Prognostic Significance of Peritumoral Edema in Patients With Vestibular Schwannomas.

Background: Peritumoral edema (PTE) in skull base meningiomas correlates to the absence of an arachnoid plane and difference in outcome. In vestibular schwannomas (VS), PTE and its significance for microsurgery and outcome have never been systematically evaluated.

Objective: To evaluate whether PTE correlates with tumor characteristics, the presence of an arachnoid plane, and outcome.

Methods: A retrospective study of the institutional database. PTE was evaluated on fluid-attenuated inversion recovery magnetic resonance images. Preoperative patient data and intraoperative tumor features (presence of tumor pseudocapsule, vascularity, degree of adhesion/invasion of the arachnoid) were noted. Outcome measures were completeness of removal, neurological outcome, and complication rate. These parameters in patients with PTE (group A) were correlated to those in matched series without edema (group B).

Results: Thirty patients presented with PTE (5%). The mean VS size was 3.4 cm. No major differences in the degree of adhesion or presence of an arachnoid plane were found. VS with PTE were more frequently hypervascular (26.7% in group A vs 6.7% in group B). The presence of PTE in VS was not related to surgical radicality. VS with PTE had worse early postoperative facial nerve function, but at 12 months, there was no major difference. VS with PTE were prone to cause postoperative hemorrhages in the tumor bed.

Conclusion: PTE in VS does not correlate with the degree of tumor adhesion and the presence of an arachnoid dissection plane. The radicality of tumor removal and long-term functional outcome in patients with and without PTE was similar. VS with PTE are more vascular and prone to cause postoperative hemorrhages. Therefore, meticulous hemostasis is advisable.