Increased Risk Of Sudden Unexpected Death In Epilepsy Research Articles

Single-nuclear RNA sequencing reveals sex-specific differences in cell composition and recruitment of neuroinflammatory pathways after repeated seizures within the NA/pre-Bötzinger Complex region

Epilepsy affects millions worldwide, but a significant portion suffers from uncontrollable epilepsy. Repeated seizures have many consequences, including a high risk of post-ictal cardiorespiratory failure and Sudden Unexpected Death in Epilepsy (SUDEP). Major risk factors for SUDEP include biological sex and the occurrence of generalized tonic-clonic seizures (GTCSs). How repeated seizures lead to cardiorespiratory dysfunction remains unknown. It was reported that a key factor in many neurological diseases is neuroinflammation, which is mediated mostly by microglia and astrocytes that become dysfunctional. Mechanistically, questions remain how they affect neuronal function in epilepsy and contribute to cardiorespiratory dysfunction and increased SUDEP risk. Here we tested the hypothesis that repeated seizures lead to differential neuroinflammatory activation after repeated seizures in CNS regions of ventilatory control in a sex-specific manner. Preliminary data in our novel rat model with genetic mutations in Kcnj16, a gene encoding an inwardly-rectifying potassium channel Kir5.1 in Dahl salt-sensitive rat (SS kcnj16-/- ) show that repeated sound-induced seizures lead to progressively more severe post-ictal suppression of breathing frequency and heart rate and increased mortality in males. Single-nuclear RNA sequencing of Nucleus Ambiguous/pre-Bötzinger Complex (NA/preBötC) cells (roughly 80,000 and 40,000) was performed in tissues from male and female SS kcnj16-/- rats (n=3/group) exposed to 0, 3, 7, or 10 seizures to measure cell type-specific gene expression changes induced by seizures. Bioinformatic analyses of transcriptomic changes across sex revealed the identification of 19 unique cell types in males and 21 unique cell types in females in this brainstem region. Differentially expressed genes (DEGs; Seurat) in both males and females showed significant ( p<0.05) recruitment of various inflammatory and stress-related pathways (e.g. CXCR4 signaling, Immunogenic Cell Death Signaling). Data integration across sex enabled sex-specific comparisons across days of the seizure (around 120,000 cells). Importantly, males show significant upregulation in DEGs with seizures in mTOR signaling and Extracellular Neutrophil Trap Signaling when compared to females. Importantly, this dataset helps characterize at a genetic and cell-type specific manner, sex differences in a crucial region not characterized before in the literature. Also, these data show clear sex differences in the cellular milieu and transcriptomic profiles in the NA/preBötC region before and after repeated seizures, suggesting different neuroinflammatory pathways may play a larger role in males than females. Understanding sex differences and how they may be playing a role in neuroinflammaton after repeated seizures may provide novel insights into identifying new therapeutic drugs aimed at reducing the risk of SUDEP in males and, more broadly, those suffering from uncontrolled epilepsy. Supported by HL122358, HL160122 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Risk of sudden unexpected death in epilepsy (SUDEP) with lamotrigine and other sodium channel-modulating antiseizure medications.

In vitro data prompted U.S Food and Drug Administration warnings that lamotrigine, a common sodium channel modulating anti-seizure medication (NaM-ASM), could increase the risk of sudden death in patients with structural or ischaemic cardiac disease, however, its implications for Sudden Unexpected Death in Epilepsy (SUDEP) are unclear. This retrospective, nested case-control study identified 101 sudden unexpected death in epilepsy (SUDEP) cases and 199 living epilepsy controls from Epilepsy Monitoring Units (EMUs) in Australia and the USA. Differences in proportions of lamotrigine and NaM-ASM use were compared between cases and controls at the time of admission, and survival analyses from the time of admission up to 16 years were conducted. Multivariable logistic regression and survival analyses compared each ASM subgroup adjusting for SUDEP risk factors. Proportions of cases and controls prescribed lamotrigine (P=0.166), one NaM-ASM (P=0.80), or ≥2NaM-ASMs (P=0.447) at EMU admission were not significantly different. Patients taking lamotrigine (adjusted hazard ratio [aHR]=0.56; P=0.054), one NaM-ASM (aHR=0.8; P=0.588) or ≥2 NaM-ASMs (aHR=0.49; P=0.139) at EMU admission were not at increased SUDEP risk up to 16 years following admission. Active tonic-clonic seizures at EMU admission associated with >2-fold SUDEP risk, irrespective of lamotrigine (aHR=2.24; P=0.031) or NaM-ASM use (aHR=2.25; P=0.029). Sensitivity analyses accounting for incomplete ASM data at follow-up suggest undetected changes to ASM use are unlikely to alter our results. This study provides additional evidence that lamotrigine and other NaM-ASMs are unlikely to be associated with an increased long-term risk of SUDEP, up to 16 years post-EMU admission.

Single Nuclear RNA Sequencing Reveals Activation of Neuroinflammation Within the Pre‐Bötzinger Complex Following Repeated Seizures

Epilepsy is one of the most common neurological diseases in the world. Treatment with anti‐epileptic drugs (AEDs) prevents recurrent seizures in ~70% of patients with epilepsy, but the remaining 30% of patients with refractory epilepsies continue to experience seizures. The consequences of repeated seizures include, but are not limited to, a high risk of post‐ictal cardiorespiratory failure and Sudden Unexpected Death in Epilepsy (SUDEP). Fundamental gaps exist in understanding how repeated seizures disrupt the vital cardiorespiratory control system in refractory epilepsy. A factor commonly identified in many neurological conditions is neuroinflammation, which may support beneficial health functions but is dysregulated in neurological disease. Key cells within the CNS that mediate beneficial and/or pathological neuroinflammation are resident microglia and astrocytes, which have been shown to be dysfunctional in human epilepsy and alter neuronal function. However, it is not known what mechanistic role they play in contributing to epilepsy‐related impairment in cardiorespiratory control or increased SUDEP risk. Here, we tested the hypothesis that repeated seizures lead to activation of neuroinflammation mediated by microglia and astrocytes in CNS regions of cardiorespiratory control, leading to a progressive decline in neurologic function. Preliminary data in our novel rat model with genetic mutations in Kcnj16, a gene encoding an inwardly‐rectifying potassium channel Kir5.1 in Dahl salt‐sensitive rat (SSkcnj16‐/‐) show that repeated sound‐induced seizures lead to a progressively more severe post‐ictal suppression of breathing frequency and heart rate. Single nuclear RNA sequencing of pre‐Bötzinger Complex/Nucleus Ambiguous cells (roughly 80,000) was performed from rats exposed to 0, 3, 7, or 10 seizures to measure cell type‐specific gene expression changes induced by seizures. Bioinformatic analyses of transcriptomic changes in microglia, neuronal, and glial cells within these regions point to activation of specific inflammatory pathways following repeated seizures such as IL‐1<img width=“7” height=“13” src=“file:////Users/wasifosmani/Library/Group%20Containers/UBF8T346G9.Office/TemporaryItems/msohtmlclip/clip_image002.png”= signaling and Toll‐like Receptor signaling. Afterwards, cytokine‐chemokine array was performed in brain regions regulating cardiorespiratory control after rats were exposed to 0, 3, 7, or 10 seizures and confirmed the presence of neuroinflammation after seizure induction. Identifying neuroinflammatory signals/pathways induced by repeated seizures within distinct neural circuits will enhance understanding of pathophysiological consequences of uncontrolled seizures in patients with refractory epilepsy and hold the potential for identifying new therapeutic targets aimed at improving cardiorespiratory function to reduce the risk of SUDEP.

SUDEP risk and autonomic dysfunction in genetic epilepsies

The underlying pathophysiology of sudden unexpected death in epilepsy (SUDEP) remains unclear. This phenomenon is likely multifactorial, and there is considerable evidence that genetic factors play a role. There are certain genetic causes of epilepsy in which the risk of SUDEP appears to be increased relative to epilepsy overall. For individuals with pathogenic variants in genes including SCN1A, SCN1B, SCN8A, SCN2A, GNB5, KCNA1 and DEPDC5, there are varying degrees of evidence to suggest an increased risk for sudden death. Why the risk for sudden death is higher is not completely clear; however, in many cases pathogenic variants in these genes are also associated with autonomic dysfunction, which is hypothesized as a contributing factor to SUDEP. We review the evidence for increased SUDEP risk for patients with epilepsy due to pathogenic variants in these genes, and also discuss what is known about autonomic dysfunction in these contexts.

Single Nuclear RNA Sequencing Reveals Activation of Neuroinflammation Within the Pre‐Bötzinger Complex Following Repeated Seizures

Epilepsy is one of the most common neurological diseases in the world. Treatment with anti-epileptic drugs (AEDs) prevents recurrent seizures in ~70% of patients with epilepsy, but the remaining 30% of patients with refractory epilepsies continue to experience seizures. The consequences of repeated seizures include but are not limited to memory impairments and a high risk of post-ictal cardiorespiratory failure, and Sudden Unexpected Death in Epilepsy (SUDEP). Fundamental gaps exist in understanding how repeated seizures disrupt the vital cardiorespiratory control system and neural networks facilitating memory formation in refractory epilepsy. A factor commonly identified in many neurological conditions is neuroinflammation, which may support beneficial health functions but is dysregulated in neurological disease. Key cells within the CNS that mediate beneficial and/or pathological neuroinflammation are resident microglia and astrocytes, which have been shown to be dysfunctional in human epilepsy and alter neuronal function. However, it is not known what mechanistic role they play in contributing to epilepsy-related memory impairment, impairment in cardiorespiratory control, or increased SUDEP risk. Here, we tested the hypothesis that repeated seizures lead to activation of neuroinflammation mediated by microglia and astrocytes in CNS regions of memory and ventilatory control, leading to a progressive decline in neurologic function. Preliminary data in our novel rat model with genetic mutations in Kcnj16, a gene encoding an inwardly-rectifying potassium channel Kir5.1 in Dahl salt-sensitive rat (SSkcnj16-/) show that repeated sound-induced seizures lead to a progressively more severe post-ictal suppression of breathing frequency and heart rate, and impaired memory. Single nuclear RNA sequencing of pre-Bötzinger Complex/nucleus ambiguous cells was performed from rats exposed to 0, 3, 7, or 10 seizures to measure cell type-specific gene expression changes induced by seizures. Bioinformatic analyses of transcriptomic changes in microglia, neuronal, and glial cells within these regions point to activation of specific inflammatory pathways following repeated seizures such as IL-1Beta signaling and Toll-like Receptor signaling. Identifying neuroinflammatory signals/pathways induced by repeated seizures within distinct neural circuits will enhance understanding of pathophysiological consequences of uncontrolled seizures in patients with refractory epilepsy and hold the potential for identifying new therapeutic targets aimed at improving memory and cardiorespiratory function to reduce the risk of SUDEP.

Kv1.1 subunits localize to cardiorespiratory brain networks in mice where their absence induces astrogliosis and microgliosis

Cardiorespiratory collapse following a seizure is a suspected cause of sudden unexpected death in epilepsy (SUDEP), the leading cause of epilepsy-related mortality. In the commonly used Kcna1 gene knockout (Kcna1−/−) mouse model of SUDEP, cardiorespiratory profiling reveals an array of aberrant breathing patterns that could contribute to risk of seizure-related mortality. However, the brain structures mediating these respiratory abnormalities remain unknown. We hypothesize that Kv1.1 deficiency in respiratory control centers of the brain contribute to respiratory dysfunction in Kcna1−/− mice leading to increased SUDEP risk. Thus, in this study, we first used immunohistochemistry to map expression of Kv1.1 protein in cardiorespiratory brain regions of wild-type Kcna1+/+ (WT) mice. Next, GFAP and Iba1 immunostaining was used to test for the presence of astrogliosis and microgliosis, respectively, in the cardiorespiratory centers of Kcna1−/− mice, which could be indicative of seizure-related brain injury that could impair breathing. In WT mice, we detected Kv1.1 protein in all cardiorespiratory centers examined, including the basolateral amygdala, dorsal respiratory group, dorsal motor nucleus of vagus, nucleus ambiguus, ventral respiratory column, and pontine respiratory group, as well as chemosensory centers including the retrotrapezoid and median raphae nuclei. Extensive gliosis was observed in the same areas in Kcna1−/− mice suggesting that seizure-associated brain injury could contribute to respiratory abnormalities.

Clinical risk factors in SUDEP: A nationwide population-based case-control study.

ObjectiveWe conducted a nationwide case-control study in Sweden to test the hypothesis that specific clinical characteristics are associated with increased risk of sudden unexpected death in epilepsy (SUDEP).MethodsThe study included 255 SUDEP cases (definite and probable) and 1,148 matched controls. Clinical information was obtained from medical records and the National Patient Register. The association between SUDEP and potential risk factors was assessed by odds ratios (ORs) and 95% confidence intervals (CIs) and interaction assessed by attributable proportion due to interaction (AP).ResultsExperiencing generalized tonic-clonic seizures (GTCS) during the preceding year was associated with a 27-fold increased risk (OR 26.81, 95% CI 14.86–48.38), whereas no excess risk was seen in those with exclusively non-GTCS seizures (OR 1.15, 95% CI 0.54–48.38). The presence of nocturnal GTCS during the last year of observation was associated with a 15-fold risk (OR 15.31, 95% CI 9.57–24.47). Living alone was associated with a 5-fold increased risk of SUDEP (OR 5.01, 95% CI 2.93–8.57) and interaction analysis showed that the combination of not sharing a bedroom and having GTCS conferred an OR of 67.10 (95% CI 29.66–151.88), with AP estimated at 0.69 (CI 0.53–0.85). Among comorbid diseases, a previous diagnosis of substance abuse or alcohol dependence was associated with excess risk of SUDEP.ConclusionsIndividuals with GTCS who sleep alone have a dramatically increased SUDEP risk. Our results indicate that 69% of SUDEP cases in patients who have GTCS and live alone could be prevented if the patients were not unattended at night or were free from GTCS.

The incidence of SUDEP: A nationwide population-based cohort study.

To identify all cases of sudden unexpected death in epilepsy (SUDEP) among people in Sweden during 1 year and to determine the SUDEP incidence in relation to age, sex, and psychiatric comorbidity. We included all individuals with a hospital-based ambulatory care or hospital discharge diagnosis of epilepsy in the Swedish National Patient Registry during 1998-2005 who were alive on January 1, 2008. Deaths during 2008 were identified by linkage to the National Cause of Death Registry. Death certificates, medical charts, and police and autopsy reports were extensively reviewed to identify SUDEP cases. Of 57,775 epilepsy patients alive on January 1, 2008, 1,890 died (3.3%) during 2008. Of these, 99 met the Annegers SUDEP criteria (49 definite, 19 probable, and 31 possible). SUDEP accounted for 5.2% of all deaths and 36% of deaths in the 0-15 years age group. The incidence of definite/probable SUDEP was 1.20/1,000 person-years, and higher in men (1.41) than in women (0.96). All SUDEP cases <16 years were in boys. SUDEP incidence at ages <16, 16-50, and >50 years was 1.11, 1.13, and 1.29, respectively, per 1,000 person-years. The incidence was 5-fold increased among female patients with psychiatric comorbidities compared to those without. Epilepsy was mentioned on the death certificate in only 62 of the 99 (63%) SUDEP cases. Methods relying on death certificates underestimate SUDEP incidence. SUDEP risk has been underestimated especially in boys and in older people regardless of sex. Patients with psychiatric comorbidities, women in particular, are at increased SUDEP risk.

SUDEP and other causes of mortality in childhood-onset epilepsy

BackgroundThere are few prospective studies on the causes of mortality in well-characterized cohorts with epilepsy and even fewer that have autopsy data that allow for reliable determination of SUDEP. We report causes of mortality and mortality rates in the Finnish cohort with childhood-onset epilepsy. MethodsA population-based cohort of 245 children with epilepsy in 1964 has been prospectively followed for almost 40years. Seizure outcomes and mortality were assessed. Autopsy data were available in 70% of the cases. Sudden unexpected death in epilepsy (SUDEP) rates were assessed, and SUDEP was confirmed by autopsy. ResultsDuring the follow-up, 60 subjects died. The major risk factor for mortality was lack of terminal remission (p<0.0001). Remote symptomatic etiology also increased the risk for death (p<0.0001) but did not remain significant on multivariate analysis after adjusting for effect of remission. Of the deaths, 33/60 (55%) were epilepsy-related including SUDEP in 23/60 (38%) using the Nashef criteria, status epilepticus in 4/60 (7%), and accidental drowning in 6/60 (10%). The nonepilepsy-related deaths occurred primarily in the remote symptomatic group and were often related to the underlying disorder or to medical comorbidities that developed after the onset of the epilepsy. Risk factors for SUDEP on multivariable analysis included lack of 5-year terminal remission and not having a localization-related epilepsy. In cryptogenic/idiopathic cases, SUDEP did not occur in childhood but begins only in adolescence. ConclusionChildhood-onset epilepsy is associated with a substantial risk of epilepsy-related mortality, primarily SUDEP. In otherwise neurologically normal individuals, the increased SUDEP risk begins in adolescence. The higher mortality rates reported in this cohort are related to duration of follow-up as most of the mortality occurs many years after the onset of the epilepsy.

Do antiepileptic drugs or generalized tonic–clonic seizure frequency increase SUDEP risk? A combined analysis

In an analysis of four case-control studies of sudden unexpected death in epilepsy (SUDEP), we found that yearly frequency of generalized tonic-clonic seizures (GTCS) and antiepileptic drug (AED) polytherapy were associated with an increased risk for SUDEP. The prior analysis, however, did not evaluate AEDs and GTCS frequency concurrently. We combined data from the three case-control studies with information on the frequency of GTCS and AED therapy, that is, carbamazepine, phenytoin, valproic acid, and other AED therapy. Number of AEDs was also considered. Lamotrigine and GTCS frequency were considered separately in two of the case-control studies. Logistic regression analysis was used to evaluate GTCS frequency, each of the AEDs, and number of AEDs. Adjusted analysis of the different AEDs accounted for study, age at death, gender, and GTCS frequency. In crude analysis, GTCS frequency, AED polytherapy, and number of AEDs were associated with an increased risk for SUDEP. Analysis of individual AEDs and of number of AEDs, adjusting for GTCS frequency, revealed no increased risk associated with AEDs as monotherapy, polytherapy, or total number. GTCS frequency remained strongly associated with an increased risk for SUDEP. Our findings-that none of the AEDs considered were associated with increased SUDEP risk as monotherapy or as polytherapy when GTCS frequency was taken into account-provide a consistent message that number of GTCS increases SUDEP risk and not AEDs. These results suggest that prevention of SUDEP must involve increased efforts to decrease GTCS frequency in order to avert the occurrence of this devastating epilepsy outcome.