Choanal atresia

By

Dr. T. Balasubramanian M.S. D.L.O.

Choanae are  otherwise known as posterior nasal apertures.  Air which is breathed through the nose finds its way into the lungs through this aperture.  In some children the choanae may be congenitally closed.  This condition goes by the name choanal atresia.  Choanal atresia may be either unilateral or bilateral.  Unilateral choanal atresia is invariably not identified early, and it needs constant suspicion for its identification.  On the contrary bilateral choanal atresia is a medical emergency, wherein the pateint's breathlessness increases when the child starts to cry.  This condition common affects one in 8000 live births.  Female children are affected twice as common as male children.

     In bilateral choanal atresia the child is in acute respiratory distress which improves when the child starts to cry, since it takes in air through the mouth by passing the obstructed choanal airway.

Neonates are obligate nasal breathers for the first 6 weeks. When bilateral choanal atresia is present in a neonate, emergency

Types of choanal atresia:

1. Bony - 90%

2. Membranous - 10%

This atretic plate of bone / membrane are generally situated just in front of the posterior end of nasal septum.  The congenital choanal atresia should not be considered as an isolated plate of bone but as one component of a skull base anomaly developing between the 4th and 12th weeks of gestation.

Embryology:

     Nose proper develops from neural crest cells.  These cells commence their caudal migration to reach the midface by the 4th week of gestation.  Two nasal placodes develop inferiorly, and they are divided into the medial and lateral nasal processes by the presence of nasal pits.  The medial nasal process give rise to the nasal septum,  philtrum and premaxilla of the nose, whereas the lateral processes form the sides of the nose. Inferior to the nasal complex, the stomodeum, or future mouth, forms.  Nasobuccal membrane separates the oral cavity inferiorly from the nasal cavity superiorly. As the olfactory pits deepen, the choanae are formed. Primitive choanae form initially, but with continued posterior development, the secondary or permanent choanae develop. By 10 weeks, differentiation into muscle, cartilage, and bony elements occurs. Failure of these carefully orchestrated events in early facial embryogenesis may result in multiple potential anomalies, including choanal atresia, medial or lateral nasal clefts, nasal aplasia, and polyrrhinia.

Four theories for the development of choanal atresia:

1. Persistence of a buccopharyngeal membrane from the foregut.

2. Persistence of the nasobuccal membrane of Hochstetter - most
commonly accepted theory.

3. The abnormal persistence or location of mesodermal adhesions in the
choanal region.

4. A misdirection of mesodermal flow secondary to local genetic
factors better explains the popular theory of persistent nasobuccal
membrane

Boundaries of the atretic plate:

1. Superior - Under surface of the body of sphenoid

2. Lateral - Medial pterygoid lamina

3. Medial - vomer

4. Inferior - Horizontal plate of palatine bone

Additional anomalies seen are:

1. The palatal arch is accentuated

2. Lateral and posterior nasal walls sweep inwards

3. The naso pharynx is narrowed

Associated other anomalies:

CHARGE association - (C- coloboma; H- congenital heart disease; A- atresia choanae; R- retarded growth and development; G- genital anomalies
in males; E-ear anomalies and deafness).  60% of these patients have bilateral choanal atresia while the rest present with unilateral atresia
 

Symptoms:

In patients with bilateral choanal atresia, mouth breathing is seen.  The patient is unable to clear the nasal cavity of its secretions.   There is also associated loss of sensation of smell.  Patient's with unilateral atresia has c/o unilateral nasal block associated with thick tenacious secretions which cannot be cleared fully.  These patients commonly have foul smelling breath either due to mouth breathing and its attendant drying effects, or due to the inability to clear the nasal cavity of its secretions.  These patients also have associated change in voice due to loss of normal nasal intonation i.e. Rhinolalia clausa.  The respiratory obstruction is cyclic - as the child falls asleep the mouth closes and a progressive obstruction starting 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.  Child with bilateral atresia has difficulty in sucking milk. 

Clinical examination:

1. Failure to pass a # 6 to 8 French plastic catheter through the nares into the pharynx. (a typical solid feeling will be encountered at
the level of the posterior choana approx. 3-3.5 cm from the alar rim).  If obstruction is encountered within 1 - 2 cms from the nasal rim it is probably due to traumatic deflection of nasal septum during delivery.  If obstruction is due to mucosal oedema it can be shrinked using nasal decongestants like oxymetazoline / xylometazoline.

2. Wisps of cotton may be placed in front of the nasal cavity and the movement of air flow can be ascertained.

3. Placing methylene blue in the nares and not visualizing it within the pharynx.
 

Investigations:

The current investigation of choice is CT and gives information whether the obstruction is membranous or bony and the actual structures involved and its thickness.  It demonstrates  thickening of the vomer, bowing of lateral wall of the nasal cavity and fusion of bony elements in choanal region.  Congenital unilateral atresia is always associated with deviation of nasal septum and thickening of the vomer bone. 

 


CT scan showing choanal atresia

Management:

In bilateral atresia securing the airway takes the first place.  An oral airway may be introduced to tide over the immediate crisis. 

Intraoral nipple - a large nipple can be modified by having its end cut off and then ties are attached to the nipple and placed around the
occiput. This type of airway is called a McGovern nipple and provides an airway through which the baby can breath. A very small feeding tube can
then we passed either through another hole in the nipple or along side the nipple for gavage feeding. This is the preferred method of
establishing an oral airway.

Role of tracheostomy:

This is controversial.  This is one way that must be considered if the patient is unable to maintain the oral airway. 

Surgical management:

Transnasal approach: (using endoscopes): The surgery is performed under general anesthesia.  A self retaining nasal speculum is used to expose the nasal cavity and the atretic plate.  If the atresia is membranous in nature 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. 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.  This procedure was first described by Stankiewicz.  To improve visualisation 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 choana.  This helps in reducing the incidence of restenosis.  Stent is kept in place for atleast 6 weeks.

Caution:

While performing this procedure caution must be taken not to injure the sphenopalatine vessels behind the middle turbinate.

Advantages of this procedure:

1. This process is faster and easier

2. Blood loss is minimal

3. Can be performed in children of all ages who do not have associated external nasal deformities

4. Child can be immediately breast fed

5. Child can be discharged on the 3rd day itself

Disadvantages:

1. Vision is highly limited especially in the new born

2.Inability to adequately remove enough of the posterior vomerine septal bone and prevent restenosis

3. Longer stenting time

4. Endoscopes do not offer binocular vision

5. Can not be done safely and with good results on patients with multiple nasal and nasopharyngeal anomalies.

Transpalatal approach:

This procedure is performed under general anaesthesia.  A Dingman-Denhardt mouth gag with the infant tongue blade is used.  The palate is injected with 0.5% lidocaine with 1:200,000 epinephrine in the area of the mucosal incision. a Owens type(U-shaped) mucosal incision is made
beginning just behind the maxillary tuberosity on one side and then continued medial to the alveolar ridge up to the canine region and then angled back to the nasopalatine foramen. A likewise incision is made on the opposite side and the mucosal flap is elevated taking care not to damage the greater palatine arteries. Mucosa of the nose and nasopharynx is elevated and preserved.  Then the palatine bones posterior to the greater palatine
foramina, the atresia plates and the posterior vomer are carefully drilled away using a diamond burr.  Two 14 or 16 French catheters are passed simultaneously into each nostril to check the patency of the newly created choanea.

     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 left in place for 4 weeks.

Advantages:

1. Better visualisation and exposure

2. Both hands are free

3. Less stenting period  (a portex endotracheal tube can be cut and used as a stent)

4. Less failure rate

Disadvantages:

1. The incisions, which are identical to those for a cleft palate repair, may have a banding effect on maxillary growth due to scar formation. (Therefore, most surgeons prefer to wait to use this approach until some teeth are in occlusion - at approx.12-18 months).

2. Palatal growth can be stunted in 50 % of individuals

3. Increased blood loss

4. Increased risk of development of palatal fistulas post operatively

Care of the post op patient:

1. The parents must be taught to maintain the stents with frequent suction and a saline-moistened pipe cleaner or cotton applicator 3 to 6 times per day.

2. Antibiotics and decongestants are prescribed if there is evidence of rhinitis

3. Patients must be followed up regularly till the stents are removed.