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

# 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 presenting 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 nasobuccal membrane which results in the failed recanalization of the nasal fossae during the embryological period and hence, occluding the posterior nasal cavity from communicating with the nasopharynx. CA presents with severe respiratory distress, feeding difficulties, and failure to thrive when the obstruction is bilateral or total; and chronic persistent nasal discharge in partial or unilateral cases. Establishing a secure 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 which is done by an 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 mucosal secretions and the nasal mucosa is constricted with a nasal decongestant (e.g., oxymetazoline). However, the final confirmatory diagnosis is done by CT scan of the nasal cavity which will demonstrate the atresia, define the tissue type (bony or membranous), and show the configuration of the entire nasal cavity. The treatment is essentially surgical which can be divided into emergent and elective approaches. It may be successfully treated by removing the obstructing tissue and reconstrucitng the posterior choanae  by using the preferable transnasal endoscopic route.  However,in cases where, the thick bony plate extremely narrows the posterior nasal cavity, a transpalatal repair technique is more approachable. An intraoperative topical application of Mitomycin-C to inhibit fibroblast proliferation has shown to be an effective adjunct to its surgical repair. Stents created from endotracheal tubes are placed and secured alongwith sutures to the septum in order to prevent postoperative re-stenosis incidence and are usually removed probably 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 choanae while examining a neonate 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. 
- 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. 

# Classification
CA can be classified on the basis of several variables such as morphology, laterality, association with congenital anomalies and surrounding structures involvement as described in the following tables from Table 1 to 4.

## Table 1: Based on the morphology  

## Table 2: Based on the laterality

## Table 3: Based on association with other congenital anomalies

## Table 4: Based on structure involvement

# Embryology
Origin: Development of the nasal cavity begins with neural crest cells migration from their origin in the dorsal neural folds. The development of posterior choanae takes place between the 4th and 11th weeks of gestation which is elaborated in Table 5 .
Table 5 explains the embryological process for the development of posterior choanae:
- Normal anatomical relations of the atretic plate are as follows: 
- Superior surface: Under surface of body of sphenoid
- Lateral border: Medial pterygoid lamina
- Medial border: Vomer
- Inferior surface: Horizontal plate of palatine bone

# Pathophysiology
- Obligate nose breathers: In neonates, the epiglottis is more superiorly placed in relation to adults so when infant swallows, the larynx rises above epiglottis position and touch the nasopharynx, and locks between soft palate and sides of nasopharynx. Due to this elevated laryngeal position compared to the adults, newborns are obligate nose breathers until mouth breathing is established with the subsequent descent of the larynx at approximately 46 weeks of life.
- During inspiration, the neonate sucks the tongue and creates the vacuum in the oropharynx which moves soft tissue of the floor of mouth up and back towards soft palate.
- During expiration, the airways pressure causes soft palate to push forward against the soft tissue and tongue in the mouth and further obstructs the oral airway. 
- Interrelation of respiration, feeding and crying episodes:
As the infants are obligate nasal breather, the oral airway is used by them only during crying; otherwise it is invariably blocked or used by them during normal respiration.
The 1/3rd reduction in the diameter of the nasal airway increase nasal airway resistance by 81 times resulting in severe distress in neonates. As a result, the infant with bilateral CA experiences episodes of asphyxia and severe distress in quiet respiration when their mouth is normally closed, especially during sleep or feeding times.
Feeding difficulty can be the initial presenting event in which the infants can present with progressive airway obstruction and choke episodes while feeding because of their inability to breathe and feed at the same time.
Moreover, the infant can become cyanotic which is relieved by crying or gasping as the child opens the mouth widely, releases the air obstruction and subsequently, the cyanosis disappears. However, the cycle repeats itself if the crying stops and the mouth closes.
Similarly, as the child falls asleep, the mouth closes and a progressive obstruction starts with stridor followed by increased respiratory effort and cyanosis. Either the observer opens the child's mouth or the child cries and the obstruction is cleared.
In resting state, child has severe retractions, and struggles to breath with rapid cyclic development of cyanosis. Moreover, the infant with bilateral CA rarely develops an ability to breathe through mouth and hence, the medical emergency would exist in the complete absence of patent both nasal cavities.
- As the infants are obligate nasal breather, the oral airway is used by them only during crying; otherwise it is invariably blocked or used by them during normal respiration.
- The 1/3rd reduction in the diameter of the nasal airway increase nasal airway resistance by 81 times resulting in severe distress in neonates. As a result, the infant with bilateral CA experiences episodes of asphyxia and severe distress in quiet respiration when their mouth is normally closed, especially during sleep or feeding times.
- Feeding difficulty can be the initial presenting event in which the infants can present with progressive airway obstruction and choke episodes while feeding because of their inability to breathe and feed at the same time.
- Moreover, the infant can become cyanotic which is relieved by crying or gasping as the child opens the mouth widely, releases the air obstruction and subsequently, the cyanosis disappears. However, the cycle repeats itself if the crying stops and the mouth closes.
- Similarly, as the child falls asleep, the mouth closes and a progressive obstruction starts with stridor followed by increased respiratory effort and cyanosis. Either the observer opens the child's mouth or the child cries and the obstruction is cleared.
- In resting state, child has severe retractions, and struggles to breath with rapid cyclic development of cyanosis. Moreover, the infant with bilateral CA rarely develops an ability to breathe through mouth and hence, the medical emergency would exist in the complete absence of patent both nasal cavities.

## Embryological theories
- Hengerer and Strome proposed four embryological originating factors for the development of congenital CA.  
- Persistence of buccopharyngeal membrane of anterior intestine;
- Failure of Hochstetter bucconasal membrane to rupture usually in the seventh gestational week;
- Abnormal adherence of the mesodermal tissue in the choanal region;
- Abnormal guidance of mesodermal flow secondary to local factors.
- Other theories which are not so widely considered are:
- Resorption of secondary nasal fossa floor
- Incomplete extension of nasal cavity dorsally
- Migration of dorsal part of frontonasal process to fuse with the palatal shelves
- However, none of these proposed pathologies gives a confirmatory support for an obstructive or minimalized size of the choanal openings by developmental processes, and hence, currently there has been no definitive evidence supporting one theory over the others. 

## Anatomical deformities
- Following deformitites are associated with CA:
- The bony atretic plate is situated in front of the posterior bony septum
- Narrowed nasal cavity
- Thickened lateral pterygoid plates compromising the nasal airway
- Thickening of medial aspect of vomer
- The membranous plate situated in between lateral pterygoid and vomer
- High arched palate

# Etiology
The exact cause of this anomaly is unknown but considered to be both genetic and environmental.

## The Role of Retinoic Acid
- Retinoic acid (RA) is produced from vitamin A by an enzyme retinaldehyde dehydrogenase (Raldh) which is important for ontogenesis and homeostasis of numerous tissues.
- However, studies have revealed that the cranio facial anamolies with mesenchymal developmental damage and disrupted neural crest cell migration pattern were reported among mothers with an ingestion of high doses of vitamin A during gestation period. 
- Dupe et al.: Using a mouse model, they demonstrated that Raldh3 knockout suppressed RA synthesis and caused CA via following proposed mechanisms:
- Over-expression of fibroblast growth factor 8 (FGF-8),
- Persistence of nasal fins whose rupture normally allowed the communication between nasal and oral cavities
- Furthermore, they demonstrated that the CA in the Raldh knockout mice could be prevented by maternal treatment of RA.
- The role of FGF-8 in CA development was further supported by the prevalence of CA among patients with craniosynostosis syndromes due to the raised levels of FGF-8 expression.

## The Role of Thioamides
- Thioamides: Methimazole, carbimazole, and propylthiouracil, are commonly used as medical treatment for hyperthyroidism.
- Several case reports have been published demonstrating the significant association of CA in the newborns with the maternal use of thioamides for the hyperfunctioning thyroid. 
- Moreover, Barbero et al. conducted a case- control study which further concluded the positive relation of prenatal exposure to methimazole for the maternal hyperthyroidism with CA development.
- Methimazole crosses the placenta and hence, enters the fetal circulation which in turn reduces the fetal T4 levels. Therefore, infants born with CA have shown a marked decrease in their T4 levels.
- Teratogenic syndromes causing bilateral CA includes: 
- Methimazole embryopathy
- Carbimazole embryopathy
- However, it is not completely supported because of lack of significant evidences.
- Maternal Hyperthyroidism: Contrarily, based on the thorough study of case reports and critical literature reviews, it was stated that the maternal hyperthyroidism rather the methimazole treatment might be underlying the causal factor for CA.
- Elevated thyroid-stimulating hormones (TSH) level was associated with increased level of FGF, FGF receptor, and other proliferating growth factors, which hypothetically form the pathological basis for CA development. 
- Hence, more research studies are required to further delineate the causes and pathogenesis of CA.

## Excessive Coffee Intake 
Excessive consumption of coffee in the form of more than 3 cups/day increases the chances of CA by interrupting the membrane rupture which leads to an outgrowth of palate towards the medial side and further blocks the communication between the nasal cavities and the pharynx.

## Genetics
- Familial cases: About 8%. 
- Multifactorial trait: The fact is supported by both affected successive and single generations. 
- CHARGE syndrome: The abnormalities in the chromodomain helicase DNA binding protein-7 (CHD7) gene have been identified in 64% of patients diagnosed with CHARGE, and hence, allowing screening of the gene for patients with CA and other related anomalies. However, the exact function of the CHD7 gene is largely unknown. 

# Differentiating Choanal atresia from other Diseases
Following conditions listed in Table 6 must be ruled out in any neonates, infant or child presented with acute or frequent episodes of nasal or upper airway obstruction.
Table 6 lists the differential diagnosis for choanal atresia:

# Epidemiology and Demographics
- Rule of 2:1 states the ratio of unilateral to bilateral CA, female to male and the right sided to the left sided CA.
- The incidence is 1:5,000 to 1:8,000 per live-born children.
- Although its incidence is rare, it represents the most common congenital abnormality of the nose. 
- Maternal age and parity does not affect the frequency of this congenital anomaly.
- Slightly increased risk exists in twin pregnancy.
- It is observed with equal frequency among all races and hence, no racial or ethnic preference is seen.

# Risk Factors
- The relation of risk factors and its implications is always complex. A risk factor increases the predisposition towards a disease in comparison to an individual with no risk factors. However, some risk factors are more important than others; hence, acquiring a single or multiple risk factor does not guarantee the disease development. Contrarily, absence of a risk factor does not ensure the disease free state.
- 2012: An epidemiological survey studied atrazine a commonly used herbicide in the US to treat agricultural crops, and stated that women living in the counties in Texas with the highest levels of this chemical were 80 times more likely to give birth to neonates with CA in relation to women who lived in the areas with its lowest levels.
- 2014: Another epidemiological National Birth Defects Prevention Study (NBDPS) summarized the higher association between the increased development of CA and exposure to second-hand-smoke, coffee consumption, high maternal zinc and B-12 intake, and use of thyroid medications.
- To sum up, the risk factors for the development of CA are listed below:
- Exposure to  endocrine disrupters such as chemicals (atrazine) and medications (methimazole) during gestation.
- Exposure to secondhand smoke during gestational period.
- Excessive consumption of coffee by pregnant mothers exposes the developing fetus to caffeine 
- Elevated levels of vitamin B-12 and  zinc in a pregnant woman exposes the fetus to the same 
- Multiple pregnancies such as twins carries a higher risk 
- Presence of certain congenital disorders that are associated with CA including Crouzon syndrome, Antley-Bixler syndrome, and Pfeiffer syndrome further increase its chances of development.

# Screening
When neonate/infant/child presented with a nasal/upper airway obstruction or respiratory distress, CA must be screened with other differential diagnosis and anomalies.

# Clinical Associations and Complications
Any condition that causes significant depression of the nasal bridge or midface retraction due to underlying genetic or environmental factors can be associated with it.
Table 7 lists the clinical associations and complications of the choanal atresia:  

## CHARGE Syndrome 
- The most commonly associated congenital anomaly.
- Choanal atresia is present in 10 to 30% of CHARGE syndrome cases.
- It elaborates as following:
C- Coloboma: of the iris, choroid, and/or microphthalmia
H- Heart disease: such as atrial septal defect (ASD) and/or conotruncal lesion
A- Choanal atresia
R- Mental and growth retardation
G- Genitourinary abnormalities: such as cryptorchidism, microphallus, and/or hydronephrosis
E- Ear deformities: associated deafness (the external, middle, and/or inner ear may be involved).
- C- Coloboma: of the iris, choroid, and/or microphthalmia
- H- Heart disease: such as atrial septal defect (ASD) and/or conotruncal lesion
- A- Choanal atresia
- R- Mental and growth retardation
- G- Genitourinary abnormalities: such as cryptorchidism, microphallus, and/or hydronephrosis
- E- Ear deformities: associated deafness (the external, middle, and/or inner ear may be involved).

# Prognosis
- The prognosis is usually considered to be very good with timely and effective management unless other complex syndrome associations seen.
- Full recovery is expected with no possibility for any long term problem in both groups of patients. 

# Clinical presentation
Clinical presentation of CA varies from acute airway obstruction to chronic recurrent sinusitis depending on whether CA is unilateral, bilateral, or associated with other coexisting airway abnormalities.    
Table 8 elaborates and compares both forms of Choanal Atresia: Bilateral and Unilateral::

## Effect of CA on the facial structures growth 
- The face, specifically the maxilla and mandible, grows in a dynamic fashion throughout childhood under the influence of bony deposition and resorption, soft-tissue contouring, and hormonal influences. In a reciprocal fashion, the skull base or neurocranium influences midfacial development via the growth of the sinuses, which in turn influence the skull base. Displacement of these structures of the nasomaxillary complex occurs in horizontal, vertical, and anteroposterior axes. These changes ultimately affect the proportions of the face and the morphology of all other facial structures, including the upper airway. Hence, an upper airway obstruction while breathing is common because the intraoral airway has foreshortened due to abnormal placement of anterior choanal aperture, and further the diagnostic visualization of the laryngeal structures becomes difficult. Moreover, a chronic case of CA may progress to the development of obstructive sleep apnea later in life.

## CA with Multiple Congenital Anomalies
- Other airway abnormalities: About 34% have other respiratory anomalies such as tracheomalacia, laryngomalacia, and subglottic stenosis 
- Craniofacial abnormalities: About 21% had it in the form of CHARGE, Treacher Collins, Pfeiffer, Apert, Mandibulofacial dysostosis, and Crouzon syndromes. 
- Hence, these subgroup of patients always presents with more acute and severe respiratory symptoms due to the underlying complex airway abnormalities; and hence, they requires stable alternative airway management such as tracheostomy in addition to the surgical correction of CA.

# Diagnosis
- The diagnosis and management of CA requires the combined and coordinated efforts of both the neonatologists and otolaryngologists. Due to its associations with other syndromes (Table 7), infants born with CA often need other subspecialty evaluations for an interprofessional approach from the departments of cardiology, ophthalmology, geneticists, gastroenterology, etc in the multidisciplinary settings especially for Pediatric Airway Disorders.
- A thorough diagnostic work up is required to rule out other clinical conditions (Table 6) to arrive at a definitive diagnosis and to make a timely diagnosis as if left unestablished till later ages, it tend to impair the quality of life through repeated hospital visits.
- Aero-digestive evaluation:  An infant diagnosed with CA must be evaluated for both airway and feeding issues which need to be addressed by speech pathologists and GI specialists respectively.
- Following methods can be employed to diagnose the condition accurately.
- Assessment of detailed history including the maternal drug intake history and symptoms should be done as mentioned in Table 8.
- A thorough diagnostic physical and radiological examination procedures should be performed as listed below. 
- Ultrasonography of the cardiac and renal systems can be conducted for the possible syndromic associations.
- Breath sounds can be heard with either a stethoscope or a Toynbee auscultation tube to detect the aerated lung fields.
- Air can be gently blown into each nasal cavity with a Politzer bag to observe any degree of nasal obstructive signs.

## Suction catheter test 
- After performing proper preparation by the use of nasal topical decongestants and nasal suctioning, a fine six or eight French suction catheter introduced into the nose via each nostrils and into the child's oral cavity.
- If there is no atresia, the catheter will effortlessly pass through the nasal cavity into the nasopharynx.
- The distance of encountered resistance can provide insights into the etiology of nasal obstruction.
3-5 cms from the anterior nares/alar rim: A typical solid feeling would be felt at this point and possibly indicates obstruction at the posterior choanal level.
1-2 cms from the anterior nares/alar rim: If obstruction is encountered at this distance, then traumatic deflection of nasal septum due to trauma during delivery or inferior turbinate pathologies might be the pathologies. Nasal decongestants such as oxymetazoline/xylometazoline can be used to shrink the obstruction caused by mucosal edema.
- 3-5 cms from the anterior nares/alar rim: A typical solid feeling would be felt at this point and possibly indicates obstruction at the posterior choanal level.
- 1-2 cms from the anterior nares/alar rim: If obstruction is encountered at this distance, then traumatic deflection of nasal septum due to trauma during delivery or inferior turbinate pathologies might be the pathologies. Nasal decongestants such as oxymetazoline/xylometazoline can be used to shrink the obstruction caused by mucosal edema.
- Hence, an inability to pass nasogastric tube through nasal cavity beyond 3-4 cm despite aerated lungs on chest radiograph confirms the diagnosis. However, care must be taken in patients with other craniofacial abnormalities to prevent intracranial passage of the catheter.

## Cotton wisp test 
- Movement of a wisp of cotton wool held directly underneath the nares while the closed mouth during inspiration and expiration. It would move in the presence of free air flow; however, the lack of movement indicates the probable obstructive diagnosis.

## Laryngeal mirror test 
- A laryngeal mirror held under the nares will reveal nasal misting in patients with patent nasal airways. Contrarily, the absence of fog on a mirror when it is placed under the one nostril after the other to check for fogging supports the CA diagnosis.

## Acoustic rhinometry 
- Acoustic rhinometry can be used for the diagnosis, but is especially helpful in the postoperative period to check the patients on restenosis or postoperative nasal complications.

## Methylene blue dye test 
- Administration of methylene blue dye into the anterior nasal cavity can be seen passing through the nasopharynx. However, obstruction due to CA will prevent the flow into the nasopharynx and supports the diagnosis.

## Automatic tympanometer 
- An examination using the automatic tympanometer is considered to be simple, minimally invasive, and highly reproducible with 100% sensitivity and specificity rate.

## Genetic Screening 
- The CHD7 gene screening test and other cytogenetic anomalies such as chromosome deletions related to the several syndromes (Table 7) associated with CA can be done.

## Prenatal ultrasound 
- The clinical presentation and diagnosis of CA is usually postnatal, hence the prenatal ultrasound diagnosis is rare, and very few cases have been reported in the literature. However, it can be suspected prenatally in the presence of other nose anomalies such as nasal septal deviation or a single nostril.

## Lateral skull X-ray 
- The traditional method of diagnosis which involves the filling the nose with radiopaque dye with the patient lying in a supine position, and thus, demonstrating the hold-up of the dye in the posterior nasal cavity.

## Nasal Endoscopy
- An appropriate age-related otorhinolaryngology examination is performed after the nasal cavity preparation, an examination in a very small children is performed with the 3.2 mm diameter flexible endoscope. When possible, the 0 and 30 rigid endoscopes are preferred with a diameter of 4.0 mm or 2.7 mm. Direct visualization of the point of obstruction in the nasal passage with a flexible nasendoscope confirms the presence of an atretic plate in the choana. Therefore, it has become the preferred method for confirming the diagnosis.

## CT scan
- CT scan imaging of the paranasal sinuses and skull base is virtually diagnostic modality of choice. It should be done after symptomatic stabilization of the patient in supine position.
- Objective:
- To confirm the diagnosis and its involvement on unilateral or bilateral sides.
- To determine the anatomy of the atretic area, including the width of the vomer bone and the medial displacement of the sides of the lateral wall of the nose.
- To measure the thickness of the atretic plate.
- To determine if any other sites of obstruction or differential abnormalities exist in the nasal, nasopharyngeal or sinus cavities.
- To detect the abnormal anatomy useful for a surgical planning, and in determining the choice of the operative technique to be used.
- Patient preparation before the scanning: A nasal topical decongestant (0.5% xylometazaline) is applied to reduce mucosal swelling 30 minutes prior to the CT scan, and suctioning of the nose done immediately before the CT scan to remove all nasal secretions in order to detect accurate radiological diagnosis due to the difficulty in radiologically distinguishing  a membranous occlusion from mucus in the unprepared nose.
- CT scan technique:
Anatomical landmark: The level of the pterygoid plates in the axial plane. At this level, the width of both posterior choanae at maximum stenosis and the maximum width of the inferoposterior vomer are measured. Below this level, the hard palate is visualised; and above this level, structures within the nasal cavity make measurements difficult.
Scanning angle: The gantry is angled 5 cephalad to a plane parallel to the hard palate to interpret the images for the measurements of the posterior vomer, the choanal openings, and the shape of the posteromedial maxilla.
Partial skull ossification: Conventional bone-window settings may not show the bony margins; however, a high resolution bone filters may overcome this problem. Hence, 1 to 1.5 mm thick noncontrasted scans are done contiguously.
- Anatomical landmark: The level of the pterygoid plates in the axial plane. At this level, the width of both posterior choanae at maximum stenosis and the maximum width of the inferoposterior vomer are measured. Below this level, the hard palate is visualised; and above this level, structures within the nasal cavity make measurements difficult.
- Scanning angle: The gantry is angled 5 cephalad to a plane parallel to the hard palate to interpret the images for the measurements of the posterior vomer, the choanal openings, and the shape of the posteromedial maxilla.
- Partial skull ossification: Conventional bone-window settings may not show the bony margins; however, a high resolution bone filters may overcome this problem. Hence, 1 to 1.5 mm thick noncontrasted scans are done contiguously.
- CT scan findings: 
- Narrowing of the posterior nasal cavity with medial bowing and thickening of the lateral wall of the nasal cavity with airway width < 3 mm.
- Impingement and thickening  at the level of the anterior aspect of the pterygoid plates
- Enlargement of the posterior portion of the vomer, with or without a central membranous connection. In patients less than 8 years of age, the vomer generally measures less than 0.23 cm in width and should not exceed 0.34 cm; in children over 8 years, the mean vomer width is 0.28 cm and should not exceed 0.55 cm.
- The mean width of the posterior choanal airspace in the newborn measured from the lateral wall of the nasal cavity to the vomer is 0.67 cm, increasing to 0.86 cm at 6 years and to 1.13 cm by 16 years of age.
- An air-fluid level of the nasal secretions above the obstruction point can be seen.
- Membranous atresias: Soft-tissue densities will be seen in the posterior choanae, and noticed narrowing of the posterior choanae just anterior to the pterygoid plates.
- Bony atresia: The thickness of the atretic plate should be taken for surgical repair planning.
- Disadvantages: The main disadvantages of using CT in pediatric populations are:
- High radiation exposure dose: Due to an inadequate positioning of infants in such an age group while achieving a scanning angle and imaging plane necessitates the repetition of the scan; and hence, subsequently results in an increased exposure of the radiation dose.
- Sedation: Need for sedation to avoid movement artifacts which render the examination of fine details less reliable. However, the contrast material used in the nose will help to overcome it.
- Childs lens: The angle of the imaging plane might enhances the risk to it.

# Treatment
- The patient should ideally be managed in a neonatal or paediatric intensive care unit with a combined supportive, medical and surgical care. However, the treatment is essentially surgical which can be divided into emergent and elective definitive categories.

## Objectives
- To restore choanal patency,
- Avoid damaging interference to the surrounding normal craniofacial structures,
- To minimize invasiveness and postoperative complications,
- To avoid recurrences.

## Systematic treatment approach
- Establish an immediate oral airway to ensure breathing
- Membranous atresia may be perforated upon passage of nasogastric tube
- Surgical CA repair for alleviating respiratory symptoms and feeding difficulties
- Postoperative scars, complications, & incomplete resection of atresia plate evaluation with bone CT scans

## Severity assessment
- Assessment is done by evaluating its laterality (unilateral or bilateral), the degree of obstruction affecting the child's breathing and feeding, and its associations with other anomalies; hence, the treatment can be further divided into mild and severe cases.
- Treatment for mild cases: In the mild cases with no significant respiratory distress or feeding difficulty; treatment includes the following:
The neonate should be kept under close observation and provided with supplemental oxygen periodically.
The nasal passages should be maintained by administering the nasal saline to keep the nasal linings healthy by clearing the discharge and preventing any further impediments to nasal breathing.
Parents can opt to delay surgical correction of the nasal structure until the child is older to develop the regional anatomy more similar to that of the adults.
In some of the unilateral cases, the surgical treatment can be delayed until the infant is at least 6 months old and weigh more than 2kgs as it allows better operative field and opportunity for control during surgery.
However, it should be ideally fixed before 5 years of age in order to avoid persistent unilateral nasal drainage which can be socially and medically problematic.
- The neonate should be kept under close observation and provided with supplemental oxygen periodically.
- The nasal passages should be maintained by administering the nasal saline to keep the nasal linings healthy by clearing the discharge and preventing any further impediments to nasal breathing.
- Parents can opt to delay surgical correction of the nasal structure until the child is older to develop the regional anatomy more similar to that of the adults.
- In some of the unilateral cases, the surgical treatment can be delayed until the infant is at least 6 months old and weigh more than 2kgs as it allows better operative field and opportunity for control during surgery.
- However, it should be ideally fixed before 5 years of age in order to avoid persistent unilateral nasal drainage which can be socially and medically problematic.
- Treatment for severe cases: In severe cases carrying life threatening risk usually because of bilateral CA, the delay in treatment should be avoided.
Surgery should be performed as soon as the patient is stable and has completed evaluation for other anomalies.
Different surgical approaches are available and selected on case to case basis.
- Surgery should be performed as soon as the patient is stable and has completed evaluation for other anomalies.
- Different surgical approaches are available and selected on case to case basis.
- To sum up, whether or not surgery is performed, if an infant suffers from CA, a periodic evaluation is necessary to ensure normal upper airway breathing and feeding habits in both preoperative and postoperative period.

## Airway Management  
- It is an initial goal of treatment especially for infants with bilateral CA by inserting an oral airway to break the seal formed by the tongue against the palate to have a tide over an immediate crisis.
- An oral airway provides a temporary secure of several weeks in a newborn with bilateral CA and severe respiratory distress.
- Surgery can be delayed for bilateral CA due to the presence of an innate reflex for nasal breathing and possibility of establishing and maintaining a patent airway with the use of a McGovern nipple or a cannula of Guedel or a standard feeding bottle teat or dummy with the tip cut off to facilitate oral breathing.
- The preferred oral airway is McGovern nipple, an intraoral nipple with a large opening by cutting its end off, which is placed in the mouth and tied around the infants occiput. A small feeding tube can be placed through another hole in the nipple or alongside the nipple to provide feeding needs. This helps the child to gain adequate weight for withstanding corrective surgical procedures.
- It provides the short-term benefits by the effect of stenting the oral cavity to open and allow mouth breathing; however it is not a permanent treatment.
- If a patient still fails to maintain an adequate airway on it, an endotracheal intubation must be performed as the initial management.
- A tracheostomy may be required in patients with severe comorbidities, but it is not necessary in cases of isolated or even bilateral CA.

## Role of tracheostomy
- Indications:
Fail to adequately maintain an oral airway.
To defer the definitive surgical treatment in patients with other comorbidities such as cardiopulmonary instability and multi-level airway obstruction.
- Fail to adequately maintain an oral airway.
- To defer the definitive surgical treatment in patients with other comorbidities such as cardiopulmonary instability and multi-level airway obstruction.
- Patients with bilateral CA and CHARGE syndrome are more likely to fail atresia repair because of the following reasons:
- More contracted nasopharynx in a lateral and/or vertical dimension,
- Narrower posterior choanal region than those with isolated CA, and
- Poor tongue/pharyngeal muscle control.
- Moreover, Asher et al. in their retrospective review of patients with CHARGE syndrome suggested that an early repair of their CA was rarely successful as patients had a propensity for airway instability during the operative time predisposing them to hypoxic events. 
- Therefore, recommended early tracheotomy rather than early CA repair to secure the airway for CA patients with CHARGE syndrome.

## Feeding Issues 
- Do not feed in the cases where there is high index of suspicion for CA.
- A feeding orogastric tube is required until surgical correction of the atresia is performed due to higher risk for aspiration.

## Timing of Surgery
- The exact timing of surgery is variable and decided upon studying the entire case scenario.
- If the infant learns to breathe orally, surgery can be delayed for a while.
- Urgent surgery required in following cases: 
- Bilateral CA;
- Symptomatic unilateral CA;
- Syndromic babies with respiratory complications from unilateral atresia.
- Delay surgery till the child reaches its first birthday in asymptomatic unilateral atresia because of the following:
- This allows the surgery site to enlarge thereby reducing the risk of post operative restenosis.
- Blood loss is reduced.
- Older infants tolerate stenting better than young ones.
- The younger the patient, the higher the risk of intraoperative and postoperative complications and re-stenosis.

## Use of Anaesthesia 
- The anesthetic approach depends on the child's condition. In general, intravenous induction with a muscle relaxant of intermediate duration, endotracheal intubation with an oral Right Angle Endotracheal (RAE) tube, and maintenance with an inhaled agent and opioid or propofol and remifentanil infusion preferred.

## Surgical Approaches
- Since Emmert's initial trocar perforation in 1854, the five different surgical approaches to correct CA have been described which includes the following:
- Transnasal,
- Transpalatal,
- Transseptal,
- Sublabial trans-septal,
- Transantral and
- External rhinoplasty.
- As per the research done in March 1999 by American Society of Pediatric Otolaryngology (ASPO), the most used techniques in descending order are:
- Transnasal with endoscope use,
- Transpalatal perforation with Fearon dilator,
- Transnasal with microscope use,
- Transnasal with laser use
- The transasal technique is considered better than the transpalatal approach.

## Transpalatal approach 
- This approach was the most frequently used to reach the area of CA through the roof of the mouth until the advent of the endoscopic endonasal approach.
- Indications:
- Abnormally developed skull base;
- Thick atresia plate;
- Associated craniofacial anomalies; and/or
- Bilateral CA
- Operating procedure: This procedure is conducted in a full sedation with the use of a general anaesthesia. A Dingman-Denhardt mouth gag with the infant tongue blade is used. The palate is injected with 0.5% lidocaine and 1:200,000 epinephrine in the area of the mucosal incision to serves the dual purpose of flap elevation and required hemostasis during the entire surgical procedure. A Owens type (U-shaped) mucosal incision  starts from just behind the maxillary tuberosity on one side and then continued medial to the alveolar ridge up to the canine region and further angled back to the nasopalatine foramen. A likewise incision is made on the opposite side; and the mucosal flap is elevated with efforts to avoid any damage to the greater palatine arteries. Nasopharynx and nasal mucosa is elevated up to the edge of the hard palate and preserved. The soft palate is now retracted posteriorly and superiorly to expose the posterior edge of hard palate which is the area for dissection and surgical repair. Then, the palatine bones posterior to the greater palatine foramina, the atresia plates, and the posterior vomer are carefully drilled away using a kerrisons punch or drill. Two 14 or 16 French catheters are passed simultaneously into each nostril to check the patency of the newly created choanae. The preserved mucosa is then used to cover the superior and inferior surfaces of the newly formed choanea and then sutured in place to cover the bone. Stents are usually left in-situ for 4 weeks. 
- Advantages:
- Better field of visualisation and exposure
- Both hands are free
- Shortened stenting duration (a portex endotracheal tube can be cut and used as a stent)
- Reduced failure rate
- Disadvantages:
- The incisions made are similar to those for a cleft palate repair and can have a banding effect on maxillary growth due to scar formation. Hence, most surgeons prefer to wait for some teeth to appear in occlusion to use this approach at approximately 12-18 months of age.
- Stunted palatal growth seen in 50 % of operated patients
- An injury to the greater palatine artery can result in an increased blood loss
- Postoperative complications: restenosis of the choanae, palatal fistulas, flap necrosis, bleeding, fistulas, infections, defective growths of the jaw and the palate bone, and orthodontic problems such as cross bite. 
- Postop Care:
- The parents must be taught to maintain the patency of stents by frequent suctioning and a saline-moistened pipe cleaner or cotton applicator 3 to 6 times a day.
- Antibiotics and decongestants are prescribed in suspicion of rhinitis
- Regular follow up should be advised until the stents are removed.

## Transseptal approach
- It is effective but rarely used due to the resultant impairment of facial growth in infants. However, it is considered effective in patients older than 8 years diagnosed later with unilateral CA.
- An operative key point is the need to remove the posterior portion of the vomer.
- It permits better correction of any septal deviations, resection of the posterior part of the vomer, and preservation of mucosal flaps for coverage of the bleeding area.
- Complications of transeptal approach:
- Pressure necrosis of columella
- Plugging of stent
- Displacement of stent
- Palatal dehiscence
- Maxillary hypoplasia causing malocclusion
- Granulation tissue formation around the stents.

## Sublabial approach
- The sub labial, trans-septal access has advantages and disadvantages similarities to the trans-septal approach, and it further reduces the likelihood of postoperative granulation tissue formation and restenosis by avoiding surgical trauma to nasal mucosa.

## Transantral approach
- Transantral access is the least-used approach because it requires a well-developed maxillary sinus which is not found in infants, many older children, and even adults with CA.  However, it permits an adequate exposure of the surgical field, allowing a quick check for any bleeding source, and reduces the risk of damaging the sphenopalatine arteries, veins and nerves; but can significantly increase the risk of deformities of growing structures such as the maxilla and upper teeth.

## Transnasal approach  
- The growing experiences and modern refinements in both instrumentation and techniques in endoscopic sinus surgery have encouraged many CHOP surgeons to prefer the use of the endoscopic endonasal technique for the CA repair as it does not affect the growth of the mandibular arch, causes no malocclusions or cosmetic alterations to the face.
- For stable infants with CA, the endoscopic endonasal technique should be considered the first choice for the surgical treatment for membranous atresia or where bony plate is thin which involves the perforation of the atretic lamina followed by dilatation and full choanal reconstruction.
- Operating procedure using endoscopes:
The surgery is performed under general anesthesia using a combination of tiny scope, dilators, sinus instruments, ear curettes and drills. A self retaining nasal speculum is used to expose the nasal cavity and the atretic plate with minimal trauma to the nasal vestibule. For the membranous atresia, a simple perforation of the same under endoscopic guidance would suffice. The nasal cavity is decongested using 4% xylocaine with adrenaline in the concentration of 1 in 10,000 concentration. A 0 endoscope is used transnasally with a simultaneous view of the nasopharynx through a transoral 120 endoscope. It is important to use both the transnasal and transoral views in order to avoid potentially entering the anterior skull base. Under endoscopic guidance, a mucosal incision is made and the mucosal flaps are elevated exposing the posterior vomer and lateral pterygoid lamina. A diamond burr on an angled hand piece is used to drill the atretic bony plate. It is perforated at the junction of the hard palate and the vomer. Incidentally, this is the thinnest part of the atretic plate. To improve visualization, the inferior turbinate can be out fractured or even be trimmed. After drilling, care is taken to preserve the mucosal flaps. A silastic stent is placed into each nostril passing through the drilled neo-choanae. This helps in reducing the incidence of restenosis and crusting at the site of the bony atresia. Stent is kept in place for atleast 6 weeks. Opening made should be large enough to allow smooth passage of suction catheter. 3-4 size Endotracheal tube can be used as stent to prevent restenosis and maintain patency while the area heals. The size of ET tubes should be choosen carefully to prevent restensosis and nasal regurgitation. However, a recent meta-analysis found similar success rates for bilateral CA repair regardless of whether stents were used; and hence, stenting is not required in all the cases. Thus, these stents will be removed at the bedside or during an office visit in weeks to months after demonstrating the child for an airway stability and feeding evaluation.
- The surgery is performed under general anesthesia using a combination of tiny scope, dilators, sinus instruments, ear curettes and drills. A self retaining nasal speculum is used to expose the nasal cavity and the atretic plate with minimal trauma to the nasal vestibule. For the membranous atresia, a simple perforation of the same under endoscopic guidance would suffice. The nasal cavity is decongested using 4% xylocaine with adrenaline in the concentration of 1 in 10,000 concentration. A 0 endoscope is used transnasally with a simultaneous view of the nasopharynx through a transoral 120 endoscope. It is important to use both the transnasal and transoral views in order to avoid potentially entering the anterior skull base. Under endoscopic guidance, a mucosal incision is made and the mucosal flaps are elevated exposing the posterior vomer and lateral pterygoid lamina. A diamond burr on an angled hand piece is used to drill the atretic bony plate. It is perforated at the junction of the hard palate and the vomer. Incidentally, this is the thinnest part of the atretic plate. To improve visualization, the inferior turbinate can be out fractured or even be trimmed. After drilling, care is taken to preserve the mucosal flaps. A silastic stent is placed into each nostril passing through the drilled neo-choanae. This helps in reducing the incidence of restenosis and crusting at the site of the bony atresia. Stent is kept in place for atleast 6 weeks. Opening made should be large enough to allow smooth passage of suction catheter. 3-4 size Endotracheal tube can be used as stent to prevent restenosis and maintain patency while the area heals. The size of ET tubes should be choosen carefully to prevent restensosis and nasal regurgitation. However, a recent meta-analysis found similar success rates for bilateral CA repair regardless of whether stents were used; and hence, stenting is not required in all the cases. Thus, these stents will be removed at the bedside or during an office visit in weeks to months after demonstrating the child for an airway stability and feeding evaluation.
- Caution: While performing this procedure, caution must be taken not to injure the sphenopalatine vessels behind the middle turbinate.
- Advantages:
- This process is faster and easier as it offers a direct approach to the atretic plate;
- Reduces intraoperative bleeding;
- Can be performed in children of all ages who do not have associated external nasal deformities;
- faster post-operative recovery, reduces hospitalization time, and lowers morbidity;
- Child can be immediately breast fed;
- Child can be discharged on the postop 3rd day
- Disadvantages:
- Vision is highly limited especially in the new born
- Inability to adequately remove enough of the posterior vomerine septal bone and prevent restenosis
- Longer stenting time
- Endoscopes do not offer binocular vision
- Can not be done safely with good results on patients with multiple nasal and nasopharyngeal anomalies.

## Rhinoplasty
- Correction of CA using an external rhinoplasty approach is usually restricted to unilateral cases when the child is 1 year of age or older. The medial crura are separated, and the cartilaginous edge of the nasal septum is exposed. The mucoperichondrium and the mucoperiosteum are elevated to the region of the atresia. The atresia plate is then removed, and the posterior portion of the vomer is resected.

## Stenting  
- The effectiveness of using stents after CA repair is a controversial topic with some of the major complications originating following its use.
- Formation of granulation tissue
- Crust formation
- Septal perforation
- Persistent nasal discharge
- Foreign body tissue reaction
- Nasal alar erosion
- Columellar pressure necrosis

## Mitomycin-C
- It is an aminoglycoside which inhibit fibroblast growth and migration; and it's topical application was proposed to reduce restenosis risk after surgery and improve the healing process as it has not caused any systemic adverse effects and anesthetic complications. However, its use is still controversial.

## Postoperative monitoring 
- After CA is surgically corrected, the surgeon is often faced with the problem of restenosis; however, recent innovations have reduced its rate.
- Newer endoscopic techniques with powered instrumentation along with the use of stenting and mitomycin-c have enhanced the safety and efficacy for CA repair.
- The postoperative period is generally well for patients with unilateral obstruction and require no special monitoring. However, infants undergoing bilateral repair can exhibit partial or intermittent upper airway obstruction that persists for some time and thus, the infant should be observed closely in the ICU with appropriate monitoring until breathing dynamics have normalized.

## Surgical Complications
- Factors resulting in the failure of microendoscopic surgery for the CA treatment are as follows:
- Surgery performed too early,
- Inadequate area of surgery exposure due to association with other malformations,
- Inappropriate surgical technique with insufficient removal of the atresial plate and the posterior nasal septum, and
- Inadequate postoperative care.

## Success Rate 
- Successful CA surgical outcomes are influenced by the presence/absence of following factors:
- Nasopharyngeal reflux,
- GERD,
- Age <10 days associated with limited visualization of the nasal area and limited resection of the vomer,
- Bilateral CA with purely bony atretic plate, and
- Associated syndromic malformations.

## Prevention
- Currently, there are no known methods or guidance reported for the prevention of CA. However, maternal mothers should consider the general health measures for minimizing the risk factors for the condition as listed in the "Risk Factors" section. 

## Tips to remember 
- Regardless of surgical approach, the key to a successful outcome is to create a large 3-dimensional opening by a combination of following:
- Puncturing the membranous obstruction,
- Widening the medial bony thickening of the medial pterygoid plate, and
- Thinning the thickened vomer
- Postoperative considerations:
- After successful CA surgery, the child should be extubated and managed in a general paediatric ward with regular nasal suctioning
- Start oral feeding as early as possible
- Postoperative nasal decongestant drops (0.5% xylometazalone) should be advised for a week
- Saline and steroid drops should be used for 2 weeks to reduce postoperative inflammation and granulations