Potential Role of Febrile Seizures and Other Risk Factors Associated With Sudden Deaths in Children

Complex Febrile Seizures: Usual and the Unusual

Febrile seizures account for 2 to 14% of all childhood seizures, and one-third of febrile seizures are complex febrile seizures. Despite this, there is a lack of clinical equipoise in the diagnosis and management of complex febrile seizures and this results in significant practice variability amongst physicians. Although febrile seizures are generally noted to be benign phenomenon, complex febrile seizures carry the risk of subsequent epilepsy. Furthermore, long-term neurodevelopmental sequelae have been observed in some cohorts. The presence of both simple and complex febrile seizures have also been documented in sudden unexpected death in childhood cohorts, and there may be similarities in the underlying pathophysiology to sudden unexpected death in epilepsy. Finally, in some cases the presence of complex febrile seizures may herald the onset of a devastating developmental and epileptic encephalopathy (i.e., Dravet syndrome) or Febrile-Infection Related Epilepsy Syndrome (FIRES). In this narrative review the authors explore the current state of management of complex febrile seizures, their neurological sequelae and morbidity as well as rare epilepsy syndromes and conditions associated with them.

Sudden unexpected infant death, sudden unexplained death in childhood, and sudden unexpected death in epilepsy

Sudden deaths in infants and children represent a profound and tragic event that continues to challenge researchers despite extensive investigation over several decades. The predominant phenotype, sudden infant death syndrome (SIDS), has evolved into the broader category of sudden unexpected infant death (SUID). In older children, a less understood phenomenon known as sudden unexplained death in childhood (SUDC) has garnered attention. Additionally, sudden unexpected death in epilepsy (SUDEP) constitutes a rare but recognized complication of epilepsy. Recent investigations indicate overlapping clinical, neuropathological, and genetic characteristics among SUID, SUDC, and SUDEP. Common features include death occurring during sleep, discovery in the prone position, hippocampal abnormalities, and genetic variations associated with epilepsy or cardiac arrhythmias. Notably, video recordings in certain examples of SUDC have captured 'convulsive' episodes preceding death in children without prior seizure history, suggesting that seizures may contribute more significantly to sudden paediatric deaths than previously presumed. This review explores these shared elements, underscoring their importance in formulating possible preventative measures against these devastating conditions.

A preliminary study on the association between prognostic nutritional index and neutrophil-to-lymphocyte ratio with nutritional status and inflammation in febrile children's susceptibility to seizures

OBJECTIVE

The aim of this study was to evaluate the association between nutritional status, inflammation, and susceptibility to seizures in febrile children.

METHODS

This observational single-center study was carried out from January 2020 to December 2023 with 324 children aged 6 months and 6 years; 106 were diagnosed with febrile seizure, 108 were febrile children, and 110 were healthy controls. The prognostic nutritional index and neutrophil-to-lymphocyte ratio were calculated, and the cutoff threshold was established through receiver operating characteristics. The study utilized correlation and univariate-multivariate logistic regression analysis. The comparison between simple and complex febrile seizure was conducted to analyze differences.

RESULTS

The optimal cutoff values were identified as 61.25 for prognostic nutritional index and 1.04 for neutrophil-to-lymphocyte ratio. Our findings showed a significant negative association between febrile seizure and platelet count, high C-reactive protein, and high ferritin levels. Additionally, the febrile seizure group showed a significant positive correlation with high neutrophil-to-lymphocyte ratio values (≥1.04) and body temperature (≥38). Our findings revealed that high neutrophil-to-lymphocyte ratio, high C-reactive protein, and age less than 18 months were independently associated with seizure susceptibility in febrile children.

CONCLUSION

High neutrophil-to-lymphocyte ratio values and low prognostic nutritional index scores may serve as novel surrogate independent factors for seizure susceptibility in febrile children. Febrile children who are less than 18 months old are more prone to experience seizures than older febrile children. Moreover, there was a correlation between febrile seizures and elevated C-reactive protein levels and neutrophil-to-lymphocyte ratio values.

Saiga antelope horn suppresses febrile seizures in rats by regulating neurotransmitters and the arachidonic acid pathway

BACKGROUND

Saiga antelope horn (SAH) is a traditional Chinese medicine for treating febrile seizure (FS) with precise efficacy, but its mechanism of action and functional substances are still unclear. Given the need for further research on SAH, our group conducted studies to elucidate its mechanisms and active substances.

METHODS

An FS rat pup model was constructed through intraperitoneal injection of LPS and hyperthermia induction. Behavioural indicators of seizures, hippocampal histopathological alterations, serum levels of inflammatory cytokines and hippocampal levels of neurotransmitters were observed and measured to investigate the effects of SAH on FS model rats. Hippocampal metabolomics and network pharmacology analyses were conducted to reveal the differential metabolites, key peptides and pathways involved in the suppression of FS by SAH.

RESULTS

SAH suppressed FS, decreased the inflammatory response and regulated the Glu-GABA balance. Metabolomic analysis revealed 13 biomarkers of FS, of which SAH improved the levels of 8 differential metabolites. Combined with network pharmacology, a "biomarker-core target-key peptide" network was constructed. The peptides of SAH, such as YGQL and LTGGF, could exert therapeutic effects via the arachidonic acid pathway. Molecular docking and ELISA results indicated that functional peptides of SAH could bind to PTGS2 target, inhibiting the generation of AA and its metabolites in hippocampal samples.

CONCLUSION

In summary, the functional peptides contained in SAH are the main material basis for the treatment of FS, potentially acting through neurotransmitter regulation and the arachidonic acid pathway.

Best practices for the management of febrile seizures in children

Febrile seizures (FS) are commonly perceived by healthcare professionals as a self-limited condition with a generally 'benign' nature. Nonetheless, they frequently lead to pediatric consultations, and their management can vary depending on the clinical context. For parents and caregivers, witnessing a seizure can be a distressing experience, significantly impacting their quality of life. In this review, we offer an in-depth exploration of FS management, therapeutic interventions, and prognostic factors, with the aim of providing support for physicians and enhancing communication with families. We conducted a comprehensive literature search using the PubMed and Web of Science databases, spanning the past 50 years. The search terms utilized included "febrile seizure," "complex febrile seizure," "simple febrile seizure," in conjunction with "children" or "infant." Only studies published in English or those presenting evidence-based data were included in our assessment. Additionally, we conducted a cross-reference search to identify any additional relevant data sources. Our thorough literature search resulted in a compilation of references, with carefully selected papers thoughtfully integrated into this review.

The protective effect of breastfeeding on febrile seizures: a systematic review with meta-analysis

Several potential risk factors have been identified in the etiopathogenesis of febrile seizures (FS), including the type and extent of breastfeeding (BF). Given the lack of conclusive data, this study aims to systematically evaluate the evidence on the association between BF and FS. We conducted a systematic review and meta-analysis according to PRISMA guidelines. The search was conducted using descriptors for FS, BF, and formula feeding in MEDLINE, Embase, and Web of Science databases. We included observational studies that compared the incidence of FS between those who had ever breastfed and those who were formula fed. The study protocol was registered on the PROSPERO platform under the number CRD42023474906. A total of 1,893,079 participants from 8 datasets were included. Our main analysis showed no significant association of any type of BF on the incidence of FS compared with formula-fed children (OR: 0.84; CI: 0.67-1.04; I2 = 78%; Cochran's Q = 0.0001), although meta-regression showed that BF was associated with a lower incidence of FS in preterm infants. Our secondary outcome showed a significantly reduced incidence of FS in children who received BF exclusively (OR: 0.80; CI: 0.65-0.99; I2 = 70%; Cochran's Q = 0.02).    Conclusion: There was no significant reduction in the incidence of FS in those who were breastfed compared to formula feeding. However, our meta-regression analysis indicated an association between BF and a lower incidence of FS in preterm infants. Additionally, children who exclusively received BF had a significantly reduced incidence of FS. These findings should be further investigated in prospective cohorts. What is Known: • Breastfeeding can modify risk factors for febrile seizures, such as susceptibility to viral and bacterial infections, micronutrient deficiencies, and low birth weight. • However, studies have shown conflicting results regarding the impact of breastfeeding on febrile seizures. What is New: • When comparing any breastfeeding pattern with no breastfeeding, there is no significant difference in the incidence of febrile seizures. • When comparing exclusive breastfeeding with no breastfeeding, there may be a decrease in the occurrence of febrile seizures.

Video Analyses of Sudden Unexplained Deaths in Toddlers

BACKGROUND AND OBJECTIVES

More than 2,900 US children aged younger than 4 years die from unknown causes each year, accounting for more than 219,000 life years lost annually. They are mostly sleep-related and unwitnessed with unremarkable autopsies, limiting our understanding of death mechanisms. We sought to understand potential mechanisms of death by evaluating videos of sudden deaths in toddlers.

METHODS

In our registry of 301 sudden unexplained child deaths, a series of 7 consecutively enrolled cases with home video recordings of the child's last sleep period were independently assessed by 8 physicians for video quality, movement, and sound.

RESULTS

Four boys and 3 girls (13-27 months at death) with terminal videos shared similar demographic features to the 293 other registry cases without video recordings. Five video recordings were continuous and 2 were triggered by sound or motion. Two lacked audio. All continuous recordings included a terminal convulsive event lasting 8-50 seconds; 4 children survived for >2.5 minutes postconvulsion. Among discontinuous videos, time lapses limited review; 1 suggested a convulsive event. Six were prone with face down, and 1 had autopsy evidence of airway obstruction. Primary cardiac arrhythmias were not supported; all 7 children had normal cardiac pathology and whole-exome sequencing identified no known cardiac disease variants.

DISCUSSION

Audio-visual recordings in 7 toddlers with unexplained sudden deaths strongly implicate that deaths were related to convulsive seizures, suggesting that many unexplained sleep-related deaths may result from seizures.

The anticonvulsant effect of saiga horn on febrile seizures by regulating brain serotonin content and inhibiting neuroinflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Saiga antelope horn (SAH) is derived from the Saiga antelope (Saiga tatarica Linnaeus) of the bovidae family. SAH has been used for the treatment of febrile seizures (FS) in children for thousands of years in China. Due to the biological protection of Saiga antelope and its ethical reasons, the application of SAH has been widely restricted. Unfortunately, the field of artificial manufacturing of SAH is still blank at present. The mechanism of SAH in the treatment of FS is still unclear, which seriously hinders the further development of artificial antelope horns and the search for substitutes for SAH. At present, there is an urgent need to determine the mechanism of SAH in the treatment of FS, so as to provide a theoretical basis for artificial antelope horn and its substitutes.

AIM OF THE STUDY

To explore the anti-FS effect of natural SAH on FS rat model and its possible mechanism, and to provide a theoretical basis for the subsequent manufacture of artificial antelope horns and the search for the best substitutes.

MATERIALS AND METHODS

FS was induced by a warm water bath (48 ± 0.5 °C). The latency and seizure grade of FS were observed and recorded. Hematoxylin-eosin (HE) staining was used to observe the functional defect of hippocampal cells. The contents of tryptophan (TRP), serotonin (5-HT), IL-1β and TNF-a in rat brain tissue were determined by ELISA. qRT-PCR and Western blot were used to detect the expression of 5-HT synthesis related neurotransmitter receptors, catalytic enzymes and inflammatory factors in hippocampus. Immunofluorescence was used to observe the expression of TPH2 protein in the dorsal raphe nucleus of rat brain.

RESULTS

After pretreating rats with SAH, the seizure grade of FS was significantly reduced and the latency was prolonged. SAH can reduce the histological damage of hippocampal tissue induced by FS in rats. Further analysis of ELISA results showed that SAH significantly increased the levels of TRP and 5-HT in the brain of FS rats, and significantly decreased the levels of IL-1β and TNF-a. The results of QPCR showed that SAH could up-regulate the expression of ER-β and TPH2 mRNA and down-regulate the expression of IL-1β and TNF-ɑ mRNA in the hippocampus of rats. In addition, WB and immunofluorescence results showed that SAH could significantly up-regulate the expression of ER-β/TPH2/5-HT pathway in the hippocampus of FS rats and the expression of TPH2 protein in the raphe nucleus, but had no significant effect on SERT protein in the hippocampus of FS rats. In addition, ER-β protein inhibitor PHTPP significantly inhibited the therapeutic effect of SAH on FS rats.

CONCLUSIONS

The present study demonstrates that SAH has a significant anticonvulsant effect on the FS rat model. The mechanism may be related to the increase of TRP content and up-regulation the expression of ER-β/TPH2/5-HT signaling pathway in the brain of FS rats, thereby increasing the content of 5-HT in the brain and reducing the content of IL-1β and TNF-a in the brain.

Febrile Seizures: An Updated Narrative Review for Pediatric Ambulatory Care Providers

BACKGROUND

While generally self-limited, febrile seizures result in significant familial distress. Ambulatory pediatric care providers must be prepared to counsel families on the causes, risk factors, management principles, and prognosis of children with febrile seizures.

OBJECTIVE

To provide an updated, evidence-based review of febrile seizures focused on the needs of an ambulatory pediatric care provider.

METHODS

A narrative review of the literature prioritizing landmark articles, metanalyses, longitudinal population longitudinal cohort studies and national level guidelines.

RESULTS

Febrile seizures are aberrant physiological responses to fever in children caused by complex interactions of cytokine mediated neuroinflammation, environmental triggers, and genetic predisposition. Other than investigations to determine fever etiology, routine bloodwork, lumbar punctures, neuroimaging and electroencephalograms are low yield. The general prognosis is excellent, however, clinicians should be aware of long-term outcomes including: cognitive impairment with non-simple febrile seizures; neuropsychiatric associations; recurrent febrile seizure and epilepsy risk factors; and the association between complex febrile seizures and sudden unexpected death. Children with a high risk of recurrence, complex febrile seizures, limited access to care, or extreme parental anxiety may benefit from intermittent oral diazepam prophylaxis.

CONCLUSION

Clinicians should consider four management priorities: 1) terminating the seizure; 2) excluding critical differential diagnoses; 3) investigating fever etiology; and 4) providing adequate counselling to families. The clinical approach and prognosis of febrile seizure can be based on subtype. Children with non-simple (i.e. complex or febrile status epilepticus) febrile seizures require closer care than the vast majority of children with simple febrile seizures, who have excellent outcomes.

Development and validation of a predictive model for febrile seizures

Febrile seizures (FS) are the most prevalent type of seizures in children. Existing predictive models for FS exhibit limited predictive ability. To build a better-performing predictive model, a retrospective analysis study was conducted on febrile children who visited the Children's Hospital of Shanghai from July 2020 to March 2021. These children were divided into training set (n = 1453), internal validation set (n = 623) and external validation set (n = 778). The variables included demographic data and complete blood counts (CBCs). The least absolute shrinkage and selection operator (LASSO) method was used to select the predictors of FS. Multivariate logistic regression analysis was used to develop a predictive model. The coefficients derived from the multivariate logistic regression were used to construct a nomogram that predicts the probability of FS. The calibration plot, area under the receiver operating characteristic curve (AUC), and decision curve analysis (DCA) were used to evaluate model performance. Results showed that the AUC of the predictive model in the training set was 0.884 (95% CI 0.861 to 0.908, p < 0.001) and C-statistic of the nomogram was 0.884. The AUC of internal validation set was 0.883 (95% CI 0.844 to 0.922, p < 0.001), and the AUC of external validation set was 0.858 (95% CI 0.820 to 0.896, p < 0.001). In conclusion, the FS predictive model constructed based on CBCs in this study exhibits good predictive ability and has clinical application value.

Unexplained and Unexpected Pediatric Deaths: Forensic Review and New Perspectives

Unexplained and unexpected pediatric deaths are a major challenge in global healthcare. The role of the forensic pathologist is crucial in determining the cause and manner of death in these cases, although to date, there are many limitations in post-mortem diagnosis. The role of the autopsy and related forensic investigations become a fundamental tool to investigate and give an explanation for an unacceptable event, considering the young age of the victims. From this point of view, even today, it is necessary that this phenomenon is correctly recorded through standardized systems and universally accepted methods. Furthermore, it is essential that scientific research on this topic is increased through the implementation of universally accepted operating protocols recognizing real risk factors in order to prevent such events. The purpose of the study is to offer a review of the state of the art about unexplained pediatric death and, above all, to propose an international reporting platform, extending proper investigations not only to judicial cases but also to all the other cases of unexpected pediatric death.

Are brief febrile seizures benign? A systematic review and narrative synthesis

Febrile seizures affect 2%-5% of U.S. children and are considered benign although associated with an increased risk of epilepsy and, rarely, with sudden unexplained death. We compared rates of mortality, neurodevelopmental disorders, and neuropathology in young children with simple and complex febrile seizures to healthy controls. We systematically reviewed studies of 3- to 72-month-old children with simple or complex febrile seizures ≤30 min. We searched studies with outcome measures on mortality, neurodevelopment, or neuropathology through July 18, 2022. Bias risk was assessed per study design. Each outcome measure was stratified by study design. PROSPERO registration is CRD42022361645. Twenty-six studies met criteria reporting mortality (11), neurodevelopment (11), and neuropathology (13), including 2665 children with febrile seizures and 1206 seizure-free controls. Study designs varied: 15 cohort, 2 cross-sectional, 3 case-control, 5 series, and 1 case report. Mortality outcomes showed stark contrasts. Six cohort studies following children after febrile seizure (n = 1348) reported no deaths, whereas four child death series and 1 case report identified 24.1% (108/449) deaths associated with simple (n = 104) and complex (n = 3) febrile seizures ≤30 min. Minor hippocampal histopathological anomalies were common in sudden deaths with or without febrile seizure history. Most electroencephalography (EEG) studies were normal. Neuroimaging studies suggested increased right hippocampal volumes. When present, neurodevelopmental problems usually preexisted febrile-seizure onset. Risk bias was medium or high in 95% (18/19) of cohort and case-control studies vs medium to low across remaining study designs. Research on outcomes after simple or brief complex febrile seizures is limited. Cohort studies suffered from inadequate sample size, bias risk, and limited follow-up durations to make valid conclusions on mortality, neurodevelopment, and neuropathology. Sudden death registries, focused on a very small percentage of all cases, strongly suggest that simple febrile seizures are associated with increased mortality. Although most children with febrile seizures have favorable outcomes, longer-term prospective studies are needed.

Determinants of caregiver's knowledge and practices regarding childhood fever management in a developing setting: a multi-centre cross-sectional assessment

Introduction

Fever is both a sign of various diseases (chief of which are infectious in nature) and an adverse effect of certain interventions (e.g. vaccines, drugs) in the pediatric population. It elicits anxiety among caregivers and healthcare professionals alike resulting in non-evidence based practices, adverse medication administration events, waste of scarce resources and overutilization of health facilities. The determinants of these practices among caregivers in the domiciliary contexts have not been well characterized in developing settings.

Methods

We assessed the knowledge and practices of childhood fever and their determinants among caregivers in domiciliary settings in Northern Nigeria using a 41-item questionnaire between August 2020 and February 2021.

Results

The questionnaire is reliable (knowledge: Cronbach's Alpha = 0.689; practice: Cronbach's Alpha = 0.814) and collected data on a total of 2,400 caregiver-child pairs, who participated in the study. Over two-third (68.3%; 1,640) of the caregivers expressed fever phobic tendencies. Paracetamol was the most commonly used medication and constituted 31.3% of medication administration adverse events reported by the caregivers. Only one out of every six knowledgeable caregivers engaged in evidence-based home childhood fever management practices (7% vs. 41.6%) with being a primary caregiver [Knowledge: odd ratio (OR): 2.81, 95% CI: 0.38; 5.68; p value: 0.04; Practice: OR: 1.65, 95% CI: 0.09; 7.33; 0.02] and having a child/children aged ≤3 years (knowledge: OR: 7.03, 95% CI: 4.89; 9.67, p value: 0.003; practice OR: 3.11, 95% CI: 1.27; 8.59, 0.007) determining both the knowledge and practices of childhood fever management in a household.

Conclusions

The knowledge and practice of childhood fever management among caregivers were sub-optimal with being a primary caregiver and having a child/children aged ≤3 years being the significant determinants of each domain. These gaps underscore the dire need for targeted strategies aimed at improving childhood fever management by educating caregivers.

Comparison of Serum Selenium, Homocysteine, Zinc, and Vitamin D Levels in Febrile Children with and without Febrile Seizures: A Prospective Single-Center Study

OBJECTIVE

Febrile seizure is a complication that makes physicians and families uneasy when detected in children with a high fevers. This study aimed to compare children with febrile seizures and children without seizures in blood selenium, zinc, homocysteine, vitamin D, vitamin B12, and magnesium levels.

MATERIALS AND METHODS

The study group included sixty-one children between the ages of 1-5 who came to the pediatric emergency department with febrile seizure. The control group had 61 children with fever without seizure, who were compatible with the study group in age, sex, and elapsed time since the onset of fever. Blood samples were taken from the patients during their admission. Selenium, zinc, vitamin D, homocysteine, vitamin B12, and magnesium levels were measured, and the data of the two groups were compared. Additionally, patients in the study group had two subgroups, simple and complex febrile seizures, and their parameters were compared.

RESULTS

Selenium, zinc, vitamin D, and vitamin B12 levels were significantly lower in the study group than in the control group (p < 0.001), and there was no significant difference in homocysteine (p = 0.990) and magnesium levels (p = 0.787) between the two groups. Moreover, no significant difference was found between those with simple and complex febrile seizures in selenium, vitamin D, homocysteine, vitamin B12, and magnesium levels.

CONCLUSIONS

Elevated levels of selenium, zinc, vitamin D, and vitamin B12 in the blood of children with fevers help to prevent febrile seizures.

Copy Number Variation and Structural Genomic Findings in 116 Cases of Sudden Unexplained Death between 1 and 28 Months of Age

In sudden unexplained death in pediatrics (SUDP) the cause of death is unknown despite an autopsy and investigation. The role of copy number variations (CNVs) in SUDP has not been well-studied. Chromosomal microarray (CMA) data are generated for 116 SUDP cases with age at death between 1 and 28 months. CNVs are classified using the American College of Medical Genetics and Genomics guidelines and CNVs in our cohort are compared to an autism spectrum disorder (ASD) cohort, and to a control cohort. Pathogenic CNVs are identified in 5 of 116 cases (4.3%). Variants of uncertain significance (VUS) favoring pathogenic CNVs are identified in 9 cases (7.8%). Several CNVs are associated with neurodevelopmental phenotypes including seizures, ASD, developmental delay, and schizophrenia. The structural variant 47,XXY is identified in two cases (2/69 boys, 2.9%) not previously diagnosed with Klinefelter syndrome. Pathogenicity scores for deletions are significantly elevated in the SUDP cohort versus controls (p = 0.007) and are not significantly different from the ASD cohort. The finding of pathogenic or VUS favoring pathogenic CNVs, or structural variants, in 12.1% of cases, combined with the observation of higher pathogenicity scores for deletions in SUDP versus controls, suggests that CMA should be included in the genetic evaluation of SUDP.

Inflammation as a target for the treatment of fever-associated epilepsy in zebrafish larvae

Inflammation is considered to be involved in epileptogenesis. However, the relationship between fever and inflammation as well as the mechanisms of fever in the occurrence and development of childhood epilepsy need further investigation. Here, we described an in vivo model of hyperthermia-induced seizures in zebrafish larvae with pentylenetetrazole (PTZ) exposure. Hyperthermia increased the susceptibility to seizure and the production of pro-inflammatory factors in PTZ-induced zebrafish larvae. As mutations in GABRG2 have been associated with fever-associated epilepsy, we used a Tg(hGABRG2^F343L) zebrafish model expressing mutant human GABRG2(F343L) to further investigate the involvement of inflammation in fever-induced seizures. Our data indicated that hyperthermia also increased the locomotor activity in Tg(hGABRG2^F343L) zebrafish larvae. Although the production of pro-inflammatory factors was upregulated by GABRG2 mutation, hyperthermia did not change the production of pro-inflammatory factors significantly. Lipopolysaccharide (LPS) stimulation was sufficient to increase the locomotor activity in zebrafish larvae, suggesting that inflammation contributed to fever-associated epilepsy. The expression of GABRG2 was increased with PTZ induction, especially at a higher temperature. Moreover, inhibition of inflammation by dexamethasone (DEX) reduced the excitability of zebrafish larvae, especially at a higher temperature. Finally, in vitro experiments proved that LPS stimulation increased the production of IL-1β and IL-6 in GABRG2(F343L) transfected cells. Collectively, our study demonstrated that neuroinflammation was induced in febrile seizures, and the increased expression of IL-1β and IL-6 might be responsible for epileptogenesis. The vicious cycle between fever and inflammation might induce seizure onset, and anti-inflammatory strategies might be a potential treatment for fever-associated epilepsy.

Autonomic dysfunction in epilepsy mouse models with implications for SUDEP research

Epilepsy has a high prevalence and can severely impair quality of life and increase the risk of premature death. Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death in drug-resistant epilepsy and most often results from respiratory and cardiac impairments due to brainstem dysfunction. Epileptic activity can spread widely, influencing neuronal activity in regions outside the epileptic network. The brainstem controls cardiorespiratory activity and arousal and reciprocally connects to cortical, diencephalic, and spinal cord areas. Epileptic activity can propagate trans-synaptically or via spreading depression (SD) to alter brainstem functions and cause cardiorespiratory dysfunction. The mechanisms by which seizures propagate to or otherwise impair brainstem function and trigger the cascading effects that cause SUDEP are poorly understood. We review insights from mouse models combined with new techniques to understand the pathophysiology of epilepsy and SUDEP. These techniques include in vivo, ex vivo, invasive and non-invasive methods in anesthetized and awake mice. Optogenetics combined with electrophysiological and optical manipulation and recording methods offer unique opportunities to study neuronal mechanisms under normal conditions, during and after non-fatal seizures, and in SUDEP. These combined approaches can advance our understanding of brainstem pathophysiology associated with seizures and SUDEP and may suggest strategies to prevent SUDEP.

De novo mutations in childhood cases of sudden unexplained death that disrupt intracellular Ca2+ regulation

Approximately 400 United States children 1 y of age and older die suddenly from unexplained causes annually. We studied whole-exome sequence data from 124 “trios” (decedent child and living parents) to identify genetic risk factors. Nonsynonymous mutations, mostly de novo (present in child but absent in both biological parents), were highly enriched in genes associated with cardiac and seizure disorders relative to controls, and contributed to 9% of deaths. We found significant overtransmission of loss-of-function or pathogenic missense variants in cardiac and seizure disorder genes. Most pathogenic variants were de novo in origin, highlighting the importance of trio studies. Many of these pathogenic de novo mutations altered a protein network regulating calcium-related excitability at submembrane junctions in cardiomyocytes and neurons.

Sudden unexplained death in childhood (SUDC) is an understudied problem. Whole-exome sequence data from 124 “trios” (decedent child, living parents) was used to test for excessive de novo mutations (DNMs) in genes involved in cardiac arrhythmias, epilepsy, and other disorders. Among decedents, nonsynonymous DNMs were enriched in genes associated with cardiac and seizure disorders relative to controls (odds ratio = 9.76, P = 2.15 × 10⁻⁴). We also found evidence for overtransmission of loss-of-function (LoF) or previously reported pathogenic variants in these same genes from heterozygous carrier parents (11 of 14 transmitted, P = 0.03). We identified a total of 11 SUDC proband genotypes (7 de novo, 1 transmitted parental mosaic, 2 transmitted parental heterozygous, and 1 compound heterozygous) as pathogenic and likely contributory to death, a genetic finding in 8.9% of our cohort. Two genes had recurrent missense DNMs, RYR2 and CACNA1C. Both RYR2 mutations are pathogenic (P = 1.7 × 10⁻⁷) and were previously studied in mouse models. Both CACNA1C mutations lie within a 104-nt exon (P = 1.0 × 10⁻⁷) and result in slowed L-type calcium channel inactivation and lower current density. In total, six pathogenic DNMs can alter calcium-related regulation of cardiomyocyte and neuronal excitability at a submembrane junction, suggesting a pathway conferring susceptibility to sudden death. There was a trend for excess LoF mutations in LoF intolerant genes, where ≥1 nonhealthy sample in denovo-db has a similar variant (odds ratio = 6.73, P = 0.02); additional uncharacterized genetic causes of sudden death in children might be discovered with larger cohorts.

Seizure-related deaths in children: The expanding spectrum

Although seizures are common in children, they are often overlooked as a potential cause of death. Febrile and nonfebrile seizures can be fatal in children with or without an epilepsy diagnosis and may go unrecognized by parents or physicians. Sudden unexpected infant deaths, sudden unexplained death in childhood, and sudden unexpected death in epilepsy share clinical, neuropathological, and genetic features, including male predominance, unwitnessed deaths, death during sleep, discovery in the prone position, hippocampal abnormalities, and variants in genes regulating cardiac and neuronal excitability. Additionally, epidemiological studies reveal that miscarriages are more common among individuals with a personal or family history of epilepsy, suggesting that some fetal losses may result from epileptic factors. The spectrum of seizure-related deaths in pediatrics is wide and underappreciated; accurately estimating this mortality and understanding its mechanism in children is critical to developing effective education and interventions to prevent these tragedies.

Febrile Seizures and Respiratory Viruses Determined by Multiplex Polymerase Chain Reaction Test and Clinical Diagnosis

Febrile seizure (FS) is a common benign seizure disorder of young children. Although upper respiratory tract infection is the cause of fever in most episodes of FS, studies to identify respiratory viruses using a multiplex polymerase chain reaction (mPCR) test have rarely been performed for children with FS. Medical records of children presenting with FS between January 2015 and December 2019 were retrospectively reviewed. Respiratory viruses identified by a rapid influenza detection test and mPCR test were investigated, and their seasonal distribution and the association between viral identification and seizure characteristics were determined. A total of 607 episodes of FS were analyzed: 81.1% of cases were generalized tonic–clonic seizures, 81.5% occurred within 24 h after fever onset, and 87.3% continued for ≤5 min. Complex FS occurred in 17.5% of FS episodes, and epilepsy was diagnosed in 2.5% of tracked cases. Of the 138 mPCR tests performed in 235 hospitalized episodes of FS, 112 (81.2%) tested positive for respiratory viruses: rhinovirus, enterovirus, adenovirus, and influenza virus were most frequently identified. The identified respiratory viruses showed similar seasonal distributions as were observed in community-acquired respiratory tract infections. The identification of a specific respiratory virus was not significantly associated with seizure characteristics or the development of complex FS. In conclusion, respiratory viruses, showing similar seasonal distributions with community-acquired respiratory tract infections and no significant association with the severity and outcomes of FS, should not be rigorously tested for in children with FS.

Current understanding of febrile seizures and their long-term outcomes

In this paper we reframe febrile seizures, which are viewed as a symptom of an underlying brain disorder. The general observation is that a small cohort of children will develop febrile seizures (2-5% in the West), while the greater majority will not. This suggests that the brain that generates a seizure, in an often-mild febrile context, differs in some ways from the brain that does not. While the underlying brain disorder appears to have no significant adverse implication in the majority of children with febrile seizures, serious long-term outcomes (cognitive and neuropsychiatric) have been recently reported, including sudden death. These adverse events likely reflect the underlying intrinsic brain pathology, as yet undefined, of which febrile seizures are purely a manifestation and not the primary cause. A complex interaction between brain-genetics-epigenetics-early environment is likely at play. In view of this emerging data, it is time to review whether febrile seizures are a single entity, with a new and multidimensional approach needed to help with predicting outcome. WHAT THIS PAPER ADDS: A febrile seizure is due to a brain's aberrant response to high temperature. Problems in a small group of children are now being identified later in life. There is no clear correlation between duration or other characteristics of febrile seizures and subsequent mesial temporal sclerosis.

Sudden Unexplained Death in Childhood: A Neuropathology Review

Sudden Unexplained Death in Childhood (SUDC) is the unexpected death of a child over age 12 months that remains unexplained after a thorough case investigation, including review of the child's medical history, circumstances of death, a complete autopsy and ancillary testing (1). First defined in 2005, SUDC cases are more often male, with death occurring during a sleep period, being found prone, peak winter incidence, associated with febrile seizure history in ~28% of cases and mild pathologic changes insufficient to explain the death (1, 2). There has been little progress in understanding the causes of SUDC and no progress in prevention. Despite reductions in sudden unexpected infant death (SUID) and other causes of mortality in childhood, the rate of SUDC has increased during the past two decades (3-5). In Ireland, SUID deaths were cut in half from 1994 to 2008 while SUDC deaths more than doubled (4). Surveillance issues, including lack of standardized certification practices, affect our understanding of the true magnitude of unexplained child deaths. Mechanisms underlying SUDC, like SUID, remain largely speculative. Limited and inconsistent evidence implicates abnormalities in brainstem autonomic and serotonergic nuclei, critical for arousal, cardiorespiratory control, and reflex responses to life-threatening hypoxia or hypercarbia in sleep (6). Abnormalities in medullary serotonergic neurons and receptors, as well as cardiorespiratory brainstem nuclei occur in some SUID cases, but have never been studied in SUDC. Retrospective, small SUDC studies with non-standardized methodologies most often demonstrate minor hippocampal abnormalities, as well as focal cortical dysplasia and dysgenesis of the brainstem and cerebellum. The significance of these findings to SUDC pathogenesis remains unclear with some investigators and forensic pathologists labeling these findings as normal variants, or potential causes of SUDC. The development of preventive strategies will require a greater understanding of underlying mechanisms.

Evaluation of Concordance Between Original Death Certifications and an Expert Panel Process in the Determination of Sudden Unexplained Death in Childhood

Importance

The true incidence of sudden unexplained death in childhood (SUDC), already the fifth leading category of death among toddlers by current US Centers for Disease Control and Prevention estimates, is potentially veiled by the varied certification processes by medicolegal investigative offices across the United States.

Objective

To evaluate the frequency of SUDC incidence, understand its epidemiology, and assess the consistency of death certification among medical examiner and coroner offices in the US death investigation system.

Design, Setting, and Participants

In this case series, 2 of 13 forensic pathologists (FPs) conducted masked reviews of 100 cases enrolled in the SUDC Registry and Research Collaborative (SUDCRRC). Children who died aged 11 months to 18 years from 36 US states, Canada, and the United Kingdom had been posthumously enrolled in the SUDCRRC by family members from 2014 to 2017. Comprehensive data from medicolegal investigative offices, clinical offices, and family members were reviewed. Data analysis was conducted from December 2014 to June 2020.

Main Outcomes and Measures

Certified cause of death (COD) characterized as explained (accidental or natural) or unexplained, as determined by SUDCRRC masked review process.

Results

In this study of 100 cases of SUDC (mean [SD] age, 32.1 [31.8] months; 58 [58.0%] boys; 82 [82.0%] White children; 92 [92.0%] from the United States), the original pathologist certified 43 cases (43.0%) as explained COD and 57 (57.0%) as unexplained COD. The SUDCRRC review process led to the following certifications: 16 (16.0%) were explained, 7 (7.0%) were undetermined because of insufficient data, and 77 (77.0%) were unexplained. Experts disagreed with the original COD in 40 cases (40.0%). These data suggest that SUDC incidence is higher than the current Centers for Disease Control and Prevention estimate (ie, 392 deaths in 2018).

Conclusions and Relevance

To our knowledge, this is the first comprehensive masked forensic pathology review process of sudden unexpected pediatric deaths, and it suggests that SUDC may often go unrecognized in US death investigations. Some unexpected pediatric deaths may be erroneously attributed to a natural or accidental COD, negatively affecting surveillance, research, public health funding, and medical care of surviving family members. To further address the challenges of accurate and consistent death certification in SUDC, future studies are warranted.

Hippocampal abnormalities and seizures: a 16-year single center review of sudden unexpected death in childhood, sudden unexpected death in epilepsy and SIDS

Sudden Unexpected Death in Childhood (SUDC) is the unexplained death of children aged between 1 and 18 years old. Hippocampal abnormalities have previously been described in Sudden Unexpected Death in Epilepsy (SUDEP) and it is possible that SUDC shares similar pathogenic mechanisms with SUDEP. Our aim was to determine the prevalence of hippocampal abnormalities, history of seizures and demographic features in our caseload of SUDC, SUDEP and SIDS cases. A review of post-mortem reports from 2003 to 2018 was carried out to identify cases of SUDC, SUDEP and SIDS. Histological evidence of hippocampal abnormalities, patient demographics (age, gender), sleeping position, and past medical history (history of seizures and illness 72 hours prior to death) were recorded. Statistical analysis was performed to compare the three groups. 48 SUDC, 18 SUDEP and 358 SIDS cases were identified. Hippocampal abnormalities associated with temporal lobe epilepsy were found in 44.4% of SUDC cases. 5/15 SUDC cases with a history of seizures demonstrated hippocampal abnormalities. SUDC cases were also more likely to be found prone compared to SIDS cases. In comparison with SIDS, both SUDC and SUDEP cases were more likely to demonstrate hippocampal abnormalities (SUDC: (OR = 9.4, 95% CI: 3.1-29.1, p < 0.001; SUDEP: OR = 35.4, 95% CI: 8.3-151.5, p < 0.001). We found a potential link between hippocampal abnormalities and epileptic seizures in SUDC. A concerted effort should be directed towards consistent sampling and standardized description of the hippocampus and clinical correlation with a history of seizures/epilepsy in postmortem reports.

Causality assessment of adverse events following immunization: the problem of multifactorial pathology

The analysis of Adverse Events Following Immunization (AEFI) is important in a balanced epidemiological evaluation of vaccines and in the issues related to national vaccine injury compensation programs. If manufacturing defects or vaccine storage and delivering errors are excluded, the majority of adverse reactions to vaccines occur as excessive or biased inflammatory and immune responses. These unwanted phenomena, occasionally severe, are associated with many different endogenous and exogenous factors, which often interact in complex ways. The confirmation or denial of the causal link between an AEFI and vaccination is determined pursuant to WHO guidelines, which propose a four-step analysis and algorithmic diagramming. The evaluation process from the onset considers all possible "other causes" that can explain the AEFI and thus exclude the role of the vaccine. Subsequently, even if there was biological plausibility and temporal compatibility for a causal association between the vaccine and the AEFI, the guidelines ask to look for any possible evidence that the vaccine could not have caused that event. Such an algorithmic method presents some concerns that are discussed here, in the light of the multifactorial nature of the inflammatory and immune pathologies induced by vaccines, including emerging knowledge of genetic susceptibility to adverse effects. It is proposed that the causality assessment could exclude a consistent association of the adverse event with the vaccine only when the presumed "other cause" is independent of an interaction with the vaccine. Furthermore, the scientific literature should be viewed not as an exclusion criterion but as a comprehensive analysis of all the evidence for or against the role of the vaccine in causing an adverse reaction. These issues are discussed in relation to the laws that, in some countries, regulate the mandatory vaccinations and the compensation for those who have suffered serious adverse effects.

Causality assessment of adverse events following immunization: the problem of multifactorial pathology

The analysis of Adverse Events Following Immunization (AEFI) is important in a balanced epidemiological evaluation of vaccines and in the issues related to vaccine injury compensation programs. The majority of adverse reactions to vaccines occur as excessive or biased inflammatory and immune responses. These unwanted phenomena, occasionally severe, are associated with many different endogenous and exogenous factors, which often interact in complex ways. The confirmation or denial of the causal link between an AEFI and vaccination is determined pursuant to WHO guidelines, which propose a four-step analysis and algorithmic diagramming. The evaluation process from the onset considers all possible "other causes" that might explain the AEFI and thus exclude the role of the vaccine. Subsequently, even if there was biological plausibility and temporal compatibility for a causal association between the vaccine and the AEFI, the guidelines ask to look for any possible evidence that the vaccine could not have caused that event. Such an algorithmic method presents several concerns that are discussed here, in the light of the multifactorial nature of the inflammatory and immune pathologies induced by vaccines, including emerging knowledge of genetic susceptibility to adverse effects. It is proposed that the causality assessment could exclude a consistent association of the adverse event with the vaccine only when the presumed "other cause" is independent of an interaction with the vaccine. Furthermore, the scientific literature should be viewed not as an exclusion criterion but as a comprehensive analysis of all the evidence for or against the role of the vaccine in causing an adverse reaction. Given these inadequacies in the evaluation of multifactorial diseases, the WHO guidelines need to be reevaluated and revised. These issues are discussed in relation to the laws that, in some countries, regulate the mandatory vaccinations and the compensation for those who have suffered serious adverse effects.

Neuropathologic Changes in Sudden Unexplained Death in Childhood

Sudden unexplained death in childhood (SUDC) affects children >1-year-old whose cause of death remains unexplained following comprehensive case investigation and is often associated with hippocampal abnormalities. We prospectively performed systematic neuropathologic investigation in 20 SUDC cases, including (i) autopsy data and comprehensive ancillary testing, including molecular studies, (ii) ex vivo 3T MRI and extensive histologic brain samples, and (iii) blinded neuropathology review by 2 board-certified neuropathologists. There were 12 girls and 8 boys; median age at death was 33.3 months. Twelve had a history of febrile seizures, 85% died during apparent sleep and 80% in prone position. Molecular testing possibly explained 3 deaths and identified genetic mutations in TNNI3, RYR2, and multiple chromosomal aberrations. Hippocampal abnormalities most often affected the dentate gyrus (altered thickness, irregular configuration, and focal lack of granule cells), and had highest concordance between reviewers. Findings were identified with similar frequencies in cases with and without molecular findings. Number of seizures did not correlate with hippocampal findings. Hippocampal alterations were the most common finding on histological review but were also found in possibly explained deaths. The significance and specificity of hippocampal findings is unclear as they may result from seizures, contribute to seizure pathogenesis, or be an unrelated phenomenon.