Abstracts

Rationale: MR-guided Laser Interstitial Thermal Therapy (MRgLiTT) is a minimally invasive surgical procedure that is rapidly becoming an alternate first-line surgical option in intractable mesial temporal epilepsy (mTLE). Though safe and effective, seizure outcomes following MRgLiTT are highly variable partly because of patient variability as well as suboptimal targeting and ablation of epileptogenic foci. As one of the radiographic measures calculated from Diffusion Tensor Imaging, the Apparent Diffusion Coefficient (ADC) map delineates pathological tissues and may highlight potential epileptogenic foci in the mesial temporal lobe. We explored whether ablation of ADC hyperintensity clusters is associated with better seizure outcomes in mTLE patients undergoing MRgLiTT.

Methods: Thirty-three mTLE patients who underwent MRgLiTT at our institution were retrospectively studied. Six-month seizure outcome was evaluated using ILAE Outcome Scale. Volumes of the hippocampus and amygdala were segmented from pre-operative ADC map. Machine learning approach was used to identify and segment spatially compact clusters of hyperintense regions (Figure 1). Ablation volume was segmented from the intra-operative MPRAGE sequence. Proportions of (1) ADC cluster volume ablated and (2) ADC local maximal peaks of each cluster ablated were correlated with seizure outcome.

Results: The mean age of patients at surgery was 37.9 years and the mean follow-up duration was 1.9 years. Twenty-six patients were diagnosed with mesial temporal sclerosis. Proportion of hippocampal ADC cluster volumes ablated correlated significantly with seizure outcome (r =-0.402, p < 0.05