gms | German Medical Science

Fourth International Symposium and Workshops: Objective Measures in Cochlear Implants

Medical University of Hannover

01.06. bis 04.06.2005, Hannover

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Estimation of the refractory period based on electrically evoked compound action potentials

Meeting Abstract

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  • corresponding author M. Sainz - Dpto. Cirugía y sus Especialidades, Universidad de Granada, 18071 Granada, Spain
  • A. de la Torre - Dpto. Electrónica y Tecn. Comp., Universidad de Granada, 18071 Granada, Spain
  • C. Roldán - Servicio ORL, Hospital Universitario S. Cecilio, 18012 Granada, Spain
  • I. Álvarez - Dpto. Electrónica y Tecn. Comp., Universidad de Granada, 18071 Granada, Spain
  • H. Spitzer - Institute of Applied Physics, University Innsbruck, Austria
  • H. Schößer - Med-El Medical Electronics, Worldwide Headquarters, Innsbruck, Austria
  • K. Veekmans - Med-El Medical Electronics, Worldwide Headquarters, Innsbruck, Austria
  • J.M. Ortigosa - Dpto. Electrónica y Tecn. Comp., Universidad de Granada, 18071 Granada, Spain

Medical University of Hannover, Department of Otolaryngology. Fourth International Symposium and Workshops: Objective Measures in Cochlear Implants. Hannover, 01.-04.06.2005. Düsseldorf, Köln: German Medical Science; 2005. Doc05omci088

Die elektronische Version dieses Artikels ist vollständig und ist verfügbar unter: http://www.egms.de/de/meetings/omci2005/05omci088.shtml

Veröffentlicht: 31. Mai 2005

© 2005 Sainz et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.

Gliederung

Text

Introduction

The amplitude of compound action potentials is decreased when two consecutive stimuli separated by a short time interval are presented. This effect is consequence of the depolarization of the neurons with the first stimulus when the interval is shorter than the refractory period, because most neurons are not re-polarized and do not fire with the second stimulus. By controlling the interval between both stimuli, compound action potentials can be used to estimate the refractory period.

Materials and Methods

The study includes 4 patients implanted with the MED-EL Pulsar device. Evoked compound action potentials were recorded by means of the auditory response telemetry incorporated in this device. The responses were recorded by presenting groups of two stimuli separated by a controlled time-interval in the range 0.5ms–8ms. The function amplitude versus time-interval provides information about the refractory period of the neurons and about its distribution for the population of neurons.

Results

For time-intervals of 0.5ms no action potentials were observed. For 8ms, the responses were similar to that obtained with a single stimulus. The amplitude growth function (as a function of time-interval) presents differences among the patients. Patients with recent hearing experience presented the shortest refractory period (some response for 1.0ms), while patients with no hearing experience presented the longest one (no response until 6ms).

Conclusions

Compound action potentials provide an estimation of the refractory period of the neurons of the auditory nerve. Therefore, this objective measurement can be applied to evaluate the state of the neural ends in the vicinity of each electrode of the cochlear implant.