Surgical Correction of Unilateral Congenital External Auditory Canal Atresia: A Case Report

INTRODUCTION

Congenital external auditory canal atresia (EACA) is a rare anomaly occurring due to incomplete canalization of the first branchial cleft. Its incidence is about 1 in 10,000 to 20,000 live births, out of which 70–90% of cases have unilateral involvement with a right-sided predominance.¹ EACA is often associated with varying degrees of microtia and middle ear anomalies, including malformed ossicles and aberrant facial nerve course.²

The primary clinical manifestation is conductive hearing loss in the affected ear. While bone conduction hearing devices offer a non-surgical option, atresiaplasty remains a definitive surgical treatment in selected patients with favorable anatomy.³ Patient selection is guided by the Jahrsdoerfer scoring system, which evaluates middle ear and cochlear structures on high-resolution computed tomography (HRCT).⁴

This report presents a case of unilateral congenital EACA in a child, managed successfully with atresiaplasty, resulting in significant functional and anatomical improvement.

CASE REPORT

A 10-year-old male presented to the otolaryngology outpatient clinic with complaints of decreased hearing in the right ear since birth. There were no associated symptoms such as ear discharge, ear pain, spinning sensation, ringing in the ear, or speech delay. His academic performance was average, and there was no family history of congenital ear malformations.

On external ear examination, the right external auditory canal was completely blocked with no view of the tympanic membrane [Figure 1]. The left ear canal and tympanic membrane were normal. There were no craniofacial dysmorphisms, and auricular development was Grade II on the right side, according to the Marx classification. Facial nerve function was normal.

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Figure 1: Pre-operative clinical picture of external ear examination showing the atretic right external auditory canal, with no view of the tympanic membrane.

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Pure tone audiometry demonstrated a right-sided moderate to severe conductive hearing loss (average air-bone gap of 53 dB), with normal hearing on the left [Figure 2]. Tympanometry on the left showed a Type A curve. The right ear could not be assessed due to the atresia.

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Figure 2: Pre-operative pure-tone audiogram showing a right-sided moderate to severe conductive hearing loss (average air-bone gap of 53 dB), with normal hearing on the left.

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HRCT of the temporal bone showed total atresia of the right external auditory canal with a thick bone plate [Figure 3]. The middle ear was well pneumatized, with ossicles present but with slight malformation. The facial nerve had a normal course, and the oval and round windows were visible. The inner ear structures were normal bilaterally. The Jahrsdoerfer score was 9/10, making the patient a suitable candidate for atresiaplasty.

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Figure 3: Pre-operative high-resolution computed tomogram of the temporal bone, axial sections showing total atresia of the right external auditory canal with thick bone plate. (a) Axial section at the level of attic showing ossicular chain normal left side and deformed on right side. (b) Axial section at the level of promontory showing reduced middle ear space on right side. (c) Axial section at the level of eustachian tube showing reduced protympanum.

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After thorough counseling, the patient was scheduled for right-sided atresiaplasty under general anesthesia. The mastoid was opened via a postauricular approach using a high-speed otologic drill under microscope illumination and magnification [Figure 4]. After the identification of the antrum and aditus, the atretic bony plate was removed [Figure 5]. The middle ear was accessed, and the malleus and incus were noted to be malformed, but the ossicular chain was mobile.

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Figure 4: Intra-operative microscopic picture showing postauricular incision with ‘triangle of attack’, i.e., Macewen’s triangle for mastoidectomy marked.

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Figure 5: Intra-operative microscopic picture showing the opened-up antrum and aditus with the atretic bony plate lateral to the middle ear with the ‘buttock sign’ of intact ossicles.

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A neocanal with a diameter of more than 10mm was created by careful drilling. The temporalis fascia graft was shaped and placed over the malleus and incus [Figure 6]. A split-thickness skin graft (thickness 0.008-0.011 inches) harvested from the right anterior thigh area was used to line the neocanal. A wide meatoplasty was done, and the skin graft was stitched to its edges. A silastic sheet was placed in the canal to keep the flap in place and prevent restenosis, and the wound was closed in layers. No facial nerve injury or intraoperative complications were noted.

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Figure 6: Intra-operative microscopic picture showing the neocanal and the temporalis fascia graft being placed over the handle of the malleus, to form the neotympanum.

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The patient was monitored postoperatively for pain, infection, and canal patency. The sutures were removed on the 7^th, and the medicated ear wick placed during surgery was removed on the 10^th postoperative day. Topical antibiotic-steroid drops and regular aural toileting were performed. At 3 weeks, the silicone sheet was removed, and the canal plus mastoid cavity appeared well epithelialized.

At the 3-month follow-up, the external auditory canal was patent and well epithelialized. The tympanic membrane was intact and visible. Repeat audiometry demonstrated a 35 dB improvement in air conduction thresholds in the operated ear, with residual minimal conductive loss and improved sound localization. At 6 months, the canal remained open with no evidence of restenosis, and the patient reported improved classroom participation and confidence.

DISCUSSION

The formation of the external auditory canal initiates from the first branchial cleft, with complete development by the 24th week of gestation. Earlier cessation of development, the extent of deformities increased, and decreased the efficiency of therapeutic approaches.⁵ It is classified into three types: Type A- stenosis with intact tympanic membrane, Type B- partial atresia with rudimentary tympanic membrane, Type C- total atresia with absent external auditory canal and tympanic membrane.⁶ EACA is frequently unilateral and may be isolated or associated with syndromes like Treacher Collins, Goldenhar, or Crouzon syndrome.⁷ In our case, the patient had isolated, non-syndromic, right-sided total atresia with a well-developed auricle.

Our patient had normal speech development as left ear hearing was normal, but was having trouble in school due to seating placement. When the affected ear was towards the teacher, he had difficulty comprehending and suffered from poor grades.

Surgical correction of EACA is indicated in selected cases, especially when the Jahrsdoerfer score is ≥7 out of 10 possible points, indicating favorable middle ear anatomy.⁴ Our patient scored 9, with intact malleus-incus complex, incus-stapes connection, present stapes, open oval window, round window, middle ear space, mastoid pneumatization, and a normal facial nerve course—all positive predictors for successful outcomes.

Atresiaplasty is a technically demanding surgery with risks such as restenosis, facial nerve injury, and unsatisfactory hearing gain. Long-term success hinges on precise drilling to create a canal of adequate size and shape, appropriate skin grafting, and prevention of granulation or fibrosis.⁸ In our case, strict postoperative care and regular follow-up ensured a good outcome, with improved hearing, sound localization, and no re-stenosis. Literature has reported a very high rate of re-stenosis following atresiaplasty, approaching 40%.⁹ Various pedicled skin flaps or inferiorly based periosteal flaps have been tried to reduce the risk of re-stenosis with equivocal results.¹⁰ Pre-operatively evaluating the CT film for facial nerve course and careful drilling may avoid facial nerve injury. The anteriorly lying aberrant facial nerve may be an obstacle to canal formation. The nerve may also get injured during soft tissue dissection and excessive retraction.¹¹ We have done posterior transmastoid dissection in this case, first to gain surgical orientation with better delineation of anatomical landmarks, and second for the construction of a wide neocanal without risk of complications.¹² Though some recommend the anterior approach.¹⁰

Alternatives to surgery include bone conduction hearing aids and implantable devices, which are effective but costly, inconvenient, and may not address cosmetic or long-term psychosocial concerns.¹³ Untreated EACA may manifest with delayed language development, learning disability, and increased risk of external canal cholesteatoma.¹⁴ Therefore, surgery remains the treatment of choice in motivated patients with good anatomical candidacy.

CONCLUSION

This case demonstrates that atresiaplasty can be a safe and effective option for unilateral congenital EACA in selected patients with favorable anatomy. Accurate preoperative assessment, proper surgical technique, and diligent postoperative care are key to achieving good functional and anatomical outcomes. Long-term follow-up is essential to monitor for complications such as restenosis or inadequate hearing gain.