Summary

Most otologic surgeons would explore the middle ear of a child with a unilateral conductive hearing loss secondary to trauma, infection, or presumed ossicular fixation (e.g., malleus or stapes). Why, then, the reluctance, or controversy, regarding aural atresia, which, fortunately, is unilateral in most patients? Certainly, the hearing loss resulting from aural atresia is significant both in terms of severity (i.e., maximal conductive deficit) and, as discussed above, in its potential impact on auditory and linguistic development.

The concerns appear to focus on surgical risks and hearing outcome. These issues have been addressed in this chapter. Specifically, it has been documented in the literature that approximately 70% of patients will achieve a hearing threshold of at least 30 dB after surgery, and about 75% of these patients will maintain this level over a longer term. The surgery can be accomplished with minimal morbidity, and a mastoid cavity with its potential for long-term care is not created.

This level of predictability—in terms of both hearing results and complications—is predicated on experience in patient selection and surgical technique. Just as all otolaryngologists, or even otologists, are not equally trained in the various facets of major skull base surgery, the same must be acknowledged for atresia surgery. Optimal treatment for patients with unilateral aural atresia will be realized as more surgeons become trained in managing these patients and as referrals to centers experienced with this condition become a priority.

REFERENCES

Lambert—CHAPTER 70

1. Bess FH. The unilaterally hearing-impaired child: a final comment. Ear Hearing 1986;7:52-54

2. Humes LE, Allen SK, Bess FH. Horizontal sound localization skills of unilaterally hearing-impaired children. Audiology 1980;19:508-518

3. Viehweg R, Campbell RA. Localization difficulty in monau-rally impaired listeners. Trans Otol Soc 1960;48:339-350

4. Tharpe AM, Bess FH. Identification and management of children with minimal hearing loss. Int J Pediatr Otorhinol 1991;21:41-50

5. Bess FH, Tharpe AM, Gibler AM. Auditory performance of children with unilateral sensorineural hearing loss. Ear Hearing 1986;7:20-26

6. Moore DR, Hutchings ME, King AJ, et al. Auditory brain-stem of the ferret: some effects of hearing with unilateral ear plug on the cochlea, cochlear nucleus, and projections to the inferior colliculus. J Neurosci 1989;9:1213-1222

7. Ferguson MO, Cook RD, Hall JW III, et al. Chronic conductive hearing loss in adults: effects on the auditory brainstem response and masking-level difference. Arch Otolaryngol Head Neck Surg 1998;124:678-685

8. Nager GT, Levin LS. Congenital aural atresia: embryology, pathology, classification, genetics, and surgical management. In: Paparella MM, Shumrick D, eds. Otolaryngology. Philadelphia: WB Saunders; 1980:1303

9. Bellucci RJ. Congenital aural malformations: diagnosis and treatment. Otolaryngol Clin North Am 1981;14:95-124

10. De la Cruz A, Linthicum FH Jr, Luxford WM. Congenital atresia of the external auditory canal. Laryngoscope 1985;95:421-427

11. Schuknecht HG. Congential aural atresia. Laryngoscope 1989;99:908-917

12. Jahrsdoerfer RA, Yeakley JW, Aguilar EA, et al. Grading system for the selection of patients with congenital aural atresia. Am J Otolaryngol 1992;13:6-12

13. Lambert PR. Congenital aural atresia: stability of surgical results. Laryngoscope 1998;108:1801-1805

14. Chandrasekhar SS, De la Cruz A, Garrido E. Surgery of congenital aural atresia. Am J Otol 1995;16:713-717

15. Glasscock ME, Storper IS, Haynes DS, Bohrer PS. Twenty-five years of experience with stapedectomy. Laryngoscope 1995;105:899-904

16. Lambert PR. Complications of surgery for congenital atresia. In: Eisele DW, ed. Complications in Head and Neck Surgery. St Louis, MO: CV Mosby; 1993:660-665

17. Jahrsdoerfer RA, Lambert PR. Facial nerve injury in congenital aural atresia surgery. Am J Otol 1998;19:283-287

18. Jahrsdoerfer RA. External auditory canal atresia. In: Lalwani AK, Grundfast KM, eds. Pediatric Otology and Neurotology. Philadelphia: Lippincott-Raven; 1998:533-540

19. Sheehy JL, House HP. Causes of failure in stapes surgery. Laryngoscope 1962;72:10-31

20. Hough JVD. Recent advances in otosclerosis. Arch Otolaryngol 1966;83:379-390

21. Lambert PR. Congenital absence of the oval window. Laryngoscope 1990;100:37-40

Congenital aural atresia results from a failure of canalization of a solid core of epithelial cells that extends from the developing auricle to the tympanic ring and middle ear cleft. The incidence of congenital aural atresia is 1 per 10,000 to 20,000 live births.1 Approximately one-third of cases are bilateral.2 The child with unilateral congenital aural atresia and a normally-functioning contralateral ear will develop language normally and have no significant cognitive, developmental, or social deficits, even without the use of a hearing aid in the affected ear.1'11'12 As such, the decision to operate on the child with unilateral atresia is controversial.

Most cases of atresia of the external auditory canal are accompanied by some form of microtia, although isolated middle ear ossicular anomalies do occur and may not be diagnosed until the child is several years old. Aural atresia can be associated with other craniofacial anomalies (e.g., Treacher Collins, hemifacial microsomia) or can occur as an isolated congenital anomaly. Jafek reported a 14% positive family history;2 atresia is seen in families, although no genetic inheritance pattern has been demonstrated.

Surgery for aural atresia involves a number of steps, with the ultimate goal ofcreating a healed, dry ear canal with liberation of the ossicles to restore the middle ear conductive mechanism. The following steps give a general overview of the procedure:

1. A postauricular incision followed by standard T-shaped periosteal incision is made to identify the atretic bone.

2. Using surface landmarks, including the glenoid fossa, linea temporalis, and cribriform areas, the new ear canal is drilled.

3. The middle ear ossicles are identified and freed from the surrounding bone.

4. A tympanic membrane graft is fashioned from temporalis fascia and lain over the mobile ossicles.

5. A split thickness skin graft is used to line the new bony ear canal.

6. A meatoplasty is created and the skin graft pulled through and sutured to the skin of the native or reconstructed auricle.

Children with bilateral aural atresia have maximal conductive hearing deficits (50 to 60 dB hearing loss [HL]), and if the anatomy is favorable, surgery at age 6 is performed in an attempt to gain hearing. Cholesteatoma will be found in 8 to 14% of children with atretic ear canals.3, 4 Stenosis of the external auditory canal is associated with a higher incidence of cholesteatoma than is complete atresia. One series of 50 patients (54 ears) with an average canal diameter of < 4 mm found a 50% incidence of cholesteatoma.5 No cholesteatoma was found in patients less than 3 years old. The more stenotic (especially < 2 mm) canals had the greater incidence of cholesteatoma. Regardless of middle and inner ear anatomy, patients with cholesteatoma require an operation to clean the ear and eradicate the disease.

Controversy exists, however, in the management of the unilateral atretic ear without cholesteatoma, as the surgery itself is challenging and has potential complications. In addition, the predictability of the final hearing result has been questioned. Improvement in the hearing threshold to > 20 dB eliminates the handicap of unilateral hearing loss;6 achieving that result cannot be guaranteed. The heart of the issue lies in the ability to predict preoperatively which patients have the potential to achieve closure of the air-bone gap to within 20 to 30 dB.

Although the incidence of major complications (total sensorineural hearing loss, facial nerve paralysis, restenosis) has decreased significantly over the years, other complications (high-tone sensorineural hearing loss [SHL], tympanic membrane lateralization) have essentially remained the same. The postoperative ear must be cleaned and debrided regularly (every 6 to 12 months). The postoperative draining ear requires extra attention and cleanings along with restrictions on swimming, exercise, and moisture/water in the ear. An argument can easily be made against operating on the unilateral atretic ear, so long as the contralateral ear is in good health and functioning well.

Nevertheless, thoughtful evaluation and preparation before surgery and advances in surgical techniques have made atresia surgery results more predictable. Patients are carefully chosen for surgery on the basis of motivation, cooperation, and anatomy, as demonstrated on high-resolution computed tomography (CT) scanning. The well-healed postoperative ear is treated normally; we even allow patients to swim. Older patients who have developed presbycusis or patients who suffer hearing loss in the unaffected ear are potentially excellent candidates and may reap the rewards of surgery. Given the improved predictability ofresults ofatresia surgery, we feel that the benefits of binaural hearing, sound localization, and improved hearing in noise outweigh the risks of surgery. In the hands of an experienced atresia surgeon, we favor atresiaplasty in the unilateral atretic ear, if the patient is motivated, cooperative, and a good candidate (minor malformations) anatomically.

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