P.141 The value of using flash visual evoked potentials monitoring during minimally invasive endoscopic meningioma resection: a retrospective chart review

Background: Endoscopic endonasal surgeries performed in areas involving the visual pathway are associated with postoperative visual dysfunction. We previously demonstrated that continued eye monitoring during surgery by flash visual evoked potential (FVEP) represents a good method to prevent/reduce visual deficit post-surgery. We wondered whether FVEP monitoring may be more beneficial in patients with meningioma, strongly associated with postoperative visual loss. The aim was to explore the visual capacity in patients subjected to meningioma resection at The Ottawa Hospital. Methods: A retrospective chart review of patients who underwent minimally invasive endoscopic skull base surgery and FVEP monitoring for meningioma resection (July 2018 to present) was conducted. Only patients with available pre- (up to 3 months) and post-surgery (1-9 months) visual evaluation were analyzed. Results: 40 eyes were included (20 patients). The median age was 61 years (range:43-84) and 90% of patients were female. The LogMAR visual acuity was not significantly modified post-surgery (from +0.25 to +0.21; p=0.7 ). Color vision (# errors reading Ishihara/16-plates) was not modified post-surgery (from 2.6 to 3.2; p=0.6 ). Visual field (Humphrey, 32-2) was not significantly modified post-surgery (from 78.1% to 81.9%; p=0.7 ). Conclusions: The prevention of visual pathway injury during surgery by FVEP monitoring prevents visual deficits after endoscopic meningioma resection.