Neurostimulation Devices Used in Treatment of Epilepsy

The Development of a New Vagus Nerve Simulation Electroceutical to Improve the Signal Attenuation in a Living Implant Environment

An electroceutical is a medical device that uses electrical signals to control biological functions. It can be inserted into the human body as an implant and has several crucial advantages over conventional medicines for certain diseases. This research develops a new vagus nerve simulation (VNS) electroceutical through an innovative approach to overcome the communication limitations of existing devices. A phased array antenna with a better communication performance was developed and applied to the electroceutical prototype. In order to effectively respond to changes in communication signals, we developed the steering algorithm and firmware, and designed the smart communication protocol that operates at a low power that is safe for the patients. This protocol is intended to improve a communication sensitivity related to the transmission and reception distance. Based on this technical approach, the heightened effectiveness and safety of the prototype have been ascertained, with the actual clinical tests using live animals. We confirmed the signal attenuation performance to be excellent, and a smooth communication was achieved even at a distance of 7 m. The prototype showed a much wider communication range than any other existing products. Through this, it is conceivable that various problems due to space constraints can be resolved, hence presenting many benefits to the patients whose last resort to the disease is the VNS electroceutical.

Virus-Induced Epilepsy vs. Epilepsy Patients Acquiring Viral Infection: Unravelling the Complex Relationship for Precision Treatment

The intricate relationship between viruses and epilepsy involves a bidirectional interaction. Certain viruses can induce epilepsy by infecting the brain, leading to inflammation, damage, or abnormal electrical activity. Conversely, epilepsy patients may be more susceptible to viral infections due to factors, such as compromised immune systems, anticonvulsant drugs, or surgical interventions. Neuroinflammation, a common factor in both scenarios, exhibits onset, duration, intensity, and consequence variations. It can modulate epileptogenesis, increase seizure susceptibility, and impact anticonvulsant drug pharmacokinetics, immune system function, and brain physiology. Viral infections significantly impact the clinical management of epilepsy patients, necessitating a multidisciplinary approach encompassing diagnosis, prevention, and treatment of both conditions. We delved into the dual dynamics of viruses inducing epilepsy and epilepsy patients acquiring viruses, examining the unique features of each case. For virus-induced epilepsy, we specify virus types, elucidate mechanisms of epilepsy induction, emphasize neuroinflammation's impact, and analyze its effects on anticonvulsant drug pharmacokinetics. Conversely, in epilepsy patients acquiring viruses, we detail the acquired virus, its interaction with existing epilepsy, neuroinflammation effects, and changes in anticonvulsant drug pharmacokinetics. Understanding this interplay advances precision therapies for epilepsy during viral infections, providing mechanistic insights, identifying biomarkers and therapeutic targets, and supporting optimized dosing regimens. However, further studies are crucial to validate tools, discover new biomarkers and therapeutic targets, and evaluate targeted therapy safety and efficacy in diverse epilepsy and viral infection scenarios.

Continuous theta-burst stimulation in patients with drug-resistant epilepsy: A single-blind placebo-controlled cross-over pilot study

OBJECTIVES

To evaluate the effect of continuous theta-burst stimulation (cTBS) in patients with drug-resistant epilepsy (DRE).

METHODS

Twelve patients with DRE (five with idiopathic generalized and seven with focal epilepsy) were included in this cross-over design study and randomized to either first sham or first active stimulation, each applied for 5 consecutive days. A round coil over the vertex was used in generalized epilepsy or a figure-of-8 coil over the "epileptogenic area" in focal epilepsy. Sham stimulation was given by placing the coil 90° perpendicular to the head. The number of seizures, electroencephalography findings, Quality of Life in Epilepsy Inventory (QOLIE-84), and Symptom Check List (SCL-90) scores evaluated during the 8-12 weeks before and after active and sham stimulations were compared statistically.

RESULTS

Eight patients could complete both active and sham stimulation periods of 5 days and two patients completed active stimulation sessions, without any significant adverse effects. The number of seizures significantly reduced after active cTBS, but not after sham stimulation, when compared with those recorded before the stimulation period. QOLIE scores were increased, but interictal epileptiform discharges and SCL-90 scores showed no difference after cTBS. Active stimulation was stopped in one patient after he experienced an aggravation of myoclonic seizures.

CONCLUSIONS

cTBS seemed to be relatively safe and gave promising results in reducing the frequency of seizures in patients with both generalized and focal DRE. This time-saving technique may ease the introduction of repetitive transcranial magnetic stimulation into the routine practice of busy epilepsy clinics.

Tonic and phasic stimulations of ventral tegmental area have opposite effects on pentylenetetrazol kindled seizures in mice

Dopamine may be involved in the anticonvulsant action of deep brain stimulation (DBS). Therefore, ventral tegmental area (VTA), as a brain dopaminergic nucleus, may be a suitable target for DBS anticonvulsant action. This study investigated the effect of tonic and phasic stimulations of the VTA on seizure parameters. Seizures were induced in adult mice by sequential injections of a sub-convulsive dose of 35 mg/kg pentylenetetrazole (PTZ) every 48 h to develop the chemical kindling until the mice reached full kindled state (showing three consecutive seizure stages 4 or 5). Fully kindled mice received DBS once a day as tonic (square waves at 1 Hz; pulse duration: 200 μs; intensity: 300 μA; 600 pulses in 10 min) or phasic (square waves at 100 Hz; pulse duration: 200 μs; intensity: 300 μA; 8 trains of 10 pulses at 1 min interval; 800 pulses in 10 min) stimulations applied into their VTA for 4 days. A single dose of PTZ was injected after each DBS. Simultaneously electrocorticography and video recordings were performed during the seizure for accuracy in seizure severity parameters detection. Tonic but not phasic stimulation significantly decreased the epileptiform discharge duration and the seizure behavioral parameters such as maximum seizure stage, stage 5 duration, seizure duration. In addition, focal to generalized seizure latency increased following VTA tonic stimulation. These data suggest that tonic (but not phasic) stimulation of VTA before PTZ injection on 4 test days had anticonvulsant effects on PTZ-kindled seizures.

Predictive value of magnetoencephalography in guiding the intracranial implant strategy for intractable epilepsy

OBJECTIVE

Magnetoencephalography (MEG) is a useful component of the presurgical evaluation of patients with epilepsy. Due to its high spatiotemporal resolution, MEG often provides additional information to the clinician when forming hypotheses about the epileptogenic zone (EZ). Because of the increasing utilization of stereo-electroencephalography (sEEG), MEG clusters are used to guide sEEG electrode targeting with increasing frequency. However, there are no predefined features of an MEG cluster that predict ictal activity. This study aims to determine which MEG cluster characteristics are predictive of the EZ.

METHODS

The authors retrospectively analyzed all patients who had an MEG study (2017-2021) and underwent subsequent sEEG evaluation. MEG dipoles and sEEG electrodes were reconstructed in the same coordinate space to calculate overlap among individual contacts on electrodes and MEG clusters. MEG cluster features-including number of dipoles, proximity, angle, density, magnitude, confidence parameters, and brain region-were used to predict ictal activity in sEEG. Logistic regression was used to identify important cluster features and to train a binary classifier to predict ictal activity.

RESULTS

Across 40 included patients, 196 electrodes (42.2%) sampled MEG clusters. Electrodes that sampled MEG clusters had higher rates of ictal and interictal activity than those that did not sample MEG clusters (ictal 68.4% vs 39.8%, p < 0.001; interictal 71.9% vs 44.6%, p < 0.001). Logistic regression revealed that the number of dipoles (odds ratio [OR] 1.09, 95% confidence interval [CI] 1.04-1.14, t = 3.43) and confidence volume (OR 0.02, 95% CI 0.00-0.86, t = -2.032) were predictive of ictal activity. This model was predictive of ictal activity with 77.3% accuracy (sensitivity = 80%, specificity = 74%, C-statistic = 0.81). Using only the number of dipoles had a predictive accuracy of 75%, whereas a threshold between 14 and 17 dipoles in a cluster detected ictal activity with 75.9%-85.2% sensitivity.

CONCLUSIONS

MEG clusters with approximately 14 or more dipoles are strong predictors of ictal activity and may be useful in the preoperative planning of sEEG implantation.

Low Power EEG Data Encoding for Brain Neurostimulation Implants

Neurostimulation devices applied for the treatment of epilepsy that collect, encode, temporarily store, and transfer electroencephalographic (EEG) signals recorded intracranially from epileptic patients, suffer from short battery life spans. The principal goal of this study is to implement strategies for low power consumption rates during the device’s smooth and uninterrupted operation as well as during data transmission. Our approach is organised in three basic levels. The first level regards the initial modelling and creation of the template for the following two stages. The second level regards the development of code for programming integrated circuits and simulation. The third and final stage regards the transmitter’s implementation at the evaluation level. In particular, more than one software and device are involved in this phase, in order to achieve realistic performance. Our research aims to evolve such technologies so that they can transmit wireless data with simultaneous energy efficiency.

Grey and white matter microstructure changes in epilepsy patients with vagus nerve stimulators

OBJECTIVES

Vagus nerve stimulation (VNS) has been widely used as an effective treatment for patients with drug-resistant epilepsy (DRE). However, little is known about grey matter (GM) and white matter (WM) microstructure changes caused by VNS. This study aimed to detect consistent GM and WM alterations in epilepsy patients with vagus nerve stimulators.

METHODS

The diffusion tensor imaging data was acquired from 15 patients who underwent VNS implantation. The voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS) were used to detect group differences in GM and WM microstructure and explore their correlation with postoperative seizure reduction.

RESULTS

After 3 months of stimulation, GM density reduced in right cerebellum, left superior temporal gyrus, right inferior temporal gyrus and left thalamus, and increased in left cerebellum, left inferior parietal lobule, left middle occipital gyrus and left gyrus rectus. No significant volume changes had been found in 14 subcortical nuclei. The fractional anisotropy (FA) values reduced in left superior longitudinal fasciculus and left corticospinal tract, and increased in bilateral cingulum and body of corpus callosum. The mean diffusivity (MD) values reduced in right retrolenticular part of internal capsule, right posterior corona radiata and right superior longitudinal fasciculus. The seizure reduction had positive correlation trends with the volume reduction in left nucleus accumbens and right amygdala, and MD reduction in right medial lemniscus and right posterior corona radiata.

CONCLUSIONS

The results showed that VNS could cause changes of GM density, WM FA and MD values in epilepsy patients. The volume and MD reduction in some subcortical structures might participate in the seizure frequency reduction of VNS.

Imaging of Neuromodulation and Surgical Interventions for Epilepsy

About one-third of epilepsy cases are refractory to medical therapy. During the past decades, the availability of surgical epilepsy interventions has substantially increased as therapeutic options for this group of patients. A wide range of surgical interventions and electrophysiologic neuromodulation techniques are available, including lesional resection, lobar resection, thermoablation, disconnection, multiple subpial transections, vagus nerve stimulation, responsive neurostimulation, and deep brain stimulation. The indications and imaging features of potential complications of the newer surgical interventions may not be widely appreciated, particularly if practitioners are not associated with comprehensive epilepsy centers. In this article, we review a wide range of invasive epilepsy treatment modalities with a particular focus on their postoperative imaging findings and complications. A state-of-the-art treatment algorithm provides context for imaging findings by helping the reader understand how a particular invasive treatment decision is made.

The thalamus-precentral gyrus functional connectivity changes in epilepsy patients following vagal nerve stimulation

Vagal nerve stimulation (VNS) is an effective treatment for patients with drug-resistant epilepsy who are unsuitable for surgical epilepsy treatment. However, the mechanism of action of VNS remains unclear, and the efficacy of VNS treatment regarding seizure frequency reduction cannot be assessed before surgery. This study measured changes in functional connectivity between thalamus and precentral gyrus which are activated as vital targets of deep brain stimulation (DBS) and transcranial magnetic stimulation (TMS) using resting-state functional MRI to evaluate the effects of VNS. 16 epilepsy patients who underwent VNS were collected and scanned by resting-state functional MRI before and after operation. The functional connections (regions of interest: thalamus, precentral gyrus) were examined. After three months of stimulation, there were eight responders (≥50 % seizure reduction) and eight non-responders to VNS. No significant difference in thalamus-precentral gyrus functional connectivity was found between responders and nonresponders before operation. Enhanced functional connections were observed between bilateral thalamus and bilateral precentral gyrus in responders, which decreased in nonresponders, while functional connections between bilateral thalamus decreased in both responders and nonresponders. Short-term stimulation may cause thalamus-precentral gyrus functional connectivity changes in DRE patients, and control seizures by enhancing functional connections between bilateral thalamus and bilateral precentral gyrus.

Altered amplitude of low-frequency fluctuations and regional homogeneity in drug-resistant epilepsy patients with vagal nerve stimulators under different current intensity

BACKGROUND

The mechanisms of vagal nerve stimulation (VNS) for the treatment of drug-resistant epilepsy (DRE) remain unclear. This study aimed to measure spontaneous brain activity changes caused by VNS in DRE patients using resting-state functional MRI (rs-fMRI).

METHODS

The rs-fMRI scans were performed in 16 DRE patients who underwent VNS surgery. Amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo) was generated and examined using paired sample t-test to compare activity changes at different current intensity stage. The preoperative and postoperative ALFF/ReHo were also compared in eight responders (≥50% reduction of seizure frequency three months after surgery) and eight nonresponders using paired sample t-test.

RESULTS

The significant ALFF and ReHo changes were shown in various cortical/subcortical structures in patients under different current intensity. After three months of stimulation, responders exhibited increased ALFF in the right middle cingulate gyrus, left parahippocampal gyrus, and left cerebellum, and increased ReHo in the right postcentral gyrus, left precuneus, left postcentral gyrus, right superior parietal gyrus, right precentral gyrus, and right superior frontal gyrus. Nonresponders exhibited decreased ALFF in the left temporal lobe and right cerebellum, increased ALFF in bilateral brainstem, decreased ReHo in bilateral lingual gyri, and increased ReHo in the right middle frontal gyrus and right anterior cingulate gyrus.

CONCLUSIONS

The spontaneous neural activity changes in DRE patients caused by VNS were in an ongoing process. Increased ALFF/ReHo in frontal cortex, cingulate gyri, precentral/postcentral gyri, parahippocampal gyri, precuneus, parietal cortex, and cerebellum may implicate in VNS-induced improvement in seizure frequency.

Non-Pharmacological and Non-Surgical Treatment of Refractory Childhood Epilepsy

Nearly 20-40% of patients with epilepsy are likely to have drug resistant epilepsy (DRE). Add-on antiseizure drugs do not produce optimal seizure control in these patients. Among the non-pharmacological options, only resective surgery is curative. However, a large majority of patients are not candidates for resective epilepsy surgery. For these children with DRE, non-pharmacological non-surgery "palliative" options should be considered early than late. These include dietary therapies and neuromodulation. While there are numerous clinical trials supporting the efficacy of dietary therapies (viz ketogenic diet, modified Atkins diet and low glycemic index therapy), the evidence for neuromodulation is still evolving. Neuromodulation techniques include vagal nerve stimulation, deep brain stimulation, and transcranial magnetic stimulation. Each of the options, whether diet or neuromodulation, has its own advantages, disadvantages and adverse events profile. These have to be considered and discussed with the family before deciding the modality being chosen.

Surgical Treatments of Epilepsy

Nearly 30% of epilepsy patients are refractory to medical therapy. Surgical management of epilepsy is an increasingly viable option for these patients. Although surgery has historically been used as a palliative option, improvements in technology and outcomes show its potential in certain subsets of patients. This article reviews the two main categories of surgical epilepsy treatment-resective surgery and neuromodulation. Resective surgery includes temporal lobe resections, extratemporal resections, laser interstitial thermal therapy, and disconnection procedures. We discuss the three main types of neuromodulation-vagal nerve stimulation, responsive neurostimulation, and deep brain stimulation for epilepsy. The history and indications are explored for each type of treatment. Given the myriad types of resection and neuromodulation techniques, patient selection is reviewed in detail, with a discussion on which patients are most likely to benefit from different treatment strategies. We also discuss outcomes with examples of the pertinent landmark trials and their results. Finally, complications and surgical technique are reviewed. As new indications emerge and patient selection is refined, surgical management will continue to evolve as an adjuvant therapy for epileptic patients.

The feasibility and value of extraoperative and adjuvant intraoperative stereoelectroencephalography in rolandic and perirolandic epilepsies

OBJECTIVE

The objective of this study was to illustrate the feasibility and value of extra- and intraoperative stereoelectroencephalography (SEEG) in patients who underwent resection in rolandic and perirolandic regions.

METHODS

The authors retrospectively reviewed all consecutive patients with at least 1 year of postoperative follow-up who underwent extra- and intraoperative SEEG monitoring between January 2015 and January 2017.

RESULTS

Four patients with pharmacoresistant rolandic and perirolandic focal epilepsy were identified, who underwent conventional extraoperative invasive SEEG evaluations followed by adjuvant intraoperative SEEG recordings. Conventional extraoperative SEEG evaluations demonstrated ictal and interictal epileptiform activities involving eloquent rolandic and perirolandic cortical areas in all patients. Following extraoperative monitoring, patients underwent preplanned staged resections guided by simultaneous and continuous adjuvant intraoperative SEEG monitoring. Resections, guided by electrode contacts of interest in 3D boundaries, were performed while continuous real-time electrographic data from SEEG recordings were obtained. Staged approaches of resections were performed until there was intraoperative resolution of synchronous rolandic/perirolandic cortex epileptic activities. All patients in the cohort achieved complete seizure freedom (Engel class IA) during the follow-up period ranging from 18 to 50 months. Resection resulted in minimal neurological deficit; 3 patients experienced transient, distal plantar flexion weakness (mild foot drop).

CONCLUSIONS

The seizure and functional outcome results of this highly preselected group of patients testifies to the feasibility and demonstrates the value of the combined benefits of both intra- and extraoperative SEEG recordings when resecting the rolandic and perirolandic areas. The novel hybrid method allows a more refined and precise identification of the epileptogenic zone. Consequently, tailored resections can be performed to minimize morbidity as well as to achieve adequate seizure control.

The functional connectivity study on the brainstem-cortical/subcortical structures in responders following cervical vagus nerve stimulation

BACKGROUND

Cervical vagus nerve stimulation (VNS) is an effective neuromodulation therapy for patients with drug-resistant epilepsy (DRE). The previous studies reported that VNS may reduce seizures by regulating the functional connectivity (FC) between cortical and subcortical regions. However, no studies on brainstem have been done in responders who achieved ≥50% seizure reduction following VNS.

METHODS

Eight healthy controls and eight patients who became responders after 3 months of operation were enrolled in this study. Resting-state functional MRI (rs-fMRI) was performed, and two sample and paired sample t test were, respectively, used to detect altered FC between brainstem and cortical/subcortical regions between controls and patients, between preoperative and postoperative patients.

RESULTS

In the control group, regions with highest FC to brainstem included bilateral anterior cingulate gyri, left basal ganglia, left insula, left cuneus, right precuneus, and bilateral cerebellum. In preoperative patients, right frontal middle gyrus, bilateral basal ganglia, and right cerebellum were showed highest FC to brainstem. Compared with the controls, preoperative patients exhibited increased FC in bilateral inferior frontal gyri, right temporal cortex, while decreased FC in left insula, left postcentral gyrus, right posterior cingulate gyrus, right precuneus, and left superior parietal gyrus. In postoperative patients, regions with increased FC to brainstem were left insula, left precuneus and left cuneus, and those with decreased FC were right inferior occipital gyrus and right cerebellum.

CONCLUSIONS

Recurrent seizures caused disturbances in brainstem-cortical/subcortical FC, especially in motor executive function related regions and default mode network. VNS could reorganize the altered FC between brainstem and insula, precuneus, and cerebellum in responders.

Recurrence quantification analysis of dynamic brain networks

Evidence suggests that brain network dynamics are a key determinant of brain function and dysfunction. Here we propose a new framework to assess the dynamics of brain networks based on recurrence analysis. Our framework uses recurrence plots and recurrence quantification analysis to characterize dynamic networks. For resting-state magnetoencephalographic dynamic functional networks (dFNs), we have found that functional networks recur more quickly in people with epilepsy than in healthy controls. This suggests that recurrence of dFNs may be used as a biomarker of epilepsy. For stereo electroencephalography data, we have found that dFNs involved in epileptic seizures emerge before seizure onset, and recurrence analysis allows us to detect seizures. We further observe distinct dFNs before and after seizures, which may inform neurostimulation strategies to prevent seizures. Our framework can also be used for understanding dFNs in healthy brain function and in other neurological disorders besides epilepsy.

Calcium imaging in freely-moving mice during electrical stimulation of deep brain structures

After decades of study in humans and animal models, there remains a lack of consensus regarding how the action of electrical stimulation on neuronal and non-neuronal elements - e.g. neuropil, cell bodies, glial cells, etc. - leads to the therapeutic effects of neuromodulation therapies. To further our understanding of neuromodulation therapies, there is a critical need for novel methodological approaches using state-of-the-art neuroscience tools to study neuromodulation therapy in preclinical models of disease. In this manuscript we outline one such approach combining chronic behaving single-photon microendoscope recordings in a pathological mouse model with electrical stimulation of a common deep brain stimulation (DBS) target. We describe in detail the steps necessary to realize this approach, as well as discuss key considerations for extending this experimental paradigm to other DBS targets for different therapeutic indications. Additionally, we make recommendations from our experience on implementing and validating the required combination of procedures that includes: the induction of a pathological model (6-OHDA model of Parkinson's disease) through an injection procedure, the injection of the viral vector to induce GCaMP expression, the implantation of the GRIN lens and stimulation electrode, and the installation of a baseplate for mounting the microendoscope. We proactively identify unique data analysis confounds occurring due to the combination of electrical stimulation and optical recordings and outline an approach to address these confounds. In order to validate the technical feasibility of this unique combination of experimental methods, we present data to demonstrate that 1) despite the complex multifaceted surgical procedures, chronic optical recordings of hundreds of cells combined with stimulation is achievable over week long periods 2) this approach enables measurement of differences in DBS evoked neural activity between anesthetized and awake conditions and 3) this combination of techniques can be used to measure electrical stimulation induced changes in neural activity during behavior in a pathological mouse model. These findings are presented to underscore the feasibility and potential utility of minimally constrained optical recordings to elucidate the mechanisms of DBS therapies in animal models of disease.

Big data in status epilepticus

Status epilepticus care and treatment are already being touched by the revolution in data science. New approaches designed to leverage the tremendous potential of "big data" in the clinical sphere are enabling researchers and clinicians to extract information from sources such as administrative claims data, the electronic medical health record, and continuous physiologic monitoring data streams. Algorithmic methods of data extraction also offer potential to fuse multimodal data (including text-based documentation, imaging data, and time-series data) to improve patient assessment and stratification beyond the manual capabilities of individual physicians. Still, the potential of data science to impact the diagnosis, treatment, and minute-to-minute care of patients with status epilepticus is only starting to be appreciated. In this brief review, we discuss how data science is impacting the field and draw examples from the following three main areas: (1) analysis of insurance claims from large administrative datasets to evaluate the impact of continuous electroencephalogram (EEG) monitoring on clinical outcomes; (2) natural language processing of the electronic health record to find, classify, and stratify patients for prognostication and treatment; and (3) real-time systems for data analysis, data reduction, and multimodal data fusion to guide therapy in real time. While early, it is our hope that these examples will stimulate investigators to leverage data science, computer science, and engineering methods to improve the care and outcome of patients with status epilepticus and other neurological disorders. This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures".

In Vivo Femtosecond Laser Subsurface Cortical Microtransections Attenuate Acute Rat Focal Seizures

Recent evidence shows that seizures propagate primarily through supragranular cortical layers. To selectively modify these circuits, we developed a new technique using tightly focused, femtosecond infrared laser pulses to make as small as ~100 µm-wide subsurface cortical incisions surrounding an epileptic focus. We use this "laser scalpel" to produce subsurface cortical incisions selectively to supragranular layers surrounding an epileptic focus in an acute rodent seizure model. Compared with sham animals, these microtransections completely blocked seizure initiation and propagation in 1/3 of all animals. In the remaining animals, seizure frequency was reduced by 2/3 and seizure propagation reduced by 1/3. In those seizures that still propagated, it was delayed and reduced in amplitude. When the recording electrode was inside the partially isolated cube and the seizure focus was on the outside, the results were even more striking. In spite of these microtransections, somatosensory responses to tail stimulation were maintained but with reduced amplitude. Our data show that just a single enclosing wall of laser cuts limited to supragranular layers led to a significant reduction in seizure initiation and propagation with preserved cortical function. Modification of this concept may be a useful treatment for human epilepsy.

High-frequency stimulation of anterior nucleus of thalamus desynchronizes epileptic network in humans

Epilepsy has been classically seen as a brain disorder resulting from abnormally enhanced neuronal excitability and synchronization. Although it has been described since antiquity, there are still significant challenges achieving the therapeutic goal of seizure freedom. Deep brain stimulation of the anterior nucleus of the thalamus has emerged as a promising therapy for focal drug-resistant epilepsy; the basic mechanism of action, however, remains unclear. Here, we show that desynchronization is a potential mechanism of deep brain stimulation of the anterior nucleus of the thalamus by studying local field potentials recordings from the cortex during high-frequency stimulation (130 Hz) of the anterior nucleus of the thalamus in nine patients with drug-resistant focal epilepsy. We demonstrate that high-frequency stimulation applied to the anterior nucleus of the thalamus desynchronizes ipsilateral hippocampal background electrical activity over a broad frequency range, and reduces pathological epileptic discharges including interictal spikes and high-frequency oscillations. Furthermore, high-frequency stimulation of the anterior nucleus of the thalamus is capable of decoupling large-scale neural activity involving the hippocampus and distributed cortical areas. We found that stimulation frequencies ranging from 15 to 45 Hz were associated with synchronization of hippocampal local field potentials, whereas higher frequencies (>45 Hz) promoted desynchronization of ipsilateral hippocampal activity. Moreover, reciprocal effective connectivity between the anterior nucleus of the thalamus and the hippocampus was demonstrated by hippocampal-thalamic evoked potentials and thalamic-hippocampal evoked potentials. In summary, high-frequency stimulation of the anterior nucleus of the thalamus is shown to desynchronize focal and large-scale epileptic networks, and here is proposed as the mechanism for reducing seizure generation and propagation. Our data also demonstrate position-specific correlation between deep brain stimulation applied to the anterior nucleus of the thalamus and patients with temporal lobe epilepsy and seizure onset zone within the Papaz circuit or limbic system. Our observation may prove useful for guiding electrode implantation to increase clinical efficacy.

Chronic abdominal vagus stimulation increased brain metabolic connectivity, reduced striatal dopamine transporter and increased mid-brain serotonin transporter in obese miniature pigs

Background/objective

Changes in brain metabolism has been investigated thoroughly during unilateral cervical chronic vagal stimulation in epileptic or depressive patients. Bilateral stimulation of the abdominal vagus (_aVNS) has received less attention despite the reduction in body weight and an altered feeding behavior in obese animals that could be clinically relevant in obese individuals. Our study aims to examine the changes in brain glucose metabolism (CMR_glu) induced by _aVNS in obese adult miniature pigs. Dopamine (DAT) and serotonin transporters (SERT) were also quantified to further understand the molecular origins of the alterations in brain metabolism.

Subjects/methods

Pairs of stimulating electrodes were implanted during laparoscopy on both abdominal vagal trunks in 20 obese adult’s miniature pigs. Half of the animals were permanently stimulated while the remaining were sham stimulated. Two months after the onset of stimulation, dynamic ₁₈FDG PET and ¹²³I-ioflupane SPECT were performed. Food intake, resting energy expenditure and fat deposition were also assessed longitudinally.

Results

Food intake was halved and resting energy expenditure was increased by 60% in _aVNS group compared to sham. The gain in body weight was also 38% less in _aVNS group compared to sham. Brain metabolic connectivity increased between numerous structures including striatum, mid-brain, amygdala and hippocampus. On the contrary, increased CMR_glu were restricted to the thalamus, the periaqueducal grey and the amygdala. DAT binding potential was decreased by about one third in the striatum while SERT was about doubled in the midbrain.

Conclusions

Our findings demonstrated that _aVNS reduced weight gain as a consequence of diminished daily food intake and increased resting energy expenditure. These changes were associated with enhanced connectivity between several brain areas. A lower striatal DAT together with a doubled mid-brain SERT were likely causative for these changes.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1831-5) contains supplementary material, which is available to authorized users.

Closed-Loop Brain Stimulation for Drug-Resistant Epilepsy: Towards an Evidence-Based Approach to Personalized Medicine

Closed-loop brain stimulation is one of the few treatments available for patients who are ineligible for traditional surgical resection of the epileptogenic zone, due to having generalized epilepsy, multifocal epilepsy, or focal epilepsy localized to an eloquent brain region. Due to its clinical efficacy and potential to delivery personalized therapy based on an individual's own intracerebral electrophysiology, this treatment is becoming an important part of clinical practice, despite a limited understanding of how to program detection and stimulation parameters for optimal, patient-specific benefit. To bring this challenge into focus, we review the evolution of neural stimulation for epilepsy, provide a technical overview of the RNS System (the only FDA-approved closed-loop device), and discuss the major challenges of working with a closed-loop device. We then propose an evidence-based solution for individualizing therapy that is driven by a bottom-up informatics approach.

Neurophysiological effects of continuous cortical stimulation in epilepsy - Spike and spontaneous ECoG activity

OBJECTIVE

The effect of continuous subthreshold cortical stimulation (CSCS) over the seizure onset zone (SOZ) in epilepsy was analyzed to delineate the affected physiological processes.

METHOD

ECoG data was recorded over SOZ and adjacent regions in patients (n = 7) with refractory-epilepsy. Data was reviewed before and during 2 Hz cortical electrical stimulation. Group differences were estimated using ANOVA and correlation with Pearson's r.

RESULTS

CSCS reduced background ECoG power at SOZ (p < 0.05), increased spectral coherence (p < 0.05) and reduced spike rate (p < 0.01) over all recorded sites. Spectral power and coherence (p < 0.01) correlated with spike rate at SOZ but not with each other at any location. Spike morphology correlated with spike-rate over all recorded sites (p < 0.0001) and with spectral power and coherence at SOZ (p < 0.01).

CONCLUSION

This study shows changes in cortical electrophysiology during CSCS over the SOZ where spike rate reduction correlated with two independent electrophysiological parameters, background power and coherence. These results suggest the possibility of a causal relationship between spectral power, coherence and interictal spikes which may be related to seizure rate.

SIGNIFICANCE

Improved understanding of the effect of electrical stimulation on epileptic tissue could suggest improvements in stimulation paradigms to reduce seizure frequency.

WONOEP APPRAISAL: The many facets of epilepsy networks

The brain is a complex system composed of networks of interacting elements, from genes to circuits, whose function (and dysfunction) is not derivable from the superposition of individual components. Epilepsy is frequently described as a network disease, but to date, there is no standardized framework within which network concepts applicable to all levels from genes to whole brain can be used to generate deeper insights into the pathogenesis of seizures or the associated morbidities. To address this shortcoming, the Neurobiology Commission of the International League Against Epilepsy dedicated a Workshop on Neurobiology of Epilepsy (XIV WONOEP 2017) with the aim of formalizing network concepts as they apply to epilepsy and to critically discuss whether and how such concepts could augment current research endeavors. Here, we review concepts and strategies derived by considering epilepsy as a disease of different network hierarchies that range from genes to clinical phenotypes. We propose that the concept of networks is important for understanding epilepsy and is critical for developing new study designs. These approaches could ultimately facilitate the development of novel diagnostic and therapeutic strategies.

Seizure detection: do current devices work? And when can they be useful?

PURPOSE OF REVIEW

The unpredictability and apparent randomness of epileptic seizures is one of the most vexing aspects of epilepsy. Methods or devices capable of detecting seizures may help prevent injury or even death and significantly improve quality of life. Here, we summarize and evaluate currently available, unimodal, or polymodal detection systems for epileptic seizures, mainly in the ambulatory setting.

RECENT FINDINGS

There are two broad categories of detection devices: EEG-based and non-EEG-based systems. Wireless wearable EEG devices are now available both in research and commercial arenas. Neuro-stimulation devices are currently evolving and initial experiences of these show potential promise. As for non-EEG devices, different detecting systems show different sensitivity according to the different patient and seizure types. Regardless, when used in combination, these modalities may complement each other to increase positive predictive value. Although some devices with high sensitivity are promising, practical widespread use of such detection systems is still some way away. More research and experience are needed to evaluate the most efficient and integrated systems, to allow for better approaches to detection and prediction of seizures. The concept of closed-loop systems and prompt intervention may substantially improve quality of life for patients and carers.

Deep brain stimulation for refractory temporal lobe epilepsy: a systematic review and meta-analysis with an emphasis on alleviation of seizure frequency outcome

OBJECTIVE

Conflicting conclusions have been reported regarding predictors of deep brain stimulation (DBS) outcome in patients with refractory temporal lobe epilepsy (TLE). The main goal of this meta-analysis study was to identify possible predictors of remarkable seizure reduction (RSR).

METHODS

We conducted a comprehensive search of English-language literature published since 1990 and indexed in PubMed, Embase, and the Cochrane Library that addressed seizure outcomes in patients who underwent DBS for refractory TLE. A pooled RSR rate was determined for eight included studies. RSR rates were analyzed relative to potential prognostic variables. Random- or fixed-effects models were used depending on the presence or absence of heterogeneity.

RESULTS

The pooled RSR rate among 61 DBS-treated patients with TLE from 8 studies was 59%. Higher likelihood of RSR was found to be associated with lateralization of stimulation, lateralized ictal EEG findings, and a longer follow-up period. Seizure semiology, MRI abnormalities, and patient sex were not predictive of RSR rate. The best electrode type for RSR was the Medtronic 3389. Hippocampal and anterior thalamic nuclei (ATN) sites of stimulation had similar odds of producing RSR.

CONCLUSIONS

DBS is an effective therapeutic modality for intractable TLE, particularly in patients with lateralized EEG abnormalities and in patients treated on the ictal side. This meta-analysis provides evidence-based information for determining DBS suitability in presurgical counseling and for explaining seizure outcomes.

Epilepsy Treatment: A Futurist View

Advances in epilepsy treatment are occurring at a rapid pace, and it is challenging for us to keep up with the latest in our field. As we struggle to keep up with the literature and concentrate on our own research and clinical work, we often fail to exercise our imagination and envision what our field will be like in future decades. This was the assignment to the speakers for the Presidential Symposium at the 2016 American Epilepsy Society Annual Meeting. I challenged the experts to step outside the frame of their usual daily work to imagine what epilepsy treatment would and should look like for the next generation of epilepsy specialists and their patients. As you will read in the following sections, the speakers truly stepped up to the challenge to look into the crystal ball. The following are summaries of each lecture that describe the current state, existing cutting edge ideas, and some surprising predictions for the future. I am grateful for the tremendous effort these experts put into this challenge and hope they stimulate your imagination so you will work to bring these advances to our patients.