Abstracts

RATIONALE: While the Wada procedure has predominantly been used to determine language dominance in epilepsy surgery candidates, the addition of memory testing during the procedure can help assess memory function of each hemisphere in isolation and may assist in the identification of those at greatest risk for post-surgical amnesia. However, there is no univerally accepted paradigm, and the effects of number of test items, types of stimuli and different recall procedures are unknown. METHODS: A sample of 66 lateralized epilepsy patients underwent the Wada procedure as part of a pre-surgical work-up. 21 were administered a 9-item version consisting of 3 nursery rhymes, 3 words, and 3 pictures followed by forced choice recognition testing. The remaining 45 were given a 16-item version consisting of 8 words and 8 pictures followed by recognition testing with 7 foils. Wada memory results were considered lateralized if there was a greater than 20% discrepancy between dominant and nondominant hemisphere injections. Percent agreement with side of recommended surgery as concluded by a multi-disciplinary surgery team was calculated for each Wada test. RESULTS: Results from the 9-item Wada test agreed with the recommended side of surgery in only 29% (6/21)of cases, while the 16-item test demonstrated a 51% (23/45) agreement rate. Both the 9- and 16-item tests corresponded with the surgery team's recommendation at a higher rate for those patients classified as having a nondominant (50% & 84%, respectively) versus dominant (9% & 27%, respectively) hemisphere seizure focus. CONCLUSIONS: These results illustrate the potential impact of Wada test features (e.g., item composition, test length, number of foils) on identification of lateralized memory function. Given the different correspondence rates across patients with dominant and nondominant seizure lateralization, differential scoring criteria depending on seizure focus could be a consideration . The higher agreement rate using the 16-item test suggests that using a greater number of items and foils may enhance the accuracy of Wada memory testing. Such findings provide further support for development of a standardized Wada memory test.