Multimodal modeling of the ictal onset zone in refractory insular epilepsy and seizure outcome of magnetic resonance-guided laser interstitial therapy: A pediatric single-center retrospective study.

Objective

This study was undertaken to evaluate seizure outcomes after magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) in children with insular epilepsy and to assess how the extent of ablation overlaps with multimodal definitions of the ictal onset zone (IOZ).

Methods

We conducted a retrospective, single-center study including consecutive pediatric patients treated with MRgLITT for insular epilepsy. All patients underwent presurgical evaluation including electroencephalography (EEG) and magnetic resonance imaging (MRI); fluorodeoxyglucose positron emission tomography (FDG-PET) and stereo-EEG (SEEG) were performed in negative-MRI cases. Epileptic zone was identified by visual analysis of SEEG recording. Postablation contrast-enhancing volumes were manually segmented and coregistered with IOZ estimates derived from Multi-centre Epilepsy Lesion Detection (MELD) MRI analysis, FDG-PET voxel-based analysis, and the Epileptogenicity Index, when available. Spatial concordance between modalities was assessed using Dice similarity coefficients, and the proportion of each IOZ modality encompassed within the ablation volume was correlated with postoperative seizure outcomes (International League Against Epilepsy classification).

Results

Eight children (median age = 10.4 years, range = 2.3-17) were included, with a median postoperative follow-up of 38 months. Two patients had insular tumors, and both achieved seizure freedom after complete ablation. Among the six MRI-negative patients, FDG-PET revealed insular hypometabolism in four, MELD detected a median of one insular cluster (range 1-3), and SEEG identified focal insular ictal activity in three cases. Overall, four negative-MRI patients achieved seizure freedom: three after MRgLITT alone and one after MRgLITT combined with frontal opercular resection. One transient postoperative aphasia was observed. Intermodality spatial concordance was low across all comparisons. A greater proportion of FDG-PET hypometabolism included in the ablation volume was associated with better seizure outcomes (p = .012).

Significance

MRgLITT is an effective and safe treatment option for focal insular epilepsy in children, either as standalone therapy or in a combined approach. Optimal outcome depends on accurate preoperative delineation of the IOZ and its complete ablation.