Does Intracanalicular Involvement Affect Presentation and Outcomes in Vestibular Schwannoma?

Objective: Prior studies have identified a subset of vestibular schwannomas (VSs) without involvement of the internal auditory canal (IAC) that may affect tumor behavior. This study seeks to identify the influence of intracanalicular involvement. Methods: Patients with sporadic, medium-to-large VS treated via microsurgery were retrospectively identified and evaluated. Patients were grouped into a medial and lateral VS group and matched in a 1:1 fashion based on age and tumor size. Clinical outcomes were compared. Results: Fourteen patients with medial VS (mean age 49 years [standard deviation (SD) 10.5], mean tumor size 22.2 mm [SD 4.6]) were matched to 14 patients with lateral VS (mean age 47 years [SD 13.3], mean tumor size 20.8 mm [SD 6.3]), with 7 patients (50%) in each group undergoing a translabyrinthine and retrosigmoid approach, respectively. There were no significant differences observed in the symptoms at presentation, including facial numbness (0.14 vs. 0.21, p=0.56), as well as the extent of resection between groups (p=0.26). Similarly, comparing the medial and lateral VS groups, there was no significant difference between House-Brackmann grade in the immediate postoperative period (median 2 [IQR 1-3] versus 2 [IQR 1-3], p=0.52) and at most recent evaluation (median 1 [IQR 1-2] versus 1 [IQR 1-1], p=0.62). Conclusions: The presence of a medial VS may not substantially impact presentation or clinical outcomes, likely reflecting the influence of tumor size as well as current operative skill. These data also contrast with prior studies that identify a medial VS subtype that portends worse outcomes.