Stereotactic laser amygdalohippocampotomy for mesial temporal lobe epilepsy

Abstract

Objective: To evaluate the outcomes 1 year and longer following stereotactic laser amygdalohippocampotomy for mesial temporal lobe epilepsy in a large series of patients treated over a 5-year period since introduction of this novel technique.

Methods: Surgical outcomes of a consecutive series of 58 patients with mesial temporal lobe epilepsy who underwent the surgery at our institution with at least 12 months of follow-up were retrospectively evaluated. A subgroup analysis was performed comparing patients with and without mesial temporal sclerosis.

Results: One year following stereotactic laser amygdalohippocampotomy, 53.4% (95% confidence interval [CI] = 40.8-65.7%) of all patients were free of disabling seizures (Engel I). Three of 9 patients became seizure-free following repeat ablation. Subgroup analysis showed that 60.5% (95% CI = 45.6-73.7%) of patients with mesial temporal sclerosis were free of disabling seizures as compared to 33.3% (95% CI = 15.0-58.5%) of patients without mesial temporal sclerosis. Quality of Life in Epilepsy-31 scores significantly improved at the group level, few procedure-related complications were observed, and verbal memory outcome was better than historical open resection data.

Interpretation: In an unselected consecutive series of patients, stereotactic laser amygdalohippocampotomy yielded seizure-free rates for patients with mesial temporal lobe epilepsy lower than, but comparable to, the outcomes typically associated with open temporal lobe surgery. Analogous to results from open surgery, patients without mesial temporal sclerosis fared less well. This novel procedure is an effective minimally invasive alternative to resective surgery. In the minority of patients not free of disabling seizures, laser ablation presents no barrier to additional open surgery. Ann Neurol 2018;83:575-587.

Figure 1. Representative MR images from the pre- and post-operative course of a representative SLAH patient with right MTS

Pre-ablative diagnostic workup demonstrates the characteristic findings of MTS being hippocampal atrophy with increased T2 (A, coronal) and T2-FLAIR (B, coronal) intensity. This is further highlighted by NeuroQuant (CorTechs Laboratory, San Diego, CA) segmentation (C, axial) with the colorized medial temporal lobe structures (hippocampus in brown and amygdala in blue) overlaid on T1 imaging. Pre-operative FDG-PET (D, axial) demonstrates hypometabolism in the right medial temporal structures, consistent with right MTS. Intraoperative MR thermometry is utilized to guide the procedure (E, axial screenshot of Visualase thermal map generated during LITT of the amygdala) and assess the thermal damage following the procedure (F, axial screenshot of Visualase irreversible damage estimation). Immediate post-ablative imaging demonstrates T1 hypointensity of the ablation target with peripheral contrast enhancement (G, coronal and H, axial, MPRAGE) and T2 (I, coronal) hypointense rings surrounding the ablation. 12-month follow-up imaging demonstrates necrosis and volume reduction of the target tissue with the resulting cavitation on T1 (J, coronal and K, axial MPRAGE) and T2 hyperintensity (L, coronal).

Figure 2. Outcome following SLAH at 12-month follow-up

(A) Distribution of 12-month patient outcomes by Engel class with respect to last SLAH procedure. The numbers above the bars indicate the percentage of patients in each class and the numbers within the bars equal the number of patients (Bar color: All: Black; MTS: Dark Grey; Non-MTS: Light Grey). (B) Comparison of 12-month patient outcomes as stratified by Engel class for patients having undergone repeat SLAH with the 12-month outcomes following the first SLAH (Original) compared with the 12-month outcome following the repeat SLAH (Repeat) demonstrating sustained or improved outcome following the repeat procedure. Non-MTS and MTS groups are presented. (C) The one-year seizure freedom rates observed for all patients with the 95% CIs. The black diamonds are the outcomes with respect to the last SLAH procedure (i.e. including repeat procedures) and the grey squares are the outcomes with respect to only the first procedure. All patients are presented, as well as the sub groups of MTS and Non-MTS.

Figure 3. Long term seizure outcomes

Kaplan-Meier depiction of the time to recurrent seizures following last SLAH. All patients (A) are presented, as well as a comparison (B) of the patients with MTS (dark grey) to those without (light grey). Dashed lines corresponding in color to their solid line counterparts indicate 95% confidence intervals. Tick marks indicate censorship. A vertical grey dashed line is presented to indicate the 12-month time point.