Exome analysis focusing on epilepsy-related genes in children and adults with sudden unexplained death

PURPOSE

Genetic studies in sudden infant death syndrome (SIDS) and sudden unexplained death (SUD) cohorts have indicated that cardiovascular diseases might have contributed to sudden unexpected death in 20-35 % of autopsy-negative cases. Sudden unexpected death can also occur in people with epilepsy, termed as sudden unexpected death in epilepsy (SUDEP). The pathophysiological mechanisms of SUDEP are not well understood, but are likely multifactorial, including seizure-induced hypoventilation and arrhythmias as well as genetic risk factors. The sudden death of some of the SIDS/SUD victims might also be explained by genetic epilepsy, therefore this study aimed to expand the post-mortem genetic analysis of SIDS/SUD cases to epilepsy-related genes.

METHODS

Existing whole-exome sequencing data from our 155 SIDS and 45 SUD cases were analyzed, with a focus on 365 epilepsy-related genes. Nine of the SUD victims had a known medical history of epilepsy, seizures or other underlying neurological conditions and were therefore classified as SUDEP cases.

RESULTS

In our SIDS and SUD cohorts, we found epilepsy-related pathogenic/likely pathogenic variants in the genes OPA1, RAI1, SCN3A, SCN5A and TSC2.

CONCLUSION

Post-mortem analysis of epilepsy-related genes identified potentially disease-causing variants that might have contributed to the sudden death events in our SIDS/SUD cases. However, the interpretation of identified variants remains challenging and often changes over time as more data is gathered. Overall, this study contributes insight in potentially pathophysiological epilepsy-related mechanisms in SIDS, SUD and SUDEP victims and underlines the importance of sensible counselling on the risk and preventive measures in genetic epilepsy.

Distinction between epileptic and non-epileptic arousal by heart rate change

OBJECTIVE

We investigated the difference in heart rate (HR) change between epileptic and non-epileptic arousals in adult patients with epilepsy (PWE).

METHODS

This is a case-control study conducted at the University Hospitals of Cleveland Medical Center. Inclusion criteria are (1) adult (≥18 years old) PWE who had arousal related to a focal aware or impaired awareness automatism seizure with or without focal to bilateral tonic-clonic seizure during an Epilepsy Monitoring Unit (EMU) admission between January 2009 and January 2021 or (2) adult PWE who had a non-epileptic arousal during an EMU admission between July 2020 and January 2021. Outcomes are (1) a percent change in baseline HR within 60 s after arousal and (2) the highest percent change in baseline HR within a 10-s sliding time window within 60 s after arousal.

RESULTS

We included 20 non-epileptic arousals from 20 adult PWE and 29 epileptic arousals with seizures from 29 adult PWE. Within 60 s after arousal, HR increased by a median of 86.7% (interquartile range (IQR), 52.7%-121.3%) in the epileptic arousal group compared to a median of 26.1% (12.9%-43.3%) in the non-epileptic arousal group (p < 0.001). The cut-off value was 48.7%. The area under the curve (AUC), sensitivity, and specificity were 0.85, 0.79, and 0.80, respectively. More than 70.1% was only in the epileptic arousals, with 100% specificity. Within 10 s of the greatest change, HR increased by 36.5 (18.7%-48.4%) in the epileptic arousal group compared to 17.7 (10.9%-23.7%) in the non-epileptic arousal group (p < 0.001). The cut-off value was 36.5%. The AUC, sensitivity, and specificity were 0.79, 0.52, and 0.95, respectively. More than 48.1% was only in the epileptic arousals, with 100% specificity.

SIGNIFICANCE

Tachycardia during epileptic arousals was significantly higher and more robust compared to tachycardia during non-epileptic arousals.

Nocturnal seizure detection: What are the needs and expectations of adults with epilepsy receiving secondary care?

INTRODUCTION

Seizure detection devices (SDDs) may lower the risk of sudden unexpected death in epilepsy (SUDEP) and provide reassurance to people with epilepsy and their relatives. We aimed to explore the perspectives of those receiving secondary care on nocturnal SDDs and epilepsy in general.

MATERIALS AND METHODS

We recruited adults with tonic or tonic-clonic seizures who had at least one nocturnal seizure in the preceding year. We used semi-structured interviews and questionnaires to explore their views on SDDs and their experiences of living with epilepsy. None of the participants had any previous experience with SDDs. We analyzed the data using qualitative content analysis.

RESULTS

Eleven participants were included with a nocturnal seizure frequency ranging from once every few weeks to less than once a year. Some participants experienced little burden of disease, whereas others were extremely impaired. Opinions on the perceived benefit of seizure detection varied widely and did not always match the clinical profile. Some participants with high SUDEP risk displayed no interest at all, whereas others with a low risk for unattended seizures displayed a strong interest. Reasons for wanting to use SDDs included providing reassurance, SUDEP prevention, and improving night rest. Reasons for not wanting to use SDDs included not being able to afford it, having to deal with false alarms, not having anyone to act upon the alarms, having a relative that will notice any seizures, not feeling like the epilepsy is severe enough to warrant SDD usage or not trusting the device.

CONCLUSIONS

The interest in nocturnal seizure detection varies among participants with low seizure frequencies and does not always match the added value one would expect based on the clinical profile. Further developments should account for the heterogeneity in user groups.

Prolonged Video-EEG and Heart Rate Variability can Elucidate Autonomic Dysregulation in Infantile Apneic Seizures

BACKGROUND

Infantile apneic seizures (IASs) are unexpected life-threatening events. We aimed to determine the utility of prolonged video-electroencephalography (vEEG) and heart rate variability (HRV) in IAS.

METHODS

The study included seven infants with apneic seizures captured by vEEG, percutaneous oxygen saturation (SpO₂), and electrocardiography (ECG). Interictal, preictal, and postictal HRV of patients and N2 sleep HRV of 10 age-matched controls were determined.

RESULTS

We analyzed seven vEEGs (duration = 17 to 87 hours) of seven patients aged three to 13 months (mean onset age of apneic event = 6.3 months). Fifteen apneic seizures (one to five per infant) were captured. The initial apneic seizure was captured at 7.5 to 76 hours (mean = 36.6 hours) after vEEG initiation. Ictal rhythmic delta/theta/fast waves were seen over temporal (five patients), central (one), and diffuse areas (one). Ictal SpO₂ decreased between 1.5% and 90% (mean = 47.9%). Ictal decreased heart rate (HR) (six seizures) and ictal increased HR (14) was detected. Both decreased and increased HR was observed (five). The preictal low-frequency (LF)/high-frequency (HF) ratio was significantly higher than the interictal LF/HF ratio (P = 0.048). Preictal (P = 0.048), and postictal (P = 0.019) root mean square of successive differences (RMSSDs) of patients were lower than the sleep RMSSD of controls. These results indicated dominant sympathetic activity. RMSSD from interictal to preictal periods tended to be higher in IAS with decreased HR than in IAS with increased HR alone (P = 0.066). The postictal RMSSD showed tendency to be higher in IAS with decreased HR than in IAS with increased HR alone (P = 0.088). The decreased HR and increased RMSSD suggested not only sympathetic activity but also escalated parasympathetic activity in IAS.

CONCLUSIONS

Infants with unexpected apneic events should be monitored with prolonged vEEG, SpO₂, and ECG. Abnormal HRV in infants with apneic seizures might indicate additional autonomic dysregulation in IAS.

Parental experiences and perspectives on the value of seizure detection while caring for a child with epilepsy: A qualitative study

INTRODUCTION

Caring for a child with epilepsy has a significant impact on parental quality of life. Seizure unpredictability and complications, including sudden unexpected death in epilepsy (SUDEP), may cause high parental stress and increased anxiety. Nocturnal supervision with seizure detection devices may lower SUDEP risk and decrease parental burden of seizure monitoring, but little is known about their added value in family homes.

METHODS

We conducted semi-structured in-depth interviews with parents of children with refractory epilepsy participating in the PROMISE trial (NCT03909984) to explore the value of seizure detection in the daily care of their child. Children were aged 4-16 years, treated at a tertiary epilepsy center, had at least one nocturnal major motor seizure per week, and used a wearable seizure detection device (NightWatch) for two months at home. Data were analyzed using inductive thematic analysis.

RESULTS

Twenty three parents of nineteen children with refractory epilepsy were interviewed. All parents expressed their fear of missing a large seizure and the possible consequences of not intervening in time. Some parents felt the threat of child loss during every seizure, while others thought about it from time to time. The fear could fluctuate over time, mainly associated with fluctuations of seizure frequency. Most parents described how they developed a protective behavior, driven by this fear. The way parents handled the care of their child and experienced the burden of care influenced their perceptions on the added value of NightWatch. The experienced value of NightWatch depended on the amount of assurance it could offer to reduce their fear and the associated protective behavior as well as their resilience to handle the potential extra burden of care, due to false alarms or technical problems.

CONCLUSION

Healthcare professionals and device companies should be aware of parental protective behavior and the high parental burden of care and develop tailored strategies to optimize seizure detection device care.

Mortality in tuberous sclerosis complex

We studied mortality in tuberous sclerosis complex (TSC) by analyzing data from the Tuberous Sclerosis Alliance Natural History Database of 2233 patients from 18 United States TSC centers. Among 31 decedents with data; mean age of death was 29 years. Cause of death could be determined in 26 cases: 11 definitely related to TSC, 14 possibly related to TSC, and 1 unrelated to TSC. Causes of death included SUDEP in 11 (35.5%; Definite (5), Probable (4), Possible (2)), respiratory conditions in 6 (23.1%; lymphangiomyelomatosis in one), tumors in 3 (11.5%), suicide in 2 (7.7%), cardiopulmonary in 2 (7.7%), shunt malfunction in one, and drowning in one. For SUDEP cases, mean age of epilepsy onset was 7 months and 10/11 were treated with multiple anti-seizure medications (ASMs) at death; 7 had intractable epilepsy and 3 were controlled with ASMs. Patients with TSC and their families should be counseled about ASM adherence and lifestyle factors, and the potential role of nocturnal supervision or seizure detection devices to prevent SUDEP.

SCN8A-related developmental and epileptic encephalopathy with ictal asystole requiring cardiac pacemaker implantation

INTRODUCTION

SCN8A-related epilepsy has various phenotypes. In particular, patients with developmental and epileptic encephalopathy (DEE) are resistant to antiepileptic drugs and may present with autonomic symptoms, such as marked bradycardia and apnea during seizures, and thus have an increased risk of sudden death. Herein, we report a case of very severe SCN8A-related epilepsy necessitating cardiac pacemaker implantation because of repetitive ictal asystole.

CASE REPORT

The patient was a 14-month-old girl. Tremor and generalized tonic seizure occurred after birth. During seizures, bradycardia and perioral cyanosis occurred, and then, after developing tachycardia and apnea, marked bradycardia and generalized cyanosis occurred, which sometimes resulted in ictal asystole requiring cardiopulmonary resuscitation. Her seizures were refractory to antiepileptic drugs. As the seizures requiring resuscitation did not decrease, cardiac pacemaker implantation was performed four months after birth. Exome sequencing revealed a heterozygous de novo variant in SCN8A (NM_014191.3:c.4934T>C,p.(Met1645Thr)). Even though phenytoin was effective, seizures with bradycardia remained approximately once a month, and pacemaker activity was observed.

CONCLUSIONS

This is, to our knowledge, the first reported case of SCN8A-related DEE in whom pacemaker implantation was performed. Pacemaker implantation should be considered as a treatment option for critical patients with SCN8A-related DEE as in the present case, because the incidence of sudden unexpected death in epilepsy is reported to be approximately 10% in patients with SCN8A-related DEE.

Near-sudden unexpected death in a patient with epilepsy undergoing hemodialysis: a case report

Sudden unexpected death in epilepsy (SUDEP) has been defined as a sudden/unexpected, witnessed/unwitnessed, nontraumatic, and nondrowning death in epileptic patients with/without seizure evidence and documented status epilepticus. Identified as the leading cause of epilepsy-related deaths, SUDEP cases are highly unrecognized and underreported due to diagnostic difficulty. We report a case of a successfully revived hemodialysis patient who developed cardiopulmonary arrest after a witnessed convulsive seizure. Electroencephalogram revealed epileptic abnormalities. Therefore, this case could be seizure-induced cardiopulmonary arrest and near-SUDEP. Hence, the possibility of SUDEP should be considered even in hemodialysis patients having conventional coronary risk factors for sudden cardiac death.

Can We Prevent Sudden Unexpected Death in Epilepsy (SUDEP)?

Sudden unexpected death in epilepsy (SUDEP) remains an important cause of epilepsy-related mortality, especially in patients with refractory epilepsy. The exact cause is not known, but postictal cardiac, respiratory, and brainstem dysfunctions are implicated. SUDEP prevention remains a big challenge. Except for low-quality evidence of preventive effect of nocturnal supervision for SUDEP, no other evidence-based preventive modality is available. Other potential preventive strategies for SUDEP include reducing the occurrence of generalized tonic-clonic seizures using seizure detection devices, detecting cardiorespiratory distress through respiratory and heart rate monitoring devices, preventing airway obstruction (safety pillows), and reducing central hypoventilation using selective serotonin reuptake inhibitors and adenosine and opiate antagonists. However, none of the above-mentioned modalities has been proven to prevent SUDEP. The present review intends to provide insight into the available SUDEP prevention modalities.

Neuron-specific Kv1.1 deficiency is sufficient to cause epilepsy, premature death, and cardiorespiratory dysregulation

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of epilepsy-related mortality, but the precise cellular substrates involved remain elusive. Epilepsy-associated ion channel genes with co-expression in brain and heart have been proposed as SUDEP candidate genes since they provide a singular unifying link between seizures and lethal cardiac arrhythmias. Here, we generated a conditional knockout (cKO) mouse with neuron-specific deletion of Kcna1, a SUDEP-associated gene with brain-heart co-expression, to test whether seizure-evoked cardiac arrhythmias and SUDEP require the absence of Kv1.1 in both brain and heart or whether ablation in neurons is sufficient. To obtain cKO mice, we developed a floxed Kcna1 mouse which we crossed to mice with the Synapsin1-Cre transgene, which selectively deletes Kcna1 in most neurons. Molecular analyses confirmed neuron-specific Kcna1 deletion in cKO mice and corresponding loss of Kv1.1 except in cerebellum where Synapsin1-Cre is not highly expressed. Survival studies and electroencephalography, electrocardiography, and plethysmography recordings showed that cKO mice exhibit premature death, epilepsy, and cardiorespiratory dysregulation but to a lesser degree than global knockouts. Heart rate variability (HRV) was increased in cKO mice with peaks during daytime suggesting disturbed diurnal HRV patterns as a SUDEP biomarker. Residual Kv1.1 expression in cKO cerebellum suggests it may play an unexpected role in regulating ictal cardiorespiratory dysfunction and SUDEP risk. This work demonstrates the principle that channelopathies with brain-heart expression patterns can increase death risk by brain-driven mechanisms alone without a functionally compromised heart, reinforcing seizure control as a primary clinical strategy for SUDEP prevention.

Cardiorespiratory profiling reveals primary breathing dysfunction in Kcna1-null mice: Implications for sudden unexpected death in epilepsy

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of epilepsy-related mortality, but the relative importance of underlying cardiac and respiratory mechanisms remains unclear. To illuminate the interactions between seizures, respiration, cardiac function, and sleep that contribute to SUDEP risk, here we developed a mouse epilepsy monitoring unit (EMU) to simultaneously record video, electroencephalography (EEG), electromyography (EMG), plethysmography, and electrocardiography (ECG) in a commonly used genetic model of SUDEP, the Kcna1 knockout (Kcna1^-/-) mouse. During interictal periods, Kcna1^-/- mice exhibited an abnormal absence of post-sigh apneas and a 3-fold increase in respiratory variability. During spontaneous convulsive seizures, Kcna1^-/- mice displayed an array of aberrant breathing patterns that always preceded cardiac abnormalities. These findings support respiratory dysfunction as a primary risk factor for susceptibility to deleterious cardiorespiratory sequelae in epilepsy and reveal a new role for Kcna1-encoded Kv1.1 channels in the regulation of basal respiratory physiology.

Prone sleeping and SUDEP risk: The dynamics of body positions in nonfatal convulsive seizures

BACKGROUND

Most victims of sudden unexpected death in epilepsy (SUDEP) are found prone with signs suggestive of an unwitnessed convulsive seizure (CS). Prone sleeping has been proposed as a risk factor for SUDEP. Little is known, however, about the change of body position during the course of CSs.

METHODS

We retrospectively reviewed video-EEG data and assessed body positions during the course of CSs, until there was a physical interaction by nursing staff with the subject.

RESULTS

We identified 180 CSs in 90 individuals. In 16 of the 180 CSs (9%), the subject started in or turned to the prone position. Of the seven CSs that started in the prone position, three turned to a lateral position during the CS. In 13 CSs, the subject was in prone position at time of nursing intervention; nine (69%) of these started in a nonprone position.

DISCUSSION

Our data suggest that the prone position occurs infrequently in closely supervised nonfatal CSs, a notable contrast to the number of victims of SUDEP found prone. Whether prone sleeping prior to CSs increases SUDEP risk, however, remains speculative, as body position during the course of a CS appeared to be dynamic.

Nonseizure SUDEP: Sudden unexpected death in epilepsy without preceding epileptic seizures

OBJECTIVE

To describe the phenomenology of monitored sudden unexpected death in epilepsy (SUDEP) occurring in the interictal period where death occurs without a seizure preceding it.

METHODS

We report a case series of monitored definite and probable SUDEP where no electroclinical evidence of underlying seizures was found preceding death.

RESULTS

Three patients (two definite and one probable) had SUDEP. They had a typical high SUDEP risk profile with longstanding intractable epilepsy and frequent generalized tonic-clonic seizures (GTCS). All patients had varying patterns of respiratory and bradyarrhythmic cardiac dysfunction with profound electroencephalography (EEG) suppression. In two patients, patterns of cardiorespiratory failure were similar to those seen in some patients in the Mortality in Epilepsy Monitoring Units Study (MORTEMUS).

SIGNIFICANCE

SUDEP almost always occur postictally, after GTCS and less commonly after a partial seizure. Monitored SUDEP or near-SUDEP cases without a seizure have not yet been reported in literature. When nonmonitored SUDEP occurs in an ambulatory setting without an overt seizure, the absence of EEG information prevents the exclusion of a subtle seizure. These cases confirm the existence of nonseizure SUDEP; such deaths may not be prevented by seizure detection-based devices. SUDEP risk in patients with epilepsy may constitute a spectrum of susceptibility wherein some are relatively immune, death occurs in others with frequent GTCS with one episode of seizure ultimately proving fatal, while in others still, death may occur even in the absence of a seizure. We emphasize the heterogeneity of SUDEP phenomena.

Optogenetic stimulation of cholinergic brainstem neurons during focal limbic seizures: Effects on cortical physiology

Focal temporal lobe seizures often cause impaired cortical function and loss of consciousness. Recent work suggests that the mechanism for depressed cortical function during focal seizures may depend on decreased subcortical cholinergic arousal, which leads to a sleep-like state of cortical slow-wave activity. To test this hypothesis, we sought to directly activate subcortical cholinergic neurons during focal limbic seizures to determine the effects on cortical function. Here we used an optogenetic approach to selectively stimulate cholinergic brainstem neurons in the pedunculopontine tegmental nucleus during focal limbic seizures induced in a lightly anesthetized rat model. We found an increase in cortical gamma activity and a decrease in delta activity in response to cholinergic stimulation. These findings support the mechanistic role of reduced subcortical cholinergic arousal in causing cortical dysfunction during seizures. Through further work, electrical or optogenetic stimulation of subcortical arousal networks may ultimately lead to new treatments aimed at preventing cortical dysfunction during seizures.

A resting-state functional connectivity study in patients at high risk for sudden unexpected death in epilepsy

OBJECTIVE

Seizure-related respiratory and cardiac dysfunctions were once thought to be the direct cause of sudden unexpected death in epilepsy (SUDEP), but both may be secondary to postictal cerebral inhibition. An important issue that has not been explored to date is the neural network basis of cerebral inhibition. Our aim was to investigate the features of neural networks in patients at high risk for SUDEP using a blood oxygen level-dependent (BOLD) resting-state functional connectivity (FC) approach.

SUBJECTS AND METHODS

Resting-state functional magnetic resonance imaging (Rs-fMRI) data were recorded from 13 patients at high risk for SUDEP and 12 patients at low risk for SUDEP. Thirteen cerebral regions that are closely related to cardiorespiratory activity were selected as regions of interest (ROIs). The ROI-wise resting-state FC analysis was compared between the two groups.

RESULTS

Compared with patients at low risk for SUDEP, patients at high risk exhibited significant reductions in the resting-state FC between the pons and the right thalamus, the midbrain and the right thalamus, the bilateral anterior cingulate cortex (ACC) and the right thalamus, and the left thalamus and the right thalamus.

CONCLUSIONS

This investigation is the first to use neuroimaging methods in research on the mechanism of SUDEP and demonstrates the abnormally decreased resting-state FC in the ACC-thalamus-brainstem circuit in patients at high risk for SUDEP. These findings highlight the need to understand the fundamental neural network dysfunction in SUDEP, which may fill the missing link between seizure-related cardiorespiratory dysfunction and SUDEP, and provide a promising neuroimaging biomarker for risk prediction of SUDEP.

Ictal ontogeny in Dravet syndrome

OBJECTIVE

To define seizure characteristics of Dravet syndrome (DS) with video-electroencephalographic (EEG) recording in different age groups.

METHODS

We reviewed 23 patients with 63 seizures in different age groups: group 1 (0-5years old); group 2 (6-10years old); and group 3 (11 or above).

RESULTS

We included 7, 11 and 5 patients in groups 1, 2, and 3 respectively. Younger children had seizures while awake (p=0.005), provoked seizures (p=0.05), focal seizure semiology (p=0.02) and long seizure duration (p=0.0004). Older children had seizures from sleep (p=0.004), generalized seizure semiology (p=0.01) and short seizure duration (p=0.0007). A generalized ictal discharge was the most commonly observed EEG pattern (15/23, 65%), more frequently found in older children (p=0.01). Ten patients (43%) had unclassified seizures or seizures with discordant EEG results. Postictal EEG suppression was found in 9 (39%).

CONCLUSION

The phenotype of seizures and ictal EEG patterns in DS vary with age.

SIGNIFICANCE

These findings will enhance the recognition of DS in the adolescent population. The incidence of postictal EEG suppression seen in DS is significant because it is a possible biomarker for sudden unexpected death in epilepsy.