This study aimed to assess long-term progression of residual tumor and facial function after primary partial resection of large vestibular schwannoma.

This retrospective study was performed in a tertiary reference center between January 2008 and December 2021. Patients with vestibular schwannoma exceeding 25mm on the long axis underwent partial tumor resection, leaving a residual fragment, and were followed up for at least 3 years. The residue was confirmed on MRI at 6 months. Facial grade was assessed on the House-Brackmann classification at the immediate postoperative time-point and at 1 year.

Fifty-seven patients were included: 10 (17%) showed tumor regrowth, at a mean 53±25.5 months. Forty (70%) showed facial grades≤III at the immediate postoperative time, and 51 (89%) at 1 year. Mean residual tumor size was 13.6±7.2mm in patients with regrowth and 7.4±5mm in those without (P<0.01). On multivariate analysis, only residual tumor size was significantly associated with regrowth (OR=1.263; 95% CI [1.050–1.677]; P=0.04). ROC analysis identified a 6.5mm threshold for residual tumor size, beyond which risk of regrowth increased, with 90% sensitivity, 53% specificity and 0.78 AUC.

Partial resection of large vestibular schwannoma provided satisfactory control and only mild postoperative facial palsy. Small residual tumor size was the main factor for success.