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.

Medtronic, Inc. has contributed research funding to Emory University during the past that was not directly related to this project. Medtronic, Inc. develops products related to the research described in the paper. Drs. Gross and Willie serve as consultants to Medtronic, Inc. and receive compensation for these services. The terms of this arrangement have been reviewed and approved by Emory University and Washington University in Saint Louis in accordance with their respective conflict of interest policies. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

This work was in part supported by grant funding (R01 NS088748, K02 NS0709060) received by Dr. Daniel L. Drane from the National Institute of Neurological Disorders and Stroke (NINDS) of the National Institutes of Health (NIH). NPP was supported by CURE Epilepsy, and NINDS K08NS105929, and R21NS122011. Jon T. Willie is supported by R01MH120194 (NIMH) and P41EB018783 (NIBIB).

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