Non-Verbal Memory Decline is Greater Following Anterior Temporal Lobectomy Than Mesial Temporal Laser Ablation in Non-Dominant Temporal Lobe Epilepsy

INTRODUCTION: Although it has been shown for dominant temporal lobe epilepsy that stereotactic laser amygdalohippocampectomy (SLAH) results in less verbal memory decline than anterior temporal lobectomy (ATL), the relative cognitive effects of these surgeries in non-dominant temporal lobe epilepsy have not been directly studied. METHODS: A retrospective review of SLAH or ATL surgeries at the University of Washington from 2014 to 2020 was conducted. Hemisphere dominance was determined using WADA testing or functional MRI. Patients that received non-dominant SLAH or ATL and pre- and post-operative neuropsychological testing were analyzed. A composite non-verbal visuospatial memory variable was created using Z-score normalization of the Visual Reproduction (VR) and Rey Complex Figure Test (RCFT) tasks. The Rey Auditory Verbal Learning Test (RAVLT) was used for verbal memory analysis. Paired t-test analysis was used to compare cognitive score distributions. Two-way ANOVA was used to assess the effects of seizure freedom (Engel score 1) and surgical intervention factors on cognitive improvement. RESULTS: Pre- and post-operative neuropsychological testing was available for 26 patients (14 SLAH, 12 ATL). Non-verbal visuospatial memory significantly decreased after ATL (mean -0.18 to -0.82, p = 0.025, n = 11) but not after SLAH (mean -0.55 to -0.57, p = 0.96, n = 14). There were no observed changes in verbal memory after ATL (mean -0.41 to -0.07, p = 0.22, n = 11) or SLAH (mean -0.13 to 0.-42, p = 0.26, n = 13). Seizure freedom was a significant factor in explaining non-verbal memory improvement, even when modeled with surgical intervention interaction term (ANOVA, p = 0.04). CONCLUSIONS: Patients undergoing non-dominant ATL experience a greater reduction in visuospatial memory metrics compared to patients undergoing SLAH. Independent of surgery type, seizure freedom is associated with improved non-verbal memory outcome.