Abstract
Objective: To evaluate declarative memory outcomes in medically refractory epilepsy patients who underwent either a highly selective laser ablation of the amygdalohippocampal complex or a conventional open temporal lobe resection.Methods: Post-operative change scores were examined for verbal memory outcome in epilepsy patients who underwent stereotactic laser amygdalohippocampotomy (SLAH: n = 40) or open resection procedures (n = 40) using both reliable change index (RCI) scores and a 1-SD change metric.Results: Using RCI scores, patients undergoing open resection (12/40, 30.0%) were more likely to decline on verbal memory than those undergoing SLAH (2/40 [5.0%], p = 0.0064, Fisher's exact test). Patients with language dominant procedures were much more likely to experience a significant verbal memory decline following open resection (9/19 [47.4%]) compared to laser ablation (2/19 [10.5%], p = 0.0293, Fisher's exact test). 1 SD verbal memory decline frequently occurred in the open resection sample of language dominant temporal lobe patients with mesial temporal sclerosis (8/10 [80.0%]), although it rarely occurred in such patients after SLAH (2/14, 14.3%) (p = 0.0027, Fisher's exact test). Memory improvement occurred significantly more frequently following SLAH than after open resection.Interpretation: These findings suggest that while verbal memory function can decline after laser ablation of the amygdalohippocampal complex, it is better preserved when compared to open temporal lobe resection. Our findings also highlight that the dominant hippocampus is not uniquely responsible for verbal memory. While this is at odds with our simple and common heuristic of the hippocampus in memory, it supports the findings of non-human primate studies showing that memory depends on broader medial and lateral TL regions.
Highlights
We have demonstrated that minimally invasive surgery for temporal lobe epilepsy (TLE), selective MRI thermographyguided interstitial thermal ablation of the amygdala and hippocampus, results in better naming and object recognition outcomes compared to open temporal lobe (TL) resection [1]
Epilepsy surgery patients undergoing highly selective stereotactic laser amygdalohippocampotomy experience a better outcome on a standard verbal list learning task as compared to a comparable cohort of open resection patients
SLAH patients are less likely to decline on this verbal memory measure, and non-dominant SLAH patients are more likely to improve on this task following surgery than are open resection counterparts
Summary
We have demonstrated that minimally invasive surgery for temporal lobe epilepsy (TLE), selective MRI thermographyguided interstitial thermal ablation of the amygdala and hippocampus (stereotactic laser amygdalohippocampotomy, SLAH), results in better naming and object recognition outcomes compared to open temporal lobe (TL) resection [1] This better outcome likely results from reducing “collateral damage,” sparing lateral and anterior TL structures and white matter pathways presumed to support these cognitive functions when accessing the medial TL [2, 3]. Initial publications examining declarative verbal memory outcomes, a function long associated with medial TL regions, the hippocampus, have suggested that this function can decline after laser ablation of the hippocampus [4,5,6] These studies lacked a comparison open resection group, and when aggregating the number of subjects showing decline across these papers, the percentage of patients declining with SLAH is much less than historically reported outcomes with open resection [7]. This paper will examine effects of surgery on declarative verbal memory by directly comparing our initial SLAH subjects to a near-consecutive cohort of open resection patients on a standard verbal memory measure
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