Focal Cortical Surface Cooling is a Novel and Safe Method for Intraoperative Functional Brain Mapping.

Objective: Electric cortical stimulation (ECS) has been the gold standard for intraoperative functional mapping in neurosurgery, yet it carries the risk of induced seizures. We assess the safety of focal cortical cooling (CC) as a potential alternative to ECS.

Methods: We reviewed 40 patients (13 with tumor and 27 with mesial temporal lobe epilepsy) who underwent intraoperative CC at the University of Iowa Hospital and Clinics (CC group), of whom 38 underwent ECS preceding CC. Intraoperative and postoperative seizure incidence, postoperative neurologic deficits, and new postoperative radiographic findings were collected to assess CC safety. Fifty-five patients who underwent ECS mapping without CC (ECS-alone group) were reviewed as a control cohort. Another 25 patients who underwent anterior temporal lobectomy (ATL) without CC or ECS (no ECS/no CC-ATL group) were also reviewed to evaluate long-term effects of CC.

Results: Seventy-nine brain sites in the CC group were cooled, comprising inferior frontal gyrus (44%), precentral gyrus (39%), postcentral gyrus (6%), subcentral gyrus (4%), and superior temporal gyrus (6%). The incidence of intraoperative seizure(s) was 0% (CC group) and 3.6% (ECS-alone group). The incidence of seizure(s) within the first postoperative week did not significantly differ among CC (7.9%), ECS-alone (9.0%), and no ECS/no CC-ATL groups (12%). There was no significant difference in the incidence of postoperative radiographic change between CC (7.5%) and ECS-alone groups (5.5%). Long-term seizure outcome (Engel I+II) for mesial temporal epilepsy did not differ among CC (80%), ECS-alone (83.3%), and no ECS/no CC-ATL groups (83.3%).

Conclusions: CC when used as an intraoperative mapping technique is safe and may complement ECS.