Preserved Low-Frequency Hearing Following 20-mm Cochlear Implantation

Evaluation of Insertion Forces and Cochlea Trauma Following Robotics-Assisted Cochlear Implant Electrode Array Insertion

HYPOTHESIS

The objective was to evaluate the effect of cochlear implant (CI) insertion technique on electrode insertion forces and intracochlear trauma. We hypothesize that robotics-assisted insertions will reduce insertion forces and intracochlear trauma compared with manual insertions.

BACKGROUND

Variability in CI outcomes exists across patients, implant centers, surgeons, and electrode types. While surgical techniques that reduce electrode insertion trauma are well established, insertion trauma remains one contributing factor to variability in CI outcomes. Previous work demonstrates that micromechanically controlled insertion tools reduce both maximum insertion forces and insertion variability compared with manual insertions.

METHODS

CI electrode insertions were performed either by hand (n = 12) or utilizing a robotics-assisted tool (n = 12) in fresh frozen, human cadaveric cochleae using electrodes from four different CI manufacturers. Electrodes array insertion forces were additionally evaluated in benchtop cochlea models. Following cadaveric insertions, samples were imaged via high resolution x-ray microscopy to evaluate electrode position and intracochlear trauma events based on a modified Eshraghi scale.

RESULTS

Electrode array insertions performed by robotics-assisted system showed significantly lower insertion forces and variability. Manual electrode array insertions had a significantly higher overall trauma score of 3.1 ± 2.0 compared with 0.9 ± 1.0 for robotics-assisted insertions. Robotics-assisted insertions had higher rate of basilar membrane elevations while manual insertions showed higher rates of severe trauma events.

CONCLUSIONS

The robotic-assisted insertion system reduced trauma events associated with CI electrode insertions in cadaveric cochleae compared with manual insertions. Surgical devices which help to precisely and more consistently insert electrodes may improve CI outcomes and hearing preservation.

Initial hearing preservation outcomes of cochlear implantation with a slim perimodiolar electrode array

OBJECTIVE

To assess the slim modiolar array as a hearing preservation electrode.

METHODS

Retrospective chart review of adult, post-lingual CI recipients implanted with slim modiolar array Sept 2016 to July 2017 in a tertiary referral center. Baseline audiograms were obtained within six months of initial CI evaluation. Patients with low frequency pure tone average (LFPTA) (125, 250, 500 Hz) <80 dB were considered HP candidates. Postoperative audiograms were obtained within 48 h before activation. Successful HP was considered as (1) retention of LFPTA threshold <80 dB and (2) change in threshold from pre- to post-operative.

RESULTS

Sixty-three patients received the slim perimodiolar array and 42 were HP candidates. Post-operative audiograms were obtained for 39 of 42 patients an average of 28.92 days after surgery. 56.4% of HP candidates retainedLFPTA <80 dB. Mean ΔLFPTA was 24.15 dB (±16.14; p < 0.001). 56.4% of HP candidates experienced Δ LFPTA <20 dB; 69.2% <30 dB. Functional hearing preservation was more successful in lower frequencies where starting thresholds were better - 78% with LFPTA <50 dB retained serviceable hearing at activation. The postoperative change was similar in each low frequency (Δ125 Hz: mean 21.25 +/- 14.76 (N = 28); Δ250 Hz: 26.28 +/- 19.29 (N = 39); Δ500 Hz: 25.00 +/- 17.73 (N = 39)).

CONCLUSIONS

The slim perimodiolar array is moderately effective at immediate hearing preservation. In subjects with preoperative audiometric profiles similar to those in prior EAS trials, immediate HP is comparable.

Factors affecting residual hearing preservation in cochlear implantation

The likelihood of residual hearing preservation in cochlear implantation (CI) is related to surgical factors such as type of cochleostomy (trans-fenestral vs. promontorial), use of lubricants and protective drugs, and device-related factors such as shape, length and flexibility of the array. We investigated the impact of these factors on the hearing preservation rate in adults and children with conventional audiological indications to CI. Eighty-two children aged 1-9 years and 73 adults (16-79 years) received a CI in the right (59%) or left ear (41%). An anterior-inferior promontorial cochleostomy was performed in 143 ears (92%); a trans-fenestral approach was used in 12 (8%). A perimodiolar electrode was implanted in 144 ears (93%), and a straight electrode in the remaining 11 (7%). Overall, some post-operative hearing was retained in 39% of ears. The rate of preservation was higher at the low than at the high frequencies. When correlated with age, side of implant, implant model and type of cochleostomy, the mean threshold variations did not reach statistical significance for any of these variables. A slight trend in favour of better residual hearing preservation in children vs. adults was seen, especially at lower frequencies.

Residual Hearing Preservation with the Evo® Cochlear Implant Electrode Array: Preliminary Results

Introduction The preservation of residual hearing is currently an important challenge for cochlear implant surgeries. Indeed, if patients exhibit functional hearing after cochlear implantation, they can benefit from the combination of acoustical stimulation, usually in the low-frequencies and electrical stimulation in the high-frequencies. This combined mode of stimulation has proven to be beneficial both in terms of speech perception and of sound quality. Finding the right procedures for conducting soft-surgeries and designing electrode arrays dedicated to hearing preservation is an open issue. Objective The objective of this study is to evaluate the combination of a soft-surgery procedure implicating round-window insertion and the use of dexamethasone and hyaluronic acid during surgery, with the use of a specifically designed straight soft electrode array, on hearing preservation in patients with functional hearing in the low frequencies. Methods This pre-clinical trial was conducted on seven patients with residual hearing in the low frequencies. The surgical method used employed a round window insertion and the use of topical dexamethasone. Results The soft-surgery protocol could be successfully followed in five patients. In this group, the average hearing threshold shift compared with pre-operative values was of 18.7 +/- 16.1 dB HL up to 500 Hz and 15.7 +/- 15.1 up to 1 kHz, demonstrating satisfying levels of hearing preservation. Conclusion We were able to demonstrate the possibility of preserving residual hearing in most of the patients using the EVO electrode. Significant residual hearing preservation levels were was obtained when a soft surgical approach involving round window insertion, dexamethasone and hyaluronic use during the surgery.