UC Irvine

Objectives/hypothesis

To evaluate a transcanal approach for placement of a stimulating electrode array in the cochlear nerve.

Study design

Prospective cadaveric temporal bone study.

Methods

Ten human cadaveric temporal bones were dissected. Both a facial recess approach with mastoidectomy and a transcanal approach using the novel technique were performed in each bone. A middle fossa dissection of the internal auditory canal was performed to confirm the position of the electrode in the cochlear nerve.

Results

The transcanal approach offered a direct approach to the cochlear nerve in all 10 bones. The procedure was quicker than the facial recess approach and did not endanger the facial or chorda tympani nerves. Inspection of the medial end of the internal auditory canal confirmed correct placement of the electrode in the cochlear nerve. In contrast, anatomical constraints, specifically the position of the facial nerve, blocked access to the cochlear nerve by the facial recess approach in three of the specimens to achieve the exposure to place the electrode at a perpendicular angle to the cochlear nerve. Sacrifice of the chorda tympani was necessary in five of the seven bones in which the cochlear nerve could be accessed.

Conclusions

The transcanal approach offers a simpler, safer approach for cochlear nerve implantation compared to the facial recess approach. This approach can be accomplished in less time and avoids the hazards of dissection around the facial nerve. Use of the proposed approach will facilitate development of intraneural stimulation for an improved auditory prosthesis.