Clinical Course of Pediatric Congenital Inner Ear Malformations

Transcription

1 The Laryngoscope Lippincott Williams & Wilkins, Inc., Philadelphia 2000 The American Laryngological, Rhinological and Otological Society, Inc. Clinical Course of Pediatric Congenital Inner Ear Malformations Albert H. Park, MD; Brenda Kou, MD; Andrew Hotaling, MD; Behrooz Azar-Kia, MD; John Leonetti, MD; Blake Papsin, MD Objective: To determine any factors that could improve the early detection and management of congenital inner ear malformations. Study Design: A retrospective review was performed of all patients with a diagnosis of inner ear malformation at Loyola University Medical Center (LUMC) and the Hospital for Sick Children (HSC) between 1987 and Clinical records and audiometric data were accumulated. One neuroradiologist reviewed every temporal bone computed tomography (CT) scan. Methods: Forty-six pediatric patients with congenital inner ear anomalies evaluated at two tertiary care hospitals. Results: The average patient age at initial assessment was 25.7 months. A family history of hearing loss was noted in only five patients (12.8%). A major nonotological deformity was seen in 41% of patients. The average hearing threshold was 88. All three patients with sudden hearing loss had vestibular aqueduct enlargement. Two of the three patients with common cavity anomalies had a history of recurrent meningitis. Twenty-seven patients had a vestibular aqueduct deformity, the most frequent radiographic abnormality in the series. Conclusions: Because inner ear malformation was diagnosed after 24 months of age in a significant percentage of patients, we recommend increased parental education and vigilance by primary care practitioners. Universal newborn screening may be the key to earlier detection of these infants. For children with idiopathic sensorineural hearing loss, we recommend a temporal bone CT scan. Patients with vestibular aqueduct enlargement must be counseled about the risk of progressive sensorineural hearing loss, meningitis, and the need to avoid contact sports. Patients with common cavity abnormalities should be considered for exploratory tympanotomy and also educated about the risk for meningitis. Key Words: Inner ear anomalies, Mondini, cochlear From the Departments of Otolaryngology Head and Neck Surgery (A.H.P., A.H., J.L.) and Radiology (B.A.-K.), Loyola University Medical Center, Maywood Illinois, and the Department of Otolaryngology (B.K., J.L.), Hospital for Sick Children, Toronto, Ontario. Editor s Note: This Manuscript was accepted for publication June 1, Send Correspondence to Albert H. Park, MD, Department of Otolaryngology Head and Neck Surgery, Loyola University Medical Center, 2160 South First Avenue, Maywood, IL 60153, U.S.A. hypoplasia, common cavity anomaly, vestibular aqueduct enlargement, sensorineural hearing loss. Laryngoscope, 110: , 2000 INTRODUCTION Approximately 20% of patients with congenital sensorineural hearing loss are found to have a radiologically proven inner ear anomaly. 1 Detection of these malformations is important, because recurrent meningitis or progressive sensorineural hearing loss with mild trauma develops in a minority of patients. These patients are advised to avoid contact sports, scuba diving, or other activities that may result in middle or inner ear pressure changes. Middle ear infections must be aggressively treated to avoid potential intracranial spread; early amplification is crucial for children with bilateral sensorineural hearing loss. The cost of temporal bone computed tomography (CT) scans and the frequent need to sedate a pediatric patient for radiological imaging have resulted in differing recommendations for the child with a sensorineural hearing loss. Recommendations have included a thorough workup for every child including a temporal bone CT scan to a scan only for those with a progressive hearing loss or with a history of recurrent meningitis. At the Hospital for Sick Children (HSC) (Toronto, Ontario, Canada) and at Loyola University Medical Center (LUMC) (Maywood, IL), a number of patients were found to have congenital inner ear malformations. Many patients were anecdotally noted to have other major nonotological anomalies or progressive sensorineural hearing loss. A review of these patients was performed to determine whether any clinical factors correlated with the presence of an inner ear malformation. MATERIALS AND METHODS A retrospective review of all patients who received diagnoses of inner ear malformation at LUMC and HSC between 1987 and 1995 was performed. Diagnoses were carried out at the hearing assessment clinic or in the hospital (e.g., for recurrent meningitis). Axial and coronal temporal bone CT scans were obtained for every patient. Scanners were set at 120 kv, 70 ma, with a slice thickness of 1.5 mm before 1996 and 1.0 mm after Sedation or general anesthesia was administered according to the institutional protocol when medical problems (e.g., craniofacial or neuromuscular disorders, young age or uncooperative 1715

2 patient) were present. Clinical records were obtained from the hearing assessment clinic and hospital. Audiometry was obtained via sound field testing or individual threshold testing or, when indicated, via auditory brainstem response testing. One neuroradiologist diagnosed an inner ear anomaly based on temporal bone CT scans. A malformation was present if one or more dysmorphological features were seen involving the internal auditory canal, vestibular aqueduct, cochlea, vestibule, or semicircular canals. Clinic data and CT findings were tabulated into an EXCEL spreadsheet (Microsoft, Redmond, WA). RESULTS Inner ear anomaly was diagnosed in 46 pediatric patients at LUMC and HSC. This population of patients made up 21% of all patients seen for idiopathic sensorineural hearing loss at the hearing assessment clinics. The average age at initial assessment was 25.7 months (range, 7 mo 7 y). Fifteen patients (36%) were older than 24 months at initial assessment. Thirteen of these 15 patients presented with either a hearing loss or speech delay or failed a hearing test. One of these patients presented with an abnormal audiogram after the insertion of tympanostomy tubes. Two of the 15 patients did not present with a delayed diagnosis. One patient presented with an acute sensorineural hearing loss after falling and hitting her head. Another patient presented with recurrent meningitis. Six of the 13 patients (46%) with hearing loss or speech delay had a loss of 55 or less in one ear. As shown in Table I, the chief presenting complaint for all the patients was hearing related, although a few patients presented with recurrent meningitis. A family history of hearing loss was noted in only five patients (12.8%). Only one patient had a relative with a known inner ear malformation. A major nonotological anomaly was seen in 17 patients (41%). Anomalies are shown in Table II and included hypotonia, congenital torticollis, Pierre Robin sequence, and failure to thrive. The cochlea was involved in 24 patients (56%); 19 patients had a noncochlear anomaly involving the semicircular canals, vestibule, or vestibular aqueduct, or a combination of these. Radiographic information for three patients was unknown. A bilateral inner ear anomaly was seen in 25 patients (58%); a unilateral anomaly was detected in 8 patients (19%). A mixed anomaly such as a cochlear hypoplasia with a contralateral vestibular aqueduct enlargement was seen in 10 patients (23%). TABLE I. Chief Presenting Complaint at Initial Assessment (N 46 patients). Presenting Complaint Patients (n) Hearing loss 31 Failed hearing test 2 Speech delay 10 Otitis media 5 Recurrent meningitis 2 Multiple dysmorphic features 1 Number of patients totals more than 46 because several patients had more than one presenting complaint. TABLE II. Nonotologic Disorders Seen in Patients With Congenital Inner Ear Malformations (N 46 patients). Nonotologic Disorder Patients (n) Hypotonia 4 Congenital torticollis 2 Pierre Robin sequence 2 Failure to thrive 2 Ambiguous genitalia 2 Other 14 Other includes Hirschsprung s disease, Down syndrome, ventricular septal defect, polycystic kidney disease, growth hormone deficiency, hypertension, preauricular sinus, congenital dislocated hip, spina bifida, agenesis corpus callosum, seizure disorder, Johanson-Blizzard syndrome (aplasia nasal ala, lower lid colobomas, imperforate anus, rectovaginal fistula, left uterocele, secundum atrial septal defect, pancreatic insufficiency), Duane s syndrome (left lateral rectus palsy), dysmorphic (unspecified), optic hypoplasia, right ureteric reflux, microanus, ankyloglossia, tracheomalacia. Each condition in the other category involved only one patient. The most common cochlear anomaly was cochlear hypoplasia (36%), followed by incomplete partition (31%) and common cavity (13%) (Fig. 1A C). Table III illustrates the frequency of each cochlear anomaly. Two patients had complete labyrinthine aplasia. Five patients had internal auditory canal malformations; the most frequent deformity was hypoplasia (Fig. 2). Vestibular anomalies were seen in 12 patients. The two most frequently observed malformations included enlargement and abnormal shape (Fig. 3). Twenty-seven patients had a vestibular aqueduct deformity, the most frequent radiographic abnormality in our series. A vestibular aqueduct anomaly was recorded when the axial section illustrated a diameter greater than 2 mm or an abnormal shape. The diameter of the facial nerve, which is about 2 mm and is evident on the same axial section) is a good subjective measure for vestibular aqueduct enlargement (Fig. 4). The most commonly seen malformations included cone- or parallel-shaped vestibular aqueduct (Figs. 4 and 5). Three patients had an abnormal vestibular aqueduct that did not fit into the cone- or parallel-shaped classification (Fig. 3). Hearing assessment was based on sound field testing, individual threshold levels, or auditory brainstem response testing. Thirty-six patients had individual threshold testing or auditory brainstem response testing; five patients had only sound field thresholds documented. No response results were arbitrarily set at 120. The average hearing threshold was 88 (range, normal to no response), which was based on speech reception thresholds (average of results at 500, 1000, and 2000 Hz). The average hearing loss was 12 (range, 0 35 ) over an average follow-up period of 2.7 years (range, 2 mo 12 y). Three patients (7%) had bilateral total deafness at initial presentation; no patient progressed to deafness. No data were obtained on high-frequency thresholds. Seven of eight patients with a unilateral inner ear malformation had evidence of hearing loss in the contralateral ear. One patient with a unilateral common cavity deformity and deafness had normal contralateral hearing. The degree of hearing loss in six patients was greater 1716

3 Fig. 1. Coronal temporal bone sections. A. Cochlear hypoplasia (black arrow). B. Incomplete partition (black arrow). Note the greater number of turns compared with cochlear hypoplasia. C. A common cavity anomaly (black arrow). Note the absent cochlear turns. than 30. Only one patient with bilateral radiographically confirmed inner ear anomalies had normal hearing in one ear. This patient presented with a unilateral 40- conductive hearing loss and had a bilateral cone-shaped vestibular aqueduct enlargement. Data for each inner ear anomaly and the corresponding hearing threshold are shown in Table IV. There was no correlation between the degree of hearing loss and the severity of cochlear malformation. Patients with an incomplete partition had a worse average hearing threshold than those with cochlear hypoplasia. Patients with a common cavity malformation had a worse average hearing threshold than those with labyrinthine aplasia. A potential confounding factor was the presence of multiple abnormal inner ear structures. Fourteen of 18 patients with malformed vestibules had another abnormal inner ear structure. Twenty-five of 31 patients with cochlear anomalies had a concomitant abnormal inner ear. A few clinical patterns were recognized in the patient series. Three patients presented with sudden hearing loss following trauma. Two of these patients experienced the loss following mild trauma. All three patients had vestibular aqueduct enlargement. Four patients had a history of meningitis. In one child with bilateral vestibular aqueduct enlargement meningitis developed after bilateral tympanostomy tube insertion. A subsequent exploratory tympanotomy revealed a round window perilymphatic fistula, which was then plugged. He had done well after 10 years of follow-up. Another child with incomplete cochlear partition and vestibular aqueduct enlargement also had a history of meningitis. The scans could not be found to verify the inner ear anomaly. Two children had recurrent meningitis and common cavity anomalies. Both required mastoid and middle ear cavity obliteration to seal perilymphatic fistulas. DISCUSSION The role of a temporal bone CT scan in the evaluation of a child with sensorineural hearing loss is controversial. Temporal bone CT scans are expensive and place a child at risk when sedation or general anesthesia is used. An unrecognized inner ear anomaly is also very costly. In a minority of patients life-threatening meningitis or progressive sensorineural hearing loss develops. 2 4 The motivation of this study was to determine any clinical factors that may provide early diagnosis and reduce the number of temporal bone CT scans. One major finding from our review was the average late age at presentation. The average patient age at initial assessment in our series was 25.7 months, a result similar to the average identification of hearing loss in the United States. 5,6 In 12 of the 15 patients who were older than 24 months at initial assessment diagnosis could have been performed with sound field testing, otoacoustic emissions testing, or automated auditory brainstem response testing. As shown in Table I, 24% of the patients already had speech delay at initial assessment. TABLE III. Frequency of Cochlear Anomalies by Type (N 24 Patients With 39 Ears Involved). Cochlear Type Ears n (%) Incomplete partition 12 (31) Common cavity 5 (13) Cochlear hypoplasia 14 (36) Cochlear aplasia 4 (10) Michel (complete labyrinthine aplasia) 4 (10) Percentage is calculated based on the total number of abnormal cochlear ears (39 ears). Fig. 2. Axial temporal bone computed tomography (CT) section. Left-side internal auditory canal hypoplasia (white arrow). 1717

4 Fig. 3. Axial temporal bone CT section. An enlarged, abnormally shaped right-side vestibule (black arrow). The white arrow indicates an abnormal vestibular aqueduct that does not fit into the cone or parallel classification. Parameters commonly associated with an increased risk for hearing loss were not found to be sensitive enough to be clinically useful. A family history of childhood hearing loss, perinatal infections, low birth weight, hyperbilirubinemia, birth asphyxia, or meningitis was found in only a few patients. Forty-one percent of patients did have nonotological anomalies such as hypotonia and failure to thrive. Twenty-nine patients (59%), however, would have been missed if nonotological anomalies alone were used as a screening measure. The existence of a progressive, fluctuating, or asymmetrical sensorineural hearing loss has been advocated as an indication for obtaining a temporal bone CT scan. 7 In our series, only a minority of patients presented in this fashion. A progressive sensorineural hearing loss developed in three patients. No patients had a fluctuating hearing loss. Only three patients had an asymmetrical sensorineural hearing loss. Fig. 4. Axial temporal bone CT section. An enlarged vestibular aqueduct (cone-shaped, white arrow). The facial nerve diameter is a good subjective comparison for vestibular aqueduct size (black arrow). Fig. 5. Axial temporal bone CT section. A parallel-shaped vestibular aqueduct (white arrow). The patients with progressive sensorineural hearing loss or meningitis did have characteristic CT scan findings: either a vestibular aqueduct or common cavity malformation. Two of the three patients with a common cavity anomaly had a history of recurrent meningitis and required surgical closure of a perilymphatic fistula. A number of authors have also commented on the relationship between recurrent meningitis and cochlear dysplasia For example, Phelps and Michaels 11 noted two cases of recurrent meningitis and common cavity anomalies. In our series, 2 of the 28 patients with a vestibular aqueduct enlargement had a history of meningitis. Only one patient required surgical closure of a perilymphatic fistula. In addition, all three patients with progressive or sudden sensorineural hearing loss had vestibular aqueduct enlargement. Anomaly TABLE IV. Hearing Threshold () According to Jackler et. al Cochlea involved Labyrinthine aplasia 2 2 Common cavity 5 Cochlear aplasia 1 Cochlear hypoplasia Incomplete partition Cochlea not involved Vestibule 2 2 enlarged Vestibular aqueduct Internal auditory canal

5 Thus a temporal bone CT scan is currently the only study sensitive enough to detect a congenital inner ear malformation. Harcourt et al. 12 have described the use of a screening CT scan to evaluate idiopathic bilateral sensorineural hearing loss in older patients. Two protocols were used, one involving 1-mm axial sections through the otic capsule and the other involving 10 to mm cuts both axial and coronal through the otic capsule. Limited sections may be an option to minimize cost and scan time. CONCLUSION From the results of this study the following recommendations can be made. Because a significant percentage of our patients with inner ear malformation received their diagnosis after age 24 months, parental education and continued vigilance by the primary care practitioner are crucial for early detection. Universal newborn screening may be the key to early detection of infants with these anomalies. 13,14 The consequences of late detection include speech delay and, for a minority of patients with inner ear malformations, progressive hearing loss and life-threatening meningitis. For children with idiopathic sensorineural hearing loss, we recommend a temporal bone CT scan. Twenty-one percent of patients with a sensorineural hearing loss at our clinics had an inner ear anomaly. Patients with vestibular aqueduct enlargement must be counseled about the risk of progressive sensorineural hearing loss and the risk of meningitis from contact sports or activities that may affect inner and middle ear pressures. Patients with common cavity abnormalities have a high incidence of recurrent meningitis and perilymphatic fistula. These patients should be considered for an exploratory tympanotomy, educated about the risks of meningitis, and also counseled to avoid contact sports and activities that may affect inner and middle ear pressures. Auditory amplification should be instituted promptly in all patients with bilateral sensorineural hearing loss. Cochlear implantation has been performed successfully in patients with cochlear anomalies, but at least one case of meningitis has occurred after implantation. 15 ACKNOWLEDGMENT We would like to acknowledge William Crysdale, MD, Vito Forte, MD, the audiology departments at LUMC and HSC, and Susan Lance, RN. BIBLIOGRAPHY 1. Jackler RK, Luxford WM, House WF. Congenital malformations of the inner ear: a classification based on embryogenesis. Laryngoscope 1987;97(2, Suppl 40): Phelps PD, Lloyd GS. Congenital deformity of the internal auditory meatus and labyrinth associated with cerebrospinal fluid fistula. Adv Otorhinolaryngol 1978;24: Bridger AWM, Phelps PD. Recurrent meningitis due to congenital malformation of the inner ear. BMJ 1983;286: Ohlms LA, Edwards MS, Mason EO, Igarashi M, Alford BR, Smith RJ. Recurrent meningitis and Mondini dysplasia. Arch Otolaryngol Head Neck Surg 1990;116: United States Maternal and Child Health Bureau. Healthy Children 2000: National Health Promotion and Disease Prevention Objectives Related to Mothers, Infants, Children, Adolescents and Youth. Washington, DC: Department of Health and Human Services, Publication 177, HRSA-M-CH Stein LK, Jabaley T, Spitz R, Stoakley D, McGee T. The hearing-impaired infant: patterns of identification and habilitation revisited. Ear Hear 1990;11: Chan KH. Sensorineural hearing loss in children. Otolaryngol Clin North Am 1994;27(3): Phelps PD. Cochlear implants for congenital deformities. J Laryngol Otol 1992;106: Phelps PD, Proops D, Sellars S, Evans J, Michaels L. Congenital cerebrospinal fluid fistula through inner ear and meningitis. J Laryngol Otol 1993;107: Phelps PD, Hoyd GA. Mondini dysplasia is not associated with meningitis and cerebrospinal fluid fistula. Arch Otolaryngol Head Neck Surg 1991;117: Phelps PD, Michaels L. The common cavity congenital deformity of the inner ear. Otorhinolaryngology 1995;57: Harcourt JP, Lennox P, Phelps PD, Brookes GB. CT screening for temporal bone abnormalities in idiopathic bilateral sensorineural hearing loss. J Laryngol Otol 1997;111: Mehl AL, Thomson V. Newborn hearing screening: the great omission. Pediatrics 1998;101(1): Comment on the Joint Committee Statement. Otolaryngol Head Neck Surg 1995;113(3): Page EL, Eby TL. Meningitis after cochlear implantation in Mondini malformation. Otolaryngol Head Neck Surg 1997; 116(1):