A Method for Removing Cochlear Implant Artifact

When cortical auditory evoked potentials (CAEPs) are recorded in individuals with a cochlear implant (CI), electrical artifact can make the CAEP difficult or impossible to measure. Since increasing the interstimulus interval (ISI) increases the amplitude of physiological responses without changing the artifact, subtracting CAEPs recorded with a short ISI from those recorded with a longer ISI should show the physiological response without any artifact. In the first experiment, N1-P2 responses were recorded using a speech syllable and tone, paired with ISIs that changed randomly between 0.5 and 4 seconds. In the second experiment, the same stimuli, at ISIs of either 500 or 3000 ms, were presented in blocks that were homogeneous or random with respect to the ISI or stimulus. In the third experiment, N1-P2 responses were recorded using pulse trains with 500 and 3000 ms ISIs in 4 CI listeners. The results demonstrated: 1) N1-P2 response amplitudes generally increased with increasing ISI. 2) Difference waveforms were largest for the homogeneous and random-stimulus blocks than for the random-ISI block. 3) The subtraction technique almost completely eliminated the electrical artifact in individuals with cochlear implants. Therefore, the subtraction technique is a feasible method of removing from the N1-P2 response the electrical artifact generated by the cochlear implant.

from Hearing Research

A Method for Removing Cochlear Implant Artifact

When cortical auditory evoked potentials (CAEPs) are recorded in individuals with a cochlear implant (CI), electrical artifact can make the CAEP difficult or impossible to measure. Since increasing the interstimulus interval (ISI) increases the amplitude of physiological responses without changing the artifact, subtracting CAEPs recorded with a short ISI from those recorded with a longer ISI should show the physiological response without any artifact. In the first experiment, N1-P2 responses were recorded using a speech syllable and tone, paired with ISIs that changed randomly between 0.5 and 4 seconds. In the second experiment, the same stimuli, at ISIs of either 500 or 3000 ms, were presented in blocks that were homogeneous or random with respect to the ISI or stimulus. In the third experiment, N1-P2 responses were recorded using pulse trains with 500 and 3000 ms ISIs in 4 CI listeners. The results demonstrated: 1) N1-P2 response amplitudes generally increased with increasing ISI. 2) Difference waveforms were largest for the homogeneous and random-stimulus blocks than for the random-ISI block. 3) The subtraction technique almost completely eliminated the electrical artifact in individuals with cochlear implants. Therefore, the subtraction technique is a feasible method of removing from the N1-P2 response the electrical artifact generated by the cochlear implant.

from Hearing Research

Recording of electrically evoked auditory brainstem responses after electrical stimulation with biphasic, triphasic and precision triphasic pulses

Biphasic electrical pulses are the standard stimulation pulses in current cochlear implants. In auditory brainstem recordings biphasic pulses generate a significant artifact that disrupts brainstem responses, which are magnitudes smaller. Triphasic pulses may minimize artifacts by restoring the neural membrane to its resting potential faster than biphasic pulses and make auditory brainstem responses detection easier. We compared biphasic pulses with triphasic and precision triphasic pulses to evoke brainstem responses in human subjects. For this purpose, electrically evoked brainstem response audiometry was performed in 10 (11 ears) cochlear implant patients. Artifacts and brainstem responses evoked by bi- and triphasic stimulation were analyzed. Artifact amplitude and decay time were related to pulse pattern shape, but application of averaging and alternation reduced the deterioration of electrically evoked brainstem responses independent of pulse pattern shape. Contrary to our expectations, biphasic pulses showed a higher detectability in comparison to triphasic pulse stimulation at the same stimulation amplitude.

from the Journal of Voice

Recording of electrically evoked auditory brainstem responses after electrical stimulation with biphasic, triphasic and precision triphasic pulses

Biphasic electrical pulses are the standard stimulation pulses in current cochlear implants. In auditory brainstem recordings biphasic pulses generate a significant artifact that disrupts brainstem responses, which are magnitudes smaller. Triphasic pulses may minimize artifacts by restoring the neural membrane to its resting potential faster than biphasic pulses and make auditory brainstem responses detection easier. We compared biphasic pulses with triphasic and precision triphasic pulses to evoke brainstem responses in human subjects. For this purpose, electrically evoked brainstem response audiometry was performed in 10 (11 ears) cochlear implant patients. Artifacts and brainstem responses evoked by bi- and triphasic stimulation were analyzed. Artifact amplitude and decay time were related to pulse pattern shape, but application of averaging and alternation reduced the deterioration of electrically evoked brainstem responses independent of pulse pattern shape. Contrary to our expectations, biphasic pulses showed a higher detectability in comparison to triphasic pulse stimulation at the same stimulation amplitude.

from Hearing Research

Validation of the LittlEARS® Auditory Questionnaire in children with normal hearing

Objectives
With more children receiving cochlear implants during infancy, there is a need for validated assessments of pre-verbal and early verbal auditory skills. The LittlEARS® Auditory Questionnaire is presented here as the first module of the LittlEARS® test battery. The LittlEARS® Auditory Questionnaire was developed and piloted to assess the auditory behaviour of normal hearing children and hearing impaired children who receive a cochlear implant or hearing aid prior to 24 months of age. This paper presents results from two studies: one validating the LittlEARS® Auditory Questionnaire on children with normal hearing who are German speaking and a second validating the norm curves found after adaptation and administration of the questionnaire to children with normal hearing in 15 different languages.

Methods
Scores from a group of 218 German and Austrian children with normal hearing between 5 days and 24 months of age were used to create a norm curve. The questionnaire was adapted from the German original into English and then 15 other languages to date. Regression curves were found based on parental responses from 3309 normal hearing infants and toddlers. Curves for each language were compared to the original German validation curve.

Results
The results of the first study were a norm curve which reflects the age-dependence of auditory behaviour, reliability and homogeneity as a measure of auditory behaviour, and calculations of expected and critical values as a function of age. Results of the second study show that the regression curves found for all the adapted languages are essentially equal to the German norm curve, as no statistically significant differences were found.

Conclusions
The LittlEARS® Auditory Questionnaire is a valid, language-independent tool for assessing the early auditory behaviour of infants and toddlers with normal hearing. The results of this study suggest that the LittlEARS® Auditory Questionnaire could also be very useful for documenting children’s progress with their current amplification, providing evidence of the need for implantation, or highlighting the need for follow-up in other developmental areas.

from the International Journal of Pediatric Otorhinolaryngology

Neural response telemetry in patients with the double-array cochlear implant

Abstract This study aimed to evaluate the neural response in double-array cochlear implant as well as to describe the refractory recovery and the spread of excitation functions. In a prospective study 11 patients were implanted with the double-array cochlear implant. Neural response telemetry (NRT) was performed intra-operatively. NRT threshold could be registered in 6 of the 11 patients, at least in one electrode. The remaining five patients did not show measurable neural response intra-operatively. It was noted that although recovery and spread of excitation functions could be recorded in all the tested electrodes with measurable neural responses, the responses were shown to be different from the usual register in patients with other etiologies.

from the European Archives of Oto-Rhino-Laryngologyl

Primary and multisensory cortical activity is correlated with audiovisual percepts

Incongruent auditory and visual stimuli can elicit audiovisual illusions such as the McGurk effect where visual /ka/ and auditory /pa/ fuse into another percept such as/ta/. In the present study, human brain activity was measured with adaptation functional magnetic resonance imaging to investigate which brain areas support such audiovisual illusions. Subjects viewed trains of four movies beginning with three congruent /pa/ stimuli to induce adaptation. The fourth stimulus could be (i) another congruent /pa/, (ii) a congruent /ka/, (iii) an incongruent stimulus that evokes the McGurk effect in susceptible individuals (lips /ka/ voice /pa/), or (iv) the converse combination that does not cause the McGurk effect (lips /pa/ voice/ ka/). This paradigm was predicted to show increased release from adaptation (i.e. stronger brain activation) when the fourth movie and the related percept was increasingly different from the three previous movies. A stimulus change in either the auditory or the visual stimulus from /pa/ to /ka/ (iii, iv) produced within-modality and cross-modal responses in primary auditory and visual areas. A greater release from adaptation was observed for incongruent non-McGurk (iv) compared to incongruent McGurk (iii) trials. A network including the primary auditory and visual cortices, nonprimary auditory cortex, and several multisensory areas (superior temporal sulcus, intraparietal sulcus, insula, and pre-central cortex) showed a correlation between perceiving the McGurk effect and the fMRI signal, suggesting that these areas support the audiovisual illusion. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc.

from Human Brain Mapping

Auditory Midbrain Implant: A Review

The auditory midbrain implant (AMI) is a new hearing prosthesis designed for stimulation of the inferior colliculus in deaf patients who cannot sufficiently benefit from cochlear implants. The authors have begun clinical trials in which five patients have been implanted with a single shank AMI array (20 electrodes). The goal of this review is to summarize the development and research that has led to the translation of the AMI from a concept into the first patients. This study presents the rationale and design concept for the AMI as well a summary of the animal safety and feasibility studies that were required for clinical approval. The authors also present the initial surgical, psychophysical, and speech results from the first three implanted patients. Overall, the results have been encouraging in terms of the safety and functionality of the implant. All patients obtain improvements in hearing capabilities on a daily basis. However, performance varies dramatically across patients depending on the implant location within the midbrain with the best performer still not able to achieve open set speech perception without lip-reading cues. Stimulation of the auditory midbrain provides a wide range of level, spectral, and temporal cues, all of which are important for speech understanding, but they do not appear to sufficiently fuse together to enable open set speech perception with the currently used stimulation strategies. Finally, several issues and hypotheses for why current patients obtain limited speech perception along with several feasible solutions for improving AMI implementation are presented.

from Trends in Amplification

High Prevalence of the Connexin 26 (GJB2) Mutation in Chinese Cochlear Implant Recipients

Background: The GJB2 gene, mapping to chromosome 13q12, encodes a gap junction protein, connexin 26, and is responsible for certain forms of congenital deafness, such as DFNB1 and DFNA3. Mutations of this gene are responsible for about one half of severe autosomal recessive non-syndromic deafness. Methods: To determine whether GJB2 mutations are major causes of deafness in Chinese cochlear implant recipients, we enrolled 115 cochlear implant recipients for mutation screening. Results: The results showed that 36.5% (42/115) of all cochlear implant recipients and 41% (41/100) of non-syndromic deafness patients exhibit GJB2 mutations; only 1 inner ear malformation patient was detected with GJB2 mutations. The present study found 11 different variations in the GJB2 gene. Conclusion: The 235delC mutation was the most prevalent mutation, found in 18.3% (42/230 alleles) of all cochlear implant recipients and 21.0% (42/200 alleles) of the non-syndromic deafness group. Only 0.6% of GJB2 mutations were detected in the inner ear malformation group. The novel 187GT mutations are likely to be pathological mutations.

from ORL -Journal for Oto-Rhino-Laryngology and Its Related Specialties

High Prevalence of the Connexin 26 (GJB2) Mutation in Chinese Cochlear Implant Recipients

Background: The GJB2 gene, mapping to chromosome 13q12, encodes a gap junction protein, connexin 26, and is responsible for certain forms of congenital deafness, such as DFNB1 and DFNA3. Mutations of this gene are responsible for about one half of severe autosomal recessive non-syndromic deafness. Methods: To determine whether GJB2 mutations are major causes of deafness in Chinese cochlear implant recipients, we enrolled 115 cochlear implant recipients for mutation screening. Results: The results showed that 36.5% (42/115) of all cochlear implant recipients and 41% (41/100) of non-syndromic deafness patients exhibit GJB2 mutations; only 1 inner ear malformation patient was detected with GJB2 mutations. The present study found 11 different variations in the GJB2 gene. Conclusion: The 235delC mutation was the most prevalent mutation, found in 18.3% (42/230 alleles) of all cochlear implant recipients and 21.0% (42/200 alleles) of the non-syndromic deafness group. Only 0.6% of GJB2 mutations were detected in the inner ear malformation group. The novel 187GT mutations are likely to be pathological mutations.

from ORL -Journal for Oto-Rhino-Laryngology and Its Related Specialties

Effects of neonatal partial deafness and chronic intracochlear electrical stimulation on auditory and electrical response characteristics in primary auditory cortex

The use of cochlear implants in patients with severe hearing losses but residual low-frequency hearing raises questions concerning the effects of chronic intracochlear electrical stimulation (ICES) on cortical responses to auditory and electrical stimuli. We investigated these questions by studying responses to tonal and electrical stimuli in primary auditory cortex (AI) of two groups of neonatally-deafened cats with residual high-threshold, low-frequency hearing. One group were implanted with a multi-channel intracochlear electrode at eight weeks of age, and received chronic ICES for up to nine months before cortical recording. Cats in the other group were implanted immediately prior to cortical recording as adults. In all cats in both groups, multi-neuron responses throughout the rostro-caudal extent of AI had low characteristic frequencies (CFs), in the frequency range of the residual hearing, and high-thresholds. Threshold and minimum latency at CF did not differ between the groups, but in the chronic ICES animals there was a higher proportion of electrically but not acoustically excited recording sites. Electrical response thresholds were higher and latencies shorter in the chronically stimulated animals. Thus, chronic implantation and ICES affected the extent of AI that could be activated by acoustic stimuli and resulted in changes in electrical response characteristics.

from Hearing Research

Estimation of risks associated with paediatric cochlear implantation

Abstract
The objectives of this study were to estimate the rates of complications associated with paediatric cochlear implantation use: a) at one Canadian cochlear implant (CI) centre, and b) in the published literature. It comprised a retrospective hospital-based chart review and a concurrent review of complications in the published literature. There were 224 children who had undergone surgery from 1994 to June 2007. Results indicate that the rates of complications at the local Canadian paediatric CI centre are not significantly different from the literature rates for all examined complication types. This hospital-based retrospective chart review and review of the literature provide readers with an estimation of the risks to aid in evidence-based decision-making surrounding paediatric cochlear implantation. Copyright © 2009 John Wiley & Sons, Ltd.

from Cochlear Implants International

Spontaneous increases in impedance following cochlear implantation: Suspected causes and management

Modern cochlear implant systems deliver impulse transmission rates up to 50 000 pps. It emerged that the fast stimulation rates led to enhanced speech comprehension. Impedance measurement is an important aspect in cochlear implant testing procedures. Impedance values are a measure of the electrical resistance between the individual implant electrodes. Increased impedances were attributed frequently to inflammatory/tissue-related processes. In recent years, however, we have repeatedly found cases of impedance increase for which the inflammatory model did not provide a satisfactory explanation. The aim of this study is to evaluate increases in impedance in our cochlear implant population, to attempt to find their cause, and to formulate therapeutic hypotheses. In our cochlear implant programme (> 3000 recipients) we screened our database for impedance increases over time during device fitting. We found 16 patients with 18 affected ears in whom impedance increases were clearly demonstrated. We found that especially in cases without any sign of prior inflammation, increasing the pulse width of the stimulation strategy seems to be an effective tool to return increased impedances to normal levels.

from the International Journal of Audiology

Development of Mandarin monosyllabic speech test materials in China

In this study, monosyllabic Mandarin speech test materials (MSTMs) were developed for use in word recognition tests for speech audiometry in Chinese audiology clinics. Mandarin monosyllabic materials with high familiarity were designed with regard to phonological balance and recorded digitally with a male voice. Inter-list equivalence of difficulty was evaluated for a group of 60 subjects (aged 18-25 years) with normal hearing. Seven lists with 50 words each were found to be equivalent. These seven equivalent lists were used to measure performance-intensity (PI) functions for a group of 32 subjects with normal hearing and a group of 40 subjects with mild to moderate sensorineural hearing loss. The mean slope of PI function was found to be 4.1%/dB and 2.7%/dB, respectively. The seven lists of Mandarin monosyllabic materials were found to have sufficient reliability and validity to be used in clinical situations.

from the International Journal of Audiology

Speech and language outcomes in children with auditory neuropathy/dys-synchrony managed with either cochlear implants or hearing aids

The aim of this study was to assess the receptive language and speech production abilities of a group of school-aged children with auditory neuropathy/dys-synchrony-type hearing loss. Ten children who had received a cochlear implant in one or both ears participated. Findings for this group were compared with those for a matched cohort of implanted children with other forms of sensorineural hearing loss and with those for a group of auditory neuropathy/dys-synchrony children who were long-term hearing aid users.

Results for 9 of the ten implanted children with auditory neuropathy/dys-synchrony were similar to those of the general population of paediatric implant recipients. (One child, who gained little perceptual benefit from his device, showed severely delayed spoken language development). Results for the group of aided auditory neuropathy/dys-synchrony subjects were comparable to those for their implanted counterparts suggesting that affected children should not automatically be considered cochlear implant candidates.

from the International Journal of Audiology