Deep brain stimulation for epilepsy

Deep brain stimulation of thalamus for epilepsy

Neuromodulation (neurostimulation) is a relatively new and rapidly growing treatment for refractory epilepsy. Three varieties are approved in the US: vagus nerve stimulation (VNS), deep brain stimulation (DBS) and responsive neurostimulation (RNS). This article reviews thalamic DBS for epilepsy. Among many thalamic sub-nuclei, DBS for epilepsy has been targeted to the anterior nucleus (ANT), centromedian nucleus (CM), dorsomedial nucleus (DM) and pulvinar (PULV). Only ANT is FDA-approved, based upon a controlled clinical trial. Bilateral stimulation of ANT reduced seizures by 40.5% at three months in the controlled phase (p = .038) and 75% by 5 years in the uncontrolled phase. Side effects related to paresthesias, acute hemorrhage, infection, occasional increased seizures, and usually transient effects on mood and memory. Efficacy was best documented for focal onset seizures in temporal or frontal lobe. CM stimulation may be useful for generalized or multifocal seizures and PULV for posterior limbic seizures. Mechanisms of DBS for epilepsy are largely unknown, but animal work points to changes in receptors, channels, neurotransmitters, synapses, network connectivity and neurogenesis. Personalization of therapies, in terms of connectivity of the seizure onset zone to the thalamic sub- nucleus and individual characteristics of the seizures, might lead to improved efficacy. Many questions remain about DBS, including the best candidates for different types of neuromodulation, the best targets, the best stimulation parameters, how to minimize side effects and how to deliver current noninvasively. Despite the questions, neuromodulation provides useful new opportunities to treat people with refractory seizures not responding to medicines and not amenable to resective surgery.

Centromedian Nucleus of the Thalamus Deep Brain Stimulation for Genetic Generalized Epilepsy: A Case Report and Review of Literature

There is a paucity of treatment options for cognitively normal individuals with drug resistant genetic generalized epilepsy (GGE). Centromedian nucleus of the thalamus (CM) deep brain stimulation (DBS) may be a viable treatment for GGE. Here, we present the case of a 27-year-old cognitively normal woman with drug resistant GGE, with childhood onset. Seizure semiology are absence seizures and generalized onset tonic clonic (GTC) seizures. At baseline she had 4–8 GTC seizures per month and weekly absence seizures despite three antiseizure medications and vagus nerve stimulation. A multidisciplinary committee recommended off-label use of CM DBS in this patient. Over 12-months of CM DBS she had two GTC seizure days, which were in the setting of medication withdrawal and illness, and no GTC seizures in the last 6 months. There was no significant change in the burden of absence seizures. Presently, just two studies clearly document CM DBS in cognitively normal individuals with GGE or idiopathic generalized epilepsy (IGE) [in contrast to studies of cognitively impaired individuals with developmental and epileptic encephalopathies (DEE)]. Our results suggest that CM DBS can be an effective treatment for cognitively normal individuals with GGE and underscore the need for prospective studies of CM DBS.

Functional brain imaging in larval zebrafish for characterising the effects of seizurogenic compounds acting via a range of pharmacological mechanisms

BACKGROUND AND PURPOSE

Functional brain imaging using genetically encoded Ca2+ sensors in larval zebrafish is being developed for studying seizures and epilepsy as a more ethical alternative to rodent models. Despite this, few data have been generated on pharmacological mechanisms of action other than GABAA antagonism. Assessing larval responsiveness across multiple mechanisms is vital to test the translational power of this approach, as well as assessing its validity for detecting unwanted drug-induced seizures and testing antiepileptic drug efficacy.

EXPERIMENTAL APPROACH

Using light-sheet imaging, we systematically analysed the responsiveness of 4 days post fertilisation (dpf; which are not considered protected under European animal experiment legislation) transgenic larval zebrafish to treatment with 57 compounds spanning more than 12 drug classes with a link to seizure generation in mammals, alongside eight compounds with no such link.

KEY RESULTS

We show 4dpf zebrafish are responsive to a wide range of mechanisms implicated in seizure generation, with cerebellar circuitry activated regardless of the initiating pharmacology. Analysis of functional connectivity revealed compounds targeting cholinergic and monoaminergic reuptake, in particular, showed phenotypic consistency broadly mapping onto what is known about neurotransmitter-specific circuitry in the larval zebrafish brain. Many seizure-associated compounds also exhibited altered whole brain functional connectivity compared with controls.

CONCLUSIONS AND IMPLICATIONS

This work represents a significant step forward in understanding the translational power of 4dpf larval zebrafish for use in neuropharmacological studies and for studying the events driving transition from small-scale pharmacological activation of local circuits, to the large network-wide abnormal synchronous activity associated with seizures.

Toward Closed-Loop Electrical Stimulation of Neuronal Systems: A Review

Biological neuronal cells communicate using neurochemistry and electrical signals. The same phenomena also allow us to probe and manipulate neuronal systems and communicate with them. Neuronal system malfunctions cause a multitude of symptoms and functional deficiencies that can be assessed and sometimes alleviated by electrical stimulation. Our working hypothesis is that real-time closed-loop full-duplex measurement and stimulation paradigms can provide more in-depth insight into neuronal networks and enhance our capability to control diseases of the nervous system. In this study, we review extracellular electrical stimulation methods used in in vivo, in vitro, and in silico neuroscience research and in the clinic (excluding methods mainly aimed at neuronal growth and other similar effects) and highlight the potential of closed-loop measurement and stimulation systems. A multitude of electrical stimulation and measurement-based methods are widely used in research and the clinic. Closed-loop methods have been proposed, and some are used in the clinic. However, closed-loop systems utilizing more complex measurement analysis and adaptive stimulation systems, such as artificial intelligence systems connected to biological neuronal systems, do not yet exist. Our review promotes the research and development of intelligent paradigms aimed at meaningful communications between neuronal and information and communications technology systems, "dialogical paradigms," which have the potential to take neuroscience and clinical methods to a new level.

Electrical stimulation of the endopiriform nucleus attenuates epilepsy in rats by network modulation

OBJECTIVE

Neuromodulatory anterior thalamic deep brain stimulation (DBS) is an effective therapy for intractable epilepsy, but few patients achieve complete seizure control with thalamic DBS. Other stimulation sites may be considered for anti-seizure DBS. We investigated bilateral low-frequency stimulation of the endopiriform nuclei (LFS-EPN) to control seizures induced by intracortically implanted cobalt wire in rats.

METHODS

Chronic epilepsy was induced by cobalt wire implantation in the motor cortex unilaterally. Bipolar-stimulating electrodes were implanted into the EPN bilaterally. Continuous electroencephalography (EEG) was recorded using electrodes placed into bilateral motor cortex and hippocampus CA1 areas. Spontaneous seizures were monitored by long-term video-EEG, and behavioral seizures were classified based on the Racine scale. Continuous 1-Hz LFS-EPN began on the third day after electrode implantation and was controlled by a multi-channel stimulator. Stimulation continued until the rats had no seizures for three consecutive days.

RESULTS

Compared with the control and sham stimulation groups, the LFS-EPN group experienced significantly fewer seizures per day and the mean Racine score of seizures was lower due to fewer generalized seizures. Ictal discharges at the epileptogenic site had significantly reduced theta band power in the LFS-EPN group compared to the other groups.

INTERPRETATION

Bilateral LFS-EPN attenuates cobalt wire-induced seizures in rats by modulating epileptic networks. Reduced ictal theta power of the EEG broadband spectrum at the lesion site may be associated with the anti-epileptogenic mechanism of LFS-EPN. Bilateral EPN DBS may have therapeutic applications in human partial epilepsies.

Role of GABAB receptors in proepileptic and antiepileptic effects of an applied electric field in rat hippocampus in vitro

The mechanisms underlying antiepileptic effects of deep brain stimulation (DBS) are complex and poorly understood. Studies on the effects of applied electric fields on epileptic nervous tissue could enable future advances in DBS treatments. Applied electric fields are known to inhibit or enhance epileptic activity in vitro through direct effects on local neurons, but it is unclear whether trans-synaptic effects participate in such actions. The present study investigates, in an epileptic brain slice model, the influence of GABA_B receptor activation on excitatory and suppressive effects of a short-duration (10 ms) electric field in rat hippocampus. The results show that perfusion of the GABA_B receptor antagonist, CGP 55845 (2 μM), could abolish applied-field induced suppression of orthodromic-stimulus evoked epileptiform afterdischarge activity in the CA1 region. GABA_B receptor blockade was associated with an enhanced excitatory (proepileptic) effect of the applied field. However, the suppressive effect, observed in isolation using weak field stimuli, was left unchanged. The G-protein-activated inwardly rectifying K⁺ channel (GIRK) antagonist, tertiapin (30-50 nM), mimicked the effects of CGP 55845. The results suggest that the applied field activate (elements of) local interneurons to release GABA onto GABA_B receptors. The resulting activation of postsynaptic GIRK channels inhibits neuronal activity thereby dampening the direct stimulatory effect of the applied field. The study indicates that local-stimulus induced GABA_B receptor activation can serve a protective role under antiepileptic paradigms by preventing electrical stimulation from causing hyperexcitation.

Clinically indicated electrical stimulation strategies to treat patients with medically refractory epilepsy

Focal epilepsies represent approximately half of all diagnoses, and more than one-third of these patients are refractory to pharmacologic treatment. Although resection can result in seizure freedom, many patients do not meet surgical criteria, as seizures may be multifocal in origin or have a focus in an eloquent region of the brain. For these individuals, several U.S. Food and Drug Administration (FDA)-approved electrical stimulation paradigms serve as alternative options, including vagus nerve stimulation, responsive neurostimulation, and stimulation of the anterior nucleus of the thalamus. All of these are safe, flexible, and lead to progressive seizure control over time when used as an adjunctive therapy to antiepileptic drugs. Focal epilepsies frequently involve significant comorbidities such as cognitive decline. Similar to antiepilepsy medications and surgical resection, current stimulation targets and parameters have yet to address cognitive impairments directly, with patients reporting persistent comorbidities associated with focal epilepsy despite a significant reduction in the number of their seizures. Although low-frequency theta oscillations of the septohippocampal network are critical for modulating cellular activity and, in turn, cognitive processing, the coordination of neural excitability is also imperative for preventing seizures. In this review, we summarize current FDA-approved electrical stimulation paradigms and propose that theta oscillations of the medial septal nucleus represent a novel neuromodulation target for concurrent seizure reduction and cognitive improvement in epilepsy. Ultimately, further advancements in clinical neurostimulation strategies will allow for the efficient treatment of both seizures and comorbidities, thereby improving overall quality of life for patients with epilepsy.

Stimulation and Neuromodulation in the Treatment of Epilepsy

Invasive brain stimulation technologies are allowing the improvement of multiple neurological diseases that were non-manageable in the past. Nowadays, this technology is widely used for movement disorders and is undergoing multiple clinical and basic science research for development of new applications. Epilepsy is one of the conditions that can benefit from these emerging technologies. The objective of this manuscript is to review literature about historical background, current principles and outcomes of available modalities of neuromodulation and deep brain stimulation in epilepsy patients.

Post-Traumatic, Drug-Resistant Epilepsy and Review of Seizure Control Outcomes from Blinded, Randomized Controlled Trials of Brain Stimulation Treatments for Drug-Resistant Epilepsy

Background: Many post-traumatic epilepsy (PTE) patients become resistant to medications. Nervous stimulation as a treatment for drug-resistant epilepsy (DRE) is an active area of clinical investigation.

Objective: To summarize methods, reported seizure control outcome measures, and adverse events from blinded, randomized control trials (RCTs) for selected invasive brain stimulation (IBS) and non-invasive brain stimulation (NIBS) treatment options in patients with DRE.

Methods: PubMed was searched for articles from 1995-2014, using search terms related to the topics of interest. Available relevant articles reporting the outcomes of interest were identified and data was extracted. Articles in the reference lists of relevant articles and clinicaltrials.gov were also referenced.

Results: Eleven articles were analyzed with a total of 795 patients identified. Studies showed that select nervous stimulation treatments significantly reduced seizure frequency in patients with DRE. 

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.

In vivo evaluation of the dentate gate theory in epilepsy

The dentate gyrus is a region subject to intense study in epilepsy because of its posited role as a 'gate', acting to inhibit overexcitation in the hippocampal circuitry through its unique synaptic, cellular and network properties that result in relatively low excitability. Numerous changes predicted to produce dentate hyperexcitability are seen in epileptic patients and animal models. However, recent findings question whether changes are causative or reactive, as well as the pathophysiological relevance of the dentate in epilepsy. Critically, direct in vivo modulation of dentate 'gate' function during spontaneous seizure activity has not been explored. Therefore, using a mouse model of temporal lobe epilepsy with hippocampal sclerosis, a closed-loop system and selective optogenetic manipulation of granule cells during seizures, we directly tested the dentate 'gate' hypothesis in vivo. Consistent with the dentate gate theory, optogenetic gate restoration through granule cell hyperpolarization efficiently stopped spontaneous seizures. By contrast, optogenetic activation of granule cells exacerbated spontaneous seizures. Furthermore, activating granule cells in non-epileptic animals evoked acute seizures of increasing severity. These data indicate that the dentate gyrus is a critical node in the temporal lobe seizure network, and provide the first in vivo support for the dentate 'gate' hypothesis.

Concise Review: Prospects of Bone Marrow Mononuclear Cells and Mesenchymal Stem Cells for Treating Status Epilepticus and Chronic Epilepsy

Mononuclear cells (MNCs) and mesenchymal stem cells (MSCs) derived from the bone marrow and other sources have received significant attention as donor cells for treating various neurological disorders due to their robust neuroprotective and anti-inflammatory effects. Moreover, it is relatively easy to procure these cells from both autogenic and allogenic sources. Currently, there is considerable interest in examining the usefulness of these cells for conditions such as status epilepticus (SE) and chronic epilepsy. A prolonged seizure activity in SE triggers neurodegeneration in the limbic brain areas, which elicits epileptogenesis and evolves into a chronic epileptic state. Because of their potential for providing neuroprotection, diminishing inflammation and curbing epileptogenesis, early intervention with MNCs or MSCs appears attractive for treating SE as such effects may restrain the development of chronic epilepsy typified by spontaneous seizures and learning and memory impairments. Delayed administration of these cells after SE may also be useful for easing spontaneous seizures and cognitive dysfunction in chronic epilepsy. This concise review evaluates the current knowledge and outlook pertaining to MNC and MSC therapies for SE and chronic epilepsy. In the first section, the behavior of these cells in animal models of SE and their efficacy to restrain neurodegeneration, inflammation, and epileptogenesis are discussed. The competence of these cells for suppressing seizures and improving cognitive function in chronic epilepsy are conferred in the next section. The final segment ponders issues that need to be addressed to pave the way for clinical application of these cells for SE and chronic epilepsy.

Cerebellar Directed Optogenetic Intervention Inhibits Spontaneous Hippocampal Seizures in a Mouse Model of Temporal Lobe Epilepsy

Epilepsy is a condition of spontaneous recurrent seizures. Current treatment options for epilepsy can have major negative side effects and for many patients fail to control seizures. We detected seizures on-line and tested a new selective intervention using a mouse model of temporal lobe epilepsy.

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Non-pharmacologic management of epilepsy

Non pharmacological treatment, in addition to pharmacological treatment is indicated in patients with refractory/pharmacoresistant epilepsy and includes ketogenic diet, deep brain stimulator, vagal nerve stimulator, transcranial magnetic stimulation and epilepsy surgery. Ketogenic diet has been recommended since 1921 and has been proved to be a safe and effective treatment for intractable epilepsy. Deep brain stimulator, has been used in the treatment of movement disorders for many years and recently been tried in the treatment of pharmacoresistant epilepsy. Vagus nerve stimulator is increasingly being used as an effective seizure aborting technique in patients not responding to anticonvulsants. Transcranial magnetic stimulation is a noninvasive brain stimulation technique which is being increasingly researched for use in patients with medication-refractory seizures who are not suitable candidates for surgery. Evolution of epilepsy surgery including Vagal nerve stimulator and Deep brain stimulator, as a successful treatment modality for intractable epilepsy has been influenced over the last decade by substantial advancement in imaging and operative/device related technology. The current article reviews the indications, mechanism of action, technological aspects and efficacy of the aforementioned modalities in the treatment of intractable/pharmacoresistant epilepsy in pediatric age group.

Electrical brain stimulation for epilepsy

Neurostimulation enables adjustable and reversible modulation of disease symptoms, including those of epilepsy. Two types of brain neuromodulation, comprising anterior thalamic deep brain stimulation and responsive neurostimulation at seizure foci, are supported by Class I evidence of effectiveness, and many other sites in the brain have been targeted in small trials of neurostimulation therapy for seizures. Animal studies have mainly assisted in the identification of potential neurostimulation sites and parameters, but much of the clinical work is only loosely based on fundamental principles derived from the laboratory, and the mechanisms by which brain neurostimulation reduces seizures remain poorly understood. The benefits of stimulation tend to increase over time, with maximal effect seen typically 1-2 years after implantation. Typical reductions of seizure frequency are approximately 40% acutely, and 50-69% after several years. Seizure intensity might also be reduced. Complications from brain neurostimulation are mainly associated with the implantation procedure and hardware, including stimulation-related paraesthesias, stimulation-site infections, electrode mistargeting and, in some patients, triggered seizures or even status epilepticus. Further preclinical and clinical experience with brain stimulation surgery should lead to improved outcomes by increasing our understanding of the optimal surgical candidates, sites and parameters.