Protecting vision with intraoperative visual evoked potentials and tractography in transcortical brain tumor surgery.

Objective: Intraoperative neuromonitoring (IONM) is nowadays a gold standard during brain tumor resections, but visual function mapping is less frequently performed in clinical practice. This article aims to report two transcortical brain tumor surgery cases affecting optic radiation, where the application of intraoperative visual evoked potentials (VEP) combined with tractography was beneficial to protect the patients' vision. Methods: Two patients with brain tumors compressing the left posterior visual pathways underwent surgery under general anesthesia using IONM and VEP with neurologic improvement and preservation of vision. Results: VEP is beneficial in the surgery of intra-axial lesions affecting the posterior visual pathways (optic radiation, visual cortex) and parasellar lesions involving the anterior visual pathways (chiasm). They can also be effectively combined with other mapping methods such as tractography. Conclusions: According to our experience, IONM with VEPs and neuronavigation with tractography protect visual function in transcortical approaches to resecting tumors near the optic radiation and should be considered a standard monitoring method for such operations.