Objective: To evaluate the effects of vestibular schwannoma (VS) consistency on internal auditory canal (IAC) widening, MRI-appearance, presenting symptoms and facial nerve outcome.
Material and methods: We performed a retrospective analysis of 140 consecutive patients presenting with unilateral VS who underwent surgical treatment in our Department. Operative videos were analyzed, and the tumors were classified into soft and firm according to the resectability with the ultrasonic aspirator at 40% power. IAC opening was measured in preoperative bone-window CT on the pathologic and on the healthy side and the percentage of widening between both sides was calculated. Tumor signal intensity was assessed on T2WI MRI scans. Preoperative and postoperative findings in the patient reports were documented.
Results: Widening of the IAC due to presence of the VS occurred in 118 patients (84.3%). Tumor consistency was soft in 91 cases (65%) and firm in 49 cases (35%). The degree of IAC widening on the tumor side compared to the other side ranged from 0.1 to 10.1 mm (mean 2.6 mm). A significant correlation was found between tumor consistency and degree of widening of the IAC (P value < 0.0001). No significant correlation was found between tumor intensity (on T2WI) and tumor consistency. In the early postoperative course patients with soft tumors had better facial nerve function than those having firm tumors. However at the last examination no difference between both groups was found.
Conclusion: The consistency of vestibular schwannoma has impact on the immediate postoperative outcome. Widening on bony CT scan, but not T2-intensity on MRI predict if the tumor is soft or firm.
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