Deep brain stimulation in epilepsy

Deep brain stimulation of the subthalamic nucleus for a patient with drug resistant juvenile myoclonic epilepsy: 1 year follow-up

BACKGROUND

Drug-resistant juvenile myoclonic epilepsy (DR-JME) remains a significant challenge in neurology. Traditional management strategies often fail to achieve satisfactory control, necessitating innovative treatments.

OBJECTIVE

This case report aims to evaluate the efficacy and safety of deep brain stimulation (DBS) targeting the subthalamic nucleus (STN-DBS) in a patient with DR-JME.

METHODS

We describe the treatment of a patient with DR-JME using STN-DBS. The patient underwent implantation and received high-frequency stimulation (HFS) at the STN.

RESULTS

One year post-implantation, the patient demonstrated a substantial reduction in motor seizure frequency by 87.5%, with improvements in quality of life and seizure severity by 52.0% and 46.7%, respectively. No adverse events were reported during the follow-up period.

CONCLUSIONS

This case represents the first report of favorable outcomes with STN-DBS in a patient with DR-JME, suggesting that long-term HFS of the STN may be a promising treatment option for patients suffering from this condition.

Transient targeting of hypothalamic orexin neurons alleviates seizures in a mouse model of epilepsy

Lateral hypothalamic (LH) hypocretin/orexin neurons (HONs) control brain-wide electrical excitation. Abnormally high excitation produces epileptic seizures, which affect millions of people and need better treatments. HON population activity spikes from minute to minute, but the role of this in seizures is unknown. Here, we describe correlative and causal links between HON activity spikes and seizures. Applying temporally-targeted HON recordings and optogenetic silencing to a male mouse model of acute epilepsy, we found that pre-seizure HON activity predicts and controls the electrophysiology and behavioral pathology of subsequent seizures. No such links were detected for HON activity during seizures. Having thus defined the time window where HONs influence seizures, we targeted it with LH deep brain stimulation (DBS), which inhibited HON population activity, and produced seizure protection. Collectively, these results uncover a feature of brain activity linked to seizures, and demonstrate a proof-of-concept treatment that controls this feature and alleviates epilepsy.

Long-term efficacy of deep brain stimulation of the subthalamic nucleus in patients with pharmacologically intractable epilepsy: A case series of six patients

OBJECTIVE

Epilepsy is one of the widespread neurological illnesses, and about 20%-40% of epilepsy patients are pharmacoresistant. We aimed to assess the long-term efficacy of subthalamic nucleus (STN) deep brain stimulation (DBS) for drug-resistant epilepsy.

METHODS

We included pharmacologically intractable epilepsy patients who had STN-DBS at the Chinese People's Liberation Army General Hospital between June 2016 and December 2018. We retrospectively evaluated pre- and postoperative clinical outcomes, including seizure frequency, seizure type, anti-seizure medication, cognitive function, anatomical target coordinates, stimulation parameters, and adverse events following the surgical procedure. Six patients with a mean follow-up of 49.3 ± 10.2 months, were included.

RESULTS

Seizure frequency decreased by an average of 64.0% after STN-DBS at last year follow-up (p = .046), and one patient (1/6) achieved seizure-free status. For seizure type, anti-seizure medication, and cognitive function, there were no significant differences between pre-and post-operation (p > .05). In terms of stimulation parameters, the pulse width, amplitude, and frequency were 58.3 ± 9.4 μs, 2.5 ± .7 V, and 122.5 ± 15.7 Hz, respectively. None of the patients showed normal electroencephalography during the electroencephalography reexamination. There were no surgery-related complications, and chronic STN stimulation was generally well tolerated in five patients. However, one patient (1/6) had a difficulty of dyskinesia in the right arm.

SIGNIFICANCE

In conclusion, neuromodulation of the STN by DBS is a promising option for patients with pharmacologically intractable epilepsy, especially for whose epileptic zone originates mainly from the frontoparietal region and who are unsuitable for resective surgery. Further prospective multicenter studies with a larger sample size are necessary for further exploration.

Modulatory effects of real-time electromagnetic stimulation on epileptiform activity in juvenile rat hippocampus based on multi-electrode array recordings

Electromagnetic stimulation (EMS) has proven to be useful for the focal suppression of epileptiform activity (EFA) in the hippocampus. There is a critical period during EFA for achieving the transition from brief interictal discharges (IIDs) to prolonged ictal discharges (IDs), and it is unknown whether EMS can modulate this transition. Therefore, this study aimed to evaluate the intensity- and time-dependent effect of EMS on the transition of EFA. A juvenile rat EFA model was constructed by perfusing magnesium-free artificial cerebrospinal fluid (aCSF) on brain slices, and the induced EFA was recorded using a micro-electrode array (MEA) platform. After a stable EFA event was recorded for some time, real-time pulsed magnetic stimulation with low and high peak-to-peak input magnetic field intensities was carried out. A 5-min intervention with real-time magnetic fields with low intensity was found to reduce the amplitude of IDs (ID events still existed), whereas a 5-min intervention with real-time magnetic fields with high input voltages completely suppressed IDs. Short-time magnetic fields (9s and 1min) with high or low input intensity had no effect on EFA. Real-time magnetic fields can block the normal EFA process from IIDs to IDs (i.e., a complete EFA cycle) and this suppression effect is dependent on input intensities and intervention duration. The experimental findings further indicate that magnetic stimulation may be chosen as an alternative antiepileptic therapy.

Chemogenetic attenuation of cortical seizures in nonhuman primates

Epilepsy is a disorder in which abnormal neuronal hyperexcitation causes several types of seizures. Because pharmacological and surgical treatments occasionally interfere with normal brain function, a more focused and on-demand approach is desirable. Here we examined the efficacy of a chemogenetic tool-designer receptors exclusively activated by designer drugs (DREADDs)-for treating focal seizure in a nonhuman primate model. Acute infusion of the GABA_A receptor antagonist bicuculline into the forelimb region of unilateral primary motor cortex caused paroxysmal discharges with twitching and stiffening of the contralateral arm, followed by recurrent cortical discharges with hemi- and whole-body clonic seizures in two male macaque monkeys. Expression of an inhibitory DREADD (hM4Di) throughout the seizure focus, and subsequent on-demand administration of a DREADD-selective agonist, rapidly suppressed the wide-spread seizures. These results demonstrate the efficacy of DREADDs for attenuating cortical seizure in a nonhuman primate model.

Optogenetic activation of the superior colliculus attenuates spontaneous seizures in the pilocarpine model of temporal lobe epilepsy

OBJECTIVE

Decades of studies have indicated that activation of the deep and intermediate layers of the superior colliculus can suppress seizures in a wide range of experimental models of epilepsy. However, prior studies have not examined efficacy against spontaneous limbic seizures. The present study aimed to address this gap through chronic optogenetic activation of the superior colliculus in the pilocarpine model of temporal lobe epilepsy.

METHODS

Sprague Dawley rats underwent pilocarpine-induced status epilepticus and were maintained until the onset of spontaneous seizures. Virus coding for channelrhodopsin-2 was injected into the deep and intermediate layers of the superior colliculus, and animals were implanted with head-mounted light-emitting diodes at the same site. Rats were stimulated with either 5- or 100-Hz light delivery. Seizure number, seizure duration, 24-h seizure burden, and behavioral seizure severity were monitored.

RESULTS

Both 5- and 100-Hz optogenetic stimulation of the deep and intermediate layers of the superior colliculus reduced daily seizure number and total seizure burden in all animals in the active vector group. Stimulation did not affect either seizure duration or behavioral seizure severity. Stimulation was without effect in opsin-negative control animals.

SIGNIFICANCE

Activation of the deep and intermediate layers of the superior colliculus reduces both the number of seizures and total daily seizure burden in the pilocarpine model of temporal lobe epilepsy. These novel data demonstrating an effect against chronic experimental seizures complement a long history of studies documenting the antiseizure efficacy of superior colliculus activation in a range of acute seizure models.

Acute and chronic convection-enhanced muscimol delivery into the rat subthalamic nucleus induces antiseizure effects associated with high responder rates

Intracerebral drug delivery is an emerging treatment strategy aiming to manage seizures in patients with systemic drug-resistant epilepsies. In rat seizure and epilepsy models, the GABA_A receptor agonist muscimol has shown powerful antiseizure potential when injected acutely into the subthalamic nucleus (STN), known for its capacity to provide remote control of different seizure types. However, chronic intrasubthalamic muscimol delivery required for long-term seizure suppression has not yet been investigated. We tested the hypothesis that chronic convection-enhanced delivery (CED) of muscimol into the STN produces long-lasting antiseizure effects in the intravenous pentylenetetrazole seizure threshold test in female rats. Acute microinjection was included to verify efficacy of intrasubthalamic muscimol delivery in this seizure model and caused significant antiseizure effects at 30 and 60 ng per hemisphere with a dose-dependent increase of responders and efficacy and only mild adverse effects compared to controls. For the chronic study, muscimol was bilaterally infused into the STN over three weeks at daily doses of 60, 300, or 600 ng per hemisphere using an implantable pump and cannula system. Chronic intrasubthalamic CED of muscimol caused significant long-lasting antiseizure effects for up to three weeks at 300 and 600 ng daily. Drug responder rate increased dose-dependently, as did drug tolerance rates. Transient ataxia and body weight loss were the main adverse effects. Drug distribution was comparable (about 2-3 mm) between acute and chronic delivery. This is the first study providing proof-of-concept that not only acute, but also chronic, continuous CED of muscimol into the STN raises seizure thresholds.

Decoupling of interacting neuronal populations by time-shifted stimulation through spike-timing-dependent plasticity

The synaptic organization of the brain is constantly modified by activity-dependent synaptic plasticity. In several neurological disorders, abnormal neuronal activity and pathological synaptic connectivity may significantly impair normal brain function. Reorganization of neuronal circuits by therapeutic stimulation has the potential to restore normal brain dynamics. Increasing evidence suggests that the temporal stimulation pattern crucially determines the long-lasting therapeutic effects of stimulation. Here, we tested whether a specific pattern of brain stimulation can enable the suppression of pathologically strong inter-population synaptic connectivity through spike-timing-dependent plasticity (STDP). More specifically, we tested how introducing a time shift between stimuli delivered to two interacting populations of neurons can effectively decouple them. To that end, we first used a tractable model, i.e., two bidirectionally coupled leaky integrate-and-fire (LIF) neurons, to theoretically analyze the optimal range of stimulation frequency and time shift for decoupling. We then extended our results to two reciprocally connected neuronal populations (modules) where inter-population delayed connections were modified by STDP. As predicted by the theoretical results, appropriately time-shifted stimulation causes a decoupling of the two-module system through STDP, i.e., by unlearning pathologically strong synaptic interactions between the two populations. Based on the overall topology of the connections, the decoupling of the two modules, in turn, causes a desynchronization of the populations that outlasts the cessation of stimulation. Decoupling effects of the time-shifted stimulation can be realized by time-shifted burst stimulation as well as time-shifted continuous simulation. Our results provide insight into the further optimization of a variety of multichannel stimulation protocols aiming at a therapeutic reshaping of diseased brain networks.

Long-term ANT-DBS effects in pilocarpine-induced epileptic rats: A combined 9.4T MRI and histological study

Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) appears to be effective against seizures in animals and humans however, its therapeutic mechanisms remain elusive. This study aimed to combine 9.4T multimodal magnetic resonance imaging (MRI) with histology to investigate the longitudinal effects of long-term ANT-DBS in pilocarpine-induced epileptic rats. Status epilepsy (SE) was induced by LiCl-pilocarpine injection in 11 adult male Sprague-Dawley rats. Four weeks after SE, chronic epileptic rats underwent either ANT-DBS (n = 6) or sham-DBS (n = 5) surgery. Electroencephalography (EEG) and spontaneous recurrent seizures (SRS) were recorded for 1 week. The T2-weighted image and images from resting-state functional MRI (rs-fMRI) were acquired at three states: before SE, at 4 weeks post-SE, and at 5 weeks post-DBS. Volumes of the hippocampal subregions and hippocampal-related functional connectivity (FC) were compared longitudinally. Finally, antibodies against neuronal nuclei (NeuN) and glial fibrillary acidic proteins were used to evaluate neuronal loss and astrogliosis in the hippocampus. Long-term ANT-DBS significantly reduced seizure generalization in pilocarpine-induced epileptic rats. By analyzing the gray matter volume using T2-weighted images, long-term ANT-DBS displayed morphometric restoration of the hippocampal subregions. Neuronal protection of the hippocampal subregions and inhibition of astrogliosis in the hippocampal subregions were observed in the ANT-DBS group. ANT-DBS caused reversible regulation of FC in the insula-hippocampus and subthalamic nucleus-hippocampus. Long-term ANT-DBS provides comprehensive protection of hippocampal histology, hippocampal morphometrics, and hippocampal-related functional networks.

Deep brain stimulation of the subthalamic nucleus for epilepsy

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is a promising palliative option for patients with refractory epilepsy. However, crucial questions remain unanswered: Which patients are the optimal candidates? How, where, and when to stimulate the STN? And what is the mechanism of STN-DBS action on epilepsy? Thus, we reviewed the clinical evidence on the antiepileptic effects of STN-DBS and its possible mechanisms on drug-resistant epilepsy, its safety, and the factors influencing stimulation outcomes. This information may guide clinical decision-making. In addition, based on the current knowledge on the effect of STN-DBS on epilepsy, we suggest research that needs to be carried out in the future.

Epileptic electroencephalography classification using Embedded Dynamic Mode Decomposition

OBJECTIVE

Seizure prediction devices for drug-resistant epileptic patients could lead to improved quality of life and new treatment options, but current approaches to classification of electroencephalography (EEG) segments for early identification of the pre-seizure state typically require many features and complex classifiers. We therefore propose a novel spatio-temporal EEG feature set that significantly aids in separation and easy classification of the interictal and preictal states.

APPROACH

We derive key spectral features from the Embedded Dynamic Mode Decomposition (EmDMD) of the brain state system. This method linearizes the complex spatio-temporal dynamics of the system, describing the dynamics in terms of a spectral basis of modes and eigenvalues. The relative subband spectral power and mean phase locking values of these modes prove to be good indicators of the preictal state that precedes seizure onset.

MAIN RESULTS

We analyze the linear separability and classification of preictal and interictal states based on our proposed features using seizure data extracted from the CHB-MIT scalp EEG and Kaggle American Epilepsy Society Seizure Prediction Challenge intracranial EEG databases. With a light-weight support vector machine or random forest classifier trained on these features, we classify the preictal state with a sensitivity of up to 92% and specificity of up to 89%.

SIGNIFICANCE

The EmDMD-derived features separate the preictal and interictal states, improving classification accuracy and motivating further work to incorporate them into seizure prediction algorithms.

Epileptic seizure prediction using spectral width of the covariance matrix

Epilepsy is a common neurological disorder in which patients suffer from sudden and unpredictable seizures. Seizures are caused by excessive and abnormal neuronal activity. Different methods have been employed to investigate electroencephalogram (EEG) data in patients with epilepsy. This paper introduces a simple yet accurate array-based method to study and predict seizures. We use the CHB-MIT dataset (all 24 cases), which includes scalp EEG recordings. The proposed method is based on the random matrix theory. After applying wavelet decomposition to denoise the data, we analyze the spatial coherence of the epileptic recordings by looking at the width of the covariance matrix eigenvalue distribution at different time and frequency bins. We train patient-specific support vector machine (SVM) classifiers to distinguish between interictal and preictal data with high performance and a false prediction rate as low as 0.09/h. The proposed technique achieves an average accuracy, specificity, sensitivity, and area under the curve (AUC) of 99.05%, 93.56%, 99.09%, and 0.99, respectively. Our proposed method outperforms state-of-the-art works in terms of sensitivity while maintaining a low false prediction rate. Also, in contrast to neural networks, which may achieve high performance, this work provides high sensitivity without compromising interpretability.

A systematic review of resting-state and task-based fmri in juvenile myoclonic epilepsy

Functional neuroimaging modalities have enhanced our understanding of juvenile myoclonic epilepsy (JME) underlying neural mechanisms. Due to its non-invasive, sensitive and analytical nature, functional magnetic resonance imaging (fMRI) provides valuable insights into relevant functional brain networks and their segregation and integration properties. We systematically reviewed the contribution of resting-state and task-based fMRI to the current understanding of the pathophysiology and the patterns of seizure propagation in JME Altogether, despite some discrepancies, functional findings suggest that corticothalamo-striato-cerebellar network along with default-mode network and salience network are the most affected networks in patients with JME. However, further studies are required to investigate the association between JME's main deficiencies, e.g., motor and cognitive deficiencies and fMRI findings. Moreover, simultaneous electroencephalography-fMRI (EEG-fMRI) studies indicate that alterations of these networks play a role in seizure modulation but fall short of identifying a causal relationship between altered functional properties and seizure propagation. This review highlights the complex pathophysiology of JME, which necessitates the design of more personalized diagnostic and therapeutic strategies in this group.

Regulatory Mechanism for Absence Seizures in Bidirectional Interactive Thalamocortical Model via Different Targeted Therapy Schemes

Recent clinical practice has found that the spike-wave discharge (SWD) scopes of absence seizures change from small cortical region to large thalamocortical networks, which has also been proved by theoretical simulation. The best biophysics explanation is that there are interactions between coupled cortico-thalamic and thalamocortical circuits. To agree with experiment results and describe the phenomena better, we constructed a coupled thalamocortical model with bidirectional channel (CTMBC) to account for the causes of absence seizures which are connected by the principle of two-way communication of neural pathways. By adjusting the coupling strength of bidirectional pathways, the spike-wave discharges are reproduced. Regulatory mechanism for absence seizures is further applied to CTMBC via four different targeted therapy schemes, such as deep brain stimulation (DBS), charge-balanced biphasic pulse (CBBP), coordinated reset stimulation (CRS) 1 : 0, and (CRS) 3 : 2. The new CTMBC model shows that neurodiversity in bidirectional interactive channel could supply theory reference for the bidirectional communication mode of thalamocortical networks and the hypothesis validation of pathogenesis.

Deep Brain Stimulation for Treatment of Refractory Epilepsy

Deep brain stimulation (DBS) has been used in the treatment of motor diseases with remarkable safety and efficacy, which abet the interest of its application in the management of other neurologic and psychiatric disorders such as epilepsy. Experimental data demonstrated that electric current could modulate distinct brain circuits and decrease the neuronal hypersynchronization seen in epileptic activity. The ability to carefully choose the most suitable anatomical target as well as to define the most reasonable stimulation parameters is highly dependable on the comprehension of the underlying mechanisms of action, which remain unclear. This review aimed to explore the relevant clinical data regarding the use of DBS in the treatment of refractory epilepsy.

Connective profiles and antagonism between dynamic and static connectivity underlying generalized epilepsy

This study aims to characterize the connective profiles and the coupling relationship between dynamic and static functional connectivity (dFC and sFC) in large-scale brain networks in patients with generalized epilepsy (GE). Functional, structural and diffuse MRI data were collected from 83 patients with GE and 106 matched healthy controls (HC). Resting-state BOLD time course was deconvolved to neural time course using a blind hemodynamic deconvolution method. Then, five connective profiles, including the structural connectivity (SC) and BOLD/neural time course-derived sFC/dFC networks, were constructed based on the proposed whole brain atlas. Network-level weighted correlation probability (NWCP) were proposed to evaluate the association between dFC and sFC. Both the BOLD signal and neural time course showed highly concordant findings and the present study emphasized the consistent findings between two functional approaches. The patients with GE showed hypervariability and enhancement of FC, and notably decreased SC in the subcortical network. Besides, increased dFC, weaker anatomic links, and complex alterations of sFC were observed in the default mode network of GE. Moreover, significantly increased SC and predominantly increased sFC were found in the frontoparietal network. Remarkably, antagonism between dFC and sFC was observed in large-scale networks in HC, while patients with GE showed significantly decreased antagonism in core epileptic networks. In sum, our study revealed distinct connective profiles in different epileptic networks and provided new clues to the brain network mechanism of epilepsy from the perspective of antagonism between dynamic and static functional connectivity.

Is STN Neuromodulation of Focal Motor Seizures Ready for Prime Time?

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Not Part of the Temporal Lobe, but Still of Importance? Substantia Nigra and Subthalamic Nucleus in Epilepsy

The most researched brain region in epilepsy research is the temporal lobe, and more specifically, the hippocampus. However, numerous other brain regions play a pivotal role in seizure circuitry and secondary generalization of epileptic activity: The substantia nigra pars reticulata (SNr) and its direct input structure, the subthalamic nucleus (STN), are considered seizure gating nuclei. There is ample evidence that direct inhibition of the SNr is capable of suppressing various seizure types in experimental models. Similarly, inhibition via its monosynaptic glutamatergic input, the STN, can decrease seizure susceptibility as well. This review will focus on therapeutic interventions such as electrical stimulation and targeted drug delivery to SNr and STN in human patients and experimental animal models of epilepsy, highlighting the opportunities for overcoming pharmacoresistance in epilepsy by investigating these promising target structures.

Dynamic Transitions of Epilepsy Waveforms Induced by Astrocyte Dysfunction and Electrical Stimulation

Experimental studies have shown that astrocytes participate in epilepsy through inducing the release of glutamate. Meanwhile, considering the disinhibition circuit among inhibitory neuronal populations with different time scales and the feedforward inhibition connection from thalamic relay nucleus to cortical inhibitory neuronal population, here, we propose a modified thalamocortical field model to systematically investigate the mechanism of epilepsy. Firstly, our results show that rich firing activities can be induced by astrocyte dysfunction, including high or low saturated state, high- or low-frequency clonic, spike-wave discharge (SWD), and tonic. More importantly, with the enhancement of feedforward inhibition connection, SWD and tonic oscillations will disappear. In other words, all these pathological waveforms can be suppressed or eliminated. Then, we explore the control effects after different external stimulations applying to thalamic neuronal population. We find that single-pulse stimulation can not only suppress but also induce pathological firing patterns, such as SWD, tonic, and clonic oscillations. And we further verify that deep brain stimulation can control absence epilepsy by regulating the amplitude and pulse width of stimulation. In addition, based on our modified model, 3 : 2 coordinated reset stimulation strategies with different intensities are compared and a more effective and safer stimulation mode is proposed. Our conclusions are expected to give more theoretical insights into the treatment of epilepsy.

Control analysis of electrical stimulation for epilepsy waveforms in a thalamocortical network

Physiological experiments and computational models both show that the thalamic reticular nucleus (RE) participates in inducing various firing patterns of cortex. Absence seizure, featured by 2-4 Hz spike-wave discharges (SWD) oscillation, is a high incidence of disease in children. Lots of electrophysiological experiments have verified the correlation between absence seizures and RE, however, the dynamical mechanisms are not well understood. Based on previous Taylor model, we firstly study the effects of external input and self-inhibition of RE on epilepsy transition. We show that increasing external input and self-inhibition of RE can lead the system from epileptic state to normal state, and vice versa. Next, we explore two stimulus strategies added in RE and various transition behaviors can be induced, such as high saturated state to clonic. Meanwhile, as the intensity of stimulation increasing, they can not only suppress the SWD, but also produce tonic-clonic oscillation. Finally, the control of DBS on single neuron cluster and two neuron clusters are compared and we find stimulating RE and TC simultaneously is a superior mode to stimulate anyone of RE or TC. It is hoped that the results we obtained will have an enlightenment on clinical treatment.

Progress in Brain-Compatible Interfaces with Soft Nanomaterials

Neural interfaces facilitating communication between the brain and machines must be compatible with the soft, curvilinear, and elastic tissues of the brain and yet yield enough power to read and write information across a wide range of brain areas through high-throughput recordings or optogenetics. Biocompatible-material engineering has facilitated the development of brain-compatible neural interfaces to support built-in modulation of neural circuits and neurological disorders. Recent developments in brain-compatible neural interfaces that use soft nanomaterials more suitable for complex neural circuit analysis and modulation are reviewed. Preclinical tests of the compatibility and specificity of these interfaces in animal models are also discussed.

Deep Brain Stimulation Increases Seizure Threshold by Altering REM Sleep and Delta Powers During NREM Sleep

We previously demonstrated that seizure occurrences at different zeitgeber times alter sleep and circadian rhythm differently. On the other hand, the synchronized delta wave of electroencephalogram (EEG) during non-rapid eye movement (NREM) sleep facilitates seizure, while the desynchronized EEG of rapid eye movement (REM) sleep suppresses it. We also elucidated that unilateral deep brain stimulation (DBS) of the anterior nucleus of thalamus (ANT) suppresses seizure recurrence. In the present study, we intraperitoneally injected pentylenetetrazol (PTZ, 40 mg/kg) for 14 consecutive days (PTZ kindling) to induce spontaneous seizure in rats, and a 30-min (delivered 10 min before each PTZ injection) or a 3-h DBS of unilateral ANT (delivered 1 h before each PTZ injection) was applied to suppress seizure. The frequency of DBS stimulation was 200 Hz and the electrical current consisted of biphasic square pulses with 50-μA intensity, 100-μs pulse width, and 4.1-ms stimulation interval. Our results found that PTZ-induced spontaneous seizure did not cause a significant change in the quantity of NREM sleep but suppressed the amount of REM sleep. Unilateral ANT DBS prolonged the onset latency of ictal seizure, decreased the spontaneous seizure duration, and increased the survival rate but did not change the amplitude of epileptiform EEGs during ictal period. Unilateral ANT DBS did not significantly alter NREM sleep but increased the amount of REM sleep. An analysis of the spectrograms of fast Fourier transform indicated that the intensities of all frequencies were enhanced during the PTZ-induced ictal period and the subsequent spontaneous seizure. Thirty minutes of unilateral ANT DBS suppressed the augmentation of low-frequency (<10 Hz) intensities during the spontaneous seizure induced by PTZ kindling. We further found that consecutive injections of PTZ progressively increased the enhancement of the delta powers during NREM sleep, whereas unilateral ANT DBS inhibited this progressive enhancement. It was also noticed that 30 min of ANT DBS exhibited a better efficacy in epilepsy suppression than 3 h of ANT DBS. These results elucidated that unilateral ANT DBS enhanced the seizure threshold by increasing the amount of REM sleep and decreasing the progressive enhancement of delta power during NREM sleep to suppress spontaneous seizure recurrences in PTZ kindling-induced epileptic rats.

Dravet Syndrome: An Overview

Dravet syndrome (DS), also known as severe myoclonic epilepsy of infancy (SMEI), is one of the rare early childhood intractable epileptic encephalopathies associated with pleomorphic seizure activity, cognitive decline, motor, and behavioral abnormalities. The convulsive seizure is the most common type seen in DS. After the first episode of seizure-like activity, behavioral disorders and cognitive decline are progressive and long-lasting. The most common etiology identified in patients with DS is a de-novo genetic mutation alpha-1 subunit of voltage-gated calcium channel gene (SCN1A). DS is diagnosed clinically and if unclear, genetic testing is recommended. DS treatment options include anti-epileptic drugs and cannabinoids; ketogenic diet therapy and surgical options such as the deep brain and vagal nerve stimulation. Due to drug-refractory epilepsy in DS, many more therapies are being investigated to increase the longevity of patients.

Deep Brain Stimulation and Drug-Resistant Epilepsy: A Review of the Literature

Introduction: Deep brain stimulation is a safe and effective neurointerventional technique for the treatment of movement disorders. Electrical stimulation of subcortical structures may exert a control on seizure generators initiating epileptic activities. The aim of this review is to present the targets of the deep brain stimulation for the treatment of drug-resistant epilepsy. Methods: We performed a structured review of the literature from 1980 to 2018 using Medline and PubMed. Articles assessing the impact of deep brain stimulation on seizure frequency in patients with DRE were selected. Meta-analyses, randomized controlled trials, and observational studies were included. Results: To date, deep brain stimulation of various neural targets has been investigated in animal experiments and humans. This article presents the use of stimulation of the anterior and centromedian nucleus of the thalamus, hippocampus, basal ganglia, cerebellum and hypothalamus. Anterior thalamic stimulation has demonstrated efficacy and there is evidence to recommend it as the target of choice. Conclusion: Deep brain stimulation for seizures may be an option in patients with drug-resistant epilepsy. Anterior thalamic nucleus stimulation could be recommended over other targets.

Behavioral validation of a wireless low-power neurostimulation technology in a conditioned place preference task

OBJECTIVE

Neurostimulation technologies are important for studying neural circuits and the connections that underlie neurological and psychiatric disorders. However, current methods come with limitations such as the restraint on movement imposed by the wires delivering stimulation. The objective of this study was to assess whether the e-Particle (EP), a novel wireless neurostimulator, could sufficiently stimulate the brain to modify behavior without these limitations.

APPROACH

Rats were implanted with the EP and a commercially available stimulating electrode. Animals received rewarding brain stimulation, and performance in a conditioned place preference (CPP) task was measured. To ensure stimulation-induced neuronal activation, immediate early gene c-fos expression was also measured.

MAIN RESULTS

The EP was validated in a commonly used CPP task by demonstrating that (1) wireless stimulation via the EP induced preference behavior that was comparable to that induced by standard wired electrodes and (2) neuronal activation was observed in projection targets of the stimulation site.

SIGNIFICANCE

The EP may help achieve a better understanding of existing brain stimulation methods while overcoming their limitations. Validation of the EP in a behavioral model suggests that the benefits of this technology may extend to other areas of animal research and potentially to human clinical applications.

Neurosurgery for mental disorder

The authors review contemporary indications for neurosurgical interventions in the management of chronic and refractory mental disorder, the procedures involved, their efficacy and known adverse effects. These data are presented within the context of a brief historical overview of the use of neurosurgery for mental disorder. In addition to a consideration of neurosurgical procedures that rely on the creation of putative therapeutic lesions, we also review two novel, non-destructive neurosurgical electrostimulation treatments that may represent viable alternatives to conventional ablative neurosurgery: vagus nerve stimulation and deep brain stimulation.

Diffusion-weighted imaging of the brains of dogs with idiopathic epilepsy

Background

Idiopathic epilepsy is one of the most common neurological disorders in dogs. Unfortunately, up to 30% of dogs with idiopathic epilepsy show no improvement under antiepileptic drug treatment. Diffusion-weighted imaging is used in human medicine to identify epileptogenic foci in the brain to allow for more invasive treatments such as deep brain stimulation or surgical removal.

The aim of this study was to ass the feasibility of interictal diffusion-weighted MRI in dogs and to evaluate the distribution of diffusion in the brains of dogs with idiopathic epilepsy (IE) and to compare these values to previously published values from healthy beagle dogs.

Client-owned dogs with the final diagnosis of IE were included in this study. MRI examination was carried out using a 1.0Tesla superconductive magnet. Diffusion-weighted images using a single shot echo planar imaging sequence (SSh-EPI) with a b value of b = 0 s/mm² and b = 800 s/mm² were acquired in a dorsal and transverse plane with diffusion gradients in all three planes (x-, y- and z-plane). An ADC (apparent diffusion coefficient) map of the isometric image of each acquired slice was generated.

Regions of interest (ROIs) were manually drawn around the caudate nucleus, the thalamus, the piriform lobe including the amygdala, the hippocampus, the semioval center and the temporal cerebral cortex by one of the authors. ROI drawings were repeated 5 times at different time points to assess intra-obersver variability. A multi-way mixed-model analysis of variance (ANOVA) and two-way ANOVA were used during statistical analysis. A p value of p < 0.05 was considered significant.

Results

Dogs with IE showed a significantly increased ADC in the amygdala within the piriform lobe and in the semioval center (p < 0.05) compared with the healthy control group.

Conclusion

Changes in the piriform lobe in cases of epilepsy are reported infrequently in human and veterinary medicine. Similar to our results, ADC changes in the interictal phase usually include an increase in ADC due to cell loss and increased intercellular spaces. Diffusion MRI might be a promising technique for the examination of canine epileptic patients lacking other gross neuromorphological abnormalities.

Translating regenerative medicine techniques for the treatment of epilepsy

Epilepsy is considered a chronic neurological disorder and is accompanied by persistent and diverse disturbances in electrical brain activity. While antiepileptic pharmaceuticals are still the predominant treatment for epilepsy, the advent of numerous surgical interventions has further improved outcomes for patients. Despite these advancements, a subpopulation continues to experience intractable seizures which are resistant to current conventional and nonconventional therapeutic options. In this review, we begin with an introduction to the clinical presentation of epilepsy before discussing the clinically relevant laboratory models of epilepsy. Finally, we explore the implications of regenerative medicine – including cell therapy, neuroprotective agents, and electrical stimulation – for epilepsy, supplemented with our laboratory's data. This paper is a review article. Referred literature in this paper has been listed in the references section. The datasets supporting the conclusions of this article are available online by searching various databases, including PubMed. Some original points in this article come from the laboratory practice in our research center and the authors’ experiences.

Deep brain and cortical stimulation for epilepsy

BACKGROUND

Despite optimal medical treatment, including epilepsy surgery, many epilepsy patients have uncontrolled seizures. Since the 1970s interest has grown in invasive intracranial neurostimulation as a treatment for these patients. Intracranial stimulation includes both deep brain stimulation (DBS) (stimulation through depth electrodes) and cortical stimulation (subdural electrodes). This is an updated version of a previous Cochrane review published in 2014.

OBJECTIVES

To assess the efficacy, safety and tolerability of DBS and cortical stimulation for refractory epilepsy based on randomized controlled trials (RCTs).

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialized Register on 29 September 2015, but it was not necessary to update this search, because records in the Specialized Register are included in CENTRAL. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2016, Issue 11, 5 November 2016), PubMed (5 November 2016), ClinicalTrials.gov (5 November 2016), the WHO International Clinical Trials Registry Platform ICTRP (5 November 2016) and reference lists of retrieved articles. We also contacted device manufacturers and other researchers in the field. No language restrictions were imposed.

SELECTION CRITERIA

RCTs comparing deep brain or cortical stimulation versus sham stimulation, resective surgery, further treatment with antiepileptic drugs or other neurostimulation treatments (including vagus nerve stimulation).

DATA COLLECTION AND ANALYSIS

Four review authors independently selected trials for inclusion. Two review authors independently extracted the relevant data and assessed trial quality and overall quality of evidence. The outcomes investigated were seizure freedom, responder rate, percentage seizure frequency reduction, adverse events, neuropsychological outcome and quality of life. If additional data were needed, the study investigators were contacted. Results were analysed and reported separately for different intracranial targets for reasons of clinical heterogeneity.

MAIN RESULTS

Twelve RCTs were identified, eleven of these compared one to three months of intracranial neurostimulation with sham stimulation. One trial was on anterior thalamic DBS (n = 109; 109 treatment periods); two trials on centromedian thalamic DBS (n = 20; 40 treatment periods), but only one of the trials (n = 7; 14 treatment periods) reported sufficient information for inclusion in the quantitative meta-analysis; three trials on cerebellar stimulation (n = 22; 39 treatment periods); three trials on hippocampal DBS (n = 15; 21 treatment periods); one trial on nucleus accumbens DBS (n = 4; 8 treatment periods); and one trial on responsive ictal onset zone stimulation (n = 191; 191 treatment periods). In addition, one small RCT (n = 6) compared six months of hippocampal DBS versus sham stimulation. Evidence of selective reporting was present in four trials and the possibility of a carryover effect complicating interpretation of the results could not be excluded in five cross-over trials without any or a sufficient washout period. Moderate-quality evidence could not demonstrate statistically or clinically significant changes in the proportion of patients who were seizure-free or experienced a 50% or greater reduction in seizure frequency (primary outcome measures) after one to three months of anterior thalamic DBS in (multi)focal epilepsy, responsive ictal onset zone stimulation in (multi)focal epilepsy patients and hippocampal DBS in (medial) temporal lobe epilepsy. However, a statistically significant reduction in seizure frequency was found for anterior thalamic DBS (mean difference (MD), -17.4% compared to sham stimulation; 95% confidence interval (CI) -31.2 to -1.0; high-quality evidence), responsive ictal onset zone stimulation (MD -24.9%; 95% CI -40.1 to -6.0; high-quality evidence) and hippocampal DBS (MD -28.1%; 95% CI -34.1 to -22.2; moderate-quality evidence). Both anterior thalamic DBS and responsive ictal onset zone stimulation do not have a clinically meaningful impact on quality life after three months of stimulation (high-quality evidence). Electrode implantation resulted in postoperative asymptomatic intracranial haemorrhage in 1.6% to 3.7% of the patients included in the two largest trials and 2.0% to 4.5% had postoperative soft tissue infections (9.4% to 12.7% after five years); no patient reported permanent symptomatic sequelae. Anterior thalamic DBS was associated with fewer epilepsy-associated injuries (7.4 versus 25.5%; P = 0.01) but higher rates of self-reported depression (14.8 versus 1.8%; P = 0.02) and subjective memory impairment (13.8 versus 1.8%; P = 0.03); there were no significant differences in formal neuropsychological testing results between the groups. Responsive ictal-onset zone stimulation seemed to be well-tolerated with few side effects.The limited number of patients preclude firm statements on safety and tolerability of hippocampal DBS. With regards to centromedian thalamic DBS, nucleus accumbens DBS and cerebellar stimulation, no statistically significant effects could be demonstrated but evidence is of only low to very low quality.

AUTHORS' CONCLUSIONS

Except for one very small RCT, only short-term RCTs on intracranial neurostimulation for epilepsy are available. Compared to sham stimulation, one to three months of anterior thalamic DBS ((multi)focal epilepsy), responsive ictal onset zone stimulation ((multi)focal epilepsy) and hippocampal DBS (temporal lobe epilepsy) moderately reduce seizure frequency in refractory epilepsy patients. Anterior thalamic DBS is associated with higher rates of self-reported depression and subjective memory impairment. There is insufficient evidence to make firm conclusive statements on the efficacy and safety of hippocampal DBS, centromedian thalamic DBS, nucleus accumbens DBS and cerebellar stimulation. There is a need for more, large and well-designed RCTs to validate and optimize the efficacy and safety of invasive intracranial neurostimulation treatments.

Ultrasoft microwire neural electrodes improve chronic tissue integration

Chronically implanted neural multi-electrode arrays (MEA) are an essential technology for recording electrical signals from neurons and/or modulating neural activity through stimulation. However, current MEAs, regardless of the type, elicit an inflammatory response that ultimately leads to device failure. Traditionally, rigid materials like tungsten and silicon have been employed to interface with the relatively soft neural tissue. The large stiffness mismatch is thought to exacerbate the inflammatory response. In order to minimize the disparity between the device and the brain, we fabricated novel ultrasoft electrodes consisting of elastomers and conducting polymers with mechanical properties much more similar to those of brain tissue than previous neural implants. In this study, these ultrasoft microelectrodes were inserted and released using a stainless steel shuttle with polyethyleneglycol (PEG) glue. The implanted microwires showed functionality in acute neural stimulation. When implanted for 1 or 8weeks, the novel soft implants demonstrated significantly reduced inflammatory tissue response at week 8 compared to tungsten wires of similar dimension and surface chemistry. Furthermore, a higher degree of cell body distortion was found next to the tungsten implants compared to the polymer implants. Our results support the use of these novel ultrasoft electrodes for long term neural implants.

STATEMENT OF SIGNIFICANCE

One critical challenge to the translation of neural recording/stimulation electrode technology to clinically viable devices for brain computer interface (BCI) or deep brain stimulation (DBS) applications is the chronic degradation of device performance due to the inflammatory tissue reaction. While many hypothesize that soft and flexible devices elicit reduced inflammatory tissue responses, there has yet to be a rigorous comparison between soft and stiff implants. We have developed an ultra-soft microelectrode with Young's modulus lower than 1MPa, closely mimicking the brain tissue modulus. Here, we present a rigorous histological comparison of this novel ultrasoft electrode and conventional stiff electrode with the same size, shape and surface chemistry, implanted in rat brains for 1-week and 8-weeks. Significant improvement was observed for ultrasoft electrodes, including inflammatory tissue reaction, electrode-tissue integration as well as mechanical disturbance to nearby neurons. A full spectrum of new techniques were developed in this study, from insertion shuttle to in situ sectioning of the microelectrode to automated cell shape analysis, all of which should contribute new methods to the field. Finally, we showed the electrical functionality of the ultrasoft electrode, demonstrating the potential of flexible neural implant devices for future research and clinical use.

The antiepileptogenic effect of low-frequency stimulation on perforant path kindling involves changes in regulators of G-protein signaling in rat

G-protein coupled receptors may have a role in mediating the antiepileptogenic effect of low-frequency stimulation (LFS) on kindling acquisition. This effect is accompanied by changes at the intracellular level of cAMP. In the present study, the effect of rolipram as a phosphodiesterase inhibitor on the antiepileptogenic effect of LFS was investigated. Meanwhile, the expression of α_s- and α_i-subunit of G proteins and regulators of G-protein signaling (RGS) proteins following LFS application was measured. Male Wistar rats were kindled by perforant path stimulation in a semi-rapid kindling manner (12 stimulations per day) during a period of 6days. Application of LFS (0.1ms pulse duration at 1Hz, 200 pulses, 50-150μA, 5min after termination of daily kindling stimulations) to the perforant path retarded the kindling development and prevented the kindling-induced potentiation and kindling-induced changes in paired pulse indices in the dentate gyrus. Intra-cerebroventricular microinjection of rolipram (0.25μM) partially prevented these LFS effects. Twenty-four hours after the last kindling stimulation, the dentate gyrus was removed and changes in protein expression were measured by Western blotting. There was no significant difference in the expression of α-subunit of G_s and G_i/o proteins in different experimental groups. However, application of LFS during the kindling procedure decreased the expression RGS4 and RGS10 proteins (that reduce the activity of G_i/o) and prevented the kindling-induced decrease of RGS2 protein (which reduces the G_s activity). Therefore, it can be postulated that the G_i/o protein signaling pathways may be involved in antiepileptogenetic effect of LFS, and this is why decreasing the cAMP metabolism by rolipram attenuates this effect of LFS.

Altered local spontaneous activity in frontal lobe epilepsy: a resting-state functional magnetic resonance imaging study

PURPOSE

The purpose of this study was to investigate the local spatiotemporal consistency of spontaneous brain activity in patients with frontal lobe epilepsy (FLE).

METHOD

Eyes closed resting-state functional magnetic resonance imaging (fMRI) data were collected from 19 FLE patients and 19 age- and gender-matched healthy controls. A novel measure, named FOur-dimensional (spatiotemporal) Consistency of local neural Activities (FOCA) was used to assess the spatiotemporal consistency of local spontaneous activity (emphasizing both local temporal homogeneity and regional stability of brain activity states). Then, two-sample t test was performed to detect the FOCA differences between two groups. Partial correlations between the FOCA values and durations of epilepsy were further analyzed.

KEY FINDINGS

Compared with controls, FLE patients demonstrated increased FOCA in distant brain regions including the frontal and parietal cortices, as well as the basal ganglia. The decreased FOCA was located in the temporal cortex, posterior default model regions, and cerebellum. In addition, the FOCA measure was linked to the duration of epilepsy in basal ganglia.

SIGNIFICANCE

Our study suggested that alterations of local spontaneous activity in frontoparietal cortex and basal ganglia was associated with the pathophysiology of FLE; and the abnormality in frontal and default model regions might account for the potential cognitive impairment in FLE. We also presumed that the FOCA measure had potential to provide important insights into understanding epilepsy such as FLE.

Altered basal ganglia-cortical functional connections in frontal lobe epilepsy: A resting-state fMRI study

OBJECTIVES

The purpose of this study was to investigate alterations of basal ganglia-cortical functional connections in patients with frontal lobe epilepsy (FLE).

METHOD

Resting-state functional magnetic resonance imaging (fMRI) data were gathered from 19 FLE patients and 19 age- and gender-matched healthy controls. Functional connectivity (FC) analysis was used to assess the functional connections between basal ganglia and cerebral cortex. Regions of interest, including the left/right caudate, putamen, pallidum and thalamus, were selected as the seeds. Two sample t-test was used to determine the difference between patients and controls, while controlling the age, gender and head motions.

RESULTS

Compared with controls, FLE patients demonstrated increased FCs between basal ganglia and regions including the right fusiform gyrus, the bilateral cingulate gyrus, the precuneus and anterior cingulate gyrus. Reduced FCs were mainly located in a range of brain regions including the bilateral middle occipital gyrus, the ventral frontal lobe, the right putamen, the left fusiform gyrus and right rolandic operculum. In addition, the relationships between basal ganglia-cingulate connections and durations of epilepsy were also found.

CONCLUSION

The alterations of functional integrity within the basal ganglia, as well as its connections to limbic and ventral frontal areas, indicate the important roles of the basal ganglia-cortical functional connections in FLE, and provide new insights in the pathophysiological mechanism of FLE.

Complex discharge-affecting networks in juvenile myoclonic epilepsy: A simultaneous EEG-fMRI study

Juvenile myoclonic epilepsy (JME) is a common subtype of idiopathic generalized epilepsies (IGEs) and is characterized by myoclonic jerks, tonic-clonic seizures and infrequent absence seizures. The network notion has been proposed to better characterize epilepsy. However, many issues remain not fully understood in JME, such as the associations between discharge-affecting networks and the relationships among resting-state networks. In this project, eigenspace maximal information canonical correlation analysis (emiCCA) and functional network connectivity (FNC) analysis were applied to simultaneous EEG-fMRI data from JME patients. The main findings of our study are as follows: discharge-affecting networks comprising the default model (DMN), self-reference (SRN), basal ganglia (BGN) and frontal networks have linear and nonlinear relationships with epileptic discharge information in JME patients; the DMN, SRN and BGN have dense/specific associations with discharge-affecting networks as well as resting-state networks; and compared with controls, significantly increased FNCs between the salience network (SN) and resting-state networks are found in JME patients. These findings suggest that the BGN, DMN and SRN may play intermediary roles in the modulation and propagation of epileptic discharges. These roles further tend to disturb the switching function of the SN in JME patients. We also postulate that emiCCA and FNC analysis may provide a potential analysis platform to provide insights into our understanding of the pathophysiological mechanism of epilepsy subtypes such as JME. Hum Brain Mapp 37:3515-3529, 2016. © 2016 Wiley Periodicals, Inc.

Technical aspects of neurostimulation: Focus on equipment, electric field modeling, and stimulation protocols

Neuromodulation is a field of science, medicine, and bioengineering that encompasses implantable and non-implantable technologies for the purpose of improving quality of life and functioning of humans. Brain neuromodulation involves different neurostimulation techniques: transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS), which are being used both to study their effects on cognitive brain functions and to treat neuropsychiatric disorders. The mechanisms of action of neurostimulation remain incompletely understood. Insight into the technical basis of neurostimulation might be a first step towards a more profound understanding of these mechanisms, which might lead to improved clinical outcome and therapeutic potential. This review provides an overview of the technical basis of neurostimulation focusing on the equipment, the present understanding of induced electric fields, and the stimulation protocols. The review is written from a technical perspective aimed at supporting the use of neurostimulation in clinical practice.

Differential Modulation of Excitatory and Inhibitory Neurons during Periodic Stimulation

Non-invasive transcranial neuronal stimulation, in addition to deep brain stimulation, is seen as a promising therapeutic and diagnostic approach for an increasing number of neurological diseases such as epilepsy, cluster headaches, depression, specific type of blindness, and other central nervous system disfunctions. Improving its effectiveness and widening its range of use may strongly rely on development of proper stimulation protocols that are tailored to specific brain circuits and that are based on a deep knowledge of different neuron types response to stimulation. To this aim, we have performed a simulation study on the behavior of excitatory and inhibitory neurons subject to sinusoidal stimulation. Due to the intrinsic difference in membrane conductance properties of excitatory and inhibitory neurons, we show that their firing is differentially modulated by the wave parameters. We analyzed the behavior of the two neuronal types for a broad range of stimulus frequency and amplitude and demonstrated that, within a small-world network prototype, parameters tuning allow for a selective enhancement or suppression of the excitation/inhibition ratio.

Optogenetic activation of superior colliculus neurons suppresses seizures originating in diverse brain networks

Because sites of seizure origin may be unknown or multifocal, identifying targets from which activation can suppress seizures originating in diverse networks is essential. We evaluated the ability of optogenetic activation of the deep/intermediate layers of the superior colliculus (DLSC) to fill this role. Optogenetic activation of DLSC suppressed behavioral and electrographic seizures in the pentylenetetrazole (forebrain+brainstem seizures) and Area Tempestas (forebrain/complex partial seizures) models; this effect was specific to activation of DLSC, and not neighboring structures. DLSC activation likewise attenuated seizures evoked by gamma butyrolactone (thalamocortical/absence seizures), or acoustic stimulation of genetically epilepsy prone rates (brainstem seizures). Anticonvulsant effects were seen with stimulation frequencies as low as 5 Hz. Unlike previous applications of optogenetics for the control of seizures, activation of DLSC exerted broad-spectrum anticonvulsant actions, attenuating seizures originating in diverse and distal brain networks. These data indicate that DLSC is a promising target for optogenetic control of epilepsy.

Neuromodulation for Epilepsy

Several palliative neuromodulation treatment modalities are currently available for adjunctive use in the treatment of medically intractable epilepsy. Over the past decades, a variety of different central and peripheral nervous system sites have been identified, clinically and experimentally, as potential targets for chronic, nonresponsive therapeutic neurostimulation. Currently, the main modalities in clinical use, from most invasive to least invasive, are anterior thalamus deep brain stimulation, vagus nerve stimulation, and trigeminal nerve stimulation. Significant reductions in seizure frequency have been demonstrated in clinical trials using each of these neuromodulation therapies.

Big data for health

This paper provides an overview of recent developments in big data in the context of biomedical and health informatics. It outlines the key characteristics of big data and how medical and health informatics, translational bioinformatics, sensor informatics, and imaging informatics will benefit from an integrated approach of piecing together different aspects of personalized information from a diverse range of data sources, both structured and unstructured, covering genomics, proteomics, metabolomics, as well as imaging, clinical diagnosis, and long-term continuous physiological sensing of an individual. It is expected that recent advances in big data will expand our knowledge for testing new hypotheses about disease management from diagnosis to prevention to personalized treatment. The rise of big data, however, also raises challenges in terms of privacy, security, data ownership, data stewardship, and governance. This paper discusses some of the existing activities and future opportunities related to big data for health, outlining some of the key underlying issues that need to be tackled.

Poly (3, 4-ethylenedioxythiophene)-ionic liquid coating improves neural recording and stimulation functionality of MEAs

In vivo multi-electrode arrays (MEAs) can sense electrical signals from a small set of neurons or modulate neural activity through micro-stimulation. Electrode's geometric surface area (GSA) and impedance are important for both unit recording and neural stimulation. Smaller GSA is preferred due to enhanced selectivity of neural signal, but it tends to increase electrode impedance. Higher impedance leads to increased electrical noise and signal loss in single unit neural recording. It also yields a smaller charge injection window for safe neural stimulation. To address these issues, poly (3, 4-ethylenedioxythiophene) - ionic liquid (PEDOT-IL) conducting polymers were electrochemically polymerized on the surface of the microelectrodes. The PEDOT-IL coating reduced the electrode impedance modulus by over 35 times at 1 kHz. It also exhibited compelling nanostructure in surface morphology and significant impedance reduction in other physiologically relevant range (100Hz-1000Hz). PEDOT-IL coated electrodes exhibited a Charge Storage Capacity (CSC) that was about 20 times larger than that of bare electrodes. The neural recording performance of PEDOT-IL coated electrodes was also compared with uncoated electrodes and PEDOT-poly (styrenesulfonate) (PSS) coated electrodes in rat barrel cortex (SI). Spontaneous neural activity and sensory evoked neural response were utilized for characterizing the electrode performance. The PEDOT-IL electrodes exhibited a higher unit yield and signal-to-noise ratio (SNR) in vivo. The local field potential recording was benefited from the low impedance PEDOT-IL coating in noise and artifact reduction as well. Moreover, cell culture on PEDOT-IL coating demonstrated that the material is safe for neural tissue and reduces astrocyte fouling. Taken together, PEDOT-IL coating has the potential to benefit neural recording and stimulation electrodes, especially when integrated with novel small GSA electrode arrays designed for high recording density, minimal insertion damage and alleviated tissue reaction.

The genetic absence epilepsy rat from Strasbourg as a model to decipher the neuronal and network mechanisms of generalized idiopathic epilepsies

First characterized in 1982, the genetic absence epilepsy rat from Strasbourg (GAERS) has emerged as an animal model highly reminiscent of a specific form of idiopathic generalized epilepsy. Both its electrophysiological (spike-and-wave discharges) and behavioral (behavioral arrest) features fit well with those observed in human patients with typical absence epilepsy and required by clinicians for diagnostic purposes. In addition, its sensitivity to antiepileptic drugs closely matches what has been described in the clinic, making this model one of the most predictive. Here, we report how the GAERS, thanks to its spontaneous, highly recurrent and easily recognizable seizures on electroencephalographic recordings, allows to address several key-questions about the pathophysiology and genetics of absence epilepsy. In particular, it offers the unique possibility to explore simultaneously the neural circuits involved in the generation of seizures at different levels of integration, using multiscale methodologies, from intracellular recording to functional magnetic resonance imaging. In addition, it has recently allowed to perform proofs of concept for innovative therapeutic strategies such as responsive deep brain stimulation or synchrotron-generated irradiation based radiosurgery.

Future of seizure prediction and intervention: closing the loop

The ultimate goal of epilepsy therapies is to provide seizure control for all patients while eliminating side effects. Improved specificity of intervention through on-demand approaches may overcome many of the limitations of current intervention strategies. This article reviews the progress in seizure prediction and detection, potential new therapies to provide improved specificity, and devices to achieve these ends. Specifically, we discuss (1) potential signal modalities and algorithms for seizure detection and prediction, (2) closed-loop intervention approaches, and (3) hardware for implementing these algorithms and interventions. Seizure prediction and therapies maximize efficacy, whereas minimizing side effects through improved specificity may represent the future of epilepsy treatments.

Electrical control of epilepsy

Epilepsy afflicts approximately 1-2% of the world's population. The mainstay therapy for treating the chronic recurrent seizures that are emblematic of epilepsy are drugs that manipulate levels of neuronal excitability in the brain. However, approximately one-third of all epilepsy patients get little to no clinical relief from this therapeutic regimen. The use of electrical stimulation in many forms to treat drug-refractory epilepsy has grown markedly over the past few decades, with some devices and protocols being increasingly used as standard clinical treatment. This article seeks to review the fundamental modes of applying electrical stimulation-from the noninvasive to the nominally invasive to deep brain stimulation-for the control of seizures in epileptic patients. Therapeutic practices from the commonly deployed clinically to the experimental are discussed to provide an overview of the innovative neural engineering approaches being explored to treat this difficult disease.