Forward and inverse electroencephalographic modeling in health and in acute traumatic brain injury

Irimia, Andrei; Goh, Suzanne; Torgerson, Carinna M.; Chambers, Micah C.; Kikinis, Ron; Horn, John D. Van

doi:10.1016/j.clinph.2013.04.336

Cited by 28 publications

(27 citation statements)

References 53 publications

(62 reference statements)

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“…Many – if not most – of these methods aim to minimize the quantitative differences between the forward and inverse solutions through the use of an adequate optimization algorithm, as described elsewhere [54]. The improved benefit of localizing cortical activation sources using inverse localization versus standard analysis of scalp EEG topography has been documented extensively [55–59]. One reason for this is the fact that typical scalp EEG patterns can extend over large portions of the scalp, which usually limits the ability to localize activation sources below the lobar level.…”

Section: Recent Advances and Emerging Methodsmentioning

confidence: 99%

“…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.…”

Section: Recent Advances and Emerging Methodsmentioning

confidence: 99%

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Epileptogenic focus localization in treatment-resistant post-traumatic epilepsy

Irimia

Horn

2015

Journal of Clinical Neuroscience

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Pharmacologically intractable post-traumatic epilepsy (PTE) is a major clinical challenge for patients with penetrating traumatic brain injury, where the risk for this condition remains very high even decades after injury. Although over 20 anti-epileptic drugs (AED) are in common use today, approximately one-third of epilepsy patients have drug-refractory seizures and even more have AED-related adverse effects which compromise life quality. Simultaneously, there have been repeated recommendations by radiologists and neuroimaging experts to incorporate localization based on electroencephalography (EEG) into the process of clinical decision making regarding PTE patients. Nevertheless, thus far, little progress has been accomplished towards the use of EEG as a reliable tool for locating epileptogenic foci prior to surgical resection. In this review, we discuss the epidemiology of pharmacologically resistant PTE, address the need for effective anti-epileptogenic treatments, and highlight recent progress in the development of noninvasive methods for the accurate localization of PTE foci for the purpose of neurosurgical intervention. These trends indicate the current emergence of promising methodologies for the noninvasive study of post-traumatic epileptogenesis and for the improved neurosurgical planning of epileptic foci resection.

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Section: Recent Advances and Emerging Methodsmentioning

confidence: 99%

Section: Recent Advances and Emerging Methodsmentioning

confidence: 99%

Epileptogenic focus localization in treatment-resistant post-traumatic epilepsy

Irimia

Horn

2015

Journal of Clinical Neuroscience

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“…This may lead to imprecise and mislocalized EEG source estimation. The need of accurate head models (via the finite element method) 50 based on high-resolution magnetic resonance images is therefore key in those cases where accurate cortical localization of the obtained responses is critical. On the other hand, this caveat is less relevant when measuring brain complexity by means of TMS, as an imprecise cortical source localization is not expected to produce changes in the overall complexity of the spatiotemporal dynamics of the response to TMS.…”

Section: Methodological Caveatsmentioning

confidence: 99%

Quantifying Cortical EEG Responses to TMS in (Un)consciousness

et al. 2014

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We normally assess another individual's level of consciousness based on her or his ability to interact with the surrounding environment and communicate. Usually, if we observe purposeful behavior, appropriate responses to sensory inputs, and, above all, appropriate answers to questions, we can be reasonably sure that the person is conscious. However, we know that consciousness can be entirely within the brain, even in the absence of any interaction with the external world; this happens almost every night, while we dream. Yet, to this day, we lack an objective, dependable measure of the level of consciousness that is independent of processing sensory inputs and producing appropriate motor outputs. Theoretically, consciousness is thought to require the joint presence of functional integration and functional differentiation, otherwise defined as brain complexity.Here we review a series of recent studies in which Transcranial Magnetic Stimulation combined with electroencephalography (TMS/EEG) has been employed to quantify brain complexity in wakefulness and during physiological (sleep), pharmacological (anesthesia) and pathological (brain injury) loss of consciousness. These studies invariably show that the complexity of the cortical response to TMS collapses when consciousness is lost during deep sleep, anesthesia and vegetative state following severe brain injury, while it recovers when consciousness resurges in wakefulness, during dreaming, in the minimally conscious state or locked-in syndrome. The present paper will also focus on how this approach may contribute to unveiling the pathophysiology of disorders of consciousness affecting brain-injured patients. Finally, we will underline some crucial methodological aspects concerning TMS/EEG measurements of brain complexity.

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“…However, the attempts to generate realistically contoured cortical sources are significantly hampered by the lack of sufficiently reliable and accurate cortical segmentation of the neonate MRI, as well as by the so far poorly understood cortical activity mechanisms that in neonates are different from the adults (Brockmann et al, 2011;Colonnese and Khazipov, 2012;Kilb et al, 2011;Vanhatalo and Kaila, 2006). Second, our BEM model was only based on few tissue compartments, while recent studies in adults have shown added benefits from as many as eleven (Ramon et al, 2006) or 25 compartments (Irimia et al, 2013). Further segmentation of the neonatal MRI is, however, limited by the dimensions of each tissue type relative to the size of MRI voxels.…”

Section: Limitationsmentioning

confidence: 99%

Analysis of infant cortical synchrony is constrained by the number of recording electrodes and the recording montage

Tokariev

Vanhatalo

Palva

2016

Clinical Neurophysiology

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Dense array EEG Connectivity Brain development h i g h l i g h t sAnalysis of brain connectivity from the neonatal EEG is strongly enhanced by adding the number of electrodes. Sensitivity and specificity of cortical synchrony estimates depend on the analysis montage; average and Laplacian montage have the best performance. The number of electrodes defines the optimal montage and it also sets the limits for the level of analytic details. a b s t r a c tObjective: To assess how the recording montage in the neonatal EEG influences the detection of cortical source signals and their phase interactions. Methods: Scalp EEG was simulated by forward modeling 20-200 simultaneously active sources covering the cortical surface of a realistic neonatal head model. We assessed systematically how the number of scalp electrodes (11-85), analysis montage, or the size of cortical sources affect the detection of cortical phase synchrony. Statistical metrics were developed for quantifying the resolution and reliability of the montages. Results: The findings converge to show that an increase in the number of recording electrodes leads to a systematic improvement in the detection of true cortical phase synchrony. While there is always a ceiling effect with respect to discernible cortical details, we show that the average and Laplacian montages exhibit superior specificity and sensitivity as compared to other conventional montages. Conclusions: Reliability in assessing true neonatal cortical synchrony is directly related to the choice of EEG recording and analysis configurations. Because of the high conductivity of the neonatal skull, the conventional neonatal EEG recordings are spatially far too sparse for pertinent studies, and this loss of information cannot be recovered by re-montaging during analysis. Significance: Future neonatal EEG studies will need prospective planning of recording configuration to allow analysis of spatial details required by each study question. Our findings also advice about the level of details in brain synchrony that can be studied with existing datasets or by using conventional EEG recordings.

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Forward and inverse electroencephalographic modeling in health and in acute traumatic brain injury

Cited by 28 publications

References 53 publications

Epileptogenic focus localization in treatment-resistant post-traumatic epilepsy

Epileptogenic focus localization in treatment-resistant post-traumatic epilepsy

Quantifying Cortical EEG Responses to TMS in (Un)consciousness

Analysis of infant cortical synchrony is constrained by the number of recording electrodes and the recording montage

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