J. Frijns

ABSTRACT Electrode array, an important component of Cochlear Implant (CI) design holds a key position in restoring the hearing process to the deaf patients. It represents a direct interface between the auditory nerve (biological tissue) and the electronic system of the CI. Electrode arrays are available in different design, material, shape and size depending upon the requirement and the application of the device. The traditional fabrication method of the device restricts the electrode usability and its performance. In this paper we investigate and explore capable materials for CI electrode array fabrication used for stimulating the auditory neurons. Here we discuss the CMOS compatible electrode material and the necessary biocompatible insulation required for long term implants. Fabrication issues and different material possibilities are discussed with respect to the properties associated with it.

Background Hearing depends on correct functioning of the cochlear hair cells, and their innervation by spiral ganglion neurons. Most of the insight into the embryological and molecular development of this sensory system has been derived from animal studies. In contrast, little is known about the molecular expression patterns and dynamics of signaling molecules during normal fetal development of the human cochlea. In this study, we investigated the onset of hair cell differentiation and innervation in the human fetal cochlea at various stages of development. Results At 10 weeks of gestation, we observed a prosensory domain expressing SOX2 and SOX9/SOX10 within the cochlear duct epithelium. In this domain, hair cell differentiation was consistently present from 12 weeks, coinciding with downregulation of SOX9/SOX10, to be followed several weeks later by downregulation of SOX2. Outgrowing neurites from spiral ganglion neurons were found penetrating into the cochlear duct epithelium pri...

This study examined the quantity and quality of parental linguistic input to toddlers with moderate hearing loss (MHL) compared with toddlers with normal hearing (NH). The linguistic input to eighteen toddlers with MHL and twenty-four toddlers with NH was examined during a 10-minute free-play activity in their home environment. Results showed that toddlers with MHL were exposed to an equivalent amount of parental linguistic input compared to toddlers with NH. However, parents of toddlers with MHL used less high-level facilitative language techniques, used less mental state language, and used shorter utterances than parents of toddlers with NH. Quantity and quality measures of parental linguistic input were positively related to the expressive language abilities of toddlers with MHL.

Several multipolar current focussing strategies are examined in a computational model of the implanted human cochlea. The model includes a realistic spatial distribution of cell bodies of the auditory neurons throughout Rosenthal's canal. Simulations are performed of monopolar, (partial) tripolar and phased array stimulation. Excitation patterns, estimated thresholds, electrical dynamic range, excitation density and neural recruitment curves are determined and compared. The main findings are: (I) Current focussing requires electrical field interaction to induce spatially restricted excitation patterns. For perimodiolar electrodes the distance to the neurons is too small to have sufficient electrical field interaction, which results in neural excitation near non-centre contacts. (II) Current focussing only produces spatially restricted excitation patterns when there is little or no excitation occurring in the peripheral processes, either because of geometrical factors or due to n...

Pediatric hearing impairment is a chronic handicap that can potentially lead to the development of psychopathology. Yet, for hearing-impaired children and adolescents, the exact occurrence of various forms of psychopathology and its causes are unclear, while this knowledge is essential to enable targeted screenings and interventions. To investigate the level of psychopathological symptoms in hearing-impaired children and adolescents as compared with normally hearing peers. Second, the influence of type of hearing device and possible risk and protective factors on psychopathology were examined. A systematic literature search was performed covering relevant databases, including PubMed, Embase, and Web of Science. Two independent researchers identified the relevant articles. The final search was performed on May 2, 2013, and resulted in a total of 35 articles. Literature consistently demonstrated that hearing-impaired children and adolescents were more prone to developing depression, a...

Emotional functioning plays a crucial role in the social development of children and adolescents. We examined the extent to which emotion control was related to the quality of friendships in pre-adolescents with and without hearing loss. We tested 350 pre-adolescents (75 deaf/hard of hearing in mainstream education (DHHm), 48 deaf/hard of hearing in special education (DHHs), and 227 hearing) through self-report. Outcomes confirmed a positive association between emotion control and positive friendships for all groups, with one notable exception: more approach strategies for emotion regulation were associated with more negative friendship features in the DHHs group. In addition, the DHHm group demonstrated high levels of emotion control, while their levels of positive friendship features were still lower compared to the hearing group.

To answer the dilemma clinician's face when deciding between cochlear implant (CI) and auditory brainstem implant (ABI) treatment options in patients with cochlear nerve deficiency (CND). Case study supplemented with literature review and meta-analysis. Tertiary referral center. Child with CHARGE syndrome and congenital deafness. ABI as there was no benefit after bilateral cochlear implantation. Speech and language development, quality of life. In one ear the cochleovestibular nerve was present on magnetic resonance imaging (MRI) without preoperative ABR responses. In the contra lateral ear the nerve could not be identified, despite present ABR responses. Nevertheless, there was no positive outcome with CI. The patient had improved speech and language and quality of life with ABI. Of the 108 patients with CND and CI identified in the literature review, 25% attained open-set speech perception, 34% attained closed-set speech perception, and 41% detected sounds or less. The appeara...

ABSTRACT Titanium nitride (TiN) is a proven bio-compatible conductor and as such increasingly applied as an microelectrode material in novel biomedical devices. This paper reports the functioning of BiCMOS devices with titanium nitride as a gate electrode and interconnect material all fabricated in five photolithographic steps. This simple BiCMOS process allows the on-chip integration of a biomedical electrode arrays with electronics to reduce the electrode wiring density and hence reduce the electrodes footprint. This approach can be useful for medical devices like cochlear implants (CI's) where a high density electrode array is applied in a small volume.

The objective of this study was to evaluate the effect of bilateral versus unilateral cochlear implants and the importance of the inter-implant interval. Seventy-three prelingually deaf children received sequential bilateral cochlear implants. Speech recognition in quiet with the first, second and with both implants simultaneously was evaluated at the time of the second implantation and after 12 and 24 months. Mean bilateral speech recognition 12 and 24 months after the second implantation was significantly higher than that obtained with either the first or the second implant. The addition of a second implant was demonstrated to have a beneficial effect after both 12 and 24 months. Speech recognition with the second implant increased significantly during the first year. A small, non-significant improvement was observed during the second year. The inter-implant interval significantly influenced speech recognition with the second cochlear implant both at 12 and 24 months, and bilateral speech recognition at 12 months, but not at 24 months. A small, but statistically significant improvement in speech recognition was found with bilateral cochlear implants compared with a unilateral implant. A major increase in speech recognition occurred with the second cochlear implant during the first year. A shorter time interval between the two implantations resulted in better speech recognition with the second implant. However, no definitive time-point was found for when the second implant could no longer add a positive effect.

The increased likelihood of facial nerve stimulation (FNS) with cochlear implantation in advanced cochlear otosclerosis is due to a lowering of the facial nerve excitation threshold with increasing bone demineralization. Facial nerve stimulation can complicate cochlear implant fitting, often necessitating the deactivation of certain electrode contacts. High-resolution computed tomographic scans were used to estimate anatomic features of the cochlea and the facial nerve canal. These features were added to a detailed computational model of the implanted human cochlea to examine the consequences of increased conductivity of the bone of the otic capsule. The model took into account the electrode contact type (banded or otherwise) and position (perimodiolar or lateral wall) of the electrode array. Contrary to the hypothesis, facial nerve thresholds were found to be slightly elevated with increased conductivity of the surrounding bone. However, the threshold and most comfortable loudness levels of the auditory nerve increase more rapidly owing to the reduced current density in the scala tympani as current leaks more easily out of the cochlea. Lateral wall electrodes were predicted to result in an increased likelihood of FNS. A progressively reduced probability of FNS was indicated for the full-band, half-band, and plated electrode arrays, respectively. The clinical observation of increased FNS in cases of cochlear otosclerosis has been demonstrated in a computational model. Rather than decreased FN threshold, it is the increased levels for cochlear stimulation that is the main factor. Particularly, perimodiolar designs with more shielding against lateral spread of current could reduce the likelihood of FNS.

To investigate the preservation of residual hearing in subjects who received the Nucleus Hybrid L24 cochlear implant. To investigate the performance benefits up to one year post-implantation in terms of speech recognition, sound quality, and quality of life. Prospective, with sequential enrolment and within-subject comparisons. Post-operative performance using a Freedom Hybrid sound processor was compared with that of pre-operative hearing aids. Sixty-six adult hearing-impaired subjects with bilateral severe-to-profound high frequency hearing loss. Group median increase in air-conduction thresholds in the implanted ear for test frequencies 125-1000 Hz was < 15 dB across the population; both immediately and one year post-operatively. Eighty-eight percent of subjects used the Hybrid processor at one year post-op. Sixty-five percent of subjects had significant gain in speech recognition in quiet, and 73% in noise (≥ 20 percentage points/2 dB SNR). Mean SSQ subscale scores were significantly improved (+ 1.2, + 1.3, + 1.8 points, p < 0.001), as was mean HUI3 score (+ 0.117, p < 0.01). Combining residual hearing with CI gave 22-26 %age points mean benefit in speech recognition scores over CI alone (p < 0.01). Useful residual hearing was conserved in 88% of subjects. Speech perception was significantly improved over preoperative hearing aids, as was sound quality and quality of life.

The aim of this study was to demonstrate the presence of yeast and bacterial biofilms on the surface of tracheoesophageal voice prostheses (TVPs) by a double-staining technique with confocal laser scanning microscopy (CLSM). Biofilms of 12 removed TVPs were visualized by scanning electron microscopy, then stained with ConA-FITC and propidium iodide for CLSM. Microbial identification was by partial 16S rRNA gene analysis and ITS-2 sequence analysis. Microbial biofilms on the TVPs consisted of bacteria and filamentous cells. Bacterial cells were attached to the filamentous and unicellular yeast cells, thus forming a network. Sequence analyses of six voice prostheses identified the presence of a variety of bacterial and yeast species. In vivo studies showed that Klebsiella oxytoca and Micrococcus luteus efficiently attached to Candida albicans. CLSM with double fluorescence staining can be used to demonstrate biofilm formations composed of a mixture of yeast and bacterial cells on the surface of TVPs.

Even with six defective contacts, spanning can largely restore speech perception with the HiRes 120 speech processing strategy to the level supported by an intact electrode array. Moreover, the sound quality is not degraded. Previous studies have demonstrated reduced speech perception scores (SPS) with defective contacts in HiRes 120. This study investigated whether replacing defective contacts by spanning, i.e. current steering on non-adjacent contacts, is able to restore speech recognition to the level supported by an intact electrode array. Ten adult cochlear implant recipients (HiRes90K, HiFocus1J) with experience with HiRes 120 participated in this study. Three different defective electrode arrays were simulated (six separate defective contacts, three pairs or two triplets). The participants received three take-home strategies and were asked to evaluate the sound quality in five predefined listening conditions. After 3 weeks, SPS were evaluated with monosyllabic words in quiet and in speech-shaped background noise. The participants rated the sound quality equal for all take-home strategies. SPS with background noise were equal for all conditions tested. However, SPS in quiet (85% phonemes correct on average with the full array) decreased significantly with increasing spanning distance, with a 3% decrease for each spanned contact.

In spite of many satisfactory results, the clinical outcome of cochlear implantation is poorly predictable and further insight into the fundamentals of electrical nerve stimulation in this complex geometry is necessary. For this purpose we developed a rotationally symmetric volume conductor model of the implanted cochlea, using the Boundary Element Method (BEM). This configuration mimics the cochlear anatomy more closely than previous, unrolled models. The calculated potential distribution in the cochlea due to stimulating electrodes is combined with a multiple non-linear node model of auditory nerve fibres, which we recently developed. The combined model is used to compute excitation profiles of the auditory nerve for a variety of stimulus levels and electrode positions. The model predicts that the excitation threshold, the spatial selectivity and the dynamic range depend on the exact position of the electrode in the scala tympani. These results are in good agreement with recently published electrical ABR data. It is shown that the use of actively modelled nerve fibres is essential to obtain correct predictions for the biphasic stimuli typically used in cochlear implants and that unrolling the cochlear duct as done in previous models leads to erroneous predictions regarding modiolar stimulation.

... ITEM METADATA RECORD. Title: Predictors of language outcomes in children one to three years after cochlear implantation. Authors: Boons, Tinne Brokx, Jan Frijns, Johan Peeraer, Louis Philips,Birgit Vermeulen, Anneke Wouters, Jan Van Wieringen, Astrid. Issue Date: 2011. ...

Computed tomographic scanning of the petrous bone and magnetic resonance imaging sequences of the inner ear and cerebellopontine angle of a deaf patient were performed to find an explanation for his deafness, and to establish whether he would be a good candidate for cochlear implantation. The imaging features were considered pathognomonic for incomplete partition type III (IP type III). Further management and discussion of this deafness subtype are detailed.