Cochlear implant explantation: An in vitro model to evaluate electrode explant force and trauma

Abstract

Objectives

Removal of a cochlear implant and its intracochlear electrode array is sometimes necessary, potentially causing cochlear explant trauma. Explantation typically occurs years post-implantation by which time reactive tissue has formed around the electrode. We aimed to create an in-vitro electrode explant model to examine explant forces and intracochlear trauma across multiple electrode types and insertion depths.

Study design

An in-vitro model using gel to represent tissue surrounding the electrode was developed. Pre-curved electrodes and straight electrodes at different insertion depths (20mm, 25mm, 28mm) were explanted from the model. During explantation, explant force was measured, and high-definition videos were recorded to capture electrode exit path and gel disruption.

Results

Explant force patterns varied based on electrode position in the scala tympani. Explant forces did not correlate with gel disruption, which represented explant trauma. The least gel disruption occurred with pre-curved electrodes and the under-inserted straight electrode. The greatest disruption occurred with the overly inserted straight electrode.

Conclusion

An in-vitro model using gel to mimic tissue surrounding the electrode may provide insights into potential electrode explant trauma. Explant force did not correlate with explant trauma in our model. Pre-curved electrodes and shallower insertion depth of a straight electrode resulted in the least amount of explant trauma.

Keywords:

• Cochlear implant explantation
• Explant trauma
• Perimodiolar electrode
• Lateral wall electrode

Disclosure statement

Dr. Roland is on the Cochlear Americas Surgical Advisory Board.

Additional information

Notes on contributors

Leena Asfour

Leena Asfour (MD) is an ENT resident at New York University. She also completed her medical education at New York University. Her research focuses on auditory brainstem implant outcomes and quality of life in the pediatric population. She is also interested in cochlear implantation outcomes and quality of life in bimodal users.

Frank Risi

Frank Risi is an engineer and the Global Group Product Manager for Surgical and Implants at Cochlear Limited. His research is related to cochlear implant electrode dynamics and their interactions with cochlea anatomy as well as improving the electrode neural interface.

Hanif Miah

Hanif Miah (M Eng., UNSW) is a Principal Technical Officer, Research and Development at Cochlear Limited. His research focuses on testing cochlear implant electrode concepts, developing test methods and validating hypotheses against experimental research.

J. Thomas Roland Jr

J. Thomas Roland, Jr. (MD) is the Mendik Foundation Chairman of the Department of Otolaryngology-Head and Neck Surgery, Professor of Otolaryngology & Neurosurgery, Co-Director of the NYU Langone Health Cochlear Implant Center and Co-Director of the Neurofibromatosis Center at NYU Langone Medical Center in New York, NY. The bulk of Dr. Roland’s research is related to cochlear implant electrode design and implementation, auditory brainstem implant in children with cochlear nerve deficiency, outcomes with skull base tumors and facial nerve reanimation.