Subcortical brain mapping strategies for intraoperative identification of the optic radiation during asleep and awake surgery: a scoping review.

Introduction: Postoperative visual deficits after glioma surgery may significantly reduce quality of life. Multiple techniques for intraoperative mapping of the optic radiation (OR) have been described, but no consensus exists regarding optimal strategies, particularly for novel neurophysiological recording techniques. Research question: We conducted a scoping review to systematically organize the existing paradigms for intraoperative OR mapping, distinguishing awake task-based approaches from evoked potential recording techniques, and to outline future directions for standardization. Material and methods: This scoping review was conducted following the PRISMA-ScR guidelines. Studies describing intraoperative mapping of the OR in any surgical setting were included. Stimulation and recording parameters, as well as intraoperative task paradigms, were extracted and synthesized. Results: Nineteen studies involving 212 patients were included: four reporting neurophysiological recording techniques, 14 describing awake mapping approaches, and one combining both. Three main technique categories were identified: subcortico-cortical evoked potentials (SCEP), subcortical recorded visual evoked potentials (sVEP), and awake task-based mapping. Discussion and conclusion: A modified picture-naming task during awake mapping, presenting two figures diagonally on a screen, has proven useful in estimating the OR boundary, allowing maximal safe resection while limiting postoperative deficits to an acceptable quadrantanopia in most low-grade glioma surgeries. Alternative awake paradigms show promise but require further validation. Intraoperative neurophysiological recording techniques are technically feasible, and their role could be relevant in the future, particularly for patients unsuitable for awake surgery. However, methodological standardization and clinical validation are needed.