Semiology of spontaneous generalized tonic-clonic seizures in the epileptic baboon

Objective

The epileptic baboon provides an animal model for juvenile myoclonic epilepsy (JME), demonstrating spontaneous generalized tonic‐clonic seizures (GTCS) in addition to generalized myoclonic, absence and multifocal seizures. While photoconvulsive responses have been described in this model, spontaneous GTCS have not been characterized.

Methods

In this study, we characterized 46 seizures in 7 epileptic baboons (5 females, 12 ± 3 years old) by video recording. While housed in single cages, the baboons were monitored for a median of 2 (range 1‐10) weeks, with high‐resolution, infrared‐capable camera systems. Each GTCS was evaluated for evidence of preconvulsive ictal symptoms, focal convulsive behaviors, duration of the preconvulsive and convulsive periods, postictal immobility, and recovery of an upright posture. The circadian pattern of GTCS was also for each baboon.

Results

More than half of GTCS occurred in sleep, beginning from an upright position in all but one tethered baboon. Focal semiological findings were noted in 19 (41%) GTCS, and these included preconvulsive focal ictal motor behaviors as well as lateralized motor activity during the convulsions. The convulsive portion lasted 47 ± 10 seconds, whereas the entire seizure lasted 54 ± 21 seconds. Postictally, the baboons remained immobile for a median latency of 40 (range 14‐347) seconds, recovering an upright posture after 173 (range 71‐1980) seconds. GTCS demonstrated circadian patterns in all but one baboon, with 34 (74%) all seizures occurring between 1‐9 am.

Significance

GTCS in the baboon revealed intersubject variability, but semiology remained stereotyped in a given baboon. Similar to GTCS in people with JME, focal symptoms were also observed in epileptic baboons. The postictal recovery period, characterized by postictal immobility and myoclonus as well as time to recumbency, also varied among baboons.

Assessment of cardiac structure and function in a murine model of temporal lobe epilepsy

Sudden unexpected death in epilepsy (SUDEP) is a significant cause of premature seizure-related death. An association between SUDEP and cardiac remodeling has been suggested. However, whether SUDEP is a direct consequence of acute or recurrent seizures is unsettled. The purpose of this study was to evaluate the impact of status epilepticus (SE) and chronic seizures on myocardial structure and function. We used the intracortical kainate injection model of temporal lobe epilepsy to elicit SE and chronic epilepsy in mice. In total, 24 C57/BL6 mice (13 kainate, 11 sham) were studied 2 and 30 days post-injection. Cardiac structure and function were investigated in-vivo with a 9.4 T MRI, electrocardiography (ECG), echocardiography, and histology [Haematoxylin/Eosin (HE) and Martius Scarlet Blue (MSB)] for staining of collagen proliferation and fibrin accumulation. In conclusion, we did not detect any significant changes in cardiac structure and function neither in mice 2 days nor 30 days post-injection.

Prone, lateral, or supine positioning at seizure onset determines the postictal body position: A multicenter video-EEG monitoring cohort study

PURPOSE

Most patients who die from sudden unexpected death in epilepsy (SUDEP) are found in the prone position. We evaluated whether changes in body position occur during generalized convulsive seizures (GCSs).

METHOD

GCSs in patients undergoing video-EEG-monitoring between 2007 and 2017 at epilepsy centers in Frankfurt and Marburg were analyzed in relation to changes in body position.

RESULTS

A total of 494 GCSs were analyzed among 327 patients. At seizure onset, positions included supine (48.2 %), right lateral (19.0 %), left lateral (15.6 %), sitting or standing (14.0 %), and prone (3.2 %). Between seizure onset and the start of generalization, 57.5 % of participants altered body positions. During four seizures, patients adopted a prone position, while, in five seizures, patients moved from a prone position. Patients who experienced GCS onset while in a nonprone position had a 2.1 % risk of entering the prone position by the end of their seizure. In contrast, 56.2 % of those in an initial prone position remained so at the end of the GCS, with an odds ratio for maintaining that position of 60.2 (95 % confidence interval: 29.1-124.3; p < 0.001). The likelihood of ending up in the prone position post-GCS did not vary among patients with different nonprone starting positions (p = 0.147).

CONCLUSIONS

Seizures in prone position occur during sleep and the highest risk for postictal prone positioning appears to be being in the prone position at GCS onset. Epilepsy patients should therefore be advised to go to sleep in a supine or lateral position to reduce their SUDEP risk.

Progressive cardiorespiratory dysfunction in Kv1.1 knockout mice may provide temporal biomarkers of pending sudden unexpected death in epilepsy (SUDEP): The contribution of orexin

OBJECTIVE

Immediately preceding sudden unexpected death in epilepsy (SUDEP), patients experienced a final generalized tonic-clonic seizure (GTCS), rapid ventilation, apnea, bradycardia, terminal apnea, and asystole. Whether a progressive pathophysiology develops and increases risk of SUDEP remains unknown. Here, we determined (a) heart rate, respiratory rate, and blood oxygen saturation (SaO₂ ) in low-risk and high-risk knockout (KO) mice; and (b) whether blocking receptors for orexin, a cardiorespiratory neuromodulator, influences cardiorespiratory function mice or longevity in high-risk KO mice.

METHODS

Heart rate and SaO₂ were determined noninvasively with ECGenie and pulse oximetry. Respiration was determined with noninvasive airway mechanics technology. The role of orexin was determined within subject following acute treatment with a dual orexin receptor antagonist (DORA, 100 mg/kg). The number of orexin neurons in the lateral hypothalamus was determined with immunohistochemistry.

RESULTS

Intermittent bradycardia was more prevalent in high-risk KO mice, an effect that may be the result of increased parasympathetic drive. High-risk KO mice had more orexin neurons in the lateral hypothalamus. Blocking of orexin receptors differentially influenced heart rate in KO, but not wild-type (WT) mice. When DORA administration increased heart rate, it also decreased heart rate variability, breathing frequency, and/or hypopnea-apnea. Blocking orexin receptors prevented the methacholine (MCh)-induced increase in breathing frequency in KO mice and reduced MCh-induced seizures, via a direct or indirect mechanism. DORA improved oxygen saturation in KO mice with intermittent hypoxia. Daily administration of DORA to high-risk KO mice increased longevity.

SIGNIFICANCE

High-risk KO mice have a unique cardiorespiratory phenotype that is characterized by progressive changes in five interdependent endpoints. Blocking of orexin receptors attenuates some of these endpoints and increases longevity, supporting the notion that windows of opportunity for intervention exist in this preclinical SUDEP model.

Review on post-mortem diagnosis in suspected SUDEP: Currently still a difficult task for Forensic Pathologists

Sudden and unexpected death in epilepsy (SUDEP) represents the predominant cause of premature deaths in young adults with epilepsy and is more common with patients with poorly controlled and generalized convulsive seizures. It is reported that there are 1,16 cases for every 1000 subjects affected with epilepsy. This review takes stock of the current problems and issues in the autopsy of cases of sudden death with epileptic people. For this purpose, all the possible findings of post-mortem examinations reported in the literature were analyzed and summarized, which can currently be considered useful for autopsy diagnoses as well as in the comprehension of the physiopathology of SUDEP. The enormous limitation of forensic pathology studies is the complete lack of a specific SUDEP diagnostic marker. Only in a few cases was it possible to find pathological signs of the brain that would clarify epilepsy-related deaths. Genetic research has tracked down variants of neurocardiac genes of ion channels in a restricted percentage of suspected SUDEP cases. The actual pathogenicity test requires an in-depth statistical analysis in order to prove there is a real excess of variants and evidence that the mutation alters the function. Despite scientific efforts, it is often difficult to distinguish SUDEP from other causes of sudden death. For these reasons, it will be necessary to create an international standard SUDEP death scene investigation and postmortem examination protocols. Further future studies of immunohistochemistry or genetics may help and may facilitate post-mortem diagnosis in cases of presumed SUDEP.

Electrocardiographic changes associated with epilepsy beyond heart rate and their utilization in future seizure detection and forecasting methods

The ability to assess seizure risk may help provide timely warnings and more personalized treatment plans for people with epilepsy (PWE). ECG changes are commonly observed in epilepsy which make ECG a promising candidate to monitor seizure risk. Most ECG research in this domain has focused on heart rate-related changes. However, several studies have identified a range of other peri-ictal ECG parameter changes that may potentially prove useful for seizure detection and forecasting. Here, we offer a systematic review of ECG changes in epilepsy outside of heart rate. We performed the systematic literature review according to PRISMA guidelines using key words related to ECG, SUDEP and epilepsy. We identified and screened 502 abstracts, read 110 full papers, and included 24 papers in the final review. Our results suggest that PWE may be more prone to cardiac conduction abnormalities than healthy controls. During interictal periods, PWE were more likely to have abnormal QTc intervals, ST segment abnormalities, elevated T Waves, early repolarization (ER), increased P Wave dispersion and PR intervals when compared to controls. Apart from these baseline abnormalities, changes during the pre-ictal and ictal states have been reported, with arrhythmias, QTc prolongation and ST segment changes being the most common. A better understanding of these state-dependent changes may afford less-cumbersome and less-stigmatizing epilepsy monitoring tools in the future.

Epilepsy deaths: Learning from health service delivery and trying to reduce risk

Two recent UK reports have highlighted data of concern in relation to potentially preventable epilepsy deaths. Public Health England, an executive agency of the Government Department of Health, using National Health Service data from 2001 to 2014 reported a rise in direct age-standardised mortality for epilepsy-associated deaths, in contrast to a reduction in all-cause deaths over the same period. Premature death was seen in people aged below 50 years, especially in men, and where epilepsy was a contributory cause rather than an association. The Scottish Epilepsy Deaths Study, analysing deaths between 2009 and 2016, similarly found death in those with epilepsy was significantly higher than the matched population below the age of 54, especially between the ages of 16 and 24 (6 times higher). Sudden unexpected death in epilepsy accounted for 38% of epilepsy-related deaths under the age of 45. Both studies found a strong relationship between risk of death and deprivation; we discuss the implications of these and other data for planning service delivery and improving epilepsy care. This paper is for the Special Issue: Prevent 21: SUDEP Summit - Time to Listen.

Learnings from deaths - the Epilepsy Deaths Register

The Epilepsy Deaths Register (EDR) differs from typical registries which concentrate primarily on clinical information. It is completed by bereaved relatives and focuses on the circumstances immediately before, and the support following, a death. It can be augmented by copies of death certificates from the families of the deceased, and all epilepsy associated deaths can be entered. The EDR is underpinned by the research and experience of the SUDEP Action team and the clinical advisors who helped design the methodology and the web-based platform. The EDR has been open since 2013 and currently has over 750 entries from over 20 different countries, the majority from the United Kingdom and the Republic of Ireland. The bereaved have shown that they place their trust in the register as a vehicle to be involved in research, even under the most difficult of circumstances. As the EDR matures, we hope to identify the common and rarer patterns of epilepsy-associated death; maintaining our dual ambitions to remain committed to listen, and to make every death count. This paper is for the Special Issue: Prevent 21: SUDEP Summit - Time to Listen.

Learnings from supporting traumatic grief in the aftermath of sudden epilepsy deaths

The majority of epilepsy deaths are sudden, unexpected, and most prevalent among young adults. The number of people affected by a death can be high, as extended family and social networks survive. Those bereaved are at risk of developing traumatic and complex grief reactions and need access to specialist bereavement support as soon as possible after a death. It helps bereaved families to know how the death happened. They want lessons to be learnt and deaths to be prevented in future. The process of investigation into the death - which can contribute to these aims - may alienate families if not handled well and cause further trauma. Loss of participation by those bereaved can lead to suboptimal investigation and missed opportunities for learning and prevention. With integrated specialist emotional and practical support, tailored to the individual, families can be empowered to participate as they choose, with those working to understand and prevent epilepsy deaths. SUDEP Action (formerly Epilepsy Bereaved) is a charity which provides specialist services for people bereaved by epilepsy. It is the only organization which delivers these services globally. It was set up by the bereaved for the bereaved and has developed its model through more than twenty years' experience of supporting bereaved people. If the bereaved are signposted to specialist support of the sort SUDEP Action provides as soon as possible after a death, that early intervention can help to alleviate the effects of traumatic bereavement and restore an element of control and choice as they navigate what is to come. Early intervention by signposting to skilled experienced epilepsy death-related bereavement services could be vital.

Bridging the gap of risk communication and management using the SUDEP and Seizure Safety Checklist

Sudden unexpected death in epilepsy (SUDEP) is a tragic condition and, despite varied risk levels among the population with epilepsy, is the cause of significant premature mortality. In the last 20 years, though awareness of SUDEP has increased among epilepsy professionals, little has changed with regard to the death rates per se, in rates of informing people with epilepsy (PWE) of their person-centered SUDEP risks, or in the awareness levels of nonepilepsy clinicians, such as, primary care practitioners and hospital doctors. The challenges to make aware and inform PWE have been multifold, in particular, 'when', 'what', and 'how' to tell about SUDEP. Current guidance recognizes that to improve SUDEP rates, it is important to engage proactively with PWE. There is a need to bring shared responsibility between clinicians and PWE to help mitigate the risk of SUDEP. To enable this, a meaningful evidence-based person-centered conversation is essential. The SUDEP and Seizure Safety Checklist ("Checklist") was created to facilitate this. This paper showcases the background, concept, development, implementation, feasibility and validity studies undertaken, challenges, barriers, and limitations of the eight-year Checklist project, which has moved from a single clinic to an international presence. It outlines the need to further reform SUDEP risk communication recognizing the differences between a basic risk message at time of diagnosis as advocated by current good practice guidance and the need for a more person-centered discussion on a regular basis for which the Checklist can be a key catalyst. This article is part of the Special Issue "Prevent 21: SUDEP Summit - Time to Listen".

SUDEP and mortality in epilepsy: The role of routinely collected healthcare data, registries, and health inequalities

Routinely collected data are a powerful research resource and offer the opportunity to further our understanding of epilepsy mortality and Sudden Unexpected Death in Epilepsy (SUDEP). The advantages of using routinely collected data include that it often covers whole populations, is already collected, and can be easily linked to other data sources. A significant disadvantage is the difficulty in obtaining accurate causes of death and correctly identifying cases of SUDEP. Using and linking data from epilepsy death registries can improve the quality of mortality data for research. Epilepsy prevalence, incidence, and mortality rates are associated with socioeconomic deprivation. Further research into understanding the link between deprivation and epilepsy mortality could lead to ways to reduce epilepsy mortality. This paper is for the Special Issue :Prevent 21: SUDEP Summit - Time to Listen.

The view of the clinician and the scientist on the family experience of sudden epilepsy deaths

A sudden epilepsy-associated death is a tragedy for the bereaved, a failure for the clinician and a challenge for a research scientist. Sudden death in epilepsy cannot be truly anticipated or prepared for by the bereaved, or the clinical team. Communications and provision of pastoral care following sudden unexpected death in epilepsy (SUDEP) is an important part of an epilepsy service where interaction with the family and specialist services for the bereaved can be rewarding. Sudden death and SUDEP are valid targets for research attention, but families may be less aware of opportunities to assist in life science research or conversely feel coerced at a vulnerable time. We have a responsibility to ensure that the SUDEP risk is minimized and that we maximize the learning potential from each death. Out of such tragedies some good must come, but this will take combined efforts from doctors, families, and the voluntary sector acting in league with scientific and academic funders. In this review, we set out to consider the dual viewpoints of the clinician and the scientist and how they consider the family experience of sudden deaths to provide advice for all parties. "This paper is for the Special Issue: Prevent 21: SUDEP Summit - Time to Listen".

The role of devices in managing risk

Over the last few years, there has been significant expansion of wearable technologies and devices into the health sector, including for conditions such as epilepsy. Although there is significant potential to benefit patients, there is a paucity of well-conducted scientific research in order to inform patients and healthcare providers of the most appropriate technology. In addition to either directly or indirectly identifying seizure activity, the ideal device should improve quality of life and reduce the risk of sudden unexpected death in epilepsy (SUDEP). Devices typically monitor a number of parameters including electroencephalographic (EEG), cardiac, and respiratory patterns and can detect movement, changes in skin conductance, and muscle activity. Multimodal devices are emerging with improved seizure detection rates and reduced false positive alarms. While convulsive seizures are reliably identified by most unimodal and multimodal devices, seizures associated with no, or minimal, movement are frequently undetected. The vast majority of current devices detect but do not actively intervene. At best, therefore, they indicate the presence of seizure activity in order to accurately ascertain true seizure frequency or facilitate intervention by others, which may, nevertheless, impact the rate of SUDEP. Future devices are likely to both detect and intervene within an autonomous closed-loop system tailored to the individual and by self-learning from the analysis of patient-specific parameters. The formulation of standards for regulatory bodies to validate seizure detection devices is also of paramount importance in order to confidently ascertain the performance of a device; and this will be facilitated by the creation of a large, open database containing multimodal annotated data in order to test device algorithms. This paper is for the Special Issue: Prevent 21: SUDEP Summit - Time to Listen.

Epilepsy deaths in children: Improvements driven by data and surveillance in pediatrics

Epilepsy-related death in children and young people deserves understanding and intervention along with epilepsy-related deaths in adults. Risk of death from epilepsy varies at different ages, and the specific calculations of risk remains complex and varies between studies. There have been several UK studies examining factors associated with epilepsy-related deaths. A UK national audit with other national initiatives has evidenced improving quality of care and more recently allowed service provision factors associated with reduced epilepsy-related death to be evidenced. A national program of health education, formalized epilepsy networks, commissioned surgical pathways, and patient information resources around risk and participation are examples of quality improvement initiatives. Epilepsy-related death is a key outcome, and there remains many difficulties and opportunities at local, regional, and national level to better understand and improve this outcome for children and young people and the adults that they should become. This paper is for the Special Issue: Prevent 21: SUDEP Summit - Time to Listen.

SUDEP: A global perspective

The potential for an epileptic seizure to end life has been known throughout history, although the cause of many such deaths is still not understood. Over the last 25 years there has been increasing interest in the phenomenon of Sudden Unexpected Death in Epilepsy (SUDEP) leading to an upswing in the investigation of epilepsy-related mortality. Families bereaved by epilepsy have played an important role in promoting awareness and research, with the UK leading the way on community and political action to tackle epilepsy-related mortality; SUDEP has now become a global conversation with clinicians, scientists, and the community working together to identify strategies that can reduce deaths. The evolution in the approach to epilepsy-related deaths and the impact on epilepsy care are discussed. This paper is for the Special Issue "Prevent 21: SUDEP Summit - Time to Listen".

Comparison of clinical and electrophysiological characteristics between ictal and cardiac asystole encountered during video-EEG monitoring

Differentiation between syncope secondary to epileptic seizures and cardiac disease in patients displaying transient loss of consciousness associated with convulsive movements is a diagnostic challenge both for neurologists and cardiologists. In such patients, prolonged video-EEG monitoring not only helps in identifying asystole as the cause of syncope, but also in categorizing asystole as primarily cardiac in origin (cardiac asystole) and secondary to epileptic seizures (ictal asystole). We carried out this study to ascertain the prevalence of asystole in an epilepsy monitoring unit, and to contrast the clinical and electrophysiological characteristics between ictal asystole and cardiac asystole. Through a retrospective search, we identified patients who were shown to have had asystole using a database of patients who underwent prolonged video-EEG monitoring during a 68-month period. We compared the data of 18 consecutive patients; five with ictal asystole and 13 with cardiac asystole, with 121 and 64 events recorded from them, respectively. Of the 10,096 patients who underwent prolonged video-EEG monitoring during the study period, we identified 18 (0.17%) patients with asystole. Cardiac asystole was 2.6 times more frequent than ictal asystole. Older age at onset, heralding symptoms of presyncope, occurrence during wakefulness, and brief duration of the events supported the diagnosis of cardiac asystole. Ictal asystole events were more protracted, and prolonged asystole more frequently occurred in patients with extratemporal seizures compared to temporal lobe seizures. Asystole occurred in only half of the recorded seizures. The accurate categorization of asystole as seizure-related or heart disease-related has huge implications for management strategy and outcome. The necessity of permanent pacemaker implantation is more frequent and urgent in patients with cardiac asystole because of the greater risk of sudden death. Hence, in patients with an ominous diagnosis of cardiac asystole, a thorough cardiac evaluation should surpass neurological evaluation.

Seizures induce obstructive apnea in DBA/2J audiogenic seizure-prone mice: Lifesaving impact of tracheal implants

The mechanism(s) for sudden death in epilepsy (SUDEP) remain(s) unknown, but seizure spread to brainstem areas serving autonomic and respiratory function is critical. In a rat model, we established a mechanism for SUDEP that involves seizure-induced laryngospasm and obstructive apnea lasting until respiratory arrest. We hypothesized that DBA/2J mice, which display lethal audiogenic seizures, would be protected from death by implanting a tracheal T-tube as a surrogate airway. In a 2 × 2 design, mice were implanted with either open or closed tracheal T-tubes and treated with either low-dose ketamine/xylazine to moderate thoracic spasm during the tonic seizure phase or no drug. Animals receiving both treatments had the highest survival rate, followed by animals receiving the open tube without ketamine/xylazine. The odds ratio for survival was >20 higher with an open T-tube (odds ratio = 24.14). The impact of open tracheal tubes indicates that the mechanism of death in DBA/2J mice involves seizure-induced upper airway obstruction until respiratory arrest. These results, our rat work, and our demonstration of inspiratory effort-based electromyographic signals and electrocardiographic abnormalities in rats and humans suggest that seizure-induced laryngospasm and obstructive apnea directly link seizure activity to respiratory arrest in these sudden death examples.

Consensus statement for the management of generalized tonic-clonic seizures in Spain

OBJECTIVE

To develop recommendations for the management of patients with primary or secondary generalized tonic-clonic seizures (GTCS) based on best evidence and experience.

METHODS

The Delphi methodology was followed. A multidisciplinary panel of 10 experts was established, who defined the scope, users and preliminary recommendations. Systematic and narrative reviews of the current literature were performed to assess data on the risk of sudden unexpected death in epilepsy and the efficacy and safety of add-on therapy in patients with GTCS. Twenty-five definitive recommendations were generated which were then graded on a scale of 1 (totally disagree) to 10 (totally agree) by the experts and 45 neurologists. Consensus was reached if at least 70% of the participants applied a score of ≥7. Each recommendation was then assigned a level of evidence, a grade of agreement and a grade of recommendation. The entire process was supervised by an expert methodologist.

RESULTS

Overall, 24 out of 25 recommendations achieved consensus. These included specific recommendations on diagnosis, evaluation and treatment. The recommendations also emphasized the importance of proper psychological evaluation and effective communication between patients and health professionals, and the importance of patient and family education and support.

SIGNIFICANCE

The recommendations generated by this consensus can be used as a guide for the diagnosis and management of patients with GTCS.

The earliest experimental convulsions by Joseph Priestley in 1766 friendship with Benjamin Franklin

In 1766, Joseph Priestley (1733-1804) was the first to systematically demonstrate the universal convulsive effect of an electrical discharge applied to the head of all the several species studied. We here republish his overlooked experiments, which often resulted in death, and which ante date the scientific studies of the electrical functions of the brain, the role of "discharges" in seizures, and experimental epilepsy by about a century. Priestley's studies of electricity were influenced by those of Benjamin Franklin (1706-1790), who became a good friend during Franklin's prolonged period in London between 1757 and 1775. Both were elected Fellows of the Royal Society and both were awarded the Copley Medal of that Society. Priestley's experiments are relevant to the history of epilepsy and neuropsychiatry, and to the modern study of sudden unexplained death in epilepsy (SUDEP).

Serotonin and sudden unexpected death in epilepsy

Epilepsy is a highly prevalent disease characterized by recurrent, spontaneous seizures. Approximately one-third of epilepsy patients will not achieve seizure freedom with medical management and become refractory to conventional treatments. These patients are at greatest risk for sudden unexpected death in epilepsy (SUDEP). The exact etiology of SUDEP is unknown, but a combination of respiratory, cardiac, neuronal electrographic dysfunction, and arousal impairment is thought to underlie SUDEP. Serotonin (5-HT) is involved in regulation of breathing, sleep/wake states, arousal, and seizure modulation and has been implicated in the pathophysiology of SUDEP. This review explores the current state of understanding of the relationship between 5-HT, epilepsy, and respiratory and autonomic control processes relevant to SUDEP in epilepsy patients and in animal models.

Ictal asystole with intercurrent cardiopathy: a complex combination leading to delayed diagnosis

Ictal asystole is a rare epileptic phenomenon, though usually self-limiting, which has been associated with an increased risk of sudden death in epileptic patients. Although early recognition is desirable, the diagnosis can be delayed until prolonged video-EEG monitoring is completed. We report a case of ictal asystole in a 74-year-old patient with co-morbid cardiac conditions leading to a delay in diagnosis of approximately 10 years. Indeed, multiple cardiac investigations and EEGs failed to reveal that the recurrent syncope was seizure induced. A detailed description of the case with an emphasis on the prolonged diagnostic process, as well as the clinical and EEG findings, is provided. This case highlights the complexity of the diagnosis of some ictal asystole cases and the need to perform continuous video-EEG monitoring for confirmation. [Published with video sequence].

Acute metabolic effects of tonic-clonic seizures

OBJECTIVE

Tonic-clonic seizures (TCS) lead to metabolic stress and changes in related blood markers. Such markers may indicate harmful conditions but can also help to identify TCS as a cause of transient loss of consciousness. In this study, we hypothesized that the alterations of circulating markers of metabolic stress depend on the clinical features of TCS.

METHODS

Ninety-one adults undergoing video-EEG monitoring participated in this prospective study. Electrolytes, renal parameters, creatine kinase (CK), prolactin (PRL), lactate, ammonia, glucose, and other parameters were measured at inclusion and different time points after TCS.

RESULTS

A total of 39 TCS were recorded in 32 patients (six generalized onset tonic-clonic seizures in 6 and 33 focal to bilateral tonic-clonic seizures in 26 patients). Shortly after TCS, mean lactate, ammonia, and PRL levels were significantly increased 8.7-fold, 2.6-fold, and 5.1-fold, respectively, with levels of more than twofold above the upper limits of the normal (ULN) in 90%, 71%, and 70% of the TCS and returned to baseline levels within 2 hours. Only postictal lactate levels were significantly correlated with the total duration of the tonic-clonic phase. In contrast, CK elevations above the ULN were found in three TCS (~10%) only with a peak after 48 hours. Immediately after the TCS, hyperphosphatemia occurred in one third of the patients, whereas hypophosphatemia was observed in one third 2 hours later. TCS led to subtle but significant alterations of other electrolytes, creatinine, and uric acid, whereas glucose levels were moderately increased.

SIGNIFICANCE

Lactate is a robust metabolic marker of TCS with elevations found in ~90% of cases within 30 minutes after seizure termination, whereas ammonia rises in ~ 70%, similarly to PRL. Phosphate levels show an early increase and a decrease 2 hours after TCS in a third of patients. CK elevations are rare after video-EEG-documented TCS, challenging its value as a diagnostic marker.

Blockade of astrocytic activation delays the occurrence of severe hypoxia-induced seizure and respiratory arrest in mice

Seizures are induced when subjects are exposed to severe hypoxia. It is followed by ventilatory fall-off and eventual respiratory arrest, which may underlie the pathophysiology of death in patients with epilepsy and severe respiratory disorders. However, the mechanisms of hypoxia-induced seizures have not been fully understood. Because astrocytes are involved in various neurological disorders, we aimed to investigate whether astrocytes are operational in seizure generation and respiratory arrest in a severe hypoxic condition. We examined the effects of astrocytic activation blockade on responses of EEG and ventilation to severe hypoxia. Adult mice were divided into two groups; in one group (n = 24) only vehicle was injected, and in the other group (n = 24) arundic acid, an inhibitory modulator of astrocytic activation, was administered before initiation of recording. After recording EEG and ventilation by whole body plethysmography in room air, the gas in the recording chamber was switched to 5% oxygen (nitrogen balanced) until a seizure and ventilatory depression occurred, followed by prompt switch back to room air. Severe hypoxia initially increased ventilation, followed by a seizure and ventilatory suppression in all mice examined. Fourteen mice without arundic acid showed respiratory arrest during loading of hypoxia. However, 22 mice pretreated with arundic acid did not suffer from respiratory arrest. Time from the onset of hypoxia to the occurrence of seizures was significantly longer in the group with arundic acid than that in the group without arundic acid. We suggest that blockade of astrocytic activation delays the occurrence of seizures and prevents respiratory arrest.

An oxygen-rich atmosphere or systemic fluoxetine extend the time to respiratory arrest in a rat model of obstructive apnea

Audiogenic seizure-prone mice can be protected from seizure-associated death by exposure to an oxygen atmosphere or treatment with selective serotonergic reuptake inhibitors (SSRIs). We have shown previously in a rat model that epileptic seizure activity can spread through brainstem areas to cause sufficient laryngospasm for obstructive apnea and that the period of seizure-associated obstructive apnea can last long enough for respiratory arrest to occur. We hypothesized that both the oxygen-rich atmosphere and SSRIs function by prolonging the time to respiratory arrest, thus ensuring that seizure activity stops before the point of respiratory arrest to allow recovery of respiratory function. To test this hypothesis, we evaluated each preventative treatment in a rat model of controlled airway occlusion where the times to respiratory arrest can be measured. Adult male Sprague Dawley rats (median age = 66 days) were studied in the absence of any seizure activity. By directly studying responses to controlled airway occlusion, rather than airway occlusion secondary to seizure activity, we could isolate the effects of manipulations that might prolong respiratory arrest from the effects of those manipulations on seizure intensity. All group sizes were ≥ 8 animals per group. We found that both oxygen exposure and fluoxetine significantly increased the time to respiratory arrest by up to 65% (p < .0001 for 5 min oxygen exposure; p = .031 for 25 mg/kg fluoxetine tested 60 min after injection) and, given that neither treatment has been shown to significantly alter seizure duration, these increases can account for the protection of either manipulation against death in sudden death models. Importantly, we found that 30 s of exposure to oxygen produced nearly the same protection as 5 min exposure suggesting that oxygen exposure could start after a seizure starts (p = .0012 for 30 s oxygen exposure). Experiments with 50% oxygen/50% air mixtures indicate that the oxygen concentration needs to be above about 60% to ensure that times to respiratory arrest will always be longer than a period of seizure-induced airway occlusion. Selective serotonin reuptake inhibitors, while instructive with regard to mechanism, require impractical dosing and may carry additional risk in the form of greater challenges for resuscitation. We conclude that oxygen exposure or SSRI treatment prevent seizure associated death by sufficiently prolonging the time to respiratory arrest so that respiratory function can recover after the seizure abates and eliminates the stimulus for seizure-induced apnea.

Scurrying to Understand Sudden Expected Death in Epilepsy: Insights From Animal Models

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in patients with refractory epilepsy, accounting for up to 17% of deaths in patients with epilepsy. The pathophysiology of SUDEP has remained unclear, largely because it is unpredictable and commonly unwitnessed. This poses a great challenge to studies in patients. Recently, there has been an increase in animal studies to try to better understand the pathophysiology of SUDEP. In this current review, we focus on developments through seizure-induced death models and the preventative strategies they may reveal.