Changes in intracochlear and intracanalicular nerves after acoustic neurinoma excision confirmed by magnetic resonance imaging.

Abstract

Postoperative magnetic resonance imaging findings related to the vestibulocochlear and facial nerves within the internal auditory canal were analyzed in acoustic neurinomas. T1- and proton-weighted magnetic resonance images showed that the vestibulocochlear nerves distal to the internal auditory meatus increased in signal intensity after surgical intervention. These nerves were conspicuously enhanced after intravenous administration of gadolinium diethylene-triamine-pentaacetic acid. The preserved facial nerves were also markedly enhanced postoperatively. As a possible cause of these findings, we suggest operative disruption of the blood-nerve barrier with ensuing nerve edema, although the operative procedures were carefully carried out using a surgical microscope. The clinical significance of traumatic disruption of the blood-nerve barrier and subsequent nerve edema are discussed from the standpoint of preservation of cochlear nerve function.