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. 2016 May;126(5):1193-200.
doi: 10.1002/lary.25602. Epub 2015 Sep 11.

Round window electrocochleography before and after cochlear implant electrode insertion

Oliver F Adunka  1   2 , Christopher K Giardina  2 , Eric J Formeister  2 , Baishakhi Choudhury  2 , Craig A Buchman  2 , Douglas C Fitzpatrick  2
Affiliations

Round window electrocochleography before and after cochlear implant electrode insertion

Oliver F Adunka et al. Laryngoscope. 2016 May.

Abstract

Objective/hypothesis: Previous reports have documented the feasibility of utilizing electrocochleographic (ECoG) responses to acoustic signals to assess trauma caused during cochlear implantation. The hypothesis is that intraoperative round window ECoG before and after electrode insertion will help predict postoperative hearing preservation outcomes in cochlear implant recipients.

Study design: Prospective cohort study.

Methods: Intraoperative round window ECoG responses were collected from 31 cochlear implant recipients (14 children and 17 adults) immediately prior to and just after electrode insertion. Hearing preservation was determined by postoperative changes in behavioral thresholds.

Results: On average, the postinsertion response was smaller than the preinsertion response by an average of 4 dB across frequencies. However, in some cases (12 of 31) the response increased after insertion. The subsequent hearing loss was greater than the acute loss in the ECoG, averaging 22 dB across the same frequency range (250-1,000 Hz). There was no correlation between the change in the ECoG response and the corresponding change in audiometric threshold.

Conclusions: Intraoperative ECoG is a sensitive method for detecting electrophysiologic changes during implantation but had limited prognostic value regarding hearing preservation in the current conventional cochlear implant patient population where hearing preservation was not intended.

Level of evidence: 2b Laryngoscope, 126:1193-1200, 2016.

Keywords: Electrocochleography; cochlear implants; cochlear physiology; hearing preservation; intraoperative monitoring.

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Conflict of interest statement

Conflict of Interest:

Supported by a grant from the MED-El Corporation and the Howard Holderness Distinguished Medical Scholars Program at the University of North Carolina.

Figures

Figure 1
Figure 1
Example ECoG responses to 500 Hz tone burst stimuli before and after device insertion. The left panels show the waveform to condensation phase stimuli while the right panels show the spectrum. A: example of a case where the response decreased after insertion; B: Example of a case where the response increased after insertion; C: Example of a case where the response was approximately the same before and after device insertion.
Figure 2
Figure 2
Changes in ECoG response magnitude after implantation. A: Mean response versus stimulus frequency. Error bars are standard error (n=31). The tones bursts were delivered at 90 dB nHL. The post-implant data is shifted slightly in frequency for visual presentation. B: Distribution of 4-tone average ECoG response. Symbol colors for each case are from the 400 Hz data in Figure 2A.
Figure 3
Figure 3
Changes in the ECoG response magnitude for different stimulus frequencies. A: 500 Hz; B: 250 Hz; C: 750 Hz; D: 1,000 Hz. Colors are the same as from Figure 2B.
Figure 4
Figure 4
Pure tone thresholds before and after implantation. A: Average thresholds for 3 frequencies. B: Three-tone thresholds before and after implantation. Symbols and colors represent the ECoG results using the same colors and symbols as in Figure 2B.
Figure 5
Figure 5
Lack of correlation between the ECoG response losses and hearing threshold increases.
Figure 6
Figure 6
Brand comparison pre- and post-insertion. A: Intraoperative ECoG response. B: Hearing thresholds. See Table I for the different devices used.
See this image and copyright information in PMC

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