Abstract
ObjectElectroencephalography-functional magnetic resonance imaging (EEG-fMRI) coregistration and high-density EEG (hdEEG) can be combined to map noninvasively abnormal brain activation elicited by epileptic processes. By combining noninvasive imaging techniques in a multimodal approach, we sought to investigate pathophysiological mechanisms underlying epileptic activity in seven patients with severe traumatic brain injury.Materials and methodsStandard EEG and fMRI data were acquired during a single scanning session. The EEG-fMRI data were analyzed using the general linear model and independent component analysis. Source localization of interictal epileptiform discharges (IEDs) was performed using 256-channel hdEEG. Blood oxygenation level dependent (BOLD) localizations were then compared to EEG source reconstruction.ResultsOn hdEEG, focal source localization was detected in all seven patients; in six out of seven it was concordant with the expected epileptic activity as defined by EEG data and clinical evaluation; and in four out of seven in whom IEDs were recorded, BOLD signal changes were observed. These activities were partially concordant with the source localization.ConclusionMultimodal integration of EEG-fMRI and hdEEG combining two different methods to localize the same epileptic foci appears to be a promising tool to noninvasively map abnormal brain activation in patients with post-traumatic brain injury.
Highlights
Object Electroencephalography-functional magnetic resonance imaging (EEG-fMRI) coregistration and high-density EEG can be combined to map noninvasively abnormal brain activation elicited by epileptic processes
On high-density EEG (hdEEG), focal source localization was detected in all seven patients; in six out of seven it was concordant with the expected epileptic activity as defined by EEG data and clinical evaluation; and in four out of seven in whom interictal epileptiform discharges (IEDs) were recorded, Blood oxygenation level dependent (BOLD) signal changes were observed
A homogeneous population was studied to explore methodological issues. This group of post-traumatic epilepsy patients was consistent in its number with some clinico-pathological correlations
Summary
Clinico-pathological characteristics were roughly similar: complex partial seizures (focal) and seizure frequency (from 3 to 25 seizures per month); 5 out of 7 patients presented with cognitive and behavioral impairment; all showed focal activity, spike and slow-wave paroxysms. Paroxysmal activity predominated in the left frontal regions (5/7 patients), in the right-temporal regions (1/7) and in the left-central regions (1/7). Patient No 1 This 43-year-old man sustained severe TBI in a road accident. Interictal standard scalp EEG over the right hemisphere was inconstant; low voltage (8–9 Hz) EEG over the left hemisphere showed theta waves associated with polymorphic delta waves which were more evident on the fronto-central hemisphere electrodes; high amplitude (75–120 lV) 2 Hz spike and wave discharges over the left frontal hemisphere electrodes which spread to the right hemisphere
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