Long-term study after perforation of the round window. Animal experiments using electric response audiometry.

The round-window membrane of the inner ear of the guinea pig was perforated with a platinum wire under ketamine-xylazine anaesthesia. The latency times of waves I and V (Jewett) increased to 0.6 ms at 100 dB click HL stimulus loudness. The interpeak latencies did not change (4.0-4.2 ms). At 60 dB CHL stimulus loudness, no responses were discernible. Closure of the membrane damage by adhesive fibrin tissue had no effect on the auditory nerve potentials or the brain-stem responses. Normal latency times of waves I-V were seen 7 days after perforation. There was no difference between the animals with repaired and unrepaired membrane damage. We observed spontaneous healing of the round-window membrane 7 days after perforation, and a normal organ of Corti.