Uncommon EEG burst-suppression in severe postanoxic encephalopathy

ObjectiveIn patients suffering from severe hypoxia, the EEG may show a burst-suppression pattern, characterized by low-voltage activity and the occurrence of high amplitude burst-like events. We describe the two-timescale burst phenomenology of this postanoxic condition.MethodsWe present EEG recordings showing remarkable burst phenomenology in two postanoxic patients and consider potential mechanisms responsible for the generation of the burst-suppression patterns. We quantify the postanoxic condition in terms of the dimension (number of degrees of freedom) of its dynamics by comparing our data with a system of three ordinary differential equations with two timescales subject to varying degrees of noise.ResultsEEGs displayed extreme similarity of the bursts, separated by interburst intervals up to more than 300 s. This pattern reflects a significant reduction in the number of functional brain states. This post-anoxic condition is found to have dimension 3, consisting of fast dynamics responsible for the bifurcation to bursting behavior, and a long time-scale responsible for burst termination and the interburst intervals.ConclusionsLow-dimensional postanoxic brain states, as manifested by burst-similarity, appears to indicate an irreversible loss of brain function and consciousness.SignificanceEvidence of brain functionality in a persistent low dimensional state due to severe hypoxia is indicative of permanent loss of consciousness with essentially no chance for recovery. Quantitative evidence for such degenerate states is important for clinical decision making.     

The prognostic value of discontinuous EEG patterns in postanoxic coma

Objective

To assess the value of background continuity and amplitude fluctuations of the EEG for the prediction of outcome of comatose patients after cardiac arrest.

Periodic eye opening and swallowing movements associated with post-anoxic burst-suppression EEG pattern.

We report a video-electroencephalogram study of a 50-year-old woman who developed a clinical picture consisting of stereotyped periodic eye opening followed by eye closing, with or without swallowing movements, after a prolonged cardiopulmonary arrest. These movements were associated with a burst-suppression pattern on the electroencephalogram. [Published with video sequences].     

Intracranial EEG in temporal lobe epilepsy.

Intracranial EEG monitoring before epilepsy surgery, while becoming less commonly performed in patients with unilateral mesial temporal lobe epilepsy, is still widely used when bilateral independent temporal lobe seizures are suspected or when extratemporal foci cannot be ruled out by noninvasive means. Additionally, many epilepsy centers are reporting excellent surgical outcome in patients with neocortical temporal lobe epilepsy, when resections are guided by intracranial EEG studies. This article reviews the indications, technical aspects, risks, and interpretation of intracranial EEG in patients with temporal lobe seizures. It also considers intracranial EEG features predictive of surgical outcome.     

Synaptic damage underlies EEG abnormalities in postanoxic encephalopathy: A computational study

Objective

In postanoxic coma, EEG patterns indicate the severity of encephalopathy and typically evolve in time. We aim to improve the understanding of pathophysiological mechanisms underlying these EEG abnormalities.

Theta EEG dynamics of the error-related negativity.

OBJECTIVE: The error-related negativity (ERN) is a response-locked brain potential (ERP) occurring 80-100ms following response errors. This report contrasts three views of the genesis of the ERN, testing the classic view that time-locked phasic bursts give rise to the ERN against the view that the ERN arises from a pure phase-resetting of ongoing theta (4-7Hz) EEG activity and the view that the ERN is generated - at least in part - by a phase-resetting and amplitude enhancement of ongoing theta EEG activity. METHODS: Time-domain ERP analyses were augmented with time-frequency investigations of phase-locked and non-phase-locked spectral power, and inter-trial phase coherence (ITPC) computed from individual EEG trials, examining time courses and scalp topographies. Simulations based on the assumptions of the classic, pure phase-resetting, and phase-resetting plus enhancement views, using parameters from each subject's empirical data, were used to contrast the time-frequency findings that could be expected if one or more of these hypotheses adequately modeled the data. RESULTS: Error responses produced larger amplitude activity than correct responses in time-domain ERPs immediately following responses, as expected. Time-frequency analyses revealed that significant error-related post-response increases in total spectral power (phase- and non-phase-locked), phase-locked power, and ITPC were primarily restricted to the theta range, with this effect located over midfrontocentral sites, with a temporal distribution from approximately 150-200ms prior to the button press and persisting up to 400ms post-button press. The increase in non-phase-locked power (total power minus phase-locked power) was larger than phase-locked power, indicating that the bulk of the theta event-related dynamics were not phase-locked to response. Results of the simulations revealed a good fit for data simulated according to the phase-locking with amplitude enhancement perspective, and a poor fit for data simulated according to the classic view and the pure phase-resetting view. CONCLUSIONS: Error responses produce not only phase-locked increases in theta EEG activity, but also increases in non-phase-locked theta, both of which share a similar topography. SIGNIFICANCE: The findings are thus consistent with the notion advanced by Luu et al. [Luu P, Tucker DM, Makeig S. Frontal midline theta and the error-related negativity; neurophysiological mechanisms of action regulation. Clin Neurophysiol 2004;115:1821-35] that the ERN emerges, at least in part, from a phase-resetting and phase-locking of ongoing theta-band activity, in the context of a general increase in theta power following errors.     

Interictal EEG in temporal lobe epilepsy in childhood.

The authors clarified the value of interictal discharges and verified which extratemporal regions may also show epileptiform activity in temporal lobe epilepsy (TLE) in childhood. Thirty consecutive patients aged 3 to 18 years (mean age = 12.16 years; 16 male) with TLE associated with hippocampal atrophy were studied. Each patient had 1 to 15 interictal EEG recordings (mean: 5.6; total = 192 EEGs). Video-EEG monitoring was performed in 20 patients. All patients had MRI. The findings were compared with a control group of 53 consecutive TLE adult outpatients with hippocampal atrophy. Each adult patient underwent 3 to 21 routine EEGs (mean: 10.67; total = 566). Interictal EEGs of children with TLE showed extratemporal epileptiform discharges more frequently than EEGs of adults with TLE. Frontal, parietal, and occipital discharges were more frequently seen in children (P < 0.05). These results suggest a close interaction between temporal and other cerebral regions in children with epilepsy and provide further evidence of the existence of neural networks.     

Burst-suppression with identical bursts: A distinct EEG pattern with poor outcome in postanoxic coma

ObjectiveTo assess the incidence, quantified EEG characteristics, and prognostic significance of “burst-suppression with identical bursts” and to discuss potential pathophysiological mechanisms.MethodsBurst-suppression EEGs were identified from a cohort of 101 comatose patients after cardiac arrest, and from our complete database of 9600 EEGs, since 2005. Patterns with and without identical bursts were classified visually by two observers. Of patients after cardiac arrest, outcomes were assessed at three and six months. Identical and non-identical burst-suppression patterns were compared for quantified EEG characteristics and clinical outcome. Cross correlation of burstshape was applied to the first 500 ms of each burst.ResultsOf 9701 EEGs, 240 showed burst-suppression, 22 with identical bursts. Identical bursts were observed in twenty (20%) of 101 comatose patients after cardiac arrest between a median of 12 and 36 h after the arrest, but not in the six patients with other pathology than cerebral ischemia, or the 183 with anesthesia induced burst suppression. Inter-observer agreement was 0.8 and disagreement always resulted from sampling error. Burst-suppression with identical bursts was always bilateral synchronous, amplitudes were higher (128 vs. 25 μV, p = 0.0001) and correlation coefficients of burstshapes were higher (95% >0.75 vs. 0% >0.75, p < 0.0001) than in burst-suppression without identical bursts. All twenty patients with identical bursts after cardiac arrest had a poor outcome versus 10 (36%) without identical bursts.Conclusion“Burst-suppression with identical bursts” is a distinct pathological EEG pattern, which in this series only occurred after diffuse cerebral ischemia and was invariably associated with poor outcome.SignificanceIn comatose patients after cardiac arrest, “burst-suppression with identical bursts” predicts a poor outcome with a high specificity.     

The temporal dynamics of the stress response

This paper summarises the available evidence that failure of defense mechanisms in (semi)-natural social groups of animals may lead to serious forms of stress pathology. Hence the study of social stress may provide animal models with a high face validity. However, most of the animal models of human stress-disorders have concentrated on the consequences of chronic exposure to stressors. The present paper considers recent data, indicating that a single experience with a major stressor in the form of social defeat may have long-term consequences ranging from hours to days and weeks. It seems that the experience of a major stressor sensitizes the animal to subsequent stressors. The consequences of these long-term temporal dynamics of the stress response to the development of stress-related disorders and stress-vulnerability are discussed.     

Mental attributes and temporal brain dynamics during bargaining: EEG source localization and neuroinformatic mapping

It was previously shown by fMRI studies that unfair offers during an ultimatum bargaining game activate regions in the brain associated with emotions and conflict, leading to decisions inconsistent with standard economic theory. The temporal dynamics of emotional processing and mental attributes were not clear due to the coarse temporal resolution in those studies (～2 s). Here, the ultimatum game was studied by EEG recorded from the responders in 19 channels. EEG time series were first in-put to independent component analysis. An equivalent current dipole model was used to localize the sources of the independent components in EEGLAB. The Talairach coordinates of the dipoles were matched with references in the Brede neuroinformatics database. Dipole magnitudes, anatomical regions, and mental attributes were used to explain the rejection of the offers by applying multiple regression as a function of time in epochs with a median resolution of 250 ms. The results are consistent with previous studies regarding responder behavior and activated regions (e.g., anterior cingulate cortex, frontal gyrus, insular cortex). There are three main findings observed with the higher temporal resolution: (1) regression results from fine-scale temporal data showed activations not captured when the analysis was done by using time-averaged data; (2) temporal analysis detected the individual significant epochs and fluctuations (positive and negative correlations) in regions and for the associated mental attributes (e.g., reward/harm perception, anger, unfairness); (3) there was a sequential activation of anterior cingulate cortex and insular cortex, respectively, leading to the rejection response. Overall, regression models could explain a large percentage (～80%) of out-of-sample behavioral responses. The results are promising for the prospect of using EEG and source localization techniques in neuroeconomics to study finer temporal dynamics of neural activation.     

Mental attributes and temporal brain dynamics during bargaining: EEG source localization and neuroinformatic mapping

It was previously shown by fMRI studies that unfair offers during an ultimatum bargaining game activate regions in the brain associated with emotions and conflict, leading to decisions inconsistent with standard economic theory. The temporal dynamics of emotional processing and mental attributes were not clear due to the coarse temporal resolution in those studies (～2 s). Here, the ultimatum game was studied by EEG recorded from the responders in 19 channels. EEG time series were first in-put to independent component analysis. An equivalent current dipole model was used to localize the sources of the independent components in EEGLAB. The Talairach coordinates of the dipoles were matched with references in the Brede neuroinformatics database. Dipole magnitudes, anatomical regions, and mental attributes were used to explain the rejection of the offers by applying multiple regression as a function of time in epochs with a median resolution of 250 ms. The results are consistent with previous studies regarding responder behavior and activated regions (e.g., anterior cingulate cortex, frontal gyrus, insular cortex). There are three main findings observed with the higher temporal resolution: (1) regression results from fine-scale temporal data showed activations not captured when the analysis was done by using time-averaged data; (2) temporal analysis detected the individual significant epochs and fluctuations (positive and negative correlations) in regions and for the associated mental attributes (e.g., reward/harm perception, anger, unfairness); (3) there was a sequential activation of anterior cingulate cortex and insular cortex, respectively, leading to the rejection response. Overall, regression models could explain a large percentage (～80%) of out-of-sample behavioral responses. The results are promising for the prospect of using EEG and source localization techniques in neuroeconomics to study finer temporal dynamics of neural activation.     

Seizure semiology in temporal lobe vs. temporal plus epilepsy using intracranial EEG monitoring

Objectives:To utilize our tertiary center’s experience with Temporal lobe epilepsy (TLE) and Temporal plus epilepsy (TPE) cases and determine whether a correlation exists between ictal semiology signs, their localization/lateralization value after intracranial electroencephalography (EEG) monitoring, and surgical outcomes.Methods:A retrospective study was conducted among epilepsy patients who underwent resective surgery for TLE or TPE after intracranial EEG monitoring between January 2008 and December 2018 at King Faisal Specialist Hospital in Riyadh, Saudi Arabia. Data were retrieved for 464 patients; 181 had intracranial electrode monitoring.Results:Forty-eight patients with a mean age of 27 years (SD=8.4) were included; 15 patients had TPE. Auras were frequently reported, emotional auras, in the form of fear (35%). The localization/lateralization value of aura was statistically significant for TPE patients, including visual hallucinations and vertigo, lateralized to the left and right temporo-occipital, respectively (p=0.009 and <0.001). Early-onset ictal manual automatism, oral automatism, late-onset dystonic posture, and late head-turning were significant for TLE without significant lateralization value. The ictal onset zone’s localization was significant between the scalp and intracranial EEG findings in mesial TLE patients. The probability of seizure freedom (Engel class I) was 74%, 60%, and 67% at 2-year follow-up for mesial, lateral TLE, and TPE, respectively.Conclusion:Our results are consistent with previous studies and confirm the importance of ictal semiology signs in TLE and TPE. The addition of intracranial EEG monitoring in these cases helped improve the surgical outcomes.

Epilepsy is one of the most common neurological disorders, affecting approximately 70 million people globally.¹ Thirty percent of these patients have drug-resistant epilepsy,² and most cases referred for epilepsy surgery involve temporal lobe epilepsy (TLE).³ However, after standard temporal lobectomy, around 40% of these patients will experience recurrent seizures.⁴ A variety of explanations have been proposed for these surgical failures, including incomplete removal of the epileptogenic zone, additional contralateral focus (bilateral TLE), dual pathology (mesial and neocortical), and extended epileptogenic focus to the neighboring structures, including extratemporal or temporal plus epilepsy (TPE).⁵The TPE is defined as focal epilepsy with a complex epileptogenic network involving the temporal lobe and the surrounding areas, such as the orbitofrontal cortex, insula, operculum, and temporo-parieto-occipital junction.⁶ A thorough presurgical evaluation is required to delineate the epileptogenic zone for successful resective surgery. In phase I assessment, scalp video electroencephalography (EEG) monitoring, brain magnetic resonance imaging (MRI), and neuropsychological evaluation are needed. Further non-invasive investigations can be included if the initial results are discordant. To reach a well-demarcated epileptogenic focus requires intracranial monitoring, including the subdural grid, strips, and depth, which is known as phase II assessment.⁷ Seizure semiology is the first step in a presurgical evaluation, and ictal semiology and scalp-EEG results play a valuable role in distinguishing TLE from TPE.⁸ Patients with TLE are more likely to experience abdominal auras, ictal gestural automatism, and post-ictal amnesia. However, TPE patients are more likely to experience gustatory hallucinations, rotatory vertigo, auditory illusions, contralateral eye and head versions, piloerection, and ipsilateral tonic posturing. Similar findings were highlighted in a review of TPE cases.4 Furthermore, laryngeal and throat constriction and the atypical distribution of somatosensory symptoms at seizure onset have been found.4Although some studies have found a correlation between seizure semiology and intracranial EEG monitoring in TLE (mesial vs. lateral) vs. TPE, none evaluated lateralization values. This study aims to utilize our tertiary center’s experience with TLE and TPE cases and determine whether a correlation exists between ictal semiology signs, their localization/lateralization value after intracranial electroencephalography (EEG) monitoring and surgical outcomes. We also highlight the process of phase I presurgical assessment (including ictal/interictal scalp EEG, MRI, positron emission tomography [PET], and neuropsychology) in our center.     

The anterior temporal electrode in the EEG of the adult

The anterior temporal cerebral region is not well covered, electroencephalographically, by the usual EEG electrodes. Numerous attempts have been made to add anterior temporal electrodes. There has been discussion regarding the amount of additional information actually attributable to those electrodes. We systematically evaluated the abnormalities revealed by one such noninvasive set of anterior temporal electrodes, D. Silverman's T1 and T2. A total of 624 consecutive EEGs were reviewed. We conclude that, in the adult, anterior temporal electrodes can add significantly to the information contained in the routine interictal EEG.     

A case of area-specific stimulus-sensitive postanoxic myoclonus.

The authors report a case of area-specific stimulus-sensitive postanoxic myoclonus and discuss possible pathophysiology. A 71-year-old man sustained cardiorespiratory arrest that lasted 10 minutes and remained unresponsive. On the first EEG obtained 8 hours after the arrest there was no cerebral electrical activity before stimulation of the trigeminal-innervated areas. Periorbital stimulation was associated with bursts of spike-wave activity and generalized myoclonic jerks, whereas other types of stimulation did not elicit any response. A second EEG obtained 32 hours later showed a nonreactive alpha coma pattern. The patient died 7 days after the arrest. Area-specific stimulus-sensitive postanoxic myoclonus is very rare. The regularity of generalized bursts of spike-wave activity (cortical response) in response to stimulation of trigeminal-innervated areas suggests that the resting EEG electrocerebral silence may have been a result of cortical suppression with disinhibition of stimulus-sensitive brainstem-generated myoclonus.     

Rapid postanoxic calcification of the basal ganglia.

A 22-year-old male diabetic on hemodialysis suffered a cerebral anoxic event. Serial CT showed the development of basal ganglia calcification over a period of no more than 17 days. It appears that the basal ganglia may develop petechial hemorrhage, necrosis, calcification, or combinations of these following an anoxic insult. The neuropathologic substrate and mechanism of rapid postanoxic calcification are unknown.