Study On Brain Structural And Functional Abnormalities In Epilepsy With Depression

For a long time,epilepsy was considered to be a disorder of the central nervous system manifested only by the occurrence epileptic seizures and its treatment was focused in the achievement of a seizure-free state.In the past few decades,however,neurologists have concluded that cognitive and psychiatric comorbidities have been identified in a number of patients with epilepsy(PWE).In fact,International League against Epilepsy proposed that epilepsy is a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures,and by the neurobiologic,cognitive,psychological,and social consequences of this condition,which implies a need to factor-in the existence of comorbidities in the comprehensive treatment and management of PWE.Depression is a common epileptic comorbidities,and its pathogenesis is not clear.Previous studies have found the abnormal structural and functional connections in default mode network(DMN)and the whole brain in epilepsy and depression.However,there are few studies on structural and functional connectivity in epilepsy with depression.Using this model,our work has studied brain structural and functional connections in DMN and the whole brain in epilepsy with depression.To study the structural and functional connectivity of DMN in epilepsy with depression,we obtained diffusion tensor imaging,resting state functional magnetic resonance images and T1-weighted imaging data from 25 patients and 27 healthy subjects.Firstly,the DMN network is represented using the seed-based method.Then,structural and functional connections in DMN are analyzed.Finally,the correlations between connection characteristics and clinical parameters were calculated.The results showed that the decreased fractional anisotropy in posterior cingulate cortex(PCC)and medial prefrontal cortex,the increased mean diffusion and the reduced functional connectivity between PCC and left hippocampus.It was also found that abnormal structural connectivity between PCC and bilateral angular gyrus.Parahippocampal gyrus and medial prefrontal cortex are important areas of limbic system,which are related to processing and regulation of emotion.The altered connections of these regions may lead to the patient’s emotional regulation deficit,which may be a brain mechanism of epilepsy with depression.To examine the whole brain’s structural and functional connections in epilepsy with depression,voxel-based morphometry(VBM)was used to analyze gray matter deficits in patients,then we examined the functional connectivity between the reduced gray matter regions and the whole brain.The results showed that the reduced gray matter volume in anterior cingulate cortex,middle cingulate cortex,cerebellar 2 crus and cerebellar 8 areas in,and dysfunctional connectivity among several brain regions associated with emotion and cognition,which implied that cerebellum and limbic system may be related to symptoms in epilepsy with depression.Our work has studied the DMN and the whole brain’s structural and functional connections in epilepsy with depression from the hypothesis-driven and data-driven levels.The results revealed that structural and functional connectivity of DMN in patients were abnormal.The abnormal connectivity of several brain regions associated with emotion in DMN may be related to depressive symptoms in patients with epilepsy.VBM analysis showed the reduced gray matter volume in cerebellum and limbic system in patient,and dysfunctional connectivity between the reduced gray matter regions and brain regions associated with emotion and cognition,which indicated limbic system and cerebellum may be related to the patient’s symptoms.We hope our findings can provide valuable information to further understand the pathogenesis of epilepsy with depression.