Prognostic value of early electrographic biomarkers of epileptogenesis in high-risk ischaemic stroke patients.

BACKGROUND AND PURPOSE: Post-stroke epilepsy (PSE) is frequent. Better prediction of PSE would enable individualized management and improve trial design for epilepsy prevention. The aim was to assess the complementary value of continuous electroencephalography (EEG) data during the acute phase compared with clinical risk factors currently used to predict PSE. METHODS: A prospective cohort of 81 patients with ischaemic stroke who received early continuous EEG monitoring was studied to assess the association of early EEG seizures, other highly epileptogenic rhythmic and periodic patterns, and regional attenuation without delta (RAWOD, an EEG pattern of stroke severity) with PSE. Clinical risk factors were investigated using the SeLECT (stroke severity; large-artery atherosclerosis; early clinical seizures; cortical involvement; territory of middle cerebral artery) scores. RESULTS: Twelve (15%) patients developed PSE. The presence of any of the investigated patterns was associated with a risk of epilepsy of 46%, with a sensitivity and specificity of 83% and 78%. The association remained significant after adjusting for the SeLECT score (odds ratio 18.8, interquartile range 3.8-72.7). CONCLUSIONS: It was found that highly epileptogenic rhythmic and periodic patterns and RAWOD were associated with the development of PSE and complemented clinical risk factors. These findings indicate that continuous EEG provides useful information to determine patients at higher risk of developing PSE and could help individualize care.

Case report: Invasive neuromonitoring in status epilepticus induced hypoxic ischemic brain injury.

Objectives: Literature on invasive neuromonitoring and bilateral decompressive craniectomies (BDC) in patients with refractory status epilepticus (RSE)-mediated hypoxic-ischemic brain injury (HIBI) is limited. Neuromonitoring can guide decision making and treatment escalation. Methods and results: We report a case of a 17 years-old male who was admitted to our hospital's intensive care unit for RSE. HIBI was detected on neuroimaging on this patient's second day of admission after he developed central diabetes insipidus (DI). Invasive neuromonitoring revealed raised intracranial pressure (ICP) and brain hypoxia as measured by reduced brain tissue oxygen tension (PbtO2). Treatments were escalated in a tiered fashion, including administration of hyperosmolar agents, analgesics, sedatives, and a neuromuscular blocking drug. Eventually, BDC was performed as a salvage therapy as a means of controlling refractory ICP crisis in the setting of diffuse cerebral edema (DCE) following HIBI. Discussion: SE-mediated HIBI can result in refractory ICP crisis. Neuromonitoring can help identify secondary brain injury (SBI), guide treatment strategies, including surgical interventions, and may lead to better outcomes.

Optimizing Electrode Configurations for Wearable EEG Seizure Detection Using Machine Learning.

Epilepsy, a prevalent neurological disorder, profoundly affects patients' quality of life due to the unpredictable nature of seizures. The development of a reliable and user-friendly wearable EEG system capable of detecting and predicting seizures has the potential to revolutionize epilepsy care. However, optimizing electrode configurations for such systems, which is crucial for balancing accuracy and practicality, remains to be explored. This study addresses this gap by developing a systematic approach to optimize electrode configurations for a seizure detection machine-learning algorithm. Our approach was applied to an extensive database of prolonged annotated EEG recordings from 158 epilepsy patients. Multiple electrode configurations ranging from one to eighteen were assessed to determine the optimal number of electrodes. Results indicated that the performance was initially maintained as the number of electrodes decreased, but a drop in performance was found to have occurred at around eight electrodes. Subsequently, a comprehensive analysis of all eight-electrode configurations was conducted using a computationally intensive workflow to identify the optimal configurations. This approach can inform the mechanical design process of an EEG system that balances seizure detection accuracy with the ease of use and portability. Additionally, this framework holds potential for optimizing hardware in other machine learning applications. The study presents a significant step towards the development of an efficient wearable EEG system for seizure detection.

Ellen R. Grass Lecture: Disparities in Access to Neurodiagnostic Testing.

Limited access to EEG services in rural areas creates health disparities in neurological care, including unnecessary transfers and delays in diagnosis and treatment. Rural facilities face several challenges to expanding EEG resources, including a lack of neurologists, technologists, EEG equipment, and adequate IT infrastructure. Potential solutions include investment in innovative technology, expansion of the workforce, and development of hub-and-spoke EEG networks. Bridging the EEG gap requires collaboration between academic and community practices to advance practical technologies, train competent personnel and develop cost-effective resource-sharing strategies.

Power spectrum analysis and outcomes of non-convulsive status epilepticus: a single-center study.

OBJECTIVES: Diagnosis of non-convulsive status epilepticus (NCSE) is challenging and outcomes during follow-up are not clear. This study aimed to conduct power spectrum analysis in NCSE and measure outcomes of patients. METHODS: We searched continuous EEG monitoring (cEEG) recordings to identify patients of NCSE. An artifact-free cEEG epoch of continuous 60 s was chosen for spectral power analysis. We also collected electronic medical records of the patients for extracting clinical information. Patients recruited were followed up at least every half a year. RESULTS: There were 48 patients with 64 independent NCSE episodes during different course of disease recruited in the study, with a mean age of 40.3 ± 19.1 years (range, 12-72 years), including 24 males (50%) and 24 females (50%). When the spectral power of 60 s equaled to 11.30 µV2 for predicting impairment of consciousness, (sensitivity, specificity) = (0.979, 0.625). When the spectral power of 60 s equaled to 52.70 µV2 for predicting myoclonic jerks, (sensitivity, specificity) = (0.783, 0.756). There were 27 patients (56.3%) followed up with a duration over 12 months. Nineteen patients (70.4%) continued to have seizures. Eleven (40.7%) resisted to at least two kinds of appropriate anti-seizure medication at maximum tolerated levels. Five patients with prolonged NCSE suffered from loss of brain parenchymal volume on follow-up MRI scans. CONCLUSION: Spectral power analysis can be used to detect mental status and limb jerks. Early diagnosis and treatment of NCSE are important, which can influence outcomes of the patients during follow-up.

Serum neuron-specific enolase: a new tool for seizure risk monitoring after status epilepticus.

BACKGROUND AND PURPOSE: There is a need for accurate biomarkers to monitor electroencephalography (EEG) activity and assess seizure risk in patients with acute brain injury. Seizure recurrence may lead to cellular alterations and subsequent neurological sequelae. Whether neuron-specific enolase (NSE) and S100-beta (S100B), brain injury biomarkers, can reflect EEG activity and help to evaluate the seizure risk was investigated. METHODS: Eleven patients, admitted to an intensive care unit for refractory status epilepticus, who underwent a minimum of 3 days of continuous EEG concomitantly with daily serum NSE and S100B assays were included. At 103 days the relationships between serum NSE and S100B levels and two EEG scores able to monitor the seizure risk were investigated. Biochemical biomarker thresholds able to predict seizure recurrence were sought. RESULTS: Only NSE levels positively correlated with EEG scores. Similar temporal dynamics were observed for the time courses of EEG scores and NSE levels. NSE levels above 17 ng/ml were associated with seizure in 71% of patients. An increase of more than 15% of NSE levels was associated with seizure recurrence in 80% of patients. CONCLUSIONS: Our study highlights the potential of NSE as a biomarker of EEG activity and to assess the risk of seizure recurrence.

Etiology and prognostic significance of ictal EEG patterns in patients with non-convulsive seizures.

We aimed to study the ictal EEG patterns in patients with non-convulsive seizures (NCS) and their relationship with underlying etiology and patient outcome. We conducted a retrospective review of EEG studies from patients undergoing continuous EEG (cEEG) monitoring for indication of altered mental status with a suspicion of NCS. Ictal EEG findings of NCS were categorized as three patterns: focal or generalized epileptiform discharges (EDs) at frequencies >2.5 Hz (Pattern 1); EDs at frequencies of ≤2.5 Hz or rhythmic activity >0.5 Hz with spatiotemporal evolution (Pattern 2); and EDs with ≤2.5 Hz with subtle clinical correlate during the ictal EEG or clinical and EEG improvement after a trial of IV anti-seizure drugs (Pattern 3). Patients with anoxic brain injury were excluded from the study. Associations between ictal EEG patterns and underlying etiology and their impact on in-hospital mortality was measured. Of 487 patients included in the study, NCS was recorded on cEEG monitoring in 57 (12%). The ictal EEG Pattern 2 was the most commonly seen ictal EEG finding in our cohort of patients with NCS (70%, n=40/57), followed by Pattern 3 (15%, n=9/57) and Pattern 1(14%, n=8/57). In patients with acute brain injury, Pattern 2 (67%, n=27/40) was a commonly seen ictal EEG finding, whereas Pattern 1 (62% n=5/8) was seen in patients with underlying acute medical illness. No statistically significant difference was found between ictal EEG patterns and underlying neurological versus medical etiologies (p=0.27) or in-hospital mortality (p=0.5). Spatiotemporal evolution of epileptiform discharges at a lower frequency was the most commonly recorded ictal EEG pattern in our cohort. Further prospective studies with a larger sample size of patients with NCS may provide valuable clinical data that could be used to evaluate the etiologic correlate of the various ictal EEG patterns and their effect on outcome.

Neurocritical Care and Brain Monitoring.

The goal of neurocritical care (NCC) is to improve the outcome of patients with neurologic insults. NCC includes the management of the primary brain injury and prevention of secondary brain injury; this is achieved with standardized clinical care for specific disorders along with neuromonitoring. Neuromonitoring uses multiple modalities, with certain modalities better suited to certain disorders. The term "multimodality monitoring" refers to using multiple modalities at the same time. This article reviews pediatric NCC, the various physiologic parameters used, especially continuous electroencephalographic monitoring.

Periodic electroclinical seizures following an ischemic stroke revealed by continuous-EEG.

BACKGROUND: Periodic EEG patterns are mostly associated with critical illnesses and acute disruptions of the central nervous system. Periodic or cyclic seizures are extremely rare phenomena, most of which are nonconvulsive, only reported in critically ill patients. Here we report a patient with periodic focal impaired awareness seizures following a minor stroke and address possible pathophysiological mechanisms. CASE: A 49 years old male patient presented with periodic seizures, associated with an acute stroke in the left occipital and parietal regions. These focal seizures, recorded during long-term video-EEG monitoring in the scalp EEG, appeared every 9-11 min, and responded to iv valproic acid treatment but not to iv treatments of diazepam, phenytoin, and levetiracetam. DISCUSSION: We believe that the blood-brain barrier disruption due to stroke, in conjunction with hyperglycemia and antiphospholipid antibodies have led to an imbalance of the surrounding tissue and sustained hyperexcitability to a point of pacemaker potentials. It is tempting to speculate that repetitive cycles of cortical spreading depression due to tissue injury have aided the periodicity of the seizures. CONCLUSION: Continuous EEG monitoring is crucial, not only to diagnose and appropriately treat accompanying subtle seizures but also to further understand the underlying intriguing pathophysiological processes like periodicity.

Continuous EEG monitoring in the follow-up of convulsive status epilepticus patients: A proposal and preliminary validation of an EEG-based seizure build-up score (EaSiBUSSEs).

Continuous electroencephalography (EEG) is a major tool for monitoring patients admitted to the intensive care unit after refractory convulsive status epilepticus, following control of convulsive movements. We review the values of different EEG patterns observed in critically ill patients for prognosis and seizure risk, together with proposed criteria for non-convulsive status epilepticus diagnosis (Salzburg Criteria), the EEG scores for prognosis (Epidemiology-based Mortality score in Status Epilepticus, EMSE) and for seizure risk (2HELPS2B). These criteria and scores, based partially on continuous EEG, are not tailored to repetitively monitor the progressive build-up leading to seizure or status epilepticus recurrence. Therefore, we propose a new EEG-based seizure build-up score in status epilepticus (EaSiBUSSEs), based on the morphology and the prevalence of the EEG patterns observed in the follow-up of convulsive status epilepticus patients. It displays subscores from the least (no interictal activity) to the most associated with seizures (focal or generalized status epilepticus). We then evaluated the performance of the EaSiBUSSEs in a cohort of eleven patients who were admitted to intensive care unit for convulsive status epilepticus and who underwent continuous EEG recording. The receiver operating curve revealed good accuracy in identifying patients who would have seizures in the next 24 h, with excellent intra- and inter-rater reliability. We believe that this score is simple to perform, and suitable for repeated monitoring of EEG following refractory convulsive status epilepticus, with quantitative description of major EEG changes leading to seizures.

Electroencephalography Technologist Inter-rater Agreement and Interpretation of Pediatric Critical Care Electroencephalography.

OBJECTIVES: Electroencephalography (EEG) technologists commonly screen continuous EEG. Until now, the inter-rater agreement or sensitivity for important EEG findings has been unknown in this group. METHODS: Twenty-nine EEG technologists and three clinical neurophysiologists interpreted 90 five-minute samples of pediatric critical care EEG. Inter-rater agreement was examined with Cohen's kappa and Fleiss' kappa for EEG findings. A gold-standard consensus agreement was developed for examining sensitivity and specificity for seizures or discontinuity. Kruskal-Wallis tests with Benjamani-Hochberg corrections for multiple comparisons were utilized to examine associations between correct scoring and certification status and years of experience. RESULTS: Aggregate agreement was moderate for seizures and fair for EEG background continuity among EEG technologists. Individual agreement for seizures and continuity varied from slight to substantial. For individual EEG technologists, sensitivity for seizures ranged from 44 to 93% and sensitivity for continuity ranged from 81 to 100%. Raters with Certified Long Term Monitoring credentials were more likely to identify seizures correctly. SIGNIFICANCE: This is the first study to evaluate inter-rater agreement and interpretation correctness among EEG technologists interpreting pediatric critical care EEG. EEG technologists demonstrated better aggregate agreement for seizure detection than other EEG findings, yet individual results and internal consistency varied widely. These data provide important insight into the common practice of utilizing EEG technologists for screening critical care EEG.

A standardized nomenclature for spectrogram EEG patterns: Inter-rater agreement and correspondence with common intensive care unit EEG patterns.

OBJECTIVE: To determine the inter-rater agreement (IRA) of a standardized nomenclature for EEG spectrogram patterns, and to estimate the probability distribution of ictal-interictal continuum (IIC) patterns vs. other EEG patterns within each category in this nomenclature. METHODS: We defined seven spectrogram categories: "Solid Flames", "Irregular Flames", "Broadband-monotonous", "Narrowband-monotonous", "Stripes", "Low power", and "Artifact". Ten electroencephalographers scored 115 spectrograms and the corresponding raw EEG samples. Gwet's agreement coefficient was used to calculate IRA. RESULTS: Solid Flames represented seizures or IIC patterns 69.4% of the time. Irregular Flames represented seizures or IIC patterns 38.7% of the time. Broadband-monotonous primarily corresponded with seizures or IIC (54.3%) and Narrowband-monotonous with focal or generalized slowing (43.8%). Stripes were associated with burst-suppression (37.2%) and generalized suppression (34.4%). Low Power category was associated with generalized suppression (94%). There was "near perfect" agreement for Solid Flames (κ = 94.36), Low power (κ = 92.61), and Artifact (κ = 93.72). There was "substantial agreement" for all other categories (κ = 74.65-79.49). CONCLUSIONS: This EEG spectrogram nomenclature has high IRA among electroencephalographers. SIGNIFICANCE: The nomenclature can be a useful tool for EEG screening. Future studies are needed to determine if using this nomenclature shortens time to IIC identification, and how best to use it in practice to reduce time to intervention.

Validation of an algorithm of time-dependent electro-clinical risk stratification for electrographic seizures (TERSE) in critically ill patients.

OBJECTIVE: The clinical implementation of continuous electroencephalography (CEEG) monitoring in critically ill patients is hampered by the substantial burden of work that it entails for clinical neurophysiologists. Solutions that might reduce this burden, including by shortening the duration of EEG to be recorded, would help its widespread adoption. Our aim was to validate a recently described algorithm of time-dependent electro-clinical risk stratification for electrographic seizure (ESz) (TERSE) based on simple clinical and EEG features. METHODS: We retrospectively reviewed the medical records and EEG recordings of consecutive patients undergoing CEEG between October 1, 2015 and September, 30 2016 and assessed the sensitivity of TERSE for seizure detection, as well as the reduction in EEG time needed to be reviewed. RESULTS: In a cohort of 407 patients and compared to full CEEG review, the model allowed the detection of 95% of patients with ESz and 97% of those with electrographic status epilepticus. The amount of CEEG to be recorded to detect ESz was reduced by two-thirds, compared to the duration of CEEG taht was actually recorded. CONCLUSIONS: TERSE allowed accurate time-dependent ESz risk stratification with a high sensitivity for ESz detection, which could substantially reduce the amount of CEEG to be recorded and reviewed, if applied prospectively in clinical practice. SIGNIFICANCE: Time-dependent electro-clinical risk stratification, such as TERSE, could allow more efficient practice of CEEG and its more widespread adoption. Future studies should aim to improve risk stratification in the subgroup of patients with acute brain injury and absence of clinical seizures.

Electrographic seizures and ictal-interictal continuum (IIC) patterns in critically ill patients.

Critical care long-term continuous electroencephalogram (cEEG) monitoring has expanded dramatically in the last several decades spurned by technological advances in EEG digitalization and several key clinical findings: 1-Seizures are relatively common in the critically ill-large recent observational studies suggest that around 20% of critically ill patients placed on cEEG have seizures. 2-The majority (~75%) of patients who have seizures have exclusively "electrographic seizures", that is, they have no overt ictal clinical signs. Along with the discovery of the unexpectedly high incidence of seizures was the high prevalence of EEG patterns that share some common features with archetypical electrographic seizures but are not uniformly considered to be "ictal". These EEG patterns include lateralized periodic discharges (LPDs) and generalized periodic discharges (GPDs)-patterns that at times exhibit ictal-like behavior and at other times behave more like an interictal finding. Dr. Hirsch and colleagues proposed a conceptual framework to describe this spectrum of patterns called the ictal-interictal continuum (IIC). In the following years, investigators began to answer some of the key pragmatic clinical concerns such as which patients are at risk of seizures and what is the optimal duration of cEEG use. At the same time, investigators have begun probing the core questions for critical care EEG-what is the underlying pathophysiology of these patterns, at what point do these patterns cause secondary brain injury, what are the optimal treatment strategies, and how do these patterns affect clinical outcomes such as neurological disability and the development of epilepsy. In this review, we cover recent advancements in both practical concerns regarding cEEG use, current treatment strategies, and review the evidence associating IIC/seizures with poor clinical outcomes.

Diagnostic Value of Electroencephalography with Ten Electrodes in Critically Ill Patients.

BACKGROUND: In critical care settings, electroencephalography (EEG) with reduced number of electrodes (reduced montage EEG, rm-EEG) might be a timely alternative to the conventional full montage EEG (fm-EEG). However, past studies have reported variable accuracies for detecting seizures using rm-EEG. We hypothesized that the past studies did not distinguish between differences in sensitivity from differences in classification of EEG patterns by different readers. The goal of the present study was to revisit the diagnostic value of rm-EEG when confounding issues are accounted for. METHODS: We retrospectively collected 212 adult EEGs recorded at Massachusetts General Hospital and reviewed by two epileptologists with access to clinical, trending, and video information. In Phase I of the study, we re-configured the first 4 h of the EEGs in lateral circumferential montage with ten electrodes and asked new readers to interpret the EEGs without access to any other ancillary information. We compared their rating to the reading of hospital clinicians with access to ancillary information. In Phase II, we measured the accuracy of the same raters reading representative samples of the discordant EEGs in full and reduced configurations presented randomly by comparing their performance to majority consensus as the gold standard. RESULTS: Of the 95 EEGs without seizures in the selected fm-EEG, readers of rm-EEG identified 92 cases (97%) as having no seizure activity. Of 117 EEGs with "seizures" identified in the selected fm-EEG, none of the cases was labeled as normal on rm-EEG. Readers of rm-EEG reported pathological activity in 100% of cases, but labeled them as seizures (N = 77), rhythmic or periodic patterns (N = 24), epileptiform spikes (N = 7), or burst suppression (N = 6). When the same raters read representative epochs of the discordant EEG cases (N = 43) in both fm-EEG and rm-EEG configurations, we found high concordance (95%) and intra-rater agreement (93%) between fm-EEG and rm-EEG diagnoses. CONCLUSIONS: Reduced EEG with ten electrodes in circumferential configuration preserves key features of the traditional EEG system. Discrepancies between rm-EEG and fm-EEG as reported in some of the past studies can be in part due to methodological factors such as choice of gold standard diagnosis, asymmetric access to ancillary clinical information, and inter-rater variability rather than detection failure of rm-EEG as a result of electrode reduction per se.

Optimizing seizure detection by quantitative EEG in paediatric refractory status epilepticus

@#Background & Objective: Continuous electroencephalography (cEEG) is valuable in the diagnosis and management of refractory status epilepticus (RSE) but requires intensive skilled interpretation. Density spectral array (DSA) is a quantitative analytic tool used to screen cEEG recordings for seizures. This study aims to determine the optimal amplitude setting and to compare the use of single-averagetrendgraph display and eight-trendgraph display in seizure detection with DSA. Methods: Five excerpts from pediatric cEEG recordings with RSE were identified. In Phase 1 of the study, each of 4 readers determined the DSA amplitude setting one most preferred for each excerpt, and marked all seizures in one excerpt using one’s preferred setting. Inter-rater agreement in seizure detection was measured. In Phase 2, readers marked all seizures in all excerpts, first using single-average-trendgraph display, and then using eight-trendgraph display after a wash-out period. Intra-rater agreement in seizure detection between the two display methods was calculated. Results: In Phase 1, DSA readers’ choice of preferred amplitude settings varied widely but inter-rater agreement in seizure detection was high. In Phase 2, seizure detection using single- and eight-trendgraph displays showed high agreement with each other and, where they disagreed, single-average-trendgraph was more sensitive. Additionally, low seizure-to-background amplitude ratio in EEG recordings was associated with worse detection sensitivity/specificity. Conclusions: DSA amplitude settings do not affect seizure detection. Single-trendgraph display is comparable to eight-trendgraph display in screening cEEG for seizures. Seizure detection with DSA performs better in cEEG recordings with high seizure-to-background amplitude ratio.

Monitoring for seizures in the intensive care unit.

Acute symptomatic seizures have been known to occur in critically ill patients for many years. It was not until the widespread use of continuous EEG (cEEG) in the critically ill did we appreciate the incidence of electrographic seizures and status epilepticus in the ICU (Newey and Kinzy, 2018). Many of the seizures that occur are without any apparent clinical signs at the time of the recording. The patients often have convulsive seizures at onset then over the next few hours they lose the ability to have a generalized tonic clonic convulsion. They may then have subtle clinical signs (ictal nystagmus, facial twitching, etc.) or lose any apparent motor response. The end result is that many of the patients lose any clinical signs for their seizures by the time they are in the ICU and their seizures are termed "nonconvulsive." The recognition of seizures in the ICU is important for the effects the seizures have on outcome, particularly in morbidity and mortality and the risk of developing epilepsy after the acute symptomatic event. The use of cEEG in the ICU population has not only highlighted the high incidence of seizure activity but has also been used to assess overall cerebral function with applications in ischemia monitoring and prognostication, and to assess the degree of encephalopathy. This chapter will illustrate the core principles of cEEG monitoring in the critical care population including the incidence of seizures, determining who is at highest risk for seizures, how long patients should be monitored and ICU EEG seizure.

Bilateral independent periodic discharges are associated with electrographic seizures and poor outcome: A case-control study.

OBJECTIVE: To determine the clinical correlates bilateral independent periodic discharges (BIPDs) and their association with electrographic seizures and outcome. METHODS: Retrospective case-control study of patients with BIPDs compared to patients without periodic discharges ("No PDs") and patients with lateralized periodic discharges ("LPDs"), matched for age, etiology and level of alertness. RESULTS: We included 85 cases and 85 controls in each group. The most frequent etiologies of BIPDs were stroke, CNS infections, and anoxic brain injury. Acute bilateral cerebral injury was more common in the BIPDs group than in the No PDs and LPDs groups (70% vs. 37% vs. 35%). Electrographic seizures were more common with BIPDs than in the absence of PDs (45% vs. 8%), but not than with LPDs (52%). Mortality was higher in the BIPDs group (36%) than in the No PDs group (18%), with fewer patients with BIPDs achieving good outcome (moderate disability or better; 18% vs. 36%), but not than in the LPDs group (24% mortality, 26% good outcome). In multivariate analyses, BIPDs remained associated with mortality (OR: 3.0 [1.4-6.4]) and poor outcome (OR: 2.9 [1.4-6.2]). CONCLUSION: BIPDs are caused by bilateral acute brain injury and are associated with a high risk of electrographic seizures and of poor outcome. SIGNIFICANCE: BIPDs are uncommon but their identification in critically ill patients has potential important implications, both in terms of clinical management and prognostication.

Clinical Correlates of Periodic Discharges and Nonconvulsive Seizures in Posterior Reversible Encephalopathy Syndrome (PRES).

IMPORTANCE: The pathophysiological mechanisms of Posterior Reversible Encephalopathy Syndrome (PRES) and related seizures remain poorly understood. The prevalence and clinical significance of nonconvulsive seizures (NCSz) and related epileptiform patterns during continuous electroencephalography monitoring (CEEG) in PRES have not been well described. OBJECTIVE: To report the prevalence, characteristics and risk factors for NCSz and related highly epileptiform patterns in patients with PRES, and to determine their relation to imaging abnormalities and outcome. DESIGN, SETTING AND PARTICIPANTS: From a prospective CEEG database, we retrospectively identified patients with PRES and reviewed their medical charts. Based on CEEG findings, we designed a retrospective cohort study comparing two groups defined based on the presence or the absence of NCSz and/or periodic discharges (PDs). MAIN OUTCOMES AND MEASURES: The prevalence and risk factors for PDs and NCSz, description of EEG and magnetic resonance imaging (MRI) abnormalities and functional outcome as measured by the Glasgow Outcome Scale (GOS) at hospital discharge. RESULTS: Among 37 eligible patients, 23 (62%) had PDs or NCSz. The presence of NCSz was associated with the presence of PDs (15/22 vs. 1/15; p = 0.0002). NCSz and PDs were usually either lateralized or bilateral independent and predominated in the posterior regions. No clinical features were associated with the occurrence of PDs or NCSz. Cortical restricted diffusion on MRI was more frequent in the PDs/NCSz group (17/23 vs. 1/14; p < 0.001). PDs/NCSz were associated with worse outcome, with 3 deaths vs. 0 in the no PDs/NCSz group and fewer cases with low disability (4 vs. 9 cases with GOS = 5, p < 0.04). CONCLUSIONS AND RELEVANCE: Our results reveal a high prevalence of NCSz and PDs in critically ill patients with PRES and an association with restricted diffusion and worse outcome, whether treating or preventing these EEG findings can improve outcome requires further research.

Time to epileptiform activity and EEG background recovery are independent predictors after cardiac arrest.

OBJECTIVE: Investigate the temporal development of EEG and prognosis. METHODS: Prospective observational substudy of the Target Temperature Management trial. Six sites performed simplified continuous EEG-monitoring (cEEG) on comatose patients after cardiac arrest, blinded to treating physicians. We determined time-points of recovery of a normal-voltage continuous background activity and the appearance of an epileptiform EEG, defined as abundant epileptiform discharges, periodic/rhythmic discharges or electrographic seizure activity. RESULTS: 134 patients were included, 65 had a good outcome. Early recovery of continuous background activity (within 24 h) occurred in 72 patients and predicted good outcome since 55 (76%) had good outcome, increasing the odds for a good outcome seven times compared to a late background recovery. Early appearance of an epileptiform EEG occurred in 38 patients and 34 (89%) had a poor outcome, increasing the odds for a poor outcome six times compared to a late debut. The time to background recovery and the time to epileptiform activity were highly associated with outcome and levels of neuron-specific enolase. Multiple regression analysis showed that both variables were independent predictors. CONCLUSIONS: Time to epileptiform activity and background recovery are independent prognostic indicators. SIGNIFICANCE: Patients with early background recovery combined with late appearance of epileptiform activity may have a good outcome.