Electroencephalographic inverse localization of brain activity in acute traumatic brain injury as a guide to surgery, monitoring and treatment

Abstract

Objective To inverse-localize epileptiform cortical electrical activity recorded from severe traumatic brain injury (TBI) patients using electroencephalography (EEG). Methods Three acute TBI cases were imaged using computed tomography (CT) and multimodal magnetic resonance imaging (MRI). Semi-automatic segmentation was performed to partition the complete TBI head into 25 distinct tissue types, including 6 tissue types accounting for pathology. Segmentations were employed to generate a finite element method model of the head, and EEG activity generators were modeled as dipolar currents distributed over the cortical surface. Results We demonstrate anatomically faithful localization of EEG generators responsible for epileptiform discharges in severe TBI. By accounting for injury-related tissue conductivity changes, our work offers the most realistic implementation currently available for the inverse estimation of cortical activity in TBI. Conclusion Whereas standard localization techniques are available for electrical activity mapping in uninjured brains, they are rarely applied to acute TBI. Modern models of TBI-induced pathology can inform the localization of epileptogenic foci, improve surgical efficacy, contribute to the improvement of critical care monitoring and provide guidance for patient-tailored treatment. With approaches such as this, neurosurgeons and neurologists can study brain activity in acute TBI and obtain insights regarding injury effects upon brain metabolism and clinical outcome.

Epileptogenic focus localization in treatment-resistant post-traumatic epilepsy

“…Although such localization has been impractical in the past, two recent studies have demonstrated that effective and accurate inverse localization of epileptogenic activity is feasible in the context of accurate inverse localization and that the use of noninvasive EEG to identify PTE foci holds considerable clinical promise. In these studies [55, 56], EEG source localization was demonstrated in six patients with acute TBI using anatomically constrained models of the head which account for TBI-related pathology. Multimodal MRI volumes were employed to create highly detailed head models via the finite element method using as many as 25 tissue types, including six types accounting for pathology.…”

Bedside functional brain imaging in critically-ill children using high-density EEG source modeling and multi-modal sensory stimulation

“…Moreover, as this set-up relies on EEG source imaging to generate cortical activation maps, it suffers from the known limitations of these approaches ( Michel et al, 2004 , Michel and Murray, 2012 ). Specifically, in the context of brain injuries there might be conductivity changes that affect the forward model ( Irimia et al, 2013a , Irimia et al, 2013b ) and localization accuracy. In addition, our study used a generic head model and when possible compared to the sources generated by the participant's MRI, without a marked difference in results.…”

“…Use of EEG and EPs are becoming more prevalent in studies of patients with decreased levels of consciousness ( Harrison and Connolly 2013 ). Some researchers have also suggested that in traumatic brain injuries it may be useful to combine these electrophysiological measures with imaging modalities such as CT and MRI ( Duncan et al, 2011 , Irimia et al, 2013a , Irimia et al, 2013b ).…”

Influence of Patient-Specific Head Modeling on EEG Source Imaging

“…Nevertheless, the use of individually defined forward models can be mandatory in several medical applications that demand a proper assisted diagnosis and adequate interpretation of patient states from the involved neurophysiological data [18][19][20]. In this regard, the combination of both approaches to enhance the model of brain structure differently implies inter-and intraobserver variability, not always decreasing enough the impact of uncertainty in the inherent geometrical complexities.…”