External auditory canal stenosis and partial atresia without associated anomalies

[Atresia or severe stenosis of the external auditory canals with normal auricles in children]

In the article we present the experience of observing 27 children with bilateral stenosis or atresia of the external auditory canals with normal or slightly hypoplastic auricles. Three children had bilateral stenosis of the external auditory canals due to abnormal or premature fusion of the skull bones. The remaining 24 children had external auditory canals atresia in the bone part or throughout. 9 of them had a syndrome of deletion of the long arm of chromosome 18, 1 child had a mosaic form of Edwards syndrome. The average age at the time of diagnosis was 4 years 3 months. Atresia of external auditory canals in normal auricle is often caused by abnormalities of 18 pairs of chromosomes, and severe stenosis of external auditory canals can be observed in children with craniostenosis and other anomalies of the skull bones.

Hearing impairment in murine model of Down syndrome

Hearing impairment is a cardinal feature of Down syndrome (DS), but its clinical manifestations have been attributed to multiple factors. Murine models could provide mechanistic insights on various causes of hearing loss in DS. To investigate mechanisms of hearing loss in DS in the absence of the cadherin 23 mutation, we backcrossed our DS mice, Dp(16)1Yey, onto normal-hearing CBA/J mice and evaluated their auditory function. Body weights of wild type (WT) and DS mice were similar at 3-months of age, but at 9-months, WT weighed 30% more than DS mice. Distortion product otoacoustic emissions (DPOAE), a test of sensory outer hair cell (OHC) function negatively impacted by conductive hearing loss, were reduced in amplitude and sensitivity across all frequencies in DS mice. The middle ear space in DS mice appeared normal with no evidence of infection. MicroCT structural imaging of DS temporal bones revealed a smaller tympanic membrane diameter, oval window, and middle ear space and localized thickening of the bony otic capsule, but no gross abnormalities of the middle ear ossicles. Histological analysis of the cochlear and vestibular sensory epithelium revealed a normal density of cochlear and vestibular hair cells; however, the cochlear basal membrane was approximately 0.6 mm shorter in DS than WT mice so that the total number of hair cells was greater in WT than DS mice. In DS mice, the early and late peaks in the auditory brainstem response (ABR), reflecting neural responses from the cochlear auditory nerve followed by subsequent neural centers in the brainstem, were reduced in amplitude and ABR thresholds were elevated to a similar degree across all frequencies, consistent with a conductive hearing impairment. The latency of the peaks in the ABR waveform were longer in DS than WT mice when compared at the same intensity; however, the latency delays disappeared when the data were compared at the same intensity above thresholds to compensate for the conductive hearing loss. Future studies using wideband tympanometry and absorbance together with detailed histological analysis of the middle ear could illuminate the nature of the conductive hearing impairment in DS mice.

Otologic characteristics of individuals with deletions of distal 18q

OBJECTIVES/HYPOTHESIS

To fully describe the otologic features seen in individuals with deletions of the distal long arm of chromosome 18 (distal 18q-).

STUDY DESIGN

Cross-sectional/observational.

METHODS

More than 200 individuals with deletions of the long arm of chromosome 18 underwent a complete otologic and audiologic examination. In addition, chromosome microarray analysis to determine the chromosome copy number was completed for all participants. Overall, 113 subjects had clinical and audiological data to be reported here.

RESULTS

Sixty-six percent of this population had aural stenosis or atresia. No subject had microtia. In the 53 individuals for whom serial data was available, enlargement of ear canal diameter was seen in 48% of ears with stenosis, examined over time. Abnormalities of the palate were seen in nearly 18% of patients and included complete or incomplete clefts of the palate, submucous clefts, and velopharyngeal insufficiency. A conductive hearing impairment was identified in 112 ears (49.5%), and sensorineural hearing loss was identified in 28%. Eustachian tube dysfunction was common and found in 78% of ears examined.

CONCLUSIONS

The otologic phenotype varies widely among individuals with distal 18q-. External auditory canal stenosis without microtia is a hallmark of the disease. Hearing impairment is also very common, with both sensorineural losses and conductive losses contributing to morbidity. Moreover, the critical region for sensorineural hearing loss will aid in the identification of the gene responsible for this aspect of the distal 18q- phenotype.

LEVEL OF EVIDENCE

4.

Down syndrome: an electrophysiological and radiological profile

OBJECTIVES/HYPOTHESIS

To assess the hearing status of trisomy 21 patients by analyzing electrophysiological and radiological findings of any correlation between hearing impairment and major or minor inner ear malformations.

STUDY DESIGN

Prospective radiological and electrophysiological study.

METHODS

A group of 34 ears of Down syndrome subjects and 20 ears of a volunteer age- and sex-matched control group of 10 normal subjects were studied electrophysiologically by means of otoacoustic emissions and auditory brainstem response. Temporal bone computed tomography (CT) scans were carried out in both groups; radiological findings were compared. Inner ear structure measurements were applied attempting to disclose subtle bony labyrinthine anomalies. The findings from both groups were statistically analyzed employing the t test.

RESULTS

The rate of sensorineural hearing loss (SNHL) in Down syndrome group was 41%. Temporal bone CT scans showed no ossicular malformation in all Down syndrome cases. Major inner ear abnormalities were disclosed in 5.8%; they corresponded to two cases of lateral semicircular canal dysplasia detected on CT images by visual inspection. The application of various inner ear structure measurements increased the overall detection rate of common inner ear malformations to 47%. A statistically significant correlation was found between hearing level and vestibule length (P = .009) and internal auditory canal length (P = .028). Vestibular aqueduct width was correlated to different otic abnormalities.

CONCLUSIONS

SNHL is mainly secondary to the underestimated subtle inner ear malformations that are adequately demonstrated by adopting standardized inner ear structure measurements on petrous bone imaging. Vestibular height and internal auditory canal length were correlated to SNHL.

LEVEL OF EVIDENCE

3b.

Association of external auditory canal atresia, vertical talus, and hypertelorism: confirmation of Rasmussen syndrome

In 1979, Rasmussen et al. reported six members of a family with congenital, bilateral, symmetrical, and isolated subtotal atresia of the external auditory canal, bilateral foot abnormalities, and increased interocular distance. The family history suggested autosomal dominant inheritance of the syndrome. We report a 3-year-old girl whose symptoms are compatible with this diagnosis. Therefore, we suggest confirmation of the description by Rasmussen et al. as a distinct entity and suggest the term Rasmussen syndrome for this condition.

Clinical and radiological evaluation in children with microtia

The management of a child with congenital ear malformation, in particular if the external ear is severely involved, is difficult because of the complexity of the therapeutic problem, and that of parental anxiety. It is very important to plan a complete therapeutic/habilitative programme as soon as possible, even if surgical procedures are delayed. Diagnostic imaging plays an important role in the global assessment of a child with microtia, in order to diagnose possible associated external auditory canal, middle and inner ear malformations. For these reasons our diagnostic protocol for children with microtia includes otological and audiological evaluation, clinical genetics and radiological imaging, from the neonatal period. Here, data are reported on 27 children with microtia who completed the diagnostic protocol. In eight of 27 cases microtia was bilateral: in unilateral cases the right side was affected more frequently. Other congenital malformations were diagnosed in 41% of cases. A high correlation between the degree of microtia and the frequency of external and middle ear dysplasias was found, in accordance with larger studies of the literature. Inner ear malformations were found less frequently, but without apparent correlation with the degree of microtia. The fact that children with microtia may also have severe inner ear malformations is emphasized.