Frontolimbic brain networks predict depressive symptoms in temporal lobe epilepsy

Abstract

Psychiatric co-morbidities in epilepsy are of great concern. The current study investigated the relative contribution of structural and functional connectivity (FC) between medial temporal (MT) and prefrontal regions in predicting levels of depressive symptoms in patients with temporal lobe epilepsy (TLE). Twenty-one patients with TLE [11 left TLE (LTLE); 10 right TLE (RTLE)] and 20 controls participated. Diffusion tensor imaging was performed to obtain fractional anisotropy (FA) of the uncinate fasciculus (UF), and mean diffusivity (MD) of the amygdala (AM) and hippocampus (HC). Functional MRI was performed to obtain FC strengths between the AM and HC and prefrontal regions of interest including anterior prefrontal (APF), orbitofrontal, and inferior frontal regions. Participants self-reported depression symptoms on the Beck Depression Inventory-II. Greater depressive symptoms were associated with stronger FC of ipsilateral HC-APF, lower FA of the bilateral UF, and higher MD of the ipsilateral HC in LTLE, and with lower FA of the contralateral UF in RTLE. Regression analyses indicated that FC of the ipsilateral HC-APF was the strongest contributor to depression in LTLE, explaining 68.7 % of the variance in depression scores. Both functional and microstructural measures of frontolimbic dysfunction were associated with depressive symptoms. These connectivity variables may be moderating which patients present with depression symptoms. In particular, FC MRI may provide a more sensitive measure of depression-related dysfunction, at least in patients with LTLE. Employing sensitive measures of frontolimbic network dysfunction in TLE may help provide new insight into mood disorders in epilepsy that could eventually guide treatment planning.

The comorbidity of epilepsy and depression: diagnosis and treatment

“…In addition, impairment of brain networks that regulate mood is also common. Using MRI to analyze the function of the brain network helps to measure mood disorders in epileptics; fcMRI is more sensitive for the functional disorders associated with depression, especially for left TLE patients [87].…”

Abnormal Brain Network in Epilepsy and Associated Comorbidites

“…Alterations in the frontolimbic network in TLE patients with depressive symptoms were also observed in functional connectivity studies [70]. In another study [71], the researchers demonstrated that hippocampalanterior prefrontal functional connectivity contributed strongly to depressive symptoms in the left TLE group compared to the right TLE group. Right amygdala functional connectivity was associated with depressive symptoms in both left and right TLE.…”

“…In addition, a graph theory analysis based on T1-weighted 3D spoiled gradient recall (SPGR) showed large scale disruptions in cortical and subcortical brain regions in children with recent onset epilepsy and anxiety [72]. Influence in the network is not necessarily local but potentially influencing other more distant regions [71]. All these findings may help provide new insight into mood disorders in epilepsy that could eventually guide treatment planning.…”

Neurological Diseases from a Systems Medicine Point of View

“…Distorted patterns of neuronal fi ring need to be stratifi ed for different epilepsy subtypes and analyzed for their response to treatment [ 192 ]. Recent advances in multi-scale [ 193 , 194 ] and multimodal neuroimaging [ 195 ] come forward to meet the needs of an integrative network analysis approach. The assessment of treatment outcomes by cellular and brain network analysis is especially important concerning increasing application of DBS in the fi eld of PD [ 196 ], but also epilepsies [ 197 ].…”