Objective: To determine in a guinea pig model the factors of invasiveness of a bipolar electrode implanted in the horizontal semicircular canal (HSC) and to evaluate the consequences on hearing of electrical stimulation of the ampullary nerve.
Design: Sixteen guinea pigs divided into four groups underwent surgical opening of the HSC of one ear as follows: control (group 1), cyanoacrylate glue application on the HSC opening (group 2), electrode implantation with cyanoacrylate glue on the HSC opening (group 3), and electrode implantation with electrical stimulation (1 hr/day) for 9 days (group 4). Auditory brainstem responses were recorded before and after surgery and after electrical stimulation. The effectiveness of electrical stimulation in producing a horizontal vestibulo-ocular reflex was evaluated by recording eye movement with video-oculography.
Results: Group 1 animals showed hearing loss, and in group 2, sealing the HSC opening with cyanoacrylate glue preserved the hearing thresholds. After electrode implantation, seven of the eight animals showed hearing loss compared with preoperative values. Electrical stimulation did not induce additional hearing loss.
Conclusion: Electrode implantation at the canal level entailed a risk of hearing loss in an animal model, but electrical stimulation of the horizontal ampullary nerve did not further alter hearing function.