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TITLE:   Congenital Choanal Atresia
SOURCE:  Dept. of Otolaryngology, UTMB, Grand Rounds
DATE:    February 14, 1996
RESIDENT PHYSICIAN:     Kathleen R. McDonald, MD
FACULTY:                Ronald Deskin, MD
SERIES EDITOR:          Francis B. Quinn, Jr., M.D.
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"This material was prepared by resident physicians in partial fulfillment 
of educational requirements established for the Postgraduate Training 
Program of the UTMB Department of Otolaryngology/Head and Neck Surgery 
and was not intended for clinical use in its present form.  It was 
prepared for the purpose of stimulating group discussion in a conference 
setting.  No warranties, either express or implied, are made with respect 
to its accuracy, completeness, or timeliness.  The material does not 
necessarily reflect the current or past opinions of members of the UTMB 
faculty and should not be used for purposes of diagnosis or treatment 
without consulting appropriate literature sources and informed professional 
opinion." 

Congenital Choanal Atresia:

Introduction:

     Choanal atresia is the total obstruction of the posterior
nasal choana, which is the opening between the nose and the
nasopharynx.  It may by unilateral or bilateral.  This is an
uncommon anomaly but is well recognized.  It has an incidence
ranging from one in every 5000 to 8000 live births. Some other
statistics are that it has a female preponderance of 2:1; it is
unilateral to bilateral, 2:1; and there appears to be right side
predominance.
     J.S. Fraser originally published a report in 1910 which
stated the deformity was made up of 90% bony and 10% membranous
atresia.  He had no access to modern workup of computer
tomography.  There is a recent study looking at the CT and
histologic specimens in 63 patients and this showed a 29% pure
bone, 71% mixed membranous and bone, no pure membranous atresia
present.(Brown et al)
     The boundaries of the atresia plate are created by the
undersurface of the body of the sphenoid bones superiorly, the
medial pterygoid lamina laterally, the vomer medially, and the
horizontal portion of the palatal bone interiorly. The bone may
be 1-12 mm in thickness.  Additional bony changes that frequently
occur are an accentuated arch of the hard palate, a sweeping
inward of the lateral and posterior nasal walls and a narrowing
of the nasopharynx by the posterior and lateral pharyngeal walls.

Presentation:

     The obstetrician and pediatrician must have acute awareness
of this diagnosis, especially in the emergent situation of the
bilateral cases in the newborn. A newborn infant is an obligate
nasal breather. The hallmark is the cyclic cyanosis of the
neonate.  Bilateral choanal atresia causes complete nasal
obstruction in the newborn, with immediate onset of respiratory
distress and possible death by asphyxia unless immediate
intervention of the insertion of an oral airway, endotracheal
tube or tracheotomy. The degree of respiratory distress and
cyanosis can be variable.  Asphyxia may be severe in some
patients, but conspicuous only during sucking in others.
     Infants are obligate nose breathers due to the posterior
soft palate covering the oropharynx and the neonate's tongue in
close proximity with the hard and soft palate.  This creates a
vacuum and causes airway obstruction.  With choanal atresia, when
the infant has its mouth closed, it can not inspire and becomes
cyanotic.  When he cries, air flow occurs through the mouth and
the cyanosis disappears.  Mouth breathing becomes possible at
around 4-6 weeks due to a learned response and facial growth.
     Unilateral atresia is rarely a cause of neonate respiratory
distress and is often not recognized at birth.  The most common
presentation is that of a 1 to 2 year old child with unilateral
copious mucoid rhinorrhea or sinusitis.
     Once the diagnosis is made steps must be taken to secure the
child's airway and prevent asphyxiation.  Under these
circumstances, an oral airway, secured with adhesive tape, must
be provided.  An alternative method is a McGovern nipple, which
is a large nipple with the end cut off and an oral airway placed
inside, tied circumferentially around the child's head to
maintain its position in the mouth.  An oral gastric tube must be
placed or the child gavage fed due to the fact that the child can
not breath while feeding.

Diagnosis:

     The diagnosis of atresia is tentatively made by failing to
pass no. 8 french catheter at least 32mm pass the anterior nares
into the oropharynx.  A second test for functional patency is by
holding thin wisp of cotton fibers first in front of one side
then the other, being sure the mouth is closed. Auscultation with
a stethescope is also helpful.  Some have used methylene blue and
assess the passage into the nasopharynx.

Radiological Assessment:

     Computerized tomography is now the method of choice in the
evaluation of congenital choanal atresia.  Both coronal and axial
cuts are helpful in determining whether the disease is unilateral
or bilateral, and the approximate thickness of the bone.  It also
shows the presence and degree of narrowing and stenosis of the
bony nasal cavity.  The knowledge of abnormal anatomy is vital in
preoperative planning and help with choice of surgical technique.
     Other methods of radiographic studies consist of radiopaque
dye inserted into the nose: this shows the presence, but not the
nature, of the obstruction.  Submental vertex tomographic studies
and plain skull films have been used in the past.

Differential diagnosis:

     The differential of nasal obstruction is numerous.  They
include bilateral choanal atresia, generalized swelling of the
nasal mucosa (turbinate hypertrophy or "stuffy nose syndrome"),
encephalocele, tumors including dermoid, hamartoma, chordoma,
teratoma, rhabdomyosarcoma, traumatic birth deformity or
dislocation of the septum.

Congenital anomalies:

     Choanal atresia is associated with other congenital
abnormalities 50% of the time.  This is seen more often with
bilateral atresia rather than unilateral.  The majority of the
children with anomalies tended to have multiple defects, most of
which involve the midline maxillofacial structures in addition to
choanal atresia.  A common anomaly is the CHARGE syndrome.  The
infants have a combination of coloboma of the retina, heart
defects, atresia of the choanae, mental retardation, genital
hypoplasia, ear anomalies and hearing loss.  Cardiac problems
should be suspected, evaluated, and treated; otherwise, they will
complicate surgical correction.  In Teacher-Collins syndrome with
its hypoplastic maxilla and mandible, a tracheotomy should be
considered part of the management of the airway.  Other reported
craniofacial dysmorphisms include Down, Aperts, oral-facial
digital syndromes and Crouzon's Disease.  The atresias associated
with congenital anomalies are more difficult to manage.  Nasal
ethmoidal encephalocele may occur with choanal atresia.

Embryology:

     Johann Roederer in 1755 first to describe posterior nasal
choana obstruction.   Since that time there have been four
theories developed to explain this phenomenon.
The four theories are 1. persistence of the buccopharyngeal
membrane from the fore gut; 2. persistence of the nasobuccal
membrane of Hochstetter(which is the most widely accepted) 3. the
abnormal persistence or location of mesoderm forming adhesions in
the nasal choanal region; and 4. misdirection of mesodermal flow,
secondary to local factors.  The last is the most recent theory
developed in 1982 by Hengerer. This theory is based on the normal
nasal development.
     A review of the normal nasal development (Hengerer et al)
will assist in the understanding of the theory. The development
begins with the migration of neural crest cells from their origin
in the dorsal neural folds laterally around the eye and
transversing the frontonasal process.  It begins the 4th week and
nasal architecture is completed by the 12th week. During this
time the neural crest cells migrate beneath the epithelium
through a meshwork of hyaluronic acid and attach to collagen
filaments within the facial processes.  These pleuropotential
cells then undergo rapid proliferation and differentiation into a
matrix of mesenchymal tissue which will be transformed into
muscle, cartilage, and bone.  Some of these changes may occur
within minutes to hours and require unbelievable precision.
     Using the information of neural crest migration a solid
theory and foundation can be proposed.  Neural crest cell migrate
through meshwork of hyaluronic acid and collagen filaments to
reach a preordained position in the facial process.  It the flow
of these cells is altered with regard to their position or total
numbers, the burrowing of the nasal pits may not create the same
rotation from the ventral dorsal to cephalic caudal plane.  This
altered thinning would likely prevent the break through at the
anterior choana.  Therefore the nasal and palatal processes
surrounding the nasobuccal membrane are the basic factors leading
to the development of a choanal atresia.
     The location of the atretic plate is relatively consistent,
the make up varies.  The finding of islands of cartilage or
membranous bone suggests that the septal or palatal processes
must add some cellular mass to the mesenchymal collection that
began in the region of the primary choana.
     Genetic factors may influence the migration and determine
whether the neural crest cells arrive in this preordained
position in correct numbers or whether defects may exist in their
matrix or migration.

Surgical repair:

     The success of the surgical repair of bony choanal atresia
depends on three variables: thickness of the atresia plate, the
technique of the surgical procedure, and the technique used to
stent the newly created opening.
     The anatomical deformity of congenital atresia can be
divided into four areas.  The first part is the narrow nasal
cavity which can not be surgically improved.  The second defect
is the lateral bony obstruction.  This bone is difficult to
remove and usually only a small portion can be trimmed with a
curette or if via the transpalatal approach a drill is used.  The
area most amendable to surgery is the medial obstruction created
by the vomer deformity.  The success of the operation depends on
adequate removal of the posterior end of the vomer which in
effect moves the choana anteriorly and enlarges the
nasopharyngeal space. The last part is the atretic plate itself.
     The thickness and type of deformity is evaluated via the CT
scan.  The thicker the atretic plate and the more associated
anatomical defects the more extensive the surgery required to
prevent re-stenosis.  This information is very vital to determine
a surgical plan of action.  Once the procedure is completed the
last and very important part is the type and degree of stenting
needed.
     In the past the use of airways to bypass the obstruction was
the treatment of choice until the child learned to by a mouth
breather then repair was performed at 1 year of age.  Now many
otolaryngologists are suggesting immediate surgical repair once
the child is stable.  As stated before the case of bilateral
atresia is emergent and usually is repaired within the first week
to month of life to give the child a safe manageable airway.
Unilateral atresia can be repaired at a later date when the
child's anatomy is larger and the procedure will be technically
less difficult.  Once the infant has been stabilized and all
contraindications to surgical intervention have been ruled out or
corrected, bilateral choanal atresia repair can be performed.
     An overview of the different surgical options is covered.
Their pros and cons are many since this is still a very
controversial area.

Transnasal Approach:

      This is the oldest method of surgical correction.  The nose
and nasopharynx are thoroughly examined with endoscopes.
Beinfield describe a transnasal method using fine mastoid curette
in 1956.  Singleton and Hardcastle then advocated the Zeiss
operating microscope, diamond burrs and silastic stenting.
     The nose is injected with 1/2 percent Xylocaine with
1/200,000 epinephrine.  A self retaining ear speculum will dilate
the nostril up to 4.5 - 5.5 mm and then place parallel to the
floor of the nose to align it with the site of the atresia.
Using an operating microscope or and endoscope the atretic plate
viewed and palpated.  The first step is to make a cruciate
incision in the mucosa and develop an anterior flap using an ear
sickle knife. House round knife is used to elevate the flaps
exposing the bony plate.  The next step is the removal of the
bone using a 4mm diamond burr on an angled handpiece.  Care must
be taken to hug the floor of the nose, drilling parallel to the
hard palate so that the perforation will be between the nose and
the nasopharynx without injury to the clivus and other important
structures such as the eustachian tube, sphenopalatine
neurovascular bundle, sphenoid sinus and maxillary sinus.  The
initial perforation is made in the inferomedial part of the
atretic plate which is usually the thinnest and the safest area
to enter.  The atretic plate is then penetrated exposing the
nasopharyngeal mucosa.  The perforation is enlarged medially by
burring the vomer, laterally by burring the pterygoid plate, and
interiorly by burring the hard palate.  The exposed posterior
mucosa is the incised in a cruciate fashion.  The arms of the
incision are rotated 45 degrees in relation to the arms of the
anterior incision. The flaps are laid down and imbricated at the
time of stenting.

Transpalatal approach:

     This approach was popularized by Owens in 1965.  The
approach is through the palate directly to the atretic plate. A
Dingman, Mclver, or Brown-Davis mouth gag is inserted after the
infant is orally intubated.  The mucosa of the hard palate is
injected with local and a horseshoe-shaped incision is made on
the hard palate 5 mm back from the dental arch.   There are many
incision designs that have been used including midline straight
or s shaped incisions.   Care must be taken posterolateral to
avoid the flaps blood supply from the greater palatine arteries
The subperiosteal elevation is made back to the leading edge of
the hard palate.  A cutting burr is then used to drill the
posterior portion of the vomer and atretic plate.  The mucosa of
the nasopharynx and nasal passage is preserved and then a
cruciate incision is made under direct vision.  Stents are then
place and secured.  The palate is repaired with 4.0 polyglycan
suture.

Transseptal Transantral Approach:

     This approach was developed by Karanjian in 1942 and was
recommenced for patients over 8 years of age.  Performed
concurrently with septal reconstruction and external nasal
surgery.  The advantages to this approach was thought to better
exposure of the operative field, ready control of hemorrhage, and
less danger to sphenopalatine nerve and vessels.  This is not
recommended in younger children due to the potential for damage
to bony growth.
     The approach consist of a gingivolabial sulcus incision to
the premaxilla.  The soft tissue is elevated off the pyriform
aperture and the caudal edge of the septum is exposed.  The
mucoperichondrium on one side of the quadrilateral cartilage is
elevated back to the perpendicular plate of the ethmoid and
vomer, and then back to the atresia plate.  The septal bony
cartilaginous junction is separated and the periosteum is
elevated off the opposite side while swinging the septal
cartilage to one side.  Using the microscope or loupes the vomer
is resected back to the atretic plate, which is perforated and
enlarged with a rongeur.  The nasal soft tissue is then allowed
to fall back into their normal positions, and otic speculum is
place into the nares, and the mucosa over the site is incised in
a cruciate fashion.  A stent is fashioned and secured.

External Rhinoplasty approach for unilateral choanal atresia:

     This surgery is usually performed when the child is older
than one at which time the nose is sufficiently large to allow
access to the atresia plate directly through an external
rhinoplasty approach.  A gull wing external rhinoplasty incision
is made and the columellar flap is elevated.  The medial crus are
separated from the caudal septum and the subperichondrial plane
is elevated off the atretic side.  The quadrilateral cartilage is
detached from the bony septum and maxillary crest and displaced
towards the normal side.  The atretic plate and mucosa is removed
in the usual fashion.

Laser repair:

     The CO2 laser, using repetitive pulse mode has been used to
vaporized the atretic plate.  The average power setting is 6 W
for both soft tissue and bone. The problems seen with the laser
is first the obstruction to the path of the laser beam.   Septal
deviation and large inferior turbinates obstruct the straight
path that the CO2 laser must take.   Occasionally resection of
the posterior septum and turbinates is required to adequately
enlarge the airway.  A more difficult problem encountered is the
high arch palate, which may preclude the beam's hitting the
plate.
     Another laser technique described is using a potassium-
titanyl-phosphate laser fiber passed through the irrigation port
of a mastoid suction irrigator.  The mucosa and bony plate are
then vaporized.

Stenting:

     Stenting of the nasal airway, although necessary, may be a
two-edged sword.  The stent is a foreign body which causes
granulation tissue and inflammation.  It is also present to help
prevent re-stenosis.  The methods commonly used for stenting a
choanal atresia repair are a modified endotracheal tube, movable
stents designed to breaking adhesions or various types of hollow
tubing.  Stenting is achieved by using a 3.5-5.0 mm portex
endotracheal tube, cut to a length that reaches into the
nasopharynx.  Stent material, shape, or diameter are of less
importance than the surgical opening created plus careful mucosal
flap coverage.
     The problem with the current stenting techniques are
premature extrusion, dislodgement, lumen occlusion, formation of
intranasal synechiae, excoriation or erosion of the nares, and
the unsightly aspect of having a stent protruding from the nose.
     This technique was recently published using silastic tubing.
The stent is fabricated using the largest diameter that fits
securely into the nose.  An oval shaped window is cut equidistant
from both ends which serves as a posterior opening.  The tubing
is folded to form up against the perpendicular plate of the
ethmoid bone when the stent is fixed in the nose.  pacemaker wire
is used like a bridal which is secured to the stent.  The arms of
the stent are trimmed to approximately 5mm.  Once seated in place
the pacemaker wire is secured to the nasal spine via a sublabial
incision.  Unilateral atresia is performed similarly except the
tubing is only unilateral exiting 1 cm distally and 5 mm proximal
to the wire entry point.  Removal using brief general anesthesia
is necessary, but the opportunity to determine patency and remove
any accumulation of granulation tissue.   Advantage to stenting
secured sublabially are secure fixation with no visible external
splint.  There is also less irritation to the nasal mucosa and
septal erosion.
     Other stenting techniques consist of fixing the stent by a
suture through the columella, attaching the right and left stent
tubes to each other anterior and posterior to the septum and also
by passing the suture through a hole in the tubing posteriorly
and securing it in front of the columella.  The later allows
removal and cleaning of the tubes.

Post Operative Care:

     Postoperative care involves stent irrigation and routine
sectioning.  The patients are maintained on oral antibiotics
(amoxicillin or a cephalosporin) while the stent is in place. The
stents are left in place for 4-6 weeks.  Some say only 2 week are
necessary to keep good patency and decrease granulation tissue.
At the time of stent removal, examination under anesthesia or
fiberoptic nasopharyngoscope is performed to assess
mucosalization and diameter.  If granulation tissue is found, it
is debrided, cultured and abx are continued.  Systemic steroids
are often used.
     Re-stenosis is common. Many times repeat dilatation with a
urethral sound and  revision surgery is required.

Surgery choice:

     Many physicians preferred to the transnasal approach.  One
reason is that there are multiple anatomical defects which exist
in the nasal architecture other than just an atretic plate.  The
lateral nasal wall is displaced medially and the bony palate is
elevated which together decrease the nasal passage. Bilateral
atresia usually has a smaller side which by using the
transpalatal approach the removal of posterior septum and
drilling of the lateral nasal wall along the pterygoid will give
a enlarged posterior airway.  Another reason for better success
is that the mucosal flaps can be developed and sutured in place
which prevent re-stenosis.  With a thick bony plate the
visualization through the palate approach allows for easy access
to the drilling away of the entire blockage which is not
accessible through a transnasal approach.  Transpalatal approach
allows direct visualization of the operative field.  This helps
prevent disorientation and damage to the base of skull, posterior
pharyngeal wall or spinal cord.  Fewer problems post operative
with re-stenosis and granulation tissue
     Transpalatal approach carries the risk of injury to the
greater palatine neurovascular complex, requires longer operative
time than transnasal is associated with more blood loss,
interferes with normal oral intake in the immediate postoperative
period and requires longer recovery time than transnasal
approach.  It also carries the risk of palatal fistulization, and
interference with normal palatal growth.
     One of the major sequelae is the potential disruption of
bone growth from the removal of the mid-palatal suture line.
Crossbite occurs in 52% operated on transpalatal compared to a
control group.  No data is available on the incidence of
crossbite with transnasal approach.  This cross bite is
attributed to the removal of the mid-palatal suture, causing a
reduction of transverse palatal growth from the proliferative
suture line but may also be just related to the abnormal facial
growth associated with the other congenital anomalies.

Conclusion:

     Congenital choanal atresia is a uncommon condition.  It is
very important for the Obstetrician and primary care giver to be
familiar with this condition due to the risk of neonate
asphyxiation.  There are many different types of choanal atresia
repair.  The reason is that none of them are entirely dependable.
The supporters of each technique describe an 80% success rate.
Many physicians prefer the transpalatal approach  due to surgical
exposure.  With the introduction of endoscopic sinus surgery many
physicians are very comfortable with endoscopic work and
transnasal will become more popular.
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