Laser irradiation of the guinea pig basilar membrane.

Abstract

The cochlea is the part of the inner ear that transduces sound waves into neural signals. The basilar membrane, a connective tissue sheet within the cochlea, is tonotopically tuned based on the spatial variation of its mass, stiffness, and damping. These biophysical properties are mainly defined by its constituent collagen fibers. We sought to assess the effect of laser irradiation on collagen within the basilar membrane using histological analysis. Four excised guinea pig cochleae were stained with trypan blue. From these, two were irradiated with a 600 nm pulsed dye laser and two were used as controls. Collagen organization was visualized using polarization microscopy. Laser irradiation reduced the birefringence within the basilar membrane as well as within other stained collagen-containing structures. Larger reductions in birefringence were measured when more laser pulses were given. The effects were similar across all turns of each cochlea. Laser irradiation causes immediate alterations in collagen organization within the cochlea that can be visualized with polarization microscopy. These alterations may affect cochlear tuning. Ongoing research is aimed at analyzing the effect of laser irradiation on cochlear function. It is conceivable that this technique may have therapeutic benefits for patients with high-frequency sensorineural hearing loss.