O202 Combining the strengths of passive functional mapping and electrical cortical stimulation

Abstract

Background The identification of eloquent cortex, surrounding the seizure onset zone, is important for predictable surgical outcome in epilepsy patients. The symptoms during electrical cortical stimulation (ECS) lead to a functional map that includes motor, sensory, and other functions. In this study we test whether a prevenient high-gamma mapping (HGM) with electrocorticography can guide ECS mapping and therefore optimizes it in terms of time and stimulation related risks. Methods Four patients underwent clinical ECS mapping and volunteered for an HGM session. The results enable an evaluation of the potential HGM contribution to the effectiveness of the ECS protocol. During HGM sessions, all patients performed hand movement, tongue movement, and listened to words. As a measure, the significance of guidance derives from a bootstrapping approach and indicates whether the HGM-guided ECS outperforms a random guidance. Additionally the potential reduction of required stimulations was calculated. Results On average, 52 electrode pairs were stimulated, where on average 18.8 electrodes relate to motor, sensory, or language-related functions. The number of required ECS stimulations could have been reduced to 31.3 electrodes on average (60.2%). Even with the reduced number of stimulations, all the electrodes that have originally been revealed, were identified. The HGM mapping significantly improves the ECS protocol for all four subjects (p Conclusions Compared to pure ECS, the proposed combined approach greatly reduces the required overall mapping time/effort as the HGM initially highlights the potential stimulation targets. We are encouraged that the presented system improves functional mapping in clinical practice.