Congenital Malformations Of The External Auditory Canal

The spontaneous mouse mutant low set ears (Lse) is caused by tandem duplication of Fgf3 and Fgf4

The external ear develops from an organized convergence of ventrally migrating neural crest cells into the first and second branchial arches. Defects in external ear position are often symptomatic of complex syndromes such as Apert, Treacher-Collins, and Crouzon Syndrome. The low set ears (Lse) spontaneous mouse mutant is characterized by the dominant inheritance of a ventrally shifted external ear position and an abnormal external auditory meatus (EAM). We identified the causative mutation as a 148 Kb tandem duplication on Chromosome 7, which includes the entire coding sequences of Fgf3 and Fgf4. Duplications of FGF3 and FGF4 occur in 11q duplication syndrome in humans and are associated with craniofacial anomalies, among other features. Intercrosses of Lse-affected mice revealed perinatal lethality in homozygotes, and Lse/Lse embryos display additional phenotypes including polydactyly, abnormal eye morphology, and cleft secondary palate. The duplication results in increased Fgf3 and Fgf4 expression in the branchial arches and additional discrete domains in the developing embryo. This ectopic overexpression resulted in functional FGF signaling, demonstrated by increased Spry2 and Etv5 expression in overlapping domains of the developing arches. Finally, a genetic interaction between Fgf3/4 overexpression and Twist1, a regulator of skull suture development, resulted in perinatal lethality, cleft palate, and polydactyly in compound heterozygotes. These data indicate a role for Fgf3 and Fgf4 in external ear and palate development and provide a novel mouse model for further interrogation of the biological consequences of human FGF3/4 duplication.

Development of an interdisciplinary microtia-atresia care model: A single-center 20-year experience

Objectives

Microtia and aural atresia are congenital ear anomalies with a wide-ranging spectrum of phenotypes and varied functional and psychosocial consequences for patients. This study seeks to analyze the management of microtia-atresia patients at our center over a 20-year period and to propose recommendations for advancing microtia-atresia care at a national level.

Methods

We performed a retrospective analysis of data from patients presenting to the Massachusetts Eye and Ear (Boston, MA) for initial otolaryngology consultation for congenital microtia and/or aural atresia between 1999 and 2018.

Results

Over the 20-year study period, 229 patients presented to our microtia-atresia center at a median age of 7 years. The severity of microtia was most commonly classified as grade III (n = 87, 38%), 61% (n = 140) of patients had complete atresia, the median Jahrsdoerfer grading scale score was 6 (range 0-10), and 81 patients (35%) underwent surgery for microtia repair. For hearing rehabilitation, 30 patients (64%) underwent bone conduction device implantation and 17 patients (36%) underwent atresiaplasty. The implementation of an interdisciplinary, longitudinal care model resulted in an increase in patient (r = 0.819, p < .001) and surgical volume (microtia surgeries, r = 0.521, p = .019; otologic surgeries, r = 0.767, p < .001) at our center over time.

Conclusion

An interdisciplinary team approach to microtia-atresia patient care may result in increased patient volume, which could improve aesthetic and hearing outcomes over time by concentrating care and surgical expertise. Future work should aim to establish standardized clinical consensus recommendations to guide the creation of high-quality microtia-atresia care programs.

Level of Evidence

4.

Ear malformations: what do radiologists need to know?

Ear malformations represent 50% of ear, nose and throat malformations. Ear malformations cause conductive hearing loss (CHL) and/or sensorineural hearing loss (SNHL) with a significant childhood disability worldwide. Early accurate diagnosis and treatment are mandatory to enhance language and speech development. Understanding the embryology of the ear explains the outcome of ototoxic prenatal insult according to the affected gestational age and the incidence of association among inner, middle, and external ear malformations. Computed tomography (CT) and magnetic resonance imaging (MRI) examinations of the temporal bone are used in the evaluation of ear malformations. In this review article, the spectrum of ear malformations is discussed in detail with hints on the ear embryology, the ear radiological anatomy, and radiological determinant factors of operative reconstruction of ear anomalies.

Neural crest contributions to the ear: Implications for congenital hearing disorders

Congenital hearing disorders affect millions of children worldwide and can significantly impact acquisition of speech and language. Efforts to identify the developmental genetic etiologies of conductive and sensorineural hearing losses have revealed critical roles for cranial neural crest cells (NCCs) in ear development. Cranial NCCs contribute to all portions of the ear, and defects in neural crest development can lead to neurocristopathies associated with profound hearing loss. The molecular mechanisms governing the development of neural crest derivatives within the ear are partially understood, but many questions remain. In this review, we describe recent advancements in determining neural crest contributions to the ear, how they inform our understanding of neurocristopathies, and highlight new avenues for further research using bioinformatic approaches.

Correlation among external auditory canal anomaly, temporal bone malformation, and hearing levels in patients with microtia

We conducted a retrospective study to evaluate the relationship between external auditory canal (EAC) anomaly, temporal bone abnormality, and hearing levels using objective scoring systems in Chinese patients with microtia. The study population consisted of 106 ears of 94 Chinese patients (67 male and 27 female) aged 5 to 45 years (mean: 12.6) with microtia. The EAC abnormalities were classified into 4 types according to Schuknecht's criteria: type A, type B, type C, and type D. Developmental anomalies of the temporal bone were evaluated by Jahrsdoerfer computed tomography (CT) scoring system using high-resolution CT scans of the temporal bone. Temporal bone malformation parameters were divided into 4 subgroups: ossicular chain development, windows connected to the cochlea, aeration development of the middle ear, and facial nerve aberration. Hearing levels (air conduction and bone conduction) were examined. Outcomes parameters included correlation coefficients (r) and a number of other variables. The total points (10 points) and subtotal points related to ossicles (4 points), windows (2 points), aeration (2 points), and facial nerve (1 point) correlated inversely with the EAC abnormalities. The hearing levels (air conduction, r = 0.396, p <0.01; bone conduction, r = 0.21, p = 0.03) correlated significantly with the EAC abnormalities of Schuknecht's classification. We conclude that the better developed the external auditory canal, the better developed the temporal bone and the better developed the external auditory canal, the better hearing level. The hearing level also can serve as an indicator to determine whether a patient will be suitable for reconstructive surgery.

COUP-TFII is required for morphogenesis of the neural crest-derived tympanic ring

Chicken Ovalbumin Upstream Promoter-Transcription Factor II (COUP-TFII) plays pivotal roles in cell growth, cell differentiation, and cell fate determination. Although genome-wide studies have identified COUP-TFII binding on gene sets mainly involved in neural crest cell (NCC) development and craniofacial morphogenesis, the direct functional connection between COUP-TFII and NCCs in vivo has not been well characterized. In this study, we show that COUP-TFII is expressed in the subpopulation of NCCs and its derivatives, and targeted ablation of COUP-TFII in mouse NCCs results in markedly shortened and bifurcated tympanic rings, which in turn disturb the caudal direction of external acoustic meatus invagination. However, formation of the manubrium of the malleus (MM) in Wnt1-Cre/+;COUP-TFII^flox/flox mice is not perturbed, suggesting that the rostral half of the tympanic ring is sufficient to support proper MM development. Interestingly, we found that loss of COUP-TFII up-regulates Sox9 in the tympanic ring primordium and affects the distribution of preosteoblasts before mesenchymal condensation. Together, our results demonstrate that COUP-TFII plays an essential role in regulating the patterning of the NCC-derived tympanic ring.

Branchial cleft and pouch anomalies in childhood: a report of 50 surgical cases

BACKGROUND AND AIMS

Branchial abnormalities occur when there is disturbance in the maturation of the branchial apparatus during fetal development. Branchial anomalies are congenital lesions usually present in childhood, even if they can be diagnosed later for enlargement or infection. A correct diagnosis will lead to proper management: complete surgical excision is the treatment of choice. The purpose of this article is to present clinical features, diagnostic methods and surgical treatment of branchial anomalies in childhood, based on a series of 50 patients.

METHODS

We conducted a retrospective analysis of a total of 50 pediatric patients operated from June 2005 to June 2014 for the presence of branchial cleft anomalies.

RESULTS

27 cases (54 %) presented a second branchial cleft fistula and 11 cases (22 %) a second branchial cleft cyst and one case (2 %) presented both cyst and sinus of the second branchial cleft; four cases (8 %) presented first branchial cleft cyst whereas four cases (8 %) a first branchial cleft sinus and two cases (4 %) a first branchial cleft fistula; one case (2 %) presented a piriform sinus fistula (third branchial cleft). None of our patients presented anomalies of the fourth branchial cleft. All patients underwent surgical treatment and lesions have been removed by excision or fistulectomy. No post-surgical complication occurred. The rate of recurrence was 4 %.

CONCLUSIONS

Pre-operative diagnosis supplies important information to the surgeon for a proper therapy: a complete excision of the lesion without inflammatory signs is essential to avoid re-intervention and to achieve a good outcome.

Developmental mechanisms of the tympanic membrane in mammals and non-mammalian amniotes

The tympanic membrane is a thin layer that originates from the ectoderm, endoderm, and mesenchyme. Molecular-genetic investigations have revealed that interaction between epithelial and mesenchymal cells in the pharyngeal arches is essential for development of the tympanic membrane. We have recently reported that developmental mechanisms underlying the tympanic membrane seem to be different between mouse and chicken, suggesting that the tympanic membrane evolved independently in mammals and non-mammalian amniotes. In this review, we summarize previous studies of tympanic membrane formation in the mouse. We also discuss its formation in amniotes from an evolutionary point of view.

Development and Integration of the Ear

The perception of our environment via sensory organs plays a crucial role in survival and evolution. Hearing, one of our most developed senses, depends on the proper function of the auditory system and plays a key role in social communication, integration, and learning ability. The ear is a composite structure, comprised of the external, middle, and inner ear. During development, the ear is formed from the integration of a number of tissues of different embryonic origin, which initiate in distinct areas of the embryo at different time points. Functional connections between the components of the hearing apparatus have to be established and maintained during development and adulthood to allow proper sound submission from the outer to the middle and inner ear. This highly organized and intimate connectivity depends on intricate spatiotemporal signaling between the various tissues that give rise to the structures of the ear. Any alterations in this chain of events can lead to the loss of integration, which can subsequently lead to conductive hearing loss, in case of outer and middle ear defects or sensorineural hearing loss, if inner ear structures are defective. This chapter aims to review the current knowledge concerning the development of the three ear compartments as well as mechanisms and signaling pathways that have been implicated in the coordination and integration process of the ear.

Genetic syndromes involving hearing

OBJECTIVE

The fundamental processes involved in the mechanism of hearing seem to be controlled by hundreds of genes and hereditary hearing impairment may be caused by a large variety of genetic mutations in different genes. Approximately 150 loci for monogenic syndromic and non-syndromic hearing impairment (HI) disorders have been mapped to the human genome. The identification of these genes and functional analysis of the proteins they encode, are paving the way towards a better understanding of the physiology and pathophysiology of the auditory system. To date, approximately 50 causative genes have been identified.

METHODS

The clinical and neuroradioldical findings of syndromal hearing impairment are analysed.

RESULTS

This paper presents an updated report on genetic syndromes in which a hearing impairment is involved, with a particular attention to the ones associated with external ear and craniofacial malformations.

CONCLUSIONS

Concepts in human genetics are rapidly evolving together with technologies. The concept itself of gene is changing. A genetic diagnosis of syndromal hearing impairment has many practical consequences: it can implies specific prognosis, specific management, specific recurrence risk in relatives and, if the diagnosis is confirmed at the molecular level, possibility of a specific early prenatal diagnosis for severe syndromes. It is important to highlight the necessity that the pediatric otolaryngologist must have a close collaboration with a clinical geneticist and a neuroradiologist.

Microtia and congenital aural atresia

Microtia and congenital aural atresia (CAA) are congenital anomalies that are so common that every otolaryngologist should be familiar with the initial evaluation and care of the patient. When one ear hears normally, speech and language development should be normal. The gross and fine motor development of the baby or child is not expected to be affected in isolated cases of microtia and CAA. Current technologies allow for reconstruction or habilitation of the microtic ear when the child is several years of age. The hope is that tissue engineering can eliminate donor site morbidity. Temporary prosthetic ears will remain an option. Aural atresia work continues to be very dependent on the patient anatomy and the need or desire for better hearing in the affected ear.

Correlation between microtia and temporal bone malformation evaluated using grading systems

OBJECTIVE

To evaluate the relationships between temporal bone abnormalities and the severity of microtia in Japanese patients using objective grading systems.

DESIGN

Retrospective case series study conducted between 1992 and 2003.

SETTING

Academic, tertiary care, referral medical center.

PATIENTS

One hundred forty-two ears of 109 Japanese patients (85 male and 24 female patients; mean age, 12.8 years [range, 2-36 years]) with microtia.

MAIN OUTCOME MEASURES

The severity of microtia was classified according to Marx classification. Developmental abnormalities of the temporal bone were evaluated by a computed tomographic (CT) scoring system modified after the system used by Jahrsdoerfer and colleagues, using high-resolution CT scans of the temporal bone. Correlations between the scores obtained from these 2 grading systems were evaluated using a nonparametric statistical method.

RESULTS

Male preponderance and incidence of bilateral cases of approximately 30% were observed in our Japanese patients with microtia. There was no significant difference in the severity of microtia between unilateral and bilateral cases. The mean +/- SEM total points in the CT scoring system (full marks, 10) was 7.9 +/- 0.4 for grade I microtia, 6.6 +/- 0.6 for grade II, and 6.4 +/- 0.3 for grade III; the total points correlated inversely with the microtia grade. Development of the auricle correlated significantly with aeration in the middle ear spaces but not with ossicular development or formation of the oval/round windows. Proportion of acceptable surgical candidates according to the CT scoring system (>5 points) was 79% for grade I microtia, 52% for grade II microtia, and 65% for grade III microtia.

CONCLUSION

The principle "the better developed the auricle, the better developed middle ear" was confirmed in Japanese patients with microtia; however, even with grade II/III microtia, more than half of the patients were considered suitable for atresia surgery.

First branchial cleft sinus presenting with cholesteatoma and external auditory canal atresia

First branchial cleft abnormalities are rare. They may involve the external auditory canal and middle ear. We describe a 6-year-old girl with congenital external auditory canal atresia, microtia, and cholesteatoma of mastoid and middle ear in addition to the first branchial cleft abnormalities. Clinical features of the patient are briefly described and the embryological relationship between first branchial cleft anomaly and external auditory canal atresia is discussed. The surgical management of these lesions may be performed, both the complete excision of the sinus and reconstructive otologic surgery.

Duplication of the external auditory canal: a report of three cases

OBJECTIVE

Malformations of the first branchial cleft are uncommon and only sporadically reported in the literature. They may present as inflammatory openings on the neck, bland cysts or fistula associated with the external auditory canal. In this retrospective study, clinical features and anatomical relationships are described in three pediatric cases. Therapeutical guidelines for surgical management of first branchial cleft anomalies are discussed.

PATIENTS

Between 1997 and 1999 three patients aged 9 months, 2 and 7 years with first branchial cleft anomalies were included in this study. All patients were treated surgically, wide exposure and superficial parotidectomy was necessary for complete removal in two of three cases.

RESULTS

Exploring patients histories revealed previous infections with repeated incision and drainage procedures as well as inadequate operative resections. Clinically, purulent drainage from the ear, swelling in the parotid area and abscess formation with persistent drainage after incision in the neck or parotid area were noted.

CONCLUSIONS

From our case series two of three patients underwent inadequate incision and drainage procedures to combat infection followed by scar tissue formation. Because of the variable relation to the facial nerve this led to difficulties in identifying and protecting the nerve during definite surgery. Management of first branchial cleft anomalies must include the facilities to achieve ear surgery and superficial parotidectomy including facial nerve exposure.

Diagnosis and management strategies in congenital atresia of the external auditory canal. Study Group on Otological Malformations and Hearing Impairment

This consensus report represents a distillation of current opinion regarding diagnosis and management of congenital aural atresia. It also takes into account the philosophical differences which exist in Europe. Congenital aural atresia requires prompt diagnosis, genetic counselling and an early assessment of hearing. In bilateral atresia, early amplification with a bone conduction hearing aid is essential for proper speech development. Further rehabilitation in bilateral cases is managed with surgical reconstruction in selected patients or by implantation of a bone-anchored hearing aid. Atresia repair surgery is worthwhile if proper patient selection is made by use of stringent audiological and radiological criteria and state of the art surgery is performed. The divergent views concerning indications, ideal age for surgery and surgical approach to achieve better hearing are discussed. Review of the literature demonstrated that even in the hands of the best surgeons a mean hearing gain of only 20-25 dB is achieved in atresia Type II, with 30-35 dB in Type I. Therefore, surgical reconstruction should only be done in the more favourable cases where post-operative hearing of <25-30 dB is attainable. Less favoured patients should be helped with bone-anchored hearing aids, as this type of surgery does not interfere with the future use of new techniques.

Congenital aural atresia: stability of surgical results

OBJECTIVES/HYPOTHESIS

To compare early (<1 y) and longer-term (1.0-7.5 y; mean follow-up, 2.8 y) hearing results following surgery for congenital aural atresia and to analyze revision cases for cause of failure, time of occurrence, and outcome.

STUDY DESIGN

Retrospective study of 55 consecutive patients (59 ears) undergoing surgery during an 11-year period for congenital aural atresia.

METHODS

The best speech reception threshold (SRT) during the first postoperative year was compared with the most recent SRT beyond the first postoperative year. The complication rate and long-term hearing results (>1 y) for initial and revision surgeries were compared.

RESULTS

In the early postoperative period, an SRT of < or =25 dB was achieved in 60% and an SRT of < or =30 dB in 70%. With longer follow-up (mean, 2.8 y), 46% of patients maintained an SRT < or =25 dB. Revision surgery was necessary in approximately one third of patients. Longer-term hearing results following initial surgery only or after revision surgery showed an SRT < or =25 dB in 53% and an SRT < or =30 dB in 64%. For primary and revisions surgeries the incidence of temporary facial paralysis was 1.5% and for significant hearing loss, 3.0%.

CONCLUSIONS

Some degradation in hearing does occur as patients are followed beyond the first postoperative year. Revision surgery will be necessary in approximately one third of cases. With revisions, an SRT < or =25 dB can be expected in half of cases and an SRT < or =30 dB in two thirds of cases. The ability to provide these hearing results supports this surgery in unilateral cases.

Hoxa1 and Hoxb1 synergize in patterning the hindbrain, cranial nerves and second pharyngeal arch

The analysis of Hoxa1 and Hoxb1 null mutants suggested that these genes are involved in distinct aspects of hindbrain segmentation and specification. Here we investigate the possible functional synergy of the two genes. The generation of Hoxa1(3′RARE)/Hoxb1(3′RARE) compound mutants resulted in mild facial motor nerve defects reminiscent of those present in the Hoxb1 null mutants. Strong genetic interactions between Hoxa1 and Hoxb1 were uncovered by introducing the Hoxb1(3′RARE) and Hoxb1 null mutations into the Hoxa1 null genetic background. Hoxa1(null)/Hoxb1(3′RARE) and Hoxa1(null)/Hoxb1(null)double homozygous embryos showed additional patterning defects in the r4-r6 region but maintained a molecularly distinct r4-like territory. Neurofilament staining and retrograde labelling of motor neurons indicated that Hoxa1 and Hoxb1 synergise in patterning the VIIth through XIth cranial nerves. The second arch expression of neural crest cell markers was abolished or dramatically reduced, suggesting a defect in this cell population. Strikingly, the second arch of the double mutant embryos involuted by 10.5 dpc and this resulted in loss of all second arch-derived elements and complete disruption of external and middle ear development. Additional defects, most notably the lack of tympanic ring, were found in first arch-derived elements, suggesting that interactions between first and second arch take place during development. Taken together, our results unveil an extensive functional synergy between Hoxa1 and Hoxb1 that was not anticipated from the phenotypes of the simple null mutants.