Melatonin response in active epilepsy

Clocking Epilepsies: A Chronomodulated Strategy-Based Therapy for Rhythmic Seizures

Epilepsy is a neurological disorder characterized by hypersynchronous recurrent neuronal activities and seizures, as well as loss of muscular control and sometimes awareness. Clinically, seizures have been reported to display daily variations. Conversely, circadian misalignment and circadian clock gene variants contribute to epileptic pathogenesis. Elucidation of the genetic bases of epilepsy is of great importance because the genetic variability of the patients affects the efficacies of antiepileptic drugs (AEDs). For this narrative review, we compiled 661 epilepsy-related genes from the PHGKB and OMIM databases and classified them into 3 groups: driver genes, passenger genes, and undetermined genes. We discuss the potential roles of some epilepsy driver genes based on GO and KEGG analyses, the circadian rhythmicity of human and animal epilepsies, and the mutual effects between epilepsy and sleep. We review the advantages and challenges of rodents and zebrafish as animal models for epileptic studies. Finally, we posit chronomodulated strategy-based chronotherapy for rhythmic epilepsies, integrating several lines of investigation for unraveling circadian mechanisms underpinning epileptogenesis, chronopharmacokinetic and chronopharmacodynamic examinations of AEDs, as well as mathematical/computational modeling to help develop time-of-day-specific AED dosing schedules for rhythmic epilepsy patients.

Cycles in epilepsy

Epilepsy is among the most dynamic disorders in neurology. A canonical view holds that seizures, the characteristic sign of epilepsy, occur at random, but, for centuries, humans have looked for patterns of temporal organization in seizure occurrence. Observations that seizures are cyclical date back to antiquity, but recent technological advances have, for the first time, enabled cycles of seizure occurrence to be quantitatively characterized with direct brain recordings. Chronic recordings of brain activity in humans and in animals have yielded converging evidence for the existence of cycles of epileptic brain activity that operate over diverse timescales: daily (circadian), multi-day (multidien) and yearly (circannual). Here, we review this evidence, synthesizing data from historical observational studies, modern implanted devices, electronic seizure diaries and laboratory-based animal neurophysiology. We discuss advances in our understanding of the mechanistic underpinnings of these cycles and highlight the knowledge gaps that remain. The potential clinical applications of a knowledge of cycles in epilepsy, including seizure forecasting and chronotherapy, are discussed in the context of the emerging concept of seizure risk. In essence, this Review addresses the broad question of why seizures occur when they occur.

Decoding Circadian Rhythm and Epileptic Activities: Clues From Animal Studies

The relationship between circadian rhythm and epilepsy has been recognized for decades. Yet many questions underlying the complex mechanisms of their interaction remain elusive. A better understanding on this topic allows the development of accurate seizure-detection algorithm and alternative precise therapeutic strategies. Preclinical laboratory studies based on epileptic animal models, with controllable epileptogenic pathology and an array of intervention strategies, shed light on the bidirectional effects between circadian rhythm and epileptic seizures as well as their underlying mechanisms. Here, we reviewed findings on the interaction between circadian rhythm and epileptic seizures in the preclinical setting. We present the possible mechanisms at molecular, cellular and circuitry levels. We propose that future experimental designs should take into account the relationship between circadian rhythm and epilepsy as well as the underlying mechanisms in different types of animal models, which may have a translational significance as stepping stones for clinical benefits.

Levels of Melatonin in Continuous Spikes and Waves During Sleep

Levels of melatonin have been reported before in children with epilepsy, but such has not been reported to date in those with continuous spikes and waves during sleep. The aim of the present study was to assess serum melatonin levels and melatonin circadian rhythm in patients with continuous spikes and waves during sleep and epilepsy. Serum melatonin was measured in 39 children stratified into 3 groups. Group 1 included 15 patients with continuous spikes and waves during sleep, group 2 included 12 epilepsy patients, and group 3 included 12 controls, respectively. Blood samples were taken from all participants at 1:00 am and 9:00 am and melatonin levels were measured using a quantitative enzyme-linked immunosorbent assay test. The 9:00 am melatonin levels of group 1 were significantly decreased and pair groups were compared. The P_a value (representing a comparison between groups 1 and 2) was .002, the P_b value (representing a comparison between groups 1 and 3) was .001, and the P_c value (representing a comparison between groups 2 and 3) was .86. These findings suggest that the 9:00 am melatonin levels were significantly decreased in the comparison of groups 2 and 3. Further detailed research is necessary to determine the factors leading to the rapid decline of morning melatonin levels of children with continuous spikes and waves during sleep.

Melatonin and Angelman Syndrome: Implications and Mathematical Model of Diurnal Secretion

The main aim of the study was to compare the melatonin rhythms in subjects with Angelman syndrome (n = 9) and in children with (n = 80) and without (n = 40) epilepsy (nonepileptic patients diagnosed with peripheral nerve palsies, myopathy, and back pain) using our mathematical model of melatonin circadian secretion. The characteristics describing the diurnal hormone secretion such as minimum melatonin concentration, release amplitude, phase shift of melatonin release, and sleep duration as well as the dim light melatonin onset (DLMO) of melatonin secretion and the γ shape parameter allow analyzing the fit and deducing about how much the measured melatonin profile differs from a physiological bell-shaped secretion. The estimated sleep duration and phase shift of melatonin release as well as the DMLO offsets at 25% and 50% relative thresholds are the key characteristic of Angelman syndrome children. As revealed from the γ shape parameter, the melatonin secretion profiles are disturbed in majority of the AG subjects revealing rather a triangular course instead of the bell-like one.

Melatonin in Tuberous Sclerosis Complex Analysis Using Modern Mathematical Modeling Methods

Purpose. The aim of the study was to assess melatonin secretion pattern in children with TSC and to compare it with the secretion patterns in children with and without epilepsy. Material and Methods. Melatonin secretion was measured every three hours using the RIA method in four children with recognized TSC. The parameters of the melatonin secretion models were interpreted and compared with those obtained for the patients with epilepsy (n = 76) and the children from the control, nonepileptic group (n = 36). To describe the diurnal melatonin secretion, mathematical model was constructed and nonlinear least squares method with the Levenberg-Marquardt optimization algorithm was applied to approximate its parameters. The dim light melatonin onset (DLMO) parameters were also estimated from the model. Results and Conclusions. Statistically significant differences were found between the TSC melatonin secretion profiles and the nonepileptic control group. The profiles for the epileptic and TSC groups were found to be similar. For the TSC group, though a small one, the variations in the MLT release amplitudes seem to be independent of the total number of seizures; however, the MLT release shift appears to depend on the number of seizures.

Chronotype in patients with epilepsy: A controlled study in 60 subjects with late-onset focal epilepsy

Studies based on self-administered questionnaires indicate that most patients with epilepsy are morning-oriented. We aimed to investigate chronotype in patients with epilepsy with late-onset focal epilepsy by combining subjective data with dim light melatonin onset (DLMO) as an objective marker of the circadian phase. Sixty adult patients (mean age 46.5±13.8; 27 males) with late-onset focal epilepsy under pharmacological treatment were prospectively studied. Subjective chronotype was determined using the Morningness-Eveningness Questionnaire (MEQ) and circadian phase through analysis of salivary melatonin secretion, considering 3pg/ml as the dim light melatonin onset (DLMO) threshold. The mean MEQ score was significantly higher in the patients with epilepsy than in the controls, and significantly, more patients had a MEQ score indicative of the morning type (50.0% vs 30.0%, p=0.02). However, no significant differences were found in mean time of DLMO (21:38±01:21 vs 21:26±01:03; p=ns), and DLMO time was in the range indicative of an intermediate chronotype in both patients and controls. Sleep onset and sleep offset phase angles were significantly shorter in the patients. Patients whose global MEQ score identified them as morning types were significantly older than those with an intermediate or evening chronotype, and they had less social jet lag. No difference in epilepsy features and treatments was found between morning-oriented and nonmorning-oriented patients. Our analyses showed that the patients with epilepsy tended to be morning-oriented and to perceive themselves as morning types, even though this was not reflected in their DLMO values which did not differ significantly from those of controls and mostly fell within the intermediate chronotype range. Several factors may considerably influence subjective chronotype. We speculate that, in patients with epilepsy, the disease itself, prompting certain lifestyle choices, including a regular sleep schedule and early bedtime, may induce morning orientation and a morning-type self-perception.

Potential safety issues in the use of the hormone melatonin in paediatrics

Melatonin is a hormone produced by the pineal gland during the night in response to light/dark information received by the retina and its integration by the suprachiasmatic nucleus. When administered to selected populations of adults, in particular those displaying delayed sleep phase disorder, melatonin may advance the time of sleep onset. It is, however, being increasingly prescribed for children with sleep disorders despite the fact that (i) it is not registered for use in children anywhere in the world; (ii) it has not undergone the formal safety testing expected for a new drug, especially long-term safety in children; (iii) it is known to have profound effects on the reproductive systems of rodents, sheep and primates, as well as effects on the cardiovascular, immune and metabolic systems; and (iv) there is the potential for important interactions with drugs sometimes prescribed for children. In this review, I discuss properties of melatonin outside its ability to alter sleep timing that have been widely ignored but which raise questions about the safety of its use in infants and adolescents.

Circadian profile of salivary melatonin secretion and its concentration after epileptic seizure in patients with drug-resistant epilepsy--preliminary report

BACKGROUND

The results of a few previous studies assessing melatonin concentration in epileptic patient are ambiguous. This study aimed at: (1) comparing the circadian profile of salivary melatonin excretion in epileptic patients with that in healthy subjects and with circadian frequency profile of seizures and (2) assessing the effect of epileptic seizure upon salivary melatonin concentration.

METHODS

The study included thirty patients suffering from drug-resistant epilepsy aged from 22 to 45 years (mean age 37.17, SD ± 10.25). All subjects had their saliva taken in order to determine melatonin concentration and its circadian excretion profile performed every 4h. Additionally, saliva samples were collected in order to assess concentration of melatonin directly after epileptic seizure and 2h later.

RESULTS

The circadian profile of melatonin secretion in epileptic patients did not differ significantly from a profile in healthy subjects. Epileptic women showed statistically higher average salivary melatonin concentration at 2a.m., 6a.m. and 10a.m., compared to epileptic men; this may be related to lower age average of women as well as to their different hormonal profile.

CONCLUSION

The significantly higher salivary melatonin concentration at 6a.m. in patients with diurnal seizures (occurring mainly in the morning) may suggest proconvulsive effect of this hormone. Epileptic seizure did not lead to significantly elevated salivary melatonin concentration. Epileptogenic effect of melatonin might be corroborated by significantly elevated salivary melatonin levels directly after nocturnal tonic-clonic seizure which affected patients with highest concentration of this hormone at 2a.m. These observations would need confirmation based on studies of larger groups of epileptic patients.

Does melatonin affect epileptic seizures?

Melatonin is widely used for sleep disorders in patients with a range of developmental disorders and neurodisabilities, who also frequently have epilepsy. The aim of our review was to examine published data to assess the evidence for melatonin affecting seizure control. The literature search revealed 26 papers apparently reporting an association between melatonin and epilepsy or seizures but seven of these did not provide relevant information. Of the three double-blind, randomised, controlled trials, two showed no overall worsening or improvement in seizures, and one recent trial reported a statistically significant reduction in seizures. The open studies reported conflicting results. The few studies on the effect of seizures on melatonin levels have reported that baseline melatonin levels may be low in patients with uncontrolled epilepsy and that levels increase markedly following seizures. The striking finding of this review is the paucity of relevant data from the remarkably small number of studies. These results allow no firm conclusions to be drawn, although it would seem reasonable to observe that there was no marked overall effect on seizures, neither improvement nor worsening. There is a need for large, well designed, randomised, double-blind, placebo-controlled trials to establish the role of melatonin in either predisposing to or decreasing the likelihood of seizures.

Potency of melatonin in living beings

Living beings are surrounded by various changes exhibiting periodical rhythms in environment. The environmental changes are imprinted in organisms in various pattern. The phenomena are believed to match the external signal with organisms in order to increase their survival rate. The signals are categorized into circadian, seasonal, and annual cycles. Among the cycles, the circadian rhythm is regarded as the most important factor because its periodicity is in harmony with the levels of melatonin secreted from pineal gland. Melatonin is produced by the absence of light and its presence displays darkness. Melatonin plays various roles in creatures. Therefore, this review is to introduce the diverse potential ability of melatonin in manifold aspects in living organism.

Phase shift in the 24-hour rhythm of hippocampal EEG spiking activity in a rat model of temporal lobe epilepsy

For over a century epileptic seizures have been known to cluster at specific times of the day. Recent studies have suggested that the circadian regulatory system may become permanently altered in epilepsy, but little is known about how this affects neural activity and the daily pattern of seizures. To investigate, we tracked long-term changes in the rate of spontaneous hippocampal EEG spikes (SPKs) in a rat model of temporal lobe epilepsy. In healthy animals, SPKs oscillated with near 24-h period; however, after injury by status epilepticus, a persistent phase shift of ∼12 h emerged in animals that later went on to develop chronic spontaneous seizures. Additional measurements showed that global 24-h rhythms, including core body temperature and theta state transitions, did not phase shift. Instead, we hypothesized that locally impaired circadian input to the hippocampus might be responsible for the SPK phase shift. This was investigated with a biophysical computer model in which we showed that subtle changes in the relative strengths of circadian input could produce a phase shift in hippocampal neural activity. MRI provided evidence that the medial septum, a putative circadian relay center for the hippocampus, exhibits signs of damage and therefore could contribute to local circadian impairment. Our results suggest that balanced circadian input is critical to maintaining natural circadian phase in the hippocampus and that damage to circadian relay centers, such as the medial septum, may disrupt this balance. We conclude by discussing how abnormal circadian regulation may contribute to the daily rhythms of epileptic seizures and related cognitive dysfunction.

Prophylactic treatment with melatonin after status epilepticus: effects on epileptogenesis, neuronal damage, and behavioral changes in a kainate model of temporal lobe epilepsy

Melatonin is a potent antioxidant which showed anticonvulsant activities both in experimental and clinical studies. In the present study, we examined the effect of melatonin treatment (10mg/kg/day, diluted in drinking water, 8 weeks) during epileptogenesis on the consequences of a kainate (KA)-induced status epilepticus (SE) in rats. Melatonin increased the latency in the appearance of spontaneous recurrent seizures (SRSs) and decreased their frequency only during the treatment period. The behavioral alterations associated with hyperactivity, depression-like behavior during the light phase, and deficits in hippocampus-dependent working memory were positively affected by melatonin treatment in rats with epilepsy. Melatonin reduced the neuronal damage in the CA1 area of the hippocampus and piriform cortex and recovered the decrease of hippocampal serotonin (5-HT) level in rats with epilepsy. Taken together, long-term melatonin treatment after SE was unable to suppress the development of epileptogenesis. However, it showed a potential in reducing some of the deleterious alterations that develop during the chronic epileptic state in a diurnal phase-dependent mode.

Melatonin secretion in children with epilepsy

This study examined melatonin (MLT) system in children with epilepsy. Diurnal patterns of salivary MLT, urinary metabolite 6-sulphatoxymelatonin, core body temperature, pulse and blood pressure were measured in 51 children with epilepsy (6.6-17.9 years) and 29 comparison children (5.5-17.3 years). The children with epilepsy preserved MLT and other circadian rhythms. In nine children with epilepsy (17.6%), peak salivary MLT concentrations were very high. There were no associations between MLT secretion/excretion parameters (diurnal profile, peak nocturnal concentrations, area under the time curve, duration of elevated concentrations, acrophase) and seizure characteristics (time, type of seizures, antiepileptic medications). The study observations are important for understanding of the MLT system in epilepsy and for exploring the potential for seizure treatment with melatonin.

Melatonin as add-on treatment for epilepsy

BACKGROUND

Epilepsy is one of the most common chronic neurologic disorders. Despite the plethora of antiepileptic drugs (AEDs) currently available, 30% of patients continue having seizures. This group of patients requires a more aggressive treatment, since monotherapy, the first choice scheme, fails to control seizures. Nevertheless, polytherapy often results in a number of unwanted effects, including neurologic disturbances (somnolence, ataxia, dizziness), psychiatric and behavioral symptoms, and metabolic alteration (osteoporosis, inducement or inhibition of hepatic enzymes, etc.). The need for better tolerated AEDs is even more urgent in this group of patients. Reports have suggested an antiepileptic role of melatonin with a good safety profile.

OBJECTIVES

To assess the efficacy and tolerability of melatonin as add-on treatment for epilepsy.

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register (May 2012), the Cochrane Central Register of Controlled Trials (CENTRAL Issue 4 of 12, The Cochrane Library 2012), and MEDLINE (1946 to April 2012). The bibliographies of any identified study were searched for further references. We handsearched selected journals and conference proceedings. No language restrictions were imposed. In addition, we contacted melatonin manufacturers (i.e. Nathura) and original investigators to identify any unpublished study.

SELECTION CRITERIA

Randomized controlled trials; double, single, or unblinded trials; parallel group or cross-over studies. People with epilepsy regardless of age and sex, including children and adults with disabilities. Administration of melatonin as add-on treatment to any AED(s) compared to add-on placebo or no add-on treatment.

DATA COLLECTION AND ANALYSIS

Review authors independently selected trials for inclusion according to predefined criteria, extracted relevant data, and evaluated the methodologic quality of trials. The following outcomes were assessed: at least 50% seizure reduction, seizure freedom, adverse events, and quality of life.

MAIN RESULTS

Four publications, with a total of 102 participants (90 aged under 18 years), were included. Two different comparisons were available: 1. melatonin versus placebo and 2. melatonin 5 mg versus melatonin 10 mg. Despite our primary intention, due to insufficient information on outcomes, we were unable to perform any meta-analysis, but summarized data narratively. Two studies were randomized, double-blind, cross-over, placebo-controlled trials and two were randomized, double-blind, parallel, placebo-controlled trials. Only one study provided the exact number of seizures during the trial compared to the baseline: none of the patients with seizures during the trial had a change in seizure frequency compared with the baseline. Adverse events were systematically evaluated in only one study (no adverse events observed). Only one study systematically evaluated quality of life, showing no statistically significant improvement in quality of life in the add-on melatonin group.

AUTHORS' CONCLUSIONS

Included studies were of poor methodologic quality, and did not systematically evaluate seizure frequency and adverse events, so that it was impossible to summarize data in a meta-analysis. It is not possible to draw any conclusion about the role of melatonin in reducing seizure frequency or improving quality of life in patients with epilepsy.

The interaction of melatonin and agmatine on pentylenetetrazole-induced seizure threshold in mice

Melatonin, the major hormone produced by the pineal gland, has a number of functions in mammals, for example, its function as an anticonvulsant. Agmatine, a biogenic amine formed by decarboxylation of L-arginine by arginine decarboxylase, also has anticonvulsant effects. This study investigated the effect of the interaction of melatonin and agmatine on seizure susceptibility in the mouse model of pentylenetetrazole (PTZ)-induced clonic seizures. Further, the researchers investigated the involvement of melatonin receptors in this interaction using luzindole, a ML(1/2) receptor antagonist and prazosin, a ML(3) receptor antagonist. Melatonin, at 40 and 80 mg/kg, and agmatine, at 10 and 20mg/kg, exerted anticonvulsant effects. Luzindole, at 1.25 and 2.5mg/kg, or prazosin, at 0.5mg/kg, did not change the seizure threshold as compared with that of vehicle-treated mice. The anticonvulsant effect of melatonin (40 and 80 mg/kg) was prevented by luzindole (2.5mg/kg) (P<0.001) but not prazosin (0.5mg/kg), indicating the possible involvement of ML(1/2) receptors in the anticonvulsant effect of melatonin. Agmatine (5mg/kg) significantly increased the anticonvulsant effect of both the noneffective dose (20mg/kg) (P<0.05) and the effective dose (80 mg/kg) (P<0.001) of melatonin. Luzindole (2.5mg/kg), but not prazosin (0.5mg/kg), decreased the anticonvulsant effect of agmatine (20mg/kg) (P<0.05). Luzindole (2.5mg/kg), but not prazosin (0.5mg/kg), also decreased the seizure threshold when agmatine (5mg/kg) was administered before melatonin (20mg/kg); the decrease was significant compared with that of the group that received only agmatine and melatonin (P<0.001). In conclusion, melatonin and agmatine exhibit an additive effect in decreasing pentylenetetrazole-induced seizure threshold in mice, probably through ML(1/2) receptors.

Herbs in epilepsy: evidence for efficacy, toxicity, and interactions

Herbs and dietary supplements enjoy widespread use in the treatment of epilepsy although supportive data yielding efficacy and safety are lacking. Ten specific products, American hellebore, betony, blue cohosh, kava, mistletoe, mugwort, pipsissiwa, skullcap, valerian, and melatonin, have either multiple-cited recommendations for use in epilepsy or a rationale for antiepileptic action and are discussed in detail. These items paradoxically often have a proconvulsant effect in addition to potentially serious adverse effects. Herb-drug interactions also occur at the level of the P450 hepatic enzyme system of drug catabolism and the P-glycoprotein transport system regulating the entry of exogenous compounds into the vasculature or blood-brain barrier. Thus, significant pharmacokinetic interactions may occur, in addition to pharmacodynamic interactions and proconvulsant effects of alternative medications themselves. Patients should be inquired as to the nature of any alternative medicine products they are using, with the view that these products may be reasonable if traditional antiepileptic drug therapy is continued, potential adverse effects of the alternative agents are monitored, and the alternative and traditional agents do not conflict.

Melatonin in experimental seizures and epilepsy

Although melatonin is approved only for the treatment of jet-lag syndrome and some types of insomnia, clinical data suggest that it is effective in the adjunctive therapy of osteoporosis, cataract, sepsis, neurodegenerative diseases, hypertension, and even cancer. Melatonin also modulates the electrical activity of neurons by reducing glutamatergic and enhancing GABA-ergic neurotransmission. The indoleamine may also be metabolized to kynurenic acid, an endogenous anticonvulsant. Finally, the hormone and its metabolites act as free radical scavengers and antioxidants. The vast majority of experimental data indicates anticonvulsant properties of the hormone. Melatonin inhibited audiogenic and electrical seizures, as well as reduced convulsions induced by pentetrazole, pilocarpine, L-cysteine and kainate. Only a few studies have shown direct or indirect proconvulsant effects of melatonin. For instance, melatonin enhanced low Mg2+-induced epileptiform activity in the hippocampus, whereas melatonin antagonists delayed the onset of pilocarpine-induced seizures. However, the relatively high doses of melatonin required to inhibit experimental seizures can induce some undesired effects (e.g., cognitive and motor impairment and decreased body temperature). In humans, melatonin may attenuate seizures, and it is most effective in the treatment of juvenile intractable epilepsy. Its additional benefits include improved physical, emotional, cognitive, and social functions. On the other hand, melatonin has been shown to induce electroencephalographic abnormalities in patients with temporal lobe epilepsy and increase seizure activity in neurologically disabled children. The hormone showed very low toxicity in clinical practice. The reported adverse effects (nightmares, hypotension, and sleep disorders) were rare and mild. However, more placebo-controlled, double-blind randomized clinical trials are needed to establish the usefulness of melatonin in the adjunctive treatment of epilepsy.

Melatonin in epilepsy and febrile seizures

A study on melatonin rhythm in children with generalized idiopathic epilepsy and simple fever is presented in this article. A population of 40 children was divided into 4 groups, namely, epilepsy, febrile seizure, and 2 control groups. Salivary melatonin was measured by means of radioimmunoassay. Friedman 2-way analysis of variance (ANOVA) and Wilcoxon tests were employed to assess the existence of melatonin rhythm. Comparison across groups was performed by means of ANOVA and Mann-Whitney tests. Higher melatonin levels were found at night, with a peak at 04:00 h in all groups. Significant diurnal rhythm was also detected for these levels. No significant overall differences between case and control groups were found for melatonin levels, though patients showed lower peak melatonin values than controls at 04:00 h with a significant difference in the febrile seizure group (10.70 vs 19.5 pg/mL respectively; P<.04). Our data support the presence of diurnal rhythm in blood melatonin concentrations in children with epileptic and febrile seizures. Comparison between case and control groups showed lower peak concentrations in the febrile seizure group with respect to healthy controls.

Urinary 6‐hydroxymelatonin sulfate excretion in intellectually disabled subjects with sleep disorders and multiple medications: Validation of measurements in urine extracted from diapers

The aim of this study was to examine the applicability of urinary 6-hydroxymelatonin sulfate (MT6s) measurements in the evaluation of melatonin secretion in intellectually disabled patients with sleep disorders. All 17 patients received drugs with potential interactions with melatonin metabolism. Serum melatonin 24-h profiles were determined at hourly intervals. The area under the curve (AUC) value, peak amplitude, half-rise time, and half-decline time were calculated individually. Urinary MT6s excretion was determined from samples collected from disposable diapers during three consecutive days at varying intervals. The average excretion rate for each hour of the day was calculated. The excretion profiles were characterized by total amount of MT6s excretion/24 h/kg body mass, amount of excreted MT6s during 6 h of maximum excretion (MAX 6h), and start time of the maximum excretion (start MAX 6h). There were significant positive correlations between serum melatonin AUC value and total excretion of MT6s/body mass, between serum melatonin amplitude and urinary MAX 6h, and between melatonin half-rise time and start MAX 6h; one patient on phenobarbital medication was out of line. The serum melatonin profiles of the patients were classified by comparing them with those of matched healthy volunteers (low-, normal-, or high secretors, normal or delayed rhythm). Similarly, the parameters of MT6s profiles were compared with those obtained from healthy controls, and the patients were reclassified as normal or aberrant. The classifications based on serum melatonin and urinary MT6s measurements were mostly concordant. The daily pattern of urinary MT6s excretion reliably reflected the phase of the serum melatonin rhythm irrespective of the medications, but in some cases, the total amount of excreted MT6s was lower than expected based on serum melatonin measurements.

Ketogenic diet treatment abolishes seizure periodicity and improves diurnal rhythmicity in epileptic Kcna1-null mice

INTRODUCTION

Seizures are known to perturb circadian rhythms in humans as well as in animal models of epilepsy. However, it is unknown whether treatment of the underlying epilepsy restores normal biologic rhythms. We asked whether: (1) seizure activity is characterized by diurnal rhythmicity, (2) chronically epileptic mice exhibit impaired rest-activity rhythms, and (3) treatment with the anticonvulsant ketogenic diet (KD) improves such perturbations.

METHODS

Chronically epileptic Kcna1-null mice were fed either a standard diet (SD) or KD for 4 weeks and subjected to continuous video-EEG (electroencephalography) and actigraphy monitoring for 3-5 days to assess seizure activity and rest-activity cycles.

RESULTS

Seizure activity in Kcna1-null mice demonstrated diurnal rhythmicity, peaking at zeitgeber (ZT)2.30 +/- 1.52. Rest-activity rhythms of epileptic mice were significantly disrupted. Whereas locomotor activity for wild-type mice peaked at ZT15.45 +/- 0.28 (ZT14:26-ZT16:51), peak activity of epileptic mice was more unpredictable, occurring over a 12.4 h range (ZT06:33-ZT18:57). In six of nine epileptic mice, peak activity was delayed to ZT17.42 +/- 0.38, whereas peak activity was advanced to ZT10.00 +/- 1.26 in the remaining mice. Treatment with the KD abolished seizure periodicity and restored the rest-activity rhythm to values resembling those of wild-type mice (i.e., activity peaking at ZT16.73 +/- 0.67).

CONCLUSIONS

Kcna1-null mice experience seizures with 24-h periodicity and impaired circadian behavior. KD reduces the number and periodicity of seizures and restores normal behavioral rhythms, suggesting that this nonpharmacologic therapy may benefit biologic rhythm disturbances in epileptic patients.

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.

A single generalized seizure alters the amplitude, but not phase, of the circadian activity rhythm of the hamster

People with epilepsy exhibit high rates of sleep disturbances. In many cases, these sleep disruptions appear to be related to the occurrence of the seizures themselves. Changes in sleep structure may reflect underlying changes in the circadian clock, as circadian rhythms of locomotor activity, body temperature, and hormone release are disrupted following a seizure. The present study was designed to determine if a single generalized seizure could alter the phase and waveform of the circadian rhythm of wheel-running behavior in the Syrian hamster. Animals were housed in constant darkness, and were administered either a sham treatment or a maximal electroconvulsive shock at one of three time-points: 6 h before activity onset, 1 h after activity onset, or 6 h after activity onset. Seizures at all of these phases did not significantly affect the phase of the circadian activity rhythm. The circadian locomotor activity levels were significantly attenuated following seizures at all three phases. This attenuation was prominent over the 24 h following the seizure, and was also evident over the three post-seizure days. These data suggest that while seizures do not affect phase, they may alter the amplitude of the circadian clock. Because the amplitude of the circadian clock affects sleep quality, these findings suggest one mechanism by which persistent seizures may decrease the quality of sleep in patients with epilepsy.

Moonstruck? The effect of the lunar cycle on seizures

Recent reports on the effects of the lunar cycle on seizure occurrence have yielded mixed results. If the moon phase is influential, we hypothesized that this would be due to the moon's contribution to nocturnal illumination, rather than its waxing or waning state, and that significant correlations would not be apparent if local cloud cover were controlled for. We found a significant negative correlation between the mean number of seizures and the fraction of the moon illuminated by the sun (rho=-0.09, P<0.05) in 1571 seizures recorded in a dedicated epilepsy inpatient unit over 341 days. This correlation disappeared when we controlled for the local clarity of the night sky, suggesting that it is the brightness of the night and the contribution the moon phase makes to nocturnal luminance, rather than the moon phase per se, that may influence the occurrence of epileptic seizures.

How to assess circadian rhythm in humans: a review of literature

It is well known that seizures of some types of epilepsy tend to occur in patterns. The circadian rhythm may play a significant role in this phenomenon. In animal studies it has been found that seizures in experimental partial epilepsy are probably under the influence of the biological clock. In this review an introduction to the influence of the human circadian rhythm in epilepsy is given. Furthermore, the methodology of measuring the circadian rhythm in humans is explored. An overview of widely used methods includes protocols used to desynchronize circadian rhythm, and sleep-wake and biological markers such as the dim light melatonin onset, core body temperature, and cortisol that are employed to determine the phase of the circadian rhythm. Finally, the use of sleep parameters, actigraphy, and questionnaires is discussed. These are also important in assessment of the circadian rhythm.

Melatonin enhances the anticonvulsant and proconvulsant effects of morphine in mice: Role for nitric oxide signaling pathway

Melatonin has different interactions with opioids including enhancing their analgesic effect and reversal of opioid tolerance and dependence. Opioids are known to exert dose-dependent anti- and proconvulsant effects in different experimental seizure paradigms. This study investigated the effect of melatonin on biphasic modulation of seizure susceptibility by morphine, in mouse model of pentylenetetrazole (PTZ)-induced clonic seizures. We further investigated the involvement of the nitric oxidergic pathway in this interaction, using a nitric oxide synthase inhibitor, NG-nitro-L-arginine-methyl-ester (L-NAME). Melatonin exerted anticonvulsant effect with doses as high as 40-80 mg/kg, but with a dose far bellow that amount (10 mg/kg), it potentiated both the anticonvulsant and proconvulsant effects of morphine on the PTZ-induced clonic seizures. Possible pharmacokinetic interaction of melatonin and morphine cannot be ruled out in the enhancement of two opposing effects of morphine on seizure threshold. L-NAME (1 mg/kg) reversed the anticonvulsant property of the combination of melatonin (10 mg/kg) plus morphine (0.5 mg/kg). Moreover, L-NAME (5 mg/kg) blocked the enhancing effect of melatonin (10 mg/kg) on proconvulsant activity of morphine (60 mg/kg). Our results indicate that co-administration of melatonin enhances both anti- and proconvulsant effects of morphine via a mechanism that may involve the nitric oxidergic pathway.

Daily rhythms of seizure activity and behavior in a model of atypical absence epilepsy

We studied daily rhythms of chronic seizure activity and behavior in adult rats and mice treated with the cholesterol biosynthesis inhibitor AY-9944 (AY) during early postnatal development. Chronic atypical absence seizures were verified in the AY-treated animals by the presence of spontaneous 5- to 6-Hz slow spike-wave discharges (SSWDs) in the neocortex. General behavioral activity, as measured by total movements (TM), movement time (MT), ambulatory movement time (AMT), time spent in center of arena (CT), jumps (JFP), and rotational behavior (TURNS), were continuously recorded under a 12-hour light:12-hour dark photocycle. The average SSWD duration in AY-treated rats varied daily, with two peaks occurring at approximately dark phase and light phase onset. Mice treated with AY exhibited significant increases in all behavioral measures during the light and dark phases, with the exception of light-phase CT, which did not differ from that of controls. Consequently, the daily rhythm of total behavioral activity (TM) exhibited a significantly higher mean oscillation (mesor) and amplitude without evidence of phase shift compared with the TM rhythm of controls. The occurrence of SSWD activity in the AY model appears to be subject to regulation by biological timing mechanisms and, furthermore, associated with motor hyperactivity that does not alter the timing of behavioral rhythmicity.

Sleep and epilepsy: what we know, don't know, and need to know

Long-term video-EEG and, more recently, video-polysomnography, have provided the means to confirm and expand on the interconnections between sleep and epilepsy. Some of these relationships have become firmly established. When one of the authors (N.F.S.) presented part of this paper at a symposium on the Future of Sleep in Neurology at an American Clinical Neurophysiology Society annual meeting in 2004, the purpose was to summarize what we know, don't know, and need to know about the effects of sleep on epilepsy and epilepsy on sleep. Here we seek to summarize some of the more firmly established relationships between sleep and epilepsy and identify intriguing associations that require further elucidation.

A comparison of the circadian rhythms and the levels of melatonin in patients with diurnal and nocturnal complex partial seizures

The aim of the present work was to assess serum melatonin levels and melatonin circadian rhythm in patients with diurnal and nocturnal complex partial epilepsy. Daily rhythms of melatonin were studied in patients with diurnal complex partial epilepsy (n=10), patients with nocturnal complex partial epilepsy (n=10), and a control group (n=10). All patients were under carbamazepine treatment. Serum melatonin samples were taken at 1000, 2200, 0100, and 0500 hours. We found that melatonin circadian rhythm was normal in all patients when compared with controls. Melatonin levels were low in both patients with nocturnal and patients with diurnal complex partial epilepsy compared with the control group at 1000, 2200, 0100, and 0500 hours; a statistically significant decrease in melatonin levels was observed in the patients with epilepsy at 1000 hours only. These findings suggest that melatonin levels and circadian rhythm of melatonin do not differ between patients with nocturnal and patients with diurnal complex partial epilepsy. Further detailed research is necessary to determine the factors that govern the nocturnal or diurnal occurrence of complex partial seizures.

Involvement of nitric oxide pathway in the acute anticonvulsant effect of melatonin in mice

Melatonin, the major hormone produced by the pineal gland, is shown to have anticonvulsant effects. Nitric oxide (NO) is a known mediator in seizure susceptibility modulation. In the present study, the involvement of NO pathway in the anticonvulsant effect of melatonin in pentylenetetrazole (PTZ)-induced clonic seizures was investigated in mice. Acute intraperitoneal administration of melatonin (40 and 80 mg/kg) significantly increased the clonic seizure threshold induced by intravenous administration of PTZ. This effect was observed as soon as 1 min after injection and lasted for 30 min with a peak effect at 3 min after melatonin administration. Combination of per se non-effective doses of melatonin (10 and 20 mg/kg) and nitric oxide synthase (NOS) substrate L-arginine (30, 60 mg/kg) showed a significant anticonvulsant activity. This effect was reversed by NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg), implying an NO-dependent mechanism for melatonin effect. Pretreatment with L-NAME (30 mg/kg) and N(G)-nitro-L-arginine (L-NNA, 10 mg/kg) inhibited the anticonvulsant property of melatonin (40 and 80 mg/kg) and melatonin 40 mg/kg, respectively. Specific inducible NOS (iNOS) inhibitor aminoguanidine (100 and 300 mg/kg) did not affect the anticonvulsant effect of melatonin, excluding the role of iNOS in this phenomenon, while pretreatment of with 7-NI (50 mg/kg), a preferential neuronal NOS inhibitor, reversed this effect. The present data show an anticonvulsant effect for melatonin in i.v. PTZ seizure paradigm, which may be mediated via NO/L-arginine pathway by constitutively expressed NOS.

Sudden death in epileptic rats exposed to nocturnal magnetic fields that simulate the shape and the intensity of sudden changes in geomagnetic activity: an experiment in response to Schnabel, Beblo and May

To test the hypothesis that sudden unexplained death (SUD) in some epileptic patients is related to geomagnetic activity we exposed rats in which limbic epilepsy had been induced to experimentally produced magnetic fields designed to simulate sudden storm commencements (SSCs). Prior studies with rats had shown that sudden death in groups of rats in which epilepsy had been induced months earlier was associated with the occurrence of SSCs and increased geomagnetic activity during the previous night. Schnabel et al. [(2000) Neurology 54:903-908] found no relationship between SUD in human patients and geomagnetic activity. A total of 96 rats were exposed to either 500, 50, 10-40 nT or sham (less than 10 nT) magnetic fields for 6 min every hour between midnight and 0800 hours (local time) for three successive nights. The shape of the complex, amplitude-modulated magnetic fields simulated the shape and structure of an average SSC. The rats were then seized with lithium and pilocarpine and the mortality was monitored. Whereas 10% of the rats that had been exposed to the sham field died within 24 h, 60% of the rats that had been exposed to the experimental magnetic fields simulating natural geomagnetic activity died (P<.001) during this period. These results suggest that correlational analyses between SUD in epileptic patients and increased geomagnetic activity can be simulated experimentally in epileptic rats and that potential mechanisms might be testable directly.

Effect of melatonin dosage on sleep disorder in tuberous sclerosis complex

We report a randomized, double-blind, controlled, crossover trial investigating the response to oral melatonin using two dose regimens in patients with sleep disorders associated with tuberous sclerosis complex. Eight outpatients with tuberous sclerosis complex and sleep disorder received either 5 or 10 mg of melatonin. Sleep latency, total sleep time, number of awakenings, and seizure frequency were recorded in sleep and seizure diaries. No evidence of a dose effect between 5 and 10 mg was seen with respect to any outcome measure. (The 5 mg results are given first: sleep latency, 86 and 76 minutes; total sleep time, 8 hours, 57 minutes and 9 hours, 4 minutes; and sleep fragmentation, 0.8 and 1.0). This study might have missed a small beneficial effect of 10 mg melatonin. We propose that an initial trial of 5 mg melatonin is worth considering in patients with tuberous sclerosis complex and sleep disorder.

Changes in brain amino acids and nitric oxide after melatonin administration in rats with pentylenetetrazole-induced seizures

We examined the effect of melatonin on brain levels of amino acids and nitric oxide (NO) after pentylenetetrazole (PTZ)-induced seizures in rats. Animals were treated with melatonin (10-160 mg/kg, i.p.) 30 min before PTZ administration (100 mg/kg, s.c.), and were killed 3 hr later. At the dose of 80 mg/kg, melatonin significantly increased the latency (5.7-12.7 min) and decreased the duration (31.2-18.4 s) of the first seizure, reducing PTZ induced mortality from 87.5 to 25%. After kill, brains were removed and neurotransmitters and nitrite levels measured in prefrontal cortex (PF), parieto-temporal cortex (PF), striatum (ST), hippocampus (HP) and brain stem (BS) by high performance liquid chromatography. PTZ treatment increased glutamine levels in all brain areas studied, without changes in glutamate, gamma-amino butyric acid (GABA) and glycine. Aspartate and taurine increased in PF and PT and in HS and PT, respectively. Melatonin administration displayed a dose-dependent effect. At doses of 10-40 mg/kg, melatonin counteracted the PTZ-induced glutamine increase and reduced both glutamate and aspartate levels in the studied areas, with minor changes in GABA and glycine content. At doses of 80 and 160 mg/kg, the levels of glutamine, and glutamate, and to a lesser extent aspartate increased, whereas serine levels did not change. These two doses of melatonin also increased taurine, GABA and glycine in most brain areas studied. Treatment with melatonin (40-160 mg/kg) significantly decreased nitrite content in PT cortex, ST and BS areas of epileptic rats, without changes in the other brain regions. The results suggest that the anticonvulsant property of melatonin involves a modulation of both brain amino acids and NO production.

Temporal lobe seizures alter the amplitude and timing of rat behavioral rhythms

Daily rhythms of spontaneous locomotor activity (SLA) in rats were studied before and after an episode of pilocarpine-induced convulsive status epilepticus (SE). A pronounced increase in activity levels during both the light and dark phases was found 1 week after SE as compared with baseline SLA and controls administered saline. Rats with bilateral lesions of the nucleus accumbens (shell) did not exhibit any significant change in SLA 1 week after SE compared with controls. We suggest that during the first week after SE the increase in SLA was induced by abnormal neuronal activity in the hippocampus driving a descending limbic-motor pathway via the nucleus accumbens. EEG recordings revealed high-amplitude interictal spikes in hippocampal CA1. During subsequent weeks, SLA rhythms of nonlesioned chronic epileptic rats remained elevated but progressively normalized over a period of 12 weeks. Although both chronic epileptic and control groups displayed near-24-hour activity patterns under light-dark conditions, significant delays (>4 hour) in acrophase were observed after spontaneous seizures had developed. The phase delay was positively correlated with seizure history and likely the result of postictal hyperactivity associated with seizures during the normal rest period. Despite these changes, cell density in the suprachiasmatic nucleus (SCN) and intergeniculate leaflet (IGL) did not differ significantly between epileptic and control groups. In the absence of damage to brain areas directly involved with the regulation of behavioral rhythms, chronic seizure activity presumably alters the timing of activity patterns through a nonphotic mechanism, perhaps involving activation of the SCN or IGL during limbic seizures.

Circadian rhythms: interactions with seizures and epilepsy

Circadian rhythms are endogenously-mediated 24 h cycles of behavioral or physiological activity. The interactions among the mammalian circadian clock, acute seizures, and chronic epilepsy are not well-characterized. Evidence suggests that seizures are susceptible to circadian modulation, and that this modulation varies with epilepsy syndrome and location of seizure foci. The circadian timing system and secondary circadian cycles of hormone secretion, sleep and wakefulness, and recurrent environmental factors are discussed as potential systems that effect spontaneous seizure recurrence. Experimental designs should take into account time-of-day effects on seizure threshold and occurrence. Further work is required to determine what mechanisms account for daily variation in seizure susceptibility.

Circadian changes of heart rate in West syndrome

Patterns of circadian and ultradian rhythms in the heart rate (HR) are described in a full-term baby with birth asphyxia and convulsions. A 24h HR recording was carried out at the age of 1, 15, 56, 289, and 295 days; West syndrome diagnosis was made when the patient was 3 months old. The HR showed no circadian rhythm in the follow-up, whereas it is known that the circadian rhythm appears in healthy infants at the age of 1 month and remains thereafter. This observation may be an indirect indicator of the interference of West syndrome with centers of neurological maturity.

Hypothalamic neuronal loss and altered circadian rhythm of temperature in a rat model of mesial temporal lobe epilepsy

PURPOSE

Numerous dysfunctions in endogenous hypothalamic function have been associated with mesial temporal lobe epilepsy (MTLE). One endogenous activity is the circadian rhythm of temperature (CRT). In this study we examined whether hypothalamically mediated function is altered in the electrically induced, self-sustained, limbic status epilepticus model of MTLE. We then wished to determine whether there was a structural basis for regulatory alterations.

METHODS

We measured CRT with peritoneal temperature telemetry obtained in light-entrained (LD) and in free-running, constant-dark (DD) conditions. CRT from epileptic and controls of normal animals and kindled animals were quantized by fast Fourier transform-nonlinear least squares analysis to determine rhythmic complexity.

RESULTS

The circadian component of CRT was preserved in all animals. In DD, CRTs of epileptic animals were more complex than those of normal animals. CRT of kindled animals showed no increased complexity after electrically induced seizures. Neuronal density was decreased in regions of the anterior and posterior hypothalamus but not in the suprachiasmatic nuclei from the epileptic rats.

CONCLUSIONS

Alterations in CRT due to the epileptic state were independent of isolated seizures. Altered circadian thermoregulation in epileptic rats corresponded to regional hypothalamic neuronal loss. Structural changes of the hypothalamus may explain alterations in endogenous rhythms in MTLE.

Changes in human plasma melatonin profiles in response to 50 Hz magnetic field exposure

The effects of power-frequency magnetic fields on nighttime plasma melatonin were studied in a group of 30 adult male human subjects. Exposure consisted of 20 microT (200 mG) at 50 Hz (circularly polarized) at certain times in relation to the predicted time of onset of rise in melatonin concentration for a particular individual (the time of onset was predicted from a previous screening night). Response to this exposure was compared to sham-exposure (in random order). When exposure preceded onset of rise, a significant delay in onset time relative to sham-exposure of approximately half an hour was observed, with indications (marginally significant) of a reduction in maximum melatonin level. Analysis of distribution of time-delays is consistent with two populations: those individuals who respond (around 20%) and those that do not. Magnetic fields generated by square-wave currents produce more marked reductions in the maximum level when compared to sinusoidal waveforms, but there was no significant difference in onset time.

Disruption of light-induced c-Fos immunoreactivity in the suprachiasmatic nuclei of chronic epileptic rats

Photic stimulation during specific day periods may induce Fos oncoprotein expression within the ventrolateral part of the suprachiasmatic nucleus (SCN) in the hypothalamus of rodents. This phenomenon appears to be a major molecular mechanism for environmental light/dark cycle entrainment of the mammalian circadian clock. Light-dependent synchronization of circadian rhythmicity may be disrupted in epilepsy, a chronic neurological disorder often associated with chronobiological features such as seizure periodicity and disruption of endogenous biological rhythms. The present work examined the light-induced Fos protein expression on the SCN in the pilocarpine model of chronic epilepsy. Fos-like immunoreactivity was significantly reduced in the SCN of chronic epileptic rats after photic stimulation during the subjective night. These results indicate an altered Fos protein expression in the SCN of chronic epileptic rats. The present findings reveal that pathological neural events underlying epileptogenesis may disturb circadian rhythm regulation. The experimental study of circadian clock activity in the SCN may clarify the molecular bases of chronobiological disturbances in epilepsy.

The relationship between sleep and epilepsy in children

There is an intricate reciprocal relationship between epilepsy and sleep. The seizure threshold is often affected by changes in the level of arousal; certain seizure types occur predominantly or almost exclusively during sleep or upon awakening; many epileptiform electroencephalogram abnormalities are activated by sleep or sleep deprivation. Inversely, certain epilepsies are often associated with sleep disturbances, and epilepsy can affect sleep patterns and sleep architecture. Also, it may be difficult to differentiate certain nocturnal nonepileptic events from epileptic seizures occurring during sleep. Finally, antiepileptic drugs used in the treatment of sleep-related epilepsies can have an effect on sleep. The following is an analysis and review of these complex interactions between epilepsy and sleep.