TITLE: Congenital Aural Atresia
SOURCE: Grand Rounds Presentation, UTMB, Dept. of Otolaryngology
DATE: October 17, 2007
RESIDENT PHYSICIAN: Hwa J Son, MD
FACULTY PHYSICIAN:
SERIES EDITORS: Francis B. Quinn, Jr., MD
"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 purp=
ose
of stimulating group discussion in a conference setting. No warranties,
either express or implied, are made with respect to its accuracy, completen=
ess,
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 aural atresia (CAA) refers to the abs= ence of external auditory canal. It occurs in 1/10,000-20,000 live births. It is more common in male and occurs more frequently on the right side. It is more commonly unilateral and bony as opposed to cartilaginous.
Embryology:
Embryology explains many associations that occur= with CAA. At around 6-8 gestational week, epithelial core from the first branchi= al groove forms meatal plate. This recanalizes around week 21 and forms extern= al auditory canal. During a similar time period, auricle and middle ear struct= ures form; the first and second branchial arches give rise to auricle between we= ek 8-12 and to middle ear structures around week 5-12. Inner ear structures, on the other hand, develop solely from otic capsule and starts at an earlier d= ate, around week 3. Hence the most commonly associated anomalies to CAA are malleus/incus fusion and microtia. It is notable that the severity of micro= tia dictates the degree of middle ear malformation. Less commonly associated are the malformations of the footplate of the stapes or inner ear structure. Un= like other ossicles, the footplate of the stapes has dual origin from the second branchial arch as well as otic capsule.
Incidence:
CAA is mostly sporadic. Syndromic associations s= uch as Treacher Collins, Goldenhar’s, De Grouchy, branchio-oto-renal, and Crouzon syndrome occur in about 11-47%. It is familial<= /span> in about 4.9-10.3%.
Other non-syndromic associations include facial asymmetry, facial nerve abnormality, cleft lip/palate, urogenital defects, cardiovascular malformation, macrostomia, a= nd congenital cholesteatoma.
Presentation:
Patients usually present as newborns with microt= ia or having failed hearing screen. A careful history should be taken including exposure to teratogens such as thalidomide, isoretinoin, vincristine, cholchicine or cadmium as these could cause microtia. Family history of CAA= or other ear anomalies should be elicited. Hearing status, language developmen= t, history of any ear surgeries as well as frequent ear infections should be asked.
On physical exam, one should look for the locati= on of condyle, size of mastoid, craniofacial anomaly, and severity of microtia. Severity of microtia is graded from I-IV. Grade I is when the auricle is in normal shape but slightly smaller. Grade II still has normal cartilaginous framework, but the size is about half of normal. Grade III is severe microt= ia without normal shape of the auricle. Grade IV is anotia.
Grading:
One can also grade severity of atresia based on =
more
extensive anatomical findings. One such classification is by Schucknecht. G=
rade
A is stenotic ear canal with normal middle ear and inner ear anatomy. Grade=
B
has stenotic ear canal with some degree of middle ear abnormality such as
fusion of malleus and incus. Grade C has complete atresia but relatively
preserved anatomy of middle ear and inner ear. Finally, grade D has both
Hearing:
Audiological assessm= ent should be done when the patient presents at age 2-3 months with auditory brainstem response (ABR). It will typically show a normal bone conduction l= evel but maximal conductive hearing loss with air conduction level near 60 dB. T= his is both due to the absence of canal and impaired mobility of the ossicles. = If ABR shows unilateral hearing loss with normal contralateral hearing, then no intervention is necessary. Behavioral audiogram should be done at age 6 mon= ths to confirm ABR. If ABR shows bilateral hearing loss, then the child should = be fitted for bone conduction hearing aid ideally before the age of 6 months. = They should be enrolled in speech therapy early on.
Imaging and Prognosis:
High resolution CT scan (HRCT) should be obtaine= d at several months. Things to look for include the status of the inner ear, the extent = of temporal bone pneumatization, the course of the facial nerve and the presen= ce of the oval window/stapes footplate. Additionally, one should also assess t= he thickness of the atretic bone, soft tissue contribution to the atresia, siz= e/status of the middle ear cavity, and the presence/absence of congenital cholesteat= oma.
Jahrsdoerfer et al. came up with grading system = of CAA based on CT findings. It gives each anatomical structure such as presence of stapes, oval window, middle ear space, and normal facial nerve either 1 or 2 points, with the presence of stapes footplate being the only one with 2 poi= nts. Out of 10 points, if the patient achieves 8 or 9, that correlates with excellent prognosis when undergoing a reconstructive surgery, likely to ach= ieve post-operative air bone gap of 20-30dB 80% of the time, according to their study. On the other hand, if their score is equal to or less than 6, then t= he patient is a poor candidate for the surgery.
Counselling:
Based on this scheme, one should counsel parents=
of
the patient with CAA about the prognosis of the reconstructive surgery.
Regardless, if the patient has bilateral conductive hearing loss, he or sho=
uld
be started on bone conduction hearing aid (BCHA) right away. Bone conduction
hearing aid uses a headband or glasses and has a sound transducer which
vibrates mastoid bone and stimulates cochlea directly. About 25 years ago,
another kind of bone conduction hearing aid called BAHA or bone anchored
hearing aid was developed in
Hearing Improvement:
There are many studies attesting to the hearing
results in patients using BAHA. Grandstrom et. al in 1993 showed that 39
patients fitted with BAHA for poor Jardoerfer score (6 or less) showed 100%
satisfaction with speech threshold. Hakansson et al published BAHA results =
with
147 patients in
Treatment:
The goal of reconstructive surgery is to create a patent, skin-lined external auditory canal with post operative ABG between 20-30. The hearing result must hold in long te= rm; in pre-lingual and school-aged children, the hearing result must be adequate f= or language development and give maximal education benefit. It should also cre= ate an esthetically pleasing auricle.
Atresiaplasty is a difficult surgery for many re= asons. There are various altered anatomical sites, so that usual surgical landmarks are absent, particularly when anomaly of facial nerve might be present. The= re are other technical difficulties such as placing skin graft and separating ossicles from atretic bone. One needs to be wary of such complications as meatal stenosis and sensorineural hearing loss.
Because CAA is usually present along with microt= ia, one must approach this as a multi-disciplinary and multi-staged procedure. = One approach adopted by Jahrsdoerfer et al is to have auriculoplasty involving cartilage graft harvest, implantation, lobule reshaping and raising of the framework by a reconstructive surgeon in 3 different stages and then procee= ding with atresiaplasty. One can combine formation of tragus with atresiaplsty. = Each stage is separated by minimum of 3 months. The timing of surgery is case dependent, but usually the earliest time one would consider surgery is at a= ge 5-6 for bilateral CAA. At any earlier age, the rib cartilages from which microtia repair will be harvested from are not mature. Also, the patient ha= s to be old enough to be able to participate in post-op care such as dressing changes. Reconstruction of the auricle must precede atresiaplasty since one would need an undisturbed vascular bed for the best possible reconstruction= .
Contrary to other ear surgeries, the better hear= ing ear is operated on first. Atresiaplasty itself has multiple parts, including canaloplasty, tympanoplasty and meatoplasty. One must employ intra-operative facial nerve monitoring because there are facial nerve anomalies such as wh= en its vertical portion makes a more acute angle than usual, thereby re-crossi= ng the middle ear space.
Follow-up Care
Follow-up care is extensive, with meatal sutures coming out at 6 days, packing coming out in 2-3 wks and the first audiogram= at 8 wks. Antibiotic drops should be used for 8-12 wks. The patient must come = back for audiogram and periodic debridement of the new canal every 6-12 months. =
Results of Treatment::
The hearing results of the surgery were looked a= t by several authors. Jardoerfer et al published hearing results in 90 patients = in 1992 they operated on. Out of these, 37 patients had Jahrdoerfer’s gr= ade of 8 or 9 out 10. 78% of these patients had speech reception threshold of 1= 0-25 dB and SRT <10 in 11%. Chandrasekhar in 1995 looked at 95 patients. 60% = of those going through primary surgery achieved air bone gap closure of <30= and whereas 54% of revision surgery patients did. In 1997, Murphy et al publish= ed results showing 33% of those with partial atresia achieving SRT<20 and 1= 5% of those with total atresia. De La Cruz et al published results of 116 operated ears, of whom 58% showed ABG<30 for primary surgery. For long term heari= ng results, De La Cruz et al looked at 90 ears with post-operation follow-up of greater than 6 months. He showed that on average, hearing improved with both pure tone average and air bone gap, but in long-term follow-up, hearing did deteriorate a bit, although not statistically significant. Ossicular chain re-fixation was the most common reason for hearing deterioration after the = surgery. In summary, the success rate of surgery is dependent on the experience and expertise of the surgeon. In addition, what is termed a success in each stu= dy is different. The most commonly used measure is post-op ABG <30, and even that is not good enough for pre-school or school-aged children who need SRT <15 for maximal educational benefit.
Complications:
There are many complications of the surgery. Lateralization of the tympanic membrane occurs in about 22-28% of the time = and up to 12 months after the procedure. Meatal restenosis occurs in 8-12%. Fixation and discontinuity of ossicles happen at 11.5% of the time. Sensorineural hearing loss and facial nerve injury is less common, occurrin= g at 2 and 1% respectively.
Evans et al in 2006 revisited the question of “surgery or implantable hearing aids?” in a paper that compared costs, rate of complication, and hearing results. The paper showed that with atresiaplasty, the hearing gain on average is 17.3dB per ear whereas it is 31.8dB for BAHA. The cost for reconstructive surgery was $51,506 whereas the cost for 1-stage BAHA and 2-stage HAHA respectively were $42,449 and $28,34= 1. This comes out to cost/dB gain of hearing of $2909 for reconstructive surge= ry, $1238 for 1-stage BAHA and $826 for 2-stage BAHA. In addition, they found o= ut that 93% of patients who had the reconstructive surgery needed some form of sound amplification whereas BAHA patients achieved hearing level <15dB.<= /p>
Complications-wise, there were far more serious = and frequent complications such as facial nerve injury, re-stenosis of meatus, and lateralization of TM for the surgery compared to BAHA in which local inflammation/infection of skin (7.5%) and failure to o= sseointegrate (2.5%) were the main risks.
In animal studies, it was shown that binaural neurons develop early on only when there=
are binaural
inputs present. There are reports of children with minimal or unilateral
hearing loss having social and educational impacts without intervention.
Conclusion:
In conclusion, early identification of CAA is im= portant for hearing amplification and special education. Patient classification wit= h audiologic testing and CT images using such system as= Jahrdorefer’s is important for predicting resul= ts of the reconstructive surgery. BCHA should be fitted before age 6M for bilater= al CAA. BAHA affords better hearing results and satisfaction than BCHA for non-surgical candidates. Reconstructive surgery needs a careful planning and timing with multidisciplinary effort. Before offering surgery, parents must understand that that the surgery produces a questionably adequate hearing result for children. BAHA on the other hand produces good hearing results a= nd is more cost effective for hearing gain than the reconstructive surgery. Final= ly, binaural hearing amplification with BAHA is recommended for further gain in speech in noise and localization.
Case Studies:
Case #1
Case #2
RP is a 10 month old boy returning to our pediat= ric ENT clinic for a follow-up after failing initial newborn OAE. He was born w= ith right partial atresia. On physical exam, he had microtia and right side with small, stenotic canal. Left side had a narrowed EAC at the junction of bony= -cartilaginous junction. CT showed bony atresia on right side, making contact with middle = ear ossicles with otherwise normal inner ear and middle ear. Left ear also had stenotic, tortuous canal with additional, second tympanic membrane medially. Patient was developing speech normally. He was referred to audiology for fitting with either BCHA or BAHA for binaural benefit.
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