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Case Reports
. 2025 Apr 19;17(4):e82563.
doi: 10.7759/cureus.82563. eCollection 2025 Apr.

Postoperative Improvement of Visual Function Following Amplitude Increase in Intraoperative Off-Response Visual Evoked Potential (VEP) Monitoring During a Skull Base Meningioma Surgery

Ming X Foo  1 , Ridzky F Hardian  2 , Kohei Kanaya  3 , Daishiro Abe  3 , Satoshi Kitamura  3 , Yutaro Sato  3 , Tomoya Shigehara  3 , Tetsuyoshi Horiuchi  3
Affiliations
Case Reports

Postoperative Improvement of Visual Function Following Amplitude Increase in Intraoperative Off-Response Visual Evoked Potential (VEP) Monitoring During a Skull Base Meningioma Surgery

Ming X Foo et al. Cureus. .

Abstract

Intraoperative visual evoked potential (VEP) monitoring does not generally predict improvement of postoperative visual function when there is an increase in the amplitude compared to the baseline recording. However, with a novel VEP monitoring method called "off-response" VEP, postoperative improvement of visual function was documented following an increase in the VEP amplitude during a skull base meningioma surgery. The authors present a case of a patient who was diagnosed with a skull base meningioma and underwent a left frontotemporal craniotomy. The patient initially presented with a decreased visual acuity in the right eye. The best-corrected visual acuity in the right eye was 0.1 on the Landolt C chart, approximately equivalent to 20/200 on the Snellen visual acuity chart. Both off-response and conventional VEP monitoring were performed on the right eye during the surgery because the left eye was already blind. Following tumor resection, the off-response VEP recording in the right eye showed a 40% increase in amplitude, while the conventional VEP remained unchanged. The patient's visual acuity in the right eye significantly improved after surgery. We report a case of postoperative improvement of visual function preceded by an amplitude increase in intraoperative off-response VEP, despite unchanged conventional VEP recording during a skull base meningioma surgery. Off-response VEP is effective in monitoring visual function intraoperatively and may be highly sensitive compared to the conventional flash VEP.

Keywords: improvement; intraoperative monitoring; off-response; visual evoked potential (vep); visual function.

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Conflict of interest statement

Human subjects: Consent for treatment and open access publication was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1. Pre and postoperative contrast-enhanced T1-weighted images
Preoperative axial (A), coronal (B), and sagittal (C) sections of contrast-enhanced T1-weighted images revealed a skull base tumor extending to the suprasellar region. Postoperative axial (D), coronal (E), and sagittal (F) sections of contrast-enhanced T1-weighted images showed partial removal of the tumor around the optic nerves.
Figure 2
Figure 2. Waterfall display of intraoperative right VEP monitoring with on-response (left) and off-response (right) monitoring from the start of the surgery (baseline recording) until after the tumor removal.
Off-response VEP monitoring (arrowheads) detected a 40% improvement in amplitude (from 2.8 μV to 4.0 μV) with latencies of approximately 70 ms during the tumor removal procedure around the right optic nerve, while the on-response VEP (flash VEP) monitoring (arrows) was unchanged throughout the procedure. VEP: Visual evoked potential
See this image and copyright information in PMC

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