Incidence and clinical decision making for the Wada test over one decade: 1997-2007

Purpose. The objective of this study was to review the percentage of Wada tests performed on patients with intractable temporal lobe epilepsy undergoing surgery at a single epilepsy centre over the last decade, and to identify clinical features which are more likely associated with decision making in favour of Wada testing. Methods. We retrospectively reviewed all temporal lobe resections performed between 1997 and 2007 at the Cleveland Clinic Epilepsy Center. Results. A total of 410 Wada tests were conducted on 777 patients undergoing temporal lobectomy (TL). Left temporal resection was performed in 55% of cases. The most frequent pathological diagnoses were hippocampal sclerosis (42%) and non-specific gliosis (26%). Overall, Wada test frequency in patients undergoing presurgical evaluation decreased over time. In 1997, 47 of 58 (81%) TL patients underwent Wada testing compared to 11 of 76 (14.4%) in 2007. Patients with left temporal lobe epilepsy, and/or those referred for subdural electrode placement, were significantly more likely to undergo Wada testing. The most common types of surgery were anteromedial temporal resection with removal of mesial structures (59%) and temporal resection without mesial structure removal (32%). Patients with left temporal epilepsy and Wada testing were significantly more likely to undergo resection of mesial cortex. Discussion. Wada testing has declined over the last decade in this single centre study. Patients with left, likely dominant, temporal lobe epilepsy and those with subdural evaluations were more likely to undergo Wada testing. We speculate that the emergence of alternative noninvasive language lateralization techniques, along with concerns about the reliability of results and awareness of complication risks, are major reasons for the decline.