BILATERAL CONGENITAL AURAL ATRESIA: SURGICAL RECONSTRUCTION VS. BAHA IMPLANTATION

Martin A. Fernandez

Department of Otolaryngology, Clinica de Marly, Bogota DC, Colombia

Introduction

Congenital aural atresia defines a clinical entity involving atresia of the ear canal and abnormalities in the middle ear usually in conjunction with microtia. These ear malformations may occur in isolation or in association with other craniofacial dysplasias. The reported incidence of aural atresia is around 1 in 10.000 and one third of cases are bilateral with a variety of complexity on each side. Surgical reconstruction has been the traditional approach to resolve the conductive hearing loss and the resulting handicap in bilateral cases, being the objective to restore sufficient hearing to avoid the necessity for amplification. Atresia surgery is usually performed after the age of 5 years old.15 In some cases based on CT scan findings, patients are considered no candidates for surgical repair. It is this group of patients for whom the osseointegrated bone-conducting hearing aid is intended.68 Currently the most popular osseointegrated hearing aid is the Bone-Anchored Hearing Aid (BAHA, manufactured by Cochlear Corporation, Molnlycke, Sweden, formerly Entific Corp.).

However, it is generally perceived that this operation is challenging, even for experienced otologic surgeons. Many of them suggest that it is a risky procedure, specially for the facial nerve and the cochlear function with non stable results over the time, even that many authorities have report large series of patients , some included long-term follow-up, suggesting that the BAHA implantation should be considered as the first option for this patients.

The present case revision intents to compare the experience of the author during 10 years performing both types of treatments for bilateral Congenital Aural Atresia.

Methods

Patients

From 1998 through 2008, 65 primary surgeries for congenital ear malformation were performed by the author, but just 34 cases were available for the long term analysis. During 2003 through 2008, the author performed 19 BAHA implantation surgeries for congenital aural atresia patients, 14 of which were available for the analysis. Revision surgeries and unilateral atresias were not included in this series. Cholesteatoma was found in three patients which was an additional reason to perform the surgery. Of the 48 patients comprising in this study 28 were males and 20 females. Mean age at surgery were 11 +/- 3 for the reconstruction group and 12+/-2 for the BAHA group. The side was chosen based on anatomic and radiologic considerations and the better ear was selected for the initial surgical procedure. In the BAHA group the side selection was based on anatomic issues, patients and parents preferences and patient dominance. The reconstruction was done in 18 patients in the left side and in 16 patients in the right side.

Temporal bone CT scans and adequate hearing documentation (complete audiogram and bone conduction auditory brainstem response testing) were performed on all patients for preoperative assessment. Patient selection criteria for surgery included normal sensorineural function bilaterally and a rating of 7 or above in the CT scan according to the Jahrsdoerfer grading system.9 Patient selection criteria included normal sensorineural function bilaterally and at least 4 mm of cortical temporal bone thickness demonstrated in the radiologic evaluation.

The selection of the procedure was based on CT scan findings and patient and parents decision after a very careful consultation and explanation over the pros and cons of each procedure. Diagnoses included bilateral isolated and syndromes atresias. In this context the mean Jahrsdoerfer rate was 7.8+/-1.2 for the reconstruction group and a little lower 7.3+/-1.2 for the BAHA group.

Surgical Procedure

If an auricular reconstruction was done before, a post-auricular incision with preservation of the implanted rib cartilage framework is performed. If not, the skin and soft tissue incisions are decided based in a previous discussion with the plastic surgeon in order to preserve blood supply and minimize scars.

The temporalis fascia and the mastoid bone are exposed with a careful but generous elevation of the soft tissue. An external auditory canal is created in the atretic bone by drilling posterior to the glenoid fossa and inferior to the middle cranial fossa dura according to the anterior surgical approach described previously.1,2,10 However it is very common to combine this approach with the transmastoid approach due to anatomical rea-sons.11 All surrounding bone is removed from the ossicular chain so that it is centered in the new canal. The mobility of the ossicles is assured trying to preserve the malformed but commonly present ossicular chain. A thin fascia graft is placed over the mobilized ossicular chain. The goal is to maintain contact between the graft and the ossicles and prevent the lateralization. Several techniques can be used to prevent this complication: a notch incision in the graft to accommodate the malleus, a sulcus in the anterior canal wall can be drilled or sometimes cement or fibrin glue can be used to fix the graft to the malleus. A meatoplasty is performed with debulking of the subcutaneous tissues and the auricle is returned to its normal position leaving an anterior skin flap reflected over the anterior canal. A split-thickness skin graft is harvested from the upper arm and used to line the bony canal and placed over the fascial graft, then a Rosebud packing of the new external auditory canal is done.12 The pack is removed 3 weeks later as an office procedure in older patients and under general anesthesia in patients younger than 12 at this time a second look of the canal is performed.

The proper technique of osseointegrated prosthesis placement has been described in detail elsewhere.7,13 Briefly, only a single implant in a single stage operation is required to hold a BAHA securely in place. The marking of the implant site is crucial to preserve enough space to the auricular reconstruction or to avoid contact with the rib cartilage framework or the auricular prostheses (usually the post-auricular flap is elevated a little more posterior than the common technique in non malformed ears). Insertion of the implant must be performed with a high torque drill at slow speeds under maximal irrigation. Previously, an anteriorly based skin flap and careful removal of soft tissue is done. This allows the dermal layer to heal directly on the mastoid periosteum, creating a solid, immobile foundation for the implant. After placement of the implant, the flap is sutured and a hole is punched in the skin directly over the implant. The healing cap is placed and a dressing is positioned and secured. Three months later in order to allow for adequate healing and osseointegration, the bone conductor is placed.

Data Collection

For each patient, preoperative air-bone conduction PTA thresholds at 500, 1000 and 2000 Hz was recorded. The preoperative air-bone gap for each patient was measured by subtracting the best preoperative bone-conducting PTA from the best air-conduction PTA. Postoperative air-bone conduction PTA thresholds and postoperative air-bone gap were also measured for each patient in the reconstruction series. The postoperative BAHA aided PTA thresholds were recorded. Hearing improvement was calculated by subtracting the postoperative air thresholds from the preoperative air conduction PTA.14

The postoperative data were taken from the most recent audiogram beyond the first postoperative year and called long-term hearing results (mean follow-up in reconstruction series, 4.4 y, range, 1.0–10 y; mean follow-up in BAHA series, 3.5y, range, 1.0–6 y).

Major complications encountered in all cases were recorded, including facial nerve iatrogenic injury, sensorineural hearing loss or acquired cholesteatoma in the reconstruction group; and meningitis, failure of osseointegration or severe local skin complications in the BAHA group. The number of surgeries per patient was established according to the number of revision surgeries in each case. It was necessary to review 2 BAHA patients due to skin problems; in one of these cases it was impossible to use the implant. The mean number of surgeries per patient in the reconstruction group was 1.9, but it is necessary to stipulate that a second operation under general anesthesia it was implemented for patients under 12 years old three weeks after the primary surgery, even in absence of complication.

Patient satisfaction was measured trough the question to the patient and parents if they would be able to do the same procedure in the contra lateral ear or in another family member? The answer was positive in 29 (85%) of the reconstruction patients and in 13 (93%) of the BAHA patients. Surgeon satisfaction was also taken into account, and this was defined as a long term postoperative air-bone gap less than 30 dB restoring sufficient hearing so amplification is no longer needed. These was accomplished in 24 (71%) of the reconstruction patients and in 13 (93%) of the BAHA cases.

Results

Operative Findings

In all cases, a fused and malformed malleus/incus complex attached to the bony atresia plate was found. There was one case in which the stapes was absent and a rudimentary oval window was identified. Ossicular replacement prosthesis was not used in any case in the primary surgery. In two cases it was impossible to complete the surgery due to the anatomic position of the facial nerve, both cases were syndromes. Cholesteatoma was found in three patients, two of them had widely excavated the bony external canal. In one cholesteatoma case a fistula was present and a subcutaneous abscess was identified in the post auricular region.

Two of the fourteen patients who underwent osseointegrated implantation had adverse tissue reaction. One patient required removal of the implant because of an infection and a skin graft was necessary.

Hearing Results

Preoperative an postoperative long-term (mean follow-up, 4.4 y) hearing results for 34 patients who underwent primary surgery only or primary surgery followed by revision surgery are summarized in Table 1. 71% of the patients in this series achieved and ABG (air-bone gap) of 30 dB or less in the long term (> 1 y). Furthermore, an average long-term improvement in the ear conduction PTA was 24.2 dB.

Preoperative and postoperative long-term (mean follow-up, 3.5 y) hearing results for 14 patients who underwent BAHA implantation are summarized in Table 2. 93% of the patients achieved and ABG of 30 dB or less in the long term. The average long-term improvement in the ear conduction PTA was 30.6 dB.

Complications

In the reconstruction group, no major complications were documented. Neither of these patients had facial nerve problems, significant sensorioneural loss of hearing or acquired cholesteatoma. Among the causes of initial failure were stenosis of the external auditory canal or meatus, fixation of the ossicular chain and later-alization of tympanic membrane; In general, the failure long-term rate was 28%. For the BAHA group, two patients experienced adverse tissue reactions and one patient required removal of the implant because of an infection. The failure rate with BAHA in this series was 7%.

Discussion

In infants with bilateral atresia, early amplification is essential and a bone conduction hearing aid must be fitted as soon as possible. Surgical decision is usually taken after the age of 5 or 6 years. Although some surgeons are reluctant to recommend surgical intervention in unilateral cases, there is no controversy about the early surgical reconstruction or the implantation of a bone-anchored hearing aid in bilateral cases.15 Many otologic surgeons maintain that hearing recovery in atresia surgery is seldom achieved and in good cases the likelihood of maintaining the initial hearing result is poor. In addition, the perceived risks, especially to the facial nerve, are also cited as a deterrent to surgery. Apparently, the advances in imaging methods, microscopes, facial nerve monitoring and surgical technique have no changed this perception.16 Consequently, some authors suggest the titanium anchored bone-conducting hearing aids as the option with more predictable and stable results with less likelihood of complications and a high rate of patient satisfaction.17 The measure of the long-term outcomes with both types or treatments have very important implications for counseling patients about the benefits they would expect, thus enabling the patient and surgeon to make a more informed choice. Outcome measures are also important in patient selection because the BAHA is a relatively expensive device.

Table 1. Atresia surgery patients and hearing results

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Table 2. BAHA patients and hearing results

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The results of these series show good long-term hearing results in both groups of patients with a very low incidence of major complications. The likelihood of achieve a long-term post-operative air-bone gap of 30 or less after, interpreted for the author as a good result, is 71% in the atresia surgery series and 93% in the BAHA group. The atresia surgery group had an average hearing improvement of 24.2 dB. By comparison, patients with BAHA had on average a 30.6 dB hearing improvement.

Although the number of surgeries per patient is clearly higher in the atresia surgery, the advantage of avoid the permanent use of a hearing aid and its implications in terms of cost, batteries replacement, exposition to wet environments and the interference of a metallic implant in subsequent radiologic studies make a very comparable rate of patient satisfaction in the long-term.18

In summary, surgical correction of congenital aural atresia has the potential to significantly improve hearing with low risk to the patient. Osseointegrated bone-anchored hearing aid offer to the otolaryngologist a viable alternative for hearing rehabilitation in patients who are not candidates for surgery or have failed to obtain hearing improvement with the surgical reconstruction.

References

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Address for correspondence: Martin A. Fernandez, clinicadeloido@marly.com.co

Cholesteatoma and Ear Surgery – An Update, pp. 119–123

Edited by Haruo Takahashi

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