DTI-based Study On The Association Between Thalamocortical Structural Connection And The Efficacy Of Vagus Nerve Stimulation In Patients With Drug-resistant Epilepsy

Purpose Vagus nerve stimulation(VNS)is an important treatment option for the patients with drug-resistant epilepsy(DRE),but not all patients with DRE can benefit from it.At present,there is lack of effective indicator to predict the efficacy of VNS.In this study,the associations between thalamocortical structural connection and postoperative outcomes of VNS in patients with DRE were analyzed by diffusion tensor imaging(DTI),so as to provide a reliable and convenient indicator to predict the efficacy of VNS in patients with DRE.Methods DRE patients who underwent VNS in the Department of Neurosurgery of the First Affiliated Hospital of Anhui Medical University from June 2020 to October 2021were selected to conduct a cranial DTI scan before surgery.Health controls were obtained from the Human Connection Group Program(HCP).The improved Engel classification and Mc Hugh classification were used to evaluate the efficacy of VNS at 3 and 6 months after surgery.The thalamic subarea was individually segmented as the region of interest(ROI)by probabilistic tractography.Five pathways of the structural connection between the thalamus ROI and the corresponding cerebral cortex ROI were analyzed respectively,including thalamus-prefrontal cortex(thalamus-PFC),thalamus-motor and premotor cortex(thalamus-MC),thalamus-somatosensory cortex(thalamus-SC),thalamusparietal and occipital cortex(POC)and thalamus-temporal cortex(thalamus-TC).The integrity of the thalamocortical structural connection was evaluated by four indices,including fractional anisotropy(FA),mean diffusivity(MD),radial diffusivity(RD)and axial diffusivity(AD).DRE patients were divided into poor and effective therapeutic groups to compare their thalamocortical structural connections and to evaluate the associations between these connections and postoperative outcomes of VNS.Results In Comparison with the health control group,the FA value of DRE patients was significantly lower in thalamus-PFC,thalamus-MC,thalamus-SC,thalamus-TC(P<0.05),and the RD value increased in thalamus-SC(P<0.05).The FA value of DRE patients in thalamus-PFC was significantly lower than that of thalamus-MC(P<0.01)and thalamusSC(P<0.05),and the FA value in thalamus-TC was significantly lower than thalamusMC,thalamus-TC and thalamus-POC(P<0.01).The RD value in thalamus-TC was significantly higher than the that in the other four regions(P<0.01),and RD value in thalamus-POC was higher than thalamus-MC(P<0.05).DRE patients who had better response to VNS had higher FA value in thalamus-PFC,while RD value had no statistical differences in all five regions(P>0.05).Conclusions VNS could decrease epileptic seizures in DRE patients and was generally safe and controllable.The division of thalamic subarea according to the individualized thalamocortical structural connection by probabilistic tractography is of significance for epilepsy surgery.Damnifications of nerve fiber in the thalamocortical structural connection in DRE patients were related to neurocyte demyelination.Patients with relatively complete thalamocortical structural connection can obtain better outcomes.