Vasospasm of the internal auditory artery: Significance in cerebellopontine angle surgery

Background: Cochlear ischemia is likely involved in sensorineural hearing l oss after cerebellopontine angle (CPR) surgery. Objective: To demonstrate the type of vascular damage to the cochlea, apart from arterial section, that can he induced by CPA surgery. Methods: The effects on measures of both cochlear blood flow (CBF) and dist ortion-product otoacoustic emissions (DPOAEs) of partial or total mechanica l compressions of the internal auditory artery (IAA) were compared in young adult rabbits. Results: When preocclusion baseline activity was compared with postocclusio n CBF and DPOAEs, it was clear in the majority of cases that total compress ions lasting less than or equal to 7 minutes produced the same full recover ies for birth measures as did the shorter obstructions of only a few minute s. By contrast, both short and long partial occlusions in which ischemia wa s interrupted by periods of poor reperfusion (<50% of the initial CBF value ) resulted in delayed and prolonged recoveries. Ln addition, at rimes, full recovery was not achieved, particularly for DPOAEs, because of vasospasm-l ike activity. Conclusion: Vasospasm of the IAA was induced by a systematic series of IAA compressions and releases that did not provide for full reperfusion. These data support the concept that vasospasm should be prevented whenever hearin g preservation is attempted in CPA surgery.