Language Lateralization in temporal lobe epilepsy -- a behavioral screening tool for surgical planning

Introduction: Temporal lobe epilepsy (TLE) can affect eloquent areas, affecting language. We applied the Translingual Lexical Decision Task (TLDT), a tongue independent behavioral screening tool to measure language dominance in drug resistant TLE. Method: Patients with left TLE (LTLE) (n=26), right TLE (RTLE) (n=28) and Controls (n=30) were evaluated using TLDT. We performed two repeated measures ANOVAs for accuracy and response time, with Visual half-field as intra-subject factor (left visual-field, LVF; right visual-field, RVF), and Group as inter-subject factor (RTLE, LTLE, Controls). Result: A main effect of visual half-field was found, showing RVF (left hemisphere) advantage. A main effect of Group was found in accuracy, and pairwise comparisons showed that both patient groups performed less accurately compared to Controls, and LTLE performed significantly lower than RTLE. Also, the Group by Visual half-field interaction was significant. Post hoc t-tests indicated the Controls and RTLE performed better in RVF than in LVF whereas no visual half-field effect was found in LTLE. For response times, the interaction was also significant. Post hoc t-tests showed a significant RVF advantage for Controls only, which was present for RTLE when tested one-tailed. LTLE group did not show an RVF advantage. Conclusion: Overall, the results demonstrated that TLDT is a non-invasive method to investigate language lateralization in drug-resistant TLE patients, and can efficiently distinguish between LTLE and RTLE. Compared to RTLE and Controls, language lateralization is diminished in LTLE. The current findings highlight the potential use of TLDT as an effective presurgical language lateralization screening tool.