Assessment of memory lateralization by posterior cerebral artery selective anesthesia and postoperative verbal memory...

The Wada test, an intracarotid amobarbital procedure, is the gold standard for preoperative evaluation of postoperative memory decline in patients with drug-resistant epilepsy. However, it has certain limitations including false negatives due to insufficient hippocampal inhibition and false positives due to extrahippocampal disorders such as aphasia. This study examined the utility of posterior cerebral artery (PCA) selective anesthesia for functional evaluation (SAFE) as an alternative approach to avoid aphasia and assessed its predictive value for postoperative verbal memory decline.

The authors conducted a single-center retrospective study of patients with drug-resistant epilepsy between May 2018 and December 2023, who subsequently underwent PCA SAFE before anterior temporal lobe resection. The SAFE protocol includes comparable memory tasks before and immediately after anesthetic infusion. Preinfusion assessments established baseline memory function, whereas postinfusion assessments evaluated brain function under selective anesthesia. Patients were required to memorize 8 words, 8 pictures, and 5 figures. After the anesthetic effects subsided, recognition tasks were performed for all presented stimuli. The memory score was calculated by subtracting the number of recognized items encoded under anesthesia from the baseline. Word recognition represented verbal memory, whereas figure recognition represented visual memory. A memory score ≥ 2 points on the side of the epileptic focus or no difference between left and right PCA SAFE was classified as a high risk of postoperative memory decline. A decline of ≥ 15 points in postoperative memory scores on the Wechsler Memory Scale-Revised was defined as significant memory decline.

The authors included 11 patients (focus side: left in 8 patients and right in 3 patients). Five patients were classified as having a high risk and 6 as having a low risk for verbal memory decline. All 5 high-risk patients revealed significant postoperative verbal memory decline, whereas 5 of the 6 low-risk patients did not. The sensitivity was 83.3%, and the specificity was 100%. No patients had a significant decline in postoperative visual memory.

PCA SAFE was shown to predict postoperative verbal memory decline with high accuracy. This study highlights the utility of PCA SAFE in reducing aphasic interference in verbal memory, leading to a more accurate evaluation of surgical candidacy in patients with drug-resistant epilepsy.