Aural Atresia Treatment & Management

Alternatives to surgical correction include amplification devices, such as a bone-conducting hearing aid or bone-anchored hearing device/BAHA system (Cochlear Corp., Englewood, CO).^[17] Conventional hearing aids in patients with canal stenosis may also be used if the hearing device is able to provide adequate amplification. Distinction should be made between the Baha system (Cochlear Corp., Englewood, CO), which is the osseointegrated titanium implant and speech processor, and the Baha Softband (Cochlear Corp., Englewood, CO), which is a bone conducting hearing device that is worn on a soft headband around the head. The Baha system is FDA-approved for children 5 and older in the United States. Oticon Medical Corp. (Somerset, NJ) also has a commercially available bone anchored hearing aid called the Ponto.

Experience using the BAHA device is considerable, especially in Europe. Long-term results of the US experience with the BAHA are also favorable.^[18] This device 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.

This type of 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) less than 30 dB are obtainable with the use of these devices. Bilateral BAHA devices have even been used for patients with bilateral atresia.^[19] Bilateral implants may impart better sound localization ability and possibly better hearing in noisy environments, but this has not been demonstrated consistently experimentally. Furthermore, the use of the BAHA device does not preclude future reconstructive surgery. Potential complications of BAHA 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 BAHA implant 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 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.

Surgical repair of CAA is offered if the patient is deemed a good candidate from both the radiological (see Imaging Studies) and audiological examinations. 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 implant, atresia surgery is recommended prior to placement of the Medpor framework.^[9]

Timing of surgery

External ear reconstruction is usually delayed until the child is about 5.5-7 years, with atresia repair 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. The younger child is certainly not bothered psychologically by the ear deformity and is not yet in school where other children could tease him/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.

Surgery in patients with bilateral CAA is performed with the goal to restore useful hearing, unaided or aided. Surgery should 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.

The patient is placed in the supine position with the operated ear turned away. The arm on the same side of the operated ear (split-thickness skin graft donor arm) is tucked loosely so that in the middle of the operation the arm can be removed from under the drapes and placed on an arm board 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 3-6 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.

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.

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.

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.

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.

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). 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.

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.

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.

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.

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 cottonball 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 one 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 one month visit, the patient has no restrictions and may swim, but alcohol eardrops after swimming and once a week are advised.

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.

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 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.^[20]

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 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, and facial nerve injury occurs in 0.1%. 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 drainage.

In a large review of revision atresia surgery operations, meatal stenosis (narrowing of the ear canal) was the most common complication (58% of 107 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.^[21]

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. The 2 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, but excellent hearing outcomes are difficult. Even so, 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.^{[16, 22]}

A recent study has 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.^[16] 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.^[16] The importance of middle ear aeration has been supported by other studies.^[22]

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 natie 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 replacement prosthesis.^[23] Interestingly, other atresia surgeons have not found a difference between reconstruction using the patient's native ossicular chain and an ossicular prosthesis.^{[24, 25]}

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 a 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.^[26] 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.^[27] Revision surgery may not hold up as well long term.^[28]

Surgeons 10-15 years ago counseled patients and families against repair of unilateral atresia, given the mediocre hearing gains and risk of major complications. Since the introduction of HRCT 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,^[29] 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.

Improvement in the ability to treat congenital aural atresia (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 repair remains unclear. 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.^[9]

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.

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.

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.^{[29, 30]}

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.

Preliminary studies (Bradley W Kesser; unpublished data with manuscript in revision) show that children with unilateral aural atresia are less likely than their peers with unilateral sensorineural ("nerve") hearing loss to fail a grade but are more likely to used services such as an FM system or IEP to achieve scholastic success. Time and ongoing analysis with longitudinal studies will determine if atresia surgery is an advantage in the classroom for children with aural atresia.