Showing papers by "Cochlear Limited published in 2011"

Use it or lose it? Lessons learned from the developing brains of children who are deaf and use cochlear implants to hear.

Abstract: In the present paper, we review what is currently known about the effects of deafness on the developing human auditory system and ask: Without use, does the immature auditory system lose the ability to normally function and mature? Any change to the structure or function of the auditory pathways resulting from a lack of activity will have important implications for future use through an auditory prosthesis such as a cochlear implant. Data to date show that deafness in children arrests and disrupts normal auditory development. Multiple changes to the auditory pathways occur during the period of deafness with the extent and type of change being dependent upon the age and stage of auditory development at onset of deafness, the cause or type of deafness, and the length of time the immature auditory pathways are left without significant input. Structural changes to the auditory nerve, brainstem, and cortex have been described in animal models of deafness as well in humans who are deaf. Functional changes in deaf auditory pathways have been evaluated by using a cochlear implant to stimulate the auditory nerve with electrical pulses. Studies of electrically evoked activity in the immature deaf auditory system have demonstrated that auditory brainstem development is arrested and that thalamo-cortical areas are vulnerable to being taken over by other competitive inputs (cross-modal plasticity). Indeed, enhanced peripheral sight and detection of visual movement in congenitally deaf cats and adults have been linked to activity in specific areas of what would normally be auditory cortex. Cochlear implants can stimulate developmental plasticity in the auditory brainstem even after many years of deafness in childhood but changes in the auditory cortex are limited, at least in part, by the degree of reorganization which occurred during the period of deafness. Consequently, we must identify hearing loss rapidly (i.e., at birth for congenital deficits) and provide cochlear implants to appropriate candidates as soon as possible. Doing so has facilitated auditory development in the thalamo-cortex and allowed children who are deaf to perceive and use spoken language.

What is the optimal timing for bilateral cochlear implantation in children

Abstract: Bilateral cochlear implants (CIs) have been provided to children who are deaf in both ears with intent to promote binaural hearing. If it is possible to establish binaural hearing with two CIs, these children would be able to make use of interaural level and timing differences to localize sound and to distinguish between sounds separated in space. These skills are central to the ability to attend to one particular sound amidst a number of sound sources. This may be particularly important for children because they are typically learning and interacting in groups. However, the development of binaural processing could be disrupted by effects of bilateral deafness, effects of unilateral CI use, or issues related to the child's age at onset of deafness and age at the time of the first and second cochlear implantation. This research aims to determine whether binaural auditory processing is affected by these variables in an effort to determine the optimal timing for bilateral cochlear implantation in children. It is now clear that the duration of bilateral deafness should be limited in children to restrict reorganization in the auditory thalamo-cortical pathways. It has also been shown that unilateral CI use can halt such reorganization to some extent and promote auditory development. At the same time, however, unilateral input might compromise the development of binaural processing if CIs are provided sequentially. Mismatches in responses from the auditory brainstem and cortex evoked by the first and second CI after a long period of unilateral CI use suggest asymmetry in the bilateral auditory pathways which is significantly more pronounced than in children receiving bilateral implants simultaneously. Moreover, behavioural responses to level and timing differences between implants suggest that these important binaural cues are not being processed normally by children who received a second CI after a long period of unilateral CI use and at older ages. In sum, there may be multiple sensitive periods in the developing auditory system, which must be considered when determining the optimal timing for bilateral cochlear implantation.

Development and evaluation of the modiolar research array – multi-centre collaborative study in human temporal bones

Abstract: ObjectiveMulti-centre collaborative study to develop and refine the design of a prototype thin perimodiolar cochlear implant electrode array and to assess feasibility for use in human subjects. Study DesignMulti-centre temporal bone insertion studies. Materials and MethodsThe modiolar research array (MRA) is a thin pre-curved electrode that is held straight for initial insertion with an external sheath rather than an internal stylet. Between November 2006 and February 2009, six iterations of electrode design were studied in 21 separate insertion studies in which 140 electrode insertions were performed in 85 human temporal bones by 12 surgeons. These studies aimed at addressing four fundamental questions related to the electrode concept, being: (1) Could a sheath result in additional intra-cochlear trauma? (2) Could a sheath accommodate variations in cochlea size and anatomies? (3) Could a sheath be inserted via the round window? and (4) Could a sheath be safely removed once the electrode had been inserted...

Identifying emotions in music through electrical hearing in deaf children using cochlear implants

Abstract: Objective: Cochlear implant (CI) devices are the choice of treatment for individuals with severe to profound hearing loss. The CI devices provide the opportunity for children who are deaf to perceive sound by electrical stimulation of the auditory nerve, with the goal of optimizing oral communication. A natural benefit of acquiring hearing using CIs is the ability to hear, and perhaps enjoy, music. Music is a non-verbal auditory stimulus and a powerful tool for transmitting emotion. Identifying emotional cues is an important part of normal social development and communication and thus music may play an important role in establishing these skills during development. To date, it is not known whether children who use cochlear implants to hear can identify the emotional content carried in music. Our objective in the present study was to determine whether children who have been deaf from infancy and are experienced CI users have acquired the ability to identify emotion in musical phrases.Method: Study ...

Facial nerve stimulation after cochlear implantation: our experience.

Abstract: Post-implantation facial nerve stimulation is one of the best known and most frequent complications of the cochlear implant procedure. Some conditions, such as otosclerosis and cochlear malformations, as well as high stimulation levels that may be necessary in patients with long auditory deprivation, expose patients to a higher risk of developing post-implant facial nerve stimulation. Facial nerve stimulation can frequently be resolved with minimal changes in speech processor fitting but, in some cases, this can lead to a reduction in the outcome. A retrospective review has been made of the clinical features of 11 patients (out of 119 patients consecutively implanted, from 1999 to 2007, at the ENT Clinic of the University of Pisa) who developed post-implantation facial nerve stimulation.

Electrical stimulation causes rapid changes in electrode impedance of cell-covered electrodes.

Abstract: Animal and clinical observations of a reduction in electrode impedance following electrical stimulation encouraged the development of an in vitro model of the electrode-tissue interface. This model was used previously to show an increase in impedance with cell and protein cover over electrodes. In this paper, the model was used to assess the changes in electrode impedance and cell cover following application of a charge-balanced biphasic current pulse train. Following stimulation, a large and rapid drop in total impedance (Z(t)) and access resistance (R(a)) occurred. The magnitude of this impedance change was dependent on the current amplitude used, with a linear relationship determined between R(a) and the resulting cell cover over the electrodes. The changes in impedance due to stimulation were shown to be transitory, with impedance returning to pre-stimulation levels several hours after cessation of stimulation. A loss of cells over the electrode surface was observed immediately after stimulation, suggesting that the level of stimulation applied was creating localized changes to cell adhesion. Similar changes in electrode impedance were observed for in vivo and in vitro work, thus helping to verify the in vitro model, although the underlying mechanisms may differ. A change in the porosity of the cellular layer was proposed to explain the alterations in electrode impedance in vitro. These in vitro studies provide insight into the possible mechanisms occurring at the electrode-tissue interface in association with electrical stimulation.

Magnetic induction communication system for an implantable medical device

Abstract: A communication system for an active implantable medical device. The communication system includes an isolation transformer a coil coupled to the isolation transformer, and first and second communication components each coupled to the isolation transformer such that the first and second communication components are electrically isolated from the coil, and such that the isolation transformer enables the first and second communication components to communicate, via magnetic induction (MI) using the coil, with at least one external component.

Fitting an auditory prosthesis

Abstract: A method and system for fitting and adjusting the operation of an acoustic hearing prosthesis or a hybrid electric and acoustic hearing prosthesis. A graphic user interface allows for the acoustic and electric fitting parameters to be viewed and adjusted in a comparable way. The method further allows for the parameters for acoustic stimulation of the acoustic channels to be adjusted in response to behavioural or objective measurement of responses to known stimuli, so as to achieve a desired response curve.

Effect of Surgical Technique on Electrode Impedance after Cochlear Implantation

Abstract: OBJECTIVES We compare the evolution of electrode impedance values (IVs) following either conventional cochlear implantation or implantation by the soft surgery (SS) technique. METHODS We performed a retrospective chart review of 20 consecutive adult patients who underwent implantation with the Nucleus CA 24 device between 2004 and 2007. Five patients with preoperative residual hearing at the frequencies 256, 512, and 1,024 Hz underwent implantation by an SS cochlear implantation technique (SS group), and the 15 other patients underwent a conventional implantation technique (conventional cochleostomy [CC] group). The active electrodes were classified as distal (17 to 22), middle (10 to 16), or proximal (3 to 9) according to their position in relation to the tip of the electrode array. Their IVs were collected at 1, 3, 12, 24, and 36 months after implantation. Changes in auditory thresholds at 3 and 24 months were reported for patients in the SS group. RESULTS The postoperative IVs of both the CC and SS groups decreased significantly between 1 and 3 months after implantation (p < 0.05) and then remained stable. The IVs after 12 months were significantly lower (p < 0.05) in the SS group than in the CC group. CONCLUSIONS Patients who underwent the SS technique displayed lower long-term electrode IVs than did their counterparts in the CC group. If electrode IVs are indeed an indirect representation of cochlear fibrosis, the use of the SS technique in lieu of the CC technique could reduce fibrotic development.

Perception of Suprasegmental Speech Features via Bimodal Stimulation: Cochlear Implant on One Ear and Hearing Aid on the Other

Abstract: Purpose The purpose of the study was to evaluate the contribution of acoustic hearing to the perception of suprasegmental features by adults who use a cochlear implant (CI) and a hearing aid (HA) in opposite ears. Method 23 adults participated in this study. Perception of suprasegmental features—intonation, syllable stress, and word emphasis—was assessed. All tests were administered in 2 conditions: CI alone and CI + HA (bimodal). Results Scores were significantly higher in the bimodal condition in comparison to scores in CI alone for all 3 tests. In both conditions, there was great variability among the individual participants. Significant negative correlations emerged between perception of suprasegmental features and the unaided pure-tone average of the contralateral ear to the CI. Conclusions This study found a significant bimodal advantage for perception of all suprasegmental features, most probably due to the better low-frequency acoustic hearing that is provided by the HA. Outcomes suggest that in c...

High-Efficiency Transmission for Medical Implants

Abstract: In this article, by means of appropriate circuit design the total efficiency can be optimized. On a circuit level, a high efficiency for an inductive power link can be obtained by using a class E amplifier and an active power regulator. The class E amplifier has three advantages: it has a high efficiency, it has a minimal power consumption when the secondary coil of the inductive link is shorted, and it reaches its normal operation almost immediately after turn on (although a high-Q LC circuit is involved). These properties are exploited in the design of two different power regulators, which are simple on-off control systems. The power regulators have never been realized, but the Micro-Cap simulations are really very promising. The author is hopeful that these considerations may inspire young designers to optimize inductive powering systems. Recent papers in reference [6], [7] show that modeling and designing an inductive power link with a high efficiency is still a challenge.

A comparison of the strength of autohesion of plasma treated amorphous and semi-crystalline PEEK films

Abstract: Polyether ether ketone (PEEK) is a promising material for the encapsulation of electronic components for medical implants but a strong and hermetic joining technology is required. Autohesion is a self-bonding method that avoids the need for adhesives. The strengths of autohesive joins using amorphous and semi-crystalline PEEK films after surface activation using RF plasma were compared. Both types of PEEK films showed successful autohesion after activation with the bond strength of the amorphous sample being twice as high as the bond strength of the semi-crystalline sample. Plasma treatment increased the autohesion strength of PEEK with no observed change in surface roughness (as measured by profilometer). The water contact angle was reduced by the treatment. X-ray photoelectron spectroscopy (XPS) was carried out to determine surface chemistry. In the case of the semi-crystalline surface, plasma treatment increased the relative percentage of CO functional groups compared to the untreated surface. For treated surfaces nitrogen concentration correlated positively with bond strength while oxygen concentration correlated negatively with the semi-crystalline PEEK samples and positively with the amorphous PEEK samples. The oxygen groups most likely are formed after the treatment by ambient oxidation are not conducive to bond formation, possibly because of the quenching of radicals that would otherwise form links. Copyright © 2010 John Wiley & Sons, Ltd.

Clinical evaluation of cochlear implant sound coding taking into account conjectural masking functions, MP3000™

Abstract: Efficacy of the SPEAK and ACE coding strategies was compared with that of a new strategy, MP3000™, by 37 European implant centers including 221 subjects. The SPEAK and ACE strategies are based on selection of 8-10 spectral components with the highest levels, while MP3000 is based on the selection of only 4-6 components, with the highest levels relative to an estimate of the spread of masking. The pulse rate per component was fixed. No significant difference was found for the speech scores and for coding preference between the SPEAK/ACE and MP3000 strategies. Battery life was 24% longer for the MP3000 strategy. With MP3000 the best results were found for a selection of six components. In addition, the best results were found for a masking function with a low-frequency slope of 50 dB/Bark and a high-frequency slope of 37 dB/Bark (50/37) as compared to the other combinations examined of 40/30 and 20/15 dB/Bark. The best results found for the steepest slopes do not seem to agree with current estimates of the spread of masking in electrical stimulation. Future research might reveal if performance with respect to SPEAK/ACE can be enhanced by increasing the number of channels in MP3000 beyond 4-6 and it should shed more light on the optimum steepness of the slopes of the masking functions applied in MP3000.

Disruption of ephrin B/Eph B interaction results in abnormal cochlear innervation patterns†‡

Abstract: Objective: To determine the expression patterns of B ephrins and Ephs in the cochlea and identify functional consequences of disruption of ephrin B/Eph B interactions in both cultured spiral ganglion neurons and in the cochlea of live animals. Study Design: The expression patterns of various B ephrins and Ephs were determined in mice with Lac-Z mutation. Mice with null function of individual B ephrin and Eph proteins and those with multiple knockouts were studied for cochlear innervation patterns. Methods: Mice with B ephrins and Ephs disrupted with the β-galactosidase gene were sacrificed at P6, and their cochleae isolated and processed for Lac-Z staining to determine expression of these proteins in cochlear tissue. Spiral ganglion cells from wild-type as well as ephrin B1 knockout mice were isolated and cocultured with Eph B2 expressing Cos1 cells and neurite lengths were determined. Fluorescent lipophillic dyes were used to label spiral ganglion cell nerve fibers to determine cochlear innervation patterns in wild-type and knockout mice. Results: Eph B1, B2, and ephrin B2 but not B3 was expressed in the cochlea. Eph B2 inhibited outgrowth of spiral ganglion cell axons from wild-type mice, but not from ephrin B1 knockout mice in culture. Knockout mice with null function of ephrin B1 alone or Eph B1, Eph B2, Eph B3 in combination demonstrated abnormal innervation patterns in the organ of Corti. Conclusions: Disruption of B ephrins and Ephs results in functional consequences in spiral ganglion cells, suggesting that these proteins play a role in establishing normal innervation patterns in the cochlea.

Telephone use and the factors influencing it among cochlear implant patients

Abstract: ObjectiveTo investigate telephone use in cochlear implant patients and to determine factors most likely to influence telephone use.MethodsSurveys were mailed to 504 cochlear implant patients treated at Sunnybrook Health Sciences Hospital.ResultsTwo hundred four patients returned surveys (49%), 87% were classified as telephone users. No differences were found in age, pre-implant hearing characteristics, and the majority of post-implant behaviors. Education and post-implant sound perception scores were found to be significantly different (P < 0.05) between telephone users and non-users.DiscussionTelephone use among cochlear implant patients shows a positive increase compared to previous studies. In addition, we find that higher attained education and post-implant hearing scores to be independently correlated to telephone use.

Extracochlear electrode extrusion

Abstract: Extracochlear electrode extrusion is a potentially under-recognized complication of cochlear implantation As the age of implantation becomes younger, electrode extrusion is of concern due to future skull growth Extrusion of several electrodes may compromise performance and thus require surgical reinsertion of the electrodes Almost 60% of patients with electrode extrusion have required revision surgery This paper presents a case report and literature review which discusses factors which contribute to electrode extrusion and emphasizes the need for a high degree of suspicion in certain situations Surgical steps such as electrode fixation techniques are highlighted in order to attempt to reduce the occurrence of this complication

User control for hearing prostheses

Abstract: A method of operating a hearing prosthesis. The hearing prosthesis includes memory and a clock and is configured to deliver stimuli to a user. The method includes determining the stimuli, with the hearing prosthesis, in response to a sound signal and at least in part by using one or more adjustable parameters stored in the memory. The method further includes receiving, from the user, a request to adjust at least one of the parameters, and determining whether to make the requested adjustment by reference to an amount of time, as determined by said clock, or a function based around an amount of time since a predefined event.

Hearing Prosthesis with Integrated Sensors for Measuring Pressure in a Cochlea

Abstract: The present application discloses a hearing prosthesis comprising a stimulation assembly configured to be implanted into a cochlea. The stimulation assembly comprises a plurality of electrodes and one or more sensors. The one or more sensors may be configured to measure pressure within the cochlea. The pressure measurements may include (i) measurements of pressure corresponding to a physical contact of the one or more sensors with internal cochlear structures, (ii) measurements of perilymph fluid pressure, or (iii) measurements of pressure waves in the perilymph fluid corresponding to external sound waves. In one aspect, the sensor may be used by a system to help surgeons avoid damage to the cochlea during surgical implantation of the stimulation assembly. In another aspect, the sensor may be one component of an implantable microphone.

Preliminary results and technique for electrophysiological intra-operative monitoring of residual hearing during cochlear implantation

Abstract: AimsTo assess the feasibility of intra-operative monitoring of residual hearing using electrocochleography (ECOG) during cochlear implantation. We present our methods and preliminary results. MethodsWe attempted to monitor 21 consecutive paediatric and adult subjects during cochlear implantation. All subjects were implanted via a promontory cochleostomy with full electrode insertions of CochlearTM Nucleus® (Cochlear Nucleus, Cochlear Ltd, Australia) devices: 8 with straight electrodes and 13 with contoured electrodes. Baseline recordings were made after the completion of the posterior tympanotomy, and subsequently at stages of the cochleostomy and electrode insertion. ResultsWe were unable to obtain recordings on five patients because the ear-insert tubing kinked, which disrupted transmission of the stimulus. Five had insufficient cochlear function to be able to record a baseline ECOG. No subjects in whom we were able to obtain a satisfactory baseline ECOG (n = 11) had a reduction in ECOG action potential...

Intra-individual assessment of speech and music perception in cochlear implant users with contralateral Cochlear™ and MED-EL™ systems.

Abstract: Conclusion: Whilst objective testing on music perception showed no individual differences between cochlear implant (CI) devices, subjective music perception was found to be superior with the MED-EL device in the majority of cases evaluated. Objective: To compare speech and music perception through two different CI systems in the same individuals. Methods: Six post-lingually deaf patients, who had been implanted with a Cochlear™ Nucleus® device in one ear and a MED-EL SONATATI100 on the contralateral side were evaluated. One subject was excluded from group analysis because of significant differences in performance between ears. Subjects completed a questionnaire designed to assess implant users' listening habits. Subjective assessments of each subject were made for comparison of speech and music perception with each system and preferences of system. The subjects consecutively used each system with the contralateral device turned off, and were objectively assessed for specific musical skills. Speec...

Sound processing with increased noise suppression

Abstract: A method for processing sound that includes, generating one or more noise component estimates relating to an electrical representation of the sound and generating an associated confidence measure for the one or more noise component estimates. The method further comprises processing, based on the confidence measure, the sound.

Challenges and recent developments in sound processing for Baha

Abstract: Osseointegrated auditory implants such as Baha(®) provide an efficient pathway for sound delivery and an excellent amplification choice for patients with conductive or mixed hearing loss or single-sided sensorineural deafness. But at the same time, bone conduction hearing provides a number of key challenges that need to be addressed. One solution is computer-based fitting software to measure in-situ thresholds directly through the Baha sound processor and to individually prescribe amplification settings based on the patient's hearing loss and degree of transcranial attenuation. Additionally, technologies such as automatic directional microphones and noise reduction systems further improve hearing performance in noisy situations. This paper highlights recent technological innovations and summarizes data on the advantages for the Baha patient population using the sound processing capabilities available in the latest Baha sound processors.

Consonant Perception by Adults with Bimodal Fitting

Abstract: Many adults who receive a cochlear implant in one ear have usable residual hearing in the opposite ear. The simultaneous use of a cochlear implant (CI) and a hearing aid (HA) in the contralateral ear, or bimodal fitting, provides the recipient with potentially complementary information to the auditory system for speech perception, localization, and functional benefits in everyday life via two different modes of stimulation (acoustic and electric). This study investigated consonant perception in listeners who use bimodal fitting with the aim to identify the acoustic cues responsible for speech understanding when an HA is used together with a CI in comparison with the use of a CI alone. The results showed that on average, there was significant improvement in consonant recognition in quiet and in noise when adults wore CIs with HAs compared with CIs alone. Feature analysis of consonants was performed to directly examine what additional cues were provided by the HA to enhance consonant perception. This analysis showed that on average, there was a significant increase in reception of information about voicing in quiet conditions and about voicing and manner of articulation in noise. There was no difference in the transmission of information about place of articulation. The implications of these findings on rehabilitation of adults with unilateral CI are discussed.