| 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. Congenital Conductive Hearing Loss Conductive hearing loss in children is usually caused by middle ear fluid, but it can also be caused by congenital anatomic abnormalities. Today we will review the incidence of congenital conductive hearing loss and the most common types of middle ear anomalies found. We will discuss diagnosis, audiology testing, and the role of CT scans in appropriate management. I will also present the postoperative results found in the literature and the results of my research project from our own Baylor College of Medicine iinstitution. This topic is important because the diagnosis and treatment of hearing loss is critical for normal speech and language. Hearing impairment during childhood can affect social and emotional development, behavior, attention, and academic achievement. It has been shown in multiple studies that children with hearing loss do not learn as well and eventually suffer in psychosocial growth and even in their socioeconomic performance. To avoid these consequences, we must identify the hearing loss early and either amplify it or surgically correct it. Delay in diagnosis can be severe because schools are auditory verbal environments. Even mild or unilateral hearing loss may have a detrimental affect on the development of a young child. Some cases of hearing loss are misdiagnosed because affected children have sufficient hearing to respond to environmental sounds and they can even learn some speech and language, but when challenged in the classroom they cannot perform to full potential. Hearing loss should be considered in any child with speech and language difficulties or poor grades, poor behavior, or inattention in school. Conductive hearing loss is the most common type of hearing loss in children, and it occurs when sound transmission is physically impeded in either the external and/or the middle ear. Acute otitis media, otitis media with effusion, and chronic otitis media are the most common causes of childhood conductive hearing loss. Other common causes are cholesteatoma as shown here, and oral atresia, stenosis, and impacted cerumen or foreign bodies. Children with obvious anomalies such as bilateral atresia are usually appropriately recognized and managed early; but children with congenital conductive hearing loss are often unrecognized, incorrectly diagnosed as sensorineural, or attributed to concurrent otitis media. Otitis media with effusion is by far the most common etiology for hearing loss in the pediatric population; however, once appropriate ventilation of the middle ear has been established, either after medical therapy or PE tubes, it is important to confirm closure of the air-bone gap. Normalization of hearing must be documented in order to identify those children who have congenital conductive hearing loss or permanent sequelae from the otitis media. The pathogenesis of most congenital middle ear anomalies is poorly understood. This picture shows the development of the external and middle ears. There is a solid core of epithelial cells extending toward the first pharyngeal pouch from the primitive external canal. The ossicles grow only during the first half of fetal life, after which they ossify, having attained full adult size. The cartilage of the first and second brachial arches forms the malleus, incus, and part of the stapes. The middle ear ossicles first appear in the fifth week. The malleus and incus emerge from a bridge between Meckel’s cartilage and Reichert’s cartilage. The stapes, which can be seen here, develops in the sixth week in the second brachial arch forming a ring around the stapedial artery. These are the four main theories for middle ear anomalies. If Meckel’s cartilage fails to resorb completely, this may result in bony bridges tethering the malleus or incus to the epitympanum. Second, a child may have incomplete aeration of epitympanic space. Congenital stapedial fixation usually occurs at the level of the footplate. The annular ligament normally forms at 16 weeks allowing the footplate to move independently of the otic capsule, so fixation of the footplate can occur when the annular ligament either fails to fully differentiate from the otic capsule bone or the annular ligament may develop normally and then become ossified secondarily. These defects are very rare. In 1993, Dr. Stewart and Dr. Downs studied 565 children with hearing loss. Only 54 children, or 9.5%, had conductive hearing loss unrelated to otitis media. Thirty-seven children had syndromes and 14 children had microtia or atresia. Only three children, or 0.5%, were found to have an isolated middle ear anomaly. In 1994, Dr. Bergstrom studied 687 children with congenital hearing loss. He found that 17% of this was conductive and only 0.1%, or eight of the 687 children, had an isolated middle ear defect. Twenty five percent of congenital middle ear anomalies occur in conjunction with inherited syndromes. These include brachial-oto-renal syndrome, Treacher Collins, and Klippel-Feil. This child had Treacher Collins syndrome with the typical deformed mandible, fishmouth deformity, and down-slanting eyes. Other syndromes associated with congenital conductive hearing loss include Crouzon syndrome, which this child has, Apert’s, CHARGE association, and Goldenhar syndrome. It is challenging to evaluate hearing loss in children because it is difficult to obtain direct histories, to perform adequate physical examinations, and to do tuning fork and audiologic testing in the pediatric population. The early detection of isolated congenital conductive hearing loss is not easy, and it requires a high index of suspicion. The presence of syndromic features or craniofacial defects are warning signs as is a positive family history or suggestion of prenatal injury. Children with isolated middle ear anomalies who are otherwise normal most often suffer delayed diagnosis. This is particularly true in those with unilateral anomalies, which may be diagnosed only at school screenings such as our case report. A careful history should be obtained from the parents and from the child. Delineating the onset of symptoms is important because congenital middle ear anomalies will create a fixed defect from early childhood. History is usually positive for non-progressive hearing loss and usually negative for recurrent ear infections. School performance and language development should be assessed. Prenatal history and family history of hearing loss are also important. A review of systems may reveal associated cardiac, renal, or other medical problems suggestive of a syndromic diagnosis. Physical examination should be performed watching for abnormal facies or developmental anomalies, particularly those originating in the first and second branchial arches. Otoscopy may reveal an abnormality of the tympanic membrane, malleus, or incus; but usually the tympanic membrane will have a normal appearance. Audiologic testing should be performed in an age appropriate manner. If the child presents at 4 or 5 years of age or older, pure tone audiometry is used to assess hearing acuity. Children presenting for assessment between 2.5 and 4 years of age can be tested using play audiometry. In younger children, visual reinforcement audiometry can be used to assess air conduction thresholds. Threshold ABR is the test of choice in infants under 6 months of age. Children with suspected congenital anomalies should be evaluated with temporal bone CT. CT scan is useful in both diagnosis and planning of surgical intervention. Axial and coronal images should be obtained to accurately delineate the bony labyrinth, middle ear, and facial nerves. The scan can help identify any contraindication to surgery such as gross anomalies of the inner ear. Inner ear anomalies may coexist with ossicular malformations and are suggested by the presence of mixed conductive and sensorineural hearing loss. This shows a Mondini deformity with a dysplastic inner ear with a dilated and tortuous internal auditory canal. If you see on CT scan a widened lateral internal auditory canal or an enlarged vestibular aqueduct as shown here, the child is at higher risk for a stapes gusher and may do better with hearing aids. On this CT scan, you can see the cochlea only with one and a half turns and an underdeveloped vestibule as well. On some CT scans, you can also identify an aberrant facial nerve crossing the oval window or a persistent stapedial artery. After the diagnosis is made, treatment options should be presented to the family considering the particular needs of the child. Congenital conductive hearing loss due to ossicular deformities can be treated by either rehabilitation with a hearing aid or surgical reconstruction. Children with a unilateral conductive hearing loss and normal contralateral hearing can be managed conservatively with preferential seating with or without a hearing aid, and surgical management should be deferred until the child is old enough to participate in the decision making process. Bilateral conductive hearing loss should be immediately addressed with amplification. Surgical candidacy can then be addressed. It is better to defer definitive surgical intervention until the child is no longer vulnerable to poor eustachian function and recurrent otitis media. The literature varies with regards to the minimum age required for surgery, ranging anywhere from 5 to 10 years of age. This is particularly important when considering stapes surgery given the risk of perioperative labyrinthitis and sensorineural hearing loss. Surgery is typically reserved for a moderate to severe conductive hearing loss, usually with a speech reception threshold greater than 35 and a pure tone average of greater than 30 dB. The ear with poor threshold is selected for surgery, and it should not be performed on an only-hearing ear. General anesthesia is usually indicated for middle ear exploration. Once the ossicular chain is exposed, each ossicle should be independently palpated. Congenital anomalies of the malleus and incus are often encountered upon reexploration after failed stapes surgery. Occasionally, it can be difficult to determine if an ossicular deformity is congenital or acquired. Malleus head fixation may be a congenital anomaly, but it can also result from trauma, inflammation, or previous surgery. The long process of the incus can be congenitally absent, but it is also often eroded in chronic otitis media. Today I will not discuss the technical details of middle ear repair. These depend on patient anatomy and surgical preference. In an attempt to provide a basis for comparison of results, various authors have defined classification systems for congenital anomalies. Drs. Teunissen and Cremers described a classification system in 1993. The found that they could divide the middle ear abnormalities into one of three classes: ossicular lesions requiring reconstruction without opening the inner ear, stapedial footplate fixation requiring mobilization or stapedectomy, and finally oval window and facial nerve anomalies not amenable to stapedectomy. Congenital fixation of the stapes was first described by Dr. Shambaugh, who is pictured here, in 1952. The underlying pathology involves ossification of the annular ligament and ankylosis of the stapes footplate. It was the most common congenital anomaly encountered by multiple authors. The main differential includes childhood otosclerosis, which is characterized by positive family history and progressive conductive hearing loss. The main risk of fenestrating the footplate in this case is the occurrence of a perilymph gusher. The true incidence of perilymph gusher is unknown. Most of these patients have been males, and it is thought that congenital stapedial fixation with associated perilymph gushers is due to an X-linked inheritance. If the CT scan shows evidence of a widened cochlear aqueduct or internal auditory canal, this should be considered a relative contraindication to surgery. Postoperative results are mixed. In 1999, Dr. de la Cruz reviewed the House Ear Clinic results for 95 ears in 81 patients under the age of 18 who all underwent stapes surgery. The mean age of surgery was 13. This study did include both otosclerosis and congenital fixation patients. Techniques varied from total stapedectomy to small fenestra laser stapedotomy. He defined increased hearing as a decrease of at least 10 dB in pure tone average and 15% improvement in discrimination scores. By this standard, 79% of primary cases in his study demonstrated improved postop hearing. In 1993, Dr. Teunissen and Dr. Cremers reported on a series of 144 ears from 117 patients with isolated congenital middle ear anomalies. Forty-four cases of class 1 congenital stapes footplate fixation were included. In this study, more than half of the patients with stapedial fixation also had associated incudomalleolar abnormalities. All patients were at least 10 years old at the time of stapedectomy. In his study, 49% of cases resulted in closure of the air-bone gap to less than 10 dB, and 22% closed to within 10-20 dB. Although the results of this series are somewhat less successful, the de la Cruz figures do reflect results for both otosclerosis and congenital fixation. Class 2 congenital anomalies are defined by stapedial fixation combined with anomalies of the malleus or incus. In the de la Cruz series, they found that 25% of congenital fixation cases had associated malleus or incus anomalies. The Teunissen and Cremers series included 55 cases of class 2 anomalies. In this series, more than half of the patients with stapedial fixation had associated incudomalleolar anomalies. The most common anomaly involved hypoplasia of the long process of the incus. Closure of the air-bone gap to less than 10 dB was only achieved in 40% of cases and 10-20 dB was achieved in 33%. The third class is congenital ossicular anomalies with a mobile footplate. Teunissen and Cremers described 27 cases of these class 3 anomalies. A syndrome was identified in 20% of the cases. The incus was the most commonly affected ossicle, and aplasia or dysplasia of the long process was the most common pathology. Ossicular chain reconstruction produced a hearing improvement of at least 15 dB in 12 of 19 patients with a mean gain of 25 dB. Dr. Myers found that fixation of the head of the malleus occurred in about 1 out of 100 ears explored for conductive hearing loss. He agreed that hypoplasia of the long or lenticular process is the most common defect found. The final class includes anomalies such as aplasia or severe dysplasia of the oval or round window. Again, Drs. Teunissen and Cremers describe 14 class 4 ears, ten with aplasia of the oval window, three with a crossing facial nerve, and one with a persistent stapedial artery. In their review of twelve cases of middle ear anomalies, Dr. Herman and Dr. Kimmilan describe five cases of oval window agenesis. All five were associated with severe anomalies of the stapes, and the authors chose not to attempt reconstruction in these cases. The de la Cruz series of pediatric stapedectomies included four absent oval windows. A persistent stapedial artery is another very rare cause of conductive hearing loss. This vessel develops during the fifth week while a stapes blastoma wraps around it, establishing the foramen. I would like to present two more studies before reviewing the Baylor data. The most recent study was done in 2002 by Dr. Raveh in Toronto. He reviewed charts of children seen between 1986 and 1996, and then he compiled the results of middle ear exploration in 67 patients with non-serous congenital conductive hearing loss. He found that 42 children had malformation of one or more ossicles without fixation of the stapes and 19 did have fixed stapes. Fifty percent of the patients who underwent reconstruction showed no significant benefit from surgery with postoperative air-bone gaps greater than 30 dB. Only 44% gained air-bone closure of at least 10 dB; and in 39% of cases, the surgeon decided not to perform surgical correction. In Glasscock’s study in 1983 of nine cases of non-serous congenital conductive hearing loss, only five of them, or 55%, had hearing improvement. Reviewing all the studies, it may appear that patients are not having significant postoperative improvement, but these two studies that I am about to review will show that objective measures alone may not accurately evaluate surgical outcomes. In 1999, Dr. Spurling evaluated the subjective and objective outcomes of surgical therapy in patients with congenital conductive hearing loss treated in adulthood. After surgical correction, the patients in this study had an average improvement of 18 dB in pure tone average and 16 dB in air-bone gaps, yet they still reported high satisfaction with overall improvement in their quality of life, perceived improvement in hearing, telephone use, and localization of sound. The patients reported that they felt less dependent on a hearing aid and they felt safer in their daily environment. In 2000, Drs. Stewart, Coker, Jenkins, and Mandolis performed a prospective longitudinal outcome based study of patients before and after treatment of conductive hearing loss. Eight-nine patients were included in the overall study population. Some were treated with hearing aids while others were treated with surgery. Overall, the hearing specific instrument did demonstrate significant improvement in emotional, social, and situational hearing status after treatment of their conductive hearing loss. This was a retrospective case study performed here at Baylor this year. We reviewed the charts of children seen by otologists during the past five years at Baylor. A total of 150 charts were reviewed at Methodist, Texas Children’s, and Ben Taub Hospitals. We excluded those cases where there was fluid in the middle ear, ossicular damage due to temporal bone trauma, cholesteatoma, and stenosis of the external auditory canal. We identified a total of 27 patients that we included in our study. Postoperative results are presented only for children who were followed for at least one year. The most recent audiogram was taken into account. Four-tone pure tone averages and air-bone gaps were calculated pre- and postoperatively. We reviewed all preoperative CT scans to see if we could predict the type of middle ear anomaly. We also measured one year postoperative air-bone gaps and individual gain as measured by the difference between the pre- and postoperative air-bone gaps. Four patients had associated syndromes. There were three patients with mixed loss. The age at time of surgery varied from seven to fifteen years with an average of twelve years. This graph depicts the most common anomalies found here during these middle ear explorations. Four anomalies were identified. Thirty percent of the cases were malleus fixation, and 30% were combined malleus incus abnormalities. Stapedial fixation and isolated incus abnormalities were both 20% of the cases. Overall, postoperative hearing results were mixed. Twenty-five percent had postoperative air-bone gaps of more than 30 dB. Only 50% of cases achieved a pure tone average of less than 30 dB while 55% of cases had an improvement in air-bone gap by 10 dB from preoperative levels. Cases of stapedial fixation had better results overall with 60% achieving a postoperative pure tone average of less than 30 dB and 60% improving by greater than 10 dB in postoperative air-bone gap. This graph depicts the postoperative results and divides them into the four different types of anomalies found. The first bar represents the preoperative pure tone average and the blue bar represents the postop results. You can see the most gain in pure tone average within the combined malleus incus abnormality group and the malleus group, but overall the absolute value of the pure tone average postoperatively was worse for the malleus group and the malleus incus group. We see similar results when we look at the pre- and postoperative air-bone gaps. The third bar represents the gain or the change between the preoperative and postoperative air-bone gaps. Postoperatively, the most gain in air-bone gap was in the malleus incus group and in the malleus group. Again though, the overall air-bone gap postoperatively was still worse in the malleus incus group and the malleus group. Twelve of the patients in this study had high resolution CT scans. We reviewed them and found that 25% showed inner ear anomalies such as enlarged vestibular aqueduct. On half of the studies, we were able to identify the specific ossicular abnormality that was later confirmed in surgery. These are some of the findings seen in the scans from our study. This CT shows malformed ossicles with normal inner ear structures; and on this next scan you can see how the head of the malleus is fixed to the anterior attic wall, which is bowed posteriorly. We concluded that there is diverse middle ear pathology, with the most common anomalies being malleus fixation and malleus incus anomalies. If we define a good result as pure tone average less than 30 or air-bone gap less than 20 postoperatively, surgery overall has mixed results with only 50% achieving objective benefit. The most gain in pure tone average and air-bone gap was in the group with the combined malleus incus anomaly, but overall the pure tone average and air-bone gap was best in the stapedial fixation group. Fifty percent of ossicular abnormalities were identified on preoperative CT scans. In conclusion, as otolaryngologists, we must watch carefully for patients with congenital conductive hearing loss. The history and physical exam are usually positive for non-progressive hearing loss and usually negative for recurrent otitis media. Syndromes should be ruled out and the options of hearing aid versus surgical correction should be discussed at length with the family, and if surgery is chosen it should be deferred until at least ages five through ten. There are mixed postoperative results in the literature and at Baylor, but it is important for us to know that quality of life for these children may still improve considerably after treatment. Case Presentation: He has had normal speech and language development. He was currently doing well in school in regular classes, with good grades and good attention in class. His past medical history was significant for childhood asthma that has now resolved. His prenatal and birth history were unremarkable. Family history was negative for hearing loss. Review of systems was negative for cardiac, renal, or other medical problems. On physical exam, his ear canal was patent and his tympanic membrane appeared normal. He had no syndromic features, abnormal facies, or developmental abnormalities. His hearing was tested using conventional behavioral audiometry. Consistent responses to air- and bone-conduction audiometry under insert earphones were observed at levels, indicating a moderate conductive hearing loss in the right ear and normal hearing in the left ear. Preoperative four-tone pure tone average in the right ear was 55, and air bone gap was 55. Acoustic immittance measures yielded a type Ad tympanogram in the right ear and a normal type A tympanogram in the left ear. Acoustic reflexes were absent in the right ear, and ipsilateral acoustic reflexes were present in the left ear. Preoperative CT scan did not show any inner ear or ossicular anomalies. Risks and options were presented to the family, and they opted for surgery. He was taken to the OR for middle ear exploration. In the OR, he was found to have an absent long process of the incus. The remainder of the ossicular chain was present and had intact mobility. A titanium incus prosthesis was placed, with good position. Postoperatively, he has done well. His two year postoperative results show a four-tone pure tone average of 20 and air bone gap of 20. Bibliography Battalglia A, McGrew BM, Jackson CG. Reconstruction of the entire ossicular conduction mechanism. Laryngoscope 2003;113:654-658. Bergstrom LB. Anomalies of the ear. Otolaryngology 1994;1:24-28. Boone R, Dornhoffer J. Stapedotomy above the facial nerve in a congenitally malformed ear: A case report. Otolaryngol Head Neck Surg 2002;127:342-345. Briggs, RJ, Luxford WM. Correction of conductive hearing loss in children. Otolaryngol Clin North Am 1994;27:607-620. De la Cruz A, Angeli S, Slattery WH. Stapedectomy in children. Otolaryngol Head Neck Surg 1999;120:487-492. De La Cruz A, Doyle KJ. Ossiculoplasty in congenital hearing loss. Otolaryngol Clin North Am 1994;27:799-811. Farrior JB. 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Subotic R, Mladina R, Risavi R. Congenital bony fixation of the malleus. Acta Otolaryngol 1998;118:833-836. Teunissen E, Cremers CWRJ, Huygen PLM. Isolated congenital stapes ankylosis: Surgical results in 32 ears and review of the literature. Laryngoscope 1990;100:1331-1336. Teunissen E, Cremers CWRJ. Classification of congenital middle ear anomalies: Report on 144 ears. Ann Otol Rhinol Laryngol 1993;102:606-612. Vincent R, Lopez A, Sperling NM. Malleus ankylosis: A clinical, audiometric, histologic, and surgical study of 123 cases. Am J Otol 1999;20:717-725. Wehrs RE. Congenital absence of the long process of the incus. Laryngoscope 1999;102:192-197. BCM Public | BCM Intranet | Privacy Notices | Contact BCM | BCM Site Map | ©2001-2005
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