Impaired default mode network on resting-state FMRI in children with medically refractory epilepsy

Abstract

Background and purpose: Resting-state networks including the DMN have been shown to be abnormal in adults with temporal lobe epilepsy. However, little is known about the DMN in children with medically refractory epilepsy. The aim was to determine whether there was a difference in the DMN in children with medically refractory epilepsy relative to controls.

Materials and methods: Eleven children with medically refractory epilepsy and 11 age-matched healthy controls underwent resting-state fMRI. IC analysis was used to identify the DMN. A random-effects analysis was performed on the Z-maps of the DMN within each group and between groups. We calculated the temporal correlation coefficients of pairs of ROIs: PCC/PCUN, mPFC, and left and right lateral parietal cortices. The relations between z scores of temporal correlation coefficients of pairs of ROIs and clinical seizure parameters and IQ were assessed.

Results: The patients demonstrated decreased DMN connectivity in the PCC/PCUN, bilateral lateral parietal cortex, and anterior and midcingulate relative to controls. There was reduced connectivity between the mPFC-right lateral parietal cortex, the PCC/PCUN-left lateral parietal cortex, and the PCC/PCUN-right lateral parietal cortex pairs of ROIs in patients compared with controls. There were no significant correlations between the z scores of temporal correlation coefficients of the 6 pairs of ROIs in patients and age of seizure onset, duration of epilepsy, number of medications, seizure frequency, and IQ.

Conclusions: We have found reduced connectivity in the DMN in children with medically refractory epilepsy. Further studies are needed to determine whether different seizure types have different effects on the DMN and whether the impaired connectivity is related to cognitive functions subserved by the DMN.

Fig. 1.

Random-effects analysis of the DMN in controls (A) and (B) patients. C, The patients demonstrate decreased DMN connectivity in the PCC/PCUN, bilateral lateral parietal cortex, and anterior and midcingulate.

Fig. 2.

Functional connectivity within the DMN in controls (A) and patients (B). Numbers in the rectangles correspond to the average pair-wise correlation coefficients. C, Comparison of functional connectivity within the DMN in controls versus patients shows significant reduction in mPFC–right lateral parietal cortex (LPC), PCC/PCUN–right LPC, and PCC/PCUN–left LPC. Numbers in rectangles represent the P value for the comparison of the mean correlation coefficients of control and patient groups. Thick lines represent significant changes in the pair-wise correlation between controls and patients (P < .05).