An Electrophysiological Study on the Effect of Laser Irradiation of Round Window Membrane in the Guinea Pig

Abstract

An argon laser beam was used to irradiate the round window in 17 guinea pigs. Each animal was examined electrophysiologically with an electrode placed on the round window (RW) membrane 3 or 30 days after the irradiation, after which the cochlea was examined morphologically. The RW membrane was found intact in 16 out of 17 animals. All potentials (SP, CM, CAP) were abolished in 8 of the 17 animals. Histologically, perforations of the basilar membrane and Reissner's membrane were observed in 7 of 8 cases. In 4 of the 17 cases, a small effect of irradiation was evident both physiologically and histologically. Significant elevation of thresholds was observed in the remaining 5 animals, where amplitudes of CM, +SP, and CAP decreased at all intensities. Varying degrees of membranous labyrinth destruction can be used without perforating the RW membrane by the present method.

Key Words:

• argon laser
• round window membrane
• cochlear microphonic
• compound action potetial
• guinea pig