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Cochlear implants rely on the integrity and correct functioning of auditory nerves. However, after sensorineural hearing loss there is a well-characterised degeneration of auditory nerves. One proposed mechanism of this degeneration is a reduction in the levels of neurotrophins, which are naturally occurring proteins that aid the growth and maintenance of neurons. Neurotrophin application to the cochlea of animals prevent morphological degeneration of the auditory nerves after deafness, making it a promising treatment for improving cochlear implant outcomes. The current study examined the effects of two major neurotrophins present in the cochlea, brain-derived neurotrophic factor and neurotrophic factor-3, on the function of individual auditory nerve fibres to cochlear implant stimulation. Guinea pigs were ototoxically deafened and then divided into groups that received treatment for four weeks with either brain derived neurotrophic factor, neurotrophin factor-3 or Ringer's solution as a control. Treatments were administered one week after deafening and delivered to the left cochlea through a combined cannula-electrode array that was attached to a mini-osmotic pump. Additional control groups included guinea pigs deafened for five weeks and an acutely deafened group. At the end of the treatment period responses of individual auditory nerve fibres to acute electrical stimulation of the cochlea at rates from 200-5000 pulses per second were recorded. Both brain derived neurotrophic factor and neurotrophin-3 treatment generally normalized the reduction in spike latency of auditory nerve fibres observed after deafness. BDNF significantly reduced thresholds compared to all control groups, while NT-3 did not. Both BDNF and NT-3 increased the first-spike dynamic range compared to untreated groups. These results were largely similar regardless of the stimulus rate used. These results suggest that neurotrophin treatment of the cochlea after deafness appears to preserve the latency of auditory nerve fibres, but may alter the response threshold and dynamic range. Further investigations are required to determine if neurotrophins are likely to preserve or improve auditory nerve function when used with a cochlear implant. [ABSTRACT FROM AUTHOR]

Fluctuations in cochlear implant impedance are associated with inner ear pathology after implantation. The current research explores whether these fluctuations coincide with episodes of hearing loss and/or vertigo, with a comparison between lateral wall and peri-modiolar electrode arrays. Seven-hundred and seventy recipients of Cochlear's slimstraight, lateral wall electrode (CI422) or peri-modiolar (CI512) electrode were investigated for impedance fluctuations. Impedance fluctuations were defined as a median rise of ≥ 4 kΩ across all intra-cochlear electrodes from baseline measurements taken two weeks after switch-on. Medical records were analysed from 193 of the 770 patients selected so that a comparable number would have impedance fluctuations as did not, for both electrode types. The slim straight, lateral wall electrode was found to fluctuate in impedance at a small, but significantly higher rate than the peri-modiolar array (17% vs 12% respectively). Impedance fluctuations were found to significantly correlate with medical events (either hearing loss, vertigo, or tinnitus). Overall, in the "fluctuation" group, 42 out of 75 patients (56%) demonstrated a clinical event during the impedance fluctuation, whereas 26 out of 118 patients (22%) of the "non-fluctuation" group had a clinical event. This significant difference existed with both implant type. The Positive Predictive Value (PPV) of the impedance fluctuation being associated with a clinical event is 0.56, and the Negative Predictive Value (NPV) is 0.78. There were no significant differences in the demographics of those who had an impedance fluctuation compared with those who did not. These results support the relationship between fluctuations in cochlear implant impedances and post-operative clinical events, including the loss of residual hearing and vertigo. Monitoring cochlear implant impedance may be a method for early detection, and so the prevention, of these events in the future. [ABSTRACT FROM AUTHOR]

Objective: To describe the experience and outcomes with the Slim Modiolar cochlear Implant Electrode. Materials and Methods: Retrospective review of all patients receiving the new CI532 implant. Outcome measures include; pre and postoperative speech perception, operative report details, electrode position as determined by X-ray in all cases and also Cone Beam CT in adults. Comparison was made with prior experience with the Contour perimodiolar CI512 electrode. Results: 135 CI532 implants were implanted prior to 30/01/2018. 43 in children and 92 in adults. Tip fold over occurred in 6 cases (4.4%). 4 were recognized and corrected intra-operatively, 2 recognized on post op CBCT required revision surgery. Of the 92 adults, CBCT confirmed scala tympani position in all but one case where placement had been into scala vestibuli. There were no translocations from ST to SV. This compares favourably with CI512 translocation rate of 17%. Speech perception outcomes demonstrated good performance with mean pre-op phoneme scores of 21.8 (+/- 15) increasing to 3 month post op of 61.2% (+/- 23). Where 12 month phoneme scores are available, CI532 compared favourably with a matched group of 512 recipients, 79.5 (14) vs 69.4 (17) respectively. Conclusion: The slim modiolar, CI532 electrode has provided very reliable scala tympani position with a low rate of tip fold over. The speech perception outcomes achieved compare favourably with our experience with previous perimodiolar electrodes. [ABSTRACT FROM AUTHOR]