Sex differences and lateral asymmetry in heart rate modulation in patients with temporal lobe epilepsy

Pre-ictal heart rate changes: A systematic review and meta-analysis

PURPOSE

To estimate the incidence of pre-ictal heart rate (HR) manifestations and to identify clinical and study-related factors modulating the estimate.

METHODS

We searched articles recording concurrent pre-ictal EEG and HR in adults and children with epilepsy. Pre-ictal HR changes were classified as HR reduction (HRR) or increase (HRI). Studies reporting the total number of seizures and the number of seizures with pre-ictal HR changes were included in a random-effects meta-analysis. A random-effects meta-regression was used to identify variables affecting study heterogeneity.

RESULTS

Thirty studies, including 1110 participants and 2957 seizures, were included. The meta-analysis showed a pooled incidence of pre-ictal HRI of 36/100 seizures (95% CI 22-50). The pre-ictal HRI incidence was 44/100 seizures (95% CI 33-55) in studies including temporal lobe epilepsy, 55/100 seizures (95% CI 41-68) in studies enrolling adults and 35/100 seizures (95% CI 16-58) when patients on antiepileptic drugs were included. The meta-regression showed that the age group, the length of the pre-ictal period, the incidence of ictal tachycardia and the time of onset of the pre-ictal HRI had a significant impact on estimates variability. The pooled incidence of pre-ictal HRR was 0/100 seizures (95% CI 0-1).

CONCLUSION

Review of bias evaluation and methods assessment disclosed several major limitations in the evidence-base. HR monitoring could be valuable to identify seizures prior to their apparent onset, opening the possibility to early interventions. Additional effort is necessary to delineate the target population who might benefit from its use and the mechanisms sustaining the pre-ictal cardiac changes.

Pupil-size asymmetry is a physiologic trait related to gender, attentional function, and personality

A small difference in the size of the two pupils is common in healthy individuals, a condition termed benign or physiologic anisocoria (BA). Past research indicates that BA is probably caused by asymmetry in sympathetic nervous system (SNS) function [e.g., Rosenberg (2008). Physiologic anisocoria: A manifestation of a physiologic sympathetic asymmetry. Neuro-Ophthalmology, 32, 147-149]. This study is the first to show that BA varies with psychological factors linked to brain asymmetry and autonomic arousal, including gender, attention, and personality. Males exhibited a more directional BA than females, consistent with greater hemispheric lateralization in males. BA also varied with a self-report measure of attentional function, consistent with evidence of hemispheric asymmetry in visuospatial attention networks. Finally, BA varied with personality traits linked to autonomic arousal. Individuals exhibiting higher Meanness and Boldness, and lower Empathy scores tended to show more directional BA. This link between personality traits and BA may be related to brain asymmetries in autonomic arousal and emotion-related processing. If future studies employing direct measures of lateralized brain activity confirm the link between BA and SNS asymmetries, this new metric may prove useful in discovering new relationships between brain organization and psychological function, and how these relationships vary across individuals.

A possible relationship between Takotsubo cardiomyopathy and female sex steroid-related modulation of functional cerebral asymmetry

Takotsubo cardiomyopathy (Tc) is a transient left ventricular apical ballooning syndrome, with symptoms and signs of acute myocardial infarction. Tc syndrome, which occurs predominantly in postmenopausal women, is characterized by increase of sympathetic activity. Studies on the gender-specific differences in sympatho-vagal regulation and functional cerebral asymmetry (FCA) imply that female pattern of dominance is characterized by the left hemisphere, which is believed to have parasympathetic predominance, whereas male pattern indicates dominance of the right hemisphere, which is believed to have sympathetic predominance. Fluctuating levels of female sex steroids are supposed to change FCA, modulating transcallosal inter-hemispheric inhibition across the menstrual cycle. The findings suggest that FCA is enhanced during the low steroid phase (menstrual phase), whereas, during high estrogen and/or progesterone phases (follicular and luteal phase) FCA is reduced. This theory is in line with concept of decreased magnitude of inter-hemispheric cortical lateralization in premenopausal women compared to men and postmenopausal women. Therefore, if postmenopausal women are more lateralized for a variety of cerebral functions, they have less balanced equilibrium between the right-sided sympathetic and left-sided parasympathetic predominance. Decrease of endogenous female sex steroid levels in postmenopausal women leads to reduced influence of estrogens to the left hemisphere, which is believed to have parasympathetic predominance. If both of these mechanisms result in sympatho-vagal imbalance, increasing sympathetic system activity in postmenopausal women, it seems reasonable why postmenopausal women became more susceptible to sympathetically-mediated syndromes such as Takotsubo cardiomyopathy.

Syncope, seizure-induced bradycardia and asystole: two cases and review of clinical and pathophysiological features

Episodes of transient loss of consciousness (TLOC) are commonly due to syncope or epileptic seizures. The distinction between both entities on clinical grounds and eyewitness accounts can be challenging and is often hampered by similar clinical features. We briefly summarize syncope-related symptoms and present the case of a female patient who suffered from TLOC episodes due to both reflex syncope and epileptic seizures. Seizure-induced syncope is a rare complication particularly of non-generalized temporal lobe seizures and may be suspected in people with epilepsy who report new semiological features with sudden onset of atonia, TLOC and seizure-related falls. We review epidemiological, clinical and electroencephalographic aspects of seizure-related asystole and syncope and discuss their clinical relevance. The implantation of a cardiac pacemaker appears to efficiently prevent seizure-related falls and consecutive injuries and is an important treatment option if full seizure-control cannot be achieved in these patients. We describe a second case of a patient with refractory temporal lobe epilepsy and seizure-related syncope which ceased after the implantation of a cardiac pacemaker.

Exercise-induced seizures and lateral asymmetry in patients with temporal lobe epilepsy

Objective

The objective of this case report is to better characterize the clinical features and potential pathophysiological mechanisms of exercise-induced seizures.

Methods

We report a case series of ten patients from a tertiary epilepsy center, where a clear history was obtained of physical exercise as a reproducible trigger for seizures.

Results

The precipitating type of exercise was quite specific for each patient, and various forms of exercise are described including running, swimming, playing netball, dancing, cycling, weight lifting, and martial arts. The level of physical exertion also correlated with the likelihood of seizure occurrence. All ten patients had temporal lobe abnormalities, with nine of the ten patients having isolated temporal lobe epilepsies, as supported by seizure semiology, EEG recordings, and both structural and functional imaging. Nine of the ten patients had seizures that were lateralized to the left (dominant) hemisphere. Five patients underwent surgical resection, with no successful long-term postoperative outcomes.

Conclusions

Exercise may be an underrecognized form of reflex epilepsy, which tended to be refractory to both medical and surgical interventions in our patients. Almost all patients in our cohort had seizures localizing to the left temporal lobe. We discuss potential mechanisms by which exercise may precipitate seizures, and its relevance regarding our understanding of temporal lobe epilepsy and lateralization of seizures. Recognition of, as well as advice regarding avoidance of, known triggers forms an important part of management of these patients.

Cardiac arrhythmias and ictal events within an epilepsy monitoring unit

The aim of this study was to determine the incidence and describe the factors influencing ictal cardiac arrhythmias in children with epilepsy. A 2-year review within a pediatric epilepsy monitoring unit revealed 2066 electrographically confirmed seizures in 139 patients. Demographic, seizure, and cardiac variables were collected for each patient. Fisher's exact test, Wilcoxon rank-sum test, and Spearman's rank correlation coefficient were used to identify significant differences and associations at the seizure and patient levels. In 244 seizures meeting inclusion criteria, ictal cardiac arrhythmias were seen in 45% of the seizures (40% of the patients). The most common arrhythmia was benign respiratory sinus arrhythmia (78% of seizures with arrhythmias, 70% of patients with arrhythmias). Potentially serious arrhythmias included irregular variable arrhythmias, and abnormal QRS intervals were seen in 12% of all the patients. In seizures with ictal arrhythmias, 64% occurred in male patients (P = 0.016) and 78% occurred in white patients (P = 0.013). This study estimates the incidence of ictal arrhythmias within the pediatric population that need further medical attention and management.

Peri-ictal vegetative symptoms in temporal lobe epilepsy

We investigated peri-ictal vegetative symptoms (PIVS) in 141 patients with adult temporal lobe epilepsy (TLE) and assessed frequency, gender effect, and lateralizing value of peri-ictal autonomic signs. We recorded abdominal auras in 62%, goosebumps in 3%, hypersalivation in 12%, spitting in 1%, cold shivering in 3%, urinary urge in 3%, water drinking in 7%, postictal nose wiping (PNW) in 44%, and postictal coughing in 16%. At least one vegetative sign appeared in 86% of the patients. The presence of PIVS did not have a significant lateralizing value. PNW occurred in 52% of women and in 33% of men, whereas any PIVS was present in 93% of women and 77% of men. In summary, contradictory to previous studies, the presence of PIVS has no lateralizing value, which may be linked to a low frequency of occurrence of PIVS. PIVS, especially PNW, occurred more frequently in women, supporting the gender differences in epilepsy.

Behavioural asymmetry is involved in regulation of autonomic processes: Left side presentation of food improves reproduction and lactation in cows

It is known that the right and left brain hemispheres differ in their ability to regulate autonomic processes in the organism. Direct unilateral stimulation of the brain provokes side-dependent endocrine, immune and other visceral reactions. Since brain hemispheres are mainly involved in the regulation of muscles and sensory organs on the contra lateral side of the body the activation of behavioural asymmetry stimulates the contra lateral half of the brain. The important theoretical and practical question of whether autonomic processes can be regulated via the behavioural asymmetry route remains unexplored. In this study, we report that the chronic presentation of an emotionally important stimulus-food-from the left side, improves reproductive performance in animals in a broad range of feeding conditions. The unilateral presentation of food can also influence lactation, but in this case the side-dependent effects are different under varying feeding conditions. This finding opens a simple practical approach to influence basic somatic functions in the organism.

Ictal heart rate increase precedes EEG discharge in drug-resistant mesial temporal lobe seizures

OBJECTIVE

Heart rate (HR) changes, mainly tachycardia, are often observed during seizures originating from the temporal lobe. The aim of this study was to analyze the role of ictal HR changes in localizing both mesial and lateral temporal lobe epilepsy (TLE) in a group of 68 patients. The influence of the gender and the side of epilepsy on HR modulation was also evaluated.

METHODS

Ictal HR was recorded during prolonged Video-EEG monitoring performed in 68 patients affected by drug-resistant TLE during a non-invasive pre-surgical protocol. According to the electro-clinical correlation, obtained by video-EEG monitoring, one hundred-thirteen seizures (n=113) and one hundred-forty-four auras (n=144) were identified and included in the study. Furthermore, the electro-clinical correlation allowed the classification of all the epileptic events (seizures and auras) as having mesial or lateral origin, based on the temporal lobe seizure onset zone. Ictal HR was calculated with respect to the R-R waves, and assessed from 15 sec (s) before (T(- 15)) to 15 s after (T(+15)) the time of EEG seizure onset (T(0)).

RESULTS

We observed a high incidence (92%) of ictal HR increase in TLE seizures. When the ictal EEG indicated a seizure onset from the mesial temporal structures, the onset of ictal HR increase preceded by about 5 s the EEG ictal onset (SD+/-18.4), whereas the onset of HR increase coincided with the onset of EEG discharges (SD+/-14.8) when the ictal EEG indicated the onset of seizures from the lateral temporal structures. No significant differences were found between male and female patients; and between right and left TLE.

CONCLUSIONS

Our findings show that ictal HR increase, preceding the onset of the EEG discharge, is associated with ictal EEG seizure pattern defining temporal lobe seizures originating from the mesial temporal lobe structures; this association suggests that the HR changes may be coupled to the functional impairment of neural circuits involved in sympathetic cardiovascular regulation, in the mesial temporal lobe structures. Further studies investigating the relationship between intracranial EEG monitoring and ECG recording are worthwhile, to confirm our results and to give further indications on the pathogenesis of ictal HR abnormalities.