Faculty Bibliography

BACKGROUND:Febrile seizures occur in 3%-4% of US children aged six months to five years and are considered benign. However, sudden unexplained death in childhood is associated with 10 times increase in febrile seizures. We assessed the characteristics of children with febrile seizure and sudden death to identify factors that confer increased sudden death risk. METHODS:We conducted a case-control analysis of children with febrile seizure and subsequent sudden death versus living controls from December 2021 to June 2023 through an ∼10-minute anonymous online survey. We enrolled parents of children, living or deceased, whose child had experienced a febrile seizure from age six months to six years. Subjects were excluded if the child had an afebrile seizure or parents had not witnessed a febrile seizure. Demographic characteristics, parasomnias, and febrile seizure features were analyzed. RESULTS:A total of 381 completed surveys were received; 53 (14%) cases of febrile seizure with sudden death and 328 (86%) living controls. Cases reported febrile seizure onset >2 months earlier (P = 0.013) and reported developmental concerns (odds ratio [OR] = 2.32, 95% confidence interval [CI] [1.14, 4.71], P = 0.03), less frequent night awakenings (OR = 0.34, 95% CI [0.18, 0.65], P = 0.001), and less restless sleep (OR = 0.37, 95% CI [0.16, 0.85], P = 0.02). Cases were also less likely to drool (OR = 0.442, 95% CI [0.218, 0.900], P = 0.032) or be unresponsive for more than one minute (OR = 0.45, 95% CI [0.238, 0.854], P = 0.021). CONCLUSIONS:We report novel associations of febrile seizure and sudden death related to age, development, sleep, and observed ictal features. Anonymous survey methodology cannot exclude ascertainment bias and any related potential effect on results. Our findings suggest that impaired arousal mechanisms may increase risk of death in subjects with febrile seizure.

Sudden unexplained death in childhood (SUDC) is death of a child ≥ 12 months old that is unexplained after autopsy and detailed analyses. Among SUDC cases, ~ 30% have febrile seizure (FS) history, versus 2-5% in the general population. SUDC cases share features with sudden unexpected death in epilepsy (SUDEP) and sudden infant death syndrome (SIDS), in which brainstem autonomic dysfunction is implicated. To understand whether brainstem protein changes are associated with FS history in SUDC, we performed label-free quantitative mass spectrometry on microdissected midbrain dorsal raphe, medullary raphe, and the ventrolateral medulla (n = 8 SUDC-noFS, n = 11 SUDC-FS). Differential expression analysis between SUDC-FS and SUDC-noFS at p < 0.05 identified 178 altered proteins in dorsal raphe, 344 in medullary raphe, and 100 in the ventrolateral medulla. These proteins were most significantly associated with increased eukaryotic translation initiation (p = 3.09 × 10^-7, z = 1.00), eukaryotic translation elongation (p = 6.31 × 10^-49, z = 6.01), and coagulation system (p = 1.32 × 10^-5, z = 1.00). The medullary raphe had the strongest enrichment for altered signaling pathways, including with comparisons to three other brain regions previously analyzed (frontal cortex, hippocampal dentate gyrus, cornu ammonus). Immunofluorescent tissue analysis of serotonin receptors identified 2.1-fold increased 5HT2A in the medullary raphe of SUDC-FS (p = 0.025). Weighted gene correlation network analysis (WGCNA) of case history indicated that longer FS history duration significantly correlated with protein levels in the medullary raphe and ventrolateral medulla; the most significant gene ontology biological processes were decreased cellular respiration (p = 9.8 × 10^-5, corr = - 0.80) in medullary raphe and decreased synaptic vesicle cycle (p = 1.60 × 10^-7, corr = - 0.90) in the ventrolateral medulla. Overall, FS in SUDC was associated with more protein differences in the medullary raphe and was related with increased translation-related signaling pathways. Future studies should assess whether these changes result from FS or may in some way predispose to FS or SUDC.

BACKGROUND AND OBJECTIVES/OBJECTIVE: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/CONCLUSIONS: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.

Febrile seizures affect 2-5% of U.S. children and are considered benign although associated with an increased risk of epilepsy and rarely, 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 3-72-month-old children with simple or complex febrile seizures <30 minutes. 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, while four child death series and case report identified 24.1% (108/449) deaths associated with simple (n=104) and complex (n=3) febrile seizures <30 minutes. Minor hippocampal histopathological anomalies were common in sudden deaths with or without febrile seizure history. Most 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) cohort and case-control studies versus medium to low across remaining studies 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 simple febrile seizures are associated with increased mortality. While most children with febrile seizures have favorable outcomes, longer-term prospective studies are needed.

Sudden unexplained death in childhood (SUDC) is death of a child over 1 year of age that is unexplained after review of clinical history, circumstances of death, and complete autopsy with ancillary testing. Multiple etiologies may cause SUDC. SUDC and sudden unexpected death in epilepsy (SUDEP) share clinical and pathological features, suggesting some similarities in mechanism of death and possible abnormalities in hippocampus and cortex. To identify molecular signaling pathways, we performed label-free quantitative mass spectrometry on microdissected frontal cortex, hippocampal dentate gyrus (DG), and cornu ammonis (CA1-3) in SUDC (n = 19) and pediatric control cases (n = 19) with an explained cause of death. At a 5% false discovery rate (FDR), we found differential expression of 660 proteins in frontal cortex, 170 in DG, and 57 in CA1-3. Pathway analysis of altered proteins identified top signaling pathways associated with activated oxidative phosphorylation (p = 6.3 × 10^-15, z = 4.08) and inhibited EIF2 signaling (p = 2.0 × 10^-21, z = - 2.56) in frontal cortex, and activated acute phase response in DG (p = 8.5 × 10^-6, z = 2.65) and CA1-3 (p = 4.7 × 10^-6, z = 2.00). Weighted gene correlation network analysis (WGCNA) of clinical history indicated that SUDC-positive post-mortem virology (n = 4/17) had the most significant module in each brain region, with the top most significant associated with decreased mRNA metabolic processes (p = 2.8 × 10^-5) in frontal cortex. Additional modules were associated with clinical history, including fever within 24 h of death (top: increased mitochondrial fission in DG, p = 1.8 × 10^-3) and febrile seizure history (top: decreased small molecule metabolic processes in frontal cortex, p = 8.8 × 10^-5) in all brain regions, neuropathological hippocampal findings in the DG (top: decreased focal adhesion, p = 1.9 × 10^-3). Overall, cortical and hippocampal protein changes were present in SUDC cases and some correlated with clinical features. Our studies support that proteomic studies of SUDC cohorts can advance our understanding of the pathogenesis of these tragedies and may inform the development of preventive strategies.

AIMS/OBJECTIVE:Hippocampal findings are implicated in the pathogenesis of sudden unexplained death in childhood (SUDC), although some studies have identified similar findings in sudden explained death in childhood (SEDC) cases. We blindly reviewed hippocampal histology in SUDC and SEDC controls. METHODS:Hippocampal H&E slides (n=67; 36 SUDC, 31 controls) from clinical and forensic collaborators were evaluated by 9 blinded reviewers: 3 board-certified forensic pathologists, 3 neuropathologists, and 3 dual-certified neuropathologist/forensic pathologists. RESULTS:Among nine reviewers, about 50% of hippocampal sections were rated as abnormal (SUDC 52.5%, controls 53.0%), with no difference by cause of death (COD) (p=0.16) or febrile seizure history (p=0.90). There was little agreement among nine reviewers on whether a slide was within normal range (Fleiss' kappa=0.014, p=0.47). Within reviewer groups, there were no findings more frequent in SUDC compared to controls, with variability in pyramidal neuron and dentate gyrus findings. Across reviewer groups, there was concordance for bilamination and granule cell loss. Neither SUDC (51.2%) nor control (55.9%) slides were considered contributory to determining COD (p=0.41). CONCLUSIONS:The lack of an association of hippocampal findings in SUDC and controls, as well as inconsistency of observations by multiple blinded reviewers, indicates discrepancy with previous studies and an inability to reliably identify hippocampal malformation associated with sudden death (HMASD). These findings underscore a need for larger studies to standardize evaluation of hippocampal findings, identify the range of normal variation and, changes unrelated to SUDC or febrile seizures. Molecular studies may help identify novel immunohistological markers that inform on COD.

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.

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.

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

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.