Intraoperative monitoring of cortical visual evoked potentials in resection of tumors near the optic radiation

Resection of tumors near the optic radiation carries a high risk of homonymous hemianopia. Intraoperative monitoring of cortical visual evoked potentials (cVEP) was proposed to preserve visual function. Objective. To evaluate clinical efficacy of cVEP monitoring during resection of tumors in occipital, parietal and temporal lobes. Material and methods. The study included 20 patients who underwent tumor resection with cVEP monitoring. All patients underwent pre- and postoperative automated static perimetry and MR tractography. We assessed spatial relationships between tumor and optic radiation including volumetric and fractional anisotropy analyses. Results. Stable cVEP during tumor resection (n=4, 20%) correlated with normal visual fields or minimal deficits. cVEP amplitude reduction (n=6, 30%) increased the risk of postoperative visual impairment, while unstable recordings with signal dropout (n=3, 15%) led to persistent hemianopia. Intraoperative cVEP improvement (n=2, 10%) predicted favorable outcomes (stable visual fields in one case and reduction of visual field defect after surgery in another one). Conclusion. cVEP monitoring provides intraoperative assessment of optic radiation integrity and accurately predicts postoperative visual outcomes in most cases. This technique enables real-time surgical strategy adjustments to optimize postoperative outcomes.