Systematically altered connectome gradient in benign childhood epilepsy with centrotemporal spikes: Potential effect on cognitive function

Interictal suppression in patients with mesial temporal lobe epilepsy: A simultaneous PET/fMRI study

Previous stereotactic-electroencephalography (SEEG) results have suggested that seizure-onset zones (SOZs) could be suppressed by strengthened inward connectivity from the rest of the brain during interictal periods, which might explain why people with epilepsy did not have seizures continuously. However, the limited coverage of SEEG contacts and allocation bias hindered a more comprehensive survey of interictal suppression at the whole-brain level. Previous studies also lacked a direct comparison between patients and healthy controls due to the invasive nature of SEEG. In the present study, we introduced metabolic connectivity mapping (MCM), a simultaneous FDG-PET/fMRI-based measure of effective connectivity, to evaluate the inward and outward connectivity of the SOZs in patients with mesial temporal lobe epilepsy (MTLE). Specifically, simultaneous FDG-PET/fMRI data was acquired from 23 patients with left MTLE, 24 patients with right MTLE, and 25 healthy controls. At the whole-brain level, there was significant increase of inward MCM connectivity to the SOZs, which mostly came from mesial-temporo-limbic, anterior and posterior midline regions of the default mode network (DMN) and subcortical nuclei. There was also significant decrease of outward MCM connectivity from the SOZs, which mainly projected to the regions within DMN. The increased net inward MCM to the SOZs, calculated by subtracting outward MCM from the inward MCM, was positively correlated with seizure frequency. Within DMN, MTLE patients showed decreased MCM from the SOZs to posterior cingulate cortex and right ventromedial prefrontal cortex and increased effective connectivity from posterior cingulate cortex to the SOZs. Based on the MCM patterns within DMN, we were able to classify the epileptic side of MTLE with an accuracy of 91.67 % (79.17 % for MRI-negative patients). Overall, our results provide whole-brain evidences for the interictal suppression hypothesis. We also found that the regions within DMN play a critical role in the suppression of SOZs. The pattern of such suppressive network might also serve as potential features for the localization of SOZs. Our neuroimaging results does not only provide a comprehensive understanding of interictal suppression at the whole-brain level, but also shed lights on a non-invasive and time-efficient way for SOZs localization.

Transcriptomic and glucose metabolism of connectome dynamics variability in temporal lobe epilepsy revealed by simultaneous PET-fMRI

Temporal lobe epilepsy (TLE) is associated to genetic predisposition, metabolic abnormalities, and disruptions in brain connectivity. However, the relationships between genetic factors, metabolic processes, and brain network dynamics are not yet fully understood. Simultaneous positron emission tomography and function magnetic resonance imaging (PET/fMRI) data were collected from 66 patients with TLE and 38 healthy controls (HCs). We compared differences in brain network dynamics between TLE patients and HCs using the multilayer network model constructed from extensive temporal features extracted from fMRI. Postmortem whole brain gene expression data were then utilized to identify genes associated with alterations in TLE connectome dynamics, with subsequent enrichment analysis for functional annotation, cellular, and disease associations. Mediation analysis further explored the interrelations among gene expression, glucose metabolism as measured by PET, and brain network dynamics as measured by fMRI. Compared with HCs, individuals with TLE exhibited increased module variability primarily in the default mode network and reduced module variability in the attention network. These case-control differences were validated through split-half analyses and remained unaffected by medication or lateralization. These aberrant module variability patterns were associated with gene expression profiles predominantly related to inhibitory neurons, postsynaptic cell components, MAPK signaling pathway, and these genes were significantly enriched relative to established epilepsy-related gene sets. Moreover, we observed that the effect of gene expression profile on the alterations in TLE connectome dynamics was significantly mediated by changes in glucose metabolism. These findings highlight that alterations in brain network dynamics in TLE are associated with transcriptomic signatures, and that glucose metabolic changes partially mediate this relationship, furthering insights into the biological basis of the disorder.

Simultaneous 18F-FDG PET/MRI predicting favourable surgical outcome in refractory epilepsy patients

OBJECTIVES

To evaluate the (1) successful surgery proportion in patients with clear structural lesions on MRI and single abnormality on 18F-fluorodeoxyglucose positron emission tomography/Magnetic resonance imaging (18F-FDG PET/MRI); (2) predictive value of 18F-FDG PET/MRI for postsurgical outcome in refractory epilepsy patients.

METHODS

A retrospective study was conducted on 123 patients diagnosed with refractory epilepsy who underwent presurgical evaluation involving 18F-FDG PET/MRI and were followed for one-year post-surgery. Two neuroradiologists interpreted the PET/MRI images using visual analysis and an asymmetry index based on the standard uptake value. The Engel classification was used to assess surgical outcomes one-year post-surgery. Prognostic factors predicting post-surgical seizure outcomes were explored using univariate and binary logistic regression.

RESULTS

Definitely single lesion abnormality was observed in 35.0% (43/123) of the patients on the MRI portion of PET/MRI. The proportion increased to 74.0% (91/123) when 18 F-FDG PET portion was added. About 75% (69/91) of patients displaying a clear-cut lesion on 18 F-FDG PET/MRI were classified as Engel Class I one-year post-surgery. The proportion of Engel Class I patients was not significantly different when comparing MRI-single lesion patients with MRI-negative, PET-single lesion patients one year after surgery (81.4% vs. 70.0%, P = 0.24). Binary logistic regression analysis revealed that the detection of a clear single lesion on 18 F-FDG PET/MRI was a strong positive predictor of a favorable surgical outcome (OR 3.518, 95% CI 1.363-9.077, p = 0.009).

CONCLUSION

Single lesion detected on 18 F-FDG PET/MRI is useful to predict good surgical outcome for refractory epilepsy patients; Those patients should be considered as candidates for surgery.