Implant-Based Electrocochleography and Fluoroscopy During Cochlear Implant Surgery with Two Different Types of Electrode Arrays

Background

Indications for cochlear implantation are expanding to include more residual hearing. Therefore, less traumatic electrode arrays are needed in order to not interfere with cochlear function. We use implant-based electrocochleography (implant-ECochG) for monitoring the cochlea during electrode array insertion. To identify the causes of trauma or mechanical obstruction, we monitor the electrode array using high-resolution fluoroscopy.

Objective

We want to identify trauma or mechanical obstruction during electrode array insertion, and better understand the different types of ECochG responses. This could improve ECochG interpretation during surgeries without visual electrode array feedback. We compare the movements and different ECochG characteristics of the Advanced Bionics HiFocus Mid-Scala and SlimJ electrode arrays.

Methods

During cochlear implant surgery, we monitor the cochlea using implant-ECochG on recipients with significant residual hearing, and monitor the electrode array using fluoroscopy. The ECochG responses and visual observations from the fluoroscopy are compared with the pre-op and post-op audiograms.

Results

We have successfully monitored the electrode array insertion on more than ten patients involving the Mid-Scala and SlimJ electrodes. By comparing the ECochG responses with the electrode array movements, we are able to identify some causes of cochlear trauma, and differences between the two electrode array types.

Conclusion

ECochG and fluoroscopy gives valuable feedback during surgery, and information regarding causes of trauma. Fluoroscopy allows us to study the connection between ECochG behaviour and electrode array movements. Almost all implantations are done without fluoroscopy. In time, perhaps implant-ECochG can become a standard technique for CI surgeries when the residual hearing is significant.