Heart rate variability in patients with epilepsy

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.

Impaired post-sleep apnea autonomic arousals in patients with drug-resistant epilepsy

OBJECTIVE

Sudden and unexpected deaths in epilepsy (SUDEP) pathophysiology may involve an interaction between respiratory dysfunction and sleep/wake state regulation. We investigated whether patients with epilepsy exhibit impaired sleep apnea-related arousals.

METHODS

Patients with drug-resistant (N = 20) or drug-sensitive (N = 20) epilepsy and obstructive sleep apnea, as well as patients with sleep apnea but without epilepsy (controls, N = 20) were included. We explored (1) the respiratory arousal threshold based on nadir oxygen saturation, apnea-hypopnea index, and fraction of hypopnea among respiratory events; (2) the cardiac autonomic response to apnea/hypopnea quantified as percentages of changes from the baseline in RR intervals (RRI), high (HF) and low (LF) frequency powers, and LF/HF.

RESULTS

The respiratory arousal threshold did not differ between groups. At arousal onset, RRI decreased (-9.42%) and LF power (179%) and LF/HF ratio (190%) increased. This was followed by an increase in HF power (118%), p < 0.05. The RRI decrease was lower in drug-resistant (-7.40%) than in drug-sensitive patients (-9.94%) and controls (-10.91%), p < 0.05. LF and HF power increases were higher in drug-resistant (188%/126%) than in drug-sensitive patients (172%/126%) and controls (177%/115%), p < 0.05.

CONCLUSIONS

Cardiac reactivity following sleep apnea is impaired in drug-resistant epilepsy.

SIGNIFICANCE

This autonomic dysfunction might contribute to SUDEP pathophysiology.

The effect of epilepsy and antiseizure medications on cardiac autonomic functions in children with epilepsy

BACKGROUND

Autonomic manifestations have been frequently studied in adults with epilepsy. Here, we evaluated cardiac autonomic (ANS) functions in children with epilepsy in the interictal period and determined the risks for their dysfunctions.

RESEARCH DESIGN AND METHODS

This study included 60 patients (boys = 25; girls = 35 age: 14.53 ± 2.54 yrs) and 25 controls. Patients were well-controlled on antiseizure medications (ASMs). The battery of testing included measuring resting heart rate (HR) and blood pressure (BP), 30:15 ratio, HR variability (HRV) response to deep breathing, Valsalva ratio and BP changes in response to standing, isometric exercise and cold.

RESULTS

Dizziness was reported in 25%. Autonomic dysfunctions were found in 45% (n = 27). Manifestations included high frequencies of abnormal 30:15 ratio (22%), HRV responses to deep breathing (45%), Valsalava ratio (45%), and BP responses to standing (35%), isometric exercise (27%) and cold (27%), indicating parasympathetic and sympathetic hypofunctions. There were positive correlations between parasympathetic and sympathetic dysfunctions. Logistic analysis showed that the durations of epilepsy and ASMs therapy were associated with ANS dysfunctions [95% CI: 0.895-4.719, p = 0.004].

CONCLUSIONS

Parasympathetic and sympathetic autonomic hypofunctions are common in children with epilepsy. This could be due to the depressant effect of sodium channel blocker ASMs on central and/or cardiac autonomic systems.

Heart Rate Variability as a Tool for Seizure Prediction: A Scoping Review

The most critical burden for People with Epilepsy (PwE) is represented by seizures, the unpredictability of which severely impacts quality of life. The design of real-time warning systems that can detect or even predict ictal events would enhance seizure management, leading to high benefits for PwE and their caregivers. In the past, various research works highlighted that seizure onset is anticipated by significant changes in autonomic cardiac control, which can be assessed through heart rate variability (HRV). This manuscript conducted a scoping review of the literature analyzing HRV-based methods for detecting or predicting ictal events. An initial search on the PubMed database returned 402 papers, 72 of which met the inclusion criteria and were included in the review. These results suggest that seizure detection is more accurate in neonatal and pediatric patients due to more significant autonomic modifications during the ictal transitions. In addition, conventional metrics are often incapable of capturing cardiac autonomic variations and should be replaced with more advanced methodologies, considering non-linear HRV features and machine learning tools for processing them. Finally, studies investigating wearable systems for heart monitoring denoted how HRV constitutes an efficient biomarker for seizure detection in patients presenting significant alterations in autonomic cardiac control during ictal events.

The Association of Nocturnal Seizures and Interictal Cardiac/Central Autonomic Function in Frontal Lobe Epilepsy: Heart Rate Variability and Central Autonomic Network Analysis

Purpose

Patients with epilepsy frequently experience autonomic dysfunction, closely related to sudden unexplained death in epilepsy (SUDEP). SUDEP occurs most often at night or during sleep, and frequent nocturnal seizures are an established risk factor. This study investigated the influence of nocturnal seizures on autonomic dysfunction in epilepsy.

Patients and Methods

This retrospective study enrolled frontal lobe epilepsy (FLE) patients who performed 24-hour EEG monitoring. All participants were divided into nocturnal FLE (NFLE, > 90% of seizures occurring during sleep) or diurnal FLE (DFLE) groups. EEG and ECG signals were simultaneously obtained during waking and sleep stages. EEG current density source and connectivity analysis of the autonomic network were performed. ECG was analyzed across time and frequency domains heart rate variability (HRV) analysis method was used. The obtained parameters were compared between the NFLE and DFLE groups.

Results

Fifteen NFLE and 16 DFLE patients were enrolled with no significant difference in age, sex, disease duration, seizure frequency, or the number of anti-seizure medications between the two groups. During sleep, a decrease in HRV parameters and an increase of the beta-1 (13-22 Hz) current source density power in the bilateral paracentral lobule (BA4,5,6), precuneus (BA7), and cingulate (BA31) were observed in the NFLE group compared to DFLE group. The NFLE group also showed hyperconnectivity in the central autonomic (12 edges distributed over 10 nodes), sympathetic (2 edges distributed over 3 nodes), and parasympathetic (4 edges distributed over 6 nodes) beta-1 frequency band networks during sleep. During wakefulness, central and cardiac autonomic variables were not significantly different between the NFLE and DFLE groups.

Conclusion

Interictal cardiac and central autonomic dysfunction occurred simultaneously and can be attributed to the brain-heart autonomic axis. Our findings suggest that nocturnal seizures may contribute to interictal autonomic dysfunction during sleep in people with epilepsy.

Exploring Autonomic Alterations during Seizures in Temporal Lobe Epilepsy: Insights from a Heart-Rate Variability Analysis

Epilepsy's impact on cardiovascular function and autonomic regulation, including heart-rate variability, is complex and may contribute to sudden unexpected death in epilepsy (SUDEP). Lateralization of autonomic control in the brain remains the subject of debate; nevertheless, ultra-short-term heart-rate variability (HRV) analysis is a useful tool for understanding the pathophysiology of autonomic dysfunction in epilepsy patients. A retrospective study reviewed medical records of patients with temporal lobe epilepsy who underwent presurgical evaluations. Data from 75 patients were analyzed and HRV indices were extracted from electrocardiogram recordings of preictal, ictal, and postictal intervals. Various HRV indices were calculated, including time domain, frequency domain, and nonlinear indices, to assess autonomic function during different seizure intervals. The study found significant differences in HRV indices based on hemispheric laterality, language dominancy, hippocampal atrophy, amygdala enlargement, sustained theta activity, and seizure frequency. HRV indices such as the root mean square of successive differences between heartbeats, pNN50, normalized low-frequency, normalized high-frequency, and the low-frequency/high-frequency ratio exhibited significant differences during the ictal period. Language dominancy, hippocampal atrophy, amygdala enlargement, and sustained theta activity were also found to affect HRV. Seizure frequency was correlated with HRV indices, suggesting a potential relationship with the risk of SUDEP.

Protective effect of Nardostachys jatamansi extract against lithium-pilocarpine-induced spontaneous recurrent seizures and associated cardiac irregularities in a rat model

ETHNOPHARMACOLOGICAL RELEVANCE

Nardostachys jatamansi (D.Don) DC. is a perennial herbaceous medicinal plant widely used for the ethnomedical treatment of various ailments. The underground parts of the plants are used in traditional medicine to manage epilepsy and other cardiovascular conditions.

AIM OF THE STUDY

The present study was undertaken to investigate the efficacy of a characterized hydroalcoholic extract (NJET) of Nardostachys jatamansi in the lithium-pilocarpine rat model of spontaneous recurrent seizures (SRS) and associated cardiac irregularities.

MATERIALS AND METHODS

NJET was prepared by percolation using 80% ethanol. The dried NEJT was subjected to UHPLC-qTOF-MS/MS for chemical characterization. Molecular docking studies were performed using the characterized compounds to understand mTOR interactions. The animals showing SRS following lithium-pilocarpine administration were treated with NJET for 6 weeks. Afterward, seizure severity, cardiac parameters, serum biochemistry, and histopathological parameters were studied. The cardiac tissue was processed for specific protein and gene expression studies.

RESULTS

The UHPLC-qTOF-MS/MS characterized 13 compounds in NJET. The identified compounds subjected to molecular docking showed promising binding affinities toward mTOR. There was a dose-dependent decrease in the severity of SRS following the extract administration. A reduction in mean arterial pressure and serum biochemical markers (lactate dehydrogenase and creatine kinase) was also observed following NJET treatment in epileptic animals. Histopathological investigations revealed reduced degenerative changes and decreased fibrosis following the extract treatment. The cardiac mRNA level of Mtor, Rps6, Hif1a, and Tgfb3 was reduced in the extract-treated groups. Further, a similar reduction in the protein expression of p-mTOR and HIF-1α was also observed following NJET treatment in the cardiac tissue.

CONCLUSIONS

The results concluded that NJET treatment reduces lithium-pilocarpine-induced recurrent seizures and associated cardiac irregularities via downregulation of the mTOR signalling pathway.

Association between postictal EEG suppression, postictal autonomic dysfunction, and sudden unexpected death in epilepsy: Evidence from intracranial EEG

OBJECTIVE

The association between postictal electroencephalogram (EEG) suppression (PES), autonomic dysfunction, and Sudden Unexpected Death in Epilepsy (SUDEP) remains poorly understood. We compared PES on simultaneous intracranial and scalp-EEG and evaluated the association of PES with postictal heart rate variability (HRV) and SUDEP outcome.

METHODS

Convulsive seizures were analyzed in patients with drug-resistant epilepsy at 5 centers. Intracranial PES was quantified using the Hilbert transform. HRV was quantified using root mean square of successive differences of interbeat intervals, low-frequency to high-frequency power ratio, and RR-intervals.

RESULTS

There were 64 seizures from 63 patients without SUDEP and 11 seizures from 6 SUDEP patients. PES occurred in 99% and 87% of seizures on intracranial-EEG and scalp-EEG, respectively. Mean PES duration in intracranial and scalp-EEG was similar. Intracranial PES was regional (<90% of channels) in 46% of seizures; scalp PES was generalized in all seizures. Generalized PES showed greater decrease in postictal parasympathetic activity than regional PES. PES duration and extent were similar between patients with and without SUDEP.

CONCLUSIONS

Regional intracranial PES can be present despite scalp-EEG demonstrating generalized or no PES. Postictal autonomic dysfunction correlates with the extent of PES.

SIGNIFICANCE

Intracranial-EEG demonstrates changes in autonomic regulatory networks not seen on scalp-EEG.

Cardiovascular autonomic function and baroreflex sensitivity in drug-resistant temporal lobe epilepsy

OBJECTIVE

Temporal lobe epilepsy (TLE) is often associated with autonomic manifestations. Sudden unexpected death in epilepsy (SUDEP) is a leading cause of mortality in epilepsy. Cardiac disturbances and autonomic dysfunction are the potential mechanisms behind SUDEP. Though heart rate variability (HRV) and autonomic function tests are well studied in drug-resistant temporal lobe epilepsy, there is a paucity of data on baroreflex sensitivity (BRS), a better marker of cardiac mortality in this population. We aimed to study the interictal cardiac autonomic function and BRS in people living with drug-resistant temporal lobe epilepsy compared to healthy controls.

MATERIALS AND METHODS

Thirty drug-resistant temporal lobe epilepsy (TLE) individuals and thirty healthy volunteers were recruited. Heart rate variability at rest, heart rate and blood pressure (BP) at rest, during deep breathing, postural change, BP response to isometric handgrip exercise, and baroreflex sensitivity were recorded in all study participants. The results were analyzed and compared between the two groups.

RESULTS

Compared to controls, the resting heart rate, HRV, parasympathetic reactivity test, and BRS significantly differed in people living with drug-resistant TLE. Time-domain indices including SDNN (p < 0.001), RMSSD (p < 0.001), NN50 (p < 0.001), and pNN50 (p < 0.001) were significantly reduced in the patients compared to controls. In frequency-domain indices, the total power was reduced (p < 0.001) in drug-resistant TLE. The parasympathetic reactivity such as changes in heart rate during deep breathing (E: I) (p < 0.02) and postural change (30:15) (p < 0.005) were significantly reduced in the patients. Baroreflex sensitivity was also significantly reduced in the drug-resistant TLE group (p < 0.001).

CONCLUSION

The present study findings are suggestive of parasympathetic dysfunction in drug-resistant TLE. Reduced HRV and BRS may increase the risk of SUDEP in people living with epilepsy.

Early transient dysautonomia predicts the risk of infantile epileptic spasm syndrome onset: A prospective cohort study

Background

Infantile epileptic spasm syndrome (IESS) is an age-dependent epileptic encephalopathy with a significant risk of developmental regression. This study investigates the association between heart rate variability (HRV) in infants at risk of IESS and the clinical onset of IESS.

Methods

Sixty neonates at risk of IESS were prospectively followed from birth to 12 months with simultaneous electroencephalogram (EEG) and electrocardiogram recordings for 60 min at every 2-month interval. HRV metrics were calculated from 5 min time-epoch during sleep including frequency domain measures, Poincare analysis including cardiac vagal index (CVI) and cardiac sympathetic index (CSI), and detrended fluctuation analysis (DFA α1, DFA α2). To assess the effect of each HRV metric at the 2-month baseline on the time until the first occurrence of either hypsarrhythmia on EEG and/or clinical spasm, univariate cox-proportional hazard models were fitted for each HRV metric.

Results

Infantile epileptic spasm syndrome was diagnosed in 20/60 (33%) of the cohort in a 12-month follow-up and 3 (5%) were lost to follow-up. The median age of developing hypsarrhythmia was 25 (7-53) weeks and clinical spasms at 24 (8-40) weeks. Three (5%) patients had clinical spasms without hypsarrhythmia, and 5 (8%) patients had hypsarrhythmia before clinical spasms at the initial presentation. The infants with high CSI (hazard ratio 2.5, 95% CI 1.2-5.2, P = 0.01) and high DFA α1 (hazard ratio 16, 95% CI 1.1-240, P = 0.04) at 2 months were more likely to develop hypsarrhythmia by the first year of age. There was a trend toward decreasing CSI and DFA α1 and increasing CVI in the first 8 months of age.

Conclusion

Our data suggest that relative sympathetic predominance at an early age of 2 months may be a potential predictor for developing IESS. Hence, early HRV patterns may provide valuable prognostic information in children at risk of IESS allowing early detection and optimization of cognitive outcomes. Whether early intervention to restore sympathovagal balance per se would provide clinical benefit must be addressed by future studies.

Omega-3 fatty acids in bipolar patients with a low omega-3 index and reduced heart rate variability: the "BIPO-3" trial

Background

Research suggests that a low omega-3 index may contribute to the low heart rate variability and the increased risk of cardiovascular morbidity and mortality in bipolar disorders. However, so far, no intervention trial with EPA and DHA has been conducted in bipolar patients attempting to increase their heart rate variability.

Methods

119 patients with bipolar disorder according to DSM-IV were screened, with 55 euthymic bipolar patients—owing to inclusion criteria (e.g. low omega-3 index (< 6%), SDNN < 60 ms.)—being enrolled in a randomized, double-blind, 12-week parallel study design with omega-3 fatty acids (4 capsules of 530 mg EPA, 150 mg DHA) or corn oil as a placebo, in addition to usual treatment. Heart rate variability as well as the omega-3 index were measured at baseline and at the endpoint of the study.

Results

A total of 42 patients (omega-3: n = 23, corn oil: n = 19) successfully completed the study after 12 weeks. There was a significant increase in the omega-3 index (value at endpoint minus value at baseline) in the omega-3 group compared to the corn oil group (p < 0.0001). However, there was no significant difference in the change of the SDNN (value at endpoint minus value at baseline) between the treatment groups (p = 0.22). In addition, no correlation between changes in SDNN and change in the omega-3 index could be detected in the omega-3 group (correlation coefficient = 0.02, p = 0.94) or the corn oil group (correlation coefficient =  − 0.11, p = 0.91). Similarly, no significant differences between corn oil and omega-3 group regarding the change of LF (p = 0.19), HF (p = 0.34) and LF/HF ratio (p = 0.84) could be demonstrated.

Conclusions

In our randomized, controlled intervention trial in euthymic bipolar patients with a low omega-3 index and reduced heart rate variability no significant effect of omega-3 fatty acids on SDNN or frequency-domain measures HF, LF and LF/HF ratio could be detected. Possible reasons include, among others, the effect of psychotropic medication present in our trial and/or the genetics of bipolar disorder itself. Further research is needed to test these hypotheses.

Trial registration ClinicalTrials.gov, NCT00891826. Registered 01 May 2009–Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT00891826

How predictable is heart rate variability in Brazilian patients with drug-resistant mesial temporal lobe epilepsy?

This study aimed to compare heart rate variability (HRV) in patients with drug-resistant mesial temporal lobe epilepsy (MTLE) with healthy controls and to analyze their clinical and sociodemographic variables predictive for HRV. Thirty-nine consecutive patients with drug-resistant MTLE were included in the study. The control group included twenty-seven healthy participants matched by age and gender. Seven HRV indices (HR, RR, rMSSD, SDNN, LF, HF, and LF/HF) were compared between patients and controls. The clinical and sociodemographic variables independently associated with the HRV indices were identified by multiple linear regression. In comparison with controls, the patients with MTLE showed a significant reduction in RR, rMSSD, SDNN, LF, HF, and LF/HF indices (t value 1.97-5.97, p < 0.05). Multiple regression models showed that disease duration predicted 11-22% of the analyzed HRV indices. Time domain indices showed higher association with disease duration than coefficients in frequency domain. Patients with drug-resistant MTLE present cardiac autonomic tone dysfunction, showing a significant reduction in their HRV indices (RR, SDNN, rMSSD, LF, HF, and LF/HF). Disease duration has a negative association with all HRV indices. This study contributes to understanding the relationship between MTLE and the cardiac autonomic tone, with possible implications for sudden unexpected death in epilepsy.

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.

Alice in Wonderland Syndrome-Like Seizure and Refractory Supraventricular Tachycardia

Alice in Wonderland syndrome (AIWS) is a rarely curious visual perceptual disorder which has been associated with diverse neurologic and psychiatric problems. It may be a manifestation in migraine, epileptic seizures, encephalitis, other brain lesions, medication-related side effects, schizophrenia, and depressive disorders. Principal character of AIWS is the disproportion between the external world and the self-image in which micropsia (objects appear smaller), macropsia (objects appear larger), and teleopsia (objects appear further away) are frequently reported. The cases of temporal lobe epilepsy may present with complex visual auras of visual distortions (e.g., micropsia and macropsia) like AIWS. We report an unusual case of an elderly man who presented with AIWS, focal impaired awareness seizures, ictal tachyarrhythmia, multiple episodes of transient visual disturbances of macropsia and transient loss of consciousness. During those symptoms, telemetry showed self-limited supraventricular tachycardia several times which could not be regulated with heart rate-controlled medication. The electroencephalography was later tested and showed rhythmic theta activity over the right cerebral hemisphere. He was treated with levetiracetam, and all his symptoms and tachyarrhythmias were gradually resolved thereafter. Refractory response to treatment would remind the physicians to reassess for the correct diagnosis.

Interictal autonomic dysfunction in patients with epilepsy

Background

Autonomic nervous system (ANS) symptoms are frequently present in people with epilepsy (PwE). They are generally more prominent when they originate from the temporal lobe. We aim to investigate the alterations of autonomic functions during the interictal period in patient with temporal lobe epilepsy (TLE) and idiopathic generalized epilepsy (IGE) using heart-based tests, blood pressure (BP)-based tests and sympathetic skin response (SSR). Forty-eight PwE with disease duration ranging from 2 to 15 years and 51 healthy individuals were studied. Long-term electroencephalography (EEG) monitoring, the heart rate variability (HRV) during normal breathing, deep breathing, Valsalva maneuver and standing, BP responses during standing, to isometric hand grip and to mental arithmetic, and the SSR was recorded for all participants.

Results

31 patients with TLE and 17 with IGE showed lower RR-IV values during deep breathing, Valsalva maneuver and standing, but not during rest, impaired BP responses during standing, isometric hand grip, and mental arithmetic. Also, prolonged SSR latencies. Within PwE group, no difference was noticed between males and females, nor between the left and right temporal lobes.

Conclusion

Abnormal autonomic (sympathetic and parasympathetic) regulatory functions suggest that epilepsy may alter the autonomic function and this is not only in TLE but rather in IGE too. These autonomic changes are irrespective of the localization of epilepsy between the two hemispheres. The ANS changes in epileptic patients, particularly those with autonomic symptoms, confirm that electrophysiologic measures of autonomic function may be of value in preventing sudden unexpected death in epilepsy.

Interictal autonomic changes in persons with epilepsy (PWE) on carbamazepine (CBZ) versus other anti-seizure drug monotherapy: A cross-sectional study

OBJECTIVE

Epilepsy is one of the most prevalent neurological conditions and carbamazepine is a commonly used anti-seizure drug (ASD), especially in developing nations. There are reports of carbamazepine causing atrioventricular conduction defects and autonomic dysfunctions and its implication in Sudden Unexpected Death in Epilepsy (SUDEP) is controversial. We planned this study to assess the effect of carbamazepine (CBZ) on autonomic function compared to other ASDs in persons with epilepsy.

METHODS

In this cross-sectional study, we assessed the sympathetic and parasympathetic autonomic functions in persons with epilepsy (PWE) on CBZ versus other anti-seizure monotherapy using tests of heart rate variability including its time-, frequency- and non-linear domains, heart rate response to deep breathing, valsalva maneuver, and blood pressure response to isometric handgrip.

RESULTS

Persons with epilepsy on CBZ monotherapy did not show a significant reduction in the time domain parameter SDRR compared to other ASDs used as monotherapy (mean ± SD, 38.04 ± 18.75 ms vs 44.37 ± 20.35 ms; p = 0.125). However, PWE on CBZ had significantly lower time-domain measurements including RMSSD (mean ± SD 31.95 ± 17.29 ms vs 42.02 ± 22.29 ms; p = 0.018), SDSD (mean ± SD 31.91 ± 17.26 ms vs 41.96 ± 22.27 ms; p 0.018), and pNN50 [median (IQR) 05.45(0.69-25.37) vs 16.38(2.32-36.83); p = 0.030]. Frequency domain measures of HRV, heart rate responses to deep breathing, valsalva maneuver and tilt-testing and BP responses to valsalva and tilt-testing were not significantly different between the groups.

CONCLUSION

The findings of our study indicate reduced parasympathetic activity in persons on CBZ monotherapy compared to other ASDs, which may pose risk of SUDEP. Carbamazepine may thus be avoided in those at risk of autonomic dysfunction and SUDEP.

Heart Rate Variability in Insulo-Opercular Epilepsy

Background: We aimed to evaluate heart rate variability (HRV) changes in insulo-opercular epilepsy (IOE) and after insulo-opercular surgery. Methods: We analyzed 5-min resting HRV of IOE patients before and after surgery. Patients’ SUDEP-7 risk inventory scores were also calculated. Results were compared with age- and sex-matched patients with temporal lobe epilepsy (TLE) and healthy individuals. Results: There were no differences in HRV measurements between IOE, TLE, and healthy control groups (and within each IOE group and TLE group) in preoperative and postoperative periods. In IOE patients, the SUDEP-7 score was positively correlated with pNN50 (percentage of successive RR intervals that differ by more than 50 ms) (p = 0.008) and RMSSD (root mean square of successive RR interval differences) (p = 0.019). We stratified IOE patients into those whose preoperative RMSSD values were below (Group 1a = 7) versus above (Group 1b = 9) a cut-off threshold of 31 ms (median value of a healthy population from a previous study). In group 1a, all HRV values significantly increased after surgery. In group 1b, time-domain parameters significantly decreased postoperatively. Conclusions: Our results suggest that in IOE, HRV may be either decreased in parasympathetic tone or increased globally in both sympathetic and parasympathetic tones. We found no evidence that insulo-opercular surgeries lead to major autonomic dysfunction when a good seizure outcome is reached. The increase in parasympathetic tone observed preoperatively may be of clinical concern, as it was positively correlated with the SUDEP-7 score.

Severe autonomic nervous system imbalance in Lennox-Gastaut syndrome patients demonstrated by heart rate variability recordings

OBJECTIVE

Patients diagnosed with Lennox Gastaut syndrome (LGS), an epileptic encephalopathy characterized by usually drug resistant generalized and focal seizures, are often considered as candidates for vagus nerve stimulation (VNS). Recent research shows that heart rate variability (HRV) differs in epilepsy patients and is related to VNS treatment response. This study investigated pre-ictal HRV in generalized onset seizures of patients with LGS in correlation with their VNS response.

METHODS

In drug resistant epilepsy (DRE) patients diagnosed with LGS video-electroencephalography recording was performed during their pre-surgical evaluation. Six HRV parameters (time and-, frequency domain, non-linear parameters) were evaluated for every seizure in epochs of 10 min at baseline (60 to 50 min before seizure onset) and pre-ictally (10 min prior to seizure onset). The results were correlated to VNS response after one year of VNS therapy.

RESULTS

Seven patients and 31 seizures were included, two patients were classified as VNS responders (≥ 50 % seizure reduction). No difference in pre-ictal HRV parameters between VNS responders and VNS non-responders could be found, but high frequency (HF) power, reflecting the parasympathetic tone increased significantly in the pre-ictal epoch in both VNS responders and VNS non-responders (p = 0.017, p = 0.004).

SIGNIFICANCE

In this pilot data pre-ictal HRV did not differ in VNS responders compared to VNS non-responders, but showed a significant increase in HF power - a parasympathetic overdrive - in both VNS responders and VNS non-responders. This sudden autonomic imbalance might have an influence on the cardiovascular system in the ictal period. Generalized tonic-clonic seizures are regarded as the main risk factor for SUDEP and severe seizure-induced autonomic imbalance may play a role in the pathophysiological pathway.

Altered Relationship Between Heart Rate Variability and fMRI-Based Functional Connectivity in People With Epilepsy

Background: Disruptions in central autonomic processes in people with epilepsy have been studied through evaluation of heart rate variability (HRV). Decreased HRV appears in epilepsy compared to healthy controls, suggesting a shift in autonomic balance toward sympathetic dominance; recent studies have associated HRV changes with seizure severity and outcome of interventions. However, the processes underlying these autonomic changes remain unclear. We examined the nature of these changes by assessing alterations in whole-brain functional connectivity, and relating those alterations to HRV. Methods: We examined regional brain activity and functional organization in 28 drug-resistant epilepsy patients and 16 healthy controls using resting-state functional magnetic resonance imaging (fMRI). We employed an HRV state-dependent functional connectivity (FC) framework with low and high HRV states derived from the following four cardiac-related variables: 1. RR interval, 2. root mean square of successive differences (RMSSD), 4. low-frequency HRV (0.04-0.15 Hz; LF-HRV) and high-frequency HRV (0.15-0.40 Hz; HF-HRV). The effect of group (epilepsy vs. controls), HRV state (low vs. high) and the interactions of group and state were assessed using a mixed analysis of variance (ANOVA). We assessed FC within and between 7 large-scale functional networks consisting of cortical regions and 4 subcortical networks, the amygdala, hippocampus, basal ganglia and thalamus networks. Results: Consistent with previous studies, decreased RR interval (increased heart rate) and decreased HF-HRV appeared in people with epilepsy compared to healthy controls. For both groups, fluctuations in heart rate were positively correlated with BOLD activity in bilateral thalamus and regions of the cerebellum, and negatively correlated with BOLD activity in the insula, putamen, superior temporal gyrus and inferior frontal gyrus. Connectivity strength in patients between right thalamus and ventral attention network (mainly insula) increased in the high LF-HRV state compared to low LF-HRV; the opposite trend appeared in healthy controls. A similar pattern emerged for connectivity between the thalamus and basal ganglia. Conclusion: The findings suggest that resting connectivity patterns between the thalamus and other structures underlying HRV expression are modified in people with drug-resistant epilepsy compared to healthy controls.

Electrocardiographic Abnormalities and Mortality in Epilepsy Patients

Background and Objectives: People with epilepsy (PWE) have a 2–3 times higher mortality rate than the general population. Sudden unexpected death in epilepsy (SUDEP) comprises a significant proportion of premature deaths, whereas sudden cardiac death (SCD) is among the leading causes of sudden death in the general population. Cardiac pathologies are significantly more prevalent in PWE. Whether electrocardiographic (ECG) parameters are associated with remote death in PWE has yet to be elucidated. The study objective was to assess whether interictal ECG parameters are associated with mortality in the long-term. Materials and Methods: The study involved 471 epilepsy patients who were hospitalized after a bilateral tonic-clonic seizure(s). ECG parameters were obtained on the day of hospitalization (heart rate, PQ interval, QRS complex, QT interval, heart rate corrected QT interval (QTc), ST segment and T wave changes), as well as reported ECG abnormalities. Mortality data were obtained from the Latvian National Cause-of-Death database 3–11, mean 7.0 years after hospitalization. The association between the ECG parameters and the long-term clinical outcome were examined. Results: At the time of assessment, 75.4% of patients were alive and 24.6% were deceased. Short QTc interval (odds ratio (OR) 4.780; 95% confidence interval (CI) 1.668–13.698; p = 0.004) was associated with a remote death. After the exclusion of known comorbidities with high mortality rates, short QTc (OR 4.631) and ECG signs of left ventricular hypertrophy (OR 5.009) were associated with a remote death. Conclusions: The association between routine 12-lead rest ECG parameters—short QTc interval and a pattern of left ventricular hypertrophy—and remote death in epilepsy patients was found. To the best of our knowledge, this is the first study to associate rest ECG parameters with remote death in an epileptic population.

Cardiac Autonomic Dysfunction and Risk of Sudden Unexpected Death in Epilepsy

OBJECTIVE

We aimed to test whether patients who died of sudden unexpected death in epilepsy (SUDEP) had an abnormal cardiac autonomic response to sympathetic stimulation by hyperventilation.

METHODS

We conducted a retrospective, observational, case-control study of a group of patients who died of SUDEP and controls who were matched to the patients for epilepsy type, drug resistance, sex, age at EEG recording, age at onset of epilepsy, and duration of epilepsy. We analyzed the heart rate (HR) and HR variability (HRV) at rest and during and after hyperventilation performed during the patient's last EEG recording before SUDEP. In each group, changes over time in HRV indexes were analyzed with linear mixed models.

RESULTS

Twenty patients were included in each group. In the control group, the HR increased and the root mean square of successive RR-interval differences (RMSSD) decreased during the hyperventilation and then returned to the baseline values. In the SUDEP group, however, the HR and RMSSD did not change significantly during or after hyperventilation. A difference in HR between the end of the hyperventilation and 4 minutes after its end discriminated well between patients with SUDEP and control patients (area under the receiver operating characteristic curve 0.870, sensitivity 85%, specificity 75%).

CONCLUSION

Most of patients with subsequent SUDEP have an abnormal cardiac autonomic response to sympathetic stimulation through hyperventilation. An index reflecting the change in HR on hyperventilation might be predictive of the risk of SUDEP and could be used to select patients at risk of SUDEP for inclusion in trials assessing protective measures.

Ictal and Interictal Cardiac Manifestations in Epilepsy. A Review of Their Relation With an Altered Central Control of Autonomic Functions and With the Risk of SUDEP

There is a complex interrelation between epilepsy and cardiac pathology, with both acute and long-term effects of seizures on the regulation of the cardiac rhythm and on the heart functioning. A specific issue is the potential relation between these cardiac manifestations and the risk of Sudden and Unexpected Death in Epilepsy (SUDEP), with unclear respective role of centrally-control ictal changes, long-term epilepsy-related dysregulation of the neurovegetative control and direct effects on the heart function. In the present review, we detailed available data about ictal cardiac changes, along with interictal cardiac manifestations associated with long-term functional and structural alterations of the heart. Pathophysiological mechanisms of these cardiac changes are discussed, with a specific focus on central mechanisms and the investigation of a possible deregulation of the central control of autonomic functions in addition to the role of catecholamine and hypoxemia on heart.

Interictal autonomic dysfunction

PURPOSE OF REVIEW

Epilepsy is associated with autonomic dysfunction. Here, we provide an up-to-date review on measures of interictal autonomic function, focusing on heart rate variability (HRV), baroreflex sensitivity (BRS) and electrodermal activity (EDA).

RECENT FINDINGS

Resting HRV, BRS and EDA are altered in patients with epilepsy compared with healthy controls. A larger body of work is available for HRV compared with BRS and EDA, and points to interictal HRV derangements across a wide range of epilepsies, including focal, generalized, and combined generalized and focal epilepsies. HRV alterations are most pronounced in temporal lobe epilepsy, Dravet syndrome and drug-resistant and chronic epilepsies. There are conflicting data on the effect of antiseizure medications on measures of interictal autonomic function. However, carbamazepine has been associated with decreased HRV. Epilepsy surgery and vagus nerve stimulation do not appear to have substantial impact on measures of interictal autonomic function but well designed studies are lacking.

SUMMARY

Patients with epilepsy, particularly those with longstanding uncontrolled seizures, have measurable alterations of resting autonomic function. These alterations may be relevant to the increased risk of premature mortality in epilepsy, including sudden unexpected death in epilepsy, which warrants investigation in future research.

Impairment of Cardiac Autonomic Nerve Function in Pre-school Children With Intractable Epilepsy

Objective: Intractable epilepsy and uncontrolled seizures could affect cardiac function and the autonomic nerve system with a negative impact on children's growth. The aim of this study was to investigate the variability and complexity of cardiac autonomic function in pre-school children with pediatric intractable epilepsy (PIE). Methods: Twenty four-hour Holter electrocardiograms (ECGs) from 93 patients and 46 healthy control subjects aged 3-6 years were analyzed by the methods of traditional heart rate variability (HRV), multiscale entropy (MSE), and Kurths-Wessel symbolization entropy (KWSE). Receiver operating characteristic (ROC) curve analysis was used to estimate the overall discrimination ability. Net reclassification improvement (NRI) and integrated discrimination improvement (IDI) models were also analyzed. Results: Pre-school children with PIE had significantly lower HRV measurements than healthy controls in time (Mean_RR, SDRR, RMSSD, pNN50) and frequency (VLF, LF, HF, LF/HF, TP) domains. For the MSE analysis, area 1_5 in awake state was lower, and areas 6_15 and 6_20 in sleep state were higher in PIE with a significant statistical difference. KWSE in the PIE group was also inferior to that in healthy controls. In ROC curve analysis, pNN50 had the greatest discriminatory power for PIE. Based on both NRI and IDI models, the combination of MSE indices (wake: area1_5 and sleep: area6_20) and KWSE (m = 2, τ = 1, α = 0.16) with traditional HRV measures had greater discriminatory power than any of the single HRV measures. Significance: Impaired HRV and complexity were found in pre-school children with PIE. HRV, MSE, and KWSE could discriminate patients with PIE from subjects with normal cardiac complexity. These findings suggested that the MSE and KWSE methods may be helpful for assessing and understanding heart rate dynamics in younger children with epilepsy.

Interictal Heart Rate Variability Analysis Reveals Lateralization of Cardiac Autonomic Control in Temporal Lobe Epilepsy

Purpose: The temporal lobe, a critical hub for cognition, also plays a central role in the regulation of autonomic cardiovascular functions. Lesions in this area are usually associated with abnormalities in the regulation of heart rate (HR) and blood pressure (BP). The analysis of the heart rate variability (HRV) is useful to evaluate the cardiac parasympathetic nervous system activity. This study aims at comparing HRV changes occurring in two groups of patients suffering from Temporal Lobe Epilepsy (TLE). To that aim, we evaluated patients differentiated by the right or left location of the epileptic foci.

Materials and Methods: Fifty-two adult patients with a diagnosis of TLE were enrolled. Each patient underwent a 20-min EEG + EKG recording in resting state. According to the localization of epileptic focus, patients were divided into two subgroups: right TLE (R-TLE) and left TLE (L-TLE). HRV parameters were calculated with a short-lasting analysis of EKG recordings. Time-domain and frequency domain-related, as well as non-linear analysis, parameters, were compared between the two groups.

Results: Compared to the R-TLE group, L-TLE subjects showed a significant decrease in low frequency (LF) (p < 0.01) and low frequency/high-frequency ratio (LF/HF) (p < 0.001) as well as increased HF values (p < 0.01), a parameter indicative of the presence of an increased cardiac vagal tone. These results were also confirmed in the subgroup analysis that took into account the seizure types, responses to antiepileptic drugs, seizure frequencies, and etiology.

Conclusions: The main finding of the study is that, compared to R-TLE, L-TLE is associated with increased cardiac vagal tone. These results indicate that patients with TLE exhibit a lateralized cardiac autonomic control. L-TLE patients may have a lower risk of developing cardiac dysfunctions and less susceptible to develop Sudden Death for Epilepsy (SUDEP).

Photoplethysmographic evaluation of generalized tonic-clonic seizures

OBJECTIVE

Photoplethysmography (PPG) is an optical technique measuring variations of blood perfusion in peripheral tissues. We evaluated alterations in PPG signals in relationship to the occurrence of generalized tonic-clonic seizures (GTCSs) in patients with epilepsy to evaluate the feasibility of seizure detection.

METHODS

During electroencephalographic (EEG) long-term monitoring, patients wore portable wristband sensor(s) on their wrists or ankles recording PPG signals. We analyzed PPG signals during three time periods, which were defined with respect to seizures detected on EEG: (1) baseline (>30 minutes prior to seizure), (2) preseizure period, and (3) postseizure period. Furthermore, we selected five random control segments during seizure-free periods. PPG features, including frequency, amplitude, duration, slope, smoothness, and area under the curve, were automatically calculated. We used a linear mixed-effect model to evaluate changes in PPG features between different time periods in an attempt to identify signal changes that detect seizures.

RESULTS

We prospectively enrolled 174 patients from the epilepsy monitoring unit at Boston Children's Hospital. Twenty-five GTCSs were recorded from 13 patients. Data from the first recorded GTCS of each patient were included in the analysis. We observed an increase in PPG frequency during pre- and postseizure periods that was higher than the changes during seizure-free periods (frequency increase: preseizure = 0.22 Hz, postseizure = 0.58 Hz vs changes during seizure-free period = 0.05 Hz). The PPG slope decreased significantly by 56.71 nW/s during preseizure periods compared to seizure-free periods. Additionally, the smoothness increased significantly by 0.22 nW/s during the postseizure period compared to seizure-free periods.

SIGNIFICANCE

Monitoring of PPG signals may assist in the detection of GTCSs in patients with epilepsy. PPG may serve as a promising biomarker for future seizure detection systems and may contribute to future seizure prediction systems.

Peri-ictal heart rate variability parameters as surrogate markers of seizure severity

This study aims at defining objective parameters reflecting the severity of peri-ictal autonomic changes and their relation to post-ictal generalized electroencephalography (EEG) suppression (PGES), with the view that such changes could be detected by wearable seizure detection systems and prove useful to assess the risk of sudden unexpected death in epilepsy (SUDEP). To this purpose, we assessed peri-ictal changes in heart rate variability (HRV) and correlated them with seizure duration, intensity of electromyography-based ictal muscle activity, and presence and duration of post-ictal generalized EEG suppression (PGES). We evaluated 75 motor seizures from 40 patients, including 61 generalized tonic-clonic seizures (GTCS) and 14 other major motor seizure types. For all major motor seizures, HRV measurements demonstrated a significantly decreased parasympathetic activity and increased sympathetic activity in the post-ictal period. The post-ictal increased sympathetic activity was significantly higher for GTCS as compared with non-GTCS. The degree of peri-ictal decreased parasympathetic activity and increased sympathetic activity was associated with longer PGES (>20 s), longer seizure duration, and greater intensity of ictal muscle activity. Mean post-ictal heart rate (HR) was an independent predictor of PGES duration, seizure duration, and intensity of ictal muscle contraction. Our results indicate that peri-ictal changes in HRV are potential biomarkers of major motor seizure severity.

Heart Rate Variability and Omega-3 Index in Euthymic Patients with Bipolar Disorders

Background:

Affective disorders are associated with an increased risk of cardiovascular disease, which, at least partly, appears to be independent of psychopharmacological treatments used to manage these disorders. Reduced heart rate variability (SDNN) and a low Omega-3 Index have been shown to be associated with increased risk for death after myocardial infarction. Therefore, we set out to investigate heart rate variability and the Omega-3 Index in euthymic patients with bipolar disorders.

Methods:

We assessed heart rate variability (SDNN) and the Omega-3 Index in 90 euthymic, mostly medicated patients with bipolar disorders (Bipolar-I, Bipolar-II) on stable psychotropic medication, free of significant medical comorbidity and in 62 healthy controls. Heart rate variability was measured from electrocardiography under a standardized 30 minutes resting state condition. Age, sex, BMI, smoking, alcohol consumption and caffeine consumption as potential confounders were also assessed.

Results:

Heart rate variability (SDNN) was significantly lower in patients with bipolar disorders compared to healthy controls (35.4 msec versus 60.7 msec; P < 0.0001), whereas the Omega-3 Index did not differ significantly between the groups (5.2% versus 5.3%). In a linear regression model, only group membership (patients with bipolar disorders versus healthy controls) and age significantly predicted heart rate variability (SDNN).

Conclusion:

Heart rate variability (SDNN) may provide a useful tool to study the impact of interventions aimed at reducing the increased risk of cardiovascular disease in euthymic patients with bipolar disorders. The difference in SDNN between cases and controls cannot be explained by a difference in the Omega-3 Index.

Neuro-arrhythmology: a challenging field of action and research: a review from the Task Force of Neuro-arrhythmology of Italian Association of Arrhythmias and Cardiac Pacing

: There is a growing interest in the study of the mechanisms of heart and brain interactions with the aim to improve the management of high-impact cardiac rhythm disorders, first of all atrial fibrillation. However, there are several topics to which the scientific interests of cardiologists and neurologists converge constituting the basis for enhancing the development of neuro-arrhythmology. This multidisciplinary field should cover a wide spectrum of diseases, even beyond the classical framework corresponding to stroke and atrial fibrillation and include the complex issues of seizures as well as loss of consciousness and syncope. The implications of a more focused interaction between neurologists and cardiologists in the field of neuro-arrhythmology should include in perspective the institution of research networks specifically devoted to investigate 'from bench to bedside' the complex pathophysiological links of the abovementioned diseases, with involvement of scientists in the field of biochemistry, genetics, molecular medicine, physiology, pathology and bioengineering. An investment in the field could have important implications in the perspectives of a more personalized approach to patients and diseases, in the context of 'precision'medicine. Large datasets and electronic medical records, with the approach typical of 'big data' could enhance the possibility of new findings with potentially important clinical implications. Finally, the interaction between neurologists and cardiologists involved in arrythmia management should have some organizational implications, with new models of healthcare delivery based on multidisciplinary assistance, similarly to that applied in the case of syncope units.

Use your words: The role of emotion labeling in regulating emotion in borderline personality disorder

Borderline personality disorder (BPD) treatments emphasize emotion labeling to decrease negative emotion and facilitate emotion regulation. However, no studies have examined emotion labeling in BPD or its impact on intentional emotion regulation. The present study examined the impact of emotion labeling on emotion and intentional emotion regulation attempts across self-reported and physiological indices (i.e., skin conductance response [SCR], respiratory sinus arrhythmia [RSA]) in BPD and healthy control (HC) groups. Participants listened to emotionally-evocative scripts and were either instructed to type the emotions that they were experiencing (labeling) or the objects they could imagine seeing in the script (control) into a computer. Following this, they were instructed to use either mindfulness or cognitive reappraisal to decrease their emotion. Self-reported, RSA, and SCR indices of negative emotion were collected throughout and analyzed using generalized estimating equations. Findings indicated that the BPD group experienced higher RSA during emotion labeling compared to the control task, but the HC group did not. HCs reported lower negative emotion after emotion labeling when implementing both emotion regulation strategies compared to the control task, but the BPD group did not. These findings suggest that emotion labeling may activate emotion regulatory systems in BPD and can potentiate intentional emotion regulation in HCs.

Resting-State Neural Firing Rate Is Linked to Cardiac-Cycle Duration in the Human Cingulate and Parahippocampal Cortices

Stimulation and functional imaging studies have revealed the existence of a large network of cortical regions involved in the regulation of heart rate. However, very little is known about the link between cortical neural firing and cardiac-cycle duration (CCD). Here, we analyze single-unit and multiunit data obtained in humans at rest, and show that firing rate covaries with CCD in 16.7% of the sample (25 of 150). The link between firing rate and CCD was most prevalent in the anterior medial temporal lobe (entorhinal and perirhinal cortices, anterior hippocampus, and amygdala), where 36% (18 of 50) of the units show the effect, and to a lesser extent in the mid-to-anterior cingulate cortex (11.1%, 5 of 45). The variance in firing rate explained by CCD ranged from 0.5 to 11%. Several lines of analysis indicate that neural firing influences CCD, rather than the other way around, and that neural firing affects CCD through vagally mediated mechanisms in most cases. These results show that part of the spontaneous fluctuations in firing rate can be attributed to the cortical control of the cardiac cycle. The fine tuning of the regulation of CCD represents a novel physiological factor accounting for spontaneous variance in firing rate. It remains to be determined whether the "noise" introduced in firing rate by the regulation of CCD is detrimental or beneficial to the cognitive information processing carried out in the parahippocampal and cingulate regions.SIGNIFICANCE STATEMENT Fluctuations in heart rate are known to be under the control of cortical structures, but spontaneous fluctuations in cortical firing rate, or "noise," have seldom been related to heart rate. Here, we analyze unit activity in humans at rest and show that spontaneous fluctuations in neural firing in the medial temporal lobe, as well as in the mid-to-anterior cingulate cortex, influence heart rate. This phenomenon was particularly pronounced in the entorhinal and perirhinal cortices, where it could be observed in one of three neurons. Our results show that part of spontaneous firing rate variability in regions best known for their cognitive role in spatial navigation and memory corresponds to precise physiological regulations.

Spectral entropy indicates electrophysiological and hemodynamic changes in drug-resistant epilepsy - A multimodal MREG study

Objective

Epilepsy causes measurable irregularity over a range of brain signal frequencies, as well as autonomic nervous system functions that modulate heart and respiratory rate variability. Imaging dynamic neuronal signals utilizing simultaneously acquired ultra-fast 10 Hz magnetic resonance encephalography (MREG), direct current electroencephalography (DC-EEG), and near-infrared spectroscopy (NIRS) can provide a more comprehensive picture of human brain function. Spectral entropy (SE) is a nonlinear method to summarize signal power irregularity over measured frequencies. SE was used as a joint measure to study whether spectral signal irregularity over a range of brain signal frequencies based on synchronous multimodal brain signals could provide new insights in the neural underpinnings of epileptiform activity.

Methods

Ten patients with focal drug-resistant epilepsy (DRE) and ten healthy controls (HC) were scanned with 10 Hz MREG sequence in combination with EEG, NIRS (measuring oxygenated, deoxygenated, and total hemoglobin: HbO, Hb, and HbT, respectively), and cardiorespiratory signals. After pre-processing, voxelwise SE_MREG was estimated from MREG data. Different neurophysiological and physiological subfrequency band signals were further estimated from MREG, DC-EEG, and NIRS: fullband (0–5 Hz, FB), near FB (0.08–5 Hz, NFB), brain pulsations in very-low (0.009–0.08 Hz, VLFP), respiratory (0.12–0.4 Hz, RFP), and cardiac (0.7–1.6 Hz, CFP) frequency bands. Global dynamic fluctuations in MREG and NIRS were analyzed in windows of 2 min with 50% overlap.

Results

Right thalamus, cingulate gyrus, inferior frontal gyrus, and frontal pole showed significantly higher SE_MREG in DRE patients compared to HC. In DRE patients, SE of cortical Hb was significantly reduced in FB (p = .045), NFB (p = .017), and CFP (p = .038), while both HbO and HbT were significantly reduced in RFP (p = .038, p = .045, respectively). Dynamic SE of HbT was reduced in DRE patients in RFP during minutes 2 to 6. Fitting to the frontal MREG and NIRS results, DRE patients showed a significant increase in SE_EEG in FB in fronto-central and parieto-occipital regions, in VLFP in parieto-central region, accompanied with a significant decrease in RFP in frontal pole and parietal and occipital (O2, Oz) regions.

Conclusion

This is the first study to show altered spectral entropy from synchronous MREG, EEG, and NIRS in DRE patients. Higher SE_MREG in DRE patients in anterior cingulate gyrus together with SE_EEG and SE_NIRS results in 0.12–0.4 Hz can be linked to altered parasympathetic function and respiratory pulsations in the brain. Higher SE_MREG in thalamus in DRE patients is connected to disturbances in anatomical and functional connections in epilepsy. Findings suggest that spectral irregularity of both electrophysiological and hemodynamic signals are altered in specific way depending on the physiological frequency range.

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Simultaneous imaging methods indicate spectral irregularity in neurovascular and electrophysiological brain pulsations in DRE.

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Altered spectral entropy in EEG, NIRS and BOLD indicate dysfunctional brain pulsations in respiratory frequency in epilepsy.

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Spectral irregularity (0-5 Hz) of BOLD in right thalamus supports previous structural and functional findings in epilepsy.

Closed-loop Neuropharmacology for Epilepsy: Distant Dream or Future Reality?

Epilepsy is considered the most frequent severe neurological condition but most patients treated with medication become seizure free. The management of treatment, however, is highly empirical, mainly relying on observation. A closed-loop therapy for epilepsy would be very valuable for more efficient treatment regimens. Here we discuss monitoring treatment (therapeutic drug monitoring) and the potential developments in this field, as well as providing a review of potential biomarkers that could be used to monitor the disease activity. Finally, we consider the pharmacogenetic input in epilepsy treatment.

Heart rate variability measurement in epilepsy: How can we move from research to clinical practice?

Our objective was to critically evaluate the literature surrounding heart rate variability (HRV) in people with epilepsy and to make recommendations as to how future research could be directed to facilitate and accelerate integration into clinical practice. We reviewed relevant HRV publications including those involving human subjects with seizures. HRV has been studied in patients with epilepsy for more than 30 years and, overall, patients with epilepsy display altered interictal HRV, suggesting a shift in autonomic balance toward sympathetic dominance. This derangement appears more severe in those with temporal lobe epilepsy and drug-resistant epilepsy. Normal diurnal variation in HRV is also disturbed in at least some people with epilepsy, but this aspect has received less study. Some therapeutic interventions, including vagus nerve stimulation and antiepileptic medications, may partially normalize altered HRV, but studies in this area are sometimes contradictory. During seizures, the changes in HRV may be complex, but the general trend is toward a further increase in sympathetic overactivity. Research in HRV in people with epilepsy has been limited by inconsistent experimental protocols and studies that are often underpowered. HRV measurement has the potential to aid clinical epilepsy management in several possible ways. HRV may be useful in predicting which patients are likely to benefit from surgical interventions such as vagus nerve stimulation and focal cerebral resection. As well, HRV could eventually have utility as a biomarker of risk for sudden unexpected death in epilepsy (SUDEP). However, at present, the inconsistent measurement protocols used in research are hindering translation into clinical practice. A minimum protocol for HRV evaluation, to be used in all studies involving epilepsy patients, is necessary to eventually allow HRV to become a useful tool for clinicians. We propose a straightforward protocol, involving 5-minute measurements of root mean square of successive differences in wakefulness and light sleep.

Deceleration and acceleration capacities of heart rate in patients with drug-resistant epilepsy

OBJECTIVE

Epilepsy and seizures can have dramatic effects on cardiac function. The aim of the present study was to investigate deceleration capacity, acceleration capacity and their 24-h fluctuations of heart rate variability in patients with drug-resistant epilepsy.

METHODS

Deceleration capacity, acceleration capacity of heart rate and their 24-h dynamics derived from the phase rectified signal averaging method as well as traditional measures were analyzed in 39 patients with drug-resistant epilepsy and 33 healthy control subjects using 24-h electrocardiogram recordings. The discriminatory power of heart rate variability measures were validated by assessment of the area under the receiver operating characteristic curve. Net reclassification improvement and integrated discrimination improvement models were also estimated.

RESULTS

Both deceleration capacity and absolute values of acceleration capacity were significantly lower in patients with drug-resistant epilepsy. The abnormal suppression of absolute deceleration capacity and acceleration capacity values were observed throughout the 24-h recording time (peaked at about 3 to 5 A.M.). Deceleration capacity had the greatest discriminatory power to differentiate the patients from the healthy controls. Moreover, in both net reclassification improvement and integrated discrimination improvement models, the combination of acceleration capacity or deceleration capacity with traditional heart rate variability measures has greater discriminatory power than any of the single heart rate variability features.

INTERPRETATION

Drug-resistant epilepsy was associated with a significant inhibition of vagal modulation of heart rate, which was more pronounced during the night than during the day. These findings indicate that phase rectified signal averaging method may serve as a complementary approach for characterizing and understanding the neuro-pathophysiology in epilepsy, and may provide a new clue to sudden unexpected death in epilepsy.

Deficient post-ictal cardiorespiratory compensatory mechanisms mediated by the periaqueductal gray may lead to death in a mouse model of SUDEP

Post-ictal cardiorespiratory failure is implicated as a major cause of sudden unexpected death in epilepsy (SUDEP) in patients. The DBA/1 mouse model of SUDEP is abnormally susceptible to fatal seizure-induced cardiorespiratory failure (S-CRF) induced by convulsant drug, hyperthermia, electroshock, and acoustic stimulation. Clinical and pre-clinical studies have implicated periaqueductal gray (PAG) abnormalities in SUDEP. Recent functional neuroimaging studies observed that S-CRF resulted in selective changes in PAG neuronal activity in DBA/1 mice. The PAG plays a critical compensatory role for respiratory distress caused by numerous physiological challenges in non-epileptic individuals. These observations suggest that abnormalities in PAG-mediated cardiorespiratory modulation may contribute to S-CRF in DBA/1 mice. To evaluate this, electrical stimulation (20 Hz, 20-100 μA, 10 s) was presented in the PAG of anesthetized DBA/1 and C57BL/6 (non-epileptic) control mice, and post-stimulus changes in respiration [inter-breath interval (IBI)] and heart rate variability (HRV) were examined. The post-stimulus period was considered analogous to the post-ictal period when S-CRF occurred in previous DBA/1 mouse studies. PAG stimulation caused significant intensity-related decreases in IBI in both mouse strains. However, this effect was significantly reduced in DBA/1 vis-a-vis C57BL/6 mice. These changes began immediately following cessation of stimulation and remained significant for 10 s. This time period is critical for initiating resuscitation to successfully prevent seizure-induced death in previous DBA/1 mouse experiments. Significant post-stimulus increases in HRV were also seen at ≥60 μA in the PAG in C57BL/6 mice, which were absent in DBA/1 mice. These data along with previous neuroimaging findings suggest that compensatory cardiorespiratory modulation mediated by PAG is deficient, which may be important to the susceptibility of DBA/1 mice to S-CRF. These observations suggest that correcting this deficit pharmacologically or by electrical stimulation may help to prevent S-CRF. These findings further support the potential importance of PAG abnormalities to human SUDEP.

Chronic vagus nerve stimulation reverses heart rhythm complexity in patients with drug-resistant epilepsy: An assessment with multiscale entropy analysis

OBJECTIVE

Vagus nerve stimulation (VNS) is an adjunctive treatment in drug-resistant epilepsy. The alterations in heart rate dynamics through VNS are not well understood. This study aimed to determine changes in heart rhythm complexity in association with VNS and to relate the findings to the outcome of VNS treatment in patients with drug-resistant epilepsy.

METHODS

We prospectively analyzed 32 patients with drug-resistant epilepsy, who underwent VNS implantation, and 32 age- and sex-matched healthy control subjects. The interictal heartbeat intervals were analyzed using the heart rhythm complexity with multiscale entropy (MSE) and traditional heart rate variability (HRV) analyses based on ambulatory 24-hour electrocardiograms (ECGs).

RESULTS

Patients had significantly decreased complexity indices (Slope 5, Area 1-5, Area 6-15, Area 6-20) on MSE analysis and decreased HRV measurements (standard deviation of the heartbeat interval (SDNN), square root of the mean of sum of squares of the differences between adjacent RR intervals (RMSSD), pNN50, very low frequency (VLF), low frequency (LF), high frequency (HF), total power (TP)) in time and frequency domain analyses. After one year of VNS treatment in patients with drug-resistant epilepsy, there was a trend in an elevated MSE profile with significant higher values between the scales 1 and 9. Vagus nerve stimulation induces a more significant increase of MSE in VNS responders than those in the nonresponders. The conventional HRV measurements did not change.

CONCLUSION

Our results suggest that heart rhythm complexity is impaired in patients with drug-resistant epilepsy, and this is at least partially reversed by VNS treatment. Furthermore, VNS-induced effects on heart rate complexity may be associated with the therapeutic response to VNS in patients with drug-resistant epilepsy.

Sudden unexpected death in epilepsy: ongoing challenges in finding mechanisms and prevention

Purpose/aim of the study: To summarize recent studies on the pathophysiology and preventive strategies for SUDEP. Materials and methods: Databases and literature review. Results: Patients with epilepsy have a significantly higher risk of death than the general population. Sudden unexpected death in epilepsy (SUDEP) is the leading cause of sudden death among patients with epilepsy. Despite on-going research, there are still deficits in our knowledge about the mechanisms, genetic factors, and prevention of SUDEP. Current evidence suggests that cardiac arrhythmias, respiratory dysfunction, and brainstem arousal system dysfunction are the major mechanisms of SUDEP, and animal models support the role of neurotransmitters, especially serotonin and adenosine, in pathophysiology of SUDEP. Several mutations in the neurocardiogenic channelopathy genes have been identified as a possible cause of epilepsy and increased SUDEP risk. The lack of awareness that SUDEP can be a potential cause of premature death has been found in several surveys. In addition, medical legal cases demonstrate the need for more education about this condition. Several preventive strategies to reduce SUDEP have been proposed, including effective seizure control, nocturnal supervision, seizure monitoring, devices to protect the airway, and selective serotonin reuptake inhibitors. Further research is needed to determine the efficacy of these interventions. Conclusions: The major mechanisms of SUDEP include cardiac arrhythmias, respiratory dysfunction, and brainstem arousal system dysfunction. Effective control of seizures is the only effective strategy to prevent SUDEP. Other preventive interventions require more research.

Comparison of Autonomic Function before and after Surgical Intervention in Patients with Temporal Lobe Epilepsy

Background and Purpose

Refractory temporal lobe epilepsy (TLE) is commonly associated with imbalances in cardiovascular (CV) parasympathetic and sympathetic functions, which are treated using TLE surgery. We investigated the effect of hemispheric lateralization of seizure foci on autonomic CV functions before and after TLE surgery.

Methods

The study was conducted on patients with left TLE (LTLE, n = 23) and right TLE (RTLE, n = 30) undergoing unilateral TLE surgery. To assess the autonomic CV functions, changes in the heart rate (ΔHR) and blood pressure (BP) were measured using a standardized battery of autonomic reactivity tests before surgery and at 3 and 6 months after surgery.

Results

Before surgery, ΔHR and the expiration to inspiration ratio (E:I) during the deep breathing test were higher in the LTLE group than in the RTLE group (both p < 0.001), but both outcomes were comparable between the groups at 3 and 6 months. ΔHR decreased at 3 and 6 months (p < 0.001 and 0.01, respectively) compared with preoperative values. The E:I at 3 months in the LTLE group was lower (p = 0.04) than the preoperative values. Decrease in systolic BP during the head-up tilt test was greater in the LTLE group than in the RTLE group (p = 0.002) before surgery. The maximum increase in diastolic BP during the cold pressor test was lower in the RTLE group at 6 months than that before surgery (p = 0.001) and in the LTLE group (p = 0.002).

Conclusions

We found that hemispheric lateralization of seizure foci in the temporal lobe had a differential effect on autonomic CV functions before surgery. Before surgery, parasympathetic reactivity was higher in the LTLE group, and sympathetic reactivity was higher in the RTLE group. After surgery, autonomic CV functions were comparable between the groups, suggesting that TLE surgery stabilizes autonomic CV functions.

Analysis of heart rate variability and risk factors for SUDEP in patients with drug-resistant epilepsy

BACKGROUND

Cardiac problems have been suggested as causes of sudden unexpected death in epilepsy (SUDEP). Our aim was to investigate possible associations of cardiac autonomic functions based on heart rate variability (HRV) parameters with risk factors of SUDEP in patients with drug-resistant epilepsy.

METHODS

Forty-seven patients with drug-resistant seizures and 45 healthy control subjects were enrolled in the study. Interictal time domain parameters of HRV were evaluated with 24-hour Holter recordings. Potential SUDEP risk in patients with epilepsy was estimated using an inventory of seven validated SUDEP risk factors (The SUDEP-7 inventory).

RESULTS

When compared with the healthy controls, all time domain measures (SDNN-24, SDNN-index, SDANN-index, RMSSD and pNN50) were significantly suppressed in the patient group. Scores of the SUDEP-7 inventory ranged from 1 to 9 with a median 4 out of a maximum possible risk score of 10. Maximum heart rate value in 24-hour Holter recordings and epilepsy duration were correlated with the SUDEP-7 scores (r=0.3, p=0.03). We found no significant association with HRV measures and SUDEP-7 risk factors. One patient diagnosed with Dravet syndrome died of SUDEP, which was autopsy confirmed; his SUDEP-7 inventory score was 7, HRV measures were significantly diminished, and his maximum heart rate (HR) was 208beats/min (maximum HR is between 104 and 188beats/min in normal subjects).

CONCLUSION

Patients with drug-resistant epilepsy present with significantly lower HRV measures, which may increase the risk for sudden cardiac death. Increased heart rate and diminished HRV measures may constitute one of the possible mechanisms underlying SUDEP and should be diagnosed in patients with epilepsy.

Status epilepticus in dogs and cats, part 1: etiopathogenesis, epidemiology, and diagnosis

OBJECTIVE

To review current knowledge of the etiopathogenesis, diagnosis, and consequences of status epilepticus (SE) in veterinary patients.

DATA SOURCES

Human and veterinary literature, including clinical and laboratory research and reviews.

ETIOPATHOGENESIS

Status epilepticus is a common emergency in dogs and cats, and may be the first manifestation of a seizure disorder. It results from the failure of termination of an isolated seizure. Multiple factors are involved in SE, including initiation and maintenance of neuronal excitability, neuronal network synchronization, and brain microenvironmental contributions to ictogenesis. Underlying etiologies of epilepsy and SE in dogs and cats are generally classified as genetic (idiopathic), structural-metabolic, or unknown.

DIAGNOSIS

Diagnosis of convulsive SE is usually made based on historical information and the nature of the seizures. Patient specific variables, such as the history, age of seizure onset, and physical and interictal neurological examination findings can help hone the rule out list, and are used to guide selection and prioritization of diagnostic tests. Electroencephalographic monitoring is routinely used in people to diagnose SE and guide patient care decisions, but is infrequently performed in veterinary medicine. Nonconvulsive status epilepticus has been recognized in veterinary patients; routine electroencephalography would aid in the diagnosis of this phenomenon in dogs and cats.

CLINICAL SEQUELAE

Status epilepticus is a medical emergency that can result in life-threatening complications involving the brain and systemic organs. Status epilepticus often requires comprehensive diagnostic testing, treatment with multiple anticonvulsant agents, and intensive supportive care.

Neurological Complications of Cardiac Disease

This article focuses on the complex interactions between the cardiovascular and neurologic systems. Initially, we focus on neurological complications in children with congenital heart disease both secondary to the underlying cardiac disease and complications of interventions. We later discuss diagnosis and management of common syncope syndromes with emphasis on vasovagal syncope. We also review the diagnosis, classification, and management of children and adolescents with postural orthostatic tachycardia syndrome. Lastly, we discuss long QT syndrome and sudden unexpected death in epilepsy (SUDEP), reviewing advances in genetics and current knowledge of pathophysiology of these conditions. This article attempts to provide an overview of these disorders with focus on pathophysiology, advances in molecular genetics, and current medical interventions.

The pathophysiology of cardiac dysfunction in epilepsy

Alterations in cardiac electrophysiology are an established consequence of long-standing drug resistant epilepsy. Patients with chronic epilepsy display abnormalities in both sinoatrial node pacemaker current as well as ventricular repolarizing current that places them at a greater risk of developing life-threatening cardiac arrhythmias. The development of cardiac arrhythmias secondary to drug resistant epilepsy is believed to be a key mechanism underlying the phenomenon of Sudden Unexpected Death in EPilepsy (SUDEP). Though an increasing amount of studies examining both animal models and human patients have provided evidence that chronic epilepsy can detrimentally affect cardiac function, the underlying pathophysiology remains unclear. Recent work has shown the expression of several key cardiac ion channels to be altered in animal models of genetic and acquired epilepsies. This has led to the currently held paradigm that cardiac ion channel expression may be secondarily altered as a consequence of seizure activity-resulting in electrophysiological cardiac dysfunction. Furthermore, cortical autonomic dysfunction - resulting from seizure activity-has also been suggested to play a role, whereby seizure activity may indirectly influence cardiac function via altering centrally-mediated autonomic output to the heart. In this review, we discuss various cardiac dysrhythmias associated with seizure events-including tachycardia, bradycardia and QT prolongation, both ictally and inter-ictally, as well as the role of the autonomic nervous system. We further discuss key ion channels expressed in both the heart and the brain that have been shown to be altered in epilepsy and may be responsible for the development of cardiac dysrhythmias secondary to chronic epilepsy.

Predicting seizures in untreated temporal lobe epilepsy using point-process nonlinear models of heartbeat dynamics

Symptoms of temporal lobe epilepsy (TLE) are frequently associated with autonomic dysregulation, whose underlying biological processes are thought to strongly contribute to sudden unexpected death in epilepsy (SUDEP). While abnormal cardiovascular patterns commonly occur during ictal events, putative patterns of autonomic cardiac effects during pre-ictal (PRE) periods (i.e. periods preceding seizures) are still unknown. In this study, we investigated TLE-related heart rate variability (HRV) through instantaneous, nonlinear estimates of cardiovascular oscillations during inter-ictal (INT) and PRE periods. ECG recordings from 12 patients with TLE were processed to extract standard HRV indices, as well as indices of instantaneous HRV complexity (dominant Lyapunov exponent and entropy) and higher-order statistics (bispectra) obtained through definition of inhomogeneous point-process nonlinear models, employing Volterra-Laguerre expansions of linear, quadratic, and cubic kernels. Experimental results demonstrate that the best INT vs. PRE classification performance (balanced accuracy: 73.91%) was achieved only when retaining the time-varying, nonlinear, and non-stationary structure of heartbeat dynamical features. The proposed approach opens novel important avenues in predicting ictal events using information gathered from cardiovascular signals exclusively.

Genetic biomarkers for the risk of seizures in long QT syndrome

OBJECTIVES

The coprevalence, severity, and biomarkers for seizures and arrhythmias in long QT syndrome (LQTS) remain incompletely understood.

METHODS

Using the Rochester-based LQTS Registry, this study included large cohorts of LQTS1-3 participants (LQTS⁺, n = 965) and those without a LQTS mutation (LQTS^-, n = 936).

RESULTS

Compared to LQTS^- participants, there was a higher prevalence of LQTS1, LQTS2, and LQTS⁺ participants classified as having seizures (p < 0.001, i.e., history of seizures/epilepsy or antiseizure medication). LQTS⁺ participants with longer corrected QT interval (QT_c) durations were more likely to have seizures. LQTS2 mutations in the KCNH2 pore domain were positive predictors for both arrhythmias and seizures. In contrast, mutations in the cyclic nucleotide binding domain (cNBD) of KCNH2 conferred a negative risk of seizures, but not arrhythmias. LQTS2, KCNH2-pore, KCNH2-cNBD, QT_c duration, and sex were independent predictors of seizures. LQTS⁺ participants with seizures had significantly longer QT_c durations, and a history of seizures was the strongest independent predictor of arrhythmias (hazard ratio 4.09, 95% confidence interval 2.63-6.36, p < 0.001).

CONCLUSIONS

This study highlights potential biomarkers for neurocardiac electrical abnormalities in LQTS.