Electrophysiological exploration of hearing

An eight-year follow-up on auditory outcomes after neonatal hearing screening

OBJECTIVE

The aim of this study is to assess the neonatal click Auditory Brainstem Response (ABR) results in relation to the subsequently determined mean hearing loss (HL) over 1, 2 and 4 kHz, as well as over 2 and 4 kHz.

METHODS

Between 2004-2009, follow-up data were collected from Visual Reinforcement Audiometry (VRA) at 1 and 2 years and playaudiometry at 4 and 8 years of newborns who had failed neonatal hearing screening in the well-baby clinics and who had been referred to a single Speech and Hearing center. Hearing Level data were compared with ABR threshold-levels established during the first months of life. The Two One-Sided Tests equivalence procedure for paired means was applied, using a region of similarity equal to 10 dB.

RESULTS

Initially, in 135 out of 172 children referred for diagnostic procedures hearing loss was confirmed in the neonatal period. In 106/135 of the HL children the eight-year follow-up was completed. Permanent conductive HL was established in 5/106 cases; the hearing thresholds were predominantly stable over time. Temporary conductive HL was found in 48/106 cases and the loss disappeared by 4 years of age at the latest. Sensorineural hearing loss (SNHL) was found in 53/106 cases, of which 13 were unilateral and 40 bilateral. ABR levels were equivalent (within a 10 dB range) to VRA levels at age 1 and 2 and play audiometry levels at age 4 and 8, both when VRA and play audiometry were averaged over both frequency ranges.

CONCLUSION

Long term follow-up data of children with SNHL suggest that the initial click ABR level established in the first months of life, are equivalent to the hearing threshold measured at the age of 1, 2, 4 and 8 years for both mean frequency ranges. Click ABR can reliably be used as starting point for long-term hearing rehabilitation.

Clinical Assessment Tools for the Detection of Cognitive Impairment and Hearing Loss in the Ageing Population: A Scoping Review

Objective

There is a strong association between cognitive impairment and hearing loss, both highly prevalent in the ageing population. Early detection of both hearing loss and cognitive impairment is essential in the management of these conditions to ensure effective and informed decisions on healthcare. The main objective was to identify existing and emerging cognitive and auditory assessment tools used in clinical settings (eg, memory clinics, audiology clinics), which manage the ageing population.

Methods

A scoping review of peer-reviewed publications and results were reported according to the PRISMA-ScR guidelines.

Results

A total of 289 articles were selected for data extraction. The majority of studies (76.1%) were conducted in 2017 or later. Tests of global cognitive function (ie, Mini-Mental State Exam, Montreal Cognitive Assessment) were the most commonly used method to detect cognitive impairment in hearing healthcare settings. Behavioral hearing testing (ie, pure-tone audiometry) was the most commonly used method to detect hearing loss in cognitive healthcare settings. Objective, physiological measures were seldom used across disciplines.

Conclusion

Preferences among clinicians for short, accessible tests likely explain the use of tests of global cognitive function and behavioral hearing tests. Rapidly evolving literature has identified inherent limitations of administering global cognitive function tests and pure-tone testing in an ageing population. Using electrophysiological measures as an adjunct to standard methods of assessment may provide more reliable information for clinical recommendations in those with cognitive and hearing impairment, and subsequently achieve better healthcare outcomes.

Real-Time Feature Extraction From Electrocochleography With Impedance Measurements During Cochlear Implantation Using Linear State-Space Models

Electrocochleography (ECochG) is increasingly used to monitor the inner ear function of cochlear implant (CI) patients during surgery. Current ECochG-based trauma detection shows low sensitivity and specificity and depends on visual analysis by experts. Trauma detection could be improved by including electric impedance data recorded simultaneously with the ECochG. However, combined recordings are rarely used because the impedance measurements produce artifacts in the ECochG. In this study, we propose a framework for automated real-time analysis of intraoperative ECochG signals using Autonomous Linear State-Space Models (ALSSMs). We developed ALSSM based algorithms for noise reduction, artifact removal, and feature extraction in ECochG. Feature extraction includes local amplitude and phase estimations and a confidence metric over the presence of a physiological response in a recording. We tested the algorithms in a controlled sensitivity analysis using simulations and validated them with real patient data recorded during surgeries. The results from simulation data show that the ALSSM method provides improved accuracy in the amplitude estimation together with a more robust confidence metric of ECochG signals compared to the state-of-the-art methods based on the fast Fourier transform (FFT). Tests with patient data showed promising clinical applicability and consistency with the findings from the simulations. We showed that ALSSMs are a valid tool for real-time analysis of ECochG recordings. Removal of artifacts using ALSSMs enables simultaneous recording of ECochG and impedance data. The proposed feature extraction method provides the means to automate the assessment of ECochG. Further validation of the algorithms in clinical data is needed.

Neuroinflammatory disorders of the brain and inner ear: a systematic review of auditory function in patients with migraine, multiple sclerosis, and neurodegeneration to support the idea of an innovative 'window of discovery'

Background

Hearing can be impaired in many neurological conditions and can even represent a forme fruste of specific disorders. Auditory function can be measured by either subjective or objective tests. Objective tests are more useful in identifying which auditory pathway (superior or inferior) is most affected by disease. The inner ear's perilymphatic fluid communicates with the cerebrospinal fluid (CSF) via the cochlear aqueduct representing a window from which pathological changes in the contents of the CSF due to brain inflammation could, therefore, spread to and cause inflammation in the inner ear, damaging inner hair cells and leading to hearing impairment identifiable on tests of auditory function.

Methods

A systematic review of the literature was performed, searching for papers with case-control studies that analyzed the hearing and migraine function in patients with neuro-inflammatory, neurodegenerative disorders. With data extracted from these papers, the risk of patients with neurological distortion product otoacoustic emission (DPOAE) was then calculated.

Results

Patients with neurological disorders (headache, Parkinson's disease, and multiple sclerosis) had a higher risk of having peripheral auditory deficits when compared to healthy individuals.

Conclusion

Existing data lend credence to the hypothesis that inflammatory mediators transmitted via fluid exchange across this communication window, thereby represents a key pathobiological mechanism capable of culminating in hearing disturbances associated with neuroimmunological and neuroinflammatory disorders of the nervous system.

The Effect of Different Stimulation Rates on Brainstem Auditory-Evoked-Potential Responses

Introduction  Auditory-evoked potentials are influenced by several factors, including polarity, filter, stimulus intensity and stimulation rate. The presentation of higher rates of stimuli per second enables the collection of a greater number of responses in a given period of time, promoting a shorter testing time; however, the collected recordings are subject to changes related to wave morphology. Objectives  To compare the brainstem auditory-evoked-potential responses with click stimulus with the most commonly used stimulation rates in the clinical practice. Methods  The present cross-sectional analytical study was performed with fifteen participants of both genders and normal hearing thresholds. The brainstem auditory-evoked potential was performed at four different stimulation rates (21.1, 26.7, and 27.7 stimuli/s, and a rate determined based on a mathematical calculation using the a measurement of the transmission frequency of the power grid at the time of the examination). Results  We observed that the rate of 21.1 stimuli/s showed the highest amplitudes for waves I, III, and V when compared with the other rates. The rate of 26.7 stimuli/s, when compared with 27.7 stimuli/s, showed a higher amplitude for wave V. The latency if wave V was significantly lower with the rate of 21.1 stimuli/s than with 27.7 stimuli/s. Conclusions  The stimulation rate interferes with wave latencies and amplitudes; its decrease from 27.7 to 21.1 stimuli/s decreases the latency of wave V and increases the amplitues and improves the morphology of waves I, III and V. In addition, we found evidence that suggests an improvement in the visualization of wave III by adjusting the stimulation rate based on a measurement of the local transmission frequency of the power grid.

Normative Values for Auditory Brainstem Responses and Wave V Thresholds in Indian Neonates and Infants

Click-evoked auditory-brainstem-response (ABR) is widely used for hearing screening in neonates and infants. However, their normative values are based on small studies. This retrospective study was done at a tertiary-care centre where click-ABR based screening is done in all newborns. ABR records (Nihon-Kohden machine, model MEB-9400K) of 420 healthy neonates (preterm 75; full-term 32) and infants (113) done over a period 4 years (2014-2018) were analysed retrospectively. Sick neonates and those with Wave V threshold > 40 dbnHL were excluded. Infants were divided into four groups based on post-conceptual age, Group A (75): 34-36 weeks; Group B (44): 37-40weeks; Group C (188):41 weeks-1 month; and Group D (113): 1-6months. The mean absolute latencies for wave I, wave III, and wave V varied from 1.45-1.56 milliseconds (ms), 4.14-4.37 ms, and 6.36-6.81 ms respectively. Interpeak latencies for I-V and I-III varied from 4.91 ms to 5.22 ms and 2.69 ms to 2.81 ms respectively. Older infants had lower absolute and interpeak latencies. Late preterm babies were not different from term babies suggesting early maturation of brainstem pathways.

Embryonic and Neonatal Mouse Cochleae Are Susceptible to Zika Virus Infection

Congenital Zika Syndrome (CZS) is caused by vertical transmission of Zika virus (ZIKV) to the gestating human fetus. A subset of CZS microcephalic infants present with reduced otoacoustic emissions; this test screens for hearing loss originating in the cochlea. This observation leads to the question of whether mammalian cochlear tissues are susceptible to infection by ZIKV during development. To address this question using a mouse model, the sensory cochlea was explanted at proliferative, newly post-mitotic or maturing stages. ZIKV was added for the first 24 h and organs cultured for up to 6 days to allow for cell differentiation. Results showed that ZIKV can robustly infect proliferating sensory progenitors, as well as post-mitotic hair cells and supporting cells. Virus neutralization using ZIKV-117 antibody blocked cochlear infection. AXL is a cell surface molecule known to enhance the attachment of flavivirus to host cells. While Axl mRNA is widely expressed in embryonic cochlear tissues susceptible to ZIKV infection, it is selectively downregulated in the post-mitotic sensory organ by E15.5, even though these cells remain infectible. These findings may offer insights into which target cells could potentially contribute to hearing loss resulting from fetal exposure to ZIKV in humans.

Why a Propofol Infusion Should Be the Anesthetic of Choice for Auditory Brainstem Response Testing in Children

BACKGROUND

Auditory brainstem response (ABR) testing is considered to be relatively resistant to effects of volatile anesthetics. The impact of newer anesthetics on interpretability of ABR testing is unknown. This study compared sevoflurane versus propofol anesthesia on qualitative interpretability of ABR click-testing in children.

METHODS

This prospective double-blind crossover study enrolled children (≤18 years old) receiving general anesthesia for elective ABR testing. All subjects received both sevoflurane and propofol anesthesias in the same ABR testing session. Deidentified ABR data were reviewed by 5 audiologists (blinded to anesthetic and patient) to determine threshold levels for hearing loss. The primary outcome was qualitative interpretability (false positive) of ABR click-testing.

RESULTS

Each patient was tested at 4 different intensities in each ear: generating 624 records under each anesthetic, for a total of 1248 records. A few patients were tested at 5 different intensities in a single ear accounting for the additional 11 records, yielding 1259 records. Under sevoflurane anesthesia, 21 of the same patients (37 ears) were identified with abnormal ABR levels consistent with hearing loss (one or both ears). The probability of a patient being diagnosed with hearing "loss" in one or both ears was significantly less with propofol versus sevoflurane anesthesia (mid P =.0312). If patients with bilateral loss are compared, the mid P value is 0.0098. The effect size based on patients was medium to large, with a minimum value of Cohen w = 0.320.

CONCLUSIONS

Sevoflurane produced more false positives for hearing loss and suggested more severe hearing loss than propofol. False-positive ABR tests, produced by certain anesthetic agents, can have significant life-long impact and negative psychosocial and developmental implications. Use of the intravenous anesthetic propofol is superior to sevoflurane for ABR testing in children.

Neonatal thyrotropin levels and auditory neural maturation in full-term newborns

Objective

This study aimed to look for a possible relationship between thyrotropin (TSH) values from neonatal bloodspot screening testing and newborn lower auditory pathway myelinization evaluated using the brainstem evoked response audiometry (ABR) test.

Methods

Sixty-two healthy full-term newborns without perinatal problems were enrolled in the study. TSH results were collected from neonatal bloodspot screening data and were below the test cut-off level (15μUI/mL). The TSH test was performed between three and seven days, and the ABR test was performed in the first 28 days of life. The newborns were divided into two groups: Group 1 (n = 35), TSH between 0 and 5μUI/mL, and group 2 (n = 27), TSH between 5 and 15μUI/mL. Data are presented as mean ± SD, median, or percentage, depending on the variable.

Results

Wave latency and interpeak interval values for Groups 1 and 2 were as follows: Wave I: 1.8 ± 0.1 and 1.7 ± 0.1; Wave III: 4.4 ± 0.1 and 4.4 ± 0.1; Wave V: 6.9 ± 0.1 and 6.9 ± 0.1; interval I–III: 2.6 ± 0.1 and 2.6 ± 0.1; interval I–V: 5.1 ± 0.1 and 5.1 ± 0.1; interval III–V: 2.4 ± 0.1 and 2.4 ± 0.1. There were no significant differences in ABR parameters between groups 1 and 2 (p > 0.05). Multiple regression analysis showed a slight significant negative correlation between TSH and wave I values (standardized β = −0.267; p = 0.036), without observing any relationship with the other ABR waves recorded.

Conclusions

This study investigated the relationship of TSH and auditory myelinization evaluated by ABR. It did not show a significant change in lower auditory pathway myelinization according to TSH levels in newborns with TSH screening levels lower than 15 μUI/mL.

Clinical Utility of Intraoperative Electrocochleography (ECochG) During Cochlear Implantation: A Systematic Review and Quantitative Analysis

OBJECTIVE

To evaluate the utility of intraoperative electrocochleography (ECochG) as a predictive tool for preservation of residual acoustic hearing after cochlear implantation.

DATA SOURCES

A systematic review employing a multi-database search strategy (Ovid MEDLINE, Embase, EBM Cochrane, and Scopus) was conducted from inception to August 1, 2019. English language studies in humans were included.

STUDY SELECTION

All articles were independently reviewed by two authors according to Preferred Reporting Items of Systematic Reviews and Meta-analysis (PRISMA) guidelines. Studies without intraoperative ECochG obtained during cochlear implantation were excluded.

DATA EXTRACTION

Extracted variables included number of patients, ECochG recording technique, success rate of obtaining ECochG potentials, intraoperative changes in ECochG signal, and postoperative hearing preservation outcomes.

DATA SYNTHESIS

Among 537 eligible articles, 22 met inclusion criteria encompassing 498 unique patients. Ten studies featured extracochlear measurements, eight featured intracochlear measurements, and four featured both. Extracochlear ECochG had an average (SD) recording success rate of 94.9% (12.7%) while intracochlear ECochG had an average (SD) recording success rate of 91.8% (9.8%). One hundred forty five unique patients from six studies had complete intraoperative ECochG data with postoperative behavioral audiometry. After accounting for study-specific definitions of ECochG signal disturbance, worsening changes in intraoperative ECochG signal predicted postoperative hearing loss with limited sensitivity and specificity and notable heterogeneity across studies.

CONCLUSIONS

Intraoperative ECochG recordings can be obtained in over 90% of patients, but accuracy in predicting postoperative hearing loss remains limited. Standardization of intraoperative ECochG monitoring technique and data interpretation are necessary to more robustly investigate outcomes and refine technique.

Early detection of neonatal hearing loss by otoacoustic emissions and auditory brainstem response over 10 years of experience

OBJECTIVES

A number of different screening protocols for detecting neonatal hearing loss currently exist. We present our 10 years of experience with using auditory brainstem response (ABR) complementary to otoacoustic emissions (OAEs) in the three phases hearing screening process in our hospital. Furthermore, we want to demonstrate the usefulness of these screening techniques used in combination, that remain valid to identify cases of neonatal hearing loss and meet the well-established program quality criteria for these screening protocols.

METHODS

Data were collected retrospectively from patient record forms completed on 9698 newborns from 2007 to 2017. The screening protocol for neonatal hearing loss in our centre is carried out in three phases. First phase, prior to discharge from the hospital, consists of carrying out the OAE evaluation on the newborn. Second phase is carried out in the paediatric consultation department. There, the newborns who did not pass the first phase are again studied with OAE. If this phase is not passed either, the child is referred to a third phase for the realization of ABR, in the clinical neurophysiology service. Newborns with risk factors for hearing loss, identified in the first phase, also go on to this third phase. When this hearing threshold exceeds 30 dB, it is considered abnormal. Cases with abnormal ABR, has a re-test conducted within the next six months from the initial ABR assessment.

RESULTS

A total of 9390 (97.1%) OAEs were performed during first phase, with 8245 newborns (87.8%) passing the screening test, while 1145 children (12.1%) presented an abnormal OAE and were included in the second screening phase. Second phase involving a repeat OAE examination performed on 1077 newborns (94%). In this second phase, 941 newborns (87.3%) passed the test. Nevertheless, 136 newborns (12.6%) failing the retest and were referred to continue on to phase three. Furthermore, 181 newborns (1.8%) presented high-risk factors at birth and were also included in this third phase. However, in the registries of children referred to this phase, only 255 (80%) ABR evaluations were confirmed. In total, 227 newborns (2.3%) were missed from the first to third phases of the screening process. According to the database of the clinical neurophysiology service, ABRs evaluations were performed in 352 newborns referred between December 2007 and December 2017. Of this sample, 38.9% were boys and 61.1% were girls. From among cases underwent ABR, 34% of newborns did not pass the OAEs. The most common risk factor was prematurity (with admission to the neonatal intensive care unit for more than five days), affecting 28%. Abnormal ABRs waveforms were found in 43.9%, with 12.3% having a sensorineural hearing loss, 26.5% showing mixed hearing loss and, conductive hearing loss being present in 61.9%. Considering sensorineural hearing loss and other types of severe hearing loss, affected patients constituted only 1.7% of the total number of individuals studied. Finally, regarding quality control of the program participation in the first phase of care included 97.2% of all newborns, yielding a third phase referral rate of 2.9%, confirmation of a diagnosis before the fourth month of life in more than 90% of cases with an average of 3.4 months of age, and a hearing impairment detection rate as an outcome indicator of 4.5%.

CONCLUSIONS

Our data are similar to those of previous studies on screening for hearing loss in newborns. We have demonstrated the advantages of carrying out this protocol in three phases using the otoacoustic emissions together with auditory brainstem response, diagnostic tools that remain as a Gold Standard. Also, we want to highlight and demonstrate the importance of interdisciplinary coordination between the paediatric and clinical neurophysiology services in the implementation of this screening protocol. The foregoing has allowed us to comply with the proposed quality indicators, reaching coverage percentages of more than 95%, confirming the diagnosis of hearing loss within the first six months of life and making timely referrals to benefit the newborns with hearing impairment by way of treatment and follow-up in the early stages of development, avoiding future disabilities.

Population-based cross-sectional study to assess newborn hearing screening program in central Germany

OBJECTIVES

Early diagnosis of congenital hearing loss is fundamental to minimize the negative consequences on the speech development. To lower the age at diagnosis and at intervention in hearing impaired children, not only universal newborn hearing screening (NHS) but also tracking is considered essential. The aim of the study was to evaluate the first six years after implementation of the population based newborn hearing screening program in Saxony-Anhalt, one German Federal State.

METHODS

The cross-sectional cohort study consisted of three cohort samples. Overall 102,301 infants born between January 2010 and December 2015 were included. NHS protocol was developed as dual target group protocol with two sub-protocols. The screening technique included Transient Evoked Otoacoustic Emissions (TEOAE) and Automated Auditory Brainstem Response (AABR) test. Newborns were assigned to the sub-protocols according to their audiological risk factors. Additionally, to evaluate the quality of NHS and tracking (false-negative screening) we were analysing data from a cohort of hearing impaired children diagnosed up to the age of three years. We calculated quality indicators and compared them with international guidelines.

RESULTS

101,102 (98.8%) infants were screened. The prevalence of bilateral neonatal hearing loss was 2.32 per 1000 newborns. The median age was two days at first screening, three month at diagnostic testing, and four month at intervention onset. 2.6% infants were lost to follow-up. 56.3% had a final diagnosis of bilateral sensorineural hearing loss. The sensitivity of 0.85 (KI 95%: 0.76–0.91) and a specificity of 0.84 (KI 95%: 0.84–0.85) was calculated for the NHS program.

CONCLUSIONS

The analysis of benchmarks and outcomes of NHS demonstrated that the program reaches its main goal to identify the hearing impaired newborns in a timely manner.