Experimentally induced round window membrane lesions.

This investigation confirmed previous studies indicating that the middle and inner ear of the guinea pig have a pronounced tendency to healing. Middle ear hemorrhage of surgical origin appears to stop quickly in the guinea pig. A surgically created perforation of the round window with or without removal of perilymphatic fluid by suction resulted in a spontaneous healing of the round window membrane in 12/13 animals. Perilymphatic hemorrhage, associated with short post-surgical interval was found in a substantial number of cases. The origin of the perilymphatic hemorrhage is doubtful. Degeneration of the organ of Corti was found in four ears in three animals and appeared to be correlated to the perilymphatic hemorrhage. Electrophysiological measurements appeared to correlate well with the anatomical findings for one animal with very small changes and for three animals with pronounced middle and inner ear pathology. In three additional animals less agreement was observed. In general these animals showed a more pronounced decrease of function than would be expected by the anatomy.