony choanal atresia with associated soft tissue (Cummings Otolaryngology)

Axial CT — bilateral choanal atresia with soft tissue component

Fig. 3 — Axial CT: bilateral choanal atresia (Cummings Otolaryngology)

Axial CT of a 1-month-old infant: right side showing dense bony plate, left side showing mixed bony-membranous obstruction with vomerine thickening

Fig. 4 — Axial CT: bilateral mixed-type choanal atresia in a 1-month-old — note bony plate (right) and mixed plate (left), medialization of pterygoid plates, vomerine thickening

Axial CT and sagittal reconstruction: right-sided unilateral mixed choanal atresia (arrows)

Fig. 5 — CT axial (A) and sagittal (B): unilateral right mixed choanal atresia, arrows indicate atresia wall

Management

Immediate (Bilateral Atresia — Neonatal Emergency):

Oral airway (McGovern nipple) or orotracheal intubation to establish airway
Supplemental oxygen
NG tube feeding or gastrostomy if oral feeding impaired
Tracheotomy only in cases of multiple-level airway obstruction or respiratory failure

Surgical Repair:

Timing:

Bilateral atresia: Surgery after initial airway stabilisation; ideally wait several months for adequate facial growth (analogous to cleft lip repair timing), unless respiratory compromise demands earlier intervention
Unilateral atresia: May be safely delayed months to years — allows nasal growth and reduces risk of restenosis

Surgical approaches:

Approach	Details	Preferred?
Transnasal endoscopic	0° endoscope; urethral sound to perforate plate at thinnest point; backbiting forceps, microdebrider, drill, or laser to remove tissue and bone	Current gold standard
Transpalatal	Pedicled hard palate mucoperiosteal flap (based on greater palatine artery) elevated to expose choanae	Older approach; used for revision or complex anatomy
Transeptal	Via septal window	Rarely used

Transpalatal approach: pedicled hard palate mucoperiosteal flap elevated on the greater palatine artery to expose the posterior choana

Fig. 6 — Transpalatal repair: mucoperiosteal flap elevated exposing the choanae (Cummings Otolaryngology)

Transnasal endoscopic technique:

Topical decongestion and vasoconstriction
Perforate atretic plate with urethral sound at its thinnest portion
Enlarge with backbiting forceps, microdebrider, drill, or KTP/CO₂ laser
Landmark: posterior tip of middle turbinate — stay inferior to avoid intracranial injury
Create adequate choanal opening with mucosal flap preservation

Adjunctive measures (controversial):

Stenting: Silastic stents post-repair to maintain patency; duration 4–6 weeks (now debated)
Mitomycin C (fibroblast inhibitor): Topical application to reduce scar fibrosis and restenosis
Mucosal flap preservation: Minimising mucosal trauma correlates with lower restenosis rates

Complications:

Restenosis — most common; rates highest in neonates and syndromic cases
Intracranial injury (if dissection superior to middle turbinate)
Revision surgery often required

Note on Types of Choanal Atresia & Type-Specific Management

Type	Key Feature	Management Consideration
Unilateral bony	Dense plate, unilateral	Delay surgery; transnasal endoscopic approach
Bilateral bony	Neonatal emergency	Urgent airway, then staged endoscopic repair
Mixed bony-membranous	Most common (71%); combined obstruction	Transnasal drill + microdebrider; more tissue removal needed
Bilateral vs. unilateral	Syndromic associations higher with bilateral	Screen for CHARGE; multidisciplinary management

Prognosis is better in older children and non-syndromic, unilateral cases — these have the lowest recurrence rates after repair. Bilateral syndromic cases carry higher surgical morbidity and restenosis risk.

Sources: Cummings Otolaryngology: Head & Neck Surgery (7th ed.); Grainger & Allison's Diagnostic Radiology

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