Dissociated multimodal hubs and seizures in temporal lobe epilepsy

Abstract

ObjectiveBrain connectivity at rest is altered in temporal lobe epilepsy (TLE), particularly in “hub” areas such as the posterior default mode network (DMN). Although both functional and anatomical connectivity are disturbed in TLE, the relationships between measures as well as to seizure frequency remain unclear. We aim to clarify these associations using connectivity measures specifically sensitive to hubs.MethodsConnectivity between 1000 cortical surface parcels was determined in 49 TLE patients and 23 controls with diffusion and resting-state functional magnetic resonance imaging. Two types of hub connectivity were investigated across multiple brain modules (the DMN, motor system, etcetera): (1) within-module connectivity (a measure of local importance that assesses a parcel's communication level within its own subnetwork) and (2) between-module connectivity (a measure that assesses connections across multiple modules).ResultsIn TLE patients, there was lower overall functional integrity of the DMN as well as an increase in posterior hub connections with other modules. Anatomical between-module connectivity was globally decreased. Higher DMN disintegration (DD) coincided with higher anatomical between-module connectivity, whereas both were associated with increased seizure frequency. DD related to seizure frequency through mediating effects of anatomical connectivity, but seizure frequency also correlated with anatomical connectivity through DD, indicating a complex interaction between multimodal networks and symptoms.InterpretationWe provide evidence for dissociated anatomical and functional hub connectivity in TLE. Moreover, shifts in functional hub connections from within to outside the DMN, an overall loss of integrative anatomical communication, and the interaction between the two increase seizure frequency.

MRI characterization of temporal lobe epilepsy using rapidly measurable spatial indices with hemisphere asymmetries and gender features

“…The invasive intracranial EEG is supposed to be useful for the surgical localization of epileptic foci in patients with intractable epilepsy; the data on safety and surgical outcome with this technique are still inadequate [8][9][10][11]. The ample evidences of advanced research using multimodal combinational non-invasive neuroimaging techniques like MRI, MRS, f-MRI, FDG-PET, SPECT, and MEG have revealed that most of the cases of TLE patients are accompanied by pathological changes in brain structure and function network, including cortical and subcortical (hippocampus and parahippocampus) structures [12][13][14]. Such multimodal combinational imaging (structural and functional) approaches are being suggested to detect the laterization of TLE with ictal and interictal onset in pre-surgical diagnostic purpose [15][16][17][18][19][20].…”

Postoperative seizure freedom does not normalize altered connectivity in temporal lobe epilepsy

“…It is unclear whether these changes reflect a chronic effect of the disease on brain connectivity or whether they are an index of acute seizure burden 3; 4 . Epilepsy surgery is a potential therapeutic option for patients with medically intractable epilepsy that in many patients can drastically reduce seizure burden 5; 6 .…”

Presurgical Mapping of the Language Network Using Resting-state Functional Connectivity

“…It is acquired at a resting state of the subject without requiring any tasks. Over a couple of decades, there have been increasing interests in the application of this method for understanding the brain networks in both healthy subjects and patients with neuropsychiatric diseases, e.g., Alzheimer's disease, schizophrenia and epilepsy (9,10,11). Here, we review the technique and the applications of RS-fMRI for evaluating the language function, and discuss combining functional and structural connectivity analyses.…”

“…(8,9). Previous studies have revealed the altered connectivity in patients with epilepsy (11) compared with healthy controls; however, the relationship between focal epileptogenicity and abnormal connectivity is unclear. (14).…”

“…Previous studies have demonstrated that the structural connectivity networks are associated with or predictive of the functional connectivity networks in healthy subjects (26) and patients with temporal lobe epilepsy (30). Takaya et al compared the structural, functional connectivity and regional BOLD activation, derived from DTI tractography, resting-state fMRI and task-based fMRI, respectively, and demonstrated the asymmetry overlaps in the left posterior temporal and parietal region in the right-handed healthy subjects (29).…”