The Role of Motion Sensitivity and Headaches on Vestibular Rehabilitation Outcomes in Pediatric Vestibular Migraines

OBJECTIVE

To determine the utility of the motion sensitivity quotient (MSQ) in diagnosing pediatric vestibular migraine (VM) and to characterize the role of motion sensitivity and headache control on vestibular rehabilitation (VR) outcomes in pediatric VM.

STUDY DESIGN

Retrospective cohort analysis.

SETTING

Pediatric tertiary referral center.

PATIENTS

Children (≤18 years old) with dizziness who completed vestibular testing from January 2016 to August 2022, diagnosed with either VM or another vestibular disorder.

INTERVENTIONS

VR, which included MSQ testing.

MAIN OUTCOME MEASURES

Initial MSQ, number and duration of vestibular physical therapy (PT) sessions, PT goals met, and posttreatment MSQ.

RESULTS

Two hundred fifty-seven patients met study criteria. MSQ was not a reliable diagnostic marker in pediatric VM as there was no difference in initial MSQ between VM and non-VM patients (9.4 vs. 7.8 in non-VM, p = 0.014). Both VM (n = 116) and non-VM (n = 141) patients demonstrated significant improvement in MSQ after VR (p = 0.004). However, VM patients tended to be less likely to meet at least one PT goal (60 vs. 77% in non-VM, p = 0.016, d = 0.37), although not significant. VM patients with more frequent headaches had significantly higher initial MSQ (p = 0.008). VM patients with more frequent headaches or higher initial MSQ tended to require increased number and longer duration of VR (small/medium effect size although not statistically significant after Bonferroni correction).

CONCLUSION

VR is an effective treatment for both VM and non-VM pediatric patients. VM patients, especially those with severe motion sensitivity or poorly controlled headaches, may be less responsive to VR and may require increased frequency and duration of VR. Our findings propose the importance of counseling pediatric patients with severe motion sensitivity or uncontrolled migraines regarding realistic expectations of their VR course.

The Girl With the Bleeding Earlobe Mass

ABSTRACT

Pilomatrixomas, also known as epithelioma calcificans, are benign tumors of hair follicle matrix cells that are often mistaken for other lesions, especially cutaneous abscesses. We report an illustrative case in which a teenage girl developed a red, swollen earlobe that required multiple care visits and interventions until definitive diagnosis and treatment were provided. Although the lesion was initially treated as an abscess, it continued to progress in size and discomfort. The correct diagnosis was established after imaging and complete excision with pathologic examination. Ultimately, our patient was subjected to avoidable procedures that carried the risk of potentially negative cosmetic sequelae before the proper intervention. Although abscesses are common, it is important for clinicians to avoid incision and drainage of lesions, unless the diagnosis is certain.

Socioeconomic Disparities in Pediatric Single-Sided Deafness

OBJECTIVE

To explore socioeconomic disparities in pediatric single-sided deafness (SSD) treatment.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral academic center.

METHODS

The charts of 190 pediatric patients with SSD were reviewed for demographic and clinical characteristics. Socioeconomic variables included race and insurance status. ZIP codes were used to obtain additional socioeconomic data from the American Community Survey, including mean and median income, percentage of families below the poverty level, and employment status. Socioeconomic status (SES) was classified by insurance status and income. Treatment outcomes were analyzed by socioeconomic variables.

RESULTS

There were 105 males and 85 females with a mean follow-up of 55.2 months and a mean age at diagnosis of 4.4 years. Sixty-three percent of children received treatment at last follow-up. Thirty-five percent of children had public insurance and 65% had private insurance. Treatment rates were similar in the private and public insurance groups (60.6% vs 66.7%, P = .42), but device type was different between groups (P = .02). Consistent device use was associated with private insurance (47.5% vs 38.9%, P = .003) and high SES (94.4% vs 80%, P = .04) on univariate but not on multivariate analysis. Aided audiometry results were similar between SES groups. No association was found between sex, race, income level, poverty level, or employment status and treatment outcomes.

CONCLUSION

Insurance type and SES were not associated with SSD treatment outcomes in children, although device use may be higher in children with private insurance and higher SES. Further research should focus on strategies to reduce barriers to treatment and improve adherence.

Ocular Vestibular Evoked Myogenic Potentials: Normative Findings in Children

BACKGROUND

To add to the limited body of literature on ocular vestibular evoked myogenic potential (oVEMP) responses in children and to assess a different montage for oVEMP recording.

PURPOSE

To evaluate the characteristics of the oVEMP response in children and compare the results with that of a group of healthy adults.

RESEARCH DESIGN

Prospective descriptive study from a tertiary referral center.

STUDY SAMPLE

Twenty-two children (mean age = 6.3 yr, standard deviation = ±1.5, range = 3.5-8.9 yr) were recruited from families whose parent(s) were employed by the Cincinnati Children's Hospital Medical Center (CCHMC). Pediatric participants were categorized by age into three groups for data analysis. The comparison adult group of ten participants were members of the employee staff at CCHMC.

DATA COLLECTION AND ANALYSIS

Audiometric assessment was completed in all participants. The latency, amplitude, and threshold of the oVEMP responses were recorded using a modified electrode montage with reference at the chin and compared between the pediatric and adult participants.

RESULTS

All participants completed testing and had bilateral measurable oVEMP responses using a 105-dB nHL, 500-Hz tone burst stimulus. Comparison between right and left ears across all participants for each oVEMP characteristic found no statistically significant difference. oVEMP testing showed no significant differences with respect to latency, amplitude, interaural amplitude asymmetry, and threshold of response as a function of age.

CONCLUSIONS

oVEMP responses for ages ≥3 did not differ from responses in adults.

Imaging findings in pediatric single-sided deafness and asymmetric hearing loss

OBJECTIVE

To examine the imaging findings on computer tomography (CT) and magnetic resonance imaging (MRI) in pediatric single-sided deafness (SSD) and asymmetric hearing loss (ASH).

METHODS

The medical records of 189 pediatric patients with SSD and ASH were retrospectively reviewed, and imaging findings were compared. SSD was defined as unilateral profound hearing loss and contralateral normal hearing ear. In the ASH group, ASHw was defined as the worse hearing ear with profound hearing loss, while ASHb was defined as the better hearing ear with mild-moderate hearing loss.

RESULTS

There were 170 patients with SSD and 19 patients with ASH. In the SSD group, 83 patients (48.8%) had imaging findings associated with hearing loss. In the ASH group, such imaging findings were found in six (31.6%) of the ASHw and in five (26.3%) of the ASHb ears. The most common finding in the SSD group was cochlear nerve deficiency (50.6%), followed by cochlear dysplasia (39.8%) and enlarged vestibular aqueduct (26.5%). In the ASH groups, cochlear dysplasia was seen in three (50%) of ASHw ears and in two (40%) of the ASHb ears, and enlarged vestibular aqueduct was seen in three (50%) of ASHw ears and in two (40%) of the ASHb ears.

CONCLUSION

Imaging studies identified the etiology in half of the cases of SSD and in one-third of ASH patients. Our findings strongly support the use of imaging studies in the evaluation of pediatric SSD and ASH.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:1007-1010, 2020.

Bacterial Tracheitis Reexamined: Is There a Less Severe Manifestation?

OBJECTIVE: Bacterial tracheitis (BT) is a condition that can cause fatal airway obstruction. We evaluated our experience with BT over a 10-year period.

STUDY DESIGN: Retrospective review of patients treated for BT between 1991 and 2001. RESULTS: Ninety-four cases were evaluated. The mean patient age was 7.9 years. At presentation, 60% were afebrile, and the mean WBC count was 10.8 × 103/mm3. Only 53% of patients required intubation. Younger children were more likely to require this intervention. S. aureus was the most commonly cultured bacteria, while isolation of M. catarrhalis was associated with a higher intubation rate. A pathologic virus was isolated in 64% of the 34 cultures performed. Only 9 patients were described as “toxic,” and 6 presented in respiratory extremis. There were no deaths.

CONCLUSION AND SIGNIFICANCE: A subset of patients with tracheal membranes has a less severe clinical appearance. Nonetheless, these patients require debridement and aggressive medical treatment. We propose that the term “exudative tracheitis” (ET) better describes this entity. Older patients who are less systemically ill and rapidly respond to local and systemic therapy are characteristic of ET. EBM rating: C.

Vestibular pathology in children with enlarged vestibular aqueduct

OBJECTIVES/HYPOTHESIS

To establish the prevalence of abnormal vestibular test findings in children with enlarged vestibular aqueduct (EVA) and determine if these findings correlate with clinical symptoms, radiographic findings (EVA size and laterality), audiometric findings, and genetic testing in these patients.

STUDY DESIGN

Prospective cohort.

METHODS

Patients 3 to 12 years of age with hearing loss and imaging findings consistent with EVA treated at our tertiary care institution were sequentially enrolled from 2009 to 2011. The following six outcome measurements were analyzed: audiometric findings, EVA laterality, temporal bone measurements, genetic testing, vestibular testing (cervical-evoked myogenic potentials, posturography, rotational chair, and calorics), and vestibular symptoms.

RESULTS

Twenty-seven patients with EVA (mean age 9.2 years, 48% female) were enrolled in and completed the study. Vertigo was reported in six patients. Twenty-four of 27 (89%) had at least one abnormal vestibular test result. Midpoint and operculum size correlated with directional preponderance (P = .042 and P = .032, respectively). Also, high-frequency pure tone average (HFPTA) correlated with unilateral weakness (P = .002). Walking at a later age correlated with abnormal posturography results. There was no correlation between EVA laterality and vestibular test findings.

CONCLUSION

We found a high rate of vestibular pathology in children with EVA; however, the prevalence of abnormal vestibular test findings in this patient population was not correlated with vestibular symptoms. Enlarged vestibular aqueduct size, HFPTA, and walking at a later age were correlated with abnormal vestibular test findings. In view of these results, it may be prudent to consider vestibular testing in children with these clinical characteristics.

LEVEL OF EVIDENCE

2b. Laryngoscope, 126:2344-2350, 2016.

High-frequency sensorineural hearing loss in children

OBJECTIVES/HYPOTHESIS

Determine the prevalence of high-frequency sensorineural hearing loss (HFSNHL) in our hearing loss population and a diagnostic algorithm for these patients.

STUDY DESIGN

Retrospective case series.

METHODS

We identified patients diagnosed with sensorineural hearing loss (SNHL) at our pediatric tertiary care institution from 1981 to 2010. Based on audiometric profiles, these patients were subdivided into those with a flat SNHL configuration and those with HFSNHL. Imaging and genetic testing data and data regarding age at diagnosis, laterality, and risk factors were obtained for both groups. Comparisons were then made between the two groups.

RESULTS

Of 2,867 patients included in the study, 7.6% had HFSNHL. Age at diagnosis was significantly higher in HFSNHL patients (8.3 years vs. 6.1 years; P < .0001). These patients also had a significantly higher proportion of unilateral versus bilateral loss (49.1% vs. 26.1%; P < .0001); unilateral losses were also less severe. Genetic testing showed no significant difference between groups in the proportion of patients tested or in those who tested positive. Similarly, imaging data revealed no difference in the proportion of patients tested in the two groups; however, overall diagnostic yield was significantly higher in flat SNHL patients (29.5% vs.17.3; P = .02).

CONCLUSIONS

The positive predictive value of simple genetic testing is similar to that of imaging studies. However, given cost differences between genetic testing and imaging, it is prudent to perform genetic testing as the initial diagnostic test. Determination of whether high-throughput, multigene diagnostic platforms offer an added benefit in the evaluation of children requires further study.

LEVEL OF EVIDENCE

4. Laryngoscope, 126:1236-1240, 2016.

Molecular genetics of MARVELD2 and clinical phenotype in Pakistani and Slovak families segregating DFNB49 hearing loss

Pathogenic mutations of MARVELD2, encoding tricellulin, a tricelluar tight junction protein, cause autosomal recessive non-syndromic hearing loss (DFNB49) in families of Pakistan and Czech Roma origin. In fact, they are a significant cause of prelingual hearing loss in the Czech Roma, second only to GJB2 variants. Previously, we reported that mice homozygous for p.Arg497* variant of Marveld2 had a broad phenotypic spectrum, where defects were observed in the inner ear, heart, mandibular salivary gland, thyroid gland and olfactory epithelium. The current study describes the types and frequencies of MARVELD2 alleles and clinically reexamines members of DFNB49 families. We found that MARVELD2 variants are responsible for about 1.5 % (95 % CI 0.8-2.6) of non-syndromic hearing loss in our cohort of 800 Pakistani families. The c.1331+2T>C allele is recurrent. In addition, we identified a novel large deletion in a single family, which appears to have resulted from non-allelic homologous recombination between two similar Alu short interspersed elements. Finally, we observed no other clinical manifestations co-segregating with hearing loss in DFNB49 human families, and hypothesize that the additional abnormalities in the Marveld2 mutant mouse indicates a critical non-redundant function for tricellulin in other organ systems.

Codeine-related adverse drug reactions in children following tonsillectomy: a prospective study

OBJECTIVES/HYPOTHESIS

To prospectively determine factors associated with codeine's adverse drug reactions (ADRs) at home in a large homogenous population of children undergoing outpatient tonsillectomy.

STUDY DESIGN

Prospective, genotype blinded, observational study with a single group and repeated ADR measures documented by parents at home.

METHODS

A total of 249 children 6 to 15 years of age scheduled for tonsillectomy were enrolled. The primary outcome was number of daily codeine-related ADRs. We examined the number and type of ADR by race and by days and further modeled factors potentially associated with ADR risk in a subcohort of white children. Sedation following a dose of codeine was a secondary outcome measure. Parents recorded their children's daily ADRs and sedation scores during postoperative days (POD) 0 to 3 at home.

RESULTS

Diaries were returned for 134 children, who were given codeine. A total of 106 (79%) reported at least one ADR. The most common ADRs were nausea, lightheadedness/dizziness for white children and nausea, and vomiting for African American children. In a subcohort of white children ≤ 45 kg, increased ADR risk was associated with the presence of one or more full function CYP2D6 alleles (P < 0.001), POD (P < 0.001), and sex (P = 0.027). Increased pain intensity (P = 0.009) and PODs 0 and 1 (P = 0.001) contributed to a higher sedation risk. Neither obstructive apnea nor predicted CYP2D6 phenotype were associated with sedation risk.

CONCLUSIONS

Our results provide evidence that multiple factors are associated with codeine-related ADRs and support the FDA recommendation to avoid codeine's routine use following tonsillectomy in children.

Genetic analysis through OtoSeq of Pakistani families segregating prelingual hearing loss

OBJECTIVE

To identify the genetic cause of prelingual sensorineural hearing loss in Pakistani families using a next-generation sequencing (NGS)-based mutation screening test named OtoSeq.

STUDY DESIGN

Prospective study.

SETTING

Research laboratory.

SUBJECTS AND METHODS

We used 3 fluorescently labeled short tandem repeat (STR) markers for each of the known autosomal recessive nonsyndromic (DFNB) and Usher syndrome (USH) locus to perform a linkage analysis of 243 multigenerational Pakistani families segregating prelingual hearing loss. After genotyping, we focused on 34 families with potential linkage to MYO7A, CDH23, and SLC26A4. We screened affected individuals from a subset of these families using the OtoSeq platform to identify underlying genetic variants. Sanger sequencing was performed to confirm and study the segregation of mutations in other family members. For novel mutations, normal hearing individuals from ethnically matched backgrounds were also tested.

RESULTS

Hearing loss was found to co-segregate with locus-specific STR markers for MYO7A in 32 families, CDH23 in 1 family, and SLC26A4 in 1 family. Using the OtoSeq platform, a microdroplet PCR-based enrichment followed by NGS, we identified mutations in 28 of the 34 families including 11 novel mutations. Sanger sequencing of these mutations showed 100% concordance with NGS data and co-segregation of the mutant alleles with the hearing loss phenotype in the respective families.

CONCLUSION

Using NGS-based platforms like OtoSeq in families segregating hearing loss will contribute to the identification of common and population-specific mutations, early diagnosis, genetic counseling, and molecular epidemiology.

Performance evaluation of the next-generation sequencing approach for molecular diagnosis of hereditary hearing loss

OBJECTIVE

To evaluate the performance of a next-generation sequencing (NGS)-based targeted resequencing genetic test, OtoSeq, to identify the sequence variants in the genes causing sensorineural hearing loss (SNHL).

STUDY DESIGN

Retrospective study.

SETTING

Tertiary children's hospital.

SUBJECTS AND METHODS

A total of 8 individuals presenting with prelingual hearing loss were used in this study. The coding and flanking intronic regions of 24 well-studied SNHL genes were enriched using microdroplet polymerase chain reaction and sequenced on an Illumina HiSeq 2000 sequencer. The filtered high-quality sequence reads were mapped to reference sequence, and variants were detected using NextGENe software.

RESULTS

A total of 1148 sequence variants were detected in 8 samples in 24 genes. Using in-house developed NGS data analysis criteria, we classified 810 (~71%) of these variants as potential true variants that include previously detected pathogenic mutations in 5 patients. To validate our strategy, we Sanger sequenced the target regions of 5 of the 24 genes, accounting for about 29.2% of all target sequence. Our results showed >99.99% concordance between NGS and Sanger sequencing in these 5 genes, resulting in an analytical sensitivity and specificity of 100% and 99.997%, respectively. We were able to successfully detect single base substitutions, small deletions, and insertions of up to 22 nucleotides.

CONCLUSION

This study demonstrated that our NGS-based mutation screening strategy is highly sensitive and specific in detecting sequence variants in the SNHL genes. Therefore, we propose that this NGS-based targeted sequencing method would be an alternative to current technologies for identifying the multiple genetic causes of SNHL.

Unilateral Enlarged Vestibular Aqueduct in Children

Objective: 1) Describe the likelihood of contralateral hearing loss (HL) in patients with unilateral enlarged vestibular aqueduct (UEVA). 2) Detemine the positve predictive value of genetic testing in patients with UEVA. 3) Determine the correlation of temporal bone measurements in patients with UEVA.

Method: Patients were identified from a database of children with sensorineural hearing loss (HL) and enlarged vestibular aqueduct (EVA) between 1998 and 2010. A group of patients with unilateral HL without EVA was also identified. Outcomes measured were HL phenotype, laterality of EVA, midpoint and operculum measurements, and genetic tests.

Results: Fifty-five percent of patients with UEVA had HL in the contralateral ear. There was no difference in the rate of HL progression in patients with bilateral and unilateral EVA ( P = .1). However, both EVA groups had higher rates of progression compared to patients with unilateral HL alone. A correlation was shown for the presence of HL at 250 Hz and the risk of more severe HL and progressive HL. Patients with bilateral EVA and SLC26A4 mutations had a higher rate of progression than patients who had no mutations ( P = .02). No patients with UEVA had Pendred syndrome.

Conclusion: Children with unilateral EVA have a significant risk of HL progression. Hearing loss in the contralateral ear is common, suggesting that unilateral EVA is a bilateral process. Temporal bone measurements, HL severity, and HL at 250 Hz were correlated with the risk of progressive HL.

Minimal access and standard cochlear implantation: a comparative study

OBJECTIVE

To compare the operative times and complications between patients who underwent minimal access cochlear implantation and standard technique cochlear implantation.

METHODS

Patients who underwent unilateral cochlear implantation by a single surgeon from 2001 to 2010. The minimal access technique of an approximately 2.5-3 cm post-auricular incision with creation of subperiosteal pocket for the device was compared to the longer standard "S" incision into the scalp (~8-10 cm) with bone well creation and suture fixation. Outcomes include operative times and complications.

RESULTS

There were 122 unilateral implants, 73 (59.8%) in the minimal access group and 49 (40.2%) in the standard group. Mean total time in the operating room was lower in the minimal access group compared to the standard group (200±31 vs. 255±49 min, p<.0001) as well as mean operative time (149.5±28 vs. 200±45 min, p<.0001 respectively). There were 17 complications in the entire cohort with 8 and 9 complications in the minimal and standard groups respectively. Of the 17 complications, 12 were surgical technique-specific. Although it appeared that there were higher rates of major, technique-specific, and overall complications in the standard access group, these differences did not reach statistical significance.

CONCLUSIONS

Patients undergoing minimal access cochlear implantation require shorter operative times when compared to the standard access cochlear implantation. In addition, low complication rates are observed for major, technique-specific, and overall complications. Minimal access cochlear implantation may be considered an equivalent and potentially superior technique.

The Use of Next-Generation Sequencing for Hearing Loss

Objective: Recently, next-generation sequencing (NGS) technology has emerged as a possible revolutionary force changing the paradigm of molecular diagnosis by offering high-throughput sequencing. In the present study, we have evaluated the performance of NGS to identify the sequence variants in a panel of 24 genes associated with hereditary hearing loss.

Method: The coding and flanking intronic regions covering 177 kb target sequence were enriched using microdroplet PCR from 8 samples and sequenced in a single lane on Illumina HiSeq 2000 instrument. The quality filtered sequence reads were mapped to the human reference sequence. The sequence variants were evaluated using novel pathogenecity filter.

Results: Of the 1148 variants detected in all 8 samples, 810 (71%) were classified as true variants using our filtering criteria. To validate our strategy, we Sanger sequenced regions of 4/24 genes, accounting for about 25% of all target sequences. Of the 373 variants detected in these 4 genes, we classified 265 variants as potentially true using our filtering criteria. We were able to detect 259 variants found on sequencing, including deletions/insertions up to 22 bp. Our NGS-based mutation screening strategy showed 99.99% concordance between NGS and Sanger sequencing, resulting in the analytical sensitivity and specificity of 100% and 99.99%, respectively.

Conclusion: This study demonstrated that our NGS-based mutation screening strategy is highly sensitive in detecting sequence variants in the selected hearing loss genes. Therefore, this approach would be a good alternative to current technologies for identifying the multiple genetic causes of hearing loss.

Neural Response Telemetry in Pediatric Cochlear Implantation

Objective: 1) Evaluate the neural response telemetry (NRT) of patients with inner ear anomalies, and determine correlations between NRT and postoperative speech recognition thresholds (SRT). 2) Determine if higher incidence of negative intraoperative NRT exists in pediatric patients with inner ear anomalies, namely enlarged vestibular aqueduct syndrome (EVAS).

Method: Retrospective chart review of pediatric patients who underwent cochlear implantation at a tertiary care pediatric referral center from 2001 to present. Patients with inner ear anomalies were age matched to controls without anomalies. Associations between abnormal NRT and perilymphatic gusher and correlations between NRT and audiometry were assessed.

Results: Twenty-seven subjects with radiographic evidence of EVAS were evaluated; 35 ears implanted. Median age of implantation was 77.5 months. NRT was normal in 69%, abnormal 11%, marginal 6%, missing 4%. Intraoperative data revealed a perilymphatic gusher in 8 patients (23%); of which 50% had abnormal NRT compared to 8% among patients without gusher ( P = .03). Postoperative audiometric data were available for 8 out of 35 ears. No significant correlations between intraoperative and postoperative NRT with postoperative SRT at 1 kHz, 2 kHz, 4 kHz ( P > .2). There appeared to be a correlation between intraoperative NRT and postoperative SRT at 500 kHz (ρ = 0.68, P = .14); this was not statistically significant.

Conclusion: The presence of perilymphatic gusher at the time of cochlear implantation in patients with enlarged vestibular aqueduct syndrome (EVAS) seems to be related to abnormal NRT. There is no significant correlation between intraoperative and postoperative NRT and speech recognition thresholds (SRT) at 1 kHZ, 2 kHz, and 4 kHz in patients with EVAS.

Failure on the Newborn Infant Hearing Screen: What’s Next?

Program Description: Hearing screening for newborn infants has become commonplace. The Joint Commission on Infant Hearing (JCIH) in its position statements has created goals and guidelines for managing these children in a timely manner. The early hearing detection and intervention (EHDI) process is designed to maximize linguistic and communicative competence and literacy development for children who are deaf or hard of hearing. Without appropriate opportunities to learn language, these children will fall behind their hearing peers in language, cognition, and social-emotional development. Such delays may result in lower educational and employment levels in adulthood. Early diagnosis and treatment of hearing impaired infants in the first year of life has been shown to avoid the detrimental effects of delayed action. Despite this fact and a high screening rate among programs (>95%), almost half of those infants who do not pass the initial screening fail to have appropriate and timely follow-up including audiological and medical assessment by an individual with training in pediatric hearing disorders. Rather, families are often times reassured or misinformed by well-intentioned professionals about this process and the consequences of delayed intervention. This miniseminar will provide the fundamental framework for obtaining timely and accurate audiological and medical diagnosis and hearing instrument fitting (hearing aids or cochlear implants). Recognized professionals in the field will cover topics such as electrophysiological hearing testing, practical application and results of amplification, medical assessment including radiological and genetic evaluation, and the criteria and results of cochlear implantation. Issues relevant to delayed diagnosis and intervention such as organizational structure, awareness, funding, and necessary political activity will be addressed.

Educational Objectives: 1) Understand the significance of a failure result on the newborn infant hearing screening examination. 2) Learn the fundamental, multidisciplinary evaluation, and management paradigm for infants that fail the newborn screen. 3) Understand the cause and consequences of inappropriate or delayed intervention in hearing impaired children.

Genetic mutations and aminoglycoside-induced ototoxicity in neonates

OBJECTIVE

Mutations in the 12S rRNA gene have been associated with aminoglycoside-induced ototoxicity. Our objective was to study the relationship of these mutations in neonates, duration of aminoglycoside exposure, and other known risk factors to the presence of hearing loss.

STUDY DESIGN

Prospective case-cohort study.

SETTING

Three neonatal intensive care units (NICUs) in Cincinnati, OH.

SUBJECTS AND METHODS

We studied a population of premature, low-birth-weight (< 2500 g) infants admitted to one of three ICUs. Demographic, genetic, clinical, and audiometric data were collected, and the prevalence of 12S rRNA mutations was calculated.

RESULTS

Of the 436 patients enrolled in the study, 378 were exposed to gentamicin during their ICU stay. Mutations in the 12S rRNA gene were identified in four patients (0.9%), all of whom received gentamicin. Of the cohort, 256 patients (60%) received a complete audiometric assessment; 39 failed their initial hearing assessment. Only one of these patients had a 12S rRNA mutation. Of these 39 patients, the mean birth weight (1645 g vs 1306 g) was significantly less than the birth weight of those infants who passed their initial hearing screening. Definitive hearing assessment for those who failed showed no significant differences, however.

CONCLUSION

The prevalence of 12S rRNA mutations related to aminoglycoside ototoxicity in our study population was approximately one percent. Most patients with this mutation and aminoglycoside exposure showed no evidence of hearing loss. Low birth weight was one risk factor related to the presence of failing a hearing assessment.

H1N1 influenza A presenting as bacterial tracheitis

Six cases of bacterial tracheitis (BT) occurring early in the 2009 flu season have been isolated in conjunction with the H1N1 strain of influenza A (H1N1). No previous H1N1 cases have presented as BT in the literature to date. We would like to discuss viral coinfection in BT patients and how this new strain may affect the rate and type of presentation encountered. The life-threatening potential of BT and the pandemic proportion of H1N1 highlight a possibly dangerous combination that should be recognized by the otolaryngology community. In hospitalized patients with presumed BT, consideration should be given to routine H1N1 testing and the addition of antiviral medication when indicated as this entity is further investigated.

High-throughput detection of mutations responsible for childhood hearing loss using resequencing microarrays

BACKGROUND

Despite current knowledge of mutations in 45 genes that can cause nonsyndromic sensorineural hearing loss (SNHL), no unified clinical test has been developed that can comprehensively detect mutations in multiple genes. We therefore designed Affymetrix resequencing microarrays capable of resequencing 13 genes mutated in SNHL (GJB2, GJB6, CDH23, KCNE1, KCNQ1, MYO7A, OTOF, PDS, MYO6, SLC26A5, TMIE, TMPRSS3, USH1C). We present results from hearing loss arrays developed in two different research facilities and highlight some of the approaches we adopted to enhance the applicability of resequencing arrays in a clinical setting.

RESULTS

We leveraged sequence and intensity pattern features responsible for diminished coverage and accuracy and developed a novel algorithm, sPROFILER, which resolved >80% of no-calls from GSEQ and allowed 99.6% (range: 99.2-99.8%) of sequence to be called, while maintaining overall accuracy at >99.8% based upon dideoxy sequencing comparison.

CONCLUSIONS

Together, these findings provide insight into critical issues for disease-centered resequencing protocols suitable for clinical application and support the use of array-based resequencing technology as a valuable molecular diagnostic tool for pediatric SNHL and other genetic diseases with substantial genetic heterogeneity.

An overview of custom array sequencing

This unit provides an overview of oligo hybridization-based resequencing and a wide range of considerations for implementing the technology and analyzing the resulting data. The specific technology discussed is the Affymetrix GeneChip CustomSeq Resequencing Array platform. Concepts related to array design, experimental protocols, and base-calling using existing algorithms are presented. Details that should be evaluated during development of sequence tiling, target amplification, and PCR protocols are addressed. An overview of the Affymetrix GeneChip Sequence Analysis Software (GSEQ) is provided, along with factors that influence base-calling coverage and accuracy. Also outlined are performance measures that can be used to characterize base-calling with resequencing arrays, as well as factors known to affect their performance. Limitations associated with detection of insertions and deletions (indels) are discussed, with empirical data from our experiments used to outline possible approaches to indel detection. Critical topics in the design, implementation, and analysis of targeted sequencing arrays not previously discussed in detail are highlighted.

Audiologic and temporal bone imaging findings in patients with sensorineural hearing loss and GJB2 mutations

OBJECTIVES/HYPOTHESIS

Our objectives were to determine genotype-phenotype correlations in patients with sensorineural hearing loss (SNHL) who undergo testing for GJB2 mutations and to examine the relationship of temporal bone anomalies seen on computed tomography (CT) and GJB2 mutations.

STUDY DESIGN

We conducted a retrospective review of all children diagnosed with SNHL and who underwent GJB2 testing from 1997 to 2006.

RESULTS

Of 840 patients, 146 (17.4%) had mutations. Seventy-six (9.1%) had biallelic GJB2 mutations and 70 (8.3%) had heterozygous mutations. When biallelic mutations were categorized as missense or nonsense mutations, the presence of at least one missense mutation was associated with mild or moderate SNHL. Biallelic nonsense mutations were associated with severe to profound SNHL. Among patients with GJB2 mutations, those with heterozygous mutations (n = 14 [20%]) had a higher rate of asymmetric SNHL loss than those with biallelic mutations (n = 6 [7.9%], P = .03). Those with heterozygous mutations were more likely to experience progression than were those with biallelic mutations, though this difference was only marginally significant (26.5% vs. 12.3%, respectively; P = .06). Patients who were wild type for GJB2 were more likely to have an enlarged vestibular aqueduct (EVA) than were those with biallelic and heterozygous mutations (29% vs. 11.9%, respectively; P = .004). Compared to patients who were wild type, those with biallelic mutations had a significantly lower rate of EVA.

CONCLUSIONS

This is the largest single-institution study of pediatric patients with GJB2 mutations and SNHL. The functional consequences of GJB2 mutations correlated with the degree of hearing loss. Patients with M34T mutations and/or mild SNHL had a low risk of progression. Temporal bone anomalies were uncommon in patients with GJB2 mutations.

A rapid method for detection of five known mutations associated with aminoglycoside-induced deafness

Background

South Africa has one of the highest incidences of multidrug-resistant tuberculosis (MDR-TB) in the world. Concomitantly, aminoglycosides are commonly used in this country as a treatment against MDR-TB. To date, at least five mutations are known to confer susceptibility to aminoglycoside-induced hearing loss. The aim of the present study was to develop a rapid screening method to determine whether these mutations are present in the South African population.

Methods

A multiplex method using the SNaPshot technique was used to screen for five mutations in the MT-RNR1 gene: A1555G, C1494T, T1095C, 961delT+C(n) and A827G. A total of 204 South African control samples, comprising 98 Mixed ancestry and 106 Black individuals were screened for the presence of the five mutations.

Results

A robust, cost-effective method was developed that detected the presence of all five sequence variants simultaneously. In this pilot study, the A1555G mutation was identified at a frequency of 0.9% in the Black control samples. The 961delT+C(n) variant was present in 6.6% of the Black controls and 2% of the Mixed ancestry controls. The T1095C, C1494T and A827G variants were not identified in any of the study participants.

Conclusion

The frequency of 0.9% for the A1555G mutation in the Black population in South Africa is of concern given the high incidence of MDR-TB in this particular ethnic group. Future larger studies are warranted to determine the true frequencies of the aminoglycoside deafness mutations in the general South African population. The high frequencies of the 961delT+C(n) variant observed in the controls suggest that this change is a common non-pathogenic polymorphism. This genetic method facilitates the identification of individuals at high risk of developing hearing loss prior to the start of aminoglycoside therapy. This is important in a low-resource country like South Africa where, despite their adverse side-effects, aminoglycosides will continue to be used routinely and are accompanied with very limited or no audiological monitoring.

Macrophage inflammatory proteins in cytomegalovirus-related inner ear injury

OBJECTIVE

Inner ear inflammation triggered by CMV infection may play a role in CMV-related auditory pathogenesis. The purpose of the study was to determine if a virally encoded macrophage inflammatory protein played a role in CMV-related hearing loss.

DESIGN

Mutagenesis was performed with deletion of a guinea pig CMV macrophage inflammatory protein. Intracochlear inoculations were performed on three groups of animals (n = 18). Group 1 received sterile viral media, Group 2 received wild-type CMV virus, and Group 3 received "knockout" (KO) virus with a deleted immunomodulation gene. Baseline and postinoculation ABRs were obtained. ELISA and PCR were performed and temporal bones examined.

SUBJECTS

Eighteen guinea pigs.

RESULTS

The KO group had significantly better hearing than the WT group. There were no significant differences between the KO and sham groups. The WT group had significant hearing loss at all frequencies. Inflammation and fibrosis were noted in the WT temporal bones only.

CONCLUSIONS

Virally encoded macrophage inflammatory proteins appear to play a significant role in CMV-related hearing loss.

The role of CMV inflammatory genes in hearing loss

HYPOTHESIS

The purpose of this study is to test the hypothesis that virally encoded immunomodulatory genes play a role in cytomegalovirus (CMV)-related hearing loss.

OBJECTIVE

Cytomegalovirus is the leading cause of infectious-related congenital sensorineural hearing loss worldwide. Unfortunately, little is known about the pathophysiology of CMV-related injury to the developing ear.

METHODS

Viral mutagenesis techniques were developed that allow the deletion of a specific viral immunomodulatory gene, macrophage inflammatory protein (MIP) 1alpha homolog. We assessed the extent to which this gene product contributed to auditory pathologic findings in the guinea pig (GP) model. Eighteen weanling GPs (250-350 g) were used under an Institutional Animal Control and Use Committee-approved protocol. We analyzed preinoculation hearing using auditory brainstem response recordings. Intracochlear inoculations were performed on one group of six GPs with sterile viral media, 6 GPs with wild-type (WT) CMV virus, and 6 GPs with mutant "knockout" (KO) virus (with deleted MIP-1alpha homolog). Auditory brainstem responses were then obtained on postinoculation Days 7, 14, 21, and 28.

RESULTS

There was a significant difference in hearing between the KO group and the WT group, with significantly better hearing in the KO group. A comparison of the KO group to the sham group revealed no significant hearing differences between the groups. The WT group had significant threshold shifts by dose at all frequencies meeting our criteria of hearing loss (>30 dB). There were no statistical differences in the sham or KO group.

CONCLUSION

Virally encoded immunomodulatory genes such as MIP-1alpha seem to play a significant role in CMV-related hearing loss. This study is the first demonstration of the role of specific viral immune modulation genes in the in vivo pathogenesis of CMV-induced hearing loss in a relevant animal model.

Maternally inherited aminoglycoside-induced and nonsyndromic hearing loss is associated with the 12S rRNA C1494T mutation in three Han Chinese pedigrees

We report here the clinical, genetic and molecular characterization of three Han Chinese pedigrees with maternally transmitted aminoglycoside-induced and nonsyndromic bilateral hearing loss. Clinical evaluation revealed the wide range of severity, age-at-onset and audiometric configuration of hearing impairment in matrilineal relatives in these families. The penetrances of hearing loss in these pedigrees were 28%, 20%, and 15%, with an average of 21%, when aminoglycoside-induced deafness was included. When the effect of aminoglycosides was excluded, the penetrances of hearing loss in these seven pedigrees were 21%, 13% and 8%, with an average of 14%. Sequence analysis of the complete mitochondrial genomes in these pedigrees showed the presence of the deafness-associated 12S rRNA C1494T mutation, in addition to distinct sets of mtDNA polymorphism belonging to Eastern Asian haplogroups F1a1, F1a1 and D5a2, respectively. This suggested that the C1494T mutation occurred sporadically and multiplied through evolution of the mtDNA. The absence of functionally significant mutations in tRNA and rRNAs or secondary LHON mutations in their mtDNA suggests that these mtDNA haplogroup-specific variants may not play an important role in the phenotypic expression of the C1494T mutation in those Chinese families. In addition, the lack of significant mutation in the GJB2 gene ruled out the possible involvement of GJB2 in the phenotypic expression of the C1494T mutation in those affected subjects. However, aminoglycosides and other nuclear modifier genes play a modifying role in the phenotypic manifestation of the C1494T mutation in these Chinese families.

A multicenter study of the frequency and distribution of GJB2 and GJB6 mutations in a large North American cohort

PURPOSE

The aim of the study was to determine the actual GJB2 and GJB6 mutation frequencies in North America after several years of generalized testing for autosomal recessive nonsyndromic sensorineural hearing loss to help guide diagnostic testing algorithms, especially in light of molecular diagnostic follow-up to universal newborn hearing screening.

METHODS

Mutation types, frequencies, ethnic distributions, and genotype-phenotype correlations for GJB2 and GJB6 were assessed in a very large North American cohort.

RESULTS

GJB2 variants were identified in 1796 (24.3%) of the 7401 individuals examined, with 399 (5.4%) homozygous and 429 (5.8%) compound heterozygous. GJB6 deletion testing was performed in 12.0% (888/7401) of all cases. The >300-kb deletion was identified in only nine individuals (1.0%), all of whom were compound heterozygous for mutations in GJB2 and GJB6. Among a total of 139 GJB2 variants identified, 53 (38.1%) were previously unreported, presumably representing novel pathogenic or benign variants.

CONCLUSIONS

The frequency and distribution of sequence changes in GJB2 and GJB6 in North America differ from those previously reported, suggesting a considerable role for loci other than GJB2 and GJB6 in the etiology of autosomal recessive nonsyndromic sensorineural hearing loss, with minimal prevalence of the GJB6 deletion.

Prevalence and Etiology of Hearing Loss in Rural Nicaraguan Children

OBJECTIVE/HYPOTHESIS

The prevalence and causes of pediatric hearing loss (HL) in the developing world are largely unknown. Infectious sequelae, ototoxic medications, and genetic causes may play a larger role in developing countries. In addition, the significance of GJB2 mutation gene in poorly developed areas remains unclear. The intent of this study is to investigate the prevalence and etiology of HL in children living in a remote, impoverished region of northern Nicaragua.

STUDY DESIGN

Cross-sectional study.

METHODS

Clinical data from two sources were analyzed: data from screening examinations performed in rural schools in the Department of Jinotega, Nicaragua (group A) and pediatric HL patients seen at the Otolaryngology and Audiology Clinic in Jinotega, Nicaragua (group B). Patients with congenital HL were offered a genetic test for GJB2 mutations. Comparisons were made using parametric (analysis of variance) and nonparametric (Kruskal-Wallis) tests.

RESULTS

School-based screening examinations (group A) revealed a high prevalence of significant HL (>30 dB) of 18%. The majority of these children had normal otoscopic examinations (58%). A family history of HL was seen in 24% of children who failed screening exams. Positive family history was more common in patients with HL (P < .01) and in specific schools (P < .05). Clinic-based evaluations (group B) reveal a population with predominantly severe-profound HL. Physical dysmorphism was common, yet identifiable syndromic HL was rare. Although familial HL was common (33%), there were no pathologic GJB2 mutations. Other common risk factors in this population were maternal infection during pregnancy, neonatal distress, low birth weight or prematurity, and gentamicin exposure.

CONCLUSIONS

HL in this rural, third world environment is more prevalent, and the etiologies responsible in this study group are different from those encountered in industrialized nations. Poor perinatal health care, infectious causes, gentamicin exposure, and hereditary HL are potentially preventable causes that play a major role in this population.

Cosegregation of the G7444A mutation in the mitochondrial COI/tRNA(Ser(UCN)) genes with the 12S rRNA A1555G mutation in a Chinese family with aminoglycoside-induced and nonsyndromic hearing loss

We report here on the characterization of a three-generation Chinese family with aminoglycoside-induced and nonsyndromic hearing impairment. Ten of 17 matrilineal relatives exhibited bilateral and sensorineural hearing impairment. Of these, nine matrilineal relatives, who had a history of exposure to aminoglycosides, exhibited variable severity and audiometric configuration of hearing loss. The dose and age at the time of drug administration seemed to be correlated with the severity of the hearing loss experienced by affected individuals. Sequence analysis of the complete mitochondrial genome in the pedigree showed the presence of homoplasmic A1555G mutation and 37 variants belonging to haplogroup D4a. Of those variants, the G7444A mutation is of special interest as the mutation at this position results in a read-through of the stop condon AGA of the COI message, thereby adding three amino acids (Lys-Gln-Lys) to the C-terminal of the polypeptide. Alternatively, the G7444A mutation is adjacent to the site of 3' end endonucleolytic processing of L-strand RNA precursor, spanning tRNA(Ser(UCN)) and ND6 mRNA. Thus, the G7444A mutation, similar to the deafness-associated A7445G mutation, may lead to a defect in the processing of the L-strand RNA precursor, thus influencing the phenotypic expression of the A1555G mutation. These data also imply that nuclear background plays a role in the aminoglycoside ototoxicity associated with the A1555G mutation in this Chinese pedigree.

Improved diagnostic effectiveness with a sequential diagnostic paradigm in idiopathic pediatric sensorineural hearing loss

OBJECTIVES

To determine whether a stepwise diagnostic paradigm is more diagnostically efficient and cost-effective than a simultaneous testing approach in the evaluation of idiopathic pediatric sensorineural hearing loss (SNHL).

DESIGN

Prospective prevalence study.

SETTING

Tertiary referral children's hospital.

PATIENTS

Consecutive children (n = 150) presenting with idiopathic SNHL in the last 2 years.

INTERVENTIONS

All children were evaluated with full diagnostic evaluations including GJB2 screens, temporal bone computed tomography scans, and laboratory investigations.

MAIN OUTCOME MEASURES

1) Diagnostic yields of GJB2 screens, imaging, and laboratory results per SNHL category; 2) Cost analysis comparing a sequential versus a simultaneous testing approach.

RESULTS

Overall, 12.0% of patients had biallelic mutations in the GJB2 gene, whereas 30% of patients had an abnormality on temporal bone scan. Laboratory testing did not reveal the SNHL etiology in any patient. While maintaining diagnostic accuracy, significant cost savings were inferred by using a sequential diagnostic algorithm. Our data show children with severe to profound SNHL should first be tested with a GJB2 screen, as opposed to those with milder SNHL, who should undergo imaging as the initial testing step. In patients with initially positive GJB2 or imaging screens, logistic regression analysis significantly predicted negative results on further testing.

CONCLUSIONS

A stepwise diagnostic paradigm tailored to the level of the hearing loss in children with bilateral SNHL is more diagnostically efficient and cost effective than the more commonly used full, simultaneous testing approach. Laboratory investigation should not be routine but based on clinical history.

Clinical and molecular characterization of a Chinese patient with auditory neuropathy associated with mitochondrial 12S rRNA T1095C mutation

Mutations in mitochondrial DNA (mtDNA), particularly those in the 12S rRNA gene, have been shown to be associated with sensorineural hearing loss. Recently, a systematic and extended mutation screening of the mitochondrial 12S rRNA gene has been initiated in the large clinical population of the Otology Clinic at the Chinese PLA General Hospital with the aim of identifying mtDNA mutations associated with hearing loss. Here we report the clinical and molecular characterization of a Chinese patient with auditory neuropathy. Sequence analysis of mtDNA in this patient identified a T-to-C transition at position 1095 (T1095C) in the 12S rRNA gene and other nucleotide changes. The T1095C mutation is expected to disrupt an evolutionarily conserved A-to-U base-pair, which is at the highly conserved P-site of 12S rRNA. The T1095C mutation has also been found to be associated with hearing loss in several unrelated families. Among other nucleotide changes, two novel variants: the I175V mutation in the CO2 and the V112M mutation in the ND6 localize at highly evolutionarily conserved residues from different organisms. Furthermore, the absence of mutation in the otoferlin related to auditory neuropathy showed that otoferlin may not be involved in the phenotypic expression of T1095C mutation in this subject. These data suggest that the T1095C mutation may be associated with auditory neuropathy in this subject, and two novel variants I175V and V112M may play a role in the phenotypic expression of the T1095C mutation.

Extremely low penetrance of hearing loss in four Chinese families with the mitochondrial 12S rRNA A1555G mutation

Mutations in mitochondrial DNA (mtDNA) have been found to be associated with sensorineural hearing loss. We report here the clinical, genetic, and molecular characterization of four Chinese pedigrees with aminoglycoside-induced and nonsyndromic hearing impairment. Clinical evaluation revealed the variable phenotype of hearing impairment including audiometric configuration in these subjects, although these subjects share some common features: bilateral and sensorineural hearing impairment. Strikingly, these Chinese pedigrees exhibited extremely low penetrance of hearing loss (5.2%, 4.8%, 4.2%, and 13.3%, respectively, and with an average 8% penetrance). In particular, four of all five affected matrilineal relatives of these pedigrees had aminoglycoside-induced hearing loss. Sequence analysis of the complete mitochondrial genomes in these pedigrees showed the distinct sets of mtDNA polymorphism, in addition to the identical homoplasmic A1555G mutation, associated with hearing impairment in many families from different genetic backgrounds. The fact that mtDNA of those pedigrees belonged to different haplogroups R9a, N9a, D4a, and D4 suggested that the A1555G mutation occurred sporadically and multiplied through evolution of the mtDNA in China. However, there was the absence of functionally significant mutations in tRNA and rRNAs or secondary LHON mutations in these Chinese families. These data imply that the nuclear background or/and mitochondrial haplotype may not play a significant role in the phenotypic expression of the A1555G mutation in these Chinese pedigrees. However, aminoglycoside appears to be a major modifier factor for the phenotypic manifestation of the A1555G mutation in these Chinese families.

A diagnostic paradigm for childhood idiopathic sensorineural hearing loss

OBJECTIVE

Our objective was to determine the diagnostic yield of laboratory testing, radiological imaging, and GJB2 mutation screening in a large cohort of patients with differing severities of idiopathic sensorineural hearing loss (SNHL).

DESIGN AND SETTING

We undertook a retrospective study of patients presenting with SNHL at our institution from 1993 to 2002.

RESULTS

Laboratory testing had an extremely low yield. Patients with unilateral SNHL had a significantly higher imaging yield than those with bilateral. The diagnostic yield of GJB2 screening was significantly higher in patients with severe to profound SNHL than in those with less severe SNHL. However, a relatively large number of patients with mild to moderate SNHL had positive GJB2 screens.

CONCLUSIONS

Based on diagnostic yields, we propose a cost-effective stepwise diagnostic paradigm to replace the more commonly used and costly simultaneous testing approach.

EBM RATING

C.

Refining the DFNB17 interval in consanguineous Indian families

We previously mapped the DFNB17 locus to a 3-4 cM interval on human chromosome 7q31 in a large consanguineous Indian family with congenital profound sensorineural hearing loss. To further refine this interval, 30 new highly polymorphic markers and 8 SNPs were analyzed against the pedigree. Re-analysis in the original DFNB 17 family and additional data from a second unrelated consanguineous family with congenital deafness found to map to the interval, limited the area of shared homozygosity-by-descent (HBD) to approximately 4 megabase (Mb) between markers D7S2453 and D7S525. Nineteen known genes and over 20 other cDNAs have been identified in the refined DFNB 17 interval, including the SLC26A4 gene. We have analyzed 4 other cochlear-expressed genes that map to the DFNB17 interval as candidate genes. Analysis of coding and splice site regions of these cochlear expressed genes did not reveal any disease causing mutations. Further study of other candidate genes is currently underway.

Co-expression of pendrin, vacuolar H+-ATPase alpha4-subunit and carbonic anhydrase II in epithelial cells of the murine endolymphatic sac

The endolymph in the endolymphatic sac (ES) is acidic (pH 6.6-7). Maintaining this acidic lumen is believed to be important for the normal function of the ES. The acid-base regulation mechanisms of the ES are unknown. Here we investigated the expression patterns of acid-base regulators, including vacuolar (v)H+-ATPase (proton pump), carbonic anhydrase (CA) II, and pendrin in the murine ES epithelium by immunohistochemistry (IHC) and compared their expression patterns by double immunostaining. We found that pendrin and vH+-ATPase were co-localized in the apical membrane of a specific type of ES epithelial cell. Pendrin- and vH+-ATPase-positive cells also expressed cytoplasmic CA II. Co-expression of pendrin, vH+-ATPase, and CA II in the same subgroup of ES cells suggests that this specific type of ES cell is responsible for the acid-base balance processes in the ES and pendrin, vH+-ATPase, and CA II are involved in these processes.

Genomic organization and expression analysis of the murine Fam3c gene

Previously, we identified FAM3C as a candidate gene for autosomal recessive nonsyndromic hearing loss locus 17 (DFNB17). This gene has since been found to be a member of a cytokine-like gene family, but its function has not been determined. The purpose of this study was thus to elucidate the gene structure and pattern of expression, providing information that might allow a hypothesis to be developed about FAM3C function of in the inner ear. To do this we analyzed its mouse ortholog, Fam3c. Fam3c was found to be ubiquitously expressed in all analyzed tissues, and had two major transcript variants presumed to result from an alternative use of two distinct polyadenylation signals. In situ hybridization experiments revealed a predominant Fam3c pattern of expression in the nonsensory epithelium of the growing semicircular canals at embryonic day (E) 15.5. This expression pattern resembles the known pattern of the Nkx5 homeobox genes. Analysis of the Fam3c promoter region demonstrated a putative Nkx5.1 binding site. Based on our findings, we hypothesize that Fam3c may be a downstream target gene for the Nkx5.1 transcription factor, and may thus be involved in cell differentiation and proliferation during inner ear embryogenesis. Additionally, analyses of putative amino acid sequences of FAM3C orthologous proteins showed that their primary and secondary structures and overall topology were highly conserved. Further study is underway to determine the role of FAM3C in inner ear development.

The cochlear cleft

BACKGROUND AND PURPOSE

Recent advances in the display of medical images permit the routine study of temporal bone CT images at high magnification. We noted an unfamiliar structure, which we now call the "cochlear cleft," in the otic capsule. To our knowledge, this report represents the first description of this structure in the medical imaging literature.

METHODS

Temporal bone CT performed in 100 pediatric patients without sensorineural hearing loss were examined for the presence of cochlear clefts. Incidence of cochlear clefts as well as the relationship between age and incidence was examined.

RESULTS

Cochlear clefts were present in 41% of the subjects. Incidence decreased with age.

CONCLUSION

We describe a cleft in the otic capsule that is frequently seen on magnified images of temporal bone CT studies in children. The cleft may be the fissula ante fenestram.

Temporal bone abnormalities associated with hearing loss in Waardenburg syndrome

OBJECTIVES/HYPOTHESIS

The objectives were to correlate audiometric thresholds with radiological findings and to determine the prevalence of inner ear radiological abnormalities in patients with hearing loss and Waardenburg syndrome.

STUDY DESIGN

The study was a retrospective review of patients with Waardenburg syndrome identified in a pediatric hearing-impaired population and human genetics clinic.

METHODS

Nine children with Waardenburg syndrome were identified. Eighty-nine children without sensorineural hearing loss served as control subjects. Clinical data, audiometric thresholds, and radiographic temporal bone measurements in these children were analyzed.

RESULTS

Seven children were identified with hearing loss and Waardenburg syndrome. Four children had Waardenburg syndrome type 1, and three children had Waardenburg syndrome type 2. The overall prevalence of hearing loss in the total study population with Waardenburg syndrome was 78%. The mean pure-tone average was 99 dB. All of the children had sensorineural hearing loss. The hearing outcome was stable in 86% of the children. Twelve temporal bones were available for radiological analysis by computed tomography. Enlargement of the vestibular aqueduct was found in 50% of the CT scans. There was a significant difference in measurements of vestibular aqueduct width at the midpoint between the patients with Waardenburg syndrome and the control group (P <.05). There were also significant differences in the measurements of the vestibule (P =.0484), internal auditory canal (P =.0092), and modiolus (P =.0045) between the children with Waardenburg syndrome and the control group.

CONCLUSION

A profound sensorineural hearing loss was characteristic of the study population with Waardenburg syndrome. Overall, 100% of patients with hearing loss and Waardenburg syndrome had temporal bone anomalies on at least one measurement of their inner ear, and 50% had an enlargement of the vestibular aqueduct at the midpoint. As shown by computed tomography, enlargement of the vestibular aqueduct and the upper vestibule, narrowing of the internal auditory canal porus, and hypoplasia of the modiolus are features of Waardenburg syndrome.