Implications of Vestibular Schwannoma Consistency: Analysis of 140 Cases Regarding Radiologic and Clinical Features.

OBJECTIVE: To evaluate the effects of vestibular schwannoma (VS) consistency on internal auditory canal (IAC) widening, magnetic resonance imaging 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 at the Department of Neurosurgery, Tuebingen University, Germany. Operative videos were analyzed, and the tumors were classified into soft and firm according to resectability with an ultrasonic aspirator at 40% power. IAC opening was measured in preoperative bone-window computed tomography on the pathologic and healthy sides, and the percentage of widening between both sides was calculated. Tumor signal intensity was assessed on T2-weighted magnetic resonance imaging 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%). 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). The mean widening of the IAC in relation to the healthy side was 1.9 mm in soft tumors and 3.6 mm in firm tumors. A significant correlation was found between tumor consistency and degree of widening of the IAC (P < 0.0001). No significant correlation was found between tumor intensity (on T2-weighted imaging) 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 VS has an impact on the immediate postoperative outcome. Widening on bony computed tomography scan, but not T2 intensity on magnetic resonance imaging, predicts whether the tumor is soft or firm.