Electrical stimulation mapping of the visual cortex for epilepsy surgery

Limiting the post-operative sensory, motor, and cognitive deficits is a primary goal in epilepsy surgery, for which direct electrical stimulation (ES) remains an essential tool. However, the value of ES to predict potential deficits of visual functions, especially in cases of focal posterior epilepsy, remains unclear. In this review, we will summarize ES findings in the visual cortex, assess its predictive value for visual functions and propose recommendations to improve this value. We will examine the value of ES in the primary visual cortex, as well as in the ventral and dorsal streams. In the ventral stream, we will focus on face recognition and reading functions given their high social consequences if altered. Current evidence suggests that ES has limited utility in predicting potential visual field defects, except in the primary visual cortex. ES may help to predict face recognition and reading deficits, but the literature still lacks prospective data and group studies. For these two main functions, well-designed tasks should be used accurately to detect critical regions. Face recognition tasks should be more systematically used especially when targeting the right occipito-temporal cortex, since this function occupies a large cortical territory with severe recognition deficits if damaged. We advocate for more systematic use of ES in the visual cortex, using well-designed tasks depending on the targeted visual functions, as well as a more systematic evaluation of their predictive value, ideally through prospective group studies.