Prolonged electrode implantation in experimental studies. Critical evaluation of a technique

Stainless steel electrodes were chronically implanted through the right facial canal of 30 guinea pigs, close to the potential generator (VIII nerve). Compound action potential (CAP) thresholds, N1 latencies and input-output curves were recorded on day of implantation and 2, 4 and 8-12 weeks later. In the same sitting, auditory evoked brain stem response (ABR) thresholds, latencies and inter-peak-latencies were measured on both sides as a control. N1 thresholds and latencies at low and high intensities were stable. N1 amplitudes, however, showed some variation. Rate of infection was low and reimplantation was successful. Preserving the facial nerve as a land mark was found advantageous, particularly on reimplantation, and did not affect the CAP recording. The technique, originally described by Hildesheimer et al., proved to be reproducible. A few technical difficulties are pointed out and the implication of some interesting findings are discussed.