Epidemiology, diagnosis, and management of nonconvulsive status epilepticus: Opening Pandora's box

The Role of Artificial Intelligence in the Diagnosis and Management of Non-convulsive Seizures: A Narrative Review

Non-convulsive seizures (NCS) are often underdiagnosed due to their subtle presentation including changes in behavior and mental status. Although electroencephalography (EEG) remains the gold standard for detection, challenges, such as subjective interpretation, individual observer variability, and limited availability, often prolong diagnosis. This can lead to severe complications, including cognitive decline and higher mortality rates. Recent developments in artificial intelligence (AI) are revolutionizing epilepsy care by providing enhanced accuracy and efficiency for diagnosing and managing NCS. Machine learning models, including convolutional neural networks (CNN), recurrent neural networks (RNN), and support vector machines (SVM) have demonstrated high precision in analyzing EEG data and predicting seizures. Innovations such as Ceribell Clarity algorithm (Ceribell, Sunnyvale, CA) allow fast, real-time seizure detection, reducing diagnostic delays in emergency and critical care. Wearable AI-driven technologies like wearable monitoring devices, predictive analytics, and explainable AI enhance personalized care and support better clinician decision-making. This review underlines AI's potential in neurology and neurosurgery, highlighting its role in enhancing diagnostic precision, accelerating interventions, and supporting surgical and treatment planning. By incorporating AI into clinical practice, healthcare systems can overcome diagnostic challenges and deliver patient-centered care. AI is becoming a key element in the future of medicine, driving advances in precision neurology and improving patient outcomes worldwide.

Using artificial intelligence to optimize anti-seizure treatment and EEG-guided decisions in severe brain injury

Electroencephalography (EEG) is invaluable in the management of acute neurological emergencies. Characteristic EEG changes have been identified in diverse neurologic conditions including stroke, trauma, and anoxia, and the increased utilization of continuous EEG (cEEG) has identified potentially harmful activity even in patients without overt clinical signs or neurologic diagnoses. Manual annotation by expert neurophysiologists is a major resource limitation in investigating the prognostic and therapeutic implications of these EEG patterns and in expanding EEG use to a broader set of patients who are likely to benefit. Artificial intelligence (AI) has already demonstrated clinical success in guiding cEEG allocation for patients at risk for seizures, and its potential uses in neurocritical care are expanding alongside improvements in AI itself. We review both current clinical uses of AI for EEG-guided management as well as ongoing research directions in automated seizure and ischemia detection, neurologic prognostication, and guidance of medical and surgical treatment.

Diagnostic Approach to the Patient with Altered Mental Status

Acute encephalopathy is a common presenting symptom in the emergency room and complicates many hospital and intensive care unit admissions. The evaluation of patients with encephalopathy poses several challenges: limited history and examination due to the patient's mental status, broad differential diagnosis of systemic and neurologic etiologies, low yield of neurodiagnostic testing due to the high base rate of systemic causes, and the importance of identifying less common neurologic causes of encephalopathy that can be life-threatening if not identified and treated. This article discusses the differential diagnosis of acute encephalopathy, presents an approach to the history and examination in a patient with encephalopathy, reviews the literature on the yield of neurodiagnostic testing in this population, and provides a diagnostic framework for the evaluation of patients with altered mental status.

Clinical manifestations and outcomes associated with a high 2HELPS2B score in patients with acute impaired consciousness

PURPOSE

The 2HELPS2B score is an invaluable tool for assessing seizure risk in critically ill patients with unconsciousness. However, this can be challenging for non-epileptologists to use owing to its reliance on electroencephalogram (EEG) analysis. Thus, identifying clinical manifestations associated with high 2HELPS2B scores is crucial.

METHODS

We examined patients who underwent EEG for acute impaired consciousness in the emergency department between 2020 and 2022. We evaluated the clinical manifestations immediately prior to the EEG tests and identified those associated with a 2HELPS2B score ≥ 2. Additionally, we investigated clinical outcomes in accordance with these manifestations and the 2HELPS2B score.

RESULTS

A total of 78 patients were included in this study. While the median 2HELPS2B score was 1 (range: 0-6), 13 patients (16.6%) showed electrographic/electroclinical seizures or status epilepticus and 16 patients (20.5%) showed ictal-interictal continuum in their EEGs. Abnormal muscle tonus (p = 0.034) and eye deviation (p = 0.021) were Significantly associated with a 2HELPS2B score ≥ 2. The presence of these manifestations (p < 0.001) and a 2HELPS2B score ≥ 2 (p < 0.001) were both significantly associated with a favorable response to anti-seizure medication. Conversely, patients with a 2HELPS2B score ≥ 2 who exhibited these clinical manifestations were more likely to be non-dischargeable (p = 0.053), have prolonged intensive care unit stays (p = 0.002), or require extended ventilator use (p = 0.082).

CONCLUSION

Abnormal muscle tonus and eye deviation were significant manifestations compatible with a 2HELPS2B score ≥ 2 and may indicate an increased risk of seizures or the severity of the epileptic condition.

Mammalian models of status epilepticus - Their value and limitations

Status epilepticus (SE) is a medical and neurologic emergency that may lead to permanent brain damage, morbidity, or death. Animal models of SE are particularly important to study the pathophysiology of SE and mechanisms of SE resistance to antiseizure medications with the aim to develop new, more effective treatments. In addition to rodents (rats or mice), larger mammalian species such as dogs, pigs, and nonhuman primates are used. This short review describes and discusses the value and limitations of the most frequently used mammalian models of SE. Issues that are discussed include (1) differences between chemical and electrical SE models; (2) the role of genetic background and environment on SE in rodents; (3) the use of rodent models (a) to study the pathophysiology of SE and mechanisms of SE resistance; (b) to study developmental aspects of SE; (c) to study the efficacy of new treatments, including drug combinations, for refractory SE; (d) to study the long-term consequences of SE and identify biomarkers; (e) to develop treatments that prevent or modify epilepsy; (e) to study the pharmacology of spontaneous seizures; (4) the limitations of animal models of induced SE; and (5) the advantages (and limitations) of naturally (spontaneously) occurring SE in epileptic dogs and nonhuman primates. Overall, mammalian models of SE have significantly increased our understanding of the pathophysiology and drug resistance of SE and identified potential targets for new, more effective treatments. This paper was presented at the 9th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in April 2024.

Differentiating loss of consciousness causes through artificial intelligence-enabled decoding of functional connectivity

Differential diagnosis of acute loss of consciousness (LOC) is crucial due to the need for different therapeutic strategies despite similar clinical presentations among etiologies such as nonconvulsive status epilepticus, metabolic encephalopathy, and benzodiazepine intoxication. While altered functional connectivity (FC) plays a pivotal role in the pathophysiology of LOC, there has been a lack of efforts to develop differential diagnosis artificial intelligence (AI) models that feature the distinctive FC change patterns specific to each LOC cause. Three approaches were applied for extracting features for the AI models: three-dimensional FC adjacency matrices, vectorized FC values, and graph theoretical measurements. Deep learning using convolutional neural networks (CNN) and various machine learning algorithms were implemented to compare classification accuracy using electroencephalography (EEG) data with different epoch sizes. The CNN model using FC adjacency matrices achieved the highest accuracy with an AUC of 0.905, with 20-s epoch data being optimal for classifying the different LOC causes. The high accuracy of the CNN model was maintained in a prospective cohort. Key distinguishing features among the LOC causes were found in the delta and theta brain wave bands. This research advances the understanding of LOC's underlying mechanisms and shows promise for enhancing diagnosis and treatment selection. Moreover, the AI models can provide accurate LOC differentiation with a relatively small amount of EEG data in 20-s epochs, which may be clinically useful.

Ketamine to Prevent Endotracheal Intubation in Adults with Refractory Non-convulsive Status Epilepticus: A Case Series

BACKGROUND

Non-convulsive status epilepticus (NCSE) is defined as status epilepticus (SE) with no obvious motor phenomenon and is diagnosed based on electroencephalogram (EEG). Refractory SE (RSE) is the persistence of seizures despite treatment with an adequately dosed first-line and second-line agents. Although guidelines for convulsive RSE include third-line agents such as intravenous anesthetic drugs (midazolam, propofol, or barbiturates), the therapeutic approach to NCSE is not well outlined. Treatment with traditional anesthetics invariably includes endotracheal intubation, which is associated with significant adverse events. Comparatively, ketamine, a non-competitive N-methyl-D-aspartate receptor antagonist is not associated with significant cardiorespiratory depression and may help in avoiding intubation.

OBJECTIVE

In this case series, we describe our experience with the early use of intravenous ketamine as the first anesthetic agent in patients with refractory NCSE to avoid endotracheal intubation.

METHODS

We present a case series of nine patients managed in the Neurointensive Care Unit at a university-affiliated tertiary care hospital. The study was approved by the hospital and university institutional review boards and the requirement for informed consent was waived for retrospective analysis of existing data, per institutional policy. All cases of SE were identified from a prospective database, and a subsequent retrospective chart review identified all patients with a diagnosis of refractory NCSE in whom ketamine was used as the first anesthetic agent. The primary endpoint was the avoidance of endotracheal intubation while on ketamine infusion. The secondary endpoint was defined as cessation of both clinical and electrographic seizures recorded on continuous EEG within 24 h of ketamine administration.

RESULTS

A total of nine patients experiencing refractory NCSE were included in this case series, with a median age of 61 (range 26-72) years and seven patients were male. The primary endpoint, avoiding intubation, was achieved in five out of nine (55%) cases. Six patients experienced resolution of refractory NCSE with ketamine administration as the sole anesthetic agent. Four patients required endotracheal intubation and three patients had a failure of seizure cessation with ketamine. Hypersalivation and pneumonia were the most common ketamine associated adverse events. In non-intubated patients, no deaths occurred. One patient was discharged home, four to subacute rehabilitation, one to a long term acute care hospital, and one patient to hospice.

CONCLUSION

The use of ketamine as the primary anesthetic agent may be a reasonable option to avoid endotracheal intubation in a subset of patients with refractory NCSE. This study is limited by its small sample size, retrospective design, and reliance on information obtained from chart review.

The Role of Routine Electroencephalography in the Diagnosis of Seizures in Medical Intensive Care Units

Seizures should be diagnosed and treated to ensure optimal health outcomes in critically ill patients admitted in the medical intensive care unit (MICU). Continuous electroencephalography is still infrequently used in the MICU. We investigated the effectiveness of routine EEG (rEEG) in detecting seizures in the MICU. A total of 560 patients admitted to the MICU between October 2018 and March 2023 and who underwent rEEG were reviewed. Seizure-related rEEG constituted 47% of all rEEG studies. Totally, 39% of the patients experienced clinical seizures during hospitalization; among them, 48% experienced the seizure, and 13% experienced their first seizure after undergoing an rEEG study. Seventy-seven percent of the patients had unfavorable short-term outcomes. Patients with cardiovascular diseases were the most likely to have the suppression/burst suppression (SBS) EEG pattern and the highest mortality rate. The rhythmic and periodic patterns (RPPs) and electrographic seizure (ESz) EEG pattern were associated with seizures within 24 h after rEEG, which was also related to unfavorable outcomes. Significant predictors of death were age > 59 years, the male gender, the presence of cardiovascular disease, a Glasgow Coma Scale score ≤ 5, and the SBS EEG pattern, with a predictive performance of 0.737 for death. rEEG can help identify patients at higher risk of seizures. We recommend repeated rEEG in patients with ESz or RPP EEG patterns to enable a more effective monitoring of seizure activities.

Alpha-2a adrenergic receptor activation in genetic absence epilepsy: An absence status model?

OBJECTIVE

The objective of the study was to propose a candidate animal model of absence status epilepticus induced by specific alpha-2a adrenergic receptor (α2AR) activation. We also aim to investigate the responsiveness of this model to classical anti-status or anti-absence medications.

METHODS

An α2AR agonist, dexmedetomidine (DEX), was injected intracerebroventricularly into adult rats with genetic absence epilepsy, and their electroencephalography (EEG) was recorded. The total duration, number, and mean duration of each spike-and-wave discharges (SWDs) were evaluated. The blocks of absence status events were classified as the initial and second sets of absence statuses. Ethosuximide (ETX) was administered as a pretreatment to another group of rats and later injected with 2.5 μg DEX. In addition, ETX, valproic acid (VPA), diazepam (DIAZ), and atipamezole (ATI) were administered after induced status-like events following DEX administration. Power spectral characteristics and coherence analysis were performed on the EEG to assess the absence status events and sleep.

RESULTS

The 2.5 μg dose of DEX increased the total SWD duration and induced continuous SWDs up to 26 min. Following the initial absence status event, sleep was induced; then, the second period of absence status-like activities were initiated. ETX pretreatment blocked the occurrence of absence status-like activities. Power spectral density analyses revealed that DEX-induced post-sleep activities had higher power in delta frequency band (1-4 Hz) and attenuated power of 7 Hz harmonics (14 and 21 Hz) than the pre-injection seizure. The mean duration of SWDs were decreased in all the groups, but occasional prolonged activities were seen in ETX or VPA-injected rats but not with DIAZ or ATI.

SIGNIFICANCE

This study presents an absence status epilepticus animal model that is activated by α2AR activation to investigate the pathophysiological role of absence status. Unlike other agents ATI switched off the second set of absence statuses to normal SWDs, without sedation or lethargy, can show it may preferentially block absence status-like activity.

THE PLAIN LANGUAGE SUMMARY

This study proposes a rat model for prolonged seizures, resembling absence status epilepticus. Activating the brain's alpha-2a adrenergic receptor with dexmedetomidine induced seizures lasting up to 26 minutes. Ethosuximide pretreatment and post-treatment with valproic acid, diazepam, and atipamezole decreased induced seizures. The findings suggest this model is valuable for studying absence status epilepticus. In addition, atipamezole normalized abnormal seizures without sedation, hinting at its potential for targeted treatment and further research.

Remote seizures and drug-resistant epilepsy after a first status epilepticus in adults

BACKGROUND AND PURPOSE

Long-term consequences after status epilepticus (SE) represent an unsettled issue. We investigated the incidence of remote unprovoked seizures (RS) and drug-resistant epilepsy (DRE) in a cohort of first-ever SE survivors.

METHODS

A retrospective, observational, and monocentric study was conducted on adult patients (age ≥ 14 years) with first SE who were consecutively admitted to the Modena Academic Hospital, Italy (September 2013-March 2022). Kaplan-Meier survival analyses were used to calculate the probability of seizure freedom following the index event, whereas Cox proportional hazard regression models were used to identify outcome predictors.

RESULTS

A total of 279 patients were included, 57 of whom (20.4%) developed RS (mean follow-up = 32.4 months). Cumulative probability of seizure freedom was 85%, 78%, and 68% respectively at 12 months, 2 years, and 5 years. In 45 of 57 patients (81%), the first relapse occurred within 2 years after SE. The risk of RS was higher in the case of structural brain damage (hazard ratio [HR] = 2.1, 95% confidence interval [CI] = 1.06-4.01), progressive symptomatic etiology (HR = 2.7, 95% CI = 1.44-5.16), and occurrence of nonconvulsive evolution in the semiological sequence of SE (HR = 2.9, 95% CI = 1.37-6.37). Eighteen of 57 patients (32%) developed DRE; the risk was higher in the case of super-refractory (p = 0.006) and non-convulsive SE evolution (p = 0.008).

CONCLUSIONS

The overall risk of RS was moderate, temporally confined within 2 years after the index event, and driven by specific etiologies and SE semiology. Treatment super-refractoriness and non-convulsive SE evolution were associated with DRE development.

Nonconvulsive Status Epilepticus: Clinical Findings, EEG Features, and Prognosis in a Developing Country, Mexico

PURPOSE

There is a lack of clinical and epidemiological knowledge about nonconvulsive status epilepticus (NCSE) in developing countries including Mexico, which has the highest prevalence of epilepsy in the Americas. Our aim was to describe the clinical findings, EEG features, and outcomes of NCSE in a tertiary center in Mexico.

METHODS

We conducted a retrospective case series study (2010-2020) including patients (≥15 years old) with NCSE according to the modified Salzburg NCSE criteria 2015 with at least 6 months of follow-up. We extracted the clinical data (age, sex, history of epilepsy, antiseizure medications, clinical manifestations, triggers, and etiology), EEG patterns of NCSE, and outcome. Descriptive statistics and multinomial logistic regression were used.

RESULTS

One hundred thirty-four patients were analyzed; 74 (54.8%) women, the total mean age was 39.5 (15-85) years, and 71% had a history of epilepsy. Altered state of consciousness was found in 82% (including 27.7% in coma). A generalized NCSE pattern was the most common (32.1%). The NCSE etiology was mainly idiopathic (56%), and previous uncontrolled epilepsy was the trigger in 48% of patients. The clinical outcome was remission with clinical improvement in 54.5%. Multinomial logistic regression showed that the patient's age (P = 0.04), absence of comorbidities (P = 0.04), history of perinatal hypoxia (P = 0.04), absence of clinical manifestations (P = 0.01), and coma (P = 0.03) were negatively correlated with the outcome and only the absence of generalized slowing in the EEG (P = 0.001) had a significant positive effect on the prognosis.

CONCLUSIONS

Age, history of perinatal hypoxia, coma, and focal ictal EEG pattern influence negatively the prognosis of NCSE.

Prevalence of non-convulsive seizures and electroencephalographic abnormalities in critically ill patients-A retrospective observational study

OBJECTIVE

Electroencephalographic (EEG) abnormalities especially non-convulsive status epilepticus (NCSE) have been found to be associated with worse outcomes in critically ill patients. We aimed to assess the prevalence of non-convulsive seizures and electroencephalographic abnormalities in critically ill patients. Furthermore, we aimed to investigate any association between the type of EEG abnormality and outcomes including ICU mortality and successful ICU discharge.

METHODS

This was a cross-sectional observational study carried out among critically ill patients in a mixed medical-surgical ICU from January 1, 2018 to May 15, 2020. A total of 178 records of 30 min bedside EEG records were found. EEG findings were grouped as normal, non-convulsive seizures (NCS), non-convulsive status epilepticus (NCSE), and other abnormalities. Descriptive analytical tools were used to characterize the case details in terms of the type of EEG abnormalities. Chi square test was used to describe the EEG abnormalities in terms of mortality. The status epilepticus severity scores (STESS) were further calculated for records with NCSE. These data were then analyzed for any association between STESS and mortality for cases with NCSE.

RESULTS

The prevalence of EEG abnormality in our cohort of all critically ill patients was found to be 7.3% (170/2234). Among the patients with altered sensorium in whom EEG was done, 42.9% had non-conclusive seizure activity with 25.2% in NCSE. Though the study was not adequately powered, there was a definite trend towards a lower proportion of successful ICU discharge rates seen among patients with higher STESS (>2) with only 33.3% being discharged for patients with a STESS of 6 versus 92.9% for those with STESS 3.

SIGNIFICANCE

When combined with a strong clinical suspicion, even a 30-min bedside EEG can result in detection of EEG abnormalities including NCS and NCSE. Hence, EEG should be regularly included in the evaluation of critically ill patients with altered sensorium.

PLAIN LANGUAGE SUMMARY

Electroencephalographic (EEG) abnormalities and seizures can have high prevalence in critically ill patients. These abnormalities notably, non-convulsive status epilepticus (NCSE) has been found to be associated with poor patient outcomes. This was a retrospective observational study analyzing 178 EEG records, from a mixed medical-surgical ICU. The indication for obtaining an EEG was based solely on the clinical suspicion of the treating physician. The study found a high prevalence of EEG abnormalities in 96.5% in whom it was obtained with 42.9% having any seizure activity and 28.8% having NCSE. The study was not powered for detection of association of the EEG abnormalities with clinical outcomes. However, a definite trend towards decreased chances of successful discharge from the ICU was seen. This study used strong clinical suspicion in patients with altered sensorium to obtain an EEG. High detection rates of EEG abnormalities were recorded in this study. Hence, combination of clinical judgement and EEG can improve detection of EEG abnormalities and NCSE.

Prevalence of nonconvulsive seizures and nonconvulsive status epilepticus in dogs and cats with a history of cluster seizures: A retrospective study

BACKGROUND

Nonconvulsive seizures (NCS) and nonconvulsive status epilepticus (NCSE) are frequently observed in human patients. Diagnosis of NCS and NCSE only can be achieved by the use of electroencephalography (EEG). Electroencephalographic monitoring is rare in veterinary medicine and consequently there is limited data on frequency of NCS and NCSE.

OBJECTIVES

Determine the prevalence of NCS and NCSE in dogs and cats with a history of cluster seizures.

ANIMALS

Twenty-six dogs and 12 cats.

METHODS

Retrospective study. Medical records of dogs and cats with cluster seizures were reviewed. Electroencephalography was performed in order to identify electrographic seizure activity after the apparent cessation of convulsive seizure activity.

RESULTS

Nonconvulsive seizures were detected in 9 dogs and 2 cats out of the 38 patients (29%). Nonconvulsive status epilepticus was detected in 4 dogs and 2 cats (16%). Five patients had both NCS and NCSE. A decreased level of consciousness was evident in 6/11 patients with NCS, 3/6 also had NCSE. Mortality rate for patients with NCS (73%) and NCSE (67%) was much higher than that for patients with no seizure activity on EEG (27%).

CONCLUSION AND CLINICAL IMPORTANCE

Prevalence of NCS and NCSE is high in dogs and cats with a history of cluster seizures. Nonconvulsive seizures and NCSE are difficult to detect clinically and are associated with higher in hospital mortality rates. Results indicate that prompt EEG monitoring should be performed in dogs and cats with cluster seizures.

Neurologic Complications of Cancer Immunotherapy

OBJECTIVE

Immunotherapeutic approaches have revolutionized cancer treatment with immune checkpoint inhibitors and adoptive T-cell therapy now approved to treat a variety of solid and hematologic malignancies. This article summarizes the distinctive neurologic side effects of these therapies as well as their management.

LATEST DEVELOPMENTS

Neurologic immune-related adverse events are rare but potentially serious complications of immune checkpoint inhibitors. Both peripheral and central nervous system disorders have been described, often necessitating a pause or cessation of immunotherapy. Immune effector cell-associated neurotoxicity syndrome is a potentially serious complication of chimeric antigen receptor T-cell therapy. While symptoms may be mild and self-limited, delirium, encephalopathy, seizures, focal neurologic deficits, and fulminant cerebral edema can be seen. Close neurologic monitoring is imperative. The mainstay of treatment for neurologic complications includes high-dose corticosteroids, although other immunomodulatory strategies may be used in severe or refractory cases.

ESSENTIAL POINTS

The spectrum of neurologic complications of cancer immunotherapy is broad, encompassing both central and peripheral nervous system disorders, indolent as well as fulminant clinical presentations, and wide-ranging severity with variable response to treatment. Early identification and multidisciplinary management are crucial to balance neurologic recovery and antitumor control.

Nonconvulsive Status Epilepticus: A Review for Emergency Clinicians

BACKGROUND

Status epilepticus is associated with significant morbidity and mortality and is divided into convulsive status epilepticus and nonconvulsive status epilepticus (NCSE).

OBJECTIVE

This review provides a focused evaluation of NCSE for emergency clinicians.

DISCUSSION

NCSE is a form of status epilepticus presenting with prolonged seizure activity. This disease is underdiagnosed, as it presents with nonspecific signs and symptoms, most commonly change in mental status without overt convulsive motor activity. Causes include epilepsy, cerebral pathology or injury, any systemic insult such as infection, and drugs or toxins. Mortality is primarily related to the underlying condition. Patients most commonly present with altered mental status, but other signs and symptoms include abnormal ocular movements and automatisms such as lip smacking or subtle motor twitches in the face or extremities. The diagnosis is divided into electrographic and electroclinical, and although electroencephalogram (EEG) is recommended for definitive diagnosis, emergency clinicians should consider this disease in patients with prolonged postictal state after a seizure with no improvement in mental status, altered mental status with acute cerebral pathology (e.g., stroke, hypoxic brain injury), and unexplained altered mental status. Assessment includes laboratory evaluation and neuroimaging with EEG. Management includes treating life-threatening conditions, including compromise of the airway, hypoglycemia, hyponatremia, and hypo- or hyperthermia, followed by rapid cessation of the seizure activity with benzodiazepines and other antiseizure medications.

CONCLUSIONS

An understanding of the presentation and management of NCSE can assist emergency clinicians in the care of these patients.

Presumed first episode of nonconvulsive status epilepticus as the cause of postoperative disorder of consciousness following the completion of general anesthesia: A case report

Key Clinical Message

Disorder of consciousness can lead to irreversible sequelae without proper intervention. Consequently, early diagnosis and treatment are of paramount importance in patients with disorder of consciousness.

Abstract

Disorder of consciousness (DOC) has various etiologies. Here, we report a case in which DOC following general anesthesia was suspected as being due to the first episode of nonconvulsive status epilepticus (NCSE). An elderly man in his 80s underwent uneventful tumor resection surgery under general anesthesia for extramammary Paget's disease. After the procedure, he regained consciousness following anesthesia discontinuation and was extubated. Soon after extubation, however, although his respiratory status remained stable, his level of consciousness deteriorated to a Glasgow Coma Scale (GCS) score of E1V1M1. Head computed tomography and magnetic resonance imaging scans indicated no abnormal findings. Subsequently, involuntary movements were noted in his left upper limb. Suspecting an epilepsy episode, diazepam was administered, leading to an improvement in the level of consciousness (GCS: E4V5M6). Based on the improvement in consciousness after diazepam administration, we strongly suspected NCSE.

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.

Nonconvulsive status epilepticus in neurocritical care: A critical reappraisal of outcome prediction scores

OBJECTIVE

Nonconvulsive status epilepticus (NCSE) is a frequent condition in the neurocritical care unit (NCCU) patient population, with high morbidity and mortality. We aimed to assess the validity of available outcome prediction scores for prognostication in an NCCU patient population in relation to their admission reason (NCSE vs. non-NCSE related).

METHODS

All 196 consecutive patients diagnosed with NCSE during the NCCU stay between January 2010 and December 2020 were included. Demographics, Simplified Acute Physiology Score II (SAPS II), NCSE characteristics, and in-hospital and 3-month outcome were extracted from the electronic charts. Status Epilepticus Severity Score (STESS), Epidemiology-Based Mortality Score in Status Epilepticus (EMSE), and encephalitis, NCSE, diazepam resistance, imaging features, and tracheal intubation score (END-IT) were evaluated as previously described. Univariable and multivariable analysis and comparison of sensitivity/specificity/positive and negative predictive values/accuracy were performed.

RESULTS

A total of 30.1% died during the hospital stay, and 63.5% of survivors did not achieve favorable outcome at 3 months after onset of NCSE. Patients admitted primarily due to NCSE had longer NCSE duration and were more likely to be intubated at diagnosis. The receiver operating characteristic (ROC) for SAPS II, EMSE, and STESS when predicting mortality was between .683 and .762. The ROC for SAPS II, EMSE, STESS, and END-IT when predicting 3-month outcome was between .649 and .710. The accuracy in predicting mortality/outcome was low, when considering both proposed cutoffs and optimized cutoffs (estimated using the Youden Index) as well as when adjusting for admission reason.

SIGNIFICANCE

The scores EMSE, STESS, and END-IT perform poorly when predicting outcome of patients with NCSE in an NCCU environment. They should be interpreted cautiously and only in conjunction with other clinical data in this particular patient group.

Non-convulsive status epilepticus possibly induced by a rapid correction of severe hyperkalemia: a case report and literature review

BACKGROUND

Patients with chronic kidney disease frequently develop neurological complications including confusion and altered consciousness. Non-convulsive status epilepticus, which is characterized by a change in behavior and/or mental process accompanied by epileptiform discharges on electroencephalogram in the absence of convulsive seizures, is one of the overlooked causes of altered consciousness. The incidence and precise pathophysiological mechanism of non-convulsive status epilepticus in patients with kidney disease, and especially in patients with electrolyte disturbances, remains unknown. We recently treated an older patient with chronic kidney disease and severe hyperkalemia in whom non-convulsive status epilepticus developed following a correction of severe hyperkalemia.

CASE PRESENTATION

An 82-year-old male was admitted to our hospital at midnight because of weakness of all four limbs (Day 1). He underwent urgent hemodialysis for severe hyperkalemia (9.84 mEq/L) and his serum potassium concentration decreased to 4.97 mEq/L. He regained full consciousness and his limb weakness improved on the morning of Day 2, but he became confused in the evening. Electroencephalogram revealed repeated low-voltage ictal discharges in the right occipital region and a diagnosis of non-convulsive status epilepticus was made. Following medication with fosphenytoin and phenytoin, the patient became fully alert and orientated on Day 8.

CONCLUSION

We speculate that a rapid correction of hyperkalemia was the possible cause of non-convulsive status epilepticus development. To our knowledge, this is the first report of non-convulsive status epilepticus from a potassium abnormality. We described a case of this condition in detail and summarized 78 previous case reports of non-convulsive status epilepticus with kidney disease or electrolyte disturbances.

Why won't it stop? The dynamics of benzodiazepine resistance in status epilepticus

Status epilepticus is a life-threatening neurological emergency that affects both adults and children. Approximately 36% of episodes of status epilepticus do not respond to the current preferred first-line treatment, benzodiazepines. The proportion of episodes that are refractory to benzodiazepines is higher in low-income and middle-income countries (LMICs) than in high-income countries (HICs). Evidence suggests that longer episodes of status epilepticus alter brain physiology, thereby contributing to the emergence of benzodiazepine resistance. Such changes include alterations in GABA_A receptor function and in the transmembrane gradient for chloride, both of which erode the ability of benzodiazepines to enhance inhibitory synaptic signalling. Often, current management guidelines for status epilepticus do not account for these duration-related changes in pathophysiology, which might differentially impact individuals in LMICs, where the average time taken to reach medical attention is longer than in HICs. In this Perspective article, we aim to combine clinical insights and the latest evidence from basic science to inspire a new, context-specific approach to efficiently managing status epilepticus.

Hippocampal injury and learning deficits following non-convulsive status epilepticus in periadolescent rats

The effects of non-convulsive status epilepticus (NCSE) on the developing brain remain largely elusive. Here we investigated potential hippocampal injury and learning deficits following one or two episodes of NCSE in periadolescent rats. Non-convulsive status epilepticus was induced with subconvulsive doses of intrahippocampal kainic acid (KA) under continuous EEG monitoring in postnatal day 43 (P43) rats. The RKA group (repeated KA) received intrahippocampal KA at P43 and P44, the SKA group (single KA injection) received KA at P43 and an intrahippocampal saline injection at P44. Controls were sham-treated with saline. The modified two-way active avoidance (MAAV) test was conducted between P45 and P52 to assess learning of context-cued and tone-signaled electrical foot-shock avoidance. Histological analyses were performed at P52 to assess hippocampal neuronal densities, as well as potential reactive astrocytosis and synaptic dysfunction with GFAP (glial fibrillary acidic protein) and synaptophysin (Syp) staining, respectively. Kainic acid injections resulted in electroclinical seizures characterized by behavioral arrest, oromotor automatisms and salivation, without tonic-clonic activity. Compared to controls, both the SKA and RKA groups had lower rates of tone-signaled shock avoidance (p < 0.05). In contextual testing, SKA rats were comparable to controls (p > 0.05), but the RKA group had learning deficits (p < 0.05). Hippocampal neuronal densities were comparable in all groups. Compared to controls, both the SKA and RKA groups had higher hippocampal GFAP levels (p < 0.05). The RKA group also had lower hippocampal Syp levels compared to the SKA and control groups (p < 0.05), which were comparable (p > 0.05). We show that hippocampal NCSE in periadolescent rats results in a seizure burden-dependent hippocampal injury accompanied by cognitive deficits. Our data suggest that the diagnosis and treatment of NCSE should be prompt.

The serotonin toxidrome: shortfalls of current diagnostic criteria for related syndromes

INTRODUCTION

Serotonin syndrome (toxicity) describes adverse drug effects from toxic amounts of intra-synaptic central nervous system serotonin. A wide range of drugs have been implicated to cause serotonin toxicity, not all justifiably. The plausible agents all have a final common pathway resulting in a substantial increase in central nervous system serotonergic neurotransmission. Serotonin toxicity is characterized by neuromuscular excitation, mental status changes, and autonomic dysregulation. Signs and symptoms represent a spectrum of toxicity (mild to life-threatening) related to increasing serotonin concentrations. As there is no consensus on the threshold for "toxicity" or diagnostic criteria, the true incidence of serotonin toxicity is unknown. The incidence in overdose is easier to quantify and is reasonably common in serotonergic antidepressant overdoses. In a large case series of overdoses, moderate serotonin toxicity occurred in 14% of poisonings with a selective serotonin reuptake inhibitor. While half those ingesting a monoamine oxidase inhibitor in combination with a serotonergic agent in overdose exhibit at least moderately severe serotonin toxicity. In contrast, the incidence of serotonin toxicity in those on therapeutic serotonergic agents appears to be very low.

OBJECTIVES

To provide a narrative review of the current diagnostic criteria, utilizing case reports of fatalities to evaluate how many meet the various diagnostic criteria and propose practical solutions to resolve controversies in diagnosis.

METHODS

A review of serotonin toxicity diagnostic criteria in the English literature was completed by searching Embase and PubMed from January 1990 to July 2021 for the keywords "serotonin syndrome/toxicity" paired with "diagnostic criteria" or "diagnosis." Also, fatal cases of serotonin toxicity identified from a recent systematic review were independently examined to determine what diagnostic criteria were met and whether serotonin toxicity or another cause was most likely.

REVIEW OF DIAGNOSIS CRITERIA

Serotonin toxicity is a clinical diagnosis, four diagnostic criteria (Sternbach, Serotonin Syndrome Scale, Radomski, and Hunter) have been proposed. However, the Serotonin Syndrome Scale has not been validated in patients with serotonin toxicity and only utilized in those on a serotonergic agent. The remaining three criteria are utilized more widely but have undergone little refinement or validation.

REVIEW OF FATAL CASES

Shortfalls with diagnostic criteria can be illustrated by examining case fatalities. Of 55 fatal cases reviewed, 12 (22%) were unlikely to be serotonin toxicity. Sternbach and Radomski criteria were met by 25 (45%), 20 (36%) had insufficient data reported and 10 (18%) met an exclusion criterion. Few had sufficient information reported to determine whether Hunter Criteria were met, with only 13 (24%) documented as meeting the criteria, the remaining 42 (76%) had insufficient data.

RESOLVING SHORTFALLS IN CURRENT DIAGNOSTIC CRITERIA

As serotonin toxicity is a clinical diagnosis, issues arise when basing the diagnosis on symptom criteria alone, without considering whether the drug/s ingested increase central nervous system serotonin or whether there is an alternative diagnosis. This has resulted in case reports and government warnings for drugs that cannot plausibly cause significant serotonin toxicity (e.g., ondansetron and antipsychotics). We propose when assessing for a serotonin toxidrome, both the causative agent(s) and clinical scenario is considered to determine the likelihood of serotonin toxicity. Then the clinical features assessed, those with a moderate to high prior probability (e.g., serotonergic drug-drug interaction, overdose, recent initiation or increase in dose of serotonergic agent/s) could be diagnosed based on the Hunter criteria. However, those with a low probability (e.g., stable therapeutic doses of a serotonergic agent) require more specific and stringent criteria. Finally, we propose a minimum dataset for case reports/series of serotonin toxicity.

CONCLUSIONS

More complete and accurate reporting of serotonin toxicity cases is required in the future, to avoid further misleading associations that are physiologically implausible.

Salzburg Criteria, A Useful Tool in Non-Convulsive Status Epilepticus Diagnosis: A Retrospective Study

Introduction. Non-convulsive status epilepticus (NCSE) has been traditionally a challenging electroencephalographic (EEG) diagnosis. For this reason, Salzburg consensus criteria (SCC) have been proposed to facilitate correct diagnosis. Methods. We retrospectively reanalyzed 41 cases referred to our department (from 2016 to 2018) under the suspicion of NCSE. In this study, we compared the original description (standard criteria) versus the updated description (SCC) of the same EEG. Results. Originally, 15 patients were diagnosed as NCSE (37%) and 26 patients as no NCSE (63%), using the standard criteria. Then, we analyzed EEGs according to the SCC, which led to the following results: 9 patients fulfilled the criteria for definite NCSE (22%), 20 patients were diagnosed as possible NCSE (49%) and 12 patients were diagnosed as no NCSE (29%). Subsequently, when we analyze the outcome of possible NCSE cases, we note that 50% of these patients presented mild-poor outcome (neurological deficits, deceased). Indeed, we observed worse outcomes in patients previously diagnosed as no NCSE and untreated, specifically post-anoxic cases. Conclusions. Salzburg criteria seem to be a useful tool to support NCSE diagnosis, introducing the category of possible NCSE. In our study, we observed that it contributes to improving the prognosis and management of the patients. However, more prospective studies are needed to demonstrate the accuracy of SCC.

Case Report: Hypopituitarism Presenting With Nonconvulsive Status Epilepticus

Introduction: Hypopituitarism is defined as one or more partial or complete pituitary hormone deficiencies. Nonconvulsive status epilepticus (NCSE) refers to a state of continuous or repetitive seizures without convulsions. In this paper, we review a case of an old female patient with hypopituitarism who presented with NCSE, which is rare in the clinic.

Case Report: This paper describes a 67-year-old female patient with hypopituitarism who presented as NCSE. She had surgical resection of pituitary tumor half a year before the seizures and did not get regular hormone replacement therapy. She presented general convulsive status epilepsy as the initial symptom and got sedation and antiepileptic drug in the emergency room. The seizure was terminated but the patient fell in coma in the following days. The patient had magnetic resonance imaging (MRI) and other inspects, and EEG showed epileptic discharges. Combining these clinical symptoms and examinations, we made the diagnosis of NCSE. Finally, she regained consciousness after the treatment with diazepam.

Conclusion: This case report and literature review investigated the possible mechanism of hypopituitarism presenting with NCSE.

Epidemiology, management and outcome of status epilepticus in adults: single-center Italian survey

The official variations of status epilepticus (SE) International League Against Epilepsy (ILAE, 2015) diagnostic criteria and the non-convulsive SE (NCSE) Salzburg Consensus Criteria (2013), impose the collection of updated population-based epidemiological Italian data. In this study, we aimed at evaluating (a) the frequency of SE in our hospital adopting the new ILAE 2015 SE diagnostic criteria and NCSE Salzburg Consensus Criteria, (b) the frequency of adherence to current treatment guidelines for SE and their relationship with patients' outcome, and (c) reliability of standardized prognostic scales (Status Epilepticus Severity Score-STESS-and modified STESS) for short-term outcome prediction in the setting of the newest diagnostic criteria for SE and NCSE. Detailed clinical and electrophysiological data collected in a 1-year retrospective hospital-based single-center survey on SE at Parma Hospital, Northern Italy are provided. Non-adherence to current treatment guidelines was recorded in around 50% cases, but no relation to outcome was appreciated. Mortality in our cohort increased from 30 to 50% when follow-up was extended to 30 days. STESS score was strongly correlated with short-term mortality risk (OR 18.9, 2.2-163.5, CI), and we confirm its role as easy-to-use tool for outcome evaluation also when the new ILAE diagnostic SE criteria are applied.

Non-convulsive status epilepticus in the immediate postoperative period following spine surgery

Background

Non-convulsive status epilepticus (NCSE), in which continuous epileptiform discharges occur without seizure-like movement, is rare and unfamiliar to anesthesiologists, both of which make this condition overlooked in patients with decreased levels of consciousness following general anesthesia.

Case

We report on an elderly female patient who developed NCSE in the immediate postoperative period after the spine surgery. Initially, delayed emergence from anesthesia was suspected, but the electroencephalogram confirmed NCSE, and anticonvulsant therapy was initiated.

Conclusions

Delayed emergence is commonly attributed to cerebrovascular events or residual anesthetic effects, but NCSE must be included in the differential diagnosis, especially in elderly patients. Anticonvulsant therapy should be initiated as soon as possible for a better prognosis.

Clinical features and outcomes of nonconvulsive status epilepticus in a developing country: A 5-year retrospective study

BACKGROUND

This study aimed to determine the frequency of electrographically confirmed nonconvulsive status epilepticus (NCSE) in a cohort suspected with this condition and to determine the demographic/clinical profile, treatment, and outcomes of these patients in the context of a developing country, the Philippines.

METHODS

We conducted a retrospective study among patients with suspected with NCSE admitted in the Philippine General Hospital from 2014 to 2019. Using the Salzberg 2013 criteria to diagnose NCSE, three electroencephalographers independently reviewed the electroencephalogram (EEG) tracings of suspected patients and were blinded from the clinical information. Then, we obtained pertinent clinical data from the medical records of EEG-confirmed NCSE cases.

RESULTS

Out of 89 patients suspected with NCSE and with available EEG tracings, information from a total of 14 patients (15.7%) with electrographically confirmed cases were included in the analysis. Median age was 52 ranging from 22 to 77 and female-to-male ratio was 1.3:1. The following conditions were associated with NCSE: intracranial tumor (n = 4), metabolic encephalopathy (n = 4), autoimmune encephalitis (n = 3), intracranial hemorrhage (n = 3), sepsis (n = 3), cardiac arrest (n = 2), hypoxic-ischemic injury (n = 2), antiepileptic withdrawal (n = 1), intracranial abscess (n = 1), head trauma (n = 1), and meningitis (n = 1). Three patients (21.4%) had relatively good clinical outcomes (mRS 0-2) while 6 patients (42.8%) had poor outcomes (mRS 3-5) at discharge. Five patients (35.7%) died due to medical/neurological complications. Our review of the literature showed that the profile of NCSE cases identified in our resource-limited institution strengthens the findings in other populations.

CONCLUSION

Our data showed that approximately 1 in 6 patients who are suspected with NCSE may have electrographic evidence of NCSE in our setting. The most common etiologies associated with NCSE were intracranial tumors and metabolic conditions. Further studies may entail a prospective collection of data to validate the estimates of our study.

Status Epilepticus: Definition, Classification, Pathophysiology, and Epidemiology

Status epilepticus (SE) is the state of continuous or repetitive seizures, which can occur with or without convulsions. Evolving definitions of SE take into account the concept that neuronal injury may occur at different times in different types of SE.SE that does not respond to initial treatment may become refractory or even super-refractory. Nonconvulsive SE is increasingly recognized in comatose patients in critical care units, with the growing use of continuous electroencephalogram monitoring. SE is a neurologic emergency that carries a high risk of mortality and morbidity.

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.

An update on the recognition and treatment of non-convulsive status epilepticus in the intensive care unit

INTRODUCTION

Non-convulsive status epilepticus (NCSE) is a complex and diverse condition which is often an under-recognised entity in the intensive care unit. When NCSE is identified the optimal treatment strategy is not always clear. Areas covered: This review is based on a literature review of the key literature in the field over the last 5-10 years. The articles were selected based on their importance to the field by the authors. Expert commentary: This review discusses the complex situations when a neurological consultation may occur in a critical care setting and provides an update on the latest evidence regarding the recognition of NCSE and the decision making around determining the aggressiveness of treatment. It also considers the ictal-interictal continuum of conditions which may be met with, particularly in the era of continuous EEG, and provides an approach for dealing with these. Suggestions for how the field will develop are discussed.

Nonconvulsive status epilepticus in adults - insights into the invisible

Nonconvulsive status epilepticus (NCSE) is a state of continuous or repetitive seizures without convulsions. Owing to the nonspecific symptoms and considerable morbidity and mortality associated with NCSE, clinical research has focused on early diagnosis, risk stratification and seizure termination. The subtle symptoms and the necessity for electroencephalographic confirmation of seizures result in under-diagnosis with deleterious consequences. The introduction of continuous EEG to clinical practice, and the characterization of electrographic criteria have delineated a number of NCSE types that are associated with different prognoses in several clinical settings. Epidemiological studies have uncovered risk factors for NCSE; knowledge of these factors, together with particular clinical characteristics and EEG observations, enables tailored treatment. Despite these advances, NCSE can be refractory to antiepileptic drugs, necessitating further escalation of treatment. The presumptive escalation to anaesthetics, however, has recently been questioned owing to an association with increased mortality. This Review compiles epidemiological, clinical and diagnostic aspects of NCSE, and considers current treatment options and prognosis.

Myoclonus in the critically ill: Diagnosis, management, and clinical impact

Myoclonus is the second most common involuntary non-epileptic movement in intensive care units following tremor-like gestures. Although there are several types of myoclonus, they remain underappreciated, and their diagnostic and prognostic associations are largely ignored. This review discusses clinical, electrophysiological, neuroanatomical, and neuroimaging characteristics of different types of myoclonus in critically ill adults along with their prognostic impact and treatment options. Myoclonus is characterized by a sudden, brief, and sometimes repetitive muscle contraction of body parts, or a brief and sudden cessation of tonic muscle innervation followed by a rapid recovery of tonus. Myoclonus can resemble physiologic and other pathologic involuntary movements. Neurologic injuries, anesthetics, and muscle relaxants interfere with the typical appearance of myoclonus. Identifying "real myoclonus" and determining the neuroanatomical origin are important, as treatment responses depend on the involved neuroanatomical structures. The identification of the type of myoclonus, the involved neuroanatomical structures, and the associated illnesses is essential to direct treatment. In conclusion, the combined clinical, electrophysiological, and neuroradiological examination reliably uncovers the neuroanatomical sources and the pathophysiology of myoclonus. Recognizing cortical myoclonus is critical, as it is treatable and may progress to generalized convulsive seizures or status epilepticus.