Abstracts

Rationale: In the early 1990s, most epilepsy centers performed Wada tests in almost all patients during workup for epilepsy surgery. The decision making process for Wada testing has changed, and the frequency of Wada testing has declined since. The objective of this study was to review the percentage of Wada tests performed in patients with intractable temporal lobe epilepsy at a single epilepsy center over the last decade, and to identify clinical features that are more likely associated with decision making in favor of Wada tests. Methods: We reviewed all temporal lobe surgeries performed between 1997 and 2007 at Cleveland Clinic. Data including age, side of surgery, etiology of epilepsy, placement of invasive recordings as well as Wada testing were reviewed. Statistical analysis was completed variables and the chi-square test to evaluate dichotomous variables. Results: A total of 408 Wada tests were conducted in 777 (52.8%) patients undergoing temporal lobectomy (TL) utilizing SAS statistical software. T-test was used to evaluate continuous. 420 TL were left sided (54%). The average patient age at presurgical assessment was 31.7 years (median 31, range: 1-73 years). Pathologies included mesial temporal sclerosis (n=322, 41.2%), malformation of cortical development (78, 10%), gliosis (198, 25.5%), tumors (111,14.3%), vascular malformations (29, 3.7%), and stroke (21, 2.7%). Pathology was normal in 2 (0.2%) patients. Pathology results were not available in 16 patients (2%). Overall, Wada test frequency in patients undergoing presurgical evaluation decreased over time as calculated based on percentage of Wada tests per number of temporal lobectomies each year. In 1997, 47 of 58 (81%) TL patients underwent Wada testing. In 2007 only 11/76 patients (14%) underwent Wada testing. A total of 233 of 420 left TL were screened with a Wada test (55.4%) as compared to 157 of 357 right TL (43.9%). In 1997 all right TL and 25/30 (83.3%) of left TL had Wada tests. In 2007 8/40 (20%) of left TL and 3/36 (8%) of right TL underwent a Wada test. Patients with left temporal lobe epilepsy (χ= 5.31, p= 0.02) and those who went on to undergo subdural electrode placement (χ= 6.64, p= 0.01) were more likely to be subjected to Wada testing. Patients with depth electrode placement were not more likely to have a Wada study (χ= 2.17,p= 0.14). Age was non-significant in determining Wada testing (mean age: 30.78 yrs (95% CI: 29.4-32.1 yrs) for patients with Wada; mean age: 31.57 (95% CI: 29.9-33.2 yrs) for patients without Wada; p=0.46). Conclusions: Wada testing declined over the last decade in this single center study. Patients with left, likely dominant, temporal lobe epilepsy and with planned subdural evaluations were more likely to undergo Wada testing. We speculate that increased awareness and availability of alternative language lateralization techniques (Epilepsia. 2007;48:442-455), concerns about the reliability of results (Epilepsia. 2007;48:553-558) as well as awareness of complications (Epilepsy Behav. 2008;13:551-553) may have played a role in the evolution of this decision making process.