Tone-burst elicited auditory brainstem responses in full-term and pre-term infants

OBJECTIVE

To investigate the reliability of tone-burst auditory brainstem response (TB-ABR) latencies and thresholds in pre-term and full-term infants.

DESIGN

TB-ABRs to 500 Hz and 4000 Hz tone-burst stimuli were recorded at two-week intervals over the first six weeks of life in a group of full-term infants (40-46 weeks gestational age [GA]) and over ten weeks (36-46 weeks gestation) in a group of preterm infants. Linear mixed model analyses evaluated within-subject changes and the effects of the subject group, age at assessment, and stimulus frequency on ABR latency and threshold.

STUDY SAMPLE

Twenty-four infants participated. Nine were full-term (GA: 39-41 weeks) and fifteen were healthy pre-term (GA: 28-34 weeks) at birth.

RESULTS

TB-ABR wave V latencies at 70 dBnHL decreased throughout the study (p < 0.001) in pre-term babies for both test frequencies by approximately 0.5 ms. There were, however, no group or GA (at birth) effects indicating that response latency normalized in these children by the due date. Similarly, TB-ABR threshold levels in the premature group were elevated (p = 0.001) by approximately 5 dB in pre-term evaluation but were equivalent to those of full-term participants in the post-term assessment period.

CONCLUSIONS

In healthy, pre-term infants, tone-burst ABR testing is reliable from 36 weeks gestation.

Remediation of Perceptual Deficits in Progressive Auditory Neuropathy: A Case Study

BACKGROUND

Auditory neuropathy (AN) is a hearing disorder that affects neural activity in the VIIIth cranial nerve and central auditory pathways. Progressive forms have been reported in a number of neurodegenerative diseases and may occur as a result of both the deafferentiation and desynchronisation of neuronal processes. The purpose of this study was to describe changes in auditory function over time in a patient with axonal neuropathy and to explore the effect of auditory intervention.

METHODS

We tracked auditory function in a child with progressive AN associated with Charcot-Marie-Tooth (Type 2C) disease, evaluating hearing levels, auditory-evoked potentials, and perceptual abilities over a 3-year period. Furthermore, we explored the effect of auditory intervention on everyday listening and neuroplastic development.

RESULTS

While sound detection thresholds remained constant throughout, both electrophysiologic and behavioural evidence suggested auditory neural degeneration over the course of the study. Auditory brainstem response amplitudes were reduced, and perception of auditory timing cues worsened over time. Functional hearing ability (speech perception in noise) also deteriorated through the first 1.5 years of study until the child was fitted with a "remote-microphone" listening device, which subsequently improved binaural processing and restored speech perception ability to normal levels.

CONCLUSIONS

Despite the deterioration of auditory neural function consistent with peripheral axonopathy, sustained experience with the remote-microphone listening system appeared to produce neuroplastic changes, which improved the patient's everyday listening ability-even when not wearing the device.

Interviews with musicians with hearing aids

Objectives: Musicians who wear hearing aids are a unique subset of hearing-impaired individuals. There are a number of issues musicians experience with hearing aids, making effective hearing rehabilitation a challenge. Research suggests hearing aid satisfaction in musicians is lower partly due to their advanced listening skills, however, qualitative research addressing musicians who wear hearing aids for music is scarce. The current study aimed to record the barriers encountered by musicians who wear hearing aids when playing their instrument/singing, listening to recorded music and listening to live music.Design: Professional musicians who wear hearing aids were interviewed. Participants were questioned about their experiences with hearing loss and hearing aids, with particular emphasis on experiences listening to recorded and live music, and playing or performing music with the hearing aids.Study Sample: Eight professional musicians were interviewed, using a semi-structured interview style, with a question and prompt guide.Results: Thematic analysis revealed three main themes in the data: the musicians' journey, communication, and flexibility/adjustability.Conclusions: The results have implications for future research into specific fitting parameters for hearing aids for musicians (particularly for music performance), the need for evidence-based rehabilitation programs for musicians with hearing loss, and the need for a glossary of terms to assist communication between Audiologists and musicians.

The Assistive Benefits of Remote Microphone Technology for Normal Hearing Children With Listening Difficulties

OBJECTIVES

Children often present with listening difficulties (LiD) but with normal sound detection thresholds. These children are susceptible to learning challenges, and struggle with the suboptimal acoustics of standard classrooms. Remote microphone technology (RMT) is one way to improve the listening environment. The aim of this study was to determine the assistive potential of RMT for speech identification and attention skills in children with LiD, and to investigate whether the benefits obtained by these children were greater than for those with no listening concerns.

DESIGN

A total of 28 children with LiD and 10 control participants with no listening concerns aged 6 to 12 years were included in this study. Children attended two laboratory-based testing sessions, where their speech intelligibility and attention skills were behaviorally assessed with and without the use of RMT.

RESULTS

There were significant improvements in speech identification and attention skills when RMT was used. For the LiD group, use of the devices improved speech intelligibility to being comparable or better than control abilities without RMT. Auditory attention scores also improved from being poorer than controls without RMT to comparable to control performance with device assistance.

CONCLUSIONS

Use of RMT was found to have a positive effect on both speech intelligibility and attention. RMT should be considered a viable option for addressing common behavioral symptoms of LiD, including for the many children that present with concerns of inattentiveness.

Auditory neuropathy in mice and humans with Friedreich ataxia

OBJECTIVE

Recent studies have found that human Friedreich ataxia patients have dysfunction of transmission in the auditory neural pathways. Here, we characterize hearing deficits in a mouse model of Friedreich ataxia and compare these to a clinical population.

METHODS

Sixteen mice with a C57BL/6 background were evaluated. Eight were YG8Pook/J animals (Friedreich ataxia phenotype) and eight wild-type mice served as controls. Auditory function was assessed between ages 6 and 12 months using otoacoustic emissions and auditory steady-state responses. At study end, motor deficit was assessed using Rotorod testing and inner ear tissue was examined. Thirty-seven individuals with Friedreich ataxia underwent auditory steady-state evoked potential assessment and response amplitudes were compared with functional hearing ability (speech perception-in-noise) and disease status was measured by the Friedreich Ataxia Rating Scale.

RESULTS

The YG8Pook/J mice showed anatomic and functional abnormality. While otoacoustic emission responses from the cochlear hair cells were mildly affected, auditory steady-state responses showed exaggerated amplitude reductions as the animals aged with Friedreich ataxia mice showing a 50-60% decrease compared to controls who showed only a 20-25% reduction (F(2,94)  = 17.90, p < 0.00). Furthermore, the YG8Pook/J mice had fewer surviving spiral ganglion neurons, indicating greater degeneration of the auditory nerve. Neuronal density was 20-25% lower depending on cochlear region (F(1, 30)  = 45.02, p < 0.001). In human participants, auditory steady-state response amplitudes were correlated with both Consonant-Nucleus-Consonant word scores and Friedreich Ataxia Rating Scale score.

INTERPRETATION

This study found degenerative changes in auditory structure and function in YG8Pook/J mice, indicating that auditory measures in these animals may provide a model for testing Friedreich ataxia treatments. In addition, auditory steady-state response findings in a clinical population suggested that these scalp-recorded potentials may serve as an objective biomarker for disease progress in affected individuals.

Evaluation of a game-based hearing screening program for identifying hearing loss in primary school-aged children

OBJECTIVES

To evaluate a tablet-based hearing screening game in primary school aged children. To examine the prevalence of middle/outer ear pathology, hearing loss and spatial processing disorder in primary school aged children.

DESIGN

The automated hearing test Sound Scouts was used as a screening tool, which measures hearing abnormalities through tests of speech-in-quiet/noise and tone-in-noise. Children who failed the screenings underwent follow up testing with pure tone audiometry, tympanometry, otoscopy, and the Listening in Spatialised Noise-Sentences test. Results of each test were compared to measure efficacy.

STUDY SAMPLE

1256 children aged 4-13 years from 8 primary schools.

RESULTS

111 children (8.84%) presented with evidence of middle/outer ear pathologies. 21 children (1.67%) had hearing loss in at least one ear. 30 children (2.52%) were diagnosed with spatial processing disorder. False positive rate was 5.01%, indicating that a relatively small proportion of the children who failed the screenings were subsequently shown to have normal auditory function.

CONCLUSIONS

A game based program testing sound detection and binaural speech processing can be effective in detecting undiagnosed hearing deficits, in large format school-based hearing screenings. Prevalence of hearing abnormalities in Victorian primary school aged children were established, highlighting the value of school hearing screening programs.

The effect of classroom environment on literacy development

The physical characteristics of a child's learning environment can affect health, wellbeing and educational progress. Here we investigate the effect of classroom setting on academic progress in 7-10-year-old students comparing reading development in "open-plan" (multiple class groups located within one physical space) and "enclosed-plan" (one class group per space) environments. All learning conditions (class group, teaching personnel, etc.) were held constant throughout, while physical environment was alternated term-by-term using a portable, sound-treated dividing wall. One hundred and ninety-six students underwent academic, cognitive and auditory assessment at baseline and 146 of these were available for repeat assessment at the completion of 3 school terms, allowing within-child changes across an academic year to be calculated. Reading fluency development (change in words read-per-minute) was greater for the enclosed-classroom phases (P < 0.001; 95%CI 3.7, 10.0) and the children who showed the greatest condition difference (i.e. slower rate of development in the open-plan) were those with the worst speech perception in noise and/or poorest attention skills. These findings highlight the important role classroom setting plays in the academic development of young students.

Acoustic change complex for assessing speech discrimination in normal-hearing and hearing-impaired infants

OBJECTIVE

This study examined (1) the utility of a clinical system to record acoustic change complex (ACC, an event-related potential recorded by electroencephalography) for assessing speech discrimination in infants, and (2) the relationship between ACC and functional performance in real life.

METHODS

Participants included 115 infants (43 normal-hearing, 72 hearing-impaired), aged 3-12 months. ACCs were recorded using [szs], [uiu], and a spectral rippled noise high-pass filtered at 2 kHz as stimuli. Assessments were conducted at age 3-6 months and at 7-12 months. Functional performance was evaluated using a parent-report questionnaire, and correlations with ACC were examined.

RESULTS

The rates of onset and ACC responses of normal-hearing infants were not significantly different from those of aided infants with mild or moderate hearing loss but were significantly higher than those with severe loss. On average, response rates measured at 3-6 months were not significantly different from those at 7-12 months. Higher rates of ACC responses were significantly associated with better functional performance.

CONCLUSIONS

ACCs demonstrated auditory capacity for discrimination in infants by 3-6 months. This capacity was positively related to real-life functional performance.

SIGNIFICANCE

ACCs can be used to evaluate the effectiveness of amplification and monitor development in aided hearing-impaired infants.

Clinical management guidelines for Friedreich ataxia: best practice in rare diseases

BACKGROUND

Individuals with Friedreich ataxia (FRDA) can find it difficult to access specialized clinical care. To facilitate best practice in delivering healthcare for FRDA, clinical management guidelines (CMGs) were developed in 2014. However, the lack of high-certainty evidence and the inadequacy of accepted metrics to measure health status continues to present challenges in FRDA and other rare diseases. To overcome these challenges, the Grading of Recommendations Assessment and Evaluation (GRADE) framework for rare diseases developed by the RARE-Bestpractices Working Group was adopted to update the clinical guidelines for FRDA. This approach incorporates additional strategies to the GRADE framework to support the strength of recommendations, such as review of literature in similar conditions, the systematic collection of expert opinion and patient perceptions, and use of natural history data.

METHODS

A panel representing international clinical experts, stakeholders and consumer groups provided oversight to guideline development within the GRADE framework. Invited expert authors generated the Patient, Intervention, Comparison, Outcome (PICO) questions to guide the literature search (2014 to June 2020). Evidence profiles in tandem with feedback from individuals living with FRDA, natural history registry data and expert clinical observations contributed to the final recommendations. Authors also developed best practice statements for clinical care points that were considered self-evident or were not amenable to the GRADE process.

RESULTS

Seventy clinical experts contributed to fifteen topic-specific chapters with clinical recommendations and/or best practice statements. New topics since 2014 include emergency medicine, digital and assistive technologies and a stand-alone section on mental health. Evidence was evaluated according to GRADE criteria and 130 new recommendations and 95 best practice statements were generated.

DISCUSSION AND CONCLUSION

Evidence-based CMGs are required to ensure the best clinical care for people with FRDA. Adopting the GRADE rare-disease framework enabled the development of higher quality CMGs for FRDA and allows individual topics to be updated as new evidence emerges. While the primary goal of these guidelines is better outcomes for people living with FRDA, the process of developing the guidelines may also help inform the development of clinical guidelines in other rare diseases.

Increased rate of listening difficulties in autistic children

INTRODUCTION

Auditory challenges are both common and disruptive for autistic children and evidence suggests that listening difficulties may be linked to academic underachievement (Ashburner, Ziviani & Rodger, 2008). Such deficits may also contribute to issues with attention, behavior, and communication (Ashburner et al., 2008; Riccio, Cohen, Garrison & Smith, 2005). The present study aims to summarize the auditory challenges of autistic children with normal pure-tone hearing thresholds, and perceived listening difficulties, seen at auditory-ASD clinics in the US and Australia.

METHODS

Data were compiled on a comprehensive, auditory-focused test battery in a large clinical sample of school-age autistic children with normal pure-tone hearing to date (N = 71, 6-14 years). Measures included a parent-reported auditory sensory processing questionnaire and tests of speech recognition in noise, binaural integration, attention, auditory memory and listening comprehension. Individual test performance was compared to normative data from children with no listening difficulties.

RESULTS

Over 40% of patients exhibited significantly reduced speech recognition in noise and abnormal dichotic integration that were not attributed to deficits in attention. The majority of patients (86%) performed abnormally on at least one auditory measure, suggesting that functional auditory issues can exist in autistic patients despite normal pure-tone sensitivity.

CONCLUSION

Including functional listening measures during audiological evaluations may improve clinicians' ability to detect and manage the auditory challenges impacting this population. Learner Outcomes: 1) Readers will be able to describe the auditory difficulties experienced by some autistic patients (ASD). 2) Readers will be able to describe clinical measures potentially useful for detecting listening difficulties in high-functioning autistic children.

A randomized controlled trial of remote microphone listening devices to treat auditory deficits in children with neurofibromatosis type 1

Background

A high proportion of patients with neurofibromatosis type 1 (NF1) present with functional hearing deficiency as a result of neural abnormality in the late auditory brainstem.

Methods

In this randomized, two-period crossover study, we investigated the hypothesis that remote-microphone listening devices can ameliorate hearing and communication deficits in affected school-aged children (7–17 years). Speech perception ability in background noise was evaluated in device-active and inactive conditions using the CNC-word test. Participants were then randomized to one of two treatment sequences: (1) inactive device for two weeks (placebo), followed by active device use for two weeks, or (2) active device for 2 weeks, followed by inactive device for 2 weeks. Listening and communication ratings (LIFE-R Questionnaire) were obtained at baseline and at the end of each treatment phase.

Results

Each participant demonstrated functional hearing benefits with remote-microphone use. All showed a speech perception in noise increase when the device was activated with a mean phoneme-score difference of 16.4% (p < 0.001) and reported improved listening/communication abilities in the school classroom (mean difference: 23.4%; p = 0.017).

Discussion

Conventional hearing aids are typically ineffective as a treatment for auditory neural dysfunction, making sounds louder, but not clearer for affected individuals. In this study, we demonstrate that remote-microphone technologies are acceptable/tolerable in pediatric patients with NF1 and can ameliorate their hearing deficits.

Conclusion

Remote-microphone listening systems offer a viable treatment option for children with auditory deficits associated with NF1.

Using machine learning to predict perfusionists' critical decision-making during cardiac surgery

The cardiac surgery operating room is a high-risk and complex environment in which multiple experts work as a team to provide safe and excellent care to patients. During the cardiopulmonary bypass phase of cardiac surgery, critical decisions need to be made and the perfusionists play a crucial role in assessing available information and taking a certain course of action. In this paper, we report the findings of a simulation-based study using machine learning to build predictive models of perfusionists' decision-making during critical situations in the operating room (OR). Performing 30-fold cross-validation across 30 random seeds, our machine learning approach was able to achieve an accuracy of 78.2% (95% confidence interval: 77.8% to 78.6%) in predicting perfusionists' actions, having access to only 148 simulations. The findings from this study may inform future development of computerised clinical decision support tools to be embedded into the OR, improving patient safety and surgical outcomes.

Auditory Dysfunction Among Individuals With Neurofibromatosis Type 1

IMPORTANCE

Neurofibromatosis type 1 (NF1) affects hearing through disruption of central auditory processing. The mechanisms, functional severity, and management implications are unclear.

OBJECTIVE

To investigate auditory neural dysfunction and its perceptual consequences in individuals with NF1.

DESIGN, SETTING, AND PARTICIPANTS

This case-control study included children and adults with NF1 and control participants matched on age, sex, and hearing level. Patients were recruited through specialist neurofibromatosis and neurogenetic outpatient clinics between April and September 2019. An evaluation of auditory neural activity, monaural/binaural processing, and functional hearing was conducted. Diffusion-weighted magnetic resonance imaging (MRI) data were collected from a subset of participants (10 children with NF1 and 10 matched control participants) and evaluated using a fixel-based analysis of apparent fiber density.

MAIN OUTCOMES AND MEASURES

Type and severity of auditory dysfunction evaluated via laboratory testing and questionnaire data.

RESULTS

A total of 44 participants (18 [41%] female individuals) with NF1 with a mean (SD) age of 16.9 (10.7) years and 44 control participants (18 [41%] female individuals) with a mean (SD) age of 17.2 (10.2) years were included in the study. Overall, 11 participants (25%) with NF1 presented with evidence of auditory neural dysfunction, including absent, delayed, or low amplitude electrophysiological responses from the auditory nerve and/or brainstem, compared with 1 participant (2%) in the control group (odds ratio [OR], 13.03; 95% CI, 1.59-106.95). Furthermore, 14 participants (32%) with NF1 showed clinically abnormal speech perception in background noise compared with 1 participant (2%) in the control group (OR, 20.07; 95% CI, 2.50-160.89). Analysis of diffusion-weighted MRI data of participants with NF1 showed significantly lower apparent fiber density within the ascending auditory brainstem pathways. The regions identified corresponded to the neural dysfunction measured using electrophysiological assessment.

CONCLUSIONS AND RELEVANCE

The findings of this case-control study could represent new neurobiological and clinical features of NF1. Auditory dysfunction severe enough to impede developmental progress in children and restrict communication in older participants is a common neurobiological feature of the disorder.

Fiber-Specific Changes in White Matter Microstructure in Individuals With X-Linked Auditory Neuropathy

OBJECTIVES

Auditory neuropathy (AN) is the term used to describe a group of hearing disorders, in which the hearing impairment occurs as a result of abnormal auditory nerve function. While our understanding of this condition has advanced significantly over recent years, the ability to determine the site of lesion and the extent of dysfunction in affected individuals remains a challenge. To this end, we investigated potential axonal degeneration in the white matter tracts of the brainstem in individuals with X-linked AN. We hypothesized that individuals with X-linked AN would show focal degeneration within the VIII nerve and/or auditory brainstem tracts, and the degree of degeneration would correlate with the extent of auditory perceptual impairment.

DESIGN

This was achieved using a higher-order diffusion magnetic resonance imaging (dMRI)-based quantitative measure called apparent fiber density as obtained from a technique called single-shell 3-tissue constrained spherical deconvolution and analyzed with the fixel-based analysis framework. Eleven subjects with genetically confirmed X-linked AN and 11 controls with normal hearing were assessed using behavioral and objective auditory measures. dMRI data were also collected for each participant.

RESULTS

Fixel-based analysis of the brainstem region showed that subjects with X-linked AN had significantly lower apparent fiber density in the VIII nerve compared with controls, consistent with axonal degeneration in this region. Subsequent analysis of the auditory brainstem tracts specifically showed that degeneration was also significant in these structures overall. The apparent fiber density findings were supported by objective measures of auditory function, such as auditory brainstem responses, electrocochleography, and otoacoustic emissions, which showed VIII nerve activity was severely disrupted in X-linked AN subjects while cochlear sensory hair cell function was relatively unaffected. Moreover, apparent fiber density results were significantly correlated with temporal processing ability (gap detection task) in affected subjects, suggesting that the degree of VIII nerve degeneration may impact the ability to resolve temporal aspects of an acoustic signal. Auditory assessments of sound detection, speech perception, and the processing of binaural cues were also significantly poorer in the X-linked AN group compared with the controls with normal hearing.

CONCLUSIONS

The results of this study suggest that the dMRI-based measure of apparent fiber density may provide a useful adjunct to existing auditory assessments in the characterization of the site of lesion and extent of dysfunction in individuals with AN. Additionally, the ability to determine the degree of degeneration has the potential to guide rehabilitation strategies in the future.

Prediction of Hearing Threshold in Infants Using Auditory Steady-State Evoked Potentials

This retrospective study examines the relationship between auditory steady-state evoked potential (ASSEP) thresholds determined in infancy and subsequently obtained behavioral hearing levels in children with normal hearing or varying degrees of sensorineural hearing loss. Overall, the results from 211 subjects showed that the two test techniques were highly correlated, with Pearson r values exceeding .95 at each of the audiometric test frequencies between 500 and 4000 Hz. Analysis of the findings for babies with significant hearing loss (moderate to profound levels) showed similar threshold relationships to those obtained in previous studies involving adults and older children. The results for infants with normal or near-normal hearing did, however, differ from those reported for older subjects, with behavioral thresholds typically 10 to 15 dB better than would have been predicted from their ASSEP levels.

The Auditory Steady-State Response: Comparisons with the Auditory Brainstem Response

Two studies are reported in which the threshold estimates from auditory steady-state response (ASSR) tests are compared to those of click- or toneburst-evoked auditory brainstem responses (ABRs). The first, a retrospective review of 51 cases, demonstrated that both the click-evoked ABR and the ASSR threshold estimates in infants and children could be used to predict the pure-tone threshold. The second, a prospective study of normal-hearing adults, provided evidence that the toneburst-evoked ABR and the modulated tone–evoked ASSR thresholds were similar when both were detected with an automatic detection algorithm and that threshold estimates varied with frequency, stimulus rate, and detection method. The lowest thresholds were obtained with visual detection of the ABA. The studies illustrate that ASSRs can be used to estimate pure-tone threshold in infants and children at risk for hearing loss and also in normal-hearing adults.

Wireless binaural hearing aid technology for telephone use and listening in wind noise

OBJECTIVE

To assess the speech perception benefits of binaural streaming technology for bilateral hearing aid users in two difficult listening conditions.

DESIGN

Two studies were conducted to compare hearing aid processing features relating to telephone use and wind noise. Speech perception testing was conducted in four different experimental conditions in each study.

STUDY SAMPLE

Ten bilaterally-aided children in each study.

RESULTS

Significant improvements in speech perception were obtained with a wireless feature for telephone use. Significant speech perception benefits were also obtained with wireless hearing aid features when listening to speech in simulated wind noise.

CONCLUSIONS

Binaural signal processing algorithms can significantly improve speech perception for bilateral hearing aid users in challenging listening situations.

Mild-moderate congenital hearing loss: secular trends in outcomes across four systems of detection

BACKGROUND

Universal newborn hearing screening (UNHS) targets moderate or greater hearing loss. However, UNHS also frequently detects children with mild loss that results in many receiving early treatment. The benefits of this approach are not yet established. We aimed to (i) compare language and psychosocial outcomes between four hearing loss detection systems for children aged 5-8 years with congenital mild-moderate hearing loss; (ii) determine whether age of detection predicts outcomes; and (iii) compare outcomes between children identified via well-established UNHS and the general population.

METHODS

Linear regression adjusted for potential confounding factors was used throughout. Via a quasi-experimental design, language and psychosocial outcomes were compared across four population-based Australian systems of hearing loss detection: opportunistic detection, born 1991-1993, n = 50; universal risk factor referral, born 2003-2005, n = 34; newly established UNHS, born 2003-2005, n = 41; and well-established UNHS, born 2007-2010, n = 21. In pooled analyses, we examined whether age of detection predicted outcomes. Outcomes were similarly compared between the current well-established UNHS system and typically developing children in the Early Language in Victoria Study, born 2003, n = 1217.

RESULTS

Age at diagnosis and hearing aid fitting fell steadily across the four systems. For moderate losses, mean expressive language (P for trend .05) and receptive vocabulary (P for trend .06) improved across the four systems, but benefit was not obvious for mild losses. In pooled analyses, diagnosis before age six months predicted better language outcomes for moderate losses. Children with mild-moderate losses exposed to well-established UNHS continue to experience expressive language scores well below children in the general population (adjusted mean difference -8.9 points, 95% CI -14.7 to -3.1).

CONCLUSIONS

Treatment arising from UNHS appears to be clearly benefitting children with moderate hearing losses. However, rigorous trials are needed to quantify benefits, versus costs and potential harms, of early aiding of children with mild losses.

Measuring Inhibition and Cognitive Flexibility in Friedreich Ataxia

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder with subtle impact on cognition. Inhibitory processes and cognitive flexibility were examined in FRDA by assessing the ability to suppress a predictable verbal response. We administered the Hayling Sentence Completion Test (HSCT), the Trail Making Test, and the Stroop Test to 43 individuals with FRDA and 42 gender- and age-matched control participants. There were no significant group differences in performance on the Stroop or Trail Making Test whereas significant impairment in cognitive flexibility including the ability to predict and inhibit a pre-potent response as measured in the HSCT was evident in individuals with FRDA. These deficits did not correlate with clinical characteristics of FRDA (age of disease onset, disease duration, number of guanine-adenine-adenine repeats on the shorter or larger FXN allele, or Friedreich Ataxia Rating Scale score), suggesting that such impairment may not be related to the disease process in a straightforward way. The observed specific impairment of inhibition and predictive capacity in individuals with FRDA on the HSCT task, in the absence of impairment in associated executive functions, supports cerebellar dysfunction in conjunction with disturbance to cortico-thalamo-cerebellar connectivity, perhaps via inability to access frontal areas necessary for successful task completion.

Auditory neuropathy in a patient with hemochromatosis

OBJECTIVE

To evaluate the auditory function of an individual with genetically confirmed hemochromatosis.

METHODS

A 57 year old male with mildly impaired sound detection thresholds underwent a range of behavioural, electroacoustic and electrophysiologic assessments. These included the recording of otoacoustic emissions and auditory brainstem responses, measurement of monaural temporal resolution and evaluation of binaural speech processing. Findings for this patient were subsequently compared with those of 80 healthy controls with similar audiometric thresholds.

RESULTS

The patient showed the three cardinal features of auditory neuropathy, presenting with evidence of normal cochlear outer hair cell function, disrupted neural activity in the auditory nerve/brainstem and impaired temporal processing. His functional hearing ability (speech perception) was significantly affected and suggested a reduced capacity to use localization cues to segregate signals in the presence of background noise.

CONCLUSION

We present the first case of an individual with hemochromatosis and auditory neuropathy. The findings for this patient highlight the need for careful evaluation of auditory function in individuals with the disorder.

Maturation of the Central Auditory Nervous System in Children with Auditory Processing Disorder

Neurodevelopmental delay has been proposed as the underlying cause of the majority of cases of auditory processing disorder (APD). The current study employs the cortical auditory evoked potential (CAEP) to assess if maturational differences of the central auditory nervous system (CANS) can be identified between children who do and do not meet the diagnostic criterion for APD. The P1-N1 complex of the CAEP has previously been used for tracking development of the CANS in children with hearing impairment. Twenty-seven children (7 to 12 years old) who failed an APD behavioral test battery were age-matched (within 3 months) to children who had passed the same battery. CAEP responses to 500-Hz tone burst stimuli were recorded and analyzed for latency and amplitude measures. The P1-N1 complex of the CAEP, which has previously been used for tracking development of the CANS in children with hearing impairment, showed significant group differences. The children diagnosed with APD showed significantly increased latency (∼10 milliseconds) and significantly reduced amplitude (∼10 μV) of the early components of the CAEP compared with children with normal auditory processing. No significant differences were seen in the later P2 wave. The normal developmental course is for a decrease in latency and increase in amplitude as a function of age. The results of this study are, therefore, consistent with an immaturity of the CANS as an underlying cause of APD in children.

Functional hearing deficits in children with Type 1 diabetes

AIM

Hearing loss (as reflected by abnormal sound detection) is a frequently reported consequence of Type 1 diabetes mellitus. We sought to evaluate sound detection, auditory neural function and binaural processing ability in a group of school-aged participants with Type 1 diabetes and to assess their functional hearing and general communication ability.

METHODS

A range of electroacoustic, electrophysiological and behavioural test techniques were used to evaluate both cochlear and auditory neural function in 19 affected children. A cohort of matched controls was also assessed.

RESULTS

Although all of the participants with Type 1 diabetes enjoyed normal sound detection, 9 of the 19 (47%) showed evidence of auditory pathway abnormality with evoked potential latencies and/or amplitudes beyond age-related norms. Auditory brainstem response interpeak latencies (wave I-V) were longer than in matched controls [ 95% confidence interval (95% CI); 0.10, 0.28 ms: P < 0.001] and wave V amplitudes were reduced (95% CI; -0.21, 0.00 μV: P = 0.02). Binaural speech perception in noise was also impaired (95% CI; 0.82, 3.17 dB: P = 0.002) and perceptual ability was correlated with degree of neural disruption in the auditory brainstem (r = 0.662, P = 0.003).

CONCLUSIONS

Hearing deficits severe enough to restrict communication and threaten academic progress were common on our group of school-aged children with Type 1 diabetes. Evaluation of both cochlear and auditory neural function may form an important part of the standard management regime for children with diabetes.

Pathophysiological mechanisms and functional hearing consequences of auditory neuropathy

The effects of inner ear abnormality on audibility have been explored since the early 20th century when sound detection measures were first used to define and quantify 'hearing loss'. The development in the 1970s of objective measures of cochlear hair cell function (cochlear microphonics, otoacoustic emissions, summating potentials) and auditory nerve/brainstem activity (auditory brainstem responses) have made it possible to distinguish both synaptic and auditory nerve disorders from sensory receptor loss. This distinction is critically important when considering aetiology and management. In this review we address the clinical and pathophysiological features of auditory neuropathy that distinguish site(s) of dysfunction. We describe the diagnostic criteria for: (i) presynaptic disorders affecting inner hair cells and ribbon synapses; (ii) postsynaptic disorders affecting unmyelinated auditory nerve dendrites; (iii) postsynaptic disorders affecting auditory ganglion cells and their myelinated axons and dendrites; and (iv) central neural pathway disorders affecting the auditory brainstem. We review data and principles to identify treatment options for affected patients and explore their benefits as a function of site of lesion.

An open-label trial in Friedreich ataxia suggests clinical benefit with high-dose resveratrol, without effect on frataxin levels

Friedreich ataxia (FRDA) is due to a triplet repeat expansion in FXN, resulting in deficiency of the mitochondrial protein frataxin. Resveratrol is a naturally occurring polyphenol, identified to increase frataxin expression in cellular and mouse models of FRDA and has anti-oxidant properties. This open-label, non-randomized trial evaluated the effect of two different doses of resveratrol on peripheral blood mononuclear cell (PBMC) frataxin levels over a 12-week period in individuals with FRDA. Secondary outcome measures included PMBC FXN mRNA, oxidative stress markers, and clinical measures of disease severity. Safety and tolerability were studied. Twenty-four participants completed the study; 12 received low-dose resveratrol (1 g daily) and 12 high-dose resveratrol (5 g daily). PBMC frataxin levels did not change in either dosage group [low-dose group change: 0.08 pg/μg protein (95% CI -0.05, 0.21, p = 0.21); high-dose group change: 0.03 pg/μg protein (95% CI -0.10, 0.15, p = 0.62)]. Improvement in neurologic function was evident in the high-dose group [change in Friedreich Ataxia Rating Scale -3.4 points, 95% CI (-6.6, -0.3), p = 0.036], but not the low-dose group. Significant improvements in audiologic and speech measures, and in the oxidative stress marker plasma F2-isoprostane were demonstrated in the high-dose group only. There were no improvements in cardiac measures or patient-reported outcome measures. No serious adverse events were recorded. Gastrointestinal side-effects were a common, dose-related adverse event. This open-label study shows no effect of resveratrol on frataxin levels in FRDA, but suggests that independent positive clinical and biologic effects of high-dose resveratrol may exist. Further assessment of efficacy is warranted in a randomized placebo-controlled trial.

Auditory neuropathy

Neural disorders of the auditory nerve are associated with particular disorders of auditory perceptions dependent on processing of acoustic temporal cues. These include: (1) speech perception; (2) localizing a sound's origin in space; and (3) identifying sounds in background noise. Auditory neuropathy (AN) is a consequence of: (1) presynaptic disorders affecting inner hair cell ribbon synapses; (2) postsynaptic disorders of auditory nerve dendrites; and (3) postsynaptic disorders of auditory nerve axons. The etiologies of these disorders are diverse, similar to other cranial or peripheral neuropathies. The pathologies cause attenuated and dyssynchronous auditory nerve discharges. Therapies and management of patients with AN are reviewed.

Auditory neuropathy in individuals with Type 1 diabetes

Peripheral neuropathy is a major consequence of diabetes mellitus with up to 50 % of patients showing clinically significant neural injury during the disease course. Hearing loss (as defined by impaired sound detection thresholds) is a recognized symptom of DM, but the possibility of auditory neuropathy (AN) has not been explored in this population. This pilot study investigated peripheral auditory function, auditory processing and speech perception in individuals with Type 1 diabetes mellitus (T1DM) and compared the findings with measures of vestibular function, ocular pathology/visual acuity and overall neurologic profile. Ten adults with T1DM and ten matched controls underwent a battery of tests which included: audiometry, otoacoustic emissions, auditory brainstem responses, temporal processing measures and speech perception. Six of the ten T1DM participants showed electrophysiologic evidence of AN and impaired functional hearing. Furthermore, auditory capacity was correlated with both visual acuity and degree of somatic peripheral neuropathy. This pilot investigation revealed functional-hearing deficits severe enough to impact upon everyday communication. Should the findings be confirmed by larger studies, auditory evaluation may form an important part of the management regimen for individuals with T1DM. This may be especially important for those with DM-related eye conditions, as deficits across multiple sensory modalities can have multiplicative detrimental effects on quality-of-life.

The use of listening devices to ameliorate auditory deficit in children with autism

OBJECTIVES

To evaluate both monaural and binaural processing skills in a group of children with autism spectrum disorder (ASD) and to determine the degree to which personal frequency modulation (radio transmission) (FM) listening systems could ameliorate their listening difficulties.

STUDY DESIGN

Auditory temporal processing (amplitude modulation detection), spatial listening (integration of binaural difference cues), and functional hearing (speech perception in background noise) were evaluated in 20 children with ASD. Ten of these subsequently underwent a 6-week device trial in which they wore the FM system for up to 7 hours per day.

RESULTS

Auditory temporal processing and spatial listening ability were poorer in subjects with ASD than in matched controls (temporal: P = .014 [95% CI -6.4 to -0.8 dB], spatial: P = .003 [1.0 to 4.4 dB]), and performance on both of these basic processing measures was correlated with speech perception ability (temporal: r = -0.44, P = .022; spatial: r = -0.50, P = .015). The provision of FM listening systems resulted in improved discrimination of speech in noise (P < .001 [11.6% to 21.7%]). Furthermore, both participant and teacher questionnaire data revealed device-related benefits across a range of evaluation categories including Effect of Background Noise (P = .036 [-60.7% to -2.8%]) and Ease of Communication (P = .019 [-40.1% to -5.0%]). Eight of the 10 participants who undertook the 6-week device trial remained consistent FM users at study completion.

CONCLUSIONS

Sustained use of FM listening devices can enhance speech perception in noise, aid social interaction, and improve educational outcomes in children with ASD.

A new locus for X-linked dominant Charcot-Marie-Tooth disease (CMTX6) is caused by mutations in the pyruvate dehydrogenase kinase isoenzyme 3 (PDK3) gene

Hereditary motor and sensory disorders of the peripheral nerve form one of the most common groups of human genetic diseases collectively called Charcot-Marie-Tooth (CMT) neuropathy. Using linkage analysis in a three generation kindred, we have mapped a new locus for X-linked dominant CMT to chromosome Xp22.11. A microsatellite scan of the X chromosome established significant linkage to several markers including DXS993 (Zmax = 3.16; θ = 0.05). Extended haplotype analysis refined the linkage region to a 1.43-Mb interval flanked by markers DXS7110 and DXS8027. Whole exome sequencing identified a missense mutation c.G473A (p.R158H) in the pyruvate dehydrogenase kinase isoenzyme 3 (PDK3) gene. The change localized within the 1.43-Mb linkage interval, segregated with the affected phenotype and was excluded in ethnically matched control chromosomes. PDK3 is one of the four isoenzymes regulating the pyruvate dehydrogenase complex (PDC), by reversible phosphorylation, and is a nuclear-coded protein located in the mitochondrial matrix. PDC catalyzes the oxidative decarboxylation of pyruvate to acetyl CoA and is a key enzyme linking glycolysis to the energy-producing Krebs cycle and lipogenic pathways. We found that the R158H mutation confers enzyme hyperactivity and binds with stronger affinity than the wild-type to the inner-lipoyl (L2) domain of the E2p chain of PDC. Our findings suggest a reduced pyruvate flux due to R158H mutant PDK3-mediated hyper-phosphorylation of the PDC as the underlying pathogenic cause of peripheral neuropathy. The results highlight an important causative link between peripheral nerve degeneration and an essential bioenergetic or biosynthetic pathway required for the maintenance of peripheral nerves.

Auditory and visual temporal processing disruption in open angle glaucoma

PURPOSE

Open angle glaucoma (OAG) is increasingly being viewed as an age-related neurodegenerative condition that may occur in individuals who are innately susceptible to global (autonomic) neural injury. Recent data support the plausibility of auditory neural impairment in a proportion of individuals with OAG, with results showing a key disruption to processing temporal properties of sound. This study tested the hypothesis that temporal processing deficits consistent with central (cortical) processing abnormalities are present in both the visual and auditory domains in individuals with glaucoma.

METHODS

A series of tasks designed to test progressively more complex aspects of temporal processing were conducted in 25 OAG individuals and 25 age- and sex-matched controls. For audition, baseline measurement of hearing sensitivity was followed by functional assessment of amplitude modulation detection, frequency discrimination at two reference levels, and speech perception. For vision, measures of foveal temporal contrast detection at two flicker rates, speed discrimination at two reference velocities, and coherent global motion detection were assessed.

RESULTS

A significant proportion of the OAG cohort displayed an impairment in auditory low-frequency discrimination, speech perception, visual speed discrimination for slow velocities and/or visual global motion detection, compared to controls (36%, 25%, 39%, and 34% respectively, were outside the 90th percentile of control performance; P < 0.05).

CONCLUSIONS

A subgroup of individuals with OAG displayed impaired auditory temporal processing concurrent with signs of visual temporal processing impairment. These temporal processing deficits were in the presence of normal sound detection and normal central luminance increment thresholds.

Auditory processing deficits in children with Friedreich ataxia

Friedreich ataxia is a neurodegenerative disease with an average age of onset of 10 years. The authors sought to investigate the presence and functional consequences of auditory neuropathy in a group of affected children and to evaluate the ability of personal FM-listening systems to improve perception. Nineteen school-aged individuals with Friedreich ataxia and a cohort of matched control subjects underwent a battery of auditory function tests. Sound detection was relatively normal, but auditory temporal processing and speech understanding in noise were severely impaired, with children with Friedreich ataxia typically able to access less than 40% of the information available to controls. Use of FM-listening devices did, however, improve the speech perception performance of those with Friedreich ataxia to the level of their unaffected peers in conditions designed to replicate the listening environment of the average school classroom.

Auditory function in children with Charcot-Marie-Tooth disease

The peripheral manifestations of the inherited neuropathies are increasingly well characterized, but their effects upon cranial nerve function are not well understood. Hearing loss is recognized in a minority of children with this condition, but has not previously been systemically studied. A clear understanding of the prevalence and degree of auditory difficulties in this population is important as hearing impairment can impact upon speech/language development, social interaction ability and educational progress. The aim of this study was to investigate auditory pathway function, speech perception ability and everyday listening and communication in a group of school-aged children with inherited neuropathies. Twenty-six children with Charcot-Marie-Tooth disease confirmed by genetic testing and physical examination participated. Eighteen had demyelinating neuropathies (Charcot-Marie-Tooth type 1) and eight had the axonal form (Charcot-Marie-Tooth type 2). While each subject had normal or near-normal sound detection, individuals in both disease groups showed electrophysiological evidence of auditory neuropathy with delayed or low amplitude auditory brainstem responses. Auditory perception was also affected, with >60% of subjects with Charcot-Marie-Tooth type 1 and >85% of Charcot-Marie-Tooth type 2 suffering impaired processing of auditory temporal (timing) cues and/or abnormal speech understanding in everyday listening conditions.

Interhemispheric transfer time in patients with auditory hallucinations: an auditory event-related potential study

Central auditory processing in schizophrenia patients with a history of auditory hallucinations has been reported to be impaired, and abnormalities of interhemispheric transfer have been implicated in these patients. This study examined interhemispheric functional connectivity between auditory cortical regions, using temporal information obtained from latency measures of the auditory N1 evoked potential. Interhemispheric Transfer Times (IHTTs) were compared across 3 subject groups: schizophrenia patients who had experienced auditory hallucinations, schizophrenia patients without a history of auditory hallucinations, and normal controls. Pure tones and single-syllable words were presented monaurally to each ear, while EEG was recorded continuously. IHTT was calculated for each stimulus type by comparing the latencies of the auditory N1 evoked potential recorded contralaterally and ipsilaterally to the ear of stimulation. The IHTTs for pure tones did not differ between groups. For word stimuli, the IHTT was significantly different across the 3 groups: the IHTT was close to zero in normal controls, was highest in the AH group, and was negative (shorter latencies ipsilaterally) in the nonAH group. Differences in IHTTs may be attributed to transcallosal dysfunction in the AH group, but altered or reversed cerebral lateralization in nonAH participants is also possible.

Auditory perception in individuals with Friedreich's ataxia

INTRODUCTION

Friedreich's ataxia (FRDA) is an inherited ataxia with a range of progressive features including axonal degeneration of sensory nerves. The aim of this study was to investigate auditory perception in affected individuals.

METHODS

Fourteen subjects with genetically defined FRDA participated. Two control groups, one consisting of healthy, normally hearing individuals and another comprised of subjects with sensorineural hearing loss, were also assessed. Auditory processing was evaluated using structured tasks designed to reveal the listeners' ability to perceive temporal and spectral cues. Findings were then correlated with open-set speech understanding.

RESULTS

Nine of 14 individuals with FRDA showed evidence of auditory processing disorder. Gap and amplitude modulation detection levels in these subjects were significantly elevated, indicating impaired encoding of rapid signal changes. Electrophysiologic findings (auditory brainstem response, ABR) also reflected disrupted neural activity. Speech understanding was significantly affected in these listeners and the degree of disruption was related to temporal processing ability. Speech analyses indicated that timing cues (notably consonant voice onset time and vowel duration) were most affected.

CONCLUSION

The results suggest that auditory pathway abnormality is a relatively common consequence of FRDA. Regular auditory evaluation should therefore be part of the management regime for all affected individuals. This assessment should include both ABR testing, which can provide insights into the degree to which auditory neural activity is disrupted, and some functional measure of hearing capacity such as speech perception assessment, which can quantify the disorder and provide a basis for intervention.

Cochlear Implant Outcomes for Children With Auditory Neuropathy Spectrum Disorder

Cochlear implantation is currently the intervention option of choice for many children with auditory neuropathy spectrum disorder (ANSD) who are unable to obtain benefit from conventional amplification. The aim of this study was to review the speech perception and language outcomes for children with ANSD who had received a cochlear implant and highlight specific clinical considerations for working with this population of children with hearing impairment who are being considered for implantation. Finds for the group of 17 children with ANSD using cochlear implants were compared to previously reported outcomes for children with sensori-neural (SN) type hearing loss using cochlear implants.

Two children, identified with cochlear nerve deficiency pre-operatively, received no useful auditory percepts from their cochlear implant and discontinued device use. The remaining children demonstrated speech perception and language outcomes comparable to those observed for SN hearing loss peers using cochlear implants.

This paper highlights a number of considerations for clinicians to be aware of and the importance of careful counseling pre-operatively regarding the potential for less-than-optimal outcomes, particularly for those children identified with cochlear nerve deficiency.

A comparison of 40 Hz auditory steady-state response (ASSR) and cortical auditory evoked potential (CAEP) thresholds in awake adult subjects

Evoked potential thresholds using the 40 Hz auditory steady-state response (ASSR) and cortical auditory evoked potential (CAEP) were recorded at 500 Hz and 4000 Hz test frequencies in 36 subjects with normal acuity, and 30 subjects with sensorineural hearing loss. ASSR threshold sensation levels (SLs) were lower in ears with greater degrees of hearing loss, and for the 500 Hz stimulus. Mean SLs (maximum duration of a single recording: 89 seconds) were as follows at 500 Hz and 4000 Hz respectively: normal hearing group, 16.9+/-10.3 dB and 42.4+/-14.4 dB; mild-moderate group, 10.6+/-8.8 dB and 23.8+/-8.1 dB; severe-profound group, 10.0+/-13.2 dB and 21.5+/-18.9 dB. CAEP SLs showed no change with hearing level and CAEP/behavioural differences were similar at each test frequency. Mean SLs for CAEP threshold (single recording duration: 84 seconds) at 500 Hz and 4000 Hz respectively were: normal hearing group, 10.3+/-6.4 dB and 11.5+/-3.8 dB; mild-moderate group, 8.4+/-7.4 dB and 13.2+/-12.4 dB; severe-profound group, 11.0+/-6.6 dB and 15.9+/-16.4 dB. The results of this study suggest that while both 40 Hz ASSR and CAEP can reflect the behavioural audiogram, CAEPs may provide a more reliable estimate of hearing in awake adults.

Speech perception ability in individuals with Friedreich ataxia

The aim of this study was to investigate auditory pathway function and speech perception ability in individuals with Friedreich ataxia (FRDA). Ten subjects confirmed by genetic testing as being homozygous for a GAA expansion in intron 1 of the FXN gene were included. While each of the subjects demonstrated normal, or near normal sound detection, 3 of the 10 showed electrophysiological evidence of auditory pathway disorder [presenting with the auditory neuropathy/dyssynchrony (AN/AD) result pattern], and 9 of the 10 showed abnormal speech understanding when tested with levels of background noise typical of everyday listening conditions. Information transmission analyses of the speech perception findings for the three FRDA subjects with AN/AD type hearing loss when compared with those of a cohort of individuals with peripheral [sensorineural (SN)] hearing loss, showed a distinct pattern of perceptual disruption. Where the listeners with SN loss confused sounds on the basis of frequency (pitch) differences, the FRDA subjects with AN/AD made errors that reflected an inability to perceive temporal (timing) cues in the speech sounds.