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Features Departments Information |
  Nancy M. Young, MD
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Congenital aural atresia NANCY M. YOUNG, MD aFall 1996 CONGENITAL ATRESIA of the external auditory canal may occur as an isolated finding or in association with other craniofacial anomalies. Aural atresia is most commonly a unilateral finding but can occur bilaterally. It is important to identify these children early in life in order to evaluate their hearing and to counsel their families regarding possible complications and treatment options. Initial Identification and Management A malformed pinna alerts the family and the physician to the presence of aural atresia. In fact, with the sole exception of patients exposed to thalidomide in utero,1 severe microtia of the pinna is always accompanied by atresia. However, congenital aural atresia may be found in the presence of a completely normal auricle. The opening into the canal may be completely absent, or there may be a blind sinus or tight stenosis leading to an abnormally small tympanic membrane. It is imperative that infants with atresia, whether unilateral or bilateral, undergo a complete audiologic evaluation including an auditory brainstem evoked-response test. At least a moderate conductive hearing loss will be present in an atretic ear. This degree of loss means that the atretic ear will not be useful in terms of understanding spoken language at normal conversational levels. A hearing deficit may also be present in the child’s normal-appearing ear.  FIGURE 1. Child with bilateral atresia wearing a bone-conduction aid. The bone conductor is held against the mastoid region by a headband. Children with bilateral atresia must be fitted with amplification as soon as possible. Because of the absence of the usual pathway through which sound from a hearing aid is transmitted into the ear, a special bone-conduction hearing aid must be utilized. The device is strapped against the skull over the mastoid region (Figure 1). Sound picked up by a microphone is transduced into mechanical energy that causes vibration of the temporal bone that directly stimulates the cochlea. Children with unilateral atresia need to have the hearing in their normal-appearing ear carefully assessed. In some cases, a significant hearing loss is present in the externally normal ear. The loss is typically due to congenital ossicular fixation. Prompt intervention is necessary in order for these children to receive an optimum amplification system that will enable development of normal speech and language. Children with unilateral aural atresia who have one normal-hearing ear can be expected to develop normal speech and language during the pre-school years. However, as is true for any individual with a significant unilateral hearing loss, they will have more difficulty hearing than do peers with two normal-hearing ears. They are particularly disadvantaged in listening situations where background noise is present. Therefore, the minimum recommendation is preferential seating in the classroom with the normal-hearing ear toward the teacher. Despite this measure, if hearing problems or academic skills remain a concern, an FM unit (an assistive listening device that transmits the teacher’s voice and eliminates background noise) may be helpful. For ideal candidates, surgical correction of aural atresia is another treatment option. With rare exceptions, patients with atresia of the external auditory canal have a ventilated middle ear space. For this reason, they can develop acute otitis media requiring empiric treatment. Therefore it is important to remember that atresia patients can develop complications of both acute and chronic otitis media. Their abnormal anatomy renders diagnosis and treatment of these problems more challenging since direct visualization of the tympanic membrane cannot be achieved. Children with Sinus Tracts or Severe Stenosis Children with aural atresia who have blind sinus tracts that are narrowed laterally, as well as those with severe stenosis of the entire external auditory canal, are at risk for developing acquired canal cholesteatoma. The canal architecture in these two congenital situations predisposes patients to the trapping of squamous debris from the skin-lined canal cavity. Having a bony ear canal with a diameter of two millimeters or less clearly places these patients at high risk for cholesteatoma formation. If canal cholesteatoma is not diagnosed, extensive destruction of the ear typically occurs by adolescence or early adulthood.2 Consequently, close follow-up of these patients is warranted. Surgical intervention is usually needed by six to 12 years of age in order to create a safe ear. Surgical Repair Children with bilateral atresia benefit significantly from surgical reconstruction. After surgical improvement of the hearing in one ear, they no longer need a bone conduction aid. They gain access to a broader range of frequency information and as a result have higher fidelity hearing. In addition, they are freed from using very visible and cumbersome external hardware. Children with unilateral atresia also benefit from surgical reconstruction. Successful surgery enables these children to enjoy the benefits of binaural hearing, which includes the improved ability to recognize speech in noisy environments such as the typical classroom. A number of studies have demonstrated that children with only a single hearing ear are more likely to have academic difficulties because of their poor auditory perceptual skills.3 Therefore, surgery in children with unilateral atresia, especially in cases where the family and teachers are concerned about academic progress, may be very rewarding. Candidacy for surgical reconstruction is best determined between five and seven years of age. By that time, the majority of mastoid growth has occurred, and the microtia repair, if needed, is well underway. In the vast majority of patients, reconstruction of the aural atresia is considered for the purpose of improving hearing. To achieve this goal, the hearing loss must be conductive in nature; the atretic ear must have normal cochlear function. In the fewer children who are at high risk for the development of acquired canal cholesteatoma, surgical reconstruction of the canal is beneficial even if improvement in hearing is not a realistic goal. High-resolution computed tomography of the temporal bone is necessary to determine whether improved hearing would be a realistic outcome of atresia surgery. All atretic ears have abnormal middle-ear anatomy to a greater or lesser degree. However, the radiographic appearance of seven critical anatomic elements are important in determining favorable candidacy for reconstructive surgery (Table 1).4 The degree of abnormality of these structures as determined by computed tomography typically excludes half of atretic ears from reconstructive surgery.
Children with bilateral atresia whose hearing cannot be improved by reconstructive surgery are candidates for the Audiant™ temporal bone implant.  FIGURE 2. Hermetically sealed rare-earth magnet is implanted into the mastoid bone behind the external ear. The skin is closed over the magnet. This device consists of a rare-earth magnet that is implanted into the mastoid region of the temporal bone (Figure 2) and an external sound receiving/processing device (Figure 3). Sound is transmitted directly to the temporal bone and inner ear via magnetic coupling of the external and internal portions of this device.  FIGURE 3. The external components of the Audiant behind-the-ear processor consist of a microphone, processor, connecting cord and an adjustable coil that contains a magnet. Case Studies  FIGURE 4. A child with right microtia and aural atresia. She has a conductive loss secondary to congenital ossicular fixation in her normal-appearing ear. Case 1: Ellen was born with right-sided complete cleft lip and palate and right grade III microtia and complete aural atresia (Figure 4). At the time of her lip repair at two months of age, she underwent placement of a PE tube in her left, normal-appearing ear. Postoperative auditory brain- stem evoked-response testing revealed the presence of a moderate conductive hearing loss in both ears. She was fitted with a traditional hearing aid for her left, normal-appearing ear.  FIGURE 5. Left facial paralysis secondary to otitis media in a child with left aural atresia. Case 2: Henry is a two-year-old with left microtia and complete atresia. He also has a history of intermittent episodes of right acute otitis media. Several days after diagnosis and initiation of treatment for a right acute otitis media, Henry developed sudden onset of left facial paralysis (Figure 5). He was otherwise asymptomatic and afebrile. Computed tomography revealed opacification of the left middle ear cavity and the mastoids bilaterally. Henry was begun on intravenous antibiotics for left otitis media complicated by facial paralysis. Myringotomy with drainage could not be performed because of the presence of aural atresia. For this reason, a simple mastoidectomy was performed. This permitted drainage of the left middle ear space through its natural connection to the mastoid cavity. The patient experienced return of normal facial nerve function over several weeks. Case 3: Kelly is an eight-year-old female who presented with sudden onset of left ear pain and drainage. She was born with an extremely stenotic left ear canal that did not permit visualization of the tympanic membrane. A long-standing conductive hearing loss was also present in the left ear. Her speech and language development were normal. She had been without otologic complaints until the recent onset of severe left ear pain. Otoscopic examination revealed normal pinnas bilaterally. The right ear canal and tympanic membrane were unremarkable. An opening of less than two millimeters was present in the left conchal area. Examination under the operating microscope revealed granulation tissue deep to the opening. However, the length of the patient’s skin line tract could not be determined.  FIGURE 6. The congenitally stenotic bony external auditory canal is widened medially by cholesteatoma. Computed tomography revealed the presence of a narrowed external auditory canal that was severely stenotic laterally. The canal was filled with soft-tissue density. Diagnosis of canal wall cholesteatoma was made based on evidence of widening of the bony ear canal due to the erosion of bone (Figure 6). The left middle-ear space was also contracted in size, and the ossicular chain was misshapen. However, based on the anatomy demonstrated radiographically, Kelly was found to be an excellent candidate for reconstruction of her sound-conducting mechanism. Kelly underwent removal of a left canal wall cholesteatoma and reconstruction of her external auditory canal. The canal was resurfaced with a split-thickness skin graft. Her ossicular chain was mobilized, and a complete tympanic membrane was created. Her postoperative audiogram demonstrated normal hearing in the reconstructed ear. Case 4: Sandy was initially seen at eight years of age. She had bilateral atresia secondary to Nager’s syndrome, in which mandibulofacial dysostosis is associated with radial defects. Both of her pinnae were normal in appearance, however, complete aural atresia was present. Sandy had worn a bone-conduction hearing aid since several months of age and had developed good spoken-language skills. She was mainstreamed in a regular classroom. Computed tomography revealed severe malformations of both the middle ear and mastoid cavities. Surgical reconstruction of aural atresia was therefore not recommended. In order to provide Sandy with improved sound quality and to eliminate the use of a headband, implantation of an Audiant™ device was done. At this time, Sandy has used the Audiant™ successfully for four years. She describes improved sound quality and better hearing at a distance and when background noise is present. These observations have been confirmed by her parents and classroom teachers. Conclusion All children with congenital aural atresia need to undergo complete audiologic testing during infancy. Early intervention with appropriate amplification for any child with bilateral hearing loss is necessary to insure normal speech and language development. Parents and their child’s primary care physician also need to be aware that otitis media and its complications can occur in the child’s atretic ear. Surgical management can help to improve the hearing of some patients with aural atresia. In other patients, surgical intervention may be required to treat complications of otitis media or cholesteatoma. REFERENCES 1. Cole RR, Jahrsdoerfer RA: Congenital aural atresia. Clin Plast Surg 1990;17:367–71. 2. Cole RR, Jahrsdoerfer RA: The risk of cholesteatoma in congenital aural stenosis. Laryngoscope 1990;100:576–8. 3. Bess FH, Tharpe AM: Case history data on unilaterally hearing-impaired children. Ear Hear 1986;7:14–9. 4. Jahrsdoerfer RA, Yeakley JW, Aguilar EA, Cole RR, Gray LC: Grading system for the selection of patients with congenital aural atresia. Am J Otol 1992;13:6–12. |