Congenital Aural Atresia in 18q Deletion or de Grouchy Syndrome

Canalization and maintaining the patency of external auditory canal in a congenital aural atresia patient: a multidisciplinary approach

This clinical report describes the role of a prosthodontist in rehabilitating a patient with congenital aural atresia. The external auditory canal and structure in the middle ear fail to develop completely in cases of congenital aural atresia. Canalization procedure to establish the communication between the external ear and middle ear, and maintaining the patency of the created canal plays an important role in the success of treatment in selected patients. Post Operative external auditory canal restenosis is the most common complication after congenital aural atresia surgery. The prosthodontist has an important role in assisting ENT surgeons in canalization procedure and also maintaining the patency of the canal during healing phase.

Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans

Congenital aural atresia (CAA) can occur as an isolated congenital malformation or in the context of a number of monogenic and chromosomal syndromes. CAA is frequently seen in individuals with an 18q deletion, which is characterized by intellectual disability, reduced white-matter myelination, foot deformities, and distinctive facial features. Previous work has indicated that a critical region for CAA is located in 18q22.3. We studied four individuals (from two families) with CAA and other features suggestive of an 18q deletion, and we detected overlapping microdeletions in 18q22.3 in both families. The minimal region of deletion overlap (72.9-73.4 Mb) contained only one known gene, TSHZ1, which was recently shown to be important for murine middle-ear development. Sequence analysis of the coding exons in TSHZ1 in a cohort of 11 individuals with isolated, nonsyndromic bilateral CAA revealed two mutations, c.723G>A (p.Trp241X) and c.946_947delinsA (p.Pro316ThrfsX16), and both mutations predicted a loss of function. Together, these results demonstrate that hemizygosity of TSHZ1 leads to congenital aural atresia as a result of haploinsufficiency.

The 18q deletion syndrome and analysis of the critical region for orofacial cleft at 18q22.3

INTRODUCTION

The 18q deletion syndrome (18q-) is a multiple-anomaly disorder associated with mental retardation, white matter anomalies in the brain, growth hormone deficiency, congenital aural atresia, orofacial cleft (OFC), and palate abnormalities. The aims of this study were to determine the frequency of different forms of OFC in 18q- individuals: cleft palate with or without cleft lip (CP/L), cleft lip (CL), and palate abnormalities. We also sought to map a potential critical region for OFC within chromosome 18q22.3 region.

PATIENTS

The study presents an overview of selected 18q- individuals from 11 published reports and one presented poster.

RESULTS

The frequency of CP/L and CL among 18q- individuals is about 25%; when high/arched palate cases are included, the frequency rises to about 43%.

CONCLUSION

Orofacial abnormalities are characteristic features of 18q- syndrome patients and potential CP/L critical region could be assumed at 18q22.3 between markers D18S879 and D18S1141. In addition, gene deficient mouse models for Sall3 or Tshz1 genes, which are located at the 18q22.3 critical region, displayed palate abnormality phenotype.

Genotype-phenotype mapping of chromosome 18q deletions by high-resolution array CGH: an update of the phenotypic map

Partial deletions of the long arm of chromosome 18 lead to variable phenotypes. Common clinical features include a characteristic face, short stature, congenital aural atresia (CAA), abnormalities of the feet, and mental retardation (MR). The presence or absence of these clinical features may depend on the size and position of the deleted region. Conversely, it is also known that patients whose breakpoints are localized within the same chromosome band may exhibit distinct phenotypes. New molecular techniques such as array CGH allow for a more precise determination of breakpoints in cytogenetic syndromes, thus leading to better-defined genotype-phenotype correlations. In order to update the phenotypic map for chromosome 18q deletions, we applied a tiling resolution chromosome 18 array to determine the exact breakpoints in 29 patients with such deletions. Subsequently, we linked the genotype to the patient's phenotype and integrated our results with those previously published. Using this approach, we were able to refine the critical regions for microcephaly (18q21.33), short stature (18q12.1-q12.3, 18q21.1-q21.33, and 18q22.3-q23), white matter disorders and delayed myelination (18q22.3-q23), growth hormone insufficiency (18q22.3-q23), and CAA (18q22.3). Additionally, the overall level of MR appeared to be mild in patients with deletions distal to 18q21.33 and severe in patients with deletions proximal to 18q21.31. The critical region for the 'typical' 18q-phenotype is a region of 4.3 Mb located within 18q22.3-q23. Molecular characterization of more patients will ultimately lead to a further delineation of the critical regions and thus to the identification of candidate genes for these specific traits.

Mapping susceptibility gene locus for IgA deficiency at del(18)(q22.3?q23); report of familial cryptic chromosome t(18q; 10p) translocations

This study presents a clinical report of the Finnish chromosome t(18q; 10p) translocation family with an overview of eight other selected immunoglobulin A (IgA)-deficient 18q deletion (18q-) patients from seven published articles. The family members show features common to 18q- syndrome such as mental retardation, multiple facial dysmorphism, foot/hand deformities, abnormal myelination of brain white matter, and a spectrum of immunological/infectious disorders including IgA deficiency (IgAD). Genotype-phenotype correlation study of the unbalanced t(18q-; 10p+) translocation family members and other 18q- syndrome reports led to definition of a potential susceptibility gene locus for IgAD at distal region of 18q22.3-q23 between markers D18S812-18qter. The haplo-insufficiency of the 18q22.3-q23 gene region is suggested to be a cause of the IgAD phenotype in 18q- individuals. This 7 Mb IgAD critical region shows significant association with susceptibility region for celiac disease that is frequently connected to IgAD.

Preoperative evaluation of the congenital aural atresia on computed tomography; an analysis of the severity of the deformity of the middle ear and mastoid

OBJECTIVE

To compare the development of temporal bone in normal and atretic ears and to assess some radiological landmarks that could be important in the hearing restoration interventions in such patients.

MATERIAL AND METHODS

Thirty-five patients with 40 atretic external ears were evaluated with temporal bone CT and compared to a control group of 40 normal ears retrospectively. Using comparable slice levels in all patients, the course and the caliper of the facial canal, the surface area of the incus and malleus, the level of mastoid aeration, the location and anteroposterior diameters of the jugular bulb and sigmoid sinus, the direction and the caliber of the tympanic bony part of the Eustachian tube, area of the middle ear cavity, distance from facial nerve to incudomalleolar joint, to the vestibule and to the jugular bulb were included in the assessment. Non-parametric and parametric statistical tests were used for comparison.

RESULTS

In atretic ears middle ear sectional area was found to be smaller at the equivalent plane as compared to control subjects (mean area index: 19.3mm(2) versus 47.4mm(2)). Mastoid aeration was low in general and the ossicles in the atretic ears were hypoplastic (mean ossicular sectional area: 8.3mm(2) versus 11 mm(2)). The distance from the jugular bulb to the facial nerve was significantly lower (mean: 6.2mm versus 6.8mm) (p<0.05) in the atretic ears. Facial canal caliber, distance from the facial canal to the incudomalleolar joint and distance from the facial canal to the vestibule in the atretic ears (means: 1.49, 2.93 and 1.82, respectively) did not show statistically significant difference from the control subjects (means: 1.44, 2.91 and 1.83, respectively) (p>0.05 for all).

CONCLUSION

External ear atresia is significantly associated with middle ear and mastoid abnormalities. The ossicles were underdeveloped which always have to be considered during reconstructive surgery. Radiologically, in the atretic ears anterior-posterior length of the temporal bone was more influenced as compared to superior-inferior portion, which justifies abnormal route of the facial nerve canal. However, there is no abnormality in the development of the facial nerve as the caliper is similar to the control subjects.

Identification of 2.3-Mb Gene Locus for Congenital Aural Atresia in 18q22.3 Deletion

OBJECTIVE

18q deletion syndrome is a multiple-anomaly mental retardation syndrome associated with congenital aural atresia. The purpose of this study was to determine the frequency of the congenital aural atresia phenotype in 18q deletion syndrome patients and to delineate a potential critical region for congenital aural atresia at the 18q22.3-18q23 region.

STUDY DESIGN AND PATIENTS

The study describes one 18q deletion syndrome clinical report (Patient 15) with an overview of 19 other selected 18q deletion syndrome patients presenting congenital aural atresia from 18 published articles and one presented poster on 18q deletion syndrome.

RESULTS

Our investigation, together with the results of published 18q deletion syndrome reports, shows that the average frequency of congenital aural atresia is approximately 52%. A combination of three 18q deletion syndrome probands defines a chromosomal deletion site for congenital aural atresia at 18q22.3-18q23 in the region between markers D18S489 and D18S554. These polymorphic markers outline a putative critical interval of approximately 2.3 Mb, including the genes ZNF407, ZADH2, SDCCAG33, ZNF516, FLJ44881, ZNF236, MBP-Golli, and GALR1. The haploinsufficiency of these genes is suggested to be a primary cause of congenital aural atresia phenotype in 18q deletion syndrome individuals.

CONCLUSION

Congenital aural atresia is a relevant diagnostic clue and a major recognizable feature of 18q deletion syndrome. Early diagnosis of 18q deletion syndrome may enable application of hearing aids. Knockout studies on the congenital aural atresia mouse gene homolog may add further insight into the genes responsible for this condition.

The BAHA Softband. A new treatment for young children with bilateral congenital aural atresia

OBJECTIVE

To evaluate the validity of a bone-anchored hearing aid (BAHA) Softband (fitted unilaterally and bilaterally) in young children with bilateral congenital aural atresia.

SUBJECTS

Two children with severe bilateral congenital conductive hearing loss, who had been fitted with a transcutaneous BAHA Softband at the age of 3 and 28 months, respectively. The latter child had been fitted with a conventional bone-conduction hearing aid at the age of 3 months; at 28 months, this child had received the BAHA Softband and after 5 months of unilateral application, the BAHA Softband was fitted bilaterally. Follow-up in the two children was 31 and 17 months, respectively.

METHODS

Using the artificial mastoid, gain and maximum output were studied in this new transcutaneous application of the BAHA, with the BAHA Classic and the BAHA Compact as sound processor. Results were compared to those obtained with a conventional bone-conduction device (Oticon E 300 P). Aided thresholds and sound lateralization scores were assessed with double visual reinforcement audiometry (VRA). To test the validity of the BAHA Softband, the speech and language development of the children was assessed by means of age-appropriate tests (the preverbal Symbolic play test and the Dutch non-speech test for receptive and expressive language and the Dutch version of the Reynell language test).

RESULTS

The electro-acoustic measurements showed minor differences in gain between the three devices. At a reduced volume setting, the mean input level at which the output levelled off was largely comparable between the BAHA Classic and the conventional device, but somewhat poorer with the BAHA Compact. Both children showed speech and language development that was in accordance with their cognitive development.

CONCLUSIONS

The BAHA Softband was a valid intervention in children with congenital bilateral aural atresia who were too young for percutaneous BAHA application.

A new syndrome within the oculo-auriculo-vertebral spectrum: microtia, atresia of the external auditory canal, vertebral anomaly, and complex cardiac defects

We describe a patient whose features represent a new entity within the oculo-auriculo-vertebral spectrum. The boy had right microtia, atresia of the external auditory canal, growth retardation, a complex heart defect, and extra-lobar pulmonary sequestration. The cardiac anomalies were persistent left superior vena cava, aortic stenosis, bicuspid aortic valves and subaortic membrane. Spinal films revealed complete fusion of the C2-C3 and C5-C6 vertebrae, and scoliosis of the lumbar spine. The patient's mental development was normal, and there were no abnormalities on ophthalmological examination. This report, reviews features of similar published cases, and argues why this may represent a 'new' entity within the oculo-auriculo-vertebral spectrum. The cardinal features are microtia, atresia of the external auditory canal, complex cardiac defects, growth retardation, normal mental and motor development in most cases and vertebral anomalies. All six of the patients reviewed were male raising the possibility of X-linked inheritance.

Definition of a critical region on chromosome 18 for congenital aural atresia by arrayCGH

Deletions of the long arm of chromosome 18 occur in approximately 1 in 10,000 live births. Congenital aural atresia (CAA), or narrow external auditory canals, occurs in approximately 66% of all patients who have a terminal deletion 18q. The present report describes a series of 20 patients with CAA, of whom 18 had microscopically visible 18q deletions. The extent and nature of the chromosome-18 deletions were studied in detail by array-based comparative genomic hybridization (arrayCGH). High-resolution chromosome-18 profiles were obtained for all patients, and a critical region of 5 Mb that was deleted in all patients with CAA could be defined on 18q22.3-18q23. Therefore, this region can be considered as a candidate region for aural atresia. The array-based high-resolution copy-number screening enabled a refined cytogenetic diagnosis in 12 patients. Our approach appeared to be applicable to the detection of genetic mosaicisms and, in particular, to a detailed delineation of ring chromosomes. This study clearly demonstrates the power of the arrayCGH technology in high-resolution molecular karyotyping. Deletion and amplification mapping can now be performed at the submicroscopic level and will allow high-throughput definition of genomic regions harboring disease genes.