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Updated: Dec 6, 2025
Cochlear Implantation in the Guinea Pig
Published on: June 15, 2018
Cochlear implantation in an animal model documents cochlear damage at the tip of the implant
José Santos Cruz de Andrade1, Peter Baumhoff2, Oswaldo Laércio Mendonça Cruz3
1Universidade Federal de São Paulo (UNIFESP), Departamento de Otorrinolaringologia e Cirurgia de Cabeça e Pescoço, São Paulo, SP, Brazil; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Capes), Brasília, DF, Brazil; Institute of Audioneurotechnology (VIANNA) & Department of Experimental Otology, Department of Otolaryngology, Medical University Hannover, Hannover, Germany.
Introduction:
Electrocochleography has recently emerged as a diagnostic tool in cochlear implant surgery, purposing hearing preservation and optimal electrode positioning.
Objective:
In this experimental study, extra-cochlear potentials were obtained during cochlear implant surgery in guinea pigs. The aim was to determine electrophysiological changes indicating cochlear trauma after cochleostomy and after electrode implantation in different insertion depths.
Methods:
Normal-hearing guinea pigs (n = 14) were implanted uni- or bilaterally with a multichannel electrode. The extra-cochlear cochlear nerve action potentials were obtained in response to acoustic stimuli at specific frequencies before and after cochleostomy, and after introduction of the electrode bundle. After the electrophysiological experiments, the guinea pigs were euthanized and microtomography was performed, in order to determine the position of the electrode and to calculate of the depth of insertion. Based on the changes of amplitude and thresholds in relation to the stimulus frequency, the electrophysiological data and the position obtained by the microtomography reconstruction were compared.
Results:
Cochleostomy promoted a small electrophysiological impact, while electrode insertion caused changes in the amplitude of extra-cochlear electrophysiological potentials over a wide range of frequencies, especially in the deepest insertions. There was, however, preservation of the electrical response to low frequency stimuli in most cases, indicating a limited auditory impact in the intraoperative evaluation. The mean insertion depth of the apical electrodes was 5339.56 μm (±306.45 - 6 inserted contacts) and 4447.75 μm (±290.23 - 5 inserted contacts).
Conclusions:
The main electrophysiological changes observed during surgical procedures occurred during implantation of the electrode, especially the deepest insertions, whereas the cochleostomy disturbed the potentials to a lesser extent. While hearing loss was often observed apical to the cochlear implant, it was possible to preserve low frequencies after insertion.
