Audiology and Speech Pathology - Research Publications
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ItemNo Preview AvailableHuman stem cells ameliorate auditory evoked responses in a model of neuropathy(BIOMED CENTRAL LTD, 2012-11-08)Stem cells have been touted as a potential source of replacement cells for the treatment of severe-to-profoundly deaf individuals, including possible combined therapy with a cochlear implant. The success of such a therapy is dependent on a number of factors, but of critical importance is the functional incorporation of transplanted cells into the peripheral and central auditory systems. In a major breakthrough, Chen and colleagues recently reported the restoration of hearing thresholds by up to 46% following the transplantation of human pluripotent stem cells in a rodent auditory neuropathy model. Improved function was matched with new synapse formation in the peripheral and central aspects of the auditory system. The findings have promising clinical implications for patients with auditory neuropathy. Still to be elucidated are the long-term survival and function of transplanted cells, the precise mechanism by which hearing is restored, and whether further improvement is possible when combined with electrical stimulation from a cochlear implant.
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ItemInner Ear Morphology Is Perturbed in Two Novel Mouse Models of Recessive Deafness(PUBLIC LIBRARY SCIENCE, 2012-12-12)Human MYO7A mutations can cause a variety of conditions involving the inner ear. These include dominant and recessive non-syndromic hearing loss and syndromic conditions such as Usher syndrome. Mouse models of deafness allow us to investigate functional pathways involved in normal and abnormal hearing processes. We present two novel mouse models with mutations in the Myo7a gene with distinct phenotypes. The mutation in Myo7a(I487N/I487N) ewaso is located within the head motor domain of Myo7a. Mice exhibit a profound hearing loss and manifest behaviour associated with a vestibular defect. A mutation located in the linker region between the coiled-coil and the first MyTH4 domains of the protein is responsible in Myo7a(F947I/F947I) dumbo. These mice show a less severe hearing loss than in Myo7a(I487N/I487N) ewaso; their hearing loss threshold is elevated at 4 weeks old, and progressively worsens with age. These mice show no obvious signs of vestibular dysfunction, although scanning electron microscopy reveals a mild phenotype in vestibular stereocilia bundles. The Myo7a(F947I/F947I) dumbo strain is therefore the first reported Myo7a mouse model without an overt vestibular phenotype; a possible model for human DFNB2 deafness. Understanding the molecular basis of these newly identified mutations will provide knowledge into the complex genetic pathways involved in the maintenance of hearing, and will provide insight into recessively inherited sensorineural hearing loss in humans.
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ItemNeurotrophin Gene Therapy for Sustained Neural Preservation after Deafness(PUBLIC LIBRARY SCIENCE, 2012-12-17)The cochlear implant provides auditory cues to profoundly deaf patients by electrically stimulating the residual spiral ganglion neurons. These neurons, however, undergo progressive degeneration after hearing loss, marked initially by peripheral fibre retraction and ultimately culminating in cell death. This research aims to use gene therapy techniques to both hold and reverse this degeneration by providing a sustained and localised source of neurotrophins to the deafened cochlea. Adenoviral vectors containing green fluorescent protein, with or without neurotrophin-3 and brain derived neurotrophic factor, were injected into the lower basal turn of scala media of guinea pigs ototoxically deafened one week prior to intervention. This single injection resulted in localised and sustained gene expression, principally in the supporting cells within the organ of Corti. Guinea pigs treated with adenoviral neurotrophin-gene therapy had greater neuronal survival compared to contralateral non-treated cochleae when examined at 7 and 11 weeks post injection. Moreover; there was evidence of directed peripheral fibre regrowth towards cells expressing neurotrophin genes after both treatment periods. These data suggest that neurotrophin-gene therapy can provide sustained protection of spiral ganglion neurons and peripheral fibres after hearing loss.
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ItemThe Sound Sensation of Apical Electric Stimulation in Cochlear Implant Recipients with Contralateral Residual Hearing(PUBLIC LIBRARY SCIENCE, 2012-06-19)BACKGROUND: Studies using vocoders as acoustic simulators of cochlear implants have generally focused on simulation of speech understanding, gender recognition, or music appreciation. The aim of the present experiment was to study the auditory sensation perceived by cochlear implant (CI) recipients with steady electrical stimulation on the most-apical electrode. METHODOLOGY/PRINCIPAL FINDINGS: Five unilateral CI users with contralateral residual hearing were asked to vary the parameters of an acoustic signal played to the non-implanted ear, in order to match its sensation to that of the electric stimulus. They also provided a rating of similarity between each acoustic sound they selected and the electric stimulus. On average across subjects, the sound rated as most similar was a complex signal with a concentration of energy around 523 Hz. This sound was inharmonic in 3 out of 5 subjects with a moderate, progressive increase in the spacing between the frequency components. CONCLUSIONS/SIGNIFICANCE: For these subjects, the sound sensation created by steady electric stimulation on the most-apical electrode was neither a white noise nor a pure tone, but a complex signal with a progressive increase in the spacing between the frequency components in 3 out of 5 subjects. Knowing whether the inharmonic nature of the sound was related to the fact that the non-implanted ear was impaired has to be explored in single-sided deafened patients with a contralateral CI. These results may be used in the future to better understand peripheral and central auditory processing in relation to cochlear implants.
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ItemPre-, Per- and Postoperative Factors Affecting Performance of Postlinguistically Deaf Adults Using Cochlear Implants: A New Conceptual Model over Time(PUBLIC LIBRARY SCIENCE, 2012-11-09)OBJECTIVE: To test the influence of multiple factors on cochlear implant (CI) speech performance in quiet and in noise for postlinguistically deaf adults, and to design a model of predicted auditory performance with a CI as a function of the significant factors. STUDY DESIGN: Retrospective multi-centre study. METHODS: Data from 2251 patients implanted since 2003 in 15 international centres were collected. Speech scores in quiet and in noise were converted into percentile ranks to remove differences between centres. The influence of 15 pre-, per- and postoperative factors, such as the duration of moderate hearing loss (mHL), the surgical approach (cochleostomy or round window approach), the angle of insertion, the percentage of active electrodes, and the brand of device were tested. The usual factors, duration of profound HL (pHL), age, etiology, duration of CI experience, that are already known to have an influence, were included in the statistical analyses. RESULTS: The significant factors were: the pure tone average threshold of the better ear, the brand of device, the percentage of active electrodes, the use of hearing aids (HAs) during the period of pHL, and the duration of mHL. CONCLUSIONS: A new model was designed showing a decrease of performance that started during the period of mHL, and became faster during the period of pHL. The use of bilateral HAs slowed down the related central reorganization that is the likely cause of the decreased performance.
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ItemSpeech Perception and Localisation with SCORE Bimodal: A Loudness Normalisation Strategy for Combined Cochlear Implant and Hearing Aid Stimulation(PUBLIC LIBRARY SCIENCE, 2012-10-24)A significant fraction of newly implanted cochlear implant recipients use a hearing aid in their non-implanted ear. SCORE bimodal is a sound processing strategy developed for this configuration, aimed at normalising loudness perception and improving binaural loudness balance. Speech perception performance in quiet and noise and sound localisation ability of six bimodal listeners were measured with and without application of SCORE. Speech perception in quiet was measured either with only acoustic, only electric, or bimodal stimulation, at soft and normal conversational levels. For speech in quiet there was a significant improvement with application of SCORE. Speech perception in noise was measured for either steady-state noise, fluctuating noise, or a competing talker, at conversational levels with bimodal stimulation. For speech in noise there was no significant effect of application of SCORE. Modelling of interaural loudness differences in a long-term-average-speech-spectrum-weighted click train indicated that left-right discrimination of sound sources can improve with application of SCORE. As SCORE was found to leave speech perception unaffected or to improve it, it seems suitable for implementation in clinical devices.
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ItemImproving outcomes of preschool language delay in the community: protocol for the Language for Learning randomised controlled trial(BMC, 2012-07-09)BACKGROUND: Early language delay is a high-prevalence condition of concern to parents and professionals. It may result in lifelong deficits not only in language function, but also in social, emotional/behavioural, academic and economic well-being. Such delays can lead to considerable costs to the individual, the family and to society more widely. The Language for Learning trial tests a population-based intervention in 4 year olds with measured language delay, to determine (1) if it improves language and associated outcomes at ages 5 and 6 years and (2) its cost-effectiveness for families and the health care system. METHODS/DESIGN: A large-scale randomised trial of a year-long intervention targeting preschoolers with language delay, nested within a well-documented, prospective, population-based cohort of 1464 children in Melbourne, Australia. All children received a 1.25-1.5 hour formal language assessment at their 4th birthday. The 200 children with expressive and/or receptive language scores more than 1.25 standard deviations below the mean were randomised into intervention or 'usual care' control arms. The 20-session intervention program comprises 18 one-hour home-based therapeutic sessions in three 6-week blocks, an outcome assessment, and a final feed-back/forward planning session. The therapy utilises a 'step up-step down' therapeutic approach depending on the child's language profile, severity and progress, with standardised, manualised activities covering the four language development domains of: vocabulary and grammar; narrative skills; comprehension monitoring; and phonological awareness/pre-literacy skills. Blinded follow-up assessments at ages 5 and 6 years measure the primary outcome of receptive and expressive language, and secondary outcomes of vocabulary, narrative, and phonological skills. DISCUSSION: A key strength of this robust study is the implementation of a therapeutic framework that provides a standardised yet tailored approach for each child, with a focus on specific language domains known to be associated with later language and literacy. The trial responds to identified evidence gaps, has outcomes of direct relevance to families and the community, includes a well-developed economic analysis, and has the potential to improve long-term consequences of early language delay within a public health framework. TRIAL REGISTRATION: Current Controlled Trials ISRCTN03981121.
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ItemNo Preview AvailableDifferentiating profiles of speech impairments in Friedreich's ataxia: a perceptual and instrumental approach(WILEY, 2012)BACKGROUND: The speech disorder associated with Friedreich's ataxia (FRDA) is classically described as ataxic dysarthria. However, variable neuropathology beyond the cerebellum, which may include the corticospinal and corticobulbar tracts, means that the dysarthria can be mixed rather than a pure ataxic dysarthria. AIMS: To characterize physiological features of the dysarthria associated with FRDA and identify differential patterns of deviation that may occur across the subsystems of the speech-production mechanism in a series of seven case studies. METHODS & PROCEDURES: The assessment battery included a perceptual analysis of a speech sample using an interval rating scale, and a range of instrumental measures to investigate the respiratory, laryngeal, velopharyngeal and articulatory systems. OUTCOMES & RESULTS: The results demonstrated the variability that exists in the dysarthria associated with FRDA, highlighting the existence of differential profiles of speech impairment. A particular distinction was observed between the presence of hypernasality and phonatory dysfunction, as evidenced by the instrumental results. CONCLUSIONS & IMPLICATIONS: The distinct profiles of dysarthria associated with FRDA indicate that approaches that address multiple subsystems are necessary for the accurate characterization and quantification of the motor speech disorder. Further research is required to investigate the decline in speech function as the disease progresses, as changes in speech function over time may be a good indicator of neurological decline in FRDA.
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ItemNo Preview AvailableIs age or culture important for the use of speech as a marker of depression?(Frontiers Research Foundation, 2012)Speech is a marker of depression severity and treatment response. Following on from a multisite randomised control trial which demonstrated the feasibility and validity of obtaining neurophysiologically based acoustic measures of depression in 25-65 year old English speakers, we sought to determine the efficacy of the methods in related clinically important cohorts: defined by age and language. 125 adults with major depression were recruited into an 8-week, open label observational study. Four cohorts were included: two English speaking groups (‘younger’ (n= 38) (18-25 years) and ‘older’ (n=27) (60-78 years)) and two Chinese speaking groups (Mandarin (n=29) and Cantonese speakers (n=31)). Participants beginning new treatments for depression were clinically evaluated at baseline, study midpoint (4 weeks), and end-point (8 weeks). After face to face assessment, participants completed the Quick Inventory of Depressive Symptomatology - Interactive Voice Response (QIDS-IVR) version using touch-tone telephones. Speech samples were also recorded for analysis of acoustic characteristics as clinical markers of depression severity and response to treatment. Timing-based measures of speech production, particularly during the performance of automatic speech tasks, showed the most significant correlations with overall depression severity. Specifically, associations between depression severity and total recording durations, pause times, pause variability, and speaking rates were consistent with previous studies. Few acoustic markers of speech, however, were significantly correlated with treatment response. Speech was significantly correlated with depression severity in all groups. Altered speech production and its relationship with clinician defined clinician treatment response was not clearly demonstrated, possibility due to low treatment response rates.
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ItemNo Preview AvailableHealth care utilisation following hospitalisation for transport-related injury(ELSEVIER SCI LTD, 2012-09)BACKGROUND: Transport injuries are a substantial cause of disability and death internationally. There is little published information regarding patterns of healthcare utilisation following transport injury. AIMS: To investigate patterns of in-hospital and post-discharge healthcare use following transport injury. METHODS: Analysis of all accepted adult claims from the database of the transport accident compensation regulator in Victoria, Australia between 1995 and 2008. The analyses focused on injuries resulting in hospitalisation. Indicators of in-hospital and post-discharge healthcare utilisation (e.g. number of services per practitioner group) within the first 12-months were summarised. RESULTS: More than a third (33.6%, n = 68,639) of all accepted compensable transport injuries resulted in admission to an acute care facility within 28 days of injury. In this group, the compensation authority paid for a total of 4.5 million healthcare services in the 12 months post-discharge (median of 19 services per claim). Services provided by medical practitioners were accessed by nearly all claimants (95.7%) at a median of 11 (5-26) per claimant. Less than half of claimants (46.7%) accessed paramedical or allied health services but the median number of services accessed was higher at 29 (9-82) per claimant. CONCLUSION: Transport-related injury cases require a substantial interaction with multiple components of the healthcare system in the year following hospital discharge. Compensation system data may provide a detailed understanding of healthcare utilisation, a key element of injury burden.