Selective Posterior Cerebral Artery Wada Better Predicts Good Memory and Naming Outcomes Following Selective Stereotactic Thermal Ablation for Medial Temporal Lobe Epilepsy Than Internal Carotid Artery Wada

Abstract

Epilepsy surgery has witnessed recent advancements in minimally invasive procedures, demanding precise evaluation methods for improved patient outcomes. The conventional intracarotid amobarbital (Wada) test, originally designed to assess memory function in temporal lobe epilepsy (TLE) patients, may inadequately predict memory outcomes of selective medial temporal lobe surgeries. This study compares two variations of the Wada test, the intracarotid artery (ICA) and posterior cerebral artery (PCA) approaches, aiming to determine their effectiveness in predicting memory outcomes, particularly after stereotactic laser amygdalohippocampotomy (SLAH). We retrospectively studied patients who underwent PCA Wada after first failing the ICA Wada as part of their epilepsy surgery evaluation. Memory assessments were conducted using standardized neuropsychological tests to assess pre- to post-surgical memory performance changes. Only one of thirteen patients failed the PCA Wada after failing the ICA Wada (p=0.003, two-sided binomial test with p0=0.5) demonstrating that these tests assess different brain regions or networks. PCA Wada had a high negative predictive value for the safety of SLAH, compared to ICA Wada, as none of the patients who underwent SLAH after passing the PCA Wada experienced catastrophic memory decline (0 of 9 subjects, p<.004, two-sided binomial test with p0=0.5), and all experienced a good cognitive outcome. In contrast, the single patient who received a left anterior temporal lobectomy after failed ICA and passed PCA Wada experienced a persistent, near catastrophic memory decline. On confrontation naming, few patients exhibited disturbance during the PCA Wada. Following surgery, SLAH patients showed no naming decline, while open resection patients, whose surgeries all included broader ipsilateral temporal lobe regions, experienced significant naming difficulties (Fisher's exact test, p=0.02). These findings demonstrate that PCA Wada is a more accurate tool for assessing hippocampal ablations, that the ICA Wada measures broader ipsilateral temporal lobe function, and that the hippocampal territory targeted by PCA Wada and SLAH is not contributing to language processing.