Publication Cover
Cochlear Implants International
An Interdisciplinary Journal for Implantable Hearing Devices
Volume 19, 2018 - Issue 2
273
Views
3
CrossRef citations to date
0
Altmetric
Original articles

A new approach for the determination of ECAP thresholdsFootnote

, &
Pages 104-114 | Published online: 22 Nov 2017
 

Abstract

Background: Electrically evoked compound action potentials (ECAPs) of the auditory nerve are routinely recorded for testing the cochlear implant integrity and its functional connection to the auditory system. The response thresholds derived from ECAP recordings are widely used as a helpful guide in the fitting of the dynamic range of electric stimulation, although they may not always predict the behavioral thresholds of individuals well. Conventionally, this threshold is based on the identification of a minimum N peak and maximum P peak and linear extrapolation of the resulting amplitude growth function (AGF). As an alternative, a new procedure involving numeric signal processing and requiring less user intervention is presented here.

Data acquisition: In 12 adults implanted with MED-EL FLEX28 electrodes, two series of ECAPs were recorded immediately after implantation: (i) a full profile involving all 12 channels across the whole stimulus range in steps of 200 current units and (ii) a high resolution section (20 records in the immediate neighborhood of the threshold) of the AGF in one selected channel.

Data treatment: It was observed that N and P wave latencies do not depend on stimulus intensity. Fixed time windows were hence defined for stimulus plus noise and noise alone regions. In these windows, the variance of the compound signal representing response and noise is extracted, whereas the noise variance is extracted from the tail of the curve following this time window. The base line is corrected by fitting an exponential function to reduce stimulus or amplifier artifacts. The response threshold is then derived from the response to noise ratio which should exceed the limit of 6 dB.

Results: The ECAP thresholds obtained from the new procedure coincide well with those determined by the conventional linear extrapolation of the AGF and they correlate to a greater degree with psychometric thresholds than the existing approach.

Conclusions: The new ECAP algorithm looks promising and may reduce the need for user intervention in determining thresholds.

Notes

† 13th International Congress on Cochlear Implants and Other Implantable Auditory Technologies, München, Germany, June 18th to 21st, 2014 and at the 10th Asia Pacific Symposium on Cochlear Implant and Related Sciences (APSCI) Beijing, China, April 30th to May 4th 2015.

Log in via your institution

Log in to Taylor & Francis Online

PDF download + Online access

  • 48 hours access to article PDF & online version
  • Article PDF can be downloaded
  • Article PDF can be printed
USD 65.00 Add to cart

Issue Purchase

  • 30 days online access to complete issue
  • Article PDFs can be downloaded
  • Article PDFs can be printed
USD 380.00 Add to cart

* Local tax will be added as applicable

Related Research

People also read lists articles that other readers of this article have read.

Recommended articles lists articles that we recommend and is powered by our AI driven recommendation engine.

Cited by lists all citing articles based on Crossref citations.
Articles with the Crossref icon will open in a new tab.