Role of preoperative optic tract DTI in tailoring the extent of resection to reduce risk of postoperative visual field defects in patients with mesial temporal sclerosis

Mesial temporal sclerosis (MTS) is the most common pathological substrate of drug-resistant temporal lobe epilepsy (TLE), where anterior temporal lobectomy (ATL) remains the gold standard. 1 However, postoperative visual field defects (VFDs), particularly superior quadrantanopia due to Meyer’s loop injury, is a common morbidity. There is very little literature on the extent of resection and seizure outcome. This ambispective observational study investigated the association between surgical resection extent, postoperative VFDs, and seizure outcomes in MTS patients, utilizing diffusion tensor imaging (DTI) tractography. Patients with MTS undergoing ATL with amygdalo-hippocampectomy at JIPMER hospital meeting the inclusion criteria were analyzed. The cohort included retrospective (n = 14) and prospective (n = 20) arms. Preoperative DTI tractography mapped Meyer’s loop anatomy, while postoperative MRI volumetry quantified temporal resection length. Outcomes included Engel seizure classification 2 and automated perimeter for VFD assessment. Statistical analyses employed logistic regression and ROC curves to evaluate predictors of VFDs and seizure freedom. Postoperative VFDs occurred in 64.71% (22/34), predominantly left (38.23%) or right (26.47%) superior quadrantanopia, with 35.29% retaining normal vision. Engel Grade I (seizure freedom) was achieved in 76.47% (26/34). Resection length (mean: 3.52 ± 0.51 cm) showed no significant association with Engel outcomes ( p = 0.752) or VFD risk p = 0.318). However, DTI identified an optic radiation distance ≤ 3.4 cm as a predictor of VFDs (AUC = 0.714, ( p = 0.023). Prospective patients, benefiting from DTI-guided planning, had lower VFD rates (55% vs. 78.6% retrospective) and shorter resections (3.30 cm vs. 3.82 cm). Structural equation modeling revealed temporal resection length directly influenced VFD severity (β = 0.41, p = 0.013). DTI tractography enables safer, tailored ATL by identifying patients at risk for VFDs. Personalized, image-guided resections preserve vision without compromising seizure control, supporting precision approaches in drug-resistant TLE.