Rapid eye movement sleep and hippocampal theta oscillations precede seizure onset in the tetanus toxin model of temporal lobe epilepsy.

Improved understanding of the interaction between state of vigilance (SOV) and seizure onset has therapeutic potential. Six rats received injections of tetanus toxin (TeTX) in the ventral hippocampus that resulted in chronic spontaneous seizures. The distribution of SOV before 486 seizures was analyzed for a total of 19 d of recording. Rapid eye movement sleep (REM) and exploratory wake, both of which express prominent hippocampal theta rhythm, preceded 47 and 34%, for a total of 81%, of all seizures. Nonrapid eye movement sleep (NREM) and nonexploratory wake, neither of which expresses prominent theta, preceded 6.8 and 13% of seizures. We demonstrate that identification of SOV yields significant differentiation of seizure susceptibilities, with the instantaneous seizure rate during REM nearly 10 times higher than baseline and the rate for NREM less than half of baseline. Survival analysis indicated a shorter duration of preseizure REM bouts, with a maximum transition to seizure at ∼90 s after the onset of REM. This study provides the first analysis of a correlation between SOV and seizure onset in the TeTX model of temporal lobe epilepsy, as well as the first demonstration that hippocampal theta rhythms associated with natural behavioral states can serve a seizure-promoting role. Our findings are in contrast with previous studies suggesting that the correlations between SOV and seizures are primarily governed by circadian oscillations and the notion that hippocampal theta rhythms inhibit seizures. The documentation of significant SOV-dependent seizure susceptibilities indicates the potential utility of SOV and its time course in seizure prediction and control.

Continuous brain tissue oxygenation monitoring in the management of pediatric stroke.

BACKGROUND: Direct invasive monitoring of brain tissue oxygenation (PbtO(2)) has been routinely utilized to predict cerebral ischemia and to prevent secondary injury in patients with traumatic brain injury (TBI) and vasospasm secondary to subarachnoid hemorrhage (SAH). The safety and utility of these devices in the pediatric population have been examined in a few small studies. No studies, however, have examined the use of PbtO(2) monitoring in stroke patients. METHODS: Retrospective chart review of the first two consecutive, critically ill pediatric patients in the pediatric intensive care unit requiring brain tissue oxygen monitoring for newly diagnosed cerebral ischemia. ICP, CPP, PbtO(2), SaO(2), BP, and RR were all continually monitored during their care and were retrospectively collected and reviewed. RESULTS: We present two pediatric stroke patients managed in a critical care setting with PbtO(2) monitoring in addition to ICP, MAP, CPP, and SaO(2). Both patients had multiple events of low brain tissue oxygen (PbtO(2) <20 torr), independent of abnormal values in other monitoring parameters, which required physician intervention. No new ischemic damage occurred after PbtO(2) monitoring began in either patient. CONCLUSIONS: There is currently inadequate data to support the application of PbtO(2) monitoring in children with stroke to prevent progressive ischemia and to improve outcome. However, the positive results for these two patients support the need for further study in this area.

Incidence of postoperative hyponatremia and complications in critically-ill children treated with hypotonic and normotonic solutions.

OBJECTIVE: To determine the incidence and clinical consequences of postoperative hyponatremia in children. STUDY DESIGN: We performed a retrospective analysis of postoperative admissions to the pediatric intensive care unit (excluding cardiac, neurosurgical, and renal). The incidence of severe (serum sodium < 125 mmol/L or symptoms) and moderate (serum sodium < 130 mmol/L) hyponatremia in children receiving hypotonic (HT) and normotonic (NT) fluids was calculated. RESULTS: Out of a total of 145 children (568 sodium measurements; 116 HT and 29 NT), we identified 16 with hyponatremia (11%). The incidences of moderate (10.3% vs 3.4%, P = .258) and severe (2.6% vs 0%; P = .881) hyponatremia were not significantly different in the HT and NT groups. There were no neurologic sequelae or deaths related to hyponatremia. CONCLUSIONS: In our study group, hyponatremia was common, but morbidity and death were not observed. Careful monitoring of serum sodium level may be responsible for this lack of adverse outcomes. Larger, prospective studies are needed to determine whether the incidence of hyponatremia differs between the HT and NT groups.

Fully optimized discrimination of physiological responses to auditory stimuli.

The use of multivariate measurements to characterize brain activity (electrical, magnetic, optical) is widespread. The most common approaches to reduce the complexity of such observations include principal and independent component analyses (PCA and ICA), which are not well suited for discrimination tasks. We addressed two questions: first, how do the neurophysiological responses to elongated phonemes relate to tone and phoneme responses in normal children, and, second, how discriminable are these responses. We employed fully optimized linear discrimination analysis to maximally separate the multi-electrode responses to tones and phonemes, and classified the response to elongated phonemes. We find that discrimination between tones and phonemes is dependent upon responses from associative regions of the brain apparently distinct from the primary sensory cortices typically emphasized by PCA or ICA, and that the neuronal correlates corresponding to elongated phonemes are highly variable in normal children (about half respond with neural correlates of tones and half as phonemes). Our approach is made feasible by the increase in computational power of ordinary personal computers and has significant advantages for a wide range of neuronal imaging modalities.

Parenting stress and childhood epilepsy: the impact of depression, learning, and seizure-related factors.

OBJECTIVE: The purpose of this study was to evaluate stress in parents of children with epilepsy relative to the impact of childhood depression, learning disorders, and seizure-related risk factors. METHODS: Sixty-five parents and their children completed the Parenting Stress Index, Child Depression Inventory, and behavior and demographic forms. Kruska-Wallis ANOVAs and Spearman's rank correlations were used in a cross-sectional study design. RESULTS: High levels of stress were found among the parents (45%). Overall, child depression (23%) was found to significantly increase the distress parents experienced in their role (P<0.05). Another risk factor found to impact parenting stress was learning disabilities (P<0.01). The seizure-related factors of polytherapy, duration, and age at onset were correlated with depression (P<0.05). CONCLUSION: To effectively manage children with epilepsy, assessments of depression and learning must be considered because of their potential impact on parenting stress and the child's overall quality of life.

Activating transcription factor 3 (ATF3) represses the expression of CCL4 in murine macrophages.

Acute expression of macrophage inflammatory protein-1 beta (also known as CCL4) promotes beneficial leukocyte recruitment to infected tissues, but chronic expression of this chemokine contributes to inflammatory disease. CCL4 expression is controlled largely at the transcriptional level and an ATF/CRE sequence located in the promoter (-104 to -97bp, relative to the transcriptional start site) has been identified as a critical cis-acting element. The trans-acting binding proteins that influence CCL4 transcription via this site are largely unknown. We investigated whether activating transcription factor 3 (ATF3), a member of the ATF/CREB family of transcription factors, binds to the CCL4 ATF/CRE site in macrophages. Using the electrophoretic mobility shift assay and the chromatin immunoprecipitation assay, we found that ATF3 binds to the ATF/CRE site within the CCL4 promoter in untreated and lipopolysaccharide (LPS)-stimulated macrophages. Quantitative RT-PCR analysis showed that CCL4 mRNA levels in elicited peritoneal macrophages from ATF3(-/-) mice are significantly higher than in congenic ATF3(+/+) macrophages under both unstimulated and LPS-stimulated conditions, suggesting that ATF3 represses transcription of the CCL4 gene. Consistent with the higher gene expression, ATF3-deficient macrophages secreted more CCL4 protein than ATF3(+/+) macrophages. Similar results were obtained in bone-marrow-derived macrophages treated with Toll-like receptor 2, 3, 4 and 5 agonists. Thus, we conclude that ATF3 constitutively binds to the ATF/CRE site in the CCL4 promoter where it represses basal and pathogen-associated molecular pattern (PAMP)-stimulated transcription. Consequently, ATF3 appears to be part of a control mechanism that limits the amount of CCL4 released by macrophages, preventing excessive inflammation.

Improved sleep-wake and behavior discrimination using MEMS accelerometers.

State of vigilance is determined by behavioral observations and electrophysiological activity. Here, we improve automatic state of vigilance discrimination by combining head acceleration with EEG measures. We incorporated biaxial dc-sensitive microelectromechanical system (MEMS) accelerometers into head-mounted preamplifiers in rodents. Epochs (15s) of behavioral video and EEG data formed training sets for the following states: Slow Wave Sleep, Rapid Eye Movement Sleep, Quiet Wakefulness, Feeding or Grooming, and Exploration. Multivariate linear discriminant analysis of EEG features with and without accelerometer features was used to classify behavioral state. A broad selection of EEG feature sets based on recent literature on state discrimination in rodents was tested. In all cases, inclusion of head acceleration significantly improved the discriminative capability. Our approach offers a novel methodology for determining the behavioral context of EEG in real time, and has potential application in automatic sleep-wake staging and in neural prosthetic applications for movement disorders and epileptic seizures.

The benefits of a camp designed for children with epilepsy: evaluating adaptive behaviors over 3 years.

OBJECTIVE: Children with epilepsy attending a condition-specific overnight camp were evaluated for behavioral changes over 3 consecutive years, using a modification of the Vineland Adaptive Behavioral Scale. METHODS: Trained counselors completed pre- and postcamp assessments for each camper. Repeated-measures MANOVA was used to analyze effects of the camp experience for each year, with respect to gender and age. Repeated-measures ANOVA was conducted to evaluate long-term effects from year-to-year comparisons for return campers, following three successive camp experiences. RESULTS: A significant change in social interaction was observed over 3 years. Despite some decline at the start of camp in consecutive years, the overall trend for return campers suggests a positive cumulative impact of continued camp participation, with improvements in the domains of social interaction, responsibility, and communication. CONCLUSION: A condition-specific camp designed for children with epilepsy can improve adaptive behaviors and social interactions. Overall net gains appear to increase over time, suggesting additional benefits for return campers.

A Murine Model to Study Epilepsy and SUDEP Induced by Malaria Infection.

One of the largest single sources of epilepsy in the world is produced as a neurological sequela in survivors of cerebral malaria. Nevertheless, the pathophysiological mechanisms of such epileptogenesis remain unknown and no adjunctive therapy during cerebral malaria has been shown to reduce the rate of subsequent epilepsy. There is no existing animal model of postmalarial epilepsy. In this technical report we demonstrate the first such animal models. These models were created from multiple mouse and parasite strain combinations, so that the epilepsy observed retained universality with respect to genetic background. We also discovered spontaneous sudden unexpected death in epilepsy (SUDEP) in two of our strain combinations. These models offer a platform to enable new preclinical research into mechanisms and prevention of epilepsy and SUDEP.

Multivariate linear discrimination of seizures.

OBJECTIVE: To discriminate seizures from interictal dynamics based on multivariate synchrony measures, and to identify dynamics of a pre-seizure state. METHODS: A linear discriminator was constructed from two different measures of synchronization: cross-correlation and phase synchronization. We applied this discriminator to a sequence of seizures recorded from the intracranial EEG of a patient monitored over 6 days. RESULTS: Surprisingly, we found that this bivariate measure of synchronization was not a reliable seizure discriminator for 7 of 9 seizures. Furthermore, the method did not appear to reliably detect a pre-seizure state. An association between anti-convulsant dosage, frequency of clinical seizures, and discriminator performance was noted. CONCLUSIONS: Using a bivariate measure of synchronization failed to reliably differentiate seizures from non-seizure periods in these data, nor did such methods show reliable detection of a synchronous pre-seizure state. The non-stationary variables of decreasing antiepileptic medication (without available serum concentration measurements), and concomitant increasing seizure frequency contributed to the difficulties in validating a seizure prediction tool on such data. SIGNIFICANCE: The finding that these seizures were not a simple reflection of increasing synchronization in the EEG has important implications. The non-stationary characteristics of human post-implantation intracranial EEG is an inherent limitation of pre-resection data sets.

Seizure entrainment with polarizing low-frequency electric fields in a chronic animal epilepsy model.

Neural activity can be modulated by applying a polarizing low-frequency (<<100 Hz) electric field (PLEF). Unlike conventional pulsed stimulation, PLEF stimulation has a graded, modulatory effect on neuronal excitability, and permits the simultaneous recording of neuronal activity during stimulation suitable for continuous feedback control. We tested a prototype system that allows for simultaneous PLEF stimulation with minimal recording artifact in a chronic tetanus toxin animal model (rat) of hippocampal epilepsy with spontaneous seizures. Depth electrode local field potentials recorded during seizures revealed a characteristic pattern of field postsynaptic potentials (fPSPs). Sinusoidal voltage-controlled PLEF stimulation (0.5-25 Hz) was applied in open-loop cycles radially across the CA3 of ventral hippocampus. For stimulated seizures, fPSPs were transiently entrained with the PLEF waveform. Statistical significance of entrainment was assessed with Thomson's harmonic F-test, with 45/132 stimulated seizures in four animals individually demonstrating significant entrainment (p < 0.04). Significant entrainment for multiple presentations at the same frequency (p < 0.01) was observed in three of four animals in 42/64 stimulated seizures. This is the first demonstration in chronically implanted freely behaving animals of PLEF modulation of neural activity with simultaneous recording.

Clinical experience with anticonvulsant medication in pediatric epilepsy and comorbid bipolar spectrum disorder.

Anticonvulsant drugs are first-line treatments for both bipolar mood disorder and epilepsy; however, few studies have explored treatment options when these disorders co-occur. The aim of this study was to identify bipolar disorder symptoms common in pediatric epilepsy and to determine whether anticonvulsant monotherapy might be a practical treatment consideration. A retrospective chart review identified 38 children with bipolar spectrum disorder and epilepsy comorbidity. Two mental health clinicians independently assessed psychiatric diagnoses, symptoms, and assigned retrospective CGI-I ratings for psychiatric symptoms. Common bipolar symptoms included impulsivity, psychomotor agitation, and explosive rage. Forty-two medication trials with 11 different anticonvulsants were identified. Of the 30 instances in which anticonvulsant monotherapy was attempted, carbamazepine, divalproex sodium, lamotrigine, and oxcarbazepine were associated with better psychiatric CGI-I ratings than other monotherapies (P<0.01). Results suggest that in many cases, selected anticonvulsants appeared to simultaneously treat both epilepsy and mood disorder. Controlled trials are necessary to further ascertain optimal anticonvulsant usage.

Neuronal spatiotemporal pattern discrimination: the dynamical evolution of seizures.

We developed a modern numerical approach to the multivariate linear discrimination of Fisher from 1936 based upon singular value decomposition that is sufficiently stable to permit widespread application to spatiotemporal neuronal patterns. We demonstrate this approach on an old problem in neuroscience--whether seizures have distinct dynamical states as they evolve with time. A practical result was the first demonstration that human seizures have distinct initiation and termination dynamics, an important characterization as we seek to better understand how seizures start and stop. Our approach is broadly applicable to a wide variety of neuronal data, from multichannel EEG or MEG, to sequentially acquired optical imaging data or fMRI.

New antiepileptic drugs: comparative studies of efficacy and cognition.

Over the past 10 years, the Food and Drug Administration has approved eight prophylactic antiepileptic drugs (AEDs). Although the goal of universal seizure control without side effects has not been reached, the tolerability of medications has improved. This paper reviews the AEDs introduced since 1993 and tries to objectively present comparative data obtained in double-blind studies.

In vivo modulation of hippocampal epileptiform activity with radial electric fields.

PURPOSE: Electric field stimulation can interact with brain activity in a subthreshold manner. Electric fields have been previously adaptively applied to control seizures in vitro. We report the first results from establishing suitable electrode geometries and trajectories, as well as stimulation and recording electronics, to apply this technology in vivo. METHODS: Electric field stimulation was performed in a rat kainic acid injection seizure model. Radial electric fields were generated unilaterally in hippocampus from an axial depth electrode. Both sinusoidal and multiphasic stimuli were applied. Hippocampal activity was recorded bilaterally from tungsten microelectrode pairs. Histologic examination was performed to establish electrode trajectory and characterize lesioning. RESULTS: Electric field modulation of epileptiform neural activity in phase with the stimulus was observed in five of six sinusoidal and six of six multiphasic waveform experiments. Both excitatory and suppressive modulation were observed in the two experiments with stimulation electrodes most centrally placed within the hippocampus. Distinctive modulation was observed in the period preceding seizure-onset detection in two of six experiments. Short-term histologic tissue damage was observed in one of six experiments associated with high unbalanced charge delivery. CONCLUSIONS: We demonstrated in vivo electric field modulation of epileptiform hippocampal activity, suggesting that electric field control of in vivo seizures may be technically feasible. The response to stimulation before seizure could be useful for triggering control systems, and may be a novel approach to define a preseizure state.