Altered functional connectivity in default mode network in absence epilepsy: A resting‐state fMRI study

Abstract

Dysfunctional default mode network (DMN) has been observed in various mental disorders, including epilepsy (see review Broyd et al. [2009]: Neurosci Biobehav Rev 33:279–296). Because interictal epileptic discharges may affect DMN, resting-state fMRI was used in this study to determine DMN functional connectivity in 14 healthy controls and 12 absence epilepsy patients. To avoid interictal epileptic discharge effects, testing was performed within interictal durations when there were no interictal epileptic discharges. Cross-correlation functional connectivity analysis with seed at posterior cingulate cortex, as well as region-wise calculation in DMN, revealed decreased integration within DMN in the absence epilepsy patients. Region-wise functional connectivity among the frontal, parietal, and temporal lobe was significantly decreased in the patient group. Moreover, functional connectivity between the frontal and parietal lobe revealed a significant negative correlation with epilepsy duration. These findings indicated DMN abnormalities in patients with absence epilepsy, even during resting interictal durations without interictal epileptic discharges. Abnormal functional connectivity in absence epilepsy may reflect abnormal anatomo-functional architectural integration in DMN, as a result of cognitive mental impairment and unconsciousness during absence seizure.

Seizure Frequency Can Alter Brain Connectivity: Evidence from Resting-State fMRI

“…These differences could suggest disease focus, or could be indicators of disease progression and associated compensatory mechanisms. We found that there were several areas of decreased connectivity with associated decreased connectivity of the DMN, as found by many other researchers [7][8]14,35,36 and as has been observed in children with refractory epilepsy, 24 which is known to correlate with disease duration. 6,14 Decreased connectivity was limited to the temporal lobes in patients with infrequent seizures and was widespread and involved the frontal, parietal, and temporal lobes, thalamus, and cerebellum in patients with frequent seizures.…”

Altered intrinsic brain activity in patients with familial cortical myoclonic tremor and epilepsy: An amplitude of low-frequency fluctuation study

“…The PCC is a major node of the default mode network (DMN) [34], which is characterized by decreased activity during attentiondemanding tasks and increased brain activity during the resting-state. Decreased ALFF in the DMN was reported in temporal lobe epilepsy (TLE) patients by a previous fMRI study [24], and diminished functional connectivity in the DMN was also observed in patients with epilepsy [35,36]. The current result that the ALFF in BOLD signals was decreased in the PCC supports the idea that altered low frequency fluctuation might be related to the epileptic seizures in patients with FCMTE.…”

Impaired Default Mode Network on Resting-State fMRI in Children with Medically Refractory Epilepsy

“…Impairment in the DMN does not appear to be specific to the subtypes of seizures and has been described in temporal lobe epilepsy, 13 generalized tonic clonic seizures, 14 and absence of epilepsy. 33 Certain types of epilepsy, such as mesial temporal lobe epilepsy, could have a direct influence on the DMN because the seizure focus included the medial temporal lobe component of the DMN. In our study, in some patients such as case 11, the seizure focus in the right lateral parietal occipital lobe included the lateral parietal cortex component of the DMN, but in others, such as those with seizures arising from the neocortical temporal lobe (cases 3, 6, and 8) or paracentral region (cases 2, 4, and 7), the seizure focus did not include the DMN.…”