Microtia and Congenital Aural Atresia:

Functional and Genetic Analyses Unveil the Implication of CDC27 in Hemifacial Microsomia

Hemifacial microsomia (HFM) is a rare congenital genetic syndrome primarily affecting the first and second pharyngeal arches, leading to defects in the mandible, external ear, and middle ear. The pathogenic genes remain largely unidentified. Whole-exome sequencing (WES) was conducted on 12 HFM probands and their unaffected biological parents. Predictive structural analysis of the target gene was conducted using PSIPRED (v3.3) and SWISS-MODEL, while STRING facilitated protein-to-protein interaction predictions. CRISPR/Cas9 was applied for gene knockout in zebrafish. In situ hybridization (ISH) was employed to examine the spatiotemporal expression of the target gene and neural crest cell (NCC) markers. Immunofluorescence with PH3 and TUNEL assays were used to assess cell proliferation and apoptosis. RNA sequencing was performed on mutant and control embryos, with rescue experiments involving target mRNA injections and specific gene knockouts. CDC27 was identified as a novel candidate gene for HFM, with four nonsynonymous de novo variants detected in three unrelated probands. Structural predictions indicated significant alterations in the secondary and tertiary structures of CDC27. cdc27 knockout in zebrafish resulted in craniofacial malformation, spine deformity, and cardiac edema, mirroring typical HFM phenotypes. Abnormalities in somatic cell apoptosis, reduced NCC proliferation in pharyngeal arches, and chondrocyte differentiation issues were observed in cdc27-/- mutants. cdc27 mRNA injections and cdkn1a or tp53 knockout significantly rescued pharyngeal arch cartilage dysplasia, while sox9a mRNA administration partially restored the defective phenotypes. Our findings suggest a functional link between CDC27 and HFM, primarily through the inhibition of CNCC proliferation and disruption of pharyngeal chondrocyte differentiation.

Hearing rehabilitation with osseointegrated hearing implant in bilateral congenital external auditory canal atresia

INTRODUCTION AND OBJECTIVES

Congenital atresia of the external auditory canal (EAC) is a congenital defect present in one in every 10,000-20,000 births. It causes conductive hearing loss, with an air-bone gap of 50-60dB. Early amplification is essential in bilateral cases to ensure normal language development. The aim of this study is to present the osseointegrated hearing implant as a treatment for bilateral EAC atresia, reviewing the audiometric results and the rate of complications.

MATERIAL AND METHODS

Retrospective analysis of patients diagnosed with bilateral congenital EAC atresia under follow-up in the pediatric ENT clinic of the ENT and Head and Neck Surgery department of a Portuguese Tertiary Hospital, between 2003 and 2019. We reviewed the medical records and collected information on the assessment of the initial audiometric status. In the cases submitted for implantation with an osseointegrated hearing implant, we analyzed the details of follow-up, including immediate and long-term post-operative complications, as well as the audiometric results.

RESULTS

We present 8 pediatric patients, 6 girls and 2 boys, with a diagnosis of bilateral congenital EAC atresia. The audiometric assessment revealed moderate to severe bilateral conductive hearing loss with a mean speech recognition threshold (SRT) of 51dB. Six patients underwent osseointegrated hearing implantation. All 6 patients showed good audiometric results, with an average SRT of 20dB and closure of the air-bone gap.

CONCLUSIONS

The osseointegrated hearing implant was an effective treatment option in these patients, without significant morbidity or complications. Osseointegrated hearing implantation should be considered first line treatment for children with bilateral congenital EAC atresia, as it presents good functional results and a high level of patient satisfaction.

Hearing rehabilitation with osseointegrated hearing implant in bilateral congenital external auditory canal atresia

INTRODUCTION AND OBJECTIVES

Congenital atresia of the external auditory canal (EAC) is a congenital defect present in one in every 10,000-20,000 births. It causes conductive hearing loss, with an air-bone gap of 50-60dB. Early amplification is essential in bilateral cases to ensure normal language development. The aim of this study is to present the osseointegrated hearing implant as a treatment for bilateral EAC atresia, reviewing the audiometric results and the rate of complications.

MATERIAL AND METHODS

Retrospective analysis of patients diagnosed with bilateral congenital EAC atresia under follow-up in the pediatric ENT clinic of the ENT and Head and Neck Surgery department of a Portuguese Tertiary Hospital, between 2003 and 2019. We reviewed the medical records and collected information on the assessment of the initial audiometric status. In the cases submitted for implantation with an osseointegrated hearing implant, we analyzed the details of follow-up, including immediate and long-term post-operative complications, as well as the audiometric results.

RESULTS

We present 8 pediatric patients, 6 girls and 2 boys, with a diagnosis of bilateral congenital EAC atresia. The audiometric assessment revealed moderate to severe bilateral conductive hearing loss with a mean speech recognition threshold (SRT) of 51dB. Six patients underwent osseointegrated hearing implantation. All 6 patients showed good audiometric results, with an average SRT of 20dB and closure of the air-bone gap.

CONCLUSIONS

The osseointegrated hearing implant was an effective treatment option in these patients, without significant morbidity or complications. Osseointegrated hearing implantation should be considered first line treatment for children with bilateral congenital EAC atresia, as it presents good functional results and a high level of patient satisfaction.

Long-term evaluation of development in patients with bilateral microtia using softband bone conducted hearing devices

OBJECTIVE

The ability of early intervention with softband bone conducted hearing device (BCHD) to ensure normal development of speech, language and psychosocial situations remains undetermined. We aimed to evaluate auditory and speech development, as well as psychosocial situations of children with bilateral microtia fitted with a softband BCHD for 3-5 years.

METHODS

The study included 53 patients with bilateral microtia and 53 sex- and age-matched children with normal hearing. Auditory development was evaluated using the Meaningful Auditory Integration Scale (MAIS) and Categories of Auditory Performance (CAP). Speech Intelligibility Rating (SIR) and Meaningful Use of Speech Scale (MUSS) were used to assess speech development. The psychometric properties of these patients were evaluated using Achenbach's Child Behavior Checklist (CBCL), and subjective benefits were measured using the Glasgow Children's Benefit Inventory (GCBI) questionnaire.

RESULTS

The average unaided and aided hearing thresholds measured using VRA were 73.8 ± 5.1 dB HL and 30.5 ± 6.0 dB HL, respectively. The total MAIS scores of the patients were 89.6 ± 9.6% and 93.0 ± 8.8% of normal hearing children at the last follow-up. The CAP scores of the two groups were 6.5 ± 1.3 and 6.9 ± 0.3, respectively. The mean MUSS score of the patients and the control group were 31.9 ± 7.0 and 34.3 ± 6.0, respectively. The mean SIR score of the two groups were 4.6 ± 0.7 and 4.8 ± 0.4. CBCL found that only two patients could be considered problematic psychosocially. The average benefit score on the GCBI was 32.9 ± 29.3.

CONCLUSIONS

Softband BCHD significantly improved auditory development in patients with bilateral microtia, with speech development reaching the level of normal hearing peers. No significant behavioral problems were found in the patients, with subjective evaluations showing that softband BCHD improved patient quality of life.

Whole-Exome Sequencing of Discordant Monozygotic Twin Families for Identification of Candidate Genes for Microtia-Atresia

Objective

We used data from twins and their families to probe the genetic factors contributing to microtia-atresia, in particular, early post-twinning variations that potentially account for the discordant phenotypes of monozygotic twin pairs.

Methods

Six families of monozygotic twins discordant for congenital microtia-atresia were recruited for study. The six patients shared a consistent clinical phenotype of unilateral microtia-atresia. Whole-exome sequencing (WES) was performed for all six twin pairs and their parents. Family segregation and multiple bioinformatics methods were applied to identify suspicious mutations in all families. Recurring mutations commonly detected in at least two families were highlighted. All variants were validated via Sanger sequencing. Gene Ontology (GO) analysis was performed to identify candidate gene sets and related pathways. Copy number variation (CNV), linkage analysis, association analysis and machine learning methods were additionally applied to isolate candidate mutations, and comparative genomics and structural modeling tools used to evaluate their potential roles in onset of microtia-atresia.

Results

Our analyses revealed 61 genes with suspected mutations associated with microtia-atresia. Five (HOXA4, MUC6, CHST15, TBX10, and AMER1) contained 7 de novo mutations that appeared in at least two families, which have been previously reported as pathogenic for other diseases. Among these, HOXA4 (c.920A>C, p.H307P) was determined as the most likely pathogenic variant for microtia-atresia. GO analysis revealed four gene sets involving 11 pathways potentially related to underlying pathogenesis of the disease. CNVs in three genes (UGT2B17, OVOS, and KATNAL2) were detected in at least two families. Linkage analysis disclosed 13 extra markers for the disease, of which two (FGFR1 and EYA1) were validated via machine learning analysis as plausible candidate genes for the disease.

Conclusion

Based on comprehensive genetic and bioinformatic analyses of WES data from six families of discordant monozygotic twins with microtia-atresia, we identified multiple candidate genes that may function in post-twinning onset of the disease. The collective findings provide novel insights into the pathogenesis of congenital microtia-atresia.

Safety and efficacy of transcutaneous bone conduction implant surgery for hearing improvement in microtia patients with bilateral hearing impairment

Background

In microtia patients with bilateral hearing impairment, hearing improvement is crucial for language development and performance. External auditory canal reconstruction (EACR) has been performed to improve hearing, but often results in complications. We performed transcutaneous bone conduction implant (TBCI) surgery in these patients. This study aimed to evaluate the safety and efficacy of TBCI surgery.

Methods

A retrospective review was performed of five patients who underwent auricular reconstruction and TBCI surgery and 12 patients who underwent EACR between March 2007 and August 2018. Hearing improvement was measured based on the air-bone gap values using pure-tone audiometry over a 6-week postoperative period. We reviewed other studies on hearing improvement using EACR and compared the findings with our results. The surgical techniques for TBCI were reviewed through case analyses.

Results

Postoperative hearing outcomes showed a significant improvement, with a mean gain of 34.1 dB in the TBCI cohort and 14.1 dB in the EACR cohort. Both gains were statistically significant; however, the TBCI cohort showed much larger gains. Only three of the 12 patients who underwent EACR achieved hearing gains of more than 20 dB, which is consistent with previous studies. All patients who underwent TBCI surgery demonstrated hearing gains of more than 20 dB and experienced no device-related complications.

Conclusions

TBCI is a safe and effective method of promoting hearing gains in microtia patients with bilateral hearing impairment. TBCI surgery provided better hearing outcomes than EACR and could be performed along with various auricular reconstruction techniques using virgin mastoid skin.

Recommendations for the Development and Reform of Microtia and Atresia Services

BACKGROUND

The initial step in setting up standardized microtia-atresia service is investigating the current status of the service and comparing this to internationally recognized guidelines or care standards. In many countries, documented information about microtia care is lacking. This study is an initiative to guide reform efforts of national microtia service in any country. The UK care standards for microtia-atresia can be a useful model to help set up a comprehensive microtia-atresia service.

METHODS

The authors conducted a survey to investigate different aspects of microtia service in Egypt. The major plastic surgery centers (n = 22) were surveyed by a structured questionnaire. The results were compared with the UK care standards for microtia-atresia to identify the aspects that need improvement. Thorough analysis of the main problems in microtia-atresia service is presented.

RESULTS

The authors found that microtia service is fragmented between the surveyed centers with 65% of the centers treating less than 10 microtia cases annually. Multiple surgeons are responsible for ear reconstruction in 90% of centers and only 25% of them practise a multidisciplinary team approach. None of the centers uses validated tools of aesthetic or psychological patient-reported outcome measures.

RECOMMENDATIONS

These 5 recommendations are the keys to reforming microtia service in any country:(1) Establishing nationally designated centers to concentrate the required expertise.(2) Assigning fewer high-volume surgeons to optimize the surgical outcomes.(3) Providing treatment by experienced multidisciplinary teams.(4) Using validated tools of patient-reported outcome measures.(5) Collecting and keeping standardized records for regular audit and intercenter studies.

Identification of sequence variants associated with severe microtia-astresia by targeted sequencing

Background

Microtia-atresia is characterized by abnormalities of the auricle (microtia) and aplasia or hypoplasia of the external auditory canal, often associated with middle ear abnormalities. To date, no causal genetic mutations or genes have been identified in microtia-atresia patients.

Methods

We designed a panel of 131 genes associated with external/middle or inner ear deformity. Targeted genomic capturing combined with next-generation sequencing (NGS) was utilized to screen for mutations in 40 severe microtia-atresia patients. Mutations detected by NGS were filtered and validated. And then mutations were divided into three categories—rare or novel variants, low-frequency variants and common variants—based on their frequency in the public database. The rare or novel mutations were prioritized by pathogenicity analysis. For the low-frequency variants and common variants, we used association studies to explore risk factors of severe microtia-atresia.

Results

Sixty-five rare heterozygous mutations of 42 genes were identified in 27 (67.5%) severe microtia-atresia patients. Association studies to determine genes that were potentially pathogenic found that PLEC, USH2A, FREM2, DCHS1, GLI3, POMT1 and GBA genes were significantly associated with severe microtia-atresia. Of these, DCHS1 was strongly suggested to cause severe microtia-atresia as it was identified by both low-frequency and common variants association studies. A rare mutation (c.481C > T, p.R161C) in DCHS1 identified in one individual may be deleterious and may cause severe microtia-atresia.

Conclusion

We identified several genes that were significantly associated with severe microtia-atresia. The findings provide new insights into genetic background of external ear deformities.

Electronic supplementary material

The online version of this article (10.1186/s12920-019-0475-x) contains supplementary material, which is available to authorized users.

Analysis of Inner Ear Anomalies in Unilateral Congenital Aural Atresia Combined With Microtia

Objectives

The aim of this study was to analyze the incidence of inner ear anomalies in patients with unilateral congenital aural atresia (CAA) combined with microtia.

Methods

We retrospectively reviewed 61 patients with unilateral CAA combined with microtia who underwent high-resolution temporal bone computed tomography (TBCT) and hearing examination. Inner ear anomalies were analyzed using TBCT and evaluated according to the Jahrsdoerfer grading system, Marx classification, and extent of inferior displacement of the mastoid tegmen.

Results

Inner ear anomalies were observed in 14 patients (23.0%). Lateral semicircular canal (LSCC) dysplasia was the most common inner ear anomaly, with an incidence of 16.4%. The incidence was significantly higher on the pathologic side than on the unaffected side (P=0.002). All vascular anomalies were observed in the high-riding jugular bulb, with an incidence of 24.6%. The incidence was significantly higher on the pathologic side than on the unaffected side (P<0.001). LSCC dysplasia was significantly more common in patients with a lower Jahrsdoerfer score (odds ratio, 0.66; P=0.004).

Conclusion

The incidence of inner ear anomalies was relatively high in patients with unilateral CAA combined with microtia; LSCC dysplasia was the most common anomaly and the probability of coexistence was higher in patients with a lower Jahrsdoerfer score.