Brain Volume Loss After Stereotactic Laser Interstitial Thermal Therapy in Patients With Temporal Lobe Epilepsy

Abstract

Background and purpose: Temporal lobe epilepsy is the most common form of focal epilepsy. MR-guided laser interstitial thermal therapy (LITT) of the amygdalohippocampal complex has become an established therapy option in case of drug resistance. Long-term anatomic network effects on the brain due to deafferentiation have not yet been evaluated.

Methods: We analyzed brain volumes of 11 patients with temporal lobe epilepsy before and 1-year after hippocampal LITT with FastSurfer segmenting T1-weighted data. Additionally, we performed visual ratings and measurements.

Results: A total of 11 patients with temporal lobe epilepsy (7 left-sided, 4 right-sided) were included (5 females); the mean age years (±standard deviation) at surgery was 41.5 (±18.4) years. The mean postoperative defect size was 1427 (±517) mm³. Volumetry as well as visual ratings found a progressive volume loss after left-sided surgery in the ipsilateral temporal lobe, the contralateral (right) part of the thalamus, and especially contralateral (right) fusiform cortex. These changes could not be detected for right-sided surgery.

Conclusion: A (partial) ablation of the left (dominant) hippocampus appears to exert long-term effects on the right thalamus and right-sided temporal cortices. However, we could not observe this effect in the reverse direction. Volumetric studies for larger cohorts should be conducted to investigate these findings.

Keywords: FastSurfer; epilepsy; hippocampal region; laser interstitial thermal therapy; volumetry.

FIGURE 1

Introduction example. Early postoperative MRI following laser interstitial thermal therapy in a patient with right‐sided temporal lobe epilepsy. In the right amygdala and hippocampal region beside the temporal horn (green arrow), a central elongated early postoperative defect is visible following laser ablation (red arrow) surrounded by thermal edema (yellow arrows) that closely resembles infarction‐related edema due to diffusion restriction. (A) Transversal T2‐weighted Turbo‐Spin‐Echo; (B) transversal T1‐weighted Turbo‐Field‐Echo; bottom: transversal diffusion‐weighted imaging; (C) B1000; (D) apparent diffusion coefficient map.

FIGURE 2

3D Slicer example demonstrates a manual volumetric measurement of the defect zone (green) following laser interstitial thermal therapy. 3D, three‐dimensional; AR, anterior right; B, brain series number and name; cm³, cubic centimeter; I, inferior; L, left; LA, lateral anterior; mm³, cubic millimeter; P, posterior; R, right; S, superior.

FIGURE 3

Inclusion Flow Chart. 3D, three‐dimensional; LITT, laser interstitial thermal therapy; n, number of patients; TLE, temporal lobe epilepsy.

FIGURE 4

Four coronal slices of post‐surgery segmentations (aparc Desikan–Killiany–Tourville atlas + aseg.deep and orig.mgz). Blue arrows point at the post‐surgery defect. Red arrows point at minimal fail segmentations; the yellow arrow points at a vessel. (A) Right‐sided surgery; no fail segmentations found. (B) Left‐sided surgery hemorrhage in the cavity: no fail segmentations found; (C) right‐sided surgery; and (D) left‐sided surgery, both with minimal fail segmentations of the ipsilateral entorhinal cortex and ipsilateral > contralateral amygdala. The primary olfactory cortex is not segmented in the Desikan–Killiany–Tourville atlas.

FIGURE 5

Volume loss of the contralateral entorhinal cortex following laser therapy in a 30‐year‐old‐patient. (A) Pre‐surgery coronal T1‐weighted magnetization prepared—rapid gradient echo; (B) 1‐year follow‐up coronal T1‐weighted Turbo‐Field‐Echo (blue arrow points at the postoperative defect zone after left‐sided surgery; yellow arrows at the widening of the contralateral entorhinal cortex; green arrows at the temporal horns).