Vasospasm of the internal auditory artery: significance in cerebellopontine angle surgery.

Background: Cochlear ischemia is likely involved in sensorineural hearing loss after cerebellopontine angle (CPA) surgery.

Objective: To demonstrate the type of vascular damage to the cochlea, apart from arterial section, that can be induced by CPA surgery.

Methods: The effects on measures of both cochlear blood flow (CBF) and distortion-product otoacoustic emissions (DPOAEs) of partial or total mechanical compressions of the internal auditory artery (IAA) were compared in young adult rabbits.

Results: When preocclusion baseline activity was compared with postocclusion CBF and DPOAEs, it was clear in the majority of cases that total compressions lasting < or =7 minutes produced the same full recoveries for both measures as did the shorter obstructions of only a few minutes. By contrast, both short and long partial occlusions in which ischemia was interrupted by periods of poor reperfusion (<50% of the initial CBF value) resulted in delayed and prolonged recoveries. In addition, at times, full recovery was not achieved, particularly for DPOAEs, because of vasospasm-like 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 hearing preservation is attempted in CPA surgery.