MR-guided laser hemispherotomy with detailed tractographic analysis: Evidence for individualized network-based disconnection

Background Laser interstitial thermal therapy (LITT) hemispherotomy offers a minimally invasive alternative to open hemispheric disconnection for medically refractory epilepsy. This study used quantitative deterministic tractography to evaluate whether the pattern of tract disconnection, rather than total ablation volume, predicts seizure outcome following LITT hemispherotomy.Methods Ten patients (median age 11 years, range 6-19) with medically refractory hemispheric epilepsy underwent LITT hemispherotomy between February 2021 and June 2025. Deterministic tractography was performed on paired preoperative and postoperative diffusion tensor imaging in five patients, quantifying percent volume ablation across 17 white matter pathways in commissural, temporal/limbic, and projection categories.Results Nine of 10 patients (90%) achieved Engel Class I outcomes at a median follow-up of 24.7 months (range 8.7-60.7). Mean total hemispheric tract volume ablated was 6.9% (range 1.2-19.8%). No patient developed hydrocephalus. Mean hospital length of stay was 2.1 days. Tractographic analysis revealed that no two patients shared an identical disconnection profile. For example, Case 5 achieved seizure freedom through commissural disconnection alone with no measurable projection tract disconnection, while Case 3 had the highest total ablation volume yet failed with only 9% splenium ablation.Conclusions These data support an individualized network hypothesis for hemispheric disconnection: seizure freedom depended on ablation of patient-specific seizure propagation pathways rather than maximization of total ablation volume. Prospective integration of high-resolution tractography with preoperative seizure generator localization could enable a minimal but sufficient disconnection strategy and warrants evaluation in future studies.