Ablation of Apparent Diffusion Coefficient Hyperintensity Clusters and Mesial Temporal Lobe Epilepsy Improves Seizure Outcomes after Laser Interstitial Thermal Therapy

Objective: Laser Interstitial Thermal Therapy (LiTT) is a minimally invasive surgical procedure for intractable mesial temporal epilepsy (mTLE). LiTT is safe and effective but seizure outcomes are highly variable due to patient variability, suboptimal targeting, and incomplete ablation of epileptogenic zone. Apparent Diffusion Coefficient (ADC) is an MRI sequence that can identify potential epileptogenic foci in the mesial temporal lobe to improve ablation and seizure outcome. The objective of this study was to investigate whether ablation of tissue clusters with high ADC values in the mesial temporal structures is associated with seizure outcome in mTLE after LiTT. Methods: Thirty mTLE patients who underwent LiTT at our institution were analyzed. Seizure outcome was categorized as complete seizure freedom (ILAE Class I) and residual seizures (ILAE Class II-VI). Volumes of hippocampus and amygdala were segmented from preoperative T1 MRI sequence. Spatially distinct hyperintensity clusters were identified in the preoperative ADC map. Percent cluster volume and number ablated were associated with seizure outcomes. Results: The mean age at surgery was 36.6 years and mean follow-up duration was 1.9 years. Proportions of hippocampal cluster volume (35.20% vs. 16.5 %, p = 0.014) and cluster number (27.1 % vs 4.2 %, p = 0.0007) ablated were significantly higher in patients with seizure freedom. For amygdala clusters, only proportion of cluster number ablated was significantly associated with seizure outcome (13.2 % vs. 0 %, p = 0.016). Ablation of hippocampal clusters predicted seizure outcome, both by volume (AUC = 0.7679) and number (AUC = 0.8086) ablated. Significance: Seizure outcome after LiTT in mTLE patients was significantly associated with the extent of cluster ablation in the hippocampus and amygdala. The results suggest that preoperative ADC analysis may help identify high yield pathological tissue clusters that represent epileptogenic foci. ADC-based cluster analysis can potentially assist ablation targeting and improve seizure outcome after LiTT in mTLE.