United Kingdom national paediatric bilateral project: Results of professional rating scales and parent questionnaires.

OBJECTIVES: This fourteen-centre project used professional rating scales and parent questionnaires to assess longitudinal outcomes in a large non-selected population of children receiving simultaneous and sequential bilateral cochlear implants. METHODS: This was an observational non-randomized service evaluation. Data were collected at four time points: before bilateral cochlear implants or before the sequential implant, one year, two years, and three years after. The measures reported are Categories of Auditory Performance II (CAPII), Speech Intelligibility Rating (SIR), Bilateral Listening Skills Profile (BLSP) and Parent Outcome Profile (POP). RESULTS: Thousand and one children aged from 8 months to almost 18 years were involved, although there were many missing data. In children receiving simultaneous implants after one, two, and three years respectively, median CAP scores were 4, 5, and 6; median SIR were 1, 2, and 3. Three years after receiving simultaneous bilateral cochlear implants, 61% of children were reported to understand conversation without lip-reading and 66% had intelligible speech if the listener concentrated hard. Auditory performance and speech intelligibility were significantly better in female children than males. Parents of children using sequential implants were generally positive about their child's well-being and behaviour since receiving the second device; those who were less positive about well-being changes also generally reported their children less willing to wear the second device. CONCLUSION: Data from 78% of paediatric cochlear implant centres in the United Kingdom provide a real-world picture of outcomes of children with bilateral implants in the UK. This large reference data set can be used to identify children in the lower quartile for targeted intervention.

United Kingdom national paediatric bilateral project: Demographics and results of localization and speech perception testing.

OBJECTIVES: To assess longitudinal outcomes in a large and varied population of children receiving bilateral cochlear implants both simultaneously and sequentially. METHODS: This observational non-randomized service evaluation collected localization and speech recognition in noise data from simultaneously and sequentially implanted children at four time points: before bilateral cochlear implants or before the sequential implant, 1 year, 2 years, and 3 years after bilateral implants. No inclusion criteria were applied, so children with additional difficulties, cochleovestibular anomalies, varying educational placements, 23 different home languages, a full range of outcomes and varying device use were included. RESULTS: 1001 children were included: 465 implanted simultaneously and 536 sequentially, representing just over 50% of children receiving bilateral implants in the UK in this period. In simultaneously implanted children the median age at implant was 2.1 years; 7% were implanted at less than 1 year of age. In sequentially implanted children the interval between implants ranged from 0.1 to 14.5 years. Children with simultaneous bilateral implants localized better than those with one implant. On average children receiving a second (sequential) cochlear implant showed improvement in localization and listening in background noise after 1 year of bilateral listening. The interval between sequential implants had no effect on localization improvement although a smaller interval gave more improvement in speech recognition in noise. Children with sequential implants on average were able to use their second device to obtain spatial release from masking after 2 years of bilateral listening. Although ranges were large, bilateral cochlear implants on average offered an improvement in localization and speech perception in noise over unilateral implants. CONCLUSION: These data represent the diverse population of children with bilateral cochlear implants in the UK from 2010 to 2012. Predictions of outcomes for individual patients are not possible from these data. However, there are no indications to preclude children with long inter-implant interval having the chance of a second cochlear implant.

Guidelines for quantification of noise-induced hearing loss in a medicolegal context.

OBJECTIVES: Guidelines published in 2000 by the authors are widely used by medical and legal professionals in the UK for diagnosis of noise-induced hearing loss in a medicolegal context. However, they cannot be used for quantification of the noise-induced hearing loss, which is required in most cases. This requirement is addressed. DESIGN: A method is developed here to quantify noise-induced hearing loss, thereby overcoming this shortcoming. SETTING: Assessment of noise-induced hearing loss in medicolegal cases. PARTICIPANTS: A consecutive series of 124 cases of noise-induced hearing loss is used for evaluation. MAIN OUTCOME MEASURE: Magnitude of noise-induced hearing loss based on hearing threshold levels averaged over the frequencies 1, 2 and 3 kHz. RESULTS: The rationale of the method, practical application and three worked examples are developed. A simpler short-cut method is developed and shown to be equivalent to the full method in most cases. CONCLUSIONS: The method offers a practical approach to quantification of noise-induced hearing loss.

Movement decoding using neural synchronization and inter-hemispheric connectivity from deep brain local field potentials.

OBJECTIVE: Correlating electrical activity within the human brain to movement is essential for developing and refining interventions (e.g. deep brain stimulation (DBS)) to treat central nervous system disorders. It also serves as a basis for next generation brain-machine interfaces (BMIs). This study highlights a new decoding strategy for capturing movement and its corresponding laterality from deep brain local field potentials (LFPs). APPROACH: LFPs were recorded with surgically implanted electrodes from the subthalamic nucleus or globus pallidus interna in twelve patients with Parkinson's disease or dystonia during a visually cued finger-clicking task. We introduce a method to extract frequency dependent neural synchronization and inter-hemispheric connectivity features based upon wavelet packet transform (WPT) and Granger causality approaches. A novel weighted sequential feature selection algorithm has been developed to select optimal feature subsets through a feature contribution measure. This is particularly useful when faced with limited trials of high dimensionality data as it enables estimation of feature importance during the decoding process. MAIN RESULTS: This novel approach was able to accurately and informatively decode movement related behaviours from the recorded LFP activity. An average accuracy of 99.8% was achieved for movement identification, whilst subsequent laterality classification was 81.5%. Feature contribution analysis highlighted stronger contralateral causal driving between the basal ganglia hemispheres compared to ipsilateral driving, with causality measures considerably improving laterality discrimination. SIGNIFICANCE: These findings demonstrate optimally selected neural synchronization alongside causality measures related to inter-hemispheric connectivity can provide an effective control signal for augmenting adaptive BMIs. In the case of DBS patients, acquiring such signals requires no additional surgery whilst providing a relatively stable and computationally inexpensive control signal. This has the potential to extend invasive BMI, based on recordings within the motor cortex, by providing additional information from subcortical regions.

Relations between psychophysical measures of spatial hearing and self-reported spatial-hearing abilities.

OBJECTIVE: The aim of the present study was to investigate how well the virtual psychophysical measures of spatial hearing from the preliminary auditory profile predict self-reported spatial-hearing abilities. DESIGN: Virtual spatial-hearings tests (conducted unaided, via headphones) and a questionnaire were administered in five centres in Germany, the Netherlands, Sweden, and the UK. Correlations and stepwise linear regression models were calculated among a group of hearing-impaired listeners. STUDY SAMPLE: Thirty normal-hearing listeners aged 19-39 years, and 72 hearing-impaired listeners aged 22-91 years with a broad range of hearing losses, including asymmetrical and mixed hearing losses. RESULTS: Several significant correlations (between 0.24 and 0.54) were found between results of virtual psychophysical spatial-hearing tests and self-reported localization abilities. Stepwise linear regression analyses showed that the minimum audible angle (MAA) test was a significant predictor for self-reported localization abilities (5% extra explained variance), and the spatial speech reception threshold (SRT) benefit test for self-reported listening to speech in spatial situations (6% extra explained variance). CONCLUSIONS: The MAA test and spatial SRT benefit test are indicative measures of everyday binaural functioning. The binaural SRT benefit test was not found to predict self-reported spatial-hearing abilities.

Identification and analysis of the first 2009 pandemic H1N1 influenza virus from U.S. feral swine.

The first case of pandemic H1N1 influenza (pH1N1) virus in feral swine in the United States was identified in Texas through the United States Department of Agriculture (USDA) Wildlife Services' surveillance program. Two samples were identified as pandemic influenza by reverse transcriptase quantitative PCR (RT-qPCR). Full-genome Sanger sequencing of all eight influenza segments was performed. In addition, Illumina deep sequencing of the original diagnostic samples and their respective virus isolation cultures were performed to assess the feasibility of using an unbiased whole-genome linear target amplification method and multiple sample sequencing in a single Illumina GAIIx lane. Identical sequences were obtained using both techniques. Phylogenetic analysis indicated that all gene segments belonged to the pH1N1 (2009) lineage. In conclusion, we have identified the first pH1N1 isolate in feral swine in the United States and have demonstrated the use of an easy unbiased linear amplification method for deep sequencing of multiple samples.

An economic evaluation of screening 60- to 70-year-old adults for hearing loss.

BACKGROUND: Hearing loss is common among older adults and has consequences for sufferers, families and society, but there is substantial unmet need for intervention. Screening could expedite intervention and improve outcomes. METHODS: We use Markov models to estimate the incremental cost-effectiveness ratio (ICER) of potential screening programmes compared with current provision (GP-referral), from a health service perspective. Alternative options are investigated through scenario analysis. One-way and probabilistic sensitivity analyses are undertaken. RESULTS: All modelled screens are cost-effective and reduce unmet need for hearing aids. The most cost-effective option identified is a one-stage audiometric screen for bilateral hearing loss ≥30 dB hearing level (HL) at age 60, repeated at ages 65 and 70. This option has an ICER of £1461 compared to GP-referral and would mean an additional 15 437 adults benefiting from hearing intervention per 100 000 population aged 60. The cost-effectiveness acceptability curve shows that screening is more cost-effective than GP-referral provided a Quality Adjusted Life Year is valued at £2000 or more. CONCLUSIONS: Adult hearing screening would provide a cost-effective way to improve quality of life for older adults. We recommend piloting an audiometric screen offered to all adults age 60, 65 and 70 years to identify bilateral hearing loss of at least 30 dB HL.

United Kingdom national paediatric bilateral audit.

Prior to 2009, UK public funding was mainly only available for children to receive unilateral cochlear implants. In 2009, the National Institute for Health and Clinical Excellence (NICE) published guidance for cochlear implantation following their review. According to these guidelines, all suitable children are eligible to have simultaneous bilateral cochlear implants or a sequential bilateral cochlear implant if they had received the first before the guidelines were published. NICE stated that they would review this decision in 2011. In preparation for this review, 13 UK cochlear implant centres formed a consortium, and the decision was made to carry out a multi-centre audit. The audit involves collecting data from simultaneously and sequentially implanted children at three intervals: before bilateral cochlear implants or before the sequential implant, 1 year after bilateral implants, and 2 years after bilateral implants. The measures include localization, speech recognition in quiet and background noise, speech production, listening, vocabulary, parental perception, quality of life, and surgical data including complications. The audit has now passed the 1-year point, and data have been received on more than 400 children. Preliminary results will be available a year later.

Development of a quality-of-life measure for adult patients with sequential bilateral cochlear implants.

It has been well established in the literature that hearing difficulties can have an adverse effect on the quality of life of an individual. This study looked at developing a quality-of-life measure for adult patients who received bilateral cochlear implants sequentially. The sample consisted of patients from the UK National Health Service who have received two implants sequentially. The study was divided into three stages. A retrospective open-ended questionnaire and face-to-face interviews were carried out in to develop a close-ended questionnaire for the same purposes. This is now being validated and tested for its reliability. Categories from the qualitative data were identified and these were the foundations on which the close-ended questionnaire was developed. The 'Outcomes from Bilateral Cochlear Implantation' questionnaire originally had 42 questions. Test-retest reliability was investigated and some amendments were made to reflect this. Participants will next be asked to fill in the amended questionnaire together with another three quality-of-life questionnaires (generic and disease-specific ones) and the results will be compared. Better understanding of quality of life after receiving the second implant will aid professionals dealing with these patients in understanding what the practical limitations of these devices are and advising future patients accordingly.

Parents' views on the quality of life of their children 2-3 years after cochlear implantation.

OBJECTIVE: Cochlear implants for children are known to have impact on the lives of recipients and their families in a variety of ways. To obtain a clearer picture of these benefits, we explored the quality of life of 36 Finnish children and their families 2-3 years after unilateral cochlear implantation. METHODS: The studied children were, on average 5 years old, and had received their implant at the median age of 2 years:5 months (range 1:6 to 12:3). Most (67%) of the children used speech, eight (22%) used speech and signs, and four (11%) used sign language as their main communication mode. A third of the children had concomitant problems in addition to their profound hearing impairment. A validated closed-set questionnaire "Children with cochlear implants: parental perspectives" (available, e.g., at http://www.earfoundation.org.uk/research/questionnaires.html) was used to find out parents' views and experiences on implantation and explore life after it. RESULTS: Parents were most satisfied with improved/expanded social relations, improved communication (the development of spoken language), general functioning with the help of hearing and improved self-reliance of the child. Benefit of cochlear implantation was also detected with the Categories of Auditory Performance (CAP), which was concordant with views of the parents on the progress of their child in the areas of communication and education. When deciding on implantation, the parents particularly expected auditory information to enhance their child's safety in traffic, joining socially the hearing world, and better employment prospects as adults. Concerning the process of implantation, parents especially valued the know-how and fluent services of the implant centre, positive attitude within the family and information received from other families during the time they were considering the implant decision. Parents also found it important that they have the possibility to influence the communication mode that is used in their child's educational setting. CONCLUSIONS: Parents report that cochlear implants affect their children in a wide variety of ways that cannot be summarized by a single scale. A broader descriptive framework is required to capture their experiences adequately.

Asymmetric sensorineural hearing thresholds in the non-noise-exposed UK population: a retrospective analysis.

OBJECTIVES: To estimate the distribution of inter-aural sensorineural hearing threshold level differences in the non-noise-exposed adult population of the UK. SETTING: A two-stage population study carried out in 1979-1986, initially by postal questionnaire, followed up in a proportion of participants by clinical and audiological examination. PARTICIPANTS: Volunteers (n = 48 313) initially selected at random from the electoral registers of four cities, subsequently selected at random from questionnaire respondents stratified by answers to questions about hearing. MAIN OUTCOMES MEASURE: Inter-aural hearing threshold level differences measured audiometrically, as a function of age and gender. RESULTS: Tables of inter-aural threshold level differences provided as a resource with potential medicolegal, clinical and research applications. Based on the average of the frequencies 0.5, 1, 2 and 4 kHz, approximately 1% of the general UK population aged 18-80 years have an asymmetry of 15 dB or more. The prevalence is greater in older than in younger people. CONCLUSIONS: Inter-aural threshold differences greater than attributable to measurement error are not uncommon in the adult population, even after screening for conductive hearing loss and substantial noise exposure. They are typically of unknown origin.

Age at implantation and development of vocal and auditory preverbal skills in implanted deaf children.

BACKGROUND: Preverbal vocal and auditory skills are essential precursors of spoken language development and they have been shown previously to predict later speech perception and production outcomes in young implanted deaf children. OBJECTIVES: To assess the effect of age at implantation on the development of vocal and auditory preverbal skills in implanted children. METHODS: The study assessed 99 children, 33 in each of three groups (those implanted between 1 and 2 years; 2 and 3 years; and 3 and 4 years). Preverbal skills were measured in three areas: turn taking, autonomy and auditory awareness of spoken language, using the Tait video analysis method. RESULTS: The youngest implanted group made an exceptional progress outperforming in all measures the two other groups (p<0.01), 6 and 12 months post-implantation, whereas there was no such difference before implantation. In the youngest group there was also significantly greater use of an auditory/oral style of communication: 85% of the group by 12 months post-implantation compared with 30% and 18% of the two older groups. CONCLUSIONS: Vocal and auditory preverbal skills develop much more rapidly in children implanted between 1 and 2 years in comparison with older implanted children and reach a significantly higher level by 6 and 12 months post-implantation. In addition, younger implanted children are significantly more likely by 12 months post-implantation to adopt an auditory/oral mode of communication. These findings favour cochlear implantation as early as between 1 and 2 years, provided that correct diagnosis and adequate hearing-aid trial have been achieved.

The identification of musical instruments through nucleus cochlear implants.

In this study, self-reported ability to recognize musical instruments was investigated by means of a questionnaire, which was sent to a group of adult Nucleus cochlear implant users and a group of normally hearing subjects. In addition, spectrograms and electrodograms were produced and analysed for samples of music played on 10 different musical instruments. Self-reported ability to recognize some instruments was poor in the group of implant users, particularly for the saxophone, tuba and clarinet. Electrodograms showed that these instruments could only be identified using distorted spectral information or reduced temporal information. Other instruments, such as the drum and piano, could be identified using temporal information. Limited spectral resolution makes the recognition of musical instruments difficult for Nucleus implant users.

The generation mechanisms and repeatability of 2F1-F2 distortion product otoacoustic emissions: study on normally hearing subjects.

The 2F1-F2 distortion product otoacoustic emission (DPOAE) is considered to consist of two generation mechanisms, the so-called place-fixed and wave-fixed mechanisms, depending on the frequency ratio F2/F1. The general assumption is that for a small frequency ratio there is a predominantly place-fixed emission mechanism, while with a larger frequency ratio there is a predominantly wave-fixed mechanism. There is also a lack of published data on the repeatability of the two components when separated. One aim of this study was therefore to identify the wave-fixed and place-fixed components of the 2F1-F2 DPOAE using a time-window separation method. The second aim was to quantify the test-retest repeatability of the separated 2F1-F2 DPOAE components in a group of normally hearing subjects. Results confirmed the presence of wave-fixed and place-fixed components for 2F1-F2 and a predominance of place or wave-fixed DPOAE as a function of frequency ratio. This pattern varied somewhat among subjects. Moreover, regardless of which component was stronger for any F2/F1, both components were highly repeatable across time within individual ears.

Influence on the mechanisms of generation of distortion product otoacoustic emissions of mobile phone exposure.

Mobile phones have become very commonly used throughout the world within a short period of time. Although there is no clear evidence to show harmful physiological effects of electromagnetic fields (EMF) at the levels used by mobile phones, there is widespread public concern that there may be potential for harm. Because mobile phones are usually held close to the ear, it is appropriate to study effects on hearing. In this study, the outer hair cell function of 15 subjects was assessed by DPOAE recording before and after a controlled EMF exposure. To increase the sensitivity of DPOAE recording to identify even small changes in hearing function, an inverse fast Fourier transform (IFFT) analysis and time-domain windowing was applied to separate the two generation mechanisms of DPOAE, the so-called place-fixed and wave-fixed mechanisms, in order to verify if EMF can affects the two DPOAE emission mechanisms. Statistical analysis of the data showed that 10 min of EMF exposure at the maximum power (2 W at 900 MHz or 1 W at 1800 MHz) does not induce any changes in either DPOAE generation mechanism.

Demystifying biomedical signals: a student centred approach to learning signal processing.

The processing and analysis of physiological signals has become firmly established in clinical medicine and biomedical research. Many of the users of this technology however do not come from an engineering or science background, and traditional approaches in teaching signal processing are thus not appropriate for them. We have therefore developed a series of modular courses that are aimed specifically at an audience with a background in medicine, health-care or the life-sciences. In these courses, we focus on the concepts, principles and rationale of applying signal processing methods, rather than the mathematical foundations of the techniques. Thus, we aim to remove some of the perceived 'mystery' often surrounding this subject. The very practical approach, with hands-on experience using the MATLAB software, has been well received, with strong evidence that students have learnt to apply their knowledge. This paper describes the learning and teaching approach taken, and some of the experience acquired.

Effect of aspirin on phase gradient of 2F1-F2 distortion product otoacoustic emissions.

It is well known that aspirin consumption temporarily reduces overall otoacoustic emission (OAE) amplitude in humans. However, little is known about changes in the separate components of distortion product otoacoustic emissions (DPOAE), which may be distinguished by examining phase gradients. The effects of aspirin on the phase gradient of the DPOAE 2F1-F2 obtained with fixed frequency ratio sweeps were studied longitudinally in a group of twelve subjects in whom a temporary hearing loss was induced by aspirin consumption. DPOAE were recorded daily for two days pre-aspirin consumption, during the three days of aspirin consumption and two days afterwards. DP-grams were recorded over a restricted frequency range centered on 2,3,4 and 6 kHz with the following stimulus levels: L1/L2 of 60/50-80/70 in 10-dB steps. The effects of aspirin on the phase gradients varied between the subjects and across frequency: the general trend was that the phase gradient became steeper across successive sessions for the higher frequencies, while no significant effect was found at the lower frequencies. These results suggest that aspirin may have more persistent effects on cochlear function than are disclosed by measurements of hearing threshold level or DPOAE amplitude. Particularly, DPOAE phase gradient appears to be increased by aspirin consumption and has not recovered two days after cessation of aspirin intake, despite almost complete recovery of DPOAE amplitude and hearing threshold levels. These findings may suggest differential effects on the distortion and reflection mechanisms considered to underlie DPOAE generation.

Recording the middle latency response of the auditory evoked potential as a measure of depth of anaesthesia. A technical note.

The middle latency response of the auditory evoked potential may be useful as an indicator of the hypnotic state during anaesthesia. However, it is difficult to record in some circumstances. This communication provides some suggestions and guidance for those not familiar with the technique.

Localization performance of unilateral cochlear implant users for speech, tones and noise.

Bilateral cochlear implants aim to improve sound localization compared to monaural implants, among other potential benefits. Monaural cochlear implants should not support localization in the horizontal plane as there are no interaural level and time difference cues available, although some previous studies have suggested limited capability. As background to other studies of bilateral implantation, the localization abilities of 18 monaural cochlear implantees were investigated experimentally in an anechoic chamber, using various sound stimuli with different amounts of temporal information. The effects of head movement and reverberation were also investigated. Localization performance was found to be close to chance for all stimuli. It is confirmed that monaural cochlear implants are unable to support useful auditory sound localization, even when head movements are allowed.