| Disclaimer: The information contained within the Grand Rounds Archive is intended for use by doctors and other health care professionals. These documents were prepared by resident physicians for presentation and discussion at a conference held at Baylor College of Medicine in Houston, Texas. No guarantees are made with respect to accuracy or timeliness of this material. This material should not be used as a basis for treatment decisions, and is not a substitute for professional consultation and/or peer-reviewed medical literature. Aural Atresia So, this morning, I would like to just briefly go over aural atresia and, of course, no good congenital talk is without a good embryology review so we will talk about that and go over some history on the treatment and management of this disease, the different classification systems, the work-up and management of the patient, and some of the different issues regarding medical versus surgical, unilateral versus bilateral disease. Starting off with our embryology, general knowledge of the embryologic development is essential for understanding why aural atresia presents the way that it does. It is important to recognize that the development of the inner ear, the middle ear, and external ear occur independently of one another, and, therefore, the malformation of one does not necessarily presuppose malformation of the other. It is important to understand the final location of the otic capsule and development of the inner ear structures and the cochlea. Often, you see frequent abnormalities of the outer and middle ear but this occurs in the setting of a normal inner ear, and this is because the inner ear often develops before that. Starting with the auricle. The auricle development begins in the fourth week of gestation. It develops around the first branchial groove from the first or the mandibular arch and the second hyoid branchial arch. These arches then go on to form what is known as the sixth helix of His and then through development progress to form the pinna by the third month of gestation. The external auditory canal develops from the first branchial groove, between the mandible and the hyoid arches. At about 4-5 weeks, the ectoderm of the first groove comes into contact with the endoderm of the first pharyngeal pouch. This then splits, and then the mesoderm grows in between, and by the eighth week this groove starts to extend medially as what is known as the cavum concha and develops into the funnel-shaped tube to form the primary meatus. This eventually becomes surrounded by cartilage to form the outer one-third of the external auditory canal. This groove again deepens and grows medially towards the middle ear and comes into contact with the first pharyngeal pouch. There is a residual epidermal plug that extends in from the primary meatus into the primary tympanic cavity, which forms the meatal plate. The mesenchyme which grows between this forms the substantia propria of the tympanic membrane. By the twenty-first week, the cord of the epithelial cells begin to resorb and then form the bony portion of the external auditory canal. By the twenty-eight week, the deepest cells of the ectodermal plug remain and form the superficial layer of the tympanic membrane. The medial two-thirds, as I stated, of the ectodermal tomb becomes the bony portion of the canal, and the tympanic membrane is formed from all three layers from the ectoderm, the mesoderm, and the endoderm. This is just another schematic sort of demonstrating that you have the pharyngeal pouch which extends and forms the tubotympanic cavity. You have the external auditory meatus primitively which extends in medially, and you have the mesoderm which grows here and forms later into the rudimentary ossicle, and then concurrently, you have the development of the otic capsule and the internal ear structures. So, the tympanic cavity occurs during the third week by expansion of the first pharyngeal pouch, which is lined by endoderm to form this tubotympanic recess. This progressive expansion occurs from the fourth to the sixth week, and by the seventh week, the eustachian tube begins development medially, and the tympanic cavity forms laterally. By the eighteenth week, the epitympanum develops from the tympanic cavity which leads into the antrum and mastoid. The pneumatization of the mastoid is the latest embryologic event which occurs in the seventh to eighth month and continues on postnatally. Ossicular development, as I stated, forms from the mesenchyme which grows in between those two plates The head of the malleus and the short crus on the body of the incus occurs from the mesenchyme of the mandibular arch. The manubrium of the malleus, the long process of the incus, the head, neck and crura of the stapes occur from the hyoid arch. The medial surface of the stapes, however, occurs from the otic capsule which explains why often times you have an intact footplate in the setting of atresia. This here is the development at two months, at four months gestation, at oops, I'm sorry. This is two months, this is three months, and this is four months. Here at six months, you begin ossification of the ossicles. Here, it is just in the cartilaginous form, and then here is the final adult structure. So, congenital atresia is a birth defect characterized by hypoplasia of the external auditory canal and is often associated with abnormalities of the auricle, the middle ear, and occasionally the inner ear structures. It is often seen in association with numerous syndromes and disorders such as Treacher Collins syndrome but isolated atresia can also be seen. It occurs in approximately one to ten thousand to one to twenty thousand live births. Small, little, other interesting facts are males are more often than females, bilateral atresia is found in 30% of cases, and the right ear is often more afflicted than the left. Briefly, just to go over some history, in the 7 th century, Paulus of Aegina made the first accurate description of atresia of the ear. He distinguished between superficial and deep atresias, and he recommended excision when possible. In 1883, Kiesselbach attempted the first surgical correction of aural atresia. This patient, unfortunately, resulted in a facial paralysis. Since that time, not much work has been reported regarding aural atresia repair. There have been some anecdotal comments about treating it with a hot poker or cauterization but I could not find much else on any other descriptions for repair. In 1947, Pattee and Ombredanne independently reported hearing improvement in atresia repair by removing the fixed incus to mobilize the stapes, and Ombredanne reported fenestration of the horizontal canal. In the 1950's, further interest in atresia repair developed with advances in ossicular manipulation and tympanoplasty techniques from the works of Zollner and Wullstein. Durlacky in 1968 first advocated the use of polytomography in analyzing and assessing these patients, and then further advances in the development of ABR techniques and CT scanning have brought atresia repair to where it is today. Jahrsdoerfer monograph in 1978 sort of serves as today's landmark reference for atresia repair although numerous other authors have described this as well. Congenital atresia can range in severity to thin, membranous canal atresia to a complete lack of tympanic bone maturation depending on the time of arrest in intrauterine development. The usual finding of a normal inner ear is often explained as I stated by the fact that the inner ear has already formed by the time of external or middle ear developmental arrest. There have been multiple classification schemes that have been proposed over time. It has been my impression that the Altman is the one that is most popularly used. This was first described in 1955. Altman classified these into three different categories, the first being mild atresia where the external auditory canal is often present but hypoplastic. The tympanic bone is hypoplastic but often there is a well-aerated middle ear space. There may or may not be ossicular abnormalities. The tympanic membrane is often small, and if you do see ossicular abnormalities, usually what you see is fusion of the ossicles, and often the malleus is more misshapened than the incus. His second category for moderate atresia is where the external auditory canal is absent and replaced by an atretic plate. The tympanic bone can be either partly or completely ossified. There is still a middle ear space but the ossicles are often fixed and malformed. In cases of severe atresia, this includes those not only with an absent external auditory canal but often a contracted or absent middle ear space where ossicles are often absent as well. These patients are poor surgical candidates. There have been other modifications of this classification system, and they have incorporated surgical guidelines as well. These include classifications by Delacruz, Ombredanne, and Nayer. Another classification system based on Altman's classification is Coleman's classification system. He added some modifications to incorporate surgical recommendation. In his minor aplasias, the made meatus and drum are present but abnormal, the stapes is generally abnormal, the suprastructure is, but he states that these patients' surgery can be performed through the transcanal approach, and patients tend to have good results. In patients with major aplasia, there is a complete bony meatal obliteration with complex ossicular abnormalities. For these patients, surgical repair would often require a mastoidectomy, leaving the patient with postoperative cavity care. The results he found were often disappointing. In his final classification scheme, severe atresia with absent pneumatization, and these patients are extremely difficult and very poor surgical candidates, often fraught with complications. Schucknecht came up with another classification system in 1989 which came out a laryngoscope, and this was also based on a combination of both clinical and surgical observations. Type A meatal atresia is atresia that is limited just to the fiber cartilaginous portion of the external auditory canal. Because the external auditory canal is so small, natural egress of normal desquamating epithelium is very difficult. Therefore, these patients are prone to developing canal cholesteatoma. The treatment of choice for these patients is a meatoplasty. Type B of Schucknecht’s classification is a partial atresia which is characterized by narrowing and a tortuosity of both the fiber cartilaginous as well as the bony portion of the external auditory canal. In these patients, the tympanic membrane is often hypoplastic or even maybe partially ossified, and the ossicles may or may not be abnormal. In Type C atresia, characterized this as total atresia where there was a completely atretic canal but these patients also have a well-developed pneumatized tympanic cavity where there is either a partial or complete bony atretic plate to replace the tympanic membrane. There are often ossicular abnormalities where the manubrium may be absent, and the facial nerve often takes an anomalous course in these patients. His last classification is similar to Coleman's, and this is complete absence of a pneumatized temporal bone. The patients also have a very aberrant course for their facial nerve, and are, therefore, very poor surgical candidates. In 1992, Jahrsdoerfer performed a retrospective analysis of 86 patients who underwent repair. Based on these patients and their results, he developed a grading system which is predictive of the surgical results based on their anatomy. The score correlates with percent change of restored hearing which he considered between 15-25 dB for speech reception threshold. So, patients who have a score of 8 or higher are going to have an 80% chance or greater of having a successful atresia repair. Scores of 6-8 have a moderate to fair chance of having a good result, and patients with scores less than 5 are considered poor surgical candidates. The presence of the stapes, he stated, was the most important. So, just to illustrate that point a little bit, in this CT scan example, the patient as you can see has complete absence of a pneumatized cavity, and so, therefore, his score would be clearly less than 5, and he would be a poor surgical candidate although he does have presence of a cochlea. In this case, the patient does have a pneumatized cavity as well as presence of ossicles, round window, stapes, as well as at least a fiber cartilaginous entrance for his external auditory canal. So, this patient has a reasonable chance of having a favorable atresia repair result. In evaluation of the patient, initially, it is important to assess any prenatal and maternal history, rule out any toxic exposures, drug use, or severe maternal infections. You want to make sure that there is no family history of developmental disorders or hearing impairment. You want to also do a thorough, complete physical examination, make sure you are not overlooking any other associated congenital anomalies, particularly other craniofacial anomalies, particularly in the mid face and mandible. You want to note also the position of the auricle from its anterior migration posteriorly. The most common associated facial function anomaly is congenital absence of the depressor anguli oris muscle associated with atresia. You also want to make sure that you look at other organ systems, you do not overlook any other abnormalities there. The patient evaluation in working this patient up, the first thing is to assess the overall hearing status and to ascertain the need for immediate amplification for the patient. It is important to recognize that this is a sensitive issue for many patients and parents, and that parents often have a sense of urgency and anxiety related to this matter. It is important to be sensitive in the counseling and reassurance and to reassure them that when you do the timing of the repair that often the repair is not an immediate but a delayed repair. You need to get involved multidisciplinary teams such as plastic surgery, genetics, and developmental pediatrics or any other subspecialties may need to be recruited. So, as far as the first work-up, it is important to do a complete audiologic evaluation. A screening of bone conduction ABS is necessary. You want to first be able to establish the presence of a functional inner ear. In cases of bilateral atresia, the way one responds to the ABR can be ear-specific so it permits differential evaluation of cochlear function from side to side. This is important to recognize in only hearing ear, and any poor potential for surgical improvement. Additionally, it is important to recognize that any suspicion of a conductive hearing loss in the range of 40-60 dB in the absence of trauma or infection can be highly suggestive of congenital ossicular malformation or other types of minor atresias. Also, in patients with apparent unilateral atresia, a conductive hearing loss is identified in the normal-appearing ear in up to 27% of cases, which would identify bilateral atresia. If the child presents at an older age and not at infancy, basic audiometry is also helpful. So, as I stated, CT scanning and imaging is the other key modality in working up the patient. Scanning is usually deferred until the patient is at least 4-5 years of age which would be around the time of the preoperative evaluation. The reasoning for this is the patient is more cooperative, at least to be able even to undergo the CT scan at this time, and you have more time to permit complete development and pneumatization of the mastoid. The indications for immediate scanning would include any suggestion of inner ear abnormalities such as severe sensorineural hearing loss on the ABR, suspicion for cholesteatoma or other pathology. When performing CT scanning, it is important to have fine cuts of both the axial and the coronal scans. The body of the malleus and the incus and the incudostapedial joint and round window are best often seen through the axial scan. The stapes, oval window and vestibule are best assessed through coronal scan so it is important to have both available so that you can assess the ossicles presence or lack thereof. Cressman found that 50% of patients with atresia are found to be surgical candidates based on CT scan findings alone. This patient again also has presence of the canal, of a tympanic cavity with suggestion of ossicular formation. Other new modalities include three dimensional CT scanning which can help in your work-up and identification of, you know, other anomalies, hemifacial microsomia, micrognathia. So, the otologic goal for management of aural atresia is to be able to provide the patient with serviceable hearing in the affected ear such that he or she can develop normal speech and language. In general, patients with other coexisting craniofacial anomalies or syndromes are poor surgical candidates, and the best surgical candidates are usually the patients with isolated atresia. In cases of bilateral atresias, the patients are effectively deaf unless you provide some form of intervention. So until the patient is of appropriate age, bone conducted hearing aids are usually indicated. Surgical correction of bilateral atresia is usually not questioned given that these patients are otherwise deaf; however, there has been greater controversy regarding whether or not to repair unilateral atresia. So, as I stated, for the medical management of the patient, in a young child with unilateral atresia, the general consensus that I found is that in the presence of a normal contralateral ear, hearing aids are usually not recommended. The patient would probably, in an atretic ear, require a bone conducting aid which would really just provide more interference than any benefit for the contralateral ear. It is recommended that preferential seating be helped for the patient in school. In cases of bilateral atresia, as I stated, early amplification is necessary to facilitate normal language and development. So, as I stated, there has been greater controversy as to whether or not to operate and when to operate on patients with unilateral atresia. Applebaum took a look at this in 1998 reviewing the literature for elective repair of atresias. Currently, most authors agree that elective surgical repair should be attempted at school age if they meet appropriate anatomic criteria to suggest that they will have successful surgery. If you look here, in the early 1980's as well and beforehand, most people recommended against surgical repair given the high rate of complication and the presence of a normal hearing ear on the opposite side. However, as techniques have gotten better, in patients with really good, favorable anatomy where you are fairly confident that the patient will have a good surgical result, you only have presence of maybe a mild atretic plate with normal ossicles in a good pneumatized cavity, most authors currently now say that surgery can be recommended at 5-6 years of age. Otherwise, in patients with other questionable anatomy, it is important to wait until the patient is old enough to make an informed decision for himself, knowing both the risks, benefits, and consequences of surgery. It is important to recognize that binaural hearing does provide the benefits of improved sound vocalization, enhanced speech recognition against background noise and stereo perception of sound, and for these reasons, authors have become more stronger proponents for unilateral repair. The timing of repairs, as I stated, should be considered when the patient is at least 4-5 years of age when the mastoid is more pneumatized. More importantly, it is also to consider this when the patient is going to be more cooperative with both your preoperative work-up as well as your postoperative care. These patients are going to need a lot of postoperative care with respect to taking care of the canal or the cavity and any other complications that might be related to surgery. Unlike other otologic surgeries, the surgery is performed on the better hearing ear in cases of bilateral atresia, and this is to provide the patient with the best chance for successful outcome. Since the patient is delayed till 4-5 years as I stated, bone conducted hearing aids are usually helpful prior to then. Most cases occur in the setting of microtia, and so it is important to coordinate with the plastic surgery team when to do the repair. Usually, the atresia repair is done at the third stage of the multistage repair for microtia. The first step for microtia repair is to do implantation of the auricular framework which is often autogenous rib graft in the subcutaneous pocket. You want to be able to do this step first because you want to have unoperated vascular supply such that your graft is not compromised. Then, often it is easier to coordinate where you place your canal with where the existing auricle is than the other way around. Traditionally, the transmastoid approach was used for aural atresia repair, and this is based on using the familiar landmarks of the tegmen and the sinodural angle to approach the antrum and reach the meatal plate. The facial recess is then opened and the incudostapedial joint is separated. The facial nerve monitoring is very important in these procedures because the facial nerve often has an anomalous course. Using this technique, patients often result in a canal wall down mastoidectomy so you need to consider that this patient will also have to deal with cavity care and that kind of postoperative management. Newer techniques based on the transmastoid approach have done this through a canal wall intact approach. The newer approach popularized by Jahrsdoerfer is what is most commonly reported in literature today. This is the anterior approach, and this is where the approaches begin just posterior to the condyle and uses the middle fossa as your superior guide and the posterior aspect of the condyle is your anterior guide for your landmarks. Drilling begins, therefore, laterally to medially to permit exposure of the tympanum and the ossicular mass. As you approach closer to the ossicular mass, you switch to diamond burrs and using curettes in laser technique to remove the atretic plate with care taken not to injure or contact the ossicular plate to avoid transmission and injury that way. You want to be able to try and assess the mobility of the ossicular chain, the stapes, or status of the oval and round window, if possible. Ossicular chain reconstruction is performed with a prosthesis, if necessary. However, it has been my finding through the literature that even in the setting where the ossicular mass is malformed, if it is in an immobile chain, it is better, the hearing results have been better if using the patients' native ossicular mass than by replacing it with prosthetic material. This approach is reported to have less risk of injury to an anomalous facial nerve. Once you have completed your drilling down to the level of the ossicular plate, lifted it out, the temporalis fascia is harvested to create your new tympanic membrane. At this point, careful measuring of a split-thickness skin graft is then fashioned and placed to line the new canal, and then sutured to your new meatoplasty. The donor site for the skin is often taken from the abdominal wall. The meatoplasty is performed as the final place and, therefore, is placed in continuity with your newly constructed canal. It is important to recognize that your meatoplasty should be approximately twice the normal size to account for anticipated stenosis. Stenosis is the most common complication following this surgical procedure, and placement of Merocel wicks has been performed to try and minimize this complication. It is difficult to compare the surgical results that have been reported by all of these authors given that their criteria and indications for surgery have been variable, patient selection is not consistent, the technique used, and obviously the variable degrees of atresia in each patient. However, what they considered a successful surgical result would be improved hearing to 30 dB or better, and they state in more recent literature that successful results can be achieved in approximately 40-75% of patients. The complication rate, however, has been fairly high between 30-70%. On the complications, if you notice, the intraoperative complications include facial nerve injury. Sensorineural deafness and perilymph fistulas. The rate of these complications has diminished with improved technique over time. However, the postoperative complications of meatal stenosis, lateralization of the graft, and chronic drainage from the ear continue to persist today. So, just in summary, aural atresia is a developmental anomaly of the external auditory canal and the middle ear. A complete audiometric and CT evaluation is essential prior to any consideration for surgery. The surgical options are not really considered until the patient is usually at least 4-5 years of age. In the setting of favorable anatomy, Grade I or II atresia where there is at least a pneumatized tympanic cavity, presence of some ossicles, the success rates for surgery with a speech reception threshold of 25 dB or better can often be achieved in the right hands in up to 75% of patients. Case Presentation: Z.S. is an infant boy born at 37 weeks by cesarean section at an outside hospital with multiple congenital abnormalities, weighing 2770 grams. He was transferred to Texas Children’s Hospital for failure to thrive and further work-up and management. Maternal history is negative for prenatal infections or toxin exposures. Family history is significant for a cousin with congenital cardiac anomalies. His congenital anomalies include right microtia, cleft lip and palate, micrognathia, transposition of the great vessels, ASD, PDA, hypospadias, abnormal vertebrae with partial fusion of ribs, left coloboma. Genetic work-up reveals normal chromosomes. Otolaryngology service was consulted for evaluation of microtia and hearing. Physical examination of the ears reveals a normal appearing but anteriorly displaced left auricle, with an anteriorly and inferiorly displaced Marx grade II microtia on the right. An ABR was consistent with severe mixed hearing loss on the right, with severe sensorineural hearing loss on the left. CT scan of the temporal bones on the right reveals ossicles, cochlea, but anomalous development of the vestibule ad lateral semicircular canal. The left ear is consistent with a unilocular sac in the expected location of the vestibule and cochlea. He is to be fitted for a right bone conducting hearing aid when medically stable. Bibliography: Aguilar EF. Auricular reconstruction of congenital microtia (grade III). Laryngoscope 1996;106:1-26. Bauer GP, Wiet RJ, Zappia JJ. Congenital aural atresia. Laryngoscope 1994;104:1219-1224. Chandrasekhar SS, De La Cruz A, Garrido E. Surgery of congenital aural atresia. Am J Otol 1995;16:713-717. Chang SO, Min YG, Kim CS, Koh TY. Surgical management of congenital aural atresia. Laryngoscope 1994;104:606-611. Cole RR, Jahrsdoerfer RA. Congenital aural atresia. Clin Plast Surg 1990;17:367-371. Cressman WR, Pensak ML. Surgical aspects of congenital aural atresia. Otolaryngol Clin North Am 1994;27:621-633. Jahrsdoerfer RA. Congenital atresia of the ear. Laryngoscope 1978;88:1-48. Jahrsdoerfer RA, Garcia ET, Yeakley JW, Jacobson JT. Surface contour three-dimensional imaging in congenital aural atresia. Arch Otolaryngol Head Neck Surg 1993;119:95-99. Jahrsdoerfer RA, Kresser BW. Issues on aural atresia for the facial plastic surgeon. Facial Plast Surg 1995;11:274-277. Jahrsdoerfer RA, Worth 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. Kenna MA. Embryology and developmental anatomy of the ear. In: Bluestone and Stool, editors. Pediatric Otolaryngology. Philadelphia: W.B. Saunders; 1990. pp .77-87. Kountakis SE, Helidonis E, Jahrsdoerfer RA. Microtia grade as an indicator of middle ear development in aural atresia. Arch Otolaryngol Head Neck Surg 1995;121:885-886. Lambert PR. Congenital aural atresia: Stability of surgical results. Laryngoscope 1998;108:1801-1805. Lambert PR. Major congenital ear malformations: Surgical management and results. Ann Otol Rhinol Laryngol 1988;97:641-649. Potsic WP, Cotton RT, Handler SD. Surgical Pediatric Otolaryngology. New York: Thieme; 1997. Schuknecht HF. Congenital aural atresia. Laryngoscope 1989;99:908-917. Shih L, Crabtree JA. Long-term surgical results for congenital aural atresia. Laryngoscope 1993;103:1097-1102. Trigg DJ, Applebaum EL. Indications for the surgical repair of unilateral aural atresia in children. Am J Otol 1998;16:679-686. Grand Rounds Archive | Department Home pageBCM Public | BCM Intranet | Privacy Notices | Contact BCM | BCM Site Map | ©2001-2005 Baylor College of Medicine
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