Abstracts

RATIONALE: There has been little formal evaluation of the relative contribution of the Wada compared with standard neuropsychology in pre-surgical investigations. We present the initial results of a comparison of these procedures in lateralising the epileptogenic focus in a group of patients with temporal lobe epilepsy (TLE). METHODS: Subjects were 29 left language dominant TLE patients (13 left; 16 right) who had undergone consecutive bilateral Wada procedures and standard neuropsychological testing during pre-surgical evaluation. Wada and neuropsychological memory scores (including Wechsler verbal and visual memory indexes and specific measures of verbal and non-verbal learning and retention) were analysed using group mean comparisons, group proportions and Pearson correlations. RESULTS: Wada memory scores were significantly different for Left TLE (WadaLeft = 48.6%; WadaRight = 80.8%) compared with Right TLE (WadaLeft = 82.1%; WadaRight = 37.1%) groups. Between hemisphere difference scores were in the expected direction (based on seizure focus) in the majority of patients (96%), with a difference of greater than 20% observed in 82% of cases. Neuropsychological memory scores were not significantly different in Left versus Right TLE groups. Furthermore, there were no significant correlations between Wada and neuropsychological memory scores. CONCLUSIONS: The lack of difference between left and right TLE groups on neuropsychological memory tests may be explained by large within-group variance. By contrast, clear and reliable differences were found for Wada memory scores. These findings support the hypothesis that the Wada and standard neuropsychological tests measure memory differently, and provide a unique contribution in pre-surgical epilepsy evaluations.