Cardiorespiratory abnormalities during epileptic seizures

The latency to awake from induced-obstructive sleep apnea is reduced in rats with chronic epilepsy

OSA is known to increase the risk for SUDEP in persons with epilepsy, but the relationship between these two factors is not clear. Also, there is no study showing the acute responses to obstructive apnea in a chronic epilepsy model. Therefore, this study aimed to characterize cardiorespiratory responses to obstructive apnea and chemoreceptor stimulation in rats. In addition, we analyzed respiratory centers in the brain stem by immunohistochemistry. Epilepsy was induced with pilocarpine. About 30-60 days after the first spontaneous seizure, tracheal and thoracic balloons, and electrodes for recording the electroencephalogram, electromyogram, and electrocardiogram were implanted. Intermittent apneas were made by inflation of the tracheal balloon during wakefulness, NREM sleep, and REM sleep. During apnea, respiratory effort increased, and heart rate fell, especially with apneas made during wakefulness, both in control rats and rats with epilepsy. Latency to awake from apnea was longer with apneas made during REM than NREM, but rats with epilepsy awoke more rapidly than controls with apneas made during REM sleep. Rats with epilepsy also had less REM sleep. Cardiorespiratory responses to stimulation of carotid chemoreceptors with cyanide were similar in rats with epilepsy and controls. Immunohistochemical analysis of Phox2b, tryptophan hydroxylase, and NK1 in brain stem nuclei involved in breathing and sleep (retrotrapezoid nucleus, pre-Bötzinger complex, Bötzinger complex, and caudal raphe nuclei) revealed no differences between control rats and rats with epilepsy. In conclusion, our study showed that rats with epilepsy had a decrease in the latency to awaken from apneas during REM sleep, which may be related to neuroplasticity in some other brain regions related to respiratory control, awakening mechanisms, and autonomic modulation.

Biomarkers of seizure severity derived from wearable devices

Besides triggering alarms, wearable seizure detection devices record a variety of biosignals that represent biomarkers of seizure severity. There is a need for automated seizure characterization, to identify high-risk seizures. Wearable devices can automatically identify seizure types with the highest associated morbidity and mortality (generalized tonic-clonic seizures), quantify their duration and frequency, and provide data on postictal position and immobility, autonomic changes derived from electrocardiography/heart rate variability, electrodermal activity, respiration, and oxygen saturation. In this review, we summarize how these biosignals reflect seizure severity, and how they can be monitored in the ambulatory outpatient setting using wearable devices. Multimodal recording of these biosignals will provide valuable information for individual risk assessment, as well as insights into the mechanisms and prevention of sudden unexpected death in epilepsy.

Noninvasive detection of focal seizures in ambulatory patients

Reliably detecting focal seizures without secondary generalization during daily life activities, chronically, using convenient portable or wearable devices, would offer patients with active epilepsy a number of potential benefits, such as providing more reliable seizure count to optimize treatment and seizure forecasting, and triggering alarms to promote safeguarding interventions. However, no generic solution is currently available to reach these objectives. A number of biosignals are sensitive to specific forms of focal seizures, in particular heart rate and its variability for seizures affecting the neurovegetative system, and accelerometry for those responsible for prominent motor activity. However, most studies demonstrate high rates of false detection or poor sensitivity, with only a minority of patients benefiting from acceptable levels of accuracy. To tackle this challenging issue, several lines of technological progress are envisioned, including multimodal biosensing with cross‐modal analytics, a combination of embedded and distributed self‐aware machine learning, and ultra–low‐power design to enable appropriate autonomy of such sophisticated portable solutions.

Effects of enalapril and losartan alone and in combination with sodium valproate on seizures, memory, and cardiac changes in rats

PURPOSE

Cardiac changes accompanying seizures may be responsible for sudden unexpected death in epilepsy (SUDEP), and drugs with antiseizure and favorable cardiovascular profile could be beneficial. The effect of losartan and enalapril alone and in combination with sodium valproate on seizures, cognition, cardiac histopathology, and serum brain-derived neurotropic factor (BDNF) levels were determined.

METHODS

Male "Wistar" rats (200-250 g) were administered enalapril (20 mg/kg, intraperitoneally (i.p.)) and losartan (10 mg/kg, i.p.) daily and simultaneously subjected to pentylenetetrazole (PTZ)-kindling (PTZ 30 mg/kg, i.p., every alternate day). Enalapril and losartan were injected 45 & 120 min before seizure stimuli. In another set of experiments, sodium valproate (150 mg/kg, i.p.) alone or in combination with enalapril (20 mg/kg, i.p.) and losartan (10 mg/kg, i.p.) were administered daily during induction of kindling. The effect on seizures and behavior were noted; rats were sacrificed, and blood and hearts were collected for further analysis, i.e., BDNF levels, heart weight-body weight (HWBW) ratio, and cardiac histopathology.

RESULTS

Losartan, but not enalapril, suppressed the seizure score in PTZ kindling. Sodium valproate alone or in combination with losartan or enalapril prevented kindled seizures. Sodium valproate per se caused cognitive impairment, which was prevented on combining with losartan or enalapril. A decrease in HWBW ratio was observed only in enalapril group (p value = 0.02). Kindling led to cardiac ischemic changes, which could be prevented by losartan and sodium valproate. Serum BDNF level was decreased in PTZ (p value = 0.02) and sodium valproate per se group (p value = 0.04), but sodium valproate could reverse the PTZ-induced decrease in serum BDNF level.

CONCLUSION

The use of losartan with sodium valproate in epilepsy may prevent the cognitive and cardiac sequelae of seizures. The BDNF levels as a marker for cardiovascular risk in persons with epilepsy (PWE) needs to be explored further.

Causes of mortality in individuals with tuberous sclerosis complex

AIM

The causes of death in patients with tuberous sclerosis complex (TSC) have rarely been studied, with only one published account, which was reported from the Mayo Clinic in 1991. We aimed to investigate mortality in a large cohort of patients with TSC from one of two national referral clinics in the UK.

METHOD

We identified 284 patients who attended Bath TSC clinic between 1981 and 2015, and ascertained causes of death by reviewing medical records, death certificates, and postmortem reports.

RESULTS

Sixteen patients died from complications of TSC: eight from TSC kidney diseases; four from sudden unexpected death in epilepsy (SUDEP); two from lymphangioleiomyomatosis; one from a subependymal giant cell astrocytoma; and one from a pancreatic malignancy. The median age of death was 33 years (interquartile range [IQR] 26-46). Mortality was significantly more common in patients with learning disabilities than in those without (13/135 [9%] vs 3/131 [2%]; two-tailed Fisher exact test p=0.020).

INTERPRETATION

Renal disease is a major cause of mortality in TSC. Lifelong surveillance and early intervention is warranted. SUDEP is also an important cause of mortality. Patients with learning disabilities are at significantly greater risk of early mortality and this implies the need for greater vigilance for TSC-related complications in this group. Female patients are vulnerable to pulmonary and renal disease. Pancreatic lesions are a rare but potentially treatable cause of mortality.

Pediatric Sudden Unexpected Death in Epilepsy

BACKGROUND

Epilepsy is a common neurological disorder among children and adolescents that is associated with increased mortality for numerous reasons. Sudden unexpected death in epilepsy is a critically important entity for physicians who treat patients with epilepsy. Many pediatric neurologists are hesitant to discuss this condition with patients and families because of the lower risk in the pediatric age group.

METHODS

We searched for studies published between January 2000 and June 2015 by means of a PubMed search and a cumulative review of reference lists of all relevant publications, using the keywords "sudden unexpected death in epilepsy patients," "pediatric SUDEP," "sudden unexpected death in epilepsy patients and children," "sudden unexpected death in children" and "sudden infant death syndrome."

RESULTS

SUDEP is a rare condition in children. Its mechanism is poorly understood and may have a distinct pathogenesis from adult sudden unexpected death in epilepsy. Limited comfort, experience, and knowledge to provide appropriate education about sudden unexpected death in epilepsy leads to fewer physicians discussing this subject leading to less informed and less prepared patients and families.

CONCLUSION

We provide a detailed review of the literature on pediatric SUDEP, including the definition, classification, and proposed mechanisms of sudden unexpected death in epilepsy in children, as well as discuss the incidence in the pediatric population and risk factors in children, concluding with possible prevention strategies.

Decreased heart rate and enhanced sinus arrhythmia during interictal sleep demonstrate autonomic imbalance in generalized epilepsy

We hypothesized that epilepsy affects the activity of the autonomic nervous system even in the absence of seizures, which should manifest as differences in heart rate variability (HRV) and cardiac cycle. To test this hypothesis, we investigated ECG traces of 91 children and adolescents with generalized epilepsy and 25 neurologically normal controls during 30 min of stage 2 sleep with interictal or normal EEG. Mean heart rate (HR) and high-frequency HRV corresponding to respiratory sinus arrhythmia (RSA) were quantified and compared. Blood pressure (BP) measurements from physical exams of all subjects were also collected and analyzed. RSA was on average significantly stronger in patients with epilepsy, whereas their mean HR was significantly lower after adjusting for age, body mass index, and sex, consistent with increased parasympathetic tone in these patients. In contrast, diastolic (and systolic) BP at rest was not significantly different, indicating that the sympathetic tone is similar. Remarkably, five additional subjects, initially diagnosed as neurologically normal but with enhanced RSA and lower HR, eventually developed epilepsy, suggesting that increased parasympathetic tone precedes the onset of epilepsy in children. ECG waveforms in epilepsy also displayed significantly longer TP intervals (ventricular diastole) relative to the RR interval. The relative TP interval correlated positively with RSA and negatively with HR, suggesting that these parameters are linked through a common mechanism, which we discuss. Altogether, our results provide evidence for imbalanced autonomic function in generalized epilepsy, which may be a key contributing factor to sudden unexpected death in epilepsy.

Sleep and Epilepsy

Sleep and epilepsy are common bedfellows. Sleep can affect frequency and occurrence of interictal spikes and occurrence, timing, and threshold of seizure. Epilepsy can worsen sleep architecture and severity of sleep disorders. Thus, a vicious cycle is set. Certain epilepsy syndromes are so intertwined with sleep that they are considered sleep-related epilepsies. Poor sleep in epilepsy is multifactorial and is worsened by poorly controlled seizures. On the contrary, poor sleep is associated with worsened quality of life, psychological function, and memory. Improving sleep has been noted to improve seizure frequency and an overall well-being in patients with epilepsy. Hence, an emphasis should be given to address sleep in patients with epilepsy. These interactions are discussed in detail in this review.