Comparison of Surgeons' Assessment of the Extent of Vestibular Schwannoma Resection with Immediate Post Operative and Follow-Up Volumetric MRI Analysis

Abstract

(1) Background: Incomplete excision of vestibular schwannomas (VSs) is sometimes preferable for facial nerve preservation. On the other hand, subtotal resection may be associated with higher tumor recurrence. We evaluated the correlation between intra-operative assessment of residual tumor and early and follow-up imaging. (2) Methods: The charts of all patients undergoing primary surgery for sporadic vestibular schwannoma during the study period were retrospectively reviewed. Data regarding surgeons' assessments of the extent of resection, and the residual size of the tumor on post-operative day (POD) one and follow-up MRI were extracted. (3) Results: Of 109 vestibular schwannomas meeting inclusion criteria, gross-total resection (GTR) was achieved in eighty-four, near-total (NTR) and sub-total resection (STR) in twenty-two and three patients, respectively. On follow up imaging, volumetric analysis revealed that of twenty-two NTRs, eight were radiographic GTR and nine were radiographic STR (mean volume ratio 11.9%), while five remained NTR (mean volume ratio 1.8%). Of the three STRs, two were radiographic GTR while one remained STR. Therefore, of eighteen patients with available later follow up MRIs, radiographic classification of the degree of resection changed in six. (4) Conclusions: An early MRI (POD#1) establishes a baseline for the residual tumor that may be more accurate than the surgeon's intraoperative assessment and may provide a beneficial point of comparison for long-term surveillance.

Keywords: gross total resection; magnetic resonance imaging; near-total resection; residual tumor; subtotal resection; vestibular schwannoma.

Figure 1

Pre-operative MRI (top panel) shows right sided vestibular schwannoma that was resected (bottom panel) using a translabyrinthine approach. While this was assessed as a near-total resection, post-operative volumetric analysis classified the residual as subtotal resection (7.9% of original tumor volume).

Figure 2

Post-operative MRIs at day 1 (top), 3 months (middle), and 15 months (bottom) after NTR of a right sided vestibular schwannoma. The intra-operative residual estimate was 1 mm. The immediate MRI was a radiographic GTR, but the delayed MRIs were radiographic NTR with stable appearance of the area of enhancement.