Aural Atresia 

Updated: Dec 04, 2020
Author: Bradley W Kesser, MD; Chief Editor: Arlen D Meyers, MD, MBA 

Overview

Practice Essentials

In congenital aural atresia (CAA), the external auditory canal (EAC) and structures in the middle ear fail to develop completely. Embryologic development of the ear canal and middle ear may be arrested at any point in the process. Therefore, the clinician may encounter varying degrees of severity of this malformation. In the severe form of the disorder, no identifiable ear canal exists (complete atresia), and the middle ear and its structures (ossicles, or ear bones) may be absent or show significant underdevelopment. If a semblance of an external auditory meatus (outer opening) is present, the ear canal may end in a shallow blind pouch. In less severe forms of the disorder, the ear canal may be stenotic (narrow) with a pinpoint aperture leading into the medial ear canal and, possibly, a rudimentary tympanic membrane. The tympanic membrane in these ears may or may not be attached to the ear bones (the ossicular chain).

Surgery to repair CAA is one of the most challenging operations the ear specialist faces. The goals of surgery are to provide the patient with a clean, dry, skin-lined external auditory canal with long-term restoration or improvement in hearing.

CAA is commonly accompanied by microtia ("small ear"), or incomplete development of the auricle (pinna), which is also a surgical reconstructive challenge. Microtia is classically graded I, II, and III: I is simply a smaller than normal ear with all of the normal ridges and valleys of the delicate cartilage. II is smaller than normal, with not all of the ridges and valleys of the cartilage developed. Grade III microtia is a "peanut" ear, with a small cartilage or soft tissue remnant.

The ear canal and auricle assume separate developmental and embryologic origins, yet the development of the auricle often mirrors that of the middle ear structures, with a more developed auricle generally being accompanied by a more developed middle ear space and ossicular chain.[1] The evaluation and care of the patient with microtia is another topic entirely and is addressed in a separate section (see the topic Microtia).

An image depicting Grade III microtia with aural atresia can be seen below.

Grade III microtia with complete absence (atresia) Grade III microtia with complete absence (atresia) of the external auditory canal.

Evaluation and management of congenital aural atresia

Our current understanding of the evaluation and management of patients with CAA stems from 3 significant advancements. First, detailed anatomic studies of the temporal bone have improved our knowledge of the sequence of events in the development of the different regions of the ear (ie, external ear, middle ear, and inner ear). Findings from these studies explain why some regions of the ear are more developed than others in patients with CAA and enhance our appreciation of the anatomical variations found in CAA. In general, patients with aural atresia have normal inner ear (cochlear) function because the cochlea and inner ear structures develop from a separate embryological system from the ear canal and middle ear.

The cochlea and balance system (inner ear) develop from the primitive otocyst of neuroectodermal origin, while the ear canal and middle ear develop from the branchial apparatus and set of swellings and grooves on the side of the embryo's head and pouches on the inside. The implication of this difference in embryologic origin between the inner ear (cochlea) and the middle and outer ear is that patients with aural atresia, in general, have normal inner ear function. This can be confirmed by specialized audiometric testing.

Second, high-resolution computed tomography (CT) scanning has allowed the otologist to "see" into the middle and inner ears to understand the internal anatomy. Before CT scanning, plain radiography and tomography were available, and surgeons could only surmise what the anatomy looked like inside without the ability to predict good surgical candidates. High-resolution CT scanning is paramount in the evaluation of patients for ear canal surgery (see below). With recent reports of the long-term effects of even small radiation dosages from CT scans in young children, CT scanning is typically not recommended until the child is being considered for surgery, around age 5-6 years.

Third, individuals such as Jahrsdoerfer, De la Cruz, and Lambert have gained vast experience in managing patients with CAA and have shared their insight into surgical candidacy, surgical technique, hearing restoration, and management of complications.

In CAA, the role of the otologist extends beyond diagnosis and treatment. The otologist must consider the hearing needs, along with the speech and language development, of the child, especially in children with CAA in both (bilateral) ears, and must determine not only the appropriate treatment, but also the timing of that treatment. The otologist must work closely with the facial plastic surgeon to determine the optimal time for microtia and atresia repair.[2] This decision-making process usually occurs in the setting of anxious parents seeking answers as to how this deformity came about, what can be done to restore their child's hearing and appearance, and how soon treatment can be administered.

An important point to remember: While most all patients with grade III microtia are candidates for reconstruction, not all patients with CAA are candidates for surgical correction. Among patients with associated syndromes such as Treacher-Collins or hemifacial microsomia (HFM)/Goldenhar, approximately 50% of patients are not surgical candidates because of the existing anatomy. In patients with isolated unilateral (one-sided) CAA (most patients), approximately 65-75% are surgical candidates.

For surgical candidates with favorable anatomy, the otologist must rely on the skills, techniques, and experience from middle ear and mastoid surgery to optimize the surgical result. Surgical success is based on restoration of useful hearing, long-term stability of hearing, and maintenance of a patent, skin-lined ear canal. Otologists agree that when these goals are achieved, few accomplishments are as gratifying as successfully treating a patient with CAA.

Alternatives to surgical correction include amplification devices, such as a bone-conducting hearing aid worn on a headband or the osseointegrated bone-anchored hearing devices (eg, Ponto System [Oticon Medical, Somerset, NJ; BAHA System [Cochlear Corp., Englewood, CO]).[3, 4] Conventional hearing aids in patients with canal stenosis may also be used if the hearing device is able to provide adequate amplification.

History of the Procedure

Although atresia of the external auditory canal has been recognized for over 70 years, reports of surgical repair of atresia did not surface until the late 1940s and 1950s. Nager advocated tailoring the surgical technique to open the ear canal and restore hearing to the severity of the atresia.[5] For minor malformations (Group I; normal or stenotic canal with hypoplastic middle ear and some malformation of the ossicles), Nager described an endaural approach to widen the stenotic ear canal and address any middle ear abnormalities.

For Group II malformations (fistulous tract or complete atresia of the canal with a bony atretic plate and some degree of malformation of the middle ear structures), Nager recommended opening the mastoid to expose the lateral ossicular mass, freeing the ossicular chain, and using a split-thickness skin graft to the mucoperiosteal membrane on the undersurface of the bony atretic plate.

For more severe malformations (Group III; complete ear canal atresia with nonpneumatized mastoid and middle ear), he advised against surgery, or possibly creating a window into the lateral semicircular canal.[5]

Schuknecht also divided aural atresia patients into 3 groups based on severity and reviewed 3 methods for surgical reconstruction: 1) creating a window into the lateral semicircular canal, 2) canaloplasty, and 3) type III tympanoplasty.[6] In all of these, the mastoid cavity is opened to access the ossicles and middle ear space, leaving the patient at risk for postoperative drainage and other problems associated with a cavity.

Jahrsdoerfer first described the anterior approach, avoiding opening the mastoid air cells, in 1978.[7] This approach, the standard in atresia surgery today, keeps the canal drilling anterior and superior by following the bone separating the ear canal from the brain and the jaw (temporomandibular) joint through the nonpneumatized bone of the atretic plate directly into the epitympanum and middle ear space. The atretic bone is carefully picked away, the ossicles are freed, and temporalis fascia is used as an eardrum graft with preservation of the native ossicular chain. Placement of a split-thickness skin graft and opening the meatus complete the procedure. With a few minor modifications, this technique is used today and continues to deliver significantly improved hearing results without a mastoid cavity and with fewer complications.

Problem

The main anatomic deformity in CAA is failure of the external ear canal to open and complete its development. The severity of the atresia is variable. The anatomy of the ear depends on the point along the embryological pathway where development is arrested. In the most severe form of CAA (ie, when development of the ear is halted very early), the ear canal cannot be identified. Bone fills or blocks the region the ear canal normally occupies, and no external opening (meatus) is present. In mild cases, the ear canal is present, but it is stenotic and markedly narrowed. A rudimentary tympanic membrane may be present, and it may or may not be connected to the ossicular chain.

In rare cases of ear canal stenosis (narrowing), skin that normally lines the ear canal can become trapped and cannot self-clean. This trapped skin causes bony remodeling of the surrounding bone and can cause infection. This trapping of skin is termed cholesteatoma and is a clear indication for surgical intervention to remove and clean out the trapped skin and provide for a safe ear that will not trap skin. Cholesteatoma should be suspected when there is moisture or drainage at the pinpoint opening of a stenotic canal. It is more definitively diagnosed by high-resolution CT scan of the temporal bone. Magnetic resonance imaging (MRI) with a diffusion-weighted imaging (DWI) sequence will confirm the presence of skin in the stenotic canal. Imaging findings include opacification (soft tissue filling) of the canal with bony remodeling of the surrounding bone.

As noted above, the inner ear develops much earlier in the fetus than the ear canal and middle ear. In addition, the inner ear develops from a completely separate structure from the middle and outer ears. As such, most patients with CAA have normal inner ear (cochlear) function. The problem is simply that the sound energy is not being transmitted or conducted to the inner ear. This is called a conductive hearing loss. Ways to improve the transmission of sound to the healthy inner ear include a bone-conducting hearing aid, an osseointegrated bone-conducting device, and surgery to open the ear canal and restore the natural sound-conducting mechanism to the inner ear (atresia repair or atresia surgery).

Epidemiology

Frequency

The incidence of CAA is 1 in 10,000-20,000 live births. Unilateral CAA is more common than bilateral cases with an approximate ratio of 3-4:1. For unknown reasons, right ears are more commonly affected than left ears, and boys more commonly than girls.

Etiology

Factors that cause the developmental sequence of the ear canal and middle ear to cease in CAA are not known. Regions adjacent to the ear canal, including the jaw bone (mandible) and course of the facial nerve (the nerve that moves the muscles of facial expression) may be affected as well. In general, the inner ear (cochlea, hearing nerve, balance system) is not affected because its development is from a completely separate set of structures from the ear canal and middle ear, and the development of the inner ear is complete by the time the ear canal begins to form. In general, the middle ear, ossicles, and the auricle are affected because their development is concurrent with that of the ear canal. Studies have linked mutations in chromosome 18 to some patients with aural atresia and normally developed auricles.[8, 9]

Pathophysiology

Intimate knowledge of the anatomy and development of the ear is essential to understanding the clinical manifestations of CAA. The development of the ear consists of a complex series of events. The inner ear, middle ear space, ossicles, ear canal, and auricle each are derived from the 3 embryonic germ cell layers (ie, ectoderm, mesoderm, endoderm). These structures assume individual paths of growth and maturation.

Embryology of the ear

The ear canal and middle ear develop from the branchial apparatus, a series of ectodermal outpouchings (arches) and indentations (clefts/grooves) on the lateral surface of the embryo that are first clearly seen at 24 days gestation. The formation of the ear canal begins with the invagination of the first branchial groove (ie, primary meatus). This area is located between the first branchial arch rostrally (toward the head) and the second branchial arch caudally (toward the tail).

The branchial groove invaginates and advances medially as an epithelial plate as early as the second month of fetal life. Its ingrowth temporarily meets the lateral growth of the first pharyngeal pouch. The first pharyngeal pouch is derived from endoderm of the foregut (alimentary canal) and subsequently develops into the middle ear cleft and Eustachian tube. The union between the ingrowth of the first branchial groove and first pharyngeal pouch forms the meatal plate, which is the precursor to the tympanic membrane. At 6 months of fetal life, the epithelial plate begins to canalize (open) from a medial to lateral direction (from the inside out) to meet the primary meatus.

At birth, the ear canal comprises the bony tympanic ring medially and a membranous cartilaginous portion laterally. After birth, the bony tympanic ring lengthens and transforms from a ring into a bony cylinder. Thus, the ear canal increases in length and reaches adult proportions by the age of 4-5 years.

In CAA, development of the ear may be interrupted at any point. If the process is halted before canalization of the ear canal, total atresia occurs. If development is halted during canalization, the patency of the external ear canal varies depending on how far canalization has progressed.

Development of the middle ear space and ear bones (ossicles) is closely aligned with the development of the ear canal, from the branchial apparatus. The middle ear space arises from lateral growth of the first pharyngeal pouch. The middle ear eventually envelops the ossicles and incorporates them into the middle ear space. The ossicles are derived from both first and second branchial arches, specifically Meckel and Reichert cartilages, respectively. Arrest in the development of the ear canal affects the middle ear to the extent that the growth and maturation of the middle ear will also be incomplete, and the middle ear space is constricted. The ossicular chain is usually deformed, typically featuring a fused malleus-incus complex, shortened malleus with absent manubrium, and occasionally, hypoplastic stapes suprastructure. The malleus neck may be fused to the bony atretic plate. In cases of complete atresia, the tympanic membrane is absent.

The inner ear begins development as early as the third week of fetal life with the formation of the otic placode, a local thickening of the ectoderm. The otic placode invaginates to form the otic pit. The epithelium of the otic pit fuses to become the otic vesicle, which forms the membranous labyrinth of the inner ear. A series of infoldings of the otic vesicle compartmentalizes the membranous labyrinth into the vestibule, cochlea, and endolymphatic regions. The inner ear completes its development by the 20th week of fetal life, which predates the formation of the ear canal and explains why patients with CAA generally have a cochlea that is functional and able to be stimulated.

CAA commonly coexists with microtia. However, rarely, CAA may occur alone with an auricle that appears healthy. The embryologic precursors of the auricle are the axonal hillocks, a series of ectodermal elevations derived from the first and second branchial arches located along the rostral end of the branchial apparatus. The axonal hillocks fuse with each other around the primitive ear canal. Each of the 6 hillocks is responsible for forming a distinctive part of the auricle. Hillock 1 forms the tragus; hillock 2 forms the crus helicis; hillock 3 forms the helix; hillock 4 forms the antihelix; hillock 5 forms the antitragus; and hillock 6 forms the ear lobule. The auricle assumes adult shape (but not size) by the 20th week of fetal life. Microtia ("small ear") results when the development of these hillocks is arrested. In general, the middle ear is less developed when microtia is severe than when it is not.[1]

Presentation

The patient with CAA may present with unilateral or bilateral atresia. If the deformity is present in both ears, the severity often varies between the ears. Hearing evaluation through auditory-evoked brainstem response (ABR; BAER) testing and hearing rehabilitation, generally with a bone-conducting hearing aid, are critical early in life for normal language development in children with bilateral CAA.

A study by Montino et al found that out of 68 children with CAA, 94.3% had age-adequate feeding abilities, 44.1% had language development delays, and, in patients with bilateral, right, or left CAA, 57.2%, 53.9%, and 53.4%, respectively, had orofacial development delays.[10]

Colman graded the severity of CAA into 3 categories: minor, moderate, and severe. Patients with severe CAA have total canal atresia and usually present with unfavorable middle ear anatomy and temporal bone development for reconstruction. In comparison, patients with moderate CAA have more favorable anatomy (ie, an identifiable ear canal with deformed ossicles and an aerated middle ear space). Most patients with CAA present with this moderate form. In minor cases, the ear canal is present but narrowed, and the middle ear is better developed.

CAA may coexist with syndromes that feature first and second branchial arch deformities (eg, Treacher-Collins syndrome, hemifacial microsomia, Goldenhar syndrome, and other craniofacial abnormalities).

The patient with CAA may present to the otologist in any of the scenarios discussed next.

Detection at birth

If the anatomic abnormality is detected at birth, the otologist examines the newborn and sees the parents in consultation. The parents are usually anxious and eager to have their many questions answered. Reassurance and parent education are critical during this time. Regardless of whether this condition is present in 1 or both ears, cochlear function must be assessed in both ears by means of specialized audiologic testing, such as auditory-evoked brainstem responses (ABR or BAER testing) elicited from both air-conducted and bone-conducted signals. If bilateral CAA and good cochlear function are present, the infant needs amplification with a bone-conducting hearing aid (eg, BAHA Softband) until a decision is made to pursue surgical correction around the age of 5-7.

The decision to amplify, or place a bone-conducting hearing device, on the child with unilateral CAA is one made individually by the family. There are advantages and disadvantages to using a bone conductor as well as not using one. Physicians should never discourage families from trying a bone conductor on their child with unilateral CAA, but families should not be discouraged if their child refuses to wear it. While researchers are discovering some of the more subtle problems associated with unilateral hearing loss, especially in school-age children,[11] these studies have been conducted in children with unilateral sensorineural hearing loss, not conductive hearing loss. A subsequent report showed that none of the children with unilateral CAA who were studied repeated a grade in elementary education but that they did utilize resources such as an individual education program (IEP) and speech therapy to a greater degree.[12] In general, normal hearing in one ear is sufficient hearing to support normal speech and language development.

That said, it is critical in the early years to monitor the hearing in the good ear to ensure that the ear is hearing well. Follow-up ABR testing is recommended every 3-4, then every 6 months in the first 1-2 years of life, followed by behavioral testing every 6 months in the second 2 years of life and, if the hearing is stable, annually thereafter.

Once in the elementary school years, the child should be monitored for academic success. Resources such as an IEP/504 plan, speech therapy, preferential seating in class, and FM systems should be instituted early to set the child up for success in the academic environment.

Detection in the older child just before microtia repair

The otologist may encounter the older child with unilateral CAA before a plastic surgeon repairs microtia. In these patients, coordination of care between the plastic surgeon and otologist is important to delineate a clear surgical plan and schedule to prevent confusion and unrealistic expectations.[2] Using the patient's own rib ("autologous"), the plastic surgeon sculpts an auricle and pockets it under the skin, moves the lobule, elevates the sculpted rib off the skull with a skin graft, and creates a tragus in a multistage (3-4 operations over a one year period) procedure. The otologist opens the new ear canal, frees the ossicular chain so the ear bones can vibrate, constructs a tympanic membrane, lines the ear canal with a skin graft, and opens the meatus in continuity with the new ear canal in a single procedure.

A porous polyethylene implant (Medpor, Su-Por) has recently been established as a viable means of reconstructing the auricle. Long-term (12 years) data show a complication rate of exposure of the implant at 7%.[13] The implant in the setting of atresia can be problematic if the atresia repair is performed after the implant has been placed. In this instance, the implant is at risk for exposure, infection, and extrusion. Patients have undergone atresia repair before Medpor implantation with short-term success.[14] Revision atresia repair in these patients again puts the Medpor implant at risk.

Clinical picture with canal stenosis

A child with canal stenosis (mild atresia) may present to the clinician with or without associated hearing loss in the ear. These patients with narrowed canals (generally less than 2 mm) are at risk for canal cholesteatoma.[15] Cholesteatoma is a pocket or cyst of skin that grows and expands as dead skin cells fill the cyst. Careful observation, follow-up, and microscopic examination and cleaning may ensure that the patient does not develop a canal cholesteatoma. However, when the opening to the ear canal is too small to permit examination or when the patient's history (eg, ear drainage or pain) suggests a cholesteatoma, radiographic imaging with CT scanning is used to evaluate the possibility of a canal cholesteatoma; CT scan image of a patient with canal cholesteatoma is seen below.

Coronal CT scan of patient with ear canal choleste Coronal CT scan of patient with ear canal cholesteatoma (right ear) in the setting of congenital aural stenosis. Note the rounded edges of ear canal bone filled with soft tissue density extending into the middle ear.

Children with canals 2 mm or smaller in diameter develop canal cholesteatoma more frequently than do other children. In addition, canal cholesteatomas are rarely, if ever, observed to occur in children younger than 3 years. Cole and Jahrsdoerfer reported these findings and noted that 50% of 54 stenotic ears with canals smaller than 4 mm developed canal cholesteatoma.[15] Clinicians should readily incorporate CT scanning into their diagnostic workup in children with stenotic ear canals to ensure that no canal cholesteatoma, medial to the stenosis, is present.  CT scanning can be performed when the child is aged 4-5 years and should not be done during infancy. Canal cholesteatoma in the setting of complete aural atresia very rarely, if ever, occurs.

Clinical picture in the adult with CAA

Adults with CAA who present to the otologist usually have a unilateral condition that was not corrected in childhood. In some patients, the condition was unnoticed, especially in those with stenotic ears. If it was noticed, the patients may have been told that their condition was inoperable or too risky to repair in light of possible facial nerve injury. This is especially true if the contralateral ear was morphologically and functionally normal. In this situation, the patient may make an informed decision to proceed with an evaluation for surgery with dedicated CT scan and audiometry with the hopes of obtaining binaural hearing.

Indications

Any child with microtia/atresia and normal bone conduction thresholds (normal inner ear or cochlear function) is a candidate for habilitative resources. These resources may include preferential seating in school, an FM system in which the teacher wears a microphone and the child has a speaker at his or her desk or an ear bud, or a hearing aid. FM systems improve the signal-to-noise ratio for children with hearing loss and can be effective in the classroom setting.

Individualized education programs (IEPs, 504 plans) are also available for children with aural atresia. Speech therapy is also indicated if the expressive language is not progressing.

Amplification options include bone-conducting hearing systems such as the BAHA Softband (Cochlear; Sydney, Australia), a bone oscillator worn on a headband tight to the bone around the head to optimize bone conduction to the cochlea, or, when the child is aged 5 years or older, an osseointegrated bone-conduction hearing device, an implantable titanium post to which the bone oscillator is affixed. Osseointegrated bone-conducting systems in which a post (abutment) comes through the skin (percutaneous) include the BAHA Connect System (Cochlear; Sydney, Australia) and the Ponto System (Oticon Medical; Somerset, NJ). Osseointegrated bone-conducting systems in which a magnet attaches to the titanium implant completely under the skin (transcutaneous) include the BAHA Attract System (Cochlear) and the Sophono system (Sophono; Boulder, CO).

The latter two devices (Sophono and BAHA Attract) require surgical placement of a metallic plate into the bone of the skull behind the ear. Once healed, the sound processor is attached to a magnetic plate that is placed on the skin over the metallic plate. Sound enters the processor, which vibrates, and through the magnetic field, vibrates the underlying magnetic plate and implant plate in the bone, sending the sound energy to the cochlea via bone conduction.

The BAHA System (implanted titanium post) is not approved in the United States for children younger than 5 years. These devices utilize bone conduction, sending the sound energy through the bone of the skull directly to the cochlea and bypassing the outer and middle ear.

Finally, two newer devices place the active vibrational plates under the skin. With the Cochlear Osia System (Cochlear) and the Bonebridge device (Med-El Medical Electronics; Innsbruck, Austria) the patient wears a microphone-transmitter on a magnet that sends the sound signal across the skin to the "actuator," or active piece secured to the bone. Both devices have shown favorable efficacy in hearing habilitation in patients with conductive hearing loss.[16, 17, 18]

Before surgical atresia repair (canal surgery) is considered, the patient must fulfill two criteria. First, the patient with congenital aural atresia (CAA) must have normal cochlear function, as demonstrated on audiologic examination with normal bone conduction thresholds in the atretic ear. Second, CT scanning must demonstrate normal inner ear and internal auditory canal morphology.

If patients meet these criteria, the next step is to identify patients with favorable anatomy who have a reasonable chance of success with surgical correction. Jahrsdoerfer devised a 10-point grading scheme, based on features from the CT scan and appearance of the external ear, that reflects the likelihood of success (see Imaging Studies).[19] Patients who have a score of 7 or higher are good candidates for surgery. Patients must also be motivated to undergo the surgery and postoperative care and must be willing to have the ear cleaned of dead skin once or twice a year for the rest of their lives.

Numerous studies now show that in patients with favorable anatomy, repair of unilateral CAA is a viable and successful undertaking.[20, 21]

Relevant Anatomy

Critical assessment of the anatomy is necessary in the evaluation and treatment of the patient with congenital aural atresia (CAA). Even if surgical correction is not sought, the otologist must understand the patient's anatomy and be able to assess the CT scan to explain the nature of the deformity to the parents or patient. Every CAA patient's anatomy is different.

The relevant anatomy includes the patency (or lack thereof) of the ear canal. In the absence of an ear canal, the atretic plate is the bony region just lateral to the middle ear space. Assessment of the middle ear space should include the appearance of each of the three ossicles and the incudostapedial joint (the joint between the second and third ear bones, the incus and stapes) and the position and course of the facial nerve through all of its segments. The course of the facial nerve is often aberrant in CAA, as the nerve typically courses more anterior and lateral in its proximal mastoid segment just after the second genu. In addition, the second turn takes a more acute bend than normal.

Patency of the round and oval windows must be ensured. The otologist should evaluate the size and pneumatization of the middle ear cavity and mastoid. Size, or volume, of the middle ear space has been shown to correlate with hearing outcomes; ie, the larger the middle ear volume, the better and more stable the hearing results.[22]   Relationship to the jaw joint is also important to determine the amount of room for drilling the ear canal. The position of the tegmen (bone separating the ear from the brain) is important, as the "roof" of the ear may hang down too far inferiorly to open an ear canal.[23] Very low tegmen is seen in the image below. The morphology of the inner ear is also evaluated for concurrent inner ear dysplasia.[24]

Very low tegmen (bone that separates brain from ea Very low tegmen (bone that separates brain from ear) and lack of middle ear aeration make this patient not a candidate for atresia surgery.

Contraindications

An absolute contraindication to surgical correction of congenital aural atresia (CAA) is lack of cochlear function in the involved ear as documented on audiological examination. In this condition, bone conduction thresholds will be in the moderate-severe-profound range. CT scan may reveal a dysplastic or aplastic inner ear (rare). Surgical correction of CAA is pointless if the patient has no cochlear function. However, if microtia is present, reconstruction of the auricle may be undertaken for cosmetic purposes.

Lack of middle ear aeration is another contraindication to surgery. Without an air space, the ossicles cannot vibrate, and the sound conducting mechanism of the middle ear will not be restored.

The tegmen is the bone that separates the brain from the ear. If the tegmen hangs too low, not enough space exists to open an ear canal; brain injury is a risk during the drilling. The patient is not a candidate for atresia surgery (see the image below).

Very low tegmen (bone that separates brain from ea Very low tegmen (bone that separates brain from ear) and lack of middle ear aeration make this patient not a candidate for atresia surgery.

Although some authors have advocated transposition of the facial nerve in some situations, a facial nerve coursing over the oval window or in direct line of canal drilling would be a relative contraindication.[25]

 

Workup

Laboratory Studies

In a healthy patient with no other abnormalities, laboratory investigation is generally not necessary. A small subset of patients with aural atresia will have 18q chromosome deletion syndrome. These children typically have normal auricles with complete atresia of the ear canal. Genetic testing can identify this rare condition.[9, 26]

Imaging Studies

Thin section (≤1-mm sections), high-resolution, axial and coronal computed tomography (CT) of the temporal bone is the study of choice in the surgical workup and evaluation of patients with congenital aural atresia (CAA). Given the radiation exposure of this imaging modality, the CT scan is not recommended until the child is being considered for surgery, around the age of 5-6 years.

  • Perform the study by obtaining contiguous images with a thickness of 1 mm or less (submillimeter thickness) in both axial and coronal planes (coronal reconstruction is adequate with the appropriate software).

  • Imaging provides information on whether surgical repair is feasible based on the anatomy present.

  • Obtain imaging when surgical correction is contemplated or just before surgery.

  • As long as audiologic evidence reveals that the inner ear is functional, imaging is not necessary during early infancy and childhood.

In 1992, Jahrsdoerfer et al developed a 10-point grading system to determine surgical candidacy based on key features from the CT scan and the appearance of the external ear.[19] This scheme is also used to indirectly estimate the likelihood of success if surgical correction is performed.[27]

Jahrsdoerfer recommends operating on unilateral patients with scores of 7 or higher; bilateral patients with a grade 5-6 or higher. This system bases surgical success on a postoperative speech-reception threshold (SRT) of less than or equal to 30 dB HL, which, depending on the anatomy, is attainable in over 80% of patients.[27] As a reflection of the conservative nature of this grading system, a score of 10 is never given.

The following is a summary of this 10-point grading system:

  • Stapes present = 2 points

  • Oval window open = 1 point

  • Middle ear space = 1 point

  • Facial nerve = 1 point

  • Malleus-incus complex = 1 point

  • Mastoid pneumatization = 1 point

  • Incus-stapes connection = 1 point

  • Round window = 1 point

  • External ear appearance = 1 point

Each ear is given a grade based on the CT-scan anatomy and this scale. The anatomy predicts the candidacy of that ear for atresia surgery. Of patients with scores of 7 or greater, 80-90% have been shown to achieve normal or near-normal hearing (≤30 dB HL speech reception threshold), whereas only 40-45% of patients with a score below 7 will achieve a good hearing result.[27]

Other Tests

Audiometry is equally as important as imaging in the evaluation of the patient with CAA. Air and bone conduction pure-tone thresholds at 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, 6000 Hz, and 8000 Hz, speech reception thresholds, and speech discrimination scores comprise the routine audiological assessment. Air conduction thresholds in the atretic ear tend to run in the 60-70 dB HL range with similar speech reception thresholds. Bone conduction thresholds in the atretic ear are typically in the normal range (and if they are not, the patient may not be a candidate for surgery), with excellent speech discrimination scores.

The masking dilemma arises when testing the patient with bilateral CAA. How does the audiologist establish bone conduction thresholds for each ear in bilateral CAA? The sensorineural acuity level test (SAL) allows the establishment of individual bone conduction thresholds in bilateral CAA, as follows:

  • Determine patient's thresholds through earphones to 500, 1000, 2000, and 4000 Hz.

  • Place a bone oscillator on the forehead and present masking through it at the following intensities:

    • 500 Hz - 50 dB HL

    • 1000 Hz - 50 dB HL

    • 2000 Hz - 60 dB HL

    • 4000 Hz - 60 dB HL

  • With masking present, reestablish air conduction thresholds.

  • At each frequency, determine the difference between the masked air conduction threshold and the unmasked air conduction threshold

  • Norms of threshold shift with bone conduction masking are as follows:

    • 500 Hz - 40 dB HL

    • 1000 Hz - 50 dB HL

    • 2000 Hz - 45 dB HL

    • 4000 Hz - 50 dB HL

If the masked threshold shifts more than the norm, the bone conduction threshold is 0 dB HL. If the masked threshold shifts less than the norm, then the bone conduction threshold is the difference between the norm and the amount of shift (eg, if the norm is 50 and the amount of shift is 30, the masked bone conduction is 20).

Diagnostic Procedures

See discussion of audiology and CT temporal bone imaging above.

 

Treatment

Medical Therapy

Alternatives to surgical correction include amplification devices, such as a bone-conducting hearing aid on a soft or hard band worn around the head, or a conventional hearing aid if the auricle development supports placement of a device that is able to provide adequate amplification. The Adhear System (Med-El Medical Electronics) includes an adhesive worn behind the ear to which the speech processor attaches. This device is an alternative to the headband as it does not go around the head.[28]  As noted, the bone conductor is strongly recommended for children with bilateral CAA. The benefits of a bone conductor in children with unilateral CAA are unclear and the topic of active research.

Both the osseointegrated bone-conduction systems (Ponto, BAHA Connect, BAHA Attract) and the active middle ear bone conduction systems (Bonebridge, Cochlear Osia) involve surgery to place the osseointegrated titanium implant or middle ear actuator. The osseointegrated systems are FDA-approved for children aged 5 years or older in the United States. The active middle ear implants are approved for children aged 12 years or over (Cochlear Osia, Bonebridge).

Experience using osseointegrated bone-conducting devices is considerable, especially in Europe. Long-term results of the US experience with osseointegrated bone-conducting devices are also favorable.[29] These devices features a surgically implanted, percutaneous titanium fixture-abutment that osseointegrates into the temporal bone. A sound transducer attaches to this titanium implant and delivers the sound energy directly to the cochlea via bone conduction. Therefore, one does not need an ear canal or middle ear to hear.[30]

This type of osseointegrated technology is more efficient than the bone-conducting hearing aids because the sound energy is not attenuated by the skin and intervening soft tissues. Speech reception thresholds (SRTs) of less than 30 dB are obtainable with the use of these devices. Bilateral osseointegrated bone-conducting devices have even been used for patients with bilateral atresia.[31] Bilateral implants may impart better sound localization ability and possibly better hearing in noisy environments, but experimentally, this has not been consistently demonstrated. The use of an osseointegrated bone-conducting device does not preclude future reconstructive surgery. Potential complications of placement include failure of osseointegration, with extrusion of the fixture/abutment; skin overgrowth over the abutment; and flap necrosis with secondary healing.

Important: When implanting the osseointegrated bone-conducting device in a patient who has not had microtia repair, it is critically important to place the implant far enough away from the virginal skin and soft tissue in the postauricular area so that the reconstructive microtia surgeon has room to place the autologous rib cartilage graft or porous polyethylene implant without scarring.

These alternatives may be considered in patients with unilateral or bilateral congenital aural atresia (CAA) who do not desire surgical correction or in whom the existing anatomy is not favorable (a score of 6 or less on the Jahrsdoerfer CT grading scale) but the cochlea is still functional and can be stimulated.

Some audiologists have also tried conventional hearing amplification in patients with canal stenosis. The amplification provided may overcome a mild-moderate conductive hearing loss associated with canal stenosis or minor middle ear malformation.

A study by Attaway et al indicated that in children with aural atresia who are provided with an amplification aid, the development of speech and language abilities are influenced by the age of first amplification, the degree of compliance in aid use, and which ear has atresia. For example, children fitted with the aid before age 1 year and those with left-sided atresia demonstrated better results.[32]

Surgical Therapy

Surgical repair of CAA is offered if the patient is deemed a good candidate from both the radiological (see Imaging Studies) and audiological evaluations. Patients with unilateral atresia are offered surgery if the anatomy is favorable. Surgery to correct CAA is usually performed after the child undergoes the multistage autologous rib graft reconstructive surgery for microtia (usually around 5.5-7 y). This surgery is typically performed after the cartilaginous auricular framework is placed and the ear lobule is created. Surgery is not typically recommended until the child is old enough and mature enough to cooperate in the office for the critical postoperative care, including packing removal and ear canal debridement (usually at 5.5 y). For families choosing the Medpor or Su-Por implant, atresia surgery is recommended prior to placement of the polyethylene framework.[14]

Timing of surgery

External ear reconstruction is usually delayed until the child is about 5.5-7 years, with atresia repair either preceding the Medpor/Su-Por microtia repair or following the series of operations required for rib graft microtia repair. This delay allows for growth of the rib cage, enabling sufficient costal cartilage to be harvested for sculpting the auricle. A child who is large for his/her age may be operated on earlier. The atresia surgery is typically performed after the cartilaginous auricular framework is placed, the ear lobule created, and the sculpted auricle elevated off the skull with a skin graft.

For the child with Grade I or II microtia that does not require reconstructive surgery, atresia surgery can be performed at the age of five if the child is cooperative. Waiting until the child is 6 or 7 allows the child to achieve a level of maturity and cooperation absolutely critical for the postoperative dressing changes, packing removal, and ear canal cleaning to ensure a good result. A potentially poor result can be salvaged postoperatively in the office but requires the cooperation of the patient.

Although reconstructive surgeons using the Medpor implant have implanted children as young as 3 years, the authors do not advocate atresia repair at that age because, in this author's experience, the child is simply too young to cooperate with the necessary postoperative packing removal and ear canal debridement. In addition, younger children may have a higher rate of meatal or canal stenosis necessitating revision surgery. Finally, younger children have a higher incidence of Eustachian tube dysfunction and middle ear fluid. Waiting until the child is older allows the Eustachian tube to mature and aerate or ventilate the middle ear space more effectively so that the middle ear stays clear of fluid, inflammation, and infection. The younger child is certainly not bothered psychologically by the ear deformity and is not yet in school where other children could tease him or her.

Corrective surgery may also be delayed until adulthood, when the patient can make an informed decision. The benefits of binaural hearing and improved sound localization must be weighed against the potential complications of surgery, including canal stenosis and new bone growth seen in younger patients. Research is ongoing regarding the optimal timing of atresia surgery and whether the child or adult can "use" their new ear in tests of binaural (use of both ears in a coordinated fashion) hearing - hearing in background noise and sound localization.

Surgery in patients with bilateral CAA is performed with the goal to restore useful hearing, unaided or aided. Surgery can take place just before the child enters school, usually when aged 5-6 years. Unlike classical otologic surgery, the better ear (anatomically) is chosen for surgery to repair CAA.

Preoperative Details

The patient is placed in the supine position with the operated ear turned away. The arm or leg on the same side of the operated ear (split-thickness skin graft donor limb) is tucked loosely so that in the middle of the operation the arm or leg can be removed from under the drapes and placed on an arm board (or accessed if the leg) for skin grafting. No blood pressure cuff is placed on the donor arm. A half inch swath of hair is shaved around the ear. The postauricular area is injected with 1% lidocaine with 1:40,000 epinephrine. The ear is prepped and draped in standard fashion.

Although the surgery takes 3-5 hours, urethral catheterization is not used; the anesthesiologist adjusts fluid volume accordingly. A short-acting paralytic may be used for induction of anesthesia and intubation, but no paralytic may be administered during the operation as facial nerve monitoring is performed for all atresia operations. The anesthesiologist is requested not to use nitrous oxide, as this gas diffuses into the middle ear and can cause increased positive pressure, ballooning the fascia graft away from the ossicles. The patient is kept overnight in the hospital.

Intraoperative Details

Incision and drilling

A postauricular incision is made and carried down to the temporalis fascia. A quarter-sized piece of fascia is harvested, scraped, and placed on the back table to dehydrate. Mastoid periosteal incisions are made along the linea temporalis and perpendicular anteriorly, along the temporomandibular joint (TMJ), down toward the mastoid tip. This anterior mastoid incision allows a cuff of periosteum to remain at the TMJ to which a tragal skin flap will be sutured at the end of the case to create the anterior canal wall. The mastoid periosteum is elevated and retracted posteriorly; the auricle is retracted anteriorly.

Elevation of the mastoid periosteum proceeds farther anteriorly to identify the glenoid fossa. It is critical to identify the TMJ because this structure serves an important landmark for drilling. Occasionally, a dimple on the surface of the mastoid cortex can be used to identify the site of drilling; alternatively, the cribriform area is usually present as a reliable surface landmark.

Intraoperative image of the bony landmarks used to Intraoperative image of the bony landmarks used to identify the site for drilling the bony canal in a right ear - zygomatic root, glenoid fossa, mastoid tip. Patient in the surgical position.

Using the cribriform area, temporal line, and the glenoid fossa as surface landmarks, drilling is begun with a #5 cutting burr with continuous suction irrigation, with care taken to stay anterior and superior. The tegmen is identified superiorly and followed medially. This superoanterior approach should hug the tegmen superiorly and the glenoid fossa anteriorly. Care is taken to stay out of the mastoid antrum and to open as few mastoid air cells as possible to prevent a large cavity and the risk of postoperative infection or mucosalization of the skin graft. As the drilling proceeds medially, dense, nonpneumatized atretic bone is encountered. This bone is carefully drilled away with progressively smaller diamond drill burrs. As the dissection stays superior, the goal is to enter the middle ear cleft in the epitympanum, superior to the ossicles. This approach also avoids an aberrant facial nerve.

At a depth of about 1.5 cm, the air space of the middle ear is encountered, and the fused malleus-incus complex can be identified. The first landmark the surgeon encounters is usually the body of the incus; this can be confirmed by gentle palpation to assess mobility. The ossicular chain is typically fixed to the atretic plate medially and inferiorly at the level of the malleus neck. With a bit more bone removal, the "buttock sign" is identified—the fused head of the malleus and body of the incus.

Intraoperative image of a left ear in the surgical Intraoperative image of a left ear in the surgical position upon entering the middle ear in the epitympanum. The fused malleus-incus complex can be seen.

Drilling is continued over the atretic plate, with 3 and 2 mm diamond drill burrs with slow rotation, until the bone is an eggshell thickness. The atretic bone overlying the middle ear and ossicles is carefully picked away with a Rosen needle or dental excavator. Sharp dissection is often needed to lyse the periosteal attachments of the malleus to the underside of the atretic plate. A band of soft tissue, mostly periosteum, may course through a bony defect in the wall separating the atretic plate from the TMJ; this band may be confused with the facial nerve.

The facial nerve is most likely encountered while drilling posteriorly and inferiorly. In approximately 25% of cases, the facial nerve has a short vertical segment. Instead, the nerve makes a sharp curve anteriorly at the second genu. The facial nerve is most vulnerable to injury in this location. Thin blood vessels coursing over the surface of the nerve seen through the thinned bone are a good clue to the location of the nerve. As mentioned, facial nerve monitoring is a necessity.

Intraoperative image of a right ear with a lateral Intraoperative image of a right ear with a lateral facial nerve identified in the mastoid segment.

Once the atretic plate is removed, the ossicles are carefully assessed. Bone is removed 360° around the ossicular chain to maximize mobility. The incus and malleus are almost always fused, although some early demarcation of an incudomalleal joint may be present. The handle of the malleus is often absent, and the neck of the malleus is usually in firm bony union with the undersurface of the atretic plate. Care must be exercised in removing the overlying fragments of bone so as not to sublux the ossicles or impart vibratory trauma to the inner ear. Bone around the fossa incudis is kept intact, and the anterior soft tissue attachments between the malleus and anterior mesotympanic bone are also maintained to lend support to the ossicular chain. The last ligamentous attachment of the malleus to the atretic bone is incised with a #59 beaver blade. An image depicting a newly drilled ear canal, middle ear space, and ossicular chain is seen below.

Intraoperative photograph of a newly drilled ear c Intraoperative photograph of a newly drilled ear canal, middle ear space, and ossicular chain in a patient with congenital aural atresia (CAA).

The shape and direction of the incus long arm are highly variable. What is important is that the incus attaches to a stapes. The stapes superstructure may also be anomalous. In more extreme malformations, the superstructure may be monopedal with no connection to the incus. The mobility of the footplate must be determined. Congenital fixation of the stapes is found in 4% of cases. Finding a reasonably well-formed stapes with a mobile footplate in patients with congenital atresia is common. The oval window, in concert with the stapes footplate, may be smaller than normal, but this does not adversely affect either the reconstruction or the postoperative hearing result.

In cases of incudostapedial joint discontinuity, we prefer to remove the lateral ossicular mass and reconstruct with a notched partial ossicular replacement prosthesis (PORP).[33] We have found this reconstruction to deliver superior hearing results compared with any other configuration.

Fascia grafting

The best possible circumstance in which to find the ossicles is for them to be intact (although malformed) and to move as a unit. In this condition, the fascia graft may be placed directly on the ossicular mass. Bone must be drilled peripherally, away from the ossicular mass, to create as much room as possible for the fascia graft. The ossicular mass should be centered with regard to the new tympanic membrane. The new eardrum is about 1-1.5 times the diameter of a normal tympanic membrane.

Intraoperative image of the right ear with the fas Intraoperative image of the right ear with the fascia graft draped over the ossicular chain

Prior to placing the fascia, the anesthesiologist is instructed to lower the expired oxygen to less than 25%. Room air fraction of inspired oxygen (FIO2) is best. Lowering the expired oxygen (by lowering the inspired oxygen) reduces the ballooning of the graft. The fascia is trimmed to size (about 1.5 cm in diameter) and placed in an overlay fashion directly onto the ossicular mass. The edges of the fascia are reflected up onto the canal wall by about 2mm in all directions. If large air cells have been opened, pieces of temporalis muscle are used to plug the defect.

Skin grafting

A split-thickness skin graft using the 2-inch dermatome blade and measuring 0.005 to 0.006 inches is harvested from the medial aspect of the ipsilateral upper arm. If the graft is any thicker, the skin graft tends to curl; buried squamous epithelium could produce a canal cholesteatoma. Too thin, and the graft does not withstand environmental pressures (eg, water) and can slough.

When the skin graft is harvested, an uneven thickness to its parallel borders is frequently noted. In this case, the thinner border is used at the level of the eardrum, and the thicker border is sutured to the new meatus. The skin graft is cut to a size of 3 x 5 cm and notched at the medial edge. The graft is carefully placed down into the canal, and the notched edges are aligned over the temporalis fascia so that the entire fascia graft is covered by squamous epithelium. The vertical slit faces anteriorly; this placement ensures that free edges will not grow into the mastoid air cells.

Intraoperative image of a right ear with the skin Intraoperative image of a right ear with the skin graft placed in position

The key to a successful hearing result is a thin tympanic membrane. A piece of Silastic that is 0.04 inches is cut into a circle and placed over the new tympanic membrane to hold the notched skin edges in place and prevent blunting. The Silastic button also gives the surgeon something to pack against and helps prevent displacement of the skin graft.

Four to five Merocel (Medtronic Corp., Jacksonville, FL) wicks are trimmed to 0.75 inch length and placed down into the ear canal onto the Silastic button. The new ear canal is packed to the level of the bony opening. The wicks are hydrated with an ototopical antibiotic solution (ofloxacin). The lateral skin graft is then folded over the hydrated wicks as the wicks hold the medial skin graft against the bony canal from which it will take its blood supply.

Meatoplasty

A hastily performed meatoplasty can ruin an otherwise flawless operation because it will result in meatal stenosis. Even a carefully constructed meatus can stenose, but if crafted with care, the risk is lower. The first priority is to ensure that the meatus and auricle align with the bony canal. The bony canal cannot move; the auricle needs repositioning to align the meatus to the bony canal in about half of cases, usually in a posterosuperior orientation. The ear can be elevated superiorly by sharply releasing the skin and subcutaneous tissue over the parotid fascia anteriorly and over the sternocleidomastoid muscle inferiorly. Care must be taken to stay superficial and not enter the substance of the parotid gland, as a salivary fistula can be created. The auricle can be moved posteriorly by excising a strip of skin from the postauricular incision and suturing the auricle to the new postauricular skin edge.

A U-shaped skin flap based anteriorly at the tragus is created by making a crescentic incision in the skin of the reconstructed auricle’s conchal bowl. The skin is sharply elevated off the underlying cartilage and is hinged at the tragus. The skin flap is thinned and reflected anteriorly, and the underlying cartilage and soft tissue are cored out with a #11 blade. The skin flap is then brought through the new meatus medially and down to the cuff of TMJ periosteum that was created at the beginning of the operation with the mastoid periosteal incisions.

Intraoperative image of a right ear meatoplasty. Intraoperative image of a right ear meatoplasty.

The tragal skin flap is sutured to this cuff of tissue to create the lateral anterior canal wall. The postauricular incision is tacked down with interrupted 3-0 undyed Vicryl sutures, and the skin graft is delivered through the meatus and sutured to the patient’s native skin at the edge of the conchal bowl with interrupted 4-0 undyed Vicryl and 5-0 fast absorbing gut suture. The lateral canal is packed with full length Merocel wicks hydrated with ofloxacin solution. After closure of the postauricular incision, a mastoid dressing is applied.

Postoperative Details

The patient is admitted overnight and discharged on oral antibiotics (cephalexin) and pain medicine on the first postoperative day after the dressings are removed. Antibiotic ointment is placed over the postauricular incision and an antibiotic-soaked cotton ball is changed at the meatus daily. The patient is seen in the office 1 week after surgery, and all sutures and packing are removed. A corticosteroid antibiotic eardrop preparation is then used twice daily for one week with strict dry ear precautions. The canal is left open to the air.

A second postoperative visit is made 1 month later, and the canal is débrided of desquamated epithelium sloughed from the skin graft. Beneath the epithelial crust, the skin graft should be dry and healthy. The first postoperative audiogram is obtained at this visit.

Following the patient every 6-12 months indefinitely for debridement of the desquamated epithelial crust is important. Although the skin graft is healthy, it is not self-cleaning. Failure to have the ear cleaned routinely may result in decreased hearing and chronic infection. After the 1-month visit, the patient has no restrictions and may swim, but alcohol eardrops after swimming and once a week are advised.

Follow-up

Surgical success is based on restoration and stabilization of hearing and maintenance of a patent ear canal. The first audiometric examination is performed after debriding the ear canal at the one month postoperative visit.

As mentioned, the ear canal will need routine cleaning and debridement once or twice a year for the rest of the patient's life. The debridement simply involves elevating the dead skin that accumulates on the skin graft and removing it. Often, the dead skin reduces the efficiency of the vibration of the new eardrum, and patients can tell that their hearing is a bit muffled. Removal of this dead skin layer restores the clarity of the hearing in the ear as the dead skin peels off the tympanic membrane.

Over-the-counter alcohol-based eardrops (eg, SwimEar drops) are used weekly and after swimming to dry the canal and prevent moisture buildup.

Complications

Injury to the facial nerve is one of the most feared complications of surgery for correction of congenital aural atresia (CAA). This complication has historically deterred surgeons from correcting this condition. However, in experienced hands and with improved imaging techniques, the complication rate has been below 0.1%.

The facial nerve is estimated to be aberrant in 25-30% of patients. In a review of facial nerve injuries in more than 1000 patients with CAA, Jahrsdoerfer and Lambert (1998) reported injury in 10 patients. Patients with low-set ears, canal stenosis, and cholesteatoma had facial nerves vulnerable to injury during surgery.[34]

Complications of atresia surgery can be minimized with proper selection of patients and with careful attention to surgical detail. Most common complications include meatal or canal stenosis in 15-20%, usually requiring revision surgery, and chronic drainage/infection in 10%, usually due to sloughing of the skin graft with "mucosalization" of the canal, which requires revision with a new skin graft or possible temporizing measures such as cauterization or Gentian violet if the area is small.

Less commonly, sensorineural hearing loss (5%) is most likely related to the high energy of the drill on the ossicular chain being conducted to the cochlea. About 15-20% of patients also lose the initial gains in hearing, due either to lateralization of the tympanic membrane or refixation of the ossicular chain. Approximately 15-20% of patients require a revision procedure at some point in the future, usually due to stenosis of the canal, loss of early hearing gains, or sloughing of the skin graft with chronic moisture in the canal.

In a large review of revision atresia surgery operations, meatal stenosis (narrowing of the ear canal) was the most common complication (58% of 107 revision operations), followed by conductive hearing loss and chronic moisture/infection (19-20%). Improvement in hearing, reopening of the canal, and resolution of the drainage were possible in these patients.[35]

Outcome and Prognosis

The goal of congenital aural atresia (CAA) surgery is to restore hearing to a speech-reception threshold (SRT) of less than or equal to 30 dB HL without the need for amplification and to give the patient a clean, dry, skin-lined ear canal and eardrum.[36]

Hearing outcomes after atresia surgery can vary widely. A literature review by Nadaraja et al indicated that atresia repair will lead to normal or near-normal hearing in 50-80% of patients.[37]

The two most important factors in achieving consistently good hearing outcomes in atresia surgery are careful preoperative selection of patients and meticulous surgical technique at each step of the operation. Surgery is not recommended for patients with unilateral atresia and Jahrsdoerfer scores of 6 or below.

Surgery is attempted on the patient with bilateral atresia and a score of 5 or 6. Although excellent hearing outcomes are difficult, the patient may be able to wear a conventional hearing aid in the new canal to bring the hearing thresholds into the normal range. Surgery is not recommended for patients with 4 or below. The most important anatomic feature for successful surgery is middle ear aeration; without an aerated middle ear space, the patient is not considered a candidate for surgery.[27, 38, 39, 40]

A retrospective study by Ahn et al of patients with CAA who underwent canaloplasty with implantation of a partial ossicular replacement prosthesis (PORP) indicated that the length of the prosthesis is significantly associated with the procedure’s long-term effectiveness. At 2-year follow-up, it was found that the mean length of the prosthesis in patients with a successful surgical outcome was 2.30 mm, compared with 2.77 mm in patients with an unsuccessful outcome.[41]

A study by Shonka et al examined the predictive ability of the Jahrsdoerfer scale for hearing outcomes. In this series of 116 patients, patients with a score greater than 7 had an 85-90% chance of achieving normal or near-normal hearing (as defined by an SRT ≤ 30 dB HL) in the short-term; patients with lower Jahrsdoerfer scores had a 45-50% chance of achieving this result.[27] In this same study, aeration of the middle ear was the single best predictor of hearing success in atresia surgery; without an aerated middle ear space, or with a poorly aerated middle ear space, hearing outcomes were not good.[27] The importance of middle ear aeration has been supported by other studies.[38]

A retrospective study by Sakamato et al indicated that in patients with CAA undergoing canal tympanoplasty, an external auditory canal area of over 72.3 mm2 is the most important predictor of a long-term favorable outcome. The study, which involved 51 ears, also found that a mesotympanic depth of over 5.5 mm, a mesotympanic height of over 4.6 mm, and an external auditory canal diameter of over 9.5 mm are also significant predictive factors for such outcomes.[42]

Some patients with atresia may require reconstruction of the ear bones with an artificial ear bone, or prosthesis. This type of reconstruction tends not to be as reliable as using the patient's own intact native ossicular chain. Anatomy of the middle ear and ossicles occasionally dictates (approximately 8-10% of the time) that a prosthesis must be used. This same study argued that a partial replacement prosthesis is superior to a total ossicular replacement prosthesis.[43] Interestingly, other atresia surgeons have not found a difference between reconstruction using the patient's native ossicular chain and an ossicular prosthesis.[44, 45]

One criticism of atresia surgery case series has been lack of long-term follow-up. Lambert examined the stability of hearing results after atresia surgery and found that almost two thirds of patients maintained an SRT less than or equal to 30 dB HL for the longer follow-up (>1 year; mean, 2.8 years); about one third required a revision procedure.[46] Similarly, De la Cruz reported a long-term (≥ 6 months) air-bone gap (ABG) of 30 dB or less in 51% of primary cases and 39% of revisions.[47] Revision surgery may not hold up as well long term.[48]

A retrospective study by Imbery et al found that in children and adults who underwent primary CAA repair, hearing, as measured by a three-tone (500, 1000, 2000 Hz) air conduction pure-tone average (AC PTA), improved by an average of 30.5 dB, with this gain then declining by 8.2 dB over a mean 4.4-year follow-up. The investigators noted that in 64% of the patients, hearing loss was less than 10 dB, while 36% experienced a loss of 10 dB or more over the long-term (>1 year).[49]

Until several years ago, surgeons counseled patients and families against repair of unilateral atresia, given the mediocre hearing gains and risk of major complications. Since the introduction of high-resolution CT scanning with improved preoperative evaluation, the repair of unilateral atresia has become more widely accepted. Clearly, a learning curve exists for this challenging operation, and one report suggests a minimum of 32 ears to achieve proficiency in achieving good short-term hearing results, and 48 ears for good long-term hearing outcomes. The anterior surgical approach as first proposed by Jahrsdoerfer has withstood the test of time and scrutiny. As the seemingly subtle deficits of unilateral hearing loss in children are further elucidated,[50] some habilitative intervention for children with atresia will be more often recommended. Atresia surgery is one of the many options families face when setting their children up for success in the home and in the classroom.

Future and Controversies

Atresia surgery versus BAHAs

When comparing the two modalities of hearing habilitation in patients with aural atresia, the bone-anchored hearing aid (BAHA) clearly affords greater consistency in hearing improvement than does the atresia operation.[37, 51, 52] The greater consistency comes at the price of potentially poorer cosmesis and wound-healing problems. The newer BAHA Attract, Sophono, Bonebridge, and Osia devices obviate the wound healing issues of the BAHA System and Ponto titanium post by placing the metallic plate/actuator under the skin in the bone. Some sound conduction energy is lost/attenuated through the skin and soft tissue with these devices, and the sound amplification and clarity may not be as great.

In children with unilateral congenital aural atresia (CAA), the issue of atresia versus BAHA really seeks to answer the question, "What modality best improves a patient's binaural hearing? Tasks of binaural hearing include sound localization and hearing in background noise. After atresia surgery, children with unilateral CAA do hear better in background noise.[53, 54] Future research and testing must address sound localization and long-term improvements and stability of results.

Similar studies in patients with BAHA devices are confounded by a low number of study subjects and lack of long-term data. Future studies will focus on these tasks of binaural hearing and their improvement over the long term.

Surgery

Improvement in the ability to treat CAA lies with ways to maintain patency of the surgically reconstructed ear canal. This improvement may come in the form of genetically engineered tissue grafts or advanced stent materials.

The role of Medpor microtia repair in the setting of aural atresia appears now to be a viable, established option. Surgeons have attempted atresia repair before the Medpor implant is placed to reduce the risks of implant exposure and extrusion, but no long-term studies have examined these patients' outcomes.[14]

Future research will be aimed at further refining the selection criteria for CAA surgery—variables under investigation include quantifying middle ear volume and other anatomic features on the Jahrsdoerfer grading scale, the angle of the incudostapedial joint, and surface area of the malleus-incus complex upon which the eardrum fascia graft is placed. Refinement of these selection will enable practitioners to predict with greater accuracy hearing outcomes after surgery.

Is there an age that is too young to repair CAA? Certainly, the child who cannot sit still in the office for the necessary packing removal and ear canal cleaning is not old enough to undergo the surgery, unless the surgeon returns the child to the operating room for packing removal and debridement. In addition, younger children are more susceptible to "ear infections" and middle ear fluid, negating the hearing gains of atresia surgery. Waiting until the child is aged 5-7 years mitigates this potential complication.

The auditory system, unlike the visual system, sends signals from both ears to both sides of the brain. Central auditory pathways cross the midline very early in the auditory pathway so that both sides of the brain receive stimulation from both ears. This means that both sides of the brain are being stimulated by the one good ear in unilateral aural atresia. The argument that the earlier the surgeon opens the atretic ear, the less chance the brain will "close down" (and not be able to respond) to input from the reconstructed ear has yet to be supported. In fact, studies have shown that children with unilateral aural atresia do not have the same grade retention rates as their peers with unilateral sensorineural hearing loss with the same resource utilization.[12]

Even still we are just beginning to understand whether a patient can "use" their new ear. Certainly in some cases yes, but sound localization and some tasks of hearing in noise remain elusive for many postoperative atresia patients, even with excellent hearing outcomes.[50, 55] In general, hearing in noise appears to be improved by atresia surgery.[50]

The difficulty patients have with one good ear and one atretic ear is difficulty hearing in background noise and difficulty locating a sound source. Successful surgery to open the atretic ear canal and restore hearing to the ear may eliminate (or greatly reduce) these 2 problems, whether the patient is 5 or 55! Ongoing research is attempting to quantify and qualify the difficulties children with unilateral hearing loss have, both in school and in their day-to-day activities.

Time and ongoing analysis with longitudinal studies will determine if atresia surgery is an advantage in the classroom for children with aural atresia.

Activity

Once the ear is healed, 1 month after surgery and after the first ear cleaning, the child is cleared for all activity, including getting the ear wet. Over-the-counter rubbing alcohol–based eardrops (eg, SwimEar) are recommended once weekly in the canal as a drying agent for the first year after surgery.

Long-Term Monitoring

The child undergoing CAA repair will need long-term maintenance of the ear canal. Unlike a natural ear canal, which is a self-cleaning system, the reconstructed ear canal contains a skin graft that is not self-cleaning. The child will need to have the ear canal cleaned once or twice a year for the rest of his/her life. The cleaning is not painful and simply involves elevating the dead skin layer off the healthy underlying skin and peeling it away, much like one would peel dead skin after a sunburn. This cannot be done by a pediatrician; it should be performed by an otolaryngologist in the office, under a microscope.

The meatus (opening) should also be monitored for the first year or two after surgery for narrowing, or stenosis. If the parents note meatal stenosis, triamcinolone can be injected into the skin around the meatus, and parents can place a foam earplug coated in a water-soluble lubricant at night before the child goes to bed, removing it in the morning to stent the canal open. Occasionally, revision meatoplasty with a new skin graft is necessary to reopen the soft tissue portion of the outer canal.

During the pubertal or teenage years, some children develop new bone growth in the canal. A small amount of new bone growth is not concerning as long as the ear can be cleaned and the hearing is stable, but some children will have exuberant new bone growth and will require revision surgery to drill the new bone away and place a new skin graft.

As noted above, a subset of patients will lose some hearing over time.[49] While the long-term hearing is never as bad as the preoperative hearing, thresholds can change over time, and the hearing should be monitored. A conventional hearing aid in the newly reconstructed canal can often return thresholds to the normal range.

 

 

Guidelines

Guidelines Summary

International Microtia and Atresia Workgroup

Consensus recommendations on the treatment of total congenital aural atresia (CAA), published in 2019 by the International Microtia and Atresia Workgroup (IMAW), include the following[56] :

  • Bone-conduction technology for children with bilateral aural atresia is very strongly recommended to support speech and language development
  • Evaluation of the temporal bones using careful computed tomography (CT) scanning is recommended, as is precise assessment of the type of hearing loss and of preoperative motivation with the softband
  • To prevent the processor from interfering with microtia reconstruction, a discussion between the otolaryngologist/otologist/pediatric otolaryngologist and microtia surgeon regarding placement of the osseointegrated bone conduction hearing device is strongly recommended
  • It is recommended that children over age 6 years whose hearing and anatomy support surgical reconstruction (ie, those with normal inner ear function and a Jahrsdoerfer score of 7 or higher) undergo atresia surgery with the understanding that revision surgery may be required if the canal and hearing are compromised by new bone growth during puberty
  • It is strongly recommended that atresia repair be performed in combination with or subsequent to autologous rib graft microtia repair and prior to porous polyethylene microtia repair