Nonconvulsive status epilepticus and the postictal state

Outpatient management of prolonged seizures and seizure clusters to prevent progression to a higher-level emergency: Consensus recommendations of an expert working group

OBJECTIVE

The management of prolonged seizures (PS) and seizure clusters (SC) is impeded by the lack of international, evidence-based guidance. We aimed to develop expert recommendations regarding consensus definitions of PS, SC, and treatment goals to prevent progression to higher-level emergencies such as status epilepticus (SE).

METHODS

An expert working group, comprising 12 epileptologists, neurologists, and pharmacologists from Europe and North America, used a modified Delphi consensus methodology to develop and anonymously vote on statements. Consensus was defined as ≥75% voting "Agree"/"Strongly agree."

RESULTS

All group members strongly agreed that termination of an ongoing seizure in as short a time as possible is the primary goal of rapid and early seizure termination (REST) and that an ideal medication for REST would start to act within 2 min of administration to terminate ongoing seizure activity. Consensus was reached on the terminology defining PS (with proposed thresholds of 5 min for prolonged focal seizures and 2 min for prolonged absence seizures and the convulsive phase of bilateral tonic-clonic seizures) and SC (an abnormal increase in seizure frequency compared with the individual patient's usual seizure pattern). All group members strongly agreed or agreed that patients who have experienced a PS should be offered a REST medication, and all patients who have experienced a SC should be offered an acute cluster treatment (ACT). Further, when prescribing a REST medication or ACT, a seizure action plan should be agreed upon in consultation with the patient and caregiver.

SIGNIFICANCE

The expert working group had a high level of agreement on the recommendations for defining and managing PS and SC. These recommendations will complement the existing guidance for the management of acute seizures, with the possibility of treating them earlier to potentially avoid progression to more severe seizures, including SE.

Ictal Cotard delusion as a manifestation of nonconvulsive status epilepticus: A case report and commentary

Psychosis of epileptic origin can present a wide range of cognitive and affective symptoms and is often underrecognized. Usually occurring in the inter- and postictal phase, epileptic psychosis is mostly related to temporal lobe epilepsy. Here, we describe the clinical presentation and diagnostic workup including routine EEG recording and brain MRI of a 63-year-old woman expressing isolated nihilistic delusions comprising belief of being dead and denial of self-existence. EEG showed an ictal pattern fulfilling the Salzburg criteria of nonconvulsive status epilepticus and brain MRI revealed extensive peri-ictal hyperperfusion. Delusional symptoms and EEG abnormalities subsided after acute antiseizure treatment. Our case illustrates how nihilistic delusions can occur as a direct clinical correlate of seizure activity, thereby expanding the spectrum of ictal neuropsychiatric phenomena in temporal lobe epilepsy and highlighting the need to consider an epileptic origin in patients presenting with psychotic symptoms.

Factors affecting seizure recurrence in the emergency department

Background

Information on Emergency Department (ED) follow-up of patients presenting with epileptic seizures is limited.

Objectives

It was planned to investigate the factors affecting the recurrence of epileptic seizures in the follow-up of patients presenting to the ED with the complaint of epileptic seizures.

Materials and methods

This prospective, observational, single-center study was carried out in an adult population presenting to the ED. The study included patients older than 18 years of age presenting to the ED with the complaint of epileptic seizures.

Results

Of the 205 patients included in the study, 68 (33.2%) had seizure recurrence during the 6 h. In the univariable analysis, advanced age, prolonged post-ictal duration, increased seizure duration, generalized tonic clonic seizure, alcohol consumption within past 24 h, hypertension, coronary artery disease, Alzheimer's disease, prior ischemic cerebrovascular disease, low Glascow Coma Scale (GCS), high glucose, high C-Reactive Protein, high phosphorus, low potassium, high blood urea nitrogen, high lactate, increased anion gap, high osmolarity were statistically significant in predicting recurrent seizure recurrence within 6 h. According to the logistic regression, postictal duration, GCS score, and age were independent predictors in our model. The cut-off value of postictal duration in predicting seizure recurrence at the highest sensitivity (66.2%) and specificity (89.8%) was 22.5 min.

Conclusion

A prolonged postictal state, low GCS score, advanced age may be an indication of seizure recurrence. Therefore, patients with a long postictal duration, low GCS score, advanced age should be followed up more carefully in terms of recurrent seizures in the ED.

Indications for the use of intravenous second-line antiseizure medications in an emergency room setting

BACKGROUND

Second-line iv antiseizure medications (ASMs) are used to treat status epilepticus (SE), but in the emergency room setting, there might be other intended and unintended indications for administration. We wanted to explore these different indications and assess the actual usage of first- and second-line ASMs for SE with reference to other uses, such as for SE mimics.

METHODS

In this retrospective study, we searched the electronic patient registry with the following terms: "epilepsy", "SE", and "seizure", during 2015. Patients at least 16 years old and treated with iv second-line ASMs were further analysed. We reassessed the indications for the use of iv ASMs based on clinical features and examinations performed.

RESULTS

A total of 166 episodes from 136 patients with a median age of 66 years were evaluated, constituting the following indication categories: ongoing SE (48.2%), recurrent seizures (19.3%), postictal (12.1%), seizure mimics (10.2%) and prophylactic use of ASMs (10.2%). Ongoing SE included the following subgroups: convulsive SE, focal aware SE, nonconvulsive SE (NCSE) and NCSE with coma. The seizure mimics group had a preexisting epilepsy diagnosis more often than the ongoing SE group (73% vs. 44%, p = 0.039). Ischaemic stroke was the most frequent seizure mimic. EEG was performed during hospital admission in 78% of patients with ongoing SE, 50% of patients with recurrent seizures, 75% of patients with postictal state, 53% of seizure mimic episodes and 12% of the prophylactic group. In NCSE and comatose NCSE, the diagnosis was made, and treatment was initiated only after an EEG in 52% and 30% of cases, respectively. The use of newer second-line ASMs (levetiracetam and lacosamide) was frequent in our study population. Immediate side effects of ASMs were infrequent.

CONCLUSIONS

Even though most of the use of ASMs was justified and administered for SE, it is a diagnostic challenge where a prior diagnosis of epilepsy can be a misleading factor, and EEG is an essential tool when clinical features are often overlapping with other acute seizure disorders. Side effects of the newer second-line ASMs after a single dose are infrequent.

Acute and Prophylactic Management of Postictal Agitation in Electroconvulsive Therapy

ABSTRACT

Postictal agitation (PIA) is a common adverse effect of electroconvulsive therapy (ECT), a treatment used for a variety of psychiatric disorders. Because of risk of harm to patients and health providers when patients develop PIA, its acute management and prophylaxis are of vital importance for ECT practitioners. This article describes PIA risk factors, as well as practical steps to manage this ECT complication. Nonpharmacologic patient safety interventions are critical components of PIA management. Benzodiazepines, antipsychotics, and additional anesthetic doses are discussed as acute treatment interventions. Prophylactic pharmacologic choices described include antipsychotics, postseizure anesthetics, and dexmedetomidine. Exploratory choices such as melatonin and intranasal formulations of sedatives are also discussed. This review suggests that common medication like olanzapine and propofol are cost-effective considerations to decrease PIA incidence and/or severity after ECT. In addition, dexmedetomidine presents a management alternative for treatment-resistant PIA. This literature review outlines treatment choices while suggesting future directions for considering effective treatments of postictal agitation in clinical settings.

Benzodiazepine Use for Pediatric Patients With Suspected Nonconvulsive Status Epilepticus With or Without Simplified Electroencephalogram: A Retrospective Cohort Study

OBJECTIVES

In the present study, we aimed to determine the changes in the administration rate of benzodiazepines for pediatric patients with suspected nonconvulsive status epilepticus (NCSE) before and after the introduction of simplified electroencephalography (sEEG) in the emergency department.

METHODS

This retrospective cohort study included patients who were younger than 18 years and were admitted to the emergency department from August 1, 2009, to July 31, 2017, with altered level of consciousness and nonpurposeful movement of eyes or extremities after the cessation of convulsive status epilepticus. Patients with apparent persistent convulsions, those who were fully conscious on arrival, and those who were transferred from another hospital were excluded. The patients were categorized into pre and post groups based on the introduction of sEEG, and benzodiazepine administration was compared between the 2 groups.

RESULTS

During the study period, 464 patients with status epilepticus visited our emergency department and 69 and 93 patients fulfilling the study criteria were categorized into the pre and post groups, respectively. There were no significant differences in patient background characteristics between the 2 groups. Simplified electroencephalography was recorded in 52 patients in the post group. Benzodiazepines were administered in 44 of 69 patients (63.8%) in the pre group and 44 of 93 (47.3%) in the post group, and the benzodiazepine administration rate was significantly decreased after the introduction of sEEG ( P = 0.04). The hospitalization rate was significantly lower in the post group, but there were no significant differences in the rates of intensive care unit admission, reconvulsion after discharge, and final diagnoses between the 2 groups.

CONCLUSIONS

Simplified electroencephalography might aid in determining the need for anticonvulsant treatment for suspected NCSE in pediatric patients. Albeit not a definitive diagnostic tool, sEEG might be a reliable choice in the evaluation of pediatric patients with suspected NCSE.

Management of Status Epilepticus, Refractory Status Epilepticus, and Super-refractory Status Epilepticus

PURPOSE OF REVIEW

Status epilepticus is a serious condition caused by disorders and diseases that affect the central nervous system. In status epilepticus, hypersynchronous epileptic activity lasts longer than the usual duration of isolated self-limited seizures (time t1), which causes neuronal damage or alteration of neuronal networks at a certain time point (time t2), depending on the type of and duration of status epilepticus. The successful management of status epilepticus includes both the early termination of seizure activity and the earliest possible identification of a causative etiology, which may require independent acute treatment. In nonconvulsive status epilepticus, patients present only with subtle clinical signs or even without any visible clinical manifestations. In these cases, EEG allows for the assessment of cerebral function and identification of patterns in need of urgent treatment.

RECENT FINDINGS

In 2015, the International League Against Epilepsy proposed a new definition and classification of status epilepticus, encompassing four axes: symptomatology, etiology, EEG, and age. Various validation studies determined the practical usefulness of EEG criteria to identify nonconvulsive status epilepticus. The American Clinical Neurophysiology Society has incorporated these criteria into their most recent critical care EEG terminology in 2021. Etiology, age, symptomatology, and the metabolic demand associated with an increasing duration of status epilepticus are the most important determinants of prognosis. The consequences of status epilepticus can be visualized in vivo by MRI studies.

SUMMARY

The current knowledge about status epilepticus allows for a more reliable diagnosis, earlier treatment, and improved cerebral imaging of its consequences. Outcome prediction is a soft tool for estimating the need for intensive care resources.

Nonconvulsive Status Epilepticus in Metabolic Encephalopathy in Indonesia Referral Hospital

Background

Nonconvulsive status epilepticus (NCSE) is often underdiagnosed in patients with metabolic encephalopathy (ME). The diagnosis of ME should be made specifically to recognize the underlying etiology. Delay in seizure identification and making a diagnosis of NCSE contributed to the poor outcome.

Objective

This study aimed to find the incidence and outcome of NCSE in patients with ME.

Methods and Material

This was an observational prospective cross-sectional study in patients with ME in emergency and critical care units in Cipto Mangunkusumo General Hospital. The diagnosis of NCSE was based on EEG using Salzburg Criteria for Nonconvulsive Status Epilepticus (SCNC). The outcome was assessed within 30 days after the NCSE diagnosis has been made.

Results

A total of 50 patients with ME were involved in this study. NCSE was confirmed in 32 subjects (64%). The most common etiology of ME was sepsis (58%). The mortality rate in the NCSE and non-NCSE group was 40.6% vs 44.4%. Multiple aetiologies were risk factors to poor outcome in the NCSE group.

Conclusions

The incidence of NCSE among patients with ME at our hospital was high. Despite the anti-epileptic treatment of the NCSE group, the underlying cause of ME is still the main factor that affected the outcome. Therefore, aggressive treatment of anti-epileptic drug (AED) should be very carefully considered knowing the possible side-effect that might worsen the outcome of patients with ME.

Frequency and Implications of Complications in the ICU After Status Epilepticus: No Calm After the Storm

OBJECTIVES

To investigate the frequency, types, and implications of complications during intensive care in patients after status epilepticus has been successfully terminated.

DESIGN

Retrospective study.

SETTING

ICUs at a Swiss tertiary academic medical care center.

PATIENTS

Data were collected from the digital patient records of all adult patients with status epilepticus from 2012 to 2018.

INTERVENTIONS

None.

METHODS

Primary outcomes were defined as frequency of complications following status epilepticus termination and return to premorbid functional baseline. Univariable analyses regarding the relative risks of complications occurring after status epilepticus termination for no return to premorbid neurologic function were estimated by Poisson regression with robust error variance.

RESULTS

Of 311 patients with status epilepticus, 224 patients (72%) were treated on the ICU for more than 24 hours following status epilepticus termination. Ninety-six percent of patients remained in a prolonged state of altered consciousness for a median of 2 days (interquartile range, 1-3 d) and 80% had complications during their ICU treatment. Fifty-five percent had new-onset delirium with a median duration of 2 days (interquartile range, 1-3 d). Forty-two percent had mechanical ventilation for a median of 4 days (interquartile range, 2-11 d) and 21% had nosocomial infections diagnosed after status epilepticus. Multivariable analyses revealed that mechanical ventilation for more than 24 hours after status epilepticus, and arterial hypotension requiring vasopressors were independently associated with increased risk of no return to premorbid function (RRfor each additional day = 1.01; 95% CI, 1.02-1.03 and RRfor each additional day = 1.03; 95% CI, 1.01-1.05) and death (RRfor each additional day = 1.11; 95% CI, 1.04-1.19 and RRfor each additional day = 1.15; 95% CI, 1.03-1.28). Delirium was independently associated with a decreased relative risk of death (RRfor each additional day = 0.55; 95% CI, 0.37-0.80), but prolonged ICU- and hospital stays.

CONCLUSIONS

Complications after status epilepticus termination are frequent and associated with no return to premorbid function, death, and prolonged ICU- and hospital stays. These results call for heightened awareness and further studies mainly regarding prediction and preventive strategies in this context.

Prediction of Cognitive Decline in Temporal Lobe Epilepsy and Mild Cognitive Impairment by EEG, MRI, and Neuropsychology

Cognitive decline is a severe concern of patients with mild cognitive impairment. Also, in patients with temporal lobe epilepsy, memory problems are a frequently encountered problem with potential progression. On the background of a unifying hypothesis for cognitive decline, we merged knowledge from dementia and epilepsy research in order to identify biomarkers with a high predictive value for cognitive decline across and beyond these groups that can be fed into intelligent systems. We prospectively assessed patients with temporal lobe epilepsy (N = 9), mild cognitive impairment (N = 19), and subjective cognitive complaints (N = 4) and healthy controls (N = 18). All had structural cerebral MRI, EEG at rest and during declarative verbal memory performance, and a neuropsychological assessment which was repeated after 18 months. Cognitive decline was defined as significant change on neuropsychological subscales. We extracted volumetric and shape features from MRI and brain network measures from EEG and fed these features alongside a baseline testing in neuropsychology into a machine learning framework with feature subset selection and 5-fold cross validation. Out of 50 patients, 27 had a decline over time in executive functions, 23 in visual-verbal memory, 23 in divided attention, and 7 patients had an increase in depression scores. The best sensitivity/specificity for decline was 72%/82% for executive functions based on a feature combination from MRI volumetry and EEG partial coherence during recall of memories; 95%/74% for visual-verbal memory by combination of MRI-wavelet features and neuropsychology; 84%/76% for divided attention by combination of MRI-wavelet features and neuropsychology; and 81%/90% for increase of depression by combination of EEG partial directed coherence factor at rest and neuropsychology. Combining information from EEG, MRI, and neuropsychology in order to predict neuropsychological changes in a heterogeneous population could create a more general model of cognitive performance decline.

The postictal state - What do we know?

This narrative review provides a broad and comprehensive overview of the most important discoveries on the postictal state over the past decades as well as recent developments. After a description and definition of the postictal state, we discuss postictal sypmtoms, their clinical manifestations, and related findings. Moreover, pathophysiological advances are reviewed, followed by current treatment options.

Electroencephalography and delirium in the postoperative period

Delirium commonly manifests in the postoperative period as a clinical syndrome resulting from acute brain dysfunction or encephalopathy. Delirium is characterized by acute and often fluctuating changes in attention and cognition. Emergence delirium typically presents and resolves within minutes to hours after termination of general anaesthesia. Postoperative delirium hours to days after an invasive procedure can herald poor outcomes. Easily recognized when patients are hyperactive or agitated, delirium often evades diagnosis as it most frequently presents with hypoactivity and somnolence. EEG offers objective measurements to complement clinical assessment of this complex fluctuating disorder. Although EEG features of delirium in the postoperative period remain incompletely characterized, a shift of EEG power into low frequencies is a typical finding shared among encephalopathies that manifest with delirium. In aggregate, existing data suggest that serial or continuous EEG in the postoperative period facilitates monitoring of delirium development and severity and assists in detecting epileptic aetiologies. Future studies are needed to clarify the precise EEG features that can reliably predict or diagnose delirium in the postoperative period, and to provide mechanistic insights into this pathologically diverse neurological disorder.

Persistent catatonia following epileptic seizures: a case report and systematic literature search

BACKGROUND

Catatonia is frequently associated with mood and psychotic disorders as well as with general medical conditions, especially with seizures. In the case of the latter, catatonia mostly resolves when the seizures respond to the anticonvulsive treatment. We report, to our knowledge, the first case of a patient without affective or psychotic disorder, who developed catatonia in the postictum and whose catatonia did not resolve with anticonvulsive treatment, but did so with lorazepam.

CASE PRESENTATION

We describe a 36-year-old man, with no psychiatric history, except for a possible disorder in the use of cannabis, who developed catatonia after epileptic seizures. The catatonia did not respond to the anticonvulsant therapy, but did so to lorazepam 17 mg/d. Lorazepam could be tapered slowly and stopped without reemergence of catatonic signs.

CONCLUSION

Catatonia should be part of the differential diagnosis in patients with bradyphrenia and/or remarkable postictal behavior. This report shows that lorazepam should be taken into consideration (before moving to ECT), in cases of unresolved catatonia, even if the seizures are reduced with anticonvulsants.

Neuroimaging of status epilepticus

In the past 2 decades we have observed an extensive use of different neuroimaging techniques to evaluate patients with status epilepticus. Magnetic resonance imaging (MRI) in particular may show a broad spectrum of abnormalities that are either the causes or the consequences of sustained epileptic activity. Neuroimaging techniques can offer a contribution both in the clinical management of individual patients, identifying hemodynamic patterns that support the diagnosis, and also in the recognition of periictal reversible or irreversible alterations. For the future it is necessary to develop larger and prospective studies in which imaging techniques and electroencephalography (EEG) recordings are acquired closely to understand which EEG patterns are related to imaging biomarkers of neuronal damage.

Non-convulsive status epilepticus: mimics and chameleons

Non-convulsive status epilepticus (NCSE) is an enigmatic condition with protean manifestations. It often goes unrecognised, leading to delays in its diagnosis and treatment. The principal reason for such delay is the failure to consider and request an electroencephalogram (EEG), although occasional presentations have no scalp or surface electroencephalographic correlate. In certain settings with limited EEG availability, particularly out-of-hours, clinicians should consider treating without an EEG. Patients need a careful risk–benefit analysis to assess the risks of neuronal damage and harm versus the risks of adverse effects from various intensities of therapeutic intervention. Specialists in EEG, intensive care or epilepsy are invaluable in the management of patients with possible NCSE.

Hidden in plain sight: Non-convulsive status epilepticus-Recognition and management

Non-convulsive status epilepticus (NCSE) is an electroclinical state associated with an altered level of consciousness but lacking convulsive motor activity. It can present in a multitude of ways, but classification based on the clinical presentation and electroencephalographic appearances assists in determining prognosis and planning treatment. The aggressiveness of treatment should be based on the likely prognosis and the underlying cause of the NCSE.

Epileptic Activity Increases Cerebral Amino Acid Transport Assessed by 18F-Fluoroethyl-l-Tyrosine Amino Acid PET: A Potential Brain Tumor Mimic

O-(2-¹⁸F-fluoroethyl)-l-tyrosine (¹⁸F-FET) PET is a well-established method increasingly used for diagnosis, treatment planning, and monitoring in gliomas. Epileptic activity, frequently occurring in glioma patients, can influence MRI findings. Whether seizures also affect ¹⁸F-FET PET imaging is currently unknown. The aim of this retrospective analysis was to investigate the brain amino acid metabolism during epileptic seizures by ¹⁸F-FET PET and to elucidate the pathophysiologic background.

METHODS

Ten patients with 11 episodes of serial seizures or status epilepticus, who underwent MRI and ¹⁸F-FET PET, were studied. The main diagnosis was glioma World Health Organization grade II-IV (n = 8); 2 patients suffered from nonneoplastic diseases. Immunohistochemical assessment of LAT1/LAT2/CD98 amino acid transporters was performed in seizure-affected cortex (n = 2) and compared with glioma tissues (n = 3).

RESULTS

All patients exhibited increased seizure-associated strict gyral ¹⁸F-FET uptake, which was reversible in follow-up studies or negative shortly before and without any histologic or clinical signs of tumor recurrence. ¹⁸F-FET uptake corresponded to structural MRI changes, compatible with cortical vasogenic and cytotoxic edema, partial contrast enhancement, and hyperperfusion. Patients with prolonged postictal symptoms lasting up to 8 wk displayed intensive and widespread (≥ 1 lobe) cortical ¹⁸F-FET uptake. LAT1/LAT2/CD98 was strongly expressed in neurons and endothelium of seizure-affected brains and less in reactive astrocytosis.

CONCLUSION

Seizure activity, in particular status epilepticus, increases cerebral amino acid transport with a strict gyral ¹⁸F-FET uptake pattern. Such periictal pseudoprogression represents a potential pitfall of ¹⁸F-FET PET and may mimic brain tumor. Our data also indicate a seizure-induced upregulation of neuronal, endothelial, and less astroglial LAT1/LAT2/CD98 amino acid transporter expression.

Emergency electroencephalogram: Usefulness in the diagnosis of nonconvulsive status epilepticus by the on-call neurologist

INTRODUCTION

We aim to describe the use of emergency electroencephalogram (EmEEG) by the on-call neurologist when nonconvulsive status epilepticus (NCSE) is suspected, and in other indications, in a tertiary hospital.

SUBJECTS AND METHODS

Observational retrospective cohort study of emergency EEG (EmEEG) recordings with 8-channel systems performed and analysed by the on-call neurologist in the emergency department and in-hospital wards between July 2013 and May 2015. Variables recorded were sex, age, symptoms, first diagnosis, previous seizure and cause, previous stroke, cancer, brain computed tomography, diagnosis after EEG, treatment, patient progress, routine control EEG (rEEG), and final diagnosis. We analysed frequency data, sensitivity, and specificity in the diagnosis of NCSE.

RESULTS

The study included 135 EEG recordings performed in 129 patients; 51.4% were men and their median age was 69 years. In 112 cases (83%), doctors ruled out suspected NCSE because of altered level of consciousness in 42 (37.5%), behavioural abnormalities in 38 (33.9%), and aphasia in 32 (28.5%). The EmEEG diagnosis was NCSE in 37 patients (33%), and this was confirmed in 35 (94.6%) as the final diagnosis. In 3 other cases, NCSE was the diagnosis on discharge as confirmed by rEEG although the EmEEG missed this condition at first. EmEEG performed to rule out NCSE showed 92.1% sensitivity, 97.2% specificity, a positive predictive value of 94.6%, and a negative predictive value of 96%.

CONCLUSIONS

Our experience finds that, in an appropriate clinical context, EmEEG performed by the on-call neurologist is a sensitive and specific tool for diagnosing NCSE.

Which EEG patterns in coma are nonconvulsive status epilepticus?

Nonconvulsive status epilepticus (NCSE) is common in patients with coma with a prevalence between 5% and 48%. Patients in deep coma may exhibit epileptiform EEG patterns, such as generalized periodic spikes, and there is an ongoing debate about the relationship of these patterns and NCSE. The purposes of this review are (i) to discuss the various EEG patterns found in coma, its fluctuations, and transitions and (ii) to propose modified criteria for NCSE in coma. Classical coma patterns such as diffuse polymorphic delta activity, spindle coma, alpha/theta coma, low output voltage, or burst suppression do not reflect NCSE. Any ictal patterns with a typical spatiotemporal evolution or epileptiform discharges faster than 2.5 Hz in a comatose patient reflect nonconvulsive seizures or NCSE and should be treated. Generalized periodic diacharges or lateralized periodic discharges (GPDs/LPDs) with a frequency of less than 2.5 Hz or rhythmic discharges (RDs) faster than 0.5 Hz are the borderland of NCSE in coma. In these cases, at least one of the additional criteria is needed to diagnose NCSE (a) subtle clinical ictal phenomena, (b) typical spatiotemporal evolution, or (c) response to antiepileptic drug treatment. There is currently no consensus about how long these patterns must be present to qualify for NCSE, and the distinction from nonconvulsive seizures in patients with critical illness or in comatose patients seems arbitrary. The Salzburg Consensus Criteria for NCSE [1] have been modified according to the Standardized Terminology of the American Clinical Neurophysiology Society [2] and validated in three different cohorts, with a sensitivity of 97.2%, a specificity of 95.9%, and a diagnostic accuracy of 96.3% in patients with clinical signs of NCSE. Their diagnostic utility in different cohorts with patients in deep coma has to be studied in the future. This article is part of a Special Issue entitled "Status Epilepticus".

Is There a Relation between EEG-Slow Waves and Memory Dysfunction in Epilepsy? A Critical Appraisal

Is there a relationship between peri-ictal slow waves, loss of consciousness, memory, and slow-wave sleep, in patients with different forms of epilepsy? We hypothesize that mechanisms, which result in peri-ictal slow-wave activity as detected by the electroencephalogram, could negatively affect memory processes. Slow waves (≤4 Hz) can be found in seizures with impairment of consciousness and also occur in focal seizures without impairment of consciousness but with inhibited access to memory functions. Peri-ictal slow waves are regarded as dysfunctional and are probably caused by mechanisms, which are essential to disturb the consolidation of memory entries in these patients. This is in strong contrast to physiological slow-wave activity during deep sleep, which is thought to group memory-consolidating fast oscillatory activity. In patients with epilepsy, slow waves may not only correlate with the peri-ictal clouding of consciousness, but could be the epiphenomenon of mechanisms, which interfere with normal brain function in a wider range. These mechanisms may have transient impacts on memory, such as temporary inhibition of memory systems, altered patterns of hippocampal-neocortical interactions during slow-wave sleep, or disturbed cross-frequency coupling of slow and fast oscillations. In addition, repeated tonic-clonic seizures over the years in uncontrolled chronic epilepsy may cause a progressive cognitive decline. This hypothesis can only be assessed in long-term prospective studies. These studies could disentangle the reversible short-term impacts of seizures, and the impacts of chronic uncontrolled seizures. Chronic uncontrolled seizures lead to irreversible memory impairment. By contrast, short-term impacts do not necessarily lead to a progressive cognitive decline but result in significantly impaired peri-ictal memory performance.

Epilepsy-induced behavioral changes during the ictal phase

In epilepsy, experiential phenomena and behavioral manifestations may pose a number of problems in terms of differential diagnosis. From a clinical point of view, ictal psychiatric symptoms represent partial seizures, mainly partial ones. In the majority of cases, they are very brief (lasting from a few seconds to a few minutes), stereotyped, out of context, and frequently associated with subtle or overt automatisms and postictal confusion of variable duration. In some cases, such symptoms are followed by alteration of consciousness as the ictus evolves to a complex partial seizure or a generalized tonic-clonic seizure. This paper reviews clinically relevant behavioral patterns during seizures discussing clinical phenomenology and relevance in terms of lateralizing value.

Ictal cerebral positron emission tomography (PET) in focal status epilepticus

The diagnosis of focal status epilepticus (SE) can be challenging, particularly when clinical manifestations leave doubts about its nature, and electroencephalography (EEG) is not conclusive. This work addresses the utility of ictal (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) in focal SE, which was performed in eight patients in whom SE was finally diagnosed. Clinical, MRI and EEG data were reviewed. (18)F-FDG-PET proved useful: (1) to establish the diagnosis of focal SE, when clinical elements were equivocal or the EEG did not show clear-cut epileptiform abnormalities; (2) to delineate the epileptogenic area in view of possible resective surgery; and (3) when clinical features, MRI and EEG were incongruent regarding the origin of SE. We suggest that ictal (18)F-FDG-PET may represent a valuable diagnostic tool in selected patients with focal SE or frequent focal seizures.

Electroencephalographic criteria for nonconvulsive status epilepticus: synopsis and comprehensive survey

There have been many attempts at defining the electroencephalography (EEG) characteristics of nonconvulsive status epilepticus (NCSE) without a universally accepted definition. This lack of consensus arises because the EEG expression of NCSE does not exist in isolation, but reflects status epilepticus under the variety of pathologic conditions that occur with age, cerebral development, encephalopathy, and epilepsy syndrome. Current NCSE definitions include "boundary conditions," in which electroencephalographic seizure activity occurs without apparent clinical seizures. Furthermore, what appears to one interpreter as status epilepticus, is not to another reader, reflecting the "art" of EEG interpretation. Seizures and epilepsy syndromes have undergone an evolution that has moved beyond a classification of focal or generalized conditions into a syndromic approach. It seems appropriate to make similar changes in the EEG analysis of the syndromes of NCSE. In effect, the literature on epilepsy classification has progressed to incorporate the different NCSE types with clinical descriptions, but the specific EEG evidence for these types is found largely in individual reports, and often by description only. NCSE classification of EEG patterns should derive from the aggregate of published EEG patterns in the respective clinical subtype, supported by an analysis of these EEG studies. The analysis that follows presents clinical descriptions and EEG patterns of NCSE in the neonatal period, infancy, childhood, adulthood, and late adulthood from a syndromic perspective based on age, encephalopathy, cerebral development, etiology, and syndrome. Proceeding from the proposed classification of status epilepticus syndromes in "Status epilepticus: its clinical features and treatment in children and adults" (published in 1994 by Cambridge University Press, New York), we have performed a systematic search for reports presenting EEG patterns of NCSE using the online medical search engine PubMed for 22 different search strategies. EEG patterns were reviewed by two board-certified epileptologists who reached consensus regarding presence of NCSE. From a total of 4,328 search results, 123 cases with corresponding EEG patterns could be allocated to underlying epilepsy syndromes. Typical characteristic, prominent electrographic patterns, and sequential arrangements are elucidated for the different NCSE syndromes. This compendium of patterns by NCSE syndrome classification with illustration of EEGs, and delineation of electroencephalographic features helps define the characteristics and semiologic borderlines among the types of NCSE.

[Status epilepticus]

Status epilepticus (SE) is a medical emergency. For diagnostic purposes EEG is mandatory when motor phenomena are absent or when a single seizure evolves into SE with impaired consciousness. The EEG may show focal or generalized status patterns, which must be distinguished from encephalopathies. Initially benzodiazepines are recommended; lorazepam is the drug of choice. When the SE persists, phenytoin, valproate, levetiracetam, lacosamide, and phenobarbital are administered. The choice depends on the underlying comorbidities. In this phase, only phenytoin is licensed. A generalized tonic-clonic status which is refractory is then treated with anesthetics including midazolam, disoprivan, or thiopental. The goal is to achieve burst suppression in the EEG and coadministration of antiepileptic drugs.