Concordance rate between Wada and fMRI tests for visual memory assessment of patients with medically intractable temporal lobe epilepsy

Abstract

Background: There is not enough evidence to prove either invasive Wada or non-invasive fMRI test predicts postoperative memory changes more accurately in patients with refractory temporal lobe epilepsy (TLE). In this study, concordance between fMRI and Wada test for postoperative assessment of visual memory is investigated. Methods: fMRI test with a novel scene-encoding task were conducted on our cohort of patients. fMRI laterality indices (LI) were then defined as a ratio (L-R)/(L+R) between the number of activated voxels in the left and right of two regions: hippocampus+parahippocampus (Region A) and temporal lobe - (hippocampus+parahippocampus) (Region B). fMRI results were divided into the right (LI < -0.2), left (LI > 0.2) or bilateral (-0.2 < LI <0.2) hemispheric memory dominance and compared to the results of the Wada test. Results: 19 patients were studied (14 left TLE, 3 right TLE and 2 bilateral TLE). The concordance rate between Wada and fMRI tests was 36.8% and 42.1% for regions A and B. Conclusions: Based on the results, the concordance rate between the Wada test and the fMRI test is not high. As a future work, we will investigate the correlation of each test to postoperative memory outcome.