Heart rate variability in patients with epilepsy

Factors that affect interictal cardiovascular autonomic dysfunction in temporal lobe epilepsy: role of hippocampal sclerosis

The aim of this study was to evaluate possible factors affecting interictal cardiovascular autonomic function in temporal lobe epilepsy with complex partial seizures, paying special attention to hippocampal sclerosis. The study was carried out with 88 patients with epilepsy (22 with left hippocampal sclerosis, 22 with right hippocampal sclerosis, and 44 without hippocampal sclerosis) and 44 healthy subjects. All subjects underwent three tests of cardiac autonomic function: heart rate variation during resting activity, heart rate variation in response to deep breathing and blood pressure response to rising quickly from the supine position. Hippocampal sclerosis and disease duration were found to have significantly important effects on parasympathetic autonomic function, whereas seizure control and type of antiepileptic drug had significant effects on sympathetic autonomic function. This study shows that in addition to factors related to the chronic nature of epilepsy and antiepileptic drug use, hippocampal sclerosis may cause autonomic dysfunction during the interictal period in persons with temporal lobe epilepsy.

Sudden unexpected death in epilepsy: risk factors and potential pathomechanisms

Sudden unexpected death in epilepsy (SUDEP) is the most common cause of death directly related to epilepsy, and most frequently occurs in people with chronic epilepsy. The main risk factors for SUDEP are associated with poorly controlled seizures, suggesting that most cases of SUDEP are seizure-related events. Dysregulation in cardiac and respiratory physiology, dysfunction in systemic and cerebral circulation physiology, and seizure-induced hormonal and metabolic changes might all contribute to SUDEP. Cardiac factors include bradyarrhythmias and asystole, as well as tachyarrhythmias and alterations to cardiac repolarization. Altered electrolytes and blood pH, as well as the release of catecholamines, modulate cardiac excitability and might facilitate arrhythmias. Respiratory symptoms are not uncommon during seizures and comprise central apnea or bradypnea, and, less frequently, obstruction of the airways and neurogenic pulmonary edema. Alterations to autonomic function, such as a reduction in heart rate variability or disturbed baroreflex sensitivity, can impair the body's capacity to cope with challenging situations of elevated stress, such as seizures. Here, we summarize data on the incidence of and risk factors for SUDEP, and consider the pathophysiological aspects of chronic epilepsy that might lead to sudden death. We suggest that SUDEP is caused by the fatal coexistence of several predisposing and triggering factors.

The circadian rhythm and its interaction with human epilepsy: a review of literature

Knowledge on the interaction between circadian rhythm and human epilepsy is relatively poor, although if it exists, this interaction may be of value for better knowledge of pathophysiology and for timing of diagnostic procedures and therapy. It appears that human seizure occurrence may have 24-h rhythmicity, depending on the origin. These findings are endorsed by animal studies. Rats placed in constant darkness showed spontaneous limbic seizures occurring in an endogenously mediated circadian pattern. More studies are available on the influence of epilepsy on circadian rhythms. Significant differences in chronotypes between patients with different epilepsy syndromes have been found and numerous studies have described influences of epilepsy and seizures on sleep. In contrast, knowledge on (core) body temperature and clock genes in patients is minimal. Reduced heart rate variability and changed hormone levels, which are under the influence of the biological clock, have been observed in people with epilepsy. In short, large gaps in the knowledge about the interaction of circadian rhythm and human epilepsy still remain. Proposals for studies in this borderline area between the biological clock and epilepsy will be discussed.

What is known about the mechanisms underlying SUDEP?

This article highlights studies in three major domains of potential mechanisms of sudden unexplained death in epilepsy (SUDEP): cardiac, respiratory, and autonomic. Ictal cardiac arrest is a clinically rare but well-recognized potential mechanism of SUDEP. Studies have failed to identify preexisting cardiac electrophysiologic or structural abnormalities that distinguish SUDEP persons. Some degree of pulmonary congestion is a common autopsy finding, but severe pulmonary edema occurs very rarely with seizures. In contrast, periictal apnea and hypoxia occur commonly with generalized tonic-clonic seizures and, to a lesser degree, with complex partial seizures. There are several animal models of postictal respiratory arrest. Postictal respiratory arrest in audiogenic seizure mice can be induced by serotonin receptor inhibition or prevented by selective serotonin reuptake inhibitor (SSRI) drugs. Reduced heart rate variability occurs in patients with refractory epilepsy and can be induced in animal seizure models, but its precise role in predisposing persons to sudden death requires further investigation.

Evaluation of conduction properties of somatic and sympathetic sudomotor fibers in patients with epilepsy

To assess the function of fast somatic nerve fibers and sympathetic sudomotor system in patients with partial or generalized seizures, receiving various therapeutic regimes. The authors studied 60 patients (mean age 36.7 +/- 12.5 years) and 60 matched healthy controls by clinical, conventional nerve conduction study, and sympathetic skin responses (SSR) from hand and foot. Compared with controls, patients showed a tendency, occasional reaching significant level, to conduction slowing and amplitude reduction in the sensory and less often in the motor nerve study. Clinical signs of neuropathy were disclosed in 8.3% of patients, whereas at least one abnormal sensory parameter was evident in 18.3%. Mean SSR latencies in the patients were significantly prolonged. At least one SSR abnormality was shown in 20 (33.3%) patients; six of these had absent SSR from the hand or/and the foot. Polytherapy (vs. monotherapy) and topiramate, but not any other particular drug, seemed to have a negative effect on SSR measurements. The results suggested that despite the insignificant clinical manifestations of neuropathy, an electrophysiological examination was able to demonstrate some subclinical abnormalities of the fast somatic fibers in the peripheral nerves and of the sympathetic sudomotor function in a considerable number of epileptic patients.

Modulation of cardiac autonomic balance with adjuvant yoga therapy in patients with refractory epilepsy

The practice of yoga regulates body physiology through control of posture, breathing, and meditation. Effects of yoga on autonomic functions of patients with refractory epilepsy, as quantified by standardized autonomic function tests (AFTs), were determined. The yoga group (n=18) received supervised training in yoga, and the exercise group (n=16) practiced simple routine exercises. AFTs were repeated after 10 weeks of daily sessions. Data were compared with those of healthy volunteers (n=142). The yoga group showed significant improvement in parasympathetic parameters and a decrease in seizure frequency scores. There was no improvement in blood pressure parameters in either group. Two patients in the yoga group achieved normal autonomic functions at the end of 10 weeks of therapy, whereas there were no changes in the exercise group. The data suggest that yoga may have a role as an adjuvant therapy in the management of autonomic dysfunction in patients with refractory epilepsy.

Changes in autonomic cardiac control in patients with epilepsy after discontinuation of antiepileptic drugs: a randomized controlled withdrawal study

The aim of this study was to assess cardiac autonomic control in patients with epilepsy before and after withdrawal of antiepileptic drugs (AEDs). The study was prospective, randomized and double blinded. Spectral analysis of heart rate variability (HRV) in 24 h ECG-registration before and after withdrawal of AEDs was used to assess autonomic cardiac control. The assessment of HRV with spectral analysis was based on sinus rhythm and normal heart beats [normal to normal beat (NN)]. Thirty-nine patients had 24 h rhythms free from any ectopic beats both before and after intervention, and were included in the analysis. Significant differences were found in the withdrawal group: filtered RR intervals for all 5 min segments of the analysis; percentage of differences between adjacent filtered RR intervals that are greater than 50 ms for the whole analysis; very low frequency power; low frequency power and high frequency power. The results demonstrate that slow withdrawal of AEDs in seizure-free patients with epilepsy on drug mono-therapy resulted in an increase in both parasympathetic and sympathetic functions, indicative of increased power amongst patients following cessation of AED treatment. As low HRV has been associated with increased mortality in patients with other diseases, this increased HRV may be beneficial.

Simultaneous recording of electroencephalogram and blood pressure in conscious telemetered rats during ictal state

INTRODUCTION

Seizures are accompanied by autonomic dysfunction which in turn influences cardiovascular variables. A method for simultaneous acquisition of electroencephalogram (EEG) and arterial blood pressure (BP) during seizures in conscious animals has not previously been described.

METHODS

The effect of pentylenetetrazole (PTZ) was first studied on isolated rat atria. EEG and BP were then monitored simultaneously in conscious rats, with a chronically implanted radiotelemetric device. Changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) during epileptiform seizures induced by intraperitoneal administration of PTZ were monitored to validate the method.

RESULTS

PTZ did not have significant inotropic or chronotropic effect in isolated atria. The radiotelemetry system used to acquire data in unrestrained conscious rats enabled us to study neurological excitation (EEG) and cardiovascular variables (BP and HR) during seizures. Our results demonstrated that this method can be used to study the effect of neuronal excitation on cardiovascular variables and vice versa.

Non-invasive assessment of cardioregulatory autonomic functions in children with epilepsy

OBJECTIVES

We aimed to evaluate the interictal cardiovascular autonomic functions in pediatric patients with idiopathic epilepsy, both partial and generalized.

MATERIALS AND METHODS

The study included 25 patients with idiopathic epilepsy and 50 control subjects. Patients underwent five standardized clinical cardiovascular reflex autonomic tests [resting heart rate (HR), HR response to deep breathing and to Valsalva maneuver, the 30:15 ratio of HR response to standing, and blood pressure response to standing], as well as a 12 lead surface electrocardiogram. Heart rate variability (HRV) was tested via 24-h Holter monitoring and the time domain parameters (SDNN, PNN50, rMSDD) were assessed. Excretion of vanillyl mandelic acid and metanephrine was measured in 24-h urine collection.

RESULTS

Clinical reflex autonomic tests showed mild dysfunction in 8%, moderate dysfunction in 44% and severe dysfunction in 4% of patients. The HRV parameter, SDNN, was reduced in all age groups, while rMSDD and PNN50 were reduced only in the older age group. Metanephrine levels were significantly reduced in the patients group. Patients with uncontrolled epilepsy had a significantly higher frequency of autonomic dysfunction as assessed by clinical scoring.

CONCLUSION

Cardiac autonomic dysfunction is not uncommon in pediatric patients with epilepsy. Altered cardiovascular regulation seems to be related to the epilepsy itself rather than to the characteristics of the disorder.

Heart rate variability in patients with untreated epilepsy

BACKGROUND

Several studies have reported reduced heart rate variability (HRV) in patients with chronic epilepsy under treatment with antiepileptic drugs. This impairment in cardiac autonomic control might be of relevance in relation to the risk of sudden unexpected death in patients with chronic refractory epilepsy. Little information is, however, available on HRV in untreated patients with newly diagnosed epilepsy.

METHODS

We used spectral analysis to assess HRV based on 24h ambulatory EKG recordings in 22 consecutive untreated patients with epilepsy (15 with localization-related, 4 with generalized idiopathic and 3 with undetermined epilepsy). The HRV in these patients was compared with 22 age and sex matched healthy controls.

RESULTS

When analysing the full 24h recordings, there were no significant difference between the patients and the controls in any of the analyzed measures of HRV: standard deviation of RR-intervals (P=0.191), total power (P=0.170), very low frequency power (P=0.329), low frequency power (LF) (P=0.161), high frequency power (HF) (P=0.186) and the LF/HF ratio (P=0.472). The results were very similar for daytime and nighttime recordings.

CONCLUSION

Our results suggest that there is no major effect of epilepsy as such on HRV in patients with untreated epilepsy. It should be emphasized that this study assessed newly diagnosed patients and that the results may not be applicable to patients with chronic epilepsy.

Mortality in epilepsy

All studies report an increased mortality risk for people with epilepsy compared with the general population. Population-based studies have demonstrated that the increased mortality is often related to the cause of the epilepsy. Common etiologies include neoplasia, cerebrovascular disease, and pneumonia. Deaths in selected cohorts, such as sudden unexpected death in epilepsy (SUDEP), status epilepticus (SE), suicides, and accidents are more frequently epilepsy-related. SUDEP is a particular cause for concern in younger people, and whether and when SUDEP should be discussed with patients with epilepsy remain problematic issues. Risk factors for SUDEP include generalized tonic-clonic seizures, increased seizure frequency, concomitant learning disability, and antiepileptic drug polypharmacy. The overall incidence of SE may be increasing, although case fatality rates remain constant. Mortality is frequently secondary to acute symptomatic disorders. Poor compliance with treatment in patients with epilepsy accounts for a small proportion of deaths from SE. The incidence of suicide is increased, particularly for individuals with epilepsy and comorbid psychiatric conditions. Late mortality figures in patients undergoing epilepsy surgery vary and are likely to reflect differences in case selection. Future studies of mortality should be prospective and follow agreed guidelines to better quantify risk and causation in individual populations.

Circadian Variation in Heart-Rate Variability in Localization-related Epilepsy

PURPOSE

Case-control studies of sudden unexpected death in epilepsy (SUDEP) have reported that SUDEP is more likely to occur during sleep and thus presumably during night hours. The circadian variation of heart-rate variability (HRV) might be of relevance to this risk. We examined night versus daytime HRV in patients with newly diagnosed and refractory localization-related epilepsy, assessing the effects of drug treatment and epilepsy surgery on the night/daytime HRV ratio.

METHODS

We used spectral analysis to assess HRV and calculated the night-time (00.00-05.00)/daytime (07.30-21.30) ratio of HRV in 14 patients with newly diagnosed localization-related epilepsy before and during carbamazepine (CBZ) treatment and in 21 patients with temporal lobe epilepsy before and after epilepsy surgery. Both groups were compared with age- and sex-matched controls.

RESULTS

No significant differences were found from controls in the night/daytime ratios of HRV whether compared before or after initiation of treatment with CBZ in newly diagnosed epilepsy patients. When patients were used as their own controls, night/daytime ratios of standard deviation of RR intervals (p = 0.04) and total power (p = 0.04) were significantly lower during treatment than before. Compared with those of controls, the night/daytime ratios were lower in epilepsy surgery patients before surgery [low-frequency power (p = 0.04); high-frequency power (p = 0.04)]. Night/daytime ratios did not change significantly after surgery.

CONCLUSIONS

The HRV of the patients was more affected during night-time when the risk of SUDEP seems to be highest in such patients.

Risk factors in sudden death in epilepsy (SUDEP): the quest for mechanisms

People with epilepsy may die suddenly and unexpectedly without a structural pathological cause. Most SUDEP cases are likely to be related to seizures. SUDEP incidence varies and is <1:1,000 person-years among prevalent cases in the community and approximately 1:250 person years in specialist centres. Case-control studies identified certain risk factors, some potentially amenable to manipulation, including uncontrolled convulsive seizures and factors relating to treatment and supervision. Both respiratory and cardiac mechanisms are important. The apparent protective effect of lay supervision supports an important role for respiratory factors, in part amenable to intervention by simple measures. Whereas malignant tachyarrhythmias are rare during seizures, sinus bradycardia/arrest, although infrequent, is well documented. Both types of arrhythmias can have a genetic basis. This article reviews SUDEP and explores the potential of coexisting liability to cardiac arrhythmias as a contributory factor, while acknowledging that at present, bridging evidence between cardiac inherited gene determinants and SUDEP is lacking.

Sudden unexpected death in epilepsy: a search for risk factors

Sudden unexpected death in epilepsy (SUDEP) is the commonest cause of seizure-related mortality in people with refractory epilepsy. Of the 6140 patients registered with the Epilepsy Unit at the Western Infirmary in Glasgow between 1982 and 2005, 529 had died, 62 (11.7%) of whom succumbed to SUDEP. All but 2 deaths occurred at home; 3 were witnessed. Two living controls were matched with each SUDEP case for year of birth, gender, and syndromic classification. Mean duration of epilepsy was significantly longer in cases compared with controls (P=0.001). More people succumbing to SUDEP had had a seizure within the previous year (P=0.007). There were no significant associations between SUDEP and a history of generalized tonic-clonic seizures, drug polytherapy, and current use of carbamazepine. There is an urgent need for a large-scale, prospective, international, community-based study of SUDEP to explore more closely the risk factors to plan preventive strategies.

Cardiac Vagal Activation by Adrenocorticotropic Hormone Treatment in Infants with West Syndrome

West syndrome (WS) is a generalized epileptic syndrome of infancy and early childhood with various etiologies, and consists of a triad of infantile spasm, arrest or regress of psychomotor development and specific electroencephalogram (EEG) pattern of hypsarrhythmia. WS had been believed to be refractory, but recent evidence supports effectiveness of adrenocorticotropic hormone (ACTH) treatment. The ACTH treatment, however, has a problem that it is often accompanied by adverse autonomic symptoms. We therefore examined heart rate variability (HRV) for assessing cardiac autonomic functions in WS and prospectively observed the changes during ACTH treatment. We studied 15 patients with WS and 9 age-matched controls during sleep (EEG stage 2). Compared with controls, the patients with WS were greater in the low-frequency component (LF) of HRV, an index reflecting sympatho-vagal interaction (p = 0.02), but were comparable for high-frequency component (HF) and LF-to-HF ratio (LF/HF), indices reflecting cardiac vagal activity and sympathetic predominance, respectively. During ACTH treatment, heart rate decreased (p < 0.01), LF and HF increased (p < 0.01), and LF/HF did not differ significantly. These results indicate that WS might be accompanied by autonomic changes and that ACTH treatment enhances parasympathetic function and causes bradycardia.

Impaired baroreflex function in temporal lobe epilepsy

Changes of cardiovascular function are frequent in temporal lobe epilepsy (TLE). The baroreflex - the most important reflex for cardiovascular stability - has not been studied systematically in TLE. We evaluated cardiovascular variability and baroreflex function in TLE. In 22 TLE patients and 20 controls, we continuously monitored heart rate (HR) and blood pressure (BP). Time-domain parameters were derived from recordings at rest and from standard cardiovascular reflex tests. Spectral analysis determined sympathetic and parasympathetic modulation of HR and BP in the low (LF-power) and high frequency range (HF-power). We calculated the relative LF- and HF-powers of HR in relation to the sum of LF- and HF-powers. LF/HF-ratio of HR was assessed as a parameter of sympatheticovagal balance. LF-transfer function gain between BP and HR determined baroreflex function.Time-domain parameters did not differ between TLE patients and controls. Spectral analysis showed decreased absolute LF- and HF-powers but increased relative LF-power and LF/HF-ratio of HR in TLE. LF-transfer function gain between BP and HR was reduced in TLE (p<0.05). The reduction of absolute LF- and HF-powers indicates decreased total autonomic variability in TLE. However, increased relative LF-power and LF/HF-ratio of HR in TLE show a relative increase of sympathetic tone. Most importantly, we demonstrate an impaired baroreflex function in TLE. These cardiovascular autonomic abnormalities may contribute to cardiac arrhythmia in TLE.

The ictal bradycardia syndrome: localization and lateralization

PURPOSE

Previous studies have established the importance of the insular cortex and temporal lobe in cardiovascular autonomic modulation. Some investigators, based on the results of cortical stimulation response, functional imaging, EEG recordings of seizures, and lesional studies, have suggested that cardiac sympathetic and parasympathetic function may be lateralized, with sympathetic representation lateralized to the right insula, and parasympathetic, to the left. These studies have suggested that ictal bradycardia is most commonly a manifestation of activation of the left temporal and insular cortex. However, the evidence for this is inconsistent. We sought to assess critically the predictable value of ictal bradycardia for seizure localization and lateralization.

METHODS

In this study, we reviewed the localization of seizure activity in 13 consecutive patients with ictal bradycardia diagnosed during prolonged video-EEG monitoring at Mayo Clinic Rochester. The localization of electrographic seizure activity at seizure onset and bradycardia onset was identified in all patients. In addition, we performed a comprehensive review of the ictal bradycardia literature focusing on localization of seizure activity in ictal bradycardia cases.

RESULTS

All occurrences of ictal bradycardia in the 13 identified patients were associated with temporal lobe-onset seizures. However, no consistent lateralization of seizure activity was found at onset of seizure activity or at onset of bradycardia in this population. Seizure activity was bilateral at bradycardia onset in nine of 13 patients. The results from the literature review also showed that a predominance of patients had bilateral activity at bradycardia onset; however, more of the ictal bradycardia cases from the literature had left hemispheric localization of seizure onset.

CONCLUSIONS

Ictal bradycardia most often occurs in association with bilateral hemispheric seizure activity and is not a consistent lateralizing sign in localizing seizure onset. Our data do not support the existence of a strictly unilateral parasympathetic cardiomotor representation in the left hemisphere, as has been suggested.

No apparent effect of surgery for temporal lobe epilepsy on heart rate variability

BACKGROUND

Impaired cardiac autonomic function may contribute to the risk of sudden unexpected death in epilepsy (SUDEP). Clinical observations indicate that successful epilepsy surgery is associated with a reduced risk of SUDEP. However, in a previous study we found impaired cardiac control pre-surgically in patients with poor outcome of surgery, indicating an a priori lower risk in responders to epilepsy surgery. We have now examined the effect of surgery on cardiac autonomic control in the same patients.

METHODS

We used 24 h EKG recordings to assess heart rate variability (HRV) by spectral analysis in 21 consecutive patients after temporal lobe epilepsy surgery. The HRV was compared with healthy controls, with pre-surgical HRV in the same patients, and analyzed in relation to seizure control 1 year after surgery.

RESULTS

The patients with poor outcome after surgery had significantly lower SD of RR-intervals, total power, very low frequency power and low frequency power than matched healthy controls. The patients with favorable outcome did not differ from the controls, and the postoperative HRV was not different from HRV before surgery in any of the patient groups.

CONCLUSION

We could not demonstrate any effect on HRV of temporal lobe epilepsy surgery in these patients. The observed lower HRV in the poor outcome group was present already before epilepsy surgery as previously reported. Although our results need confirmation in a larger study, the observations suggest that the increased risk of SUDEP in patients failing epilepsy surgery may be due to a common factor predisposing to surgical failure, impaired HRV as well as to an increased risk of SUDEP.

Cardiac Autonomic Control in Patients with Refractory Epilepsy before and during Vagus Nerve Stimulation Treatment: A One-Year Follow-up Study

PURPOSE

To elucidate possible effect of vagus nerve stimulation (VNS) therapy on interictal heart rate (HR) variability in patients with refractory epilepsy before and after 1-year VNS treatment.

METHODS

A 24-hour electrocardiogram (ECG) was recorded at the baseline and after 12 months of VNS treatment in 14 patients with refractory epilepsy, and once in 28 healthy age- and sex-matched control subjects. Time and frequency domain measures, along with fractal and complexity measures of HR variability, were analyzed from the ECG recordings.

RESULTS

The mean value of the RR interval (p=0.008), standard deviation of N-N intervals (SDNN) (p<0.001), very-low frequency (VLF) (p<0.001), low-frequency (LF) (p=0.001), and high-frequency (HF) (p=0.002) spectral components of HR variability, and the Poincaré components SD(1) (p=0.005) and SD(2) (p<0.001) of the patients with refractory epilepsy were significantly lower than those of the control subjects before VNS implantation. The nocturnal increase in HR variability usually seen in the normal population was absent in patients with refractory epilepsy. VNS had no significant effects on any of the HR-variability indexes despite a significant reduction in the frequency of seizures.

CONCLUSIONS

HR variability was reduced, and the nocturnal increase in HR variability was not present in patients with refractory epilepsy. One-year treatment with VNS did not have a marked effect on HR variability, suggesting that impaired cardiovascular autonomic regulation is associated with the epileptic process itself rather than with recurrent seizures.

Sudden Unexpected Death in Epilepsy: A Review of Incidence and Risk Factors

Sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. However, SUDEP is rare in patients with new onset epilepsy and in patients in remission. Incidence is about 0.35 cases/1,000 person-years in population-based incidence cohort of epilepsy. Incidence is considerably higher in patients with chronic epilepsy, 1-2/1,000 person-years, and highest with severe, refractory seizures, 3-9/1,000. The highest rates occur from 20 to 40 years. Most SUDEP appears seizure-related. When witnessed, the fatal event generally occurred in association with generalized tonic-clonic seizure. Two recent case-control studies suggest that seizure frequency is the strongest risk factor for SUDEP: relative risk = 23 (95% CI = 3.2-170) for persons with > or =1 seizure during the year of observation versus seizure-free patients. Onset of epilepsy at an early age and long duration of the disorder are other risk factors. Although SUDEP has not been associated with the use of any particular antiepileptic drugs (AEDs), some case-control studies have pointed to an association between SUDEP and polytherapy with AEDs and frequent dose changes independent of seizure frequency. Although recent epidemiological studies have been helpful in identifying patients at risk for SUDEP, providing clues to mechanisms behind SUDEP, no single risk factor is common to all SUDEP, suggesting multiple mechanisms or trigger factors. Seizure control seems of paramount importance to prevent SUDEP. Further large-scale case-control studies are needed to assess the role of AEDs in order to form a basis for treatment strategies aiming at seizure control and prevention of SUDEP.

Suppressed circadian heart rate dynamics in temporal lobe epilepsy

OBJECTIVES

To measure interictal circadian rhythm of heart rate (HR) variability in patients with temporal lobe epilepsy (TLE) using a 24 hour ECG recording.

METHODS

Various conventional and dynamic fractal measures of HR variability were analysed in 17 patients with refractory TLE, 20 patients with well controlled TLE, and 37 healthy age and sex matched control subjects.

RESULTS

The SD of all RR intervals (p < 0.01), the measured power spectral components of HR variability (low frequency power (p < 0.01), high frequency power (p < 0.05)), and the SD1 (p < 0.05) and SD2 (p < 0.01) Poincaré two dimensional vector analysis measurements were suppressed in the patients. This suppression was observed during both day and night time; however, it was more pronounced at night, and nocturnal increase in HR variability usually seen in the normal population could not be detected in the patients. The HR variability measures did not correlate with the duration of epilepsy, the age of the patients, or with the anti-epileptic drugs used.

CONCLUSION

TLE was associated with reduced HR variability, which was more pronounced during night than day, and the nocturnal increase in HR variability was abolished in patients with TLE. The alteration in autonomic regulation of HR variability was similar in patients with both refractory and well controlled TLE.

Changes of blood pressure and heart rate variability precede a grand mal seizure in a pregnant woman

In order to evaluate blood pressure and heart rate variability as a potent diagnostic tool for different hypertensive pregnancy disorders we started a clinical trial recording these variables in early pregnancies predisposed for preeclampsia. During routine measurements one of the patients experienced a grand mal epileptic seizure. Since the parameters of both heart rate and blood pressure variability were sequentially altered immediately before the seizure, this case report provides an interesting insight into autonomic cardiovascular control in a developing convulsive fit and the pathophysiological generation of a grand mal seizure in pregnancy.

Heart rate variability and autonomic dysfunction in SSPE

Autonomic nervous system involvement in subacute sclerosing panencephalitis was studied in 29 patients by analysis of heart rate variability and compared with a control group which consisted of 20 age- and sex-matched healthy subjects. Holter recordings for 24 hours were obtained, and all recordings were analyzed using time-domain parameters. The patients with subacute sclerosing panencephalitis were found to have significantly lower values of standard deviation of all normal sinus intervals and triangular index when compared with the control group. Of 23 patients who had regular follow-up, 15 died in a period ranging from 1 to 13 months. Twelve of these patients had heart rate variability parameters lower than normal, but no significant difference was observed between the heart rate variability values of patients who survived or died. Also, there was no association between brain magnetic resonance imaging findings and heart rate variability indices. It is concluded that patients with subacute sclerosing panencephalitis have autonomic dysfunction; and this was thought to be mainly due to central involvement.

Cerebral autoregulation improves in epilepsy patients after temporal lobe surgery

Patients with temporal lobe epilepsy (TLE) often show increased cardiovascular sympathetic modulation during the interictal period, that decreases after epilepsy surgery. In this study, we evaluated whether temporal lobectomy changes autonomic modulation of cerebral blood flow velocity (CBFV) and cerebral autoregulation. We studied 16 TLE patients 3-4 months before and after surgery. We monitored heart rate (HR), blood pressure (BP), respiration, transcutaneous oxygen saturation (sat-O(2)), end-expiratory carbon dioxide partial pressure (pCO(2)) and middle cerebral artery CBFV. Spectral analysis was used to determine sympathetic and parasympathetic modulation of HR, BP and CBFV as powers of signal oscillations in the low frequency (LF) ranges from 0.04-0.15Hz (LF-power) and in the high frequency ranges from (HF) 0.15-0.5Hz (HF-power). LF-transfer function gain and phase shift between BP and CBFV were calculated as parameters of cerebral autoregulation. After surgery, HR, BP(mean), CBFV(mean), respiration, sat-O(2), pCO(2) and HF powers remained unchanged. LF-powers of HR, BP, CBFV and LF-transfer function gain had decreased while the phase angle had increased (p<0.05). The reduction of LF powers and LF-gain and the higher phase angle showed reduced sympathetic modulation and improved cerebral autoregulation. The enhanced cerebrovascular stability after surgery may improve autonomic balance in epilepsy patients.

Time and frequency domain analyses of heart rate variability in patients with epilepsy

Heart rate variability (HRV) is a useful tool for the detection of sympathetic-parasympathetic balance of autonomic nervous system in patients at risk of sudden death (SD). SD is more common in patients with epilepsy and the exact mechanisms of SD are unknown. Autonomic nervous system involvement in patients with epilepsy has rarely been studied and has shown conflicting results. Our purpose was to determine if HRV showed any changes in patients with epilepsy in comparison with normal population. A short period analysis of HRV was performed for both the frequency and time domain in 43 epilepsy patients who had generalized tonic-clonic seizures (GTCS) and who were not taking any medications and also in 43 age and sex matched controls. In the time domain analysis, patients displayed higher SDNN (standard deviation of all R-R intervals), SDANN (standard deviation of mean NN intervals in 5 min recordings) and HRV triangular index than did healthy subjects (p < 0.0001). Patients tended to display higher pNN50 (number of R-R intervals differed by > 50 ms from adjacent interval divided by the total number of all R-R intervals) and RMSSD (root-mean-square of successive differences) values than did healthy subjects, but the differences were not statistically significant (p > 0.05). In the frequency domain analysis, the spectral measures of HRV showed a reduction of high frequency (HF) values (is a marker of parasympathetic activity) and an increase of low frequency (LF) values (is a measure of sympathetic activity); as a result, the ratio between low and high frequencies (LF/HF) was significantly increased (p < 0.0001, p < 0.0001 and p < 0.001, respectively). Our data suggests an increase in the sympathetic control of the heart rate in epilepsy patients who have GTCS. This increased sympathetic activity could play a key role in the development of ventricular tachyarrhythmias in patients with epilepsy and may be related to the higher incidence of sudden death in this disorder as compared to controls.

Cardiovascular Regulation and Hippocampal Sclerosis

PURPOSE

Cardiovascular dysregulation has been detected in patients with temporal lobe epilepsy (TLE) by using cardiovascular reflex tests and analysis of heart rate variability (HRV). The two methods have not previously been used in the same study to compare them in the assessment of cardioregulatory function. Magnetic resonance imaging (MRI) is considered the best method to reveal structural changes such as hippocampal sclerosis associated with TLE. It is not known whether these structural changes modify cardioregulatory function in patients with TLE.

METHODS

Standard cardiovascular reflex tests and analysis of spectral and dynamic measures from 24-h electrocardiogram (ECG) recordings were performed for eight patients with and 31 patients without hippocampal sclerosis and for 72 control subjects. MRI also was performed in each patient to reveal hippocampal sclerosis.

RESULTS

Various measures of cardiovascular reflexes and HRV were diminished in patients with TLE compared with the control subjects. No significant differences were found in the measures obtained from the cardiovascular reflex tests or analysis of HRV between those with and without hippocampal sclerosis, although a nonsignificant trend toward reduced values was seen among those with hippocampal sclerosis. The values of cardiovascular reflexes and spectral analysis of HRV correlated with each other.

CONCLUSIONS

These results suggest that functional rather than structural changes related to TLE are involved mainly as a mechanism of altered cardioregulatory function. The cardiovascular reflex test and analysis of HRV both appear to be useful in studying cardioregulation in patients with TLE.

Medical risks in epilepsy: a review with focus on physical injuries, mortality, traffic accidents and their prevention

The present review aims at highlighting selective aspects of the medical risks in epilepsy and their prevention. Emphasis is put on accidents and physical injuries, including risk factors and effectiveness of prevention; mortality, its causes, risk factors and prevention of seizure-related deaths, as well as traffic accidents, their risk factors and the effectiveness of prevention. Accidents and injuries are slightly more frequent among people with epilepsy than in the general population. This increased risk is probably most prevalent in patients with symptomatic epilepsy and frequent seizures, most often in combination with associated handicaps. The majority of accidents are trivial and occur at home. The most frequent injuries among patients with epilepsy are contusions, wounds, fractures, abrasions and brain concussions. The standardised mortality ratio (SMR; the ratio of observed number of deaths in a population with epilepsy to that expected, based on age and sex-specific mortality rates in a reference population) in population-based studies of epilepsy is 2-3 compared to the general population. This increased mortality is largely related to the etiology of the epilepsy and is probably not influenced by the treatment of the epilepsy. On the other hand, most fatalities in patients with chronic, therapy resistant epilepsy seem to be seizure-related and often sudden unexpected deaths (SUDEP). The frequency of such seizure-related deaths is most likely to be reduced by intensified treatment aiming at early seizure control, although appropriate studies for definitive evidence are still lacking. Apparently, there is an increased rate of traffic accidents in drivers with epilepsy, even if population-based prospective data are lacking. Many of these accidents are seizure-related. Probably, the extent to which physicians report their patients with uncontrolled epilepsy to the authorities is too low, but this has not yet been explored. Moreover, the preventive measures in legislation may be ignored by many people with epilepsy.

Do antiepileptic drugs play a role in sudden unexpected death in epilepsy?

Sudden unexpected death in epilepsy (SUDEP) accounts for approximately 2% of deaths in population-based cohorts of epilepsy, and up to 25% of deaths in cohorts of more severe epilepsy. When it occurs, SUDEP usually follows a generalised tonic-clonic seizure. Unresponsiveness, apnoea, and cardiac arrest occur in SUDEP, rather than the typical gradual recovery. The great majority of tonic-clonic seizures occur without difficulty and how the rare seizure associated with SUDEP differs from others is unknown.Three mechanisms have been proposed for SUDEP: cardiac arrhythmia, neurogenic pulmonary oedema, and postictal suppression of brainstem respiratory centres leading to central apnoea. Recent studies have found that the incidence of SUDEP increases with the severity of epilepsy in the population studied. The duration of epilepsy, number of tonic-clonic seizures, mental retardation, and simultaneous treatment with more than two antiepileptic drugs are independent risk factors for SUDEP. Some studies have reported that carbamazepine use, carbamazepine toxicity, and frequent, rapid changes in carbamazepine levels, may be associated with SUDEP. Other evidence indicates that carbamazepine could potentially increase the risk for SUDEP by causing arrhythmia or by altering cardiac autonomic function. However, this evidence is tenuous and most studies have not found an association between the use of carbamazepine or any other individual antiepileptic drug and SUDEP. There is little information regarding antiepileptic drugs other than phenytoin and carbamazepine. The incidence of SUDEP with gabapentin, tiagabine, and lamotrigine clinical development programmes is in the range found in other populations with refractory epilepsy. This suggests that these individual antiepileptic drugs are no more likely to cause SUDEP than antiepileptic drugs in general. Best current evidence indicates that the risk of SUDEP can be decreased by aggressive treatment of tonic-clonic seizures with as few antiepileptic drugs as necessary to achieve complete control. At present there is no strong reason to avoid any particular antiepileptic drug. Further studies are needed to elucidate the potential role of individual antiepileptic drugs in SUDEP and establish clinical relevance, if any. These studies may be challenging to conduct and interpret because SUDEP is relatively uncommon and large numbers will be necessary to narrow confidence intervals to determine the clinical relevance. Also adjustments will be needed to account for the potent risks associated with other independent factors.

Carbamazepine affects autonomic cardiac control in patients with newly diagnosed epilepsy

Previous studies indicate that epilepsy patients may have impaired autonomic cardiovascular control in the interictal state although it is unclear whether the observed reduction in cardiovascular responses is due to the epilepsy and the interictal epileptogenic discharges, or to the treatment with antiepileptic drugs. Spectral analysis of heart rate variability makes it possible to partly separate the sympathetic components, low frequency (LF), from the vagal components, high frequency (HF) of autonomic cardiac control. We used spectral analysis of heart rate variability to assess the effect of carbamazepine (CBZ) on autonomic cardiac control in patients with newly diagnosed epilepsy. Fifteen adult outpatients with newly diagnosed seizures/epilepsy underwent 24 h ambulatory EKG recordings before and after commencement of CBZ treatment. Total power as well as low frequency (LF), very low frequency (VLF) and high frequency (HF) power in heart rate variability was calculated. When analysing the full 24 h recordings, patients had significantly lower standard deviation of RR-intervals (P=0.0015), total power (P=0.0010), LF (P=0.0002), VLF (P=0.0025) and HF (P=0.0139) during treatment with CBZ than before. The results were very similar for daytime and night time recordings. Our observations demonstrate that CBZ may suppress both parasympathetic and sympathetic functions in newly diagnosed patients with epilepsy. The possible implications of our results for sudden unexpected death in epilepsy are discussed.

Heart rate variability during interictal epileptiform discharges

RATIONALE

Seizures may produce a variety of autonomic alterations. These alterations may occur due to evoked autonomic reflexes or as a direct cortical effect on autonomic control. In animal studies, lock step phenomena of interictal discharges to autonomic output have been repeatedly documented. However, the association of interictal discharges and autonomic output is not as well established in humans.

METHODS

RR intervals timely locked to interictal epileptiform discharge (RR(n)) were compared to RR intervals immediately following (RR(n+1)) interictal discharges in 40 patients with focal onset epilepsy and low baseline heart beat variability.

RESULTS

In 20 patients with 200 left sided interictal epileptiform discharges, RR(n) shortened in 100 and prolonged in 31 when compared to RR(n+1) intervals. While in 20 patients with 200 right sided interictal epileptiform discharges RR(n) intervals shortened in 17 and prolonged in 116 (Chi square P<0.001). No consistent differences in RR(n) intervals variability between frontal versus temporal localization of the interictal discharges from the same side was found.

CONCLUSIONS

Interictal discharges, may influence autonomic control over the cardiac cycle and agree with animal studies. Further study of the relationship of interictal discharges to autonomic output is needed to delineate the potential lateralized influences over autonomic nervous system.

Decrease of sympathetic cardiovascular modulation after temporal lobe epilepsy surgery

In temporal lobe epilepsy (TLE), there is evidence of ictal and interictal autonomic dysregulation, predominantly with sympathetic overactivity. The effects of TLE surgery on autonomic cardiovascular control and on baroreflex sensitivity (BRS) have not been studied. To evaluate such effects, we monitored heart rate (HR), systolic blood pressure (BP(sys)) and respiration in 18 TLE patients 3-4 months before and after TLE surgery. We used Blackman-Tukey spectral analysis to assess sympathetic and parasympathetic modulation as powers of HR and BP(sys) oscillations in the low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, 0.15-0.5 Hz) bands. BRS was determined as the LF transfer function gain between BP and HR. After surgery, HR, BP(sys), respiration and HF powers remained unchanged, while LF powers of HR (1.57 +/- 1.54 bpm(2)) and BP(sys) (2.19 +/- 1.34 mmHg(2)) and BRS (0.68 +/- 0.31 bpm/mmHg) were smaller than pre-surgical LF powers of HR (3.87 +/- 3.26 bpm(2)) and BP(sys) (4.80 +/- 3.84 mmHg(2)) and BRS (1.12 +/- 0.39 bpm/mmHg; P < 0.05). After TLE surgery, there is a reduction of sympathetic cardiovascular modulation and BRS that might result from decreased influences of interictal epileptogenic discharges on brain areas involved in cardiovascular autonomic control. TLE surgery seems to stabilize the cardiovascular control in epilepsy patients by reducing the risk of sympathetically mediated tachyarrhythmias and excessive bradycardiac counter-regulation, both of which might be relevant for the pathophysiology of sudden unexpected death in epilepsy patients (SUDEP). Thus, TLE surgery might contribute to reducing the risk of SUDEP.

Clinical pharmacology: drugs as a benefit and/or risk in sudden unexpected death in epilepsy?

Death may be the consequence of natural or unnatural causes, such as accidents, homicide, and suicide, which have no relationship to the disease of epilepsy. Direct causes of death include status epilepticus, and indirect causes may be head trauma or drowning subsequent to a seizure. When death occurs suddenly and without explanation, the term sudden unexpected unexplained death is used. Unexplained is a term that clinicians and research scientists are working to clarify. Numerous preclinical animal studies have been conducted as models for sudden death and have led to clinical studies in persons with epilepsy. These studies show that sympathetic nerve stimulation, ouabain, or coronary occlusion increased temporal dispersion of recovery of ventricular excitability and led to an underlying electrical instability that predisposed the ventricularmyocardium to arrhythmia. Cardiac arrhythmias in an animal model for ouabain-induced toxicity were associated with neural autonomic dysfunction. Neural discharges were characterized by increases, decreases, or no change in the discharge of postganglionic cardiac sympathetic nerves monitored simultaneously, predisposing to cardiac arrhythmia. Stimulation of the sympathetic ventrolateral cardiac nerve produced a shift in the origin of the pacemaker and tachyarrhythmias because the nerve is not uniformly distributed to the various regions of the heart but is localized to the atrioventricular junctional and ventricular regions. Such nonuniform distribution of sympathetic nerves would also contribute to initiation of arrhythmia as a nonuniform neural discharge occurred. Studies examining the physiology and pharmacology of this finding in multiple animal models found that subconvulsant, interictal discharge was associated with autonomic cardiac neural non-uniform discharge and cardiac arrhythmias. As a result of further investigations, Lathers and Schraeder edited a book in 1990 that summarized the clinical problem of sudden unexpected death and epilepsy (SUDEP). The contributors concluded that there was a paucity of clinical data addressing the mechanism of death. Regulatory response resulting from the consequent increased awareness of SUDEP occurred in 1993, when the FDA focused attention of practitioners and pharmaceutical manufacturers on the question of whether use of anticonvulsant drugs contributes to or prevents sudden unexpected death in epileptic persons. The FDA-convened panel of scientists considered the prevalence of sudden unexpected death in patients involved in studies associated with developing new anticonvulsant drugs and reviewed data on the risk of sudden unexpected death in patients taking lamotrigine. The risk of SUDEP was no different from thatfound in the young epilepsy population in general. Estimated SUDEP rates in patients receiving the new anticonvulsant drugs lamotrigine, gabapentin, topiramate, tigabine, and zonisamide were found to be similar to those in patients receiving standard anticonvulsant drugs, suggesting that SUDEP rates reflect population rates and not a specific drug effect. The FDA required warning labels on the risk of SUDEP in association with the use of each of the above-mentioned drugs. Another effect of bringing SUDEP to the attention of epilepsy researchers has been the expansion of basic science and the development of epidemiological and clinical studies directed at this phenomenon. Results from some of these studies are discussed in this article.

Heart rate dynamics in refractory and well controlled temporal lobe epilepsy

OBJECTIVES

Disorders of cardiovascular and other autonomic nervous system functions are often found in patients with temporal lobe epilepsy (TLE). Cardiovascular dysregulation in TLE has previously been quantified assessing traditional time and frequency domain measures of heart rate (HR) variability from short term ECG recordings. However, new complexity and fractal measures of HR variability based on non-linear dynamics and fractals ("chaos theory") may disclose certain patterns of HR dynamics that cannot be detected using only conventional measures.

METHODS

In addition to the traditional spectral and non-spectral components of HR variability, fractal correlation properties, approximate entropy (ApEn) of RR interval dynamics, and the slope of the power law relation were measured from 24 hour ambulatory ECG recordings to evaluate interictal autonomic cardiovascular regulatory function in 19 patients with refractory TLE, 25 patients with well controlled TLE, and in 34 healthy age and sex matched control subjects.

RESULTS

The traditional time and frequency domain measures were lower in patients with TLE than in controls (p<0.05). In addition, the power law slope (p<0.005) and ApEn (p<0.05) were also reduced in TLE patients. Furthermore, ApEn was smaller in patients with refractory TLE than in patients with well-controlled TLE ( p<0.01), whereas the long term fractal correlation value alpha2 was lower in patients with well controlled TLE (p<0.05). An altered HR variation was not associated with any particular AED regimen.

CONCLUSIONS

In addition to reduced overall HR variability, the long term fractal organisation and complexity of HR dynamics seem to be altered in TLE. These abnormalities in HR behaviour may partly contribute to the occurrence of adverse cardiovascular events, such as life threatening arrhythmias in patients with TLE.

Ictal tachycardia: its discriminating potential between temporal and extratemporal seizure foci

A wide variety of CNS lesions have been associated with changes in heart rate (HR). However, in epileptic patients their value to lateralize seizure onset remains controversial. This study aims to assess if HR changes associated with partial onset seizures could be useful in lateralizing seizure onset. We analysed HR changes on 100 seizures from 38 consecutive patients (mean age: 27.5 years) admitted for video-EEG telemetry monitoring. We evaluated the R-R interval 30 seconds before the seizure onset and 10, 20 and 120 seconds after the onset. We assessed whether there was a correlation between HR changes and seizure type, left/right differences and different semiological components for each seizure. We recorded 100 seizures. Three non-lateralized seizures were excluded from the analysis; 63/97 (65%) had left hemisphere onset, mainly from the temporal lobe (57.7%). The mean baseline HR was 77 beats per minute Ictal tachycardia (HR: > or = 107.06 beats per minute) was detected in 32 seizures, with ictal onset from the mesial temporal lobe structures in 23/32; 16/32 occurred during the first 10 seconds and 16/32 during the next 20 seconds from the seizure onset independently of the site of origin. Among the different semiological components for each seizure, only dystonic posturing and automatism correlated with HR increments. We did not find bradycardia in our series. Ictal tachycardia occurs most frequently with seizures arising from the mesial temporal lobe and it may not reliably predict the lateralization of seizure onset.

Antiepileptic drug therapy and its management in sudden unexpected death in epilepsy: a case-control study

PURPOSE

Because frequent seizures constitute a major risk factor for sudden unexpected death in epilepsy (SUDEP), the treatment with antiepileptic drugs (AEDs) may play a role for the occurrence of SUDEP. We used data from routine therapeutic drug monitoring (TDM) to study the association between various aspects of AED treatment and the risk of SUDEP.

METHODS

A nested case-control study was based on a cohort consisting of 6,880 patients registered in the Stockholm County In Ward Care Register with a diagnosis of epilepsy. Fifty-seven SUDEP cases, and 171 controls, living epilepsy patients, were selected from the cohort. Clinical data including data on TDM were collected through medical record review.

RESULTS

The relative risk (RR) of SUDEP was 3.7 (95% CI, 1.0-13.1) for outpatients who had no TDM compared with those who had one to three TDMs during the 2 years of observation. RR was 9.5 (1.4-66.0) if carbamazepine (CBZ) plasma levels at the last TDM were above and not within the common target range (20-40 microM). High CBZ levels were associated with a higher risk in patients receiving polytherapy and in those with frequent dose changes. Although the subgroup of patients with high CBZ levels was small (six cases of 33 with CBZ therapy), and the result should be interpreted with caution, no similar associations were demonstrated for phenytoin plasma levels and risk of SUDEP. No association was found between SUDEP risk and within-patient variation in AED levels over time.

CONCLUSIONS

Polytherapy, frequent dose changes, and high CBZ levels as identified risk factors for SUDEP all point to the risks associated with an unstable severe epilepsy. It is unclear whether high CBZ levels per se represent a risk factor or just reflect other unidentified aspects of a severe epilepsy. Our results, however, prompt further detailed analyses of the possible role of AEDs in SUDEP in larger cohorts and suggest that reasonable monitoring of the drug therapy may be useful to reduce risks.

[Bradycardia as an epileptic manifestation in temporal epilepsy: report of a case]

We describe a patient who had cardiac arrhythmia as epileptic manifestation. In a 34-year-old woman who had many episodes of loss of consciousness, the simultaneous ECG and video-EEG monitoring recorded bradycardia with a short episode of asystole (4 seconds) and left temporal rhythmic theta activity on EEG. MRI showed a small mass lesion in the left parahippocampal gyrus. Alterations in cardiac rhythm have been reported in epileptic seizures and tachycardia is the most common finding associated with them; bradyarrhythmia during seizures was uncommon. Many interconnections among insular cortex, limbic system and hypothalamus, may be responsible for vegetative manifestations in temporal lobe epilepsy.

Interictal cardiovascular autonomic responses in patients with temporal lobe epilepsy

PURPOSE

To measure interictal cardiovascular autonomic functions in patients with either refractory or well-controlled temporal lobe epilepsy (TLE).

METHODS

For autonomic assessment, heart rate variation during normal and deep breathing, Valsalva maneuver, and tilting were measured in 19 patients with chronic refractory TLE, 19 patients with well-controlled TLE, and 38 age- and sex-matched healthy control subjects. Blood pressure responses to tilting and isometric work also were evaluated.

RESULTS

Heart-rate (HR) variation during normal breathing (p = 0.006) and tilting (p = 0.043) was lower in patients with refractory TLE than in control subjects. Heart-rate response to tilting (p = 0.036) was also lower in patients with well-controlled TLE than in control subjects. Blood-pressure responses showed no differences between the patients and the control subjects. Patients taking carbamazepine (CBZ) medication had decreased HR responses to deep breathing (p = 0.046) and to tilting (p = 0.014) compared with the control subjects.

CONCLUSIONS

Refractory TLE seems to be associated with dysfunction of the cardiovascular autonomic regulation, manifesting as impaired HR responses to certain stimuli. Interictal autonomic dysfunction is seen in patients with well-controlled TLE as well, but it may be more evident in patients with refractory epilepsy. CBZ medication may also be associated with altered autonomic cardiac control.