Cochlear active mechanisms in young normal-hearing subjects affected by Williams syndrome: Time–frequency analysis of otoacoustic emissions

Peripheral Auditory Pathway and ABR Characterization in Adults with Williams Syndrome

Introduction  Williams syndrome (WS) is a genetic disorder caused by a microdeletion in chromosome 7, affecting ∼ 28 genes. Studies have demonstrated conductive losses seemingly related to the absence of the elastin gene and mild to profound sensorineural losses due to cochlear fragility. Objective  To characterize and compare the peripheral auditory system and auditory brainstem response (ABR) of adults with WS and neurotypical adults matched by age and gender. Methods  We conducted a cross-sectional observational study with 30 individuals of both sexes, aged 18 to 37 years - 15 of them with WS (study group) and 15 with neither the syndrome nor hearing complaints (control group), matched for sex and age. The subjects underwent pure-tone and speech audiometry, acoustic immittance, transient-evoked otoacoustic emissions (TEOAEs), and ABR. Results  Early-onset sensorineural hearing loss was found in 53.3% of the study sample, mostly mild, occurring above 3 kHz. The TEOAEs were absent in 53.3% of assessed subjects; for those in whom they were present, the signal-to-noise responses were significantly lower than in the control group. In the ABR, increased absolute latencies were observed in waves I and III. Conclusion  Individuals with WS have early and progressive cochlear impairments, mainly affecting the basal region of the cochlea. They may have low brainstem changes which seem to begin in adulthood.

Audiological profile and cochlear functionality in Williams syndrome

PURPOSE

to evaluate cochlear functionality in Williams syndrome (WS) individuals.

METHODS

a study with 39 individuals, being 22 with WS aged between 7 and 17 years, 15 male and 7 female, and 17 individuals with typical development and normal hearing. All individuals were evaluated using pure tone audiometry, acoustic immittance measurements, and Transient Evoked Otoacoustic Emissions (TEOAE). The audiological profile in individuals with WS was analyzed, and TEOAE responses were compared between WS individuals without hearing loss and typical developmental individuals.

RESULTS

The hearing loss was observed in 50% of patients, being 78.95% sensorineural and 21.05% mixed. This hearing loss was predominantly mild to moderate, affecting mainly frequencies above 3 kHz. As for TEOAE, there was a higher incidence of absence and lower amplitude responses in individuals with WS.

CONCLUSION

WS individuals have hair cell dysfunction, mainly in the basal region of the cochlea. Thus, TEOAE analysis is an important clinical resource to be considered in the routine audiological evaluation.

Denoising click-evoked otoacoustic emission signals by optimal shrinkage

Click-evoked otoacoustic emissions (CEOAEs) are clinically used as an objective way to infer whether cochlear functions are normal. However, because the sound pressure level of CEOAEs is typically much lower than the background noise, it usually takes hundreds, if not thousands, of repetitions to estimate the signal with sufficient accuracy. In this paper, we propose to improve the signal-to-noise ratio (SNR) of CEOAE signals within limited measurement time by optimal shrinkage (OS) in two different settings: covariance-based optimal shrinkage (cOS) and singular value decomposition-based optimal shrinkage (sOS). By simulation, the cOS consistently enhanced the SNR by 1-2 dB from a baseline method that is based on calculating the median. In real data, however, the cOS cannot enhance the SNR over 1 dB. The sOS achieved a SNR enhancement of 2-3 dB in simulation and demonstrated capability to enhance the SNR in real recordings. In addition, the level of enhancement increases as the baseline SNR decreases. An appealing property of OS is that it produces an estimate of all single trials. This property makes it possible to investigate CEOAE dynamics across a longer period of time when the cochlear conditions are not strictly stationary.

Características da avaliação auditiva na síndrome de Williams: revisão sistemática

RESUMO Objetivo Identificar por meio de uma revisão sistemática da literatura quais são as características da avaliação audiológica clínica de indivíduos com síndrome de Williams. Estratégia de pesquisa Inicialmente foi determinada a seguinte pergunta de pesquisa: “Quais são as características da avaliação auditiva clínica em indivíduos com síndrome de Williams?”. A partir desta, foi realizado um levantamento bibliográfico em 4 bases de dados, utilizando-se dos seguintes descritores: síndrome de Williams (Williams syndrome), perda auditiva (hearing loss) e audiologia (audiology). Critérios de seleção Foram selecionados artigos com nível de evidência 1 ou 2, publicados na íntegra nos idiomas português brasileiro ou inglês. Análise dos dados Foram analisados os resultados obtidos nos testes auditivos utilizados na rotina clínica, incluindo: imitanciometria, audiometria tonal, emissões otoacústicas e potencial evocado auditivo de tronco encefálico. Resultados 209 estudos foram encontrados, porém apenas 12 contemplaram os critérios de inclusão para o estudo. Foi possível observar prevalência de curva timpanométrica do tipo A, que pode ocorrer juntamente com ausência de reflexos acústicos, perda auditiva neurossensorial de grau leve a moderado acometendo principalmente as frequências altas, emissões otoacústicas ausentes ou de menor amplitude e potencial evocado auditivo de tronco encefálico sem alteração retrococlear. Conclusão O comprometimento coclear é comum em indivíduos com síndrome de Williams e as principais alterações na avaliação auditiva nesta população são a ausência das emissões otoacústicas e dos reflexos acústicos bem como a presença de perda auditiva neurossensorial de grau leve a moderado principalmente nas frequências altas na audiometria tonal.

Extraction of Cochlear Non-linearities with the Bispectral Analysis

Objectives: Transient Otoacoustic Emission (TEOAEs) are low intensity sounds generated by active mechanisms in the cochlea and elicited by broadband and short acoustic stimuli. TEOAEs are a quick, non-invasive, and very reliable measure to objectively assess the peripheral auditory system. In the current study, we present a recent technique to extract and evaluate non-linearities in TEOAEs, and apply it for the preliminary analysis of TEOAE recordings of a group of worker of a fiberglass manufacturing facility exposed to styrene solvent.

Methods: Bispectral analysis was applied to TEOAEs to extract the quadratic frequency couplings (QFCs) in TEOAEs. Amplitude of QFCs was calculated in a group of 7 styrene-exposed workers (14 ears) and compared with normative results obtained on normal hearing young adults.

Results: Difference in amplitude of QFCs were found between workers and controls. In workers, TEOAE non-linear components were found in the 1.5 – 4 kHz frequency range, whereas in control subjects they were found in a lower frequency region, ranging from 1 to 3 kHz.

Conclusion: The amplitude of QFCs highlighted differences in TEOAEs recorded among workers and controls.

Analysis of subtle auditory dysfunctions in young normal-hearing subjects affected by Williams syndrome

OBJECTIVE

To assess if young subjects affected by Williams syndrome (WS) with normal middle ear functionality and normal hearing thresholds might have subtle auditory dysfunctions that could be detected by using clinically available measurements.

METHODS

Otoscopy, acoustic reflexes, tympanometry, pure-tone audiometry, and distortion product otoacoustic emissions (DPOAEs) were measured in a group of 13 WS subjects and in 13 age-matched, typically developing control subjects. Participants were required to have normal otoscopy, A-type tympanogram, normal acoustic reflex thresholds, and pure-tone thresholds≤15 dB HL at 0.5, 1, and 2 kHz bilaterally. To limit the possible influence of middle ear status on DPOAE recordings, we analyzed only data from ears with pure-tone thresholds≤15 dB HL across all octave frequencies in the range 0.25-8 kHz, middle ear pressure (MEP)>-50 daPa, static compliance (SC) in the range 0.3-1.2 cm3, and ear canal volume (ECV) in the range 0.2-2 ml, and we performed analysis of covariance to remove the possible effects of middle ear variables on DPOAEs.

RESULTS

No differences in mean hearing thresholds, SC, ECV, and gradient were observed between the two groups, whereas significantly lower MEP values were found in WS subjects as well as significantly decreased DPOAEs up to 3.2 kHz after adjusting for differences in middle ear status.

CONCLUSIONS

Results revealed that WS subjects with normal hearing thresholds (≤15 dB HL) and normal middle ear functionality (MEP>-50 daPa, SC in the range 0.3-1.2 cm3, ECV in the range 0.2-2 ml) might have subtle auditory dysfunctions that can be detected by using clinically available methods. Overall, this study points out the importance of using otoacoustic emissions as a complement to routine audiological examinations in individuals with WS to detect, before the onset of hearing loss, possible subtle auditory dysfunctions so that patients can be early identified, better monitored, and promptly treated.

The role of GTF2IRD1 in the auditory pathology of Williams-Beuren Syndrome

Williams-Beuren Syndrome (WBS) is a rare genetic condition caused by a hemizygous deletion involving up to 28 genes within chromosome 7q11.23. Among the spectrum of physical and neurological defects in WBS, it is common to find a distinctive response to sound stimuli that includes extreme adverse reactions to loud, or sudden sounds and a fascination with certain sounds that may manifest as strengths in musical ability. However, hearing tests indicate that sensorineural hearing loss (SNHL) is frequently found in WBS patients. The functional and genetic basis of this unusual auditory phenotype is currently unknown. Here, we investigated the potential involvement of GTF2IRD1, a transcription factor encoded by a gene located within the WBS deletion that has been implicated as a contributor to the WBS assorted neurocognitive profile and craniofacial abnormalities. Using Gtf2ird1 knockout mice, we have analysed the expression of the gene in the inner ear and examined hearing capacity by evaluating the auditory brainstem response (ABR) and the distortion product of otoacoustic emissions (DPOAE). Our results show that Gtf2ird1 is expressed in a number of cell types within the cochlea, and Gtf2ird1 null mice showed higher auditory thresholds (hypoacusis) in both ABR and DPOAE hearing assessments. These data indicate that the principal hearing deficit in the mice can be traced to impairments in the amplification process mediated by the outer hair cells and suggests that similar mechanisms may underpin the SNHL experienced by WBS patients.

Williams syndrome: ophthalmological examination and review of systemic manifestations

PURPOSE

To evaluate the frequency and severity of ophthalmic manifestations and associated diseases, as well as the epidemiological data in patients with Williams syndrome.

METHODS

The authors prospectively studied 30 patients clinically diagnosed as having Williams syndrome as confirmed by the fluorescence in situ hybridization test. Patient history included gender, age, race, education level, previous illnesses, and surgeries. The ophthalmologic examination included best-corrected visual acuity, dynamic and static refraction, extraocular motility test, stereopsis test (Titmus and Lang), and direct and indirect funduscopy.

RESULTS

Thirty patients were included in this study. The mean age was 14.5 ± 1.38 years (range: 7 to 26 years). Fifty percent of the patients were male and 50% were female. Among the children examined, 77% had a refractive error. Hyperopia and astigmatism were noted in 67% and 20% of the patients, respectively, and myopia in 7%. Only one case of amblyopia was noted. On external examination, 23% of children had epicanthus; via biomicroscopy, 3 children with stellate patterns of the irides were observed. Eleven patients (36.6%) had measurable strabismus, 9 (82%) had esotropia, and 2 (18%) had exotropia. Binocular vision was abnormal in 43% of patients. Diffuse arteriovenous tortuosity on funduscopy was observed in 27% of patients.

CONCLUSIONS

Williams syndrome is rare and is associated with multiple phenotypes and diseases that are susceptible to treatment. Multidisciplinary clinical management is critical and, in some cases, surgical intervention is required.

A bispectral approach to analyze nonlinear cochlear active mechanisms in transient evoked otoacoustic emissions

A new approach to study nonlinearity in cochlear active mechanisms, as evaluated in transient evoked otoacoustic emissions (TEOAEs), is presented. TEOAEs are signals generated in the cochlea by a mix of linear and nonlinear mechanisms. This new approach was designed to complement the traditional TEOAE analysis performed by currently available systems used in objective hearing screening and assessment. Nonlinearity of TEOAEs was studied by means of the bispectrum, which is able to find out quadratic frequency couplings (QFCs) that occur when a frequency is not only generated by an independent cochlear source, but it is the result of the interaction among a number of cochlear sources. To fit with the technical constraints of currently available TEOAE systems, the bispectrum was estimated by the third-order scaled polyperiodogram. The proposed method was characterized with synthesized TEOAEs as a function of the main TEOAE parameters and then used to analyze TEOAEs recorded in normal hearing adults and full-term neonates. Results revealed the presence of QFCs in both adult and neonatal TEOAEs, with peculiar patterns and significantly different frequency content in the two groups: adults had QFCs mainly around 2 kHz and neonates had QFCs mainly in the range 3.5-4 kHz.

Time-frequency analysis of transient-evoked otoacoustic emissions in children exposed to carboplatin chemotherapy

The aims of this study were to characterize and quantify time-frequency changes in transient-evoked otoacoustic emissions (TEOAEs) recorded in children diagnosed with retinoblastoma who were receiving carboplatin chemotherapy. A signal processing technique, the wavelet transform (WT), was used to analyze TEOAE waveforms in narrow-band frequency components. Ten children (aged 3-72 months) diagnosed with unilateral or bilateral retinoblastoma were enrolled in the study. TEOAEs were acquired from the children with linear sequences of 70 dB peak equivalent SPL clicks. After WT analysis, TEOAE energy, latency and normalized energy in the narrow-band frequency components were compared before and during carboplatin chemotherapy treatment (average dose 1693 mg/m2). On a group basis, no significant differences (p>0.05) in the TEOAE energy, latency or normalized energy before and after carboplatin treatment were observed. There were decreases in normalized energy on an individual basis in 10 out of 18 ears in the sample. Exposure to carboplatin chemotherapy did not cause significant changes in TEOAE energy, latency and normalized energy during treatment. However, long-term monitoring of hearing with measurements of TEOAEs is warranted, given the risks of delayed hearing loss in some children receiving carboplatin chemotherapy.

Linking LIMK1 deficiency to hyperacusis and progressive hearing loss in individuals with Williams syndrome

Williams syndrome (a.k.a. Williams-Beuren Syndrome) is a multisystem disorder caused by the hemizygous deletion of a 1.6 Mb region at 7q11.23 encompassing about 26 genes, including that encoding LIM kinase 1 (LIMK1). Individuals with Williams Syndrome manifest hyperacusis and progressive hearing loss, and hyperacusis early onset suggests that it could be associated with one of the deleted genes. Based on our results about the critical role of LIM kinases in the regulation of the motile responses of cochlear outer hair cells (OHC) and cochlear amplification, we propose here that a reduced expression of LIMK1 in OHC would be the major underlying cause of the hyperacusis and progressive hearing loss observed in patients with Williams Syndrome. Moreover, we propose a novel model of gain-control for cochlear amplification based on LIMK-mediated regulation of OHC's slow motility.