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Updated: Jun 5, 2025
Network Analysis of the Default Mode Network Using Functional Connectivity MRI in Temporal Lobe Epilepsy
Published on: August 5, 2014
Reduced Functional Connectivity in the Default Mode Network in EEGs without Other Abnormalities in Early
Agnes Pirker-Kees1,2, Kirsten Platho-Elwischger1, Clemens Lang1,2
1Department of Neurology, Clinic Hietzing with Neurological Center Rosenhuegel, Vienna, Austria.
Insights
Disrupted brain network connectivity in the default mode network (DMN) may serve as an early marker for Creutzfeldt-Jakob disease (CJD), even when electroencephalograms (EEGs) appear normal. This study highlights potential new diagnostic avenues for early CJD detection.
Area of Science:
- Neuroscience
- Medical Diagnostics
- Brain Network Analysis
Background:
- Creutzfeldt-Jakob disease (CJD) is a fatal, transmissible neurodegenerative disorder.
- Early-stage CJD often presents with normal-appearing electroencephalograms (EEGs).
- Identifying early diagnostic markers for CJD is crucial.
Purpose of the Study:
- To investigate disruptions in default mode network (DMN) functional connectivity (FC) as an early diagnostic marker for CJD.
- To assess if DMN alterations can be detected in CJD patients with visually normal EEGs.
Main Methods:
- Compared EEGs from 7 CJD patients and 7 subjective cognitive impairment (SCI) patients.
- Calculated FC using phase locking value across delta, theta, alpha, and beta bands.
- Assessed DMN global efficacy using inverse characteristic path length.
Main Results:
- Significantly lower DMN global efficacy in the gamma band was observed in CJD patients compared to SCI patients.
- Decreased FC was found between orbitofrontal regions and the parahippocampal/anterior cingulate gyri in CJD patients.
- These alterations were present in early CJD with visually normal EEGs.
Conclusions:
- Disruption of the DMN in the gamma band and altered FC in specific brain regions are evident in early CJD with normal EEGs.
- EEG-derived brain network properties show potential as early diagnostic tools for CJD.
- Further research is warranted to evaluate the diagnostic value of FC in early CJD detection.
Introduction:
Creutzfeldt-Jakob disease (CJD) is a rare, neurodegenerative disorder that is incurable, always fatal, and transmissible. EEG is an integral part of the diagnostic workup with typical periodic sharp wave complexes indicative of CJD, but early in the disease EEG is often unaltered. Accordingly, we aimed at evaluating disruption of brain network functional connectivity (FC) in regions belonging to the default mode network (DMN) as a potential early marker in CJD when EEG is considered visually normal.
Methods:
EEGs considered visually normal obtained from 7 CJD patients were compared to EEGs of 7 patients with subjective cognitive impairment (SCI) using Brainstorm application for MATLAB. FC was calculated using the phase locking value separately for the delta-, theta-, alpha-, and beta-frequency band. The global efficacy of the DMN was calculated as the inverse characteristic path length with brain regions belonging to the DMN as nodes.
Results:
CJD versus SCI had significantly lower global efficacy of the DMN in the gamma band. FC was decreased between bilateral orbitofrontal regions and the right parahippocampal gyrus and between bilateral orbitofrontal gyrus and the right anterior cingulate gyrus in CJD.
Conclusion:
Our findings provide evidence of disruption of the DMN in the gamma band and alterations of FC between specific brain regions in early CJD patients with visually normal EEGs. EEG brain network properties bear potential as a diagnostic tool for CJD early in the disease course in addition to established criteria. These findings call for further studies evaluating the diagnostic value of FC in early CJD.
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