Effects of anterior inferior cerebellar artery occlusion on cochlear blood flow--a comparison between laser-Doppler and microsphere methods.

The effects of anterior inferior cerebellar artery (AICA) occlusion on blood flow were investigated in rats using the laser-Doppler and microsphere methods. A specially designed microclamp was held in a micromanipulator and positioned to occlude the left AICA. After the middle ear mucosa had been removed, a 1.0-mm laser-Doppler probe was placed on the basal turn of the left cochlea. Non-radioactive microspheres were injected intracardially during the AICA occlusion and the numbers of microspheres in various parts of the cochlea were counted, including in the bone surrounding the cochlea. Upon AICA clamping, the blood flow measured by laser-Doppler flowmetry decreased to 46.9+/-11.9% of the baseline value, and the number of microspheres trapped in the cochlea was 17.2+/-13.3% compared with the contralateral side in 15 animals. The number of microspheres in the bone surrounding the cochlea in the AICA-clamped side was 81+/-15% of that of the contralateral side. In animals in which there were few if any microspheres in the cochlea, laser-Doppler output was 30-40% of the baseline value. From these findings, we infer that during complete interruption of cochlear blood flow in rats, residual laser-Doppler output was essentially attributable to blood flow in the bone surrounding the cochlea.