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Network Analysis of the Default Mode Network Using Functional Connectivity MRI in Temporal Lobe Epilepsy
Published on: August 5, 2014
Abnormal Profiles of Local Functional Connectivity Proximal to Focal Cortical Dysplasias
René M H Besseling1,2,3, Jacobus F A Jansen2,3, Anton J A de Louw1
1Epilepsy center Kempenhaeghe, Heeze, the Netherlands.
Introduction:
Focal cortical dysplasia (FCD) is a congenital malformation of cortical development that often leads to medically refractory epilepsy. Focal resection can be an effective treatment, but is challenging as the surgically relevant abnormality may exceed the MR-visible lesion. The aim of the current study is to develop methodology to characterize the profile of functional connectivity around FCDs using resting-state functional MRI and in the individual patient. The detection of aberrant connectivity may provide a means to more completely delineate the clinically relevant lesion.
Materials And Methods:
Fifteen FCD patients (age, mean±SD: 31±11 years; 11 males) and 16 matched healthy controls (35±9 years; 7 males) underwent structural and functional imaging at 3 Tesla. The cortical surface was reconstructed from the T1-weighted scan and the registered functional MRI data was spatially normalized to a common anatomical standard space employing the gyral pattern. Seed-based functional connectivity was determined in all subjects for all dysplasia locations. A single patient was excluded based on an aberrant FCD seed time series. Functional connectivity as a function of geodesic distance (along the cortical surface) was compared between the individual patients and the homotopic normative connectivity profiles derived from the controls.
Results:
In 12/14 patients, aberrant profiles of functional connectivity were found, which demonstrated both hyper- and hypoconnectivity as well as combinations. Abnormal functional connectivity was typically found (also) beyond the lesion visible on structural MRI, while functional connectivity profiles not related to a lesion appeared normal in patients.
Conclusion:
This novel functional MRI technique has potential for delineating functionally aberrant from normal cortex beyond the structural lesion in FCD, which remains to be confirmed in future research.
Insights
Resting-state fMRI can identify abnormal brain connectivity in focal cortical dysplasia (FCD) patients, extending beyond visible lesions. This method helps better define the extent of FCD for surgical planning.
Area of Science:
- Neuroimaging
- Epileptology
- Medical Technology
Background:
- Focal cortical dysplasia (FCD) is a developmental brain abnormality frequently causing drug-resistant epilepsy.
- Surgical resection of FCD can be effective, but accurately identifying the full extent of the abnormality is challenging as it may surpass visible MRI lesions.
Purpose of the Study:
- To develop and validate a resting-state functional MRI (fMRI) methodology for characterizing functional connectivity profiles around FCDs in individual patients.
- To determine if aberrant connectivity patterns can help delineate the complete clinically relevant lesion in FCD.
Main Methods:
- Fifteen FCD patients and 16 healthy controls underwent 3 Tesla structural and resting-state fMRI.
- Cortical surface reconstruction and spatial normalization were performed. Seed-based functional connectivity was analyzed.
- Functional connectivity was assessed as a function of geodesic distance and compared to normative control data.
Main Results:
- Aberrant functional connectivity profiles were identified in 12 out of 14 FCD patients, showing both increased and decreased connectivity.
- These abnormal connectivity patterns often extended beyond the boundaries of the lesion visible on structural MRI.
- In patients, functional connectivity profiles unrelated to the FCD appeared normal.
Conclusions:
- This novel fMRI technique shows promise for distinguishing functionally aberrant cortex from normal cortex surrounding FCD lesions.
- The findings suggest that fMRI-based connectivity analysis can provide a more complete delineation of the functionally relevant FCD area.
- Further research is needed to confirm the clinical utility of this technique.
