Visual Memory Outcomes Following Stereotactic Laser Amygdalohippocampotomy for Temporal Lobe Epilepsy Open Access

Abstract

Stereotactic laser amygdalohippocampotomy (SLAH) is a minimally invasive procedure for temporal lobe epilepsy that preserves more neural tissue than open procedures such as anterior temporal lobectomy (ATL). Cognitive decline is a concern for patients undergoing epilepsy surgery, and understanding the cognitive risks with procedures is crucial. However, trends in visual memory outcomes following SLAH and ATL remain inconclusive. The hippocampus is a key structure for memory, and prior research has demonstrated that visual memory is often lateralized to the right cerebral hemisphere. This paper examines how hippocampal ablation via SLAH impacts visual memory, focusing on changes in Wechsler Memory Scale Visual Reproduction Third and Fourth Edition (WMS VR) T-scores pre- and post-operatively. Preoperative hippocampal volumes were extracted from magnetic resonance imaging (MRI). A total of 77 patients were included, of whom 39 underwent right SLAH and 38 underwent left SLAH. Associations between VR score changes and demographic and epilepsy-related variables were explored, although no strong relationships were found. Paired t-test analyses of neuropsychological test T-scores showed that overall VR delayed recall (DR) scores significantly improved post-operatively (p = 0.0038). Among patients who underwent right SLAH, VR DR scores significantly improved (p = 0.0050), whereas no significant change was observed among patients who underwent left SLAH (p = 0.17). Analyses using a ±1 standard deviation of DR difference cutoff indicated that 23% of patients demonstrated meaningful improvement in visual memory and 5% showed decline, with similar rates observed between left and right SLAH groups. Linear regression models predicting DR difference with volumetric asymmetry, epilepsy duration, and surgery side were examined but were not found to be significant. Given the analysis, it is possible that postoperative visual memory outcomes are more favorable than traditionally expected. These findings suggest potential neural plasticity following SLAH and raise questions about the sensitivity of the VR to hippocampal dependent aspects of visual memory, as well as the possible use of compensatory verbal strategies. These results also suggest that one may only need a single healthy hippocampus, and that white matter pathways and other structures unaffected by SLAH may play a vital role as well.

Table of Contents

Introduction............................................................................................................1

Visual Memory Networks................................................................................2

Expected Hippocampal Contribution to Visual Memory Across Species.............. 3

Visual Memory Outcomes Following TLE Surgical Interventions....................... 6

Hypothesis.....................................................................................................8

Methods.................................................................................................................9

Results.................................................................................................................. 11

Sample Characteristics and Associations with Delayed Recall Change...............11

Paired T-test Analysis for The Whole Sample..................................................14

Paired T-test Analysis for Left and Right Subgroups........................................ 15

Paired T-test Analysis Examining the RCFT.....................................................17

Standard Deviation Cutoff Analysis................................................................ 18

Linear Regression Model Analysis...................................................................20

Discussion............................................................................................................. 26

References..............................................................................................................32

About this Honors Thesis

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School	Emory College
Department	Data and Decision Sciences
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Biology, Neuroscience
Keyword	Visual Memory Hippocampus Nonverbal Memory Epilepsy Visual Reproduction
Committee Chair / Thesis Advisor	Di Iorio, Jacopo, Emory University
Committee Members	Drane, Daniel L, Emory University Carns, Danielle Renee, Emory University

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