Introduction: Transimpedance measurements from cochlear implant electrodes have the potential to identify anomalous electrode array placement, such as tip fold-over (TFO) or fold-back, basal electrode kinking, or buckling. Analysing transimpedance may thus replace intraoperative or post-operative radiological imaging to detect any potential misplacements. A transimpedance algorithm was previously developed to detect deviations from a normal electrode position with the aim of intraoperatively detecting TFO. The algorithm had been calibrated on 35 forced, tip folded electrode arrays in six temporal bones to determine the threshold criterion required to achieve a sensitivity of 100%. Our primary objective here was to estimate the specificity of this TFO algorithm in patients, in a prospective study, for a series of electrode arrays shown to be normally inserted by post-operative imaging. Methods: Intracochlear voltages were intraoperatively recorded for 157 ears, using Cochlear’s Custom Sound™ EP 5 electrophysiological software (Cochlear Ltd., Sydney, NSW, Australia), for both Nucleus® CI512 and CI532 electrode arrays. The algorithm analysed the recorded 22 × 22 transimpedance matrix (TIM) and results were displayed as a heatmap intraoperatively, only visible to the technician in the operating theatre. After all clinical data were collected, the algorithm was evaluated on the bench. The algorithm measures the transimpedance gradients and corresponding phase angles (θ) throughout the TIM and calculates the gradient phase range. If this was greater than the predetermined threshold, the algorithm classified the electrode array insertion as having a TFO. Results: Five ears had no intraoperative TIM and four anomalous matrices were identified from heatmaps and removed from the specificity analysis. Using the 148 remaining data sets (n = 103 CI532 and n = 45 CI512), the algorithm had an average specificity of 98.6% (95.80%–99.75%). Conclusion: The algorithm was found to be an effective screening tool for the identification of TFOs. Its specificity was within acceptable levels and resulted in a positive predictive value of 76%, with an estimated incidence of fold-over of 4% in perimodiolar arrays. This would mean 3 out of 4 cases flagged as a fold-over would be correctly identified by the algorithm, with the other being a false positive. The measurements were applied easily in theatre allowing it to be used as a routine clinical tool for confirming correct electrode placement.

Objective: To investigate the clinical performance, safety, and patient-reported outcomes of an active osseointegrated steady-state implant system that uses piezoelectric technology. Study Design: A prospective, multicenter, open-label, single-arm, within-subject clinical investigation. Setting: Three tertiary referral clinical centers located in Melbourne, Sydney, and Hong Kong. Patients: Twenty-nine adult subjects, 24 with mixed hearing loss or conductive hearing loss and 5 with single-sided sensorineural deafness. Intervention: Implantation with the Cochlear Osia 2 System. Main Outcome Measures: Audiological threshold evaluation and speech recognition in quiet and in noise. Patient satisfaction and safety. Results: At 6-month follow-up after surgery, a mean improvement in pure-tone average of 26.0 dB hearing level and a mean improvement of 8.8 dB signal-to-noise ratio in speech reception threshold in noise was achieved with the investigational device as compared with the unaided situation. Usability of the investigational device was rated 71.4/100 mm for sound processor retention and 81.4/100 mm for overall comfort using a visual analog scale. Conclusion: These outcomes confirm the clinical safety, performance, and benefit of an innovative active transcutaneous bone conduction implant using a piezoelectric transducer design in subjects with conductive hearing loss, mixed hearing loss, or single-sided sensorineural deafness.

Postoperative inflammation and the formation of fibrotic tissue around the intracochlear electrode array are often held responsible for negative outcomes in cochlear implant recipients. Here we test the effectiveness of intracochlear delivery of dexamethasone via a drug-eluting electrode array in reducing fibrotic tissue formation, assessed via measurement of both monopolar and four-point electrode impedance. Adult guinea pigs were bilaterally implanted with a dexamethasone-eluting array (left ear) and a standard non-eluting array (right ear). Arrays were electrically stimulated daily for 4 weeks, commencing 1 week after implantation, and impedance measured both before and after stimulation. Histological assessment of the tissue was made at the end of the 5-week period. The dexamethasone-eluting array did not reduce monopolar (MP1 + 2) electrode impedance over the course of 5 weeks, and no significant difference was observed in fibrotic tissue, new bone growth, or spiral ganglion neuron density between array types. However, four-point impedance, which provides an indication of the local environment at the neural-tissue interface, was significantly lower in the presence of dexamethasone. A strong relationship was seen between four-point and monopolar impedance for individual electrode arrays, with the exception of the standard array after daily electrical stimulation. This group instead showed a significant correlation between the final four-point impedance measure and percentage of fibrous tissue and new bone growth. In conclusion, this study demonstrated that dexamethasone influences four-point electrode impedance as well as the relationship between fibrotic tissue and impedance, and that both outcomes are shaped by daily electrical stimulation. These results suggest a change occurs at the local tissue-electrode interface in the presence of sustained, intracochlear release of dexamethasone.

The electrochemical performance of platinum electrodes was assessed in vitro and in vivo to determine the impact of electrode implantation and the relevance of in vitro testing in predicting in vivo behaviour. A significant change in electrochemical response was seen after electrode polarisation. As a result, initial in vitro measurements were poor predictors of subsequent measurements performed in vitro or in vivo. Charge storage capacity and charge density measurements from initial voltammetric measurements were not correlated with subsequent measurements. Electrode implantation also affected the electrochemical impedance. The typically reported impedance at 1 kHz was a very poor predictor of electrode performance. Lower frequencies were significantly more dependent on electrode properties, while higher frequencies were dependent on solution properties. Stronger correlations in impedance at low frequencies were seen between in vitro and in vivo measurements after electrode activation had occurred. Implanting the electrode increased the resistance of the electrochemical circuit, with bone having a higher resistivity than soft tissue. In contrast, protein fouling and fibrous tissue formation had a minimal impact on electrochemical response. In vivo electrochemical measurements also typically use a quasi-reference electrode, may operate in a 2-electrode system, and suffer from uncompensated resistance. The impact of these experimental conditions on electrochemical performance and the relevance of in vitro electrode assessment is discussed. Recommended in vitro testing protocols for assessing bionic electrodes are presented.

The objective of the study was to compare the widths of forward masking profiles in subjects implanted with the Nucleus® 24 Contour™ or straight electrode array. The Contour array is typically positioned closer to the modiolus than the straight array. Subjects were fourteen postlingually hearing-impaired adults with severe-profound hearing loss, seven used the Contour array and seven used the straight array. Forward masking profiles were measured at three positions along the array (apical, mid, and basal) using maskers at the 15% loudness level. It was hypothesized that masking profile widths would be more sensitive to differences in distance from the neural structures using low-level maskers. Masking width was calculated at the 50% point of the masking peak amplitude. There were no significant differences in masking widths between Contour and straight array subject groups. Current levels for hearing thresholds and maximum comfortable listening levels were significantly lower for the Contour array subjects.

(2018). Longitudinal outcomes of children with hearing impairment (LOCHI): 5 year data. International Journal of Audiology: Vol. 57, No. sup2, pp. S1-S2.