Authors :
Presenting Author: Shin-ichiro Osawa, MD, PhD – Tohoku University Graduate School of Medicine
Kyoko Suzuki, MD, PhD – Tohoku University Graduate School of Medicine
Kazuo Kakinuma, MD, PhD – Tohoku University Graduate School of Medicine
Hana Kikuchi, PhD – Tohoku University Graduate School of Medicine
Kazushi Ukishiro, MD, PhD – Tohoku University Graduate School of Medicine
Makoto Ishida, PhD – Tohoku University Graduate School of Medicine
Kazuto Katsuse, MD, PhD – Tokyo University Hospital
Shoko Ota, PhD – Tohoku University Graduate School of Medicine
Kazutaka Jin, MD, PhD – Tohoku University Graduate School of Medicine
Hidenori Endo, MD, PhD – Tohoku University
Rationale:
The Wada test has traditionally been used to identify the dominant hemisphere for language and memory; however, its clinical application is declining due to limitations such as intraprocedural impaired awareness and anatomical variability in vascular distribution. To address these challenges, we developed Selective Anesthesia for Functional Evaluation (SAFE), combining super-selective propofol infusion into intracranial arteries with an optimized neurocognitive task battery. (Osawa S. Cortex. 2024; 176; 209-220., Kikuchi H. J Neurosurg. In press.) Here, we report a novel application of SAFE to obtain detailed functional risk information regarding hippocampectomy, a long-standing unresolved issue in the original Wada test. We hypothesized that SAFE could contribute to material-specific evaluation of memory function.
Methods:
This study included 28 patients with temporal lobe epilepsy selected from 72 consecutive SAFE cases, in whom hippocampectomy was under consideration (Figure 1). Bilateral posterior cerebral artery injections (SAFE-PCA) were performed to assess the risk of postoperative memory decline. The mean Wechsler Memory Scale-Revised verbal and visual memory scores were 91.3 ± 15.7 and 97.4 ± 14.4, respectively. Left hemisphere language dominance was confirmed in all cases by SAFE via the middle cerebral artery. During SAFE-PCA, 8 words, 8 pictures, and 5 meaningless figures were presented before and after infusion to assess baseline and anesthetic conditions. The number of recognized items (NoR) was evaluated after neurological recovery. A lower NoR during anesthesia indicated a greater functional contribution of the anesthetized hippocampus to memory.
Results:
NoR during SAFE-PCA for each material was as follows. Left P2 infusion resulted in significantly fewer recognized words (3.1 ± 2.2) compared to right P2 infusion (4.2 ± 1.8, p = 0.037), whereas right P2 infusion resulted in significantly fewer recognized figures (1.3 ± 1.2) compared to left P2 infusion (2.6 ± 1.4, p = 0.0007). No significant difference was observed for picture recognition between left (6.4 ± 2.0, p = 0.108) and right (5.5 ± 2.2) infusions (Figure 2). Baseline NoR showed no significant differences for any material.
Conclusions:
SAFE-PCA enabled material-specific evaluation of memory function. NoR of words reflected verbal memory, while NoR of meaningless figures reflected nonverbal memory. Picture memory likely involved dual encoding strategies, combining verbal and visual processes.
Funding:
This work was supported by Health Labor Sciences Research [grant nos. 23GB1003 and 24GC1003], Grant-in-Aid for Transformative Research Areas [grant no. 20H05956], Grant-in-Aid for Scientific Research (B) [grant no. 21H03779] to KS.