Intraoperative audiologisch-technische Diagnostik bei der Cochleaimplantatversorgung

International Consensus Statements on Intraoperative Testing for Cochlear Implantation Surgery

OBJECTIVES

A wide variety of intraoperative tests are available in cochlear implantation. However, no consensus exists on which tests constitute the minimum necessary battery. We assembled an international panel of clinical experts to develop, refine, and vote upon a set of core consensus statements.

DESIGN

A literature review was used to identify intraoperative tests currently used in the field and draft a set of provisional statements. For statement evaluation and refinement, we used a modified Delphi consensus panel structure. Multiple interactive rounds of voting, evaluation, and feedback were conducted to achieve convergence.

RESULTS

Twenty-nine provisional statements were included in the original draft. In the first voting round, consensus was reached on 15 statements. Of the 14 statements that did not reach consensus, 12 were revised based on feedback provided by the expert practitioners, and 2 were eliminated. In the second voting round, 10 of the 12 revised statements reached a consensus. The two statements which did not achieve consensus were further revised and subjected to a third voting round. However, both statements failed to achieve consensus in the third round. In addition, during the final revision, one more statement was decided to be deleted due to overlap with another modified statement.

CONCLUSIONS

A final core set of 24 consensus statements was generated, covering wide areas of intraoperative testing during CI surgery. These statements may provide utility as evidence-based guidelines to improve quality and achieve uniformity of surgical practice.

Effects of Intraoperative Cochlear Implant Electrode Conditioning on Impedances and Electrically Evoked Compound Action Potentials

OBJECTIVE

The current study investigates whether, during a Cochlear Implant (CI) surgery, conditioning (i.e. applying short bursts of electrical stimulation) within a saline solution can have positive effects on subsequent intra-operative measurements. We hypothesize that, based on previous research, the impedance values will be reduced, and that the reproducibility of Electrically Evoked Compound Action Potentials (ECAPs) is improved as a result of conditioning.

METHODS

We conditioned half of the electrode contacts, within a saline solution, before CI insertion, using 23 MED-EL implants. Impedance was measured for both the conditioned and non-conditioned groups at five time points. Repeated ECAP recordings were measured and compared between the conditioned and non-conditioned groups.

RESULTS

Impedance of the electrode contacts were reduced by 31% after conditioning in saline solution; however, there were no clinically relevant differences after the implantation of the electrode array. The hypothesis that measurement reproducibility would be increased after conditioning could not be confirmed with our data. Within the saline solution, we observed that 44% of the electrode contacts were covered with air bubbles, which most disappeared after implantation. However, these air bubbles limited the effectiveness of the conditioning within the saline solution. Lastly, the effect of conditioning on the reference electrode stimulation was approximately 16% of the total reduction in impedance.

CONCLUSION

Our data does not suggest that intraoperative conditioning is clinically required for cochlear implantation with MED-EL implants. Additionally, an in-vivo ECAP recording can be considered as a method of conditioning the electrode contacts.

SIGNIFICANCE

We confirm that the common clinical practice does not need to be changed.

Transimpedance Matrix Measurements Reliably Detect Electrode Tip Fold-over in Cochlear Implantation

OBJECTIVE

During cochlear implantation, electrophysiological tests are performed to document safe technical functioning of implant and electrodes. In rare cases, the apical part of the electrode folds over during insertion. The data from transimpedance matrix (TIM) measurements enable the generation of a heat map or TIM profile measuring the spatial distribution of voltage. The aim of this study was to determine the accuracy of heat-map TIM profiles and compare them with spread of excitation (SOE) measurements and intraoperative imaging for prediction of electrode malposition.

STUDY DESIGN

Non-randomized study.

SETTING

Tertiary referral center.

PATIENTS AND INTERVENTIONS

One hundred patients who underwent cochlear implantation with completed TIM measurements, SOE data and perioperative imaging met the inclusion criteria and were enrolled.

MAIN OUTCOME MEASURE

The electrophysiological data on the electrode array positioning was compared with temporal bone imaging.

RESULTS

In seven cases, TIM measurements showed irregular results. In two cases, irregular TIM profiles were registered, but SOE data and 3D x-ray of the temporal bone didn't display deviated electrode positioning. A 3D x-ray of the skull displayed electrode tip fold-over in four cases and electrode buckling in one case. Sensitivity of TIM measurements and SOE data was 100%, specificity of TIM measurements was 97.89%, and specificity of SOE data was 98.93%.

CONCLUSION

Out of 100 patients using TIM measurements for detection of electrode malpositioning, no false negative cases were detected. TIM measurements successfully detect electrode malposition in an intraoperative setting. Different heat map patterns may be observed depending on location and type of malposition.

Electric compound action potentials (ECAPs) and impedances in an open and closed operative site during cochlear implantation

INTRODUCTION

In patients undergoing cochlear implantation, intraoperative measures of impedance and electrically evoked compound action potentials (ECAPs) are used to confirm device integrity and electrode array position. However, these electrophysiological parameters have been shown to decrease over time, with a small decrement observable as early as 24 h post implantation and becoming more apparent after 6 months. Whether the intraoperatively measured impedances and ECAPs recorded immediately after electrode insertion versus later in the operation or in an open versus closed operative site vary has not been documented. Such variation in measurement procedure may affect the ultimate operative outcome.

PATIENTS AND METHODS

Between February and October 2016, 38 patients received a cochlear implant (Cochlear^®), with half receiving a CI 522 device and the other half receiving a CI 512 device. These patients were distributed into three groups. In the first (group A; n = 21), the impedance and threshold neural response telemetry (tNRT) measures were taken before (M1) and after cutaneous suture (M2), whereas in the second group (group B; n = 11) they were taken twice in the open operative site, once at the time of electrode insertion (M1) and then again 10 min later (M2). The last group (group C; n = 6) was measured only once after a 10 min waiting time before closing the operative site.

RESULTS

tNRTs of both group A and B were significantly higher at M1 than measured at M2. The magnitude of change in tNRT did vary significantly by group (P = .027) with group A having a bigger decrease than group B. For impedances there was evidence for a significant difference in M2 between the three groups (P = .012), with group C having significantly higher values compared to group A and B.

CONCLUSION

Intraoperative tNRT measures change significantly over time, including within the first 10 min of implantation. One underlying etiology of this phenomenon for tNRTs seems to be the condition of the surgical site whereas changes of impedances can be best explained by the 'electrochemical cleaning' theory associated with the first stimulation of the electrode. However, for both impedances and tNRTs there also is an important impact of time as well as of acute perioperative changes in electrical conductivity.