1130 Anatomical Features Predicting Outcome From Stereotactic Laser Amygdalohippocampotomy

Abstract

INTRODUCTION: Stereotactic laser amygdalohippocampotomy (SLAH) is a novel procedure which is effective and safe for the treatment of temporal lobe epilepsy. Optimal operative ablation location and extent, however, is uncertain, as are the neuroanatomical features guiding successful ablations. METHODS: Patients treated with SLAH for MTS at Emory University between 2011 and 2019 (n = 65) were considered in this retrospective study. Post-procedure T1 MRI scans of patients were used to create manual segmentations of the ablation region of each patient. Ablations were assessed in relation to 1) whether they crossed the coronal plane of the lateral mesencephalic sulcus (LMS), 2) the extent to which the ablation extended posterior to the LMS, and 3) extent of ablation of the uncus. Wilcoxon ranked-sign test was performed for each variable between groups of patients with Engel score 1 versus Engel score 2-4. RESULTS: Distance of ablation past the LMS was not different between Engel class 1 (mean 6.32 ± 4.16 mm), and Engel class 2-4 (7.93 ± 3.75 mm) (p = 0.099). Ratio of ablations extending posterior to the LMS was 0.82 (SD = 0.39) in Engel 1, and 0.90 (SD = 0.30) in Engel 2-4 (p = 0.370). Volume of ablation showed little correlation with outcome, with average ablation of Engel 1 = 6064 ± 2128 mm3, Engel 2-4 = 5828 ± 3031 mm3, and no significant difference with Wilcoxon ranked-sign test (p = 0.239). Ablation of the uncus showed a strong association with better surgical outcome, with ratio of uncus ablation for Engel 1 at 0.71(SD = 0.31), and Engel 2-4 at 0.37 (SD = 0.36); p < 0.001). CONCLUSIONS: Larger ablation alone was not associated with better surgical outcomes. Ablation of the uncus was shown to result in better outcomes. Contrary to current practice, extension of SLAH ablation posterior to the lateral mesencephalic sulcus did not demonstrate improved post-operative outcomes.