Focal Epileptic Activity Research Articles

Penı̇sı̇lı̇n ile Oluşturulan Deneysel Epilepsi Modelinde Seftrı̇aksonun Etkı̇sı̇: Elektrofı̇zyolojı̇k Bı̇r Çalışma

Introduction: Epilepsy is a set of chronic neurological disorders characterized by seizures associated with abnormal and uncontrolled neuronal activity of the brain. Glutamate is the main excitatory neurotransmitter in the central nervous system. Excitatory amino acid transporter-2 (EAAT2), one of the major glutamate transporters, is responsible for total glutamate intake. Ceftriaxone is a β-lactam antibiotic that increases EAAT-2 expression and functional activity. This study aims to investigate the effects of ceftriaxone on penicillin-induced epileptiform activity by using electrocorticography (ECoG) in anesthetized rats.
 Materials and Methods: In this study, 35 Wistar male rats were used. The rats were divided into five groups of 7. In group 1, 2.5 μL 500 IU of penicillin intracranially (i.c.) and 1 ml saline solution and intraperitoneally (i.p.) were given, respectively. In group 2, 200 mg/kg, i.p. of ceftriaxone was administered 30 minutes after penicillin. In group 3, 400 mg/kg of ceftriaxone was administered i.p. 30 minutes after penicillin. 500 mg/kg of sodium valproate was administered i.p. following 30 minutes of penicillin in group 4. In group 5, 400 mg/kg, i.p. of ceftriaxone and 500 mg/kg, i.p. of sodium valproate were administered 30 minutes after penicillin. The rats were placed in a stereotaxic device after the procedure, and electrocorticogram recordings were captured for 180 minutes.
 Results: The acute treatment of ceftriaxone reduced spike-wave frequency and spike-wave amplitude of penicillin-induced epileptiform activity in the rats. 
 Conclusion: These findings suggest that acute ceftriaxone had an anticonvulsant effect on penicillin-induced focal onset epileptic activity. Ceftriaxone may has an anti-epileptogenic potential.

Interaction of interictal epileptiform activity with sleep spindles is associated with cognitive deficits and adverse surgical outcome in pediatric focal epilepsy.

Temporal coordination between oscillations enables intercortical communication and is implicated in cognition. Focal epileptic activity can affect distributed neural networks and interfere with these interactions. Refractory pediatric epilepsies are often accompanied by substantial cognitive comorbidity, but mechanisms and predictors remain mostly unknown. Here, we investigate oscillatory coupling across large-scale networks in the developing brain. We analyzed large-scale intracranial electroencephalographic recordings in children with medically refractory epilepsy undergoing presurgical workup (n = 25, aged 3-21 years). Interictal epileptiform discharges (IEDs), pathologic high-frequency oscillations (HFOs), and sleep spindles were detected. Spatiotemporal metrics of oscillatory coupling were determined and correlated with age, cognitive function, and postsurgical outcome. Children with epilepsy demonstrated significant temporal coupling of both IEDs and HFOs to sleep spindles in discrete brain regions. HFOs were associated with stronger coupling patterns than IEDs. These interactions involved tissue beyond the clinically identified epileptogenic zone and were ubiquitous across cortical regions. Increased spatial extent of coupling was most prominent in older children. Poor neurocognitive function was significantly correlated with high IED-spindle coupling strength and spatial extent; children with strong pathologic interactions additionally had decreased likelihood of postoperative seizure freedom. Our findings identify pathologic large-scale oscillatory coupling patterns in the immature brain. These results suggest that such intercortical interactions could predict risk for adverse neurocognitive and surgical outcomes, with the potential to serve as novel therapeutic targets to restore physiologic development.

Study of the Potential of MRI (Magnetic Resonance Imaging) in Detecting Epileptogenic Zones in the Brain

The epileptogenic zone is an area of the brain that is a source of uncontrolled epileptic activity. MRI can produce images of the brain with high spatial resolution, allowing detailed visualization of brain structure. This allows identification of pathological changes, such as lesions, hemorrhages, or vascular malformations, that may be a cause or indicator of an epileptogenic zone. MRI offers a variety of scanning techniques, including structural MRI (T1-weighted and T2-weighted), diffusion MRI, functional MRI (fMRI), and proton spectroscopy MRI. The literature search process was carried out on various databases (PubMed, Web of Sciences, EMBASE, Cochrane Libraries, and Google Scholar) regarding the potential of MRI (Magnetic Resonance Imaging) in detecting epileptogenic zones in the brain. This study follows the preferred reporting items for systematic reviews and meta-analysis (PRISMA) recommendations. MRI can produce images of the brain with high spatial resolution, allowing detailed identification of brain structures that may be associated with the epileptogenic zone. Lesions such as tumors, blood clots, or scar tissue that are the focus of epileptic activity can be clearly seen on MRI. Various MRI techniques, such as structural MRI, diffusion MRI, functional MRI, and proton spectroscopy MRI, can be used together to provide comprehensive information about the epileptogenic zone. MRI allows monitoring of brain structural changes over time, which is useful in determining the evolution of the epileptogenic zone. fMRI techniques help understand brain activity during epileptic attacks or as part of the epileptogenic zone.

Clinical and electroencephalographic features of epilepsy in patients with triple X syndrome: A case series

PurposeTriple X syndrome, is an often undiagnosed chromosomal abnormality with an incidence of 1/1000 females. Main associated disorders are urogenital malformations, premature ovarian failure or primary amenorrhea, gastrointestinal problems, psychiatric disorders and epilepsy. To date, triple X is not related to a specific epileptic syndrome. Therefore, the purpose of this clinical series is to analyze seizure semiology, electroencephalogram features and the long-term outcome of 13 patients with epilepsy and triple X syndrome. MethodsWe retrospectively evaluated the long-term seizure outcome in patients with triple X syndrome who had been referred to 11 Epilepsy Centers in Italy. A close electroclinical follow-up was made for at least 2 years and outcomes were reported. ResultsOur case series confirms that epilepsy is not an occasional finding but part of the phenotypic spectrum of this syndrome. The seizure semiology shows an higher prevalence of focal seizures in 62% of patients. EEG findings of focal epileptic activity were reported in 85% of patients. Anti-seizure medications were successful in all our patients whom in most cases were responsive to monotherapy. ConclusionAccording to our case series most successful drugs were VPA and LEV. Long term prognosis of epilepsy in our case series was good. Our experience suggests that all triple X patients achieve good seizure control and in 69% of cases normalization of the EEG.

Localized chemogenetic silencing of inhibitory neurons: a novel mouse model of focal cortical epileptic activity.

Focal cortical epilepsies are frequently refractory to available anticonvulsant drug therapies. One key factor contributing to this state is the limited availability of animal models that allow to reliably study focal cortical seizures and how they recruit surrounding brain areas in vivo. In this study, we selectively expressed the inhibitory chemogenetic receptor, hM4D, in GABAergic neurons in focal cortical areas using viral gene transfer. GABAergic silencing using Clozapine-N-Oxide (CNO) demonstrated reliable induction of local epileptiform events in the electroencephalogram signal of awake freely moving mice. Anesthetized mice experiments showed consistent induction of focal epileptiform-events in both the barrel cortex (BC) and the medial prefrontal cortex (mPFC), accompanied by high-frequency oscillations, a known characteristic of human seizures. Epileptiform-events showed propagation indication with favored propagation pathways: from the BC on 1 hemisphere to its counterpart and from the BC to the mPFC, but not vice-versa. Lastly, sensory whisker-pad stimulation evoked BC epileptiform events post-CNO, highlighting the potential use of this model in studying sensory-evoked seizures. Combined, our results show that targeted chemogenetic inhibition of GABAergic neurons using hM4D can serve as a novel, versatile, and reliable model of focal cortical epileptic activity suitable for systematically studying cortical ictogenesis in different cortical areas.

Study of the electrophysiological mechanisms of anticonvulsant action of the original levetiracetam analog the compound GIZH-290

The study used the method of cobalt epilepsy, which allows rats with long-term implanted electrodes in the cortical and subcortical structures of the brain to monitor the dynamics of the formation and migration of Epi-foci for a long time. It was found that in the control at the 1st stage of development of the Epi system, Epi activity is most pronounced in the electrocorticograms of the ipsilateral cortex, and at the 2nd, stable stage of development of the Epi system – in the contralateral cortex and subcortical structures. The compound GIZH-290 (the original structural analogue of levetiracetam) reduces the number of Epi discharges and their duration at the 2nd, stable stage of the development of the Epi system. The target structure of the GIZH – 290 compound was the hippocampus. The compound GIZH -290 selectively statistically significantly reduces both the number and duration of Epi – discharges only in the hippocampus and does not affect the foci of epileptic activity in the ipsi-and contralateral cortex and hypothalamus.

Phase Resetting in the Anterior Cingulate Cortex Subserves Childhood Attention and Is Impaired by Epilepsy.

The neural mechanisms that underlie selective attention in children are poorly understood. By administering a set-shifting task to children with intracranial electrodes stereotactically implanted within anterior cingulate cortex (ACC) for epilepsy monitoring, we demonstrate that selective attention in a set-shifting task is dependent upon theta-band phase resetting immediately following stimulus onset and that the preferred theta phase angle is predictive of reaction time during attentional shift. We also observe selective enhancement of oscillatory coupling between the ACC and the dorsal attention network and decoupling with the default mode network during task performance. When transient focal epileptic activity occurs around the time of stimulus onset, phase resetting is impaired, connectivity changes with attentional and default mode networks are abolished, and reaction times are prolonged. The results of the present work highlight the fundamental mechanistic role of oscillatory phase in ACC in supporting attentional circuitry and present novel opportunities to remediate attention deficits in children with epilepsy.

Bilateral epileptic networks in congenital and acquired corpus callosum defects: EEG-fMRI study

ObjectivesElectroencephalography-correlated functional magnetic resonance imaging (EEG-fMRI) allows imaging of brain-wide epileptic networks, and demonstrates that focal interictal epileptic activity is sometimes accompanied by bilateral functional activations. The corpus callosum (CC) facilitates bilateral spread of epileptic activity and at times targeted surgically for drug-resistant epilepsy (DRE). We hypothesized that focal epileptic networks are more unilateral in patients lacking intact CC. MethodsWe included focal DRE patients who underwent pre-surgical EEG-fMRI and had CC agenesis (group A, n = 5), patients who previously underwent anterior callosotomy as treatment for drop attacks and continued having seizures (group B, n = 6), and control group of patients with focal epilepsy and intact CC (group C, n = 9). Blood-oxygenation-level-dependent (BOLD) signal maps were generated for interictal epileptic discharges. To quantify bi-hemispheric distribution of epileptic networks, laterality indices were compared between groups. Anatomical and diffusion-weighted imaging demonstrated white matter pathways. Results96% of studies demonstrated bilateral activations. Laterality indices were similar in groups A and C, whereas group B demonstrated a more bilateral network than group C (p = 0.028). Diffusion-weighted and anatomical imaging showed aberrant white matter pathways and larger anterior commissure in groups A and B. 68% of studies showed maximal activation cluster concordant with the presumed epileptic focus, 28% showed non-maximal activation at presumed focus. SignificanceFocal epileptic activity is associated with bilateral functional activations despite lack of intact CC, and is associated with stronger contralateral activation in patients after anterior callosotomy compared to controls. These findings disprove our initial hypothesis, and combined with white matter structural imaging, may indicate that the CC is not a sole route of propagation of epileptic activity, which might spread via anterior commissure. Our study demonstrates the utility of EEG-fMRI in assessing epileptic networks and potentially aiding in tailoring surgical treatments in DRE patients with callosal anomalies, and in callosal surgeries.

Anticonvulsive effects of edaravone on penicillin-induced focal onset seizure model in the conscious rats.

Edaravone is a potent antioxidant and anti-inflammatory agent that is used in the clinic. The aim of the present study was to evaluate the chronic treatment effect of edaravone on penicillin-induced epileptiform activity. Twenty-eight Wistar rats were randomly divided into a total of four groups as penicillin control and edaravone pretreatment groups (1, 10, and 30mg/kg). Firstly, permanent electrodes for electrocorticography (ECoG) recording and canula for penicillin injection were placed as stereotactic under anesthesia. At the end of the recovery period, edaravone pretreatment groups received different doses of edaravone by intraperitoneal injection for 14 days and before 30-min penicillin microinjection. Epileptiform activity was induced by injecting 500 IU penicillin through the intracortical cannula. The effects of edaravone pretreatment on epileptiform activity were evaluated by using both electrophysiological and behavioral parameters. Edaravone pretreatment suppressed epileptiform activity by reducing the mean spike frequency and the behavior scores in ECoG recording. The results of the present study indicated that the use of chronic edaravone had an anticonvulsant effect on penicillin-induced focal onset epileptic activity. Edaravone had an anticonvulsant effect even at low doses.

Source imaging of deep-brain activity using the regional spatiotemporal Kalman filter

Background and objective: The human brain displays rich and complex patterns of interaction within and among brain networks that involve both cortical and subcortical brain regions. Due to the limited spatial resolution of surface electroencephalography (EEG), EEG source imaging is used to reconstruct brain sources and investigate their spatial and temporal dynamics. The majority of EEG source imaging methods fail to detect activity from subcortical brain structures. The reconstruction of subcortical sources is a challenging task because the signal from these sources is weakened and mixed with artifacts and other signals from cortical sources. In this proof-of-principle study we present a novel EEG source imaging method, the regional spatiotemporal Kalman filter (RSTKF), that can detect deep brain activity.Methods: The regional spatiotemporal Kalman filter (RSTKF) is a generalization of the spatiotemporal Kalman filter (STKF), which allows for the characterization of different regional dynamics in the brain. It is based on state-space modeling with spatially heterogeneous dynamical noise variances, since models with spatial and temporal homogeneity fail to describe the dynamical complexity of brain activity. First, RSTKF is tested using simulated EEG data from sources in the frontal lobe, putamen, and thalamus. After that, it is applied to non-averaged interictal epileptic spikes from a presurgical epilepsy patient with focal epileptic activity in the amygdalo-hippocampal complex. The results of RSTKF are compared to those of low-resolution brain electromagnetic tomography (LORETA) and of standard STKF.Results: Only RSTKF is successful in consistently and accurately localizing the sources in deep brain regions. Additionally, RSTKF shows improved spatial resolution compared to LORETA and STKF.Conclusions: RSTKF is a generalization of STKF that allows for accurate, focal, and consistent localization of sources, especially in the deeper brain areas. In contrast to standard source imaging methods, RSTKF may find application in the localization of the epileptogenic zone in deeper brain structures, such as mesial frontal and temporal lobe epilepsies, especially in EEG recordings for which no reliable averaged spike shape can be obtained due to lack of the necessary number of spikes required to reach a certain signal-to-noise ratio level after averaging.

Patterns of Functional Connectivity in the Brain in Temporal and Frontal Epilepsy

Objectives. To identify the pattern of functional connectivity (FC) between areas and networks in the brain in patients with frontal and temporal foci of epileptic activity. Materials and methods. A total of 43 patients aged 18–50 years with focal epilepsy – 32 with temporal epilepsy (TE) and 11 with frontal epilepsy (FE) – were studied. The control group consisted of 32 healthy subjects. The main method used in the study was brain MRI scans run using the epilepsy protocol and additionally including high-resolution structural images of the brain, along with resting-state fMRI. Results and conclusions. The most marked fMRI feature in patients with TE as compared with healthy subjects was a decrease in the FC of the insular cortex and the temporal opercula (the part of the temporal gyrus of each hemisphere overhanging the insula). In left-sided FE, the decrease on the left was significant. Increased FC in the dorsal part of the attention network on the left with the temporal and parietal areas of the cerebral cortex was specific for right-sided TE. TE also produced a decrease in FC between the anterior part of the cingulate gyrus and the basal ganglia. All significant results were linked with increases in FC in patients with FE as compared with healthy subjects, maximally in areas of the temporal cortex. Thus, the localization and lateralization of the focus of epileptic activity determine the pattern of FC in these areas and neural networks of the brain in patients with focal epilepsy.

Ictal Inhibition: Sync Globally, Slack Locally.

Role of Paroxysmal Depolarization in Focal Seizure Activity Tryba AK, Merricks EM, Lee S, et al. J Neuroph. 2019;122(5):1861-1873. doi.org/10.1152/jn.00392.2019We analyze the role of inhibition in sustaining focal epileptic seizure activity. We review ongoing seizure activity at the mesoscopic scale that can be observed with microelectrode arrays as well as at the macroscale of standard clinical electroencephalogram. We provide clinical, experimental, and modeling data to support the hypothesis that paroxysmal depolarization (PD) is a critical component of the ictal machinery. We present dual-patch recordings in cortical cultures showing reduced synaptic transmission associated with presynaptic occurrence of PD, and we find that the PD threshold is cell size related. We further find evidence that optically evoked PD activity in parvalbumin neurons can promote propagation of neuronal excitation in neocortical networks in vitro. Spike sorting results from microelectrode array measurements around ictal wave propagation in human focal seizures demonstrate a strong increase in putative inhibitory firing with an approaching excitatory wave, followed by a sudden reduction of firing at passage. At the macroscopic level, we summarize evidence that this excitatory ictal wave activity is strongly correlated with oscillatory activity across a centimeter-sized cortical network. We summarize Wilson–Cowan-type modeling showing how inhibitory function is crucial for this behavior. Our findings motivated us to develop a network motif of neurons in silico, governed by a reduced version of the Hodgkin–Huxley formalism, to show how feedforward, feedback, PD, and local failure of inhibition contribute to observed dynamics across network scales. The presented multidisciplinary evidence suggests that the PD not only is a cellular marker or epiphenomenon but actively contributes to seizure activity. NEW & NOTEWORTHY: We present mechanisms of ongoing focal seizures across meso- and macroscales of microelectrode array and standard clinical recordings, respectively. We find modeling, experimental, and clinical evidence for a dual role of inhibition across these scales: local failure of inhibition allows propagation of a mesoscopic ictal wave, whereas inhibition elsewhere remains intact and sustains macroscopic oscillatory activity. We present evidence for PD as a mechanism behind this dual role of inhibition in shaping ictal activity.

Cases with parietal and occipital lobe epilepsies

BackgroundFor seizures emerging from the posterior cortex it can be a challenge to differentiate if they belong to temporal, parietal or occipital epilepsies. Sensoric auras like visual phenomena may occur in all of these focal epilepsies. Ictal signs may mimic non- epileptic seizures.Case presentationsCase 1: Patient suffering from a pharmacoresistent focal epilepsy. Focal seizures with sudden visual disturbance, later during the seizure epigastric aura, vertigo-nausea, involvement to bilateral tonic-clonic seizures. MEG detected interictal spikes, source localization indicated focal epileptic activity parietal right.Case 2: Patient with focal pharmacoresistent epilepsy, semiology with focal unaware seizures, feeling that something like a coat is imposed from behind on him, then feeling cold over the whole body, goose bumbs from both arms to head, then block of motoric activity, later focal unaware seizures with stare gaze, blinking of eyes, clouding of consciousness, elevation of arms and legs, sometimes tonic-clonic convulsions. EEG/MEG source localization and MRI detected an epileptogenic lesion parietal left.Case 3: Patient with pharmacoresistent focal epilepsy, focal aware seizures, a dark spot occurring in the left visual field, sometimes anxiety during seizures (leading to the suspicion of non-epileptic psychogenic pseudo seizures). MRI demonstrated an atrophy occipito-temporal right after sinus vein thrombosis. Ictal video-EEG showed a focal seizure onset occipital right.ConclusionContribution of noninvasive and/or invasive confirmation of the localization of the underlying focal epileptic activity in posterior cortex is illustrated. Characteristics of posterior cortex epilepsies are ventilated.

Evidence for the Role of Magnetic Source Imaging in the Presurgical Evaluation of Refractory Epilepsy Patients.

Magnetoencephalography (MEG) in the field of epilepsy has multiple advantages; just like electroencephalography (EEG), MEG is able to measure the epilepsy specific information (i.e., the brain activity reflecting seizures and/or interictal epileptiform discharges) directly, non-invasively and with a very high temporal resolution (millisecond-range). In addition MEG has a unique sensitivity for tangential sources, resulting in a full picture of the brain activity when combined with EEG. It accurately allows to perform source imaging of focal epileptic activity and functional cortex and shows a specific high sensitivity for a source in the neocortex. In this paper the current evidence and practice for using magnetic source imaging of focal interictal and ictal epileptic activity during the presurgical evaluation of drug resistant patients is being reviewed.

Role of paroxysmal depolarization in focal seizure activity.

We analyze the role of inhibition in sustaining focal epileptic seizure activity. We review ongoing seizure activity at the mesoscopic scale that can be observed with microelectrode arrays as well as at the macroscale of standard clinical EEG. We provide clinical, experimental, and modeling data to support the hypothesis that paroxysmal depolarization (PD) is a critical component of the ictal machinery. We present dual-patch recordings in cortical cultures showing reduced synaptic transmission associated with presynaptic occurrence of PD, and we find that the PD threshold is cell size related. We further find evidence that optically evoked PD activity in parvalbumin neurons can promote propagation of neuronal excitation in neocortical networks in vitro. Spike sorting results from microelectrode array measurements around ictal wave propagation in human focal seizures demonstrate a strong increase in putative inhibitory firing with an approaching excitatory wave, followed by a sudden reduction of firing at passage. At the macroscopic level, we summarize evidence that this excitatory ictal wave activity is strongly correlated with oscillatory activity across a centimeter-sized cortical network. We summarize Wilson-Cowan-type modeling showing how inhibitory function is crucial for this behavior. Our findings motivated us to develop a network motif of neurons in silico, governed by a reduced version of the Hodgkin-Huxley formalism, to show how feedforward, feedback, PD, and local failure of inhibition contribute to observed dynamics across network scales. The presented multidisciplinary evidence suggests that the PD not only is a cellular marker or epiphenomenon but actively contributes to seizure activity.NEW & NOTEWORTHY We present mechanisms of ongoing focal seizures across meso- and macroscales of microelectrode array and standard clinical recordings, respectively. We find modeling, experimental, and clinical evidence for a dual role of inhibition across these scales: local failure of inhibition allows propagation of a mesoscopic ictal wave, whereas inhibition elsewhere remains intact and sustains macroscopic oscillatory activity. We present evidence for paroxysmal depolarization as a mechanism behind this dual role of inhibition in shaping ictal activity.

EEG changes in patients with intracranial tumors and seizures symptom at Mohammad Hoesin Hospital Palembang

This study was conducted to determine the EEG changes in intracranial tumor patients with symptoms of seizures and the correspondence between the location of tumor by the location of the EEG abnormality. This is a cross-sectional descriptive study using primary and secondary data. Samples were collected consecutively over a period of 1 year. Of the 35 samples, abnormal EEG in patients with primary intracranial tumors obtained 68,2%, whereas in metastatic intracranial tumors obtained in 84,6%. From the abnormal EEG, in primary intracranial tumors description focal slowing in 60.0%, epileptic activity 20.0%, accompanied focal epileptic activity and focal slowing in 13.3%. Whereas in patients with intracranial tumor metastasis overview the form of a focal slowing in 36.4%,epileptic activity in 18.2%, and deceleration focal epileptiform activity accompanied by 45.5%. Presence of the EEG abnormality locations in tumor area 23.1%, non-tumor area by 38.5%, tumor and non-tumor area area by 38.5%. In this study, most patients have an abnormal EEG which more common in the form of a focal slowing compared epileptic activity, and some abnormalities are located in non-tumor areas. This indicates that the seizures that occur may be more due to irritation lesions than for the formation of epileptic focus.

S12. Clinical and neurophysiological profile of adult epilepsy population of Bishkek

Introduction Aim of the study is to study clinical and neurophysiological profiles of epilepsy patients of Oktober district of Bishkek. Methods The study involved 430 patients with epilepsy during 2014–2016y from clinical neurology department of City Hospital and Family Medicine Centers of Oktober district of Bishkek. Results When evaluating EEG data, it was found that 153 (35.6%) patients had focal epileptic activity, while 107 (24.9%) had generalized. At the same time, 170 (39.5%) patients suffering from epilepsy performing EEG did not reveal any epileptic activity interictallly. In those patients who had epileptic foci in the routine EEG, they were most often recorded in the frontal (14.9% of the total sample size) and in the parieto-occipital region (9.1% of the total sample size). In the analysis of MRI, the lesions of the frontal, temporal and parietal lobes were simultaneously the most frequent (50 cases or 11.6%), moreover, changes were often detected in the medial divisions of the temporal lobe (20 cases or 4.7%). In 126 cases (29.3%) no changes were detected on the MRI. In 57 (13.2%) cases, neuroimaging was not performed. In the group of patients (153) with the focus established according to the EEG data, the greatest correlation (kA = 0.21) between the epileptic focus and the pathological focus on MRI images coincided for the frontal and frontal parietal areas. In the differential analysis of the structure of seizures, depending on the localization of epileptic focus on the EEG, partial seizures prevailed in various combinations (54.5%) in patients with temporo-parietal focus, in patients with all other areas EEG focuses most often were observed primary GTCS. Conclusion The above data clearly demonstrate that, despite the fact that MRI is an obligatory method of investigation in patients with epilepsy, in reality for citizens of Kyrgyzstan, MRI is often inaccessible, is only in private clinics and is costly. Therefore, it is necessary to equip state hospitals with modern MRI devices, which should be one of the priority directions for the development of domestic epileptology. Taking into account that in 39.5% of cases during routine EEG in the surveyed population, it was not possible to detect focal activity for the purpose of timely diagnosis and adequate therapy of AED in the absence of focal activity according to routine EEG data, it is necessary to perform 3 or 6 h video EEG monitoring.

Local Oscillatory Properties of the Dendritic Membrane of Hippocampal Pyramidal Neurons: a Simulation Study

Foci of epileptic activity, generated as a result of synchronization of periodic burst discharges in neuronal networks, are often localized in the hippocampus. Using a model approach, we investigated the possibility of and biophysical conditions for the appearance of local oscillatory processes in dendrites possessing voltage-dependent channels (which is typical of pyramidal neurons of the hippocampus). The study was performed on a computer model of the membrane with active conductivities inherent in dendrites of pyramidal neurons of the CA3 area. It was found that such a membrane compartment subjected to tonic synaptic excitatory influences can function as a local generator of stable depolarization of a low or a high level or as a generator producing membrane potential oscillations (local oscillator). Each of these modes corresponds to a certain range of the synaptic excitation intensity; with increasing temperature, the range within which the oscillator properties are manifested is narrowed, while the range within which high-level stable depolarization is generated is expanded.

Thalamic interictal epileptiform discharges in deep brainstimulated epilepsy patients.

The relationships between interictal epileptiform discharges (IEDs) in the anterior (ANT) and dorsomedial nuclei (DMNT) of the thalamus and electro-clinical parameters in pharmacoresistant focal epilepsy patients receiving intrathalamic electrodes for deep brain stimulation (DBS) were investigated. Thalamus-localized IEDs (LIEDs) and surface EEG (sEEG)-IEDs were evaluated in eight patients who underwent ANT-DBS. Occurrence and frequency of ANT- and DMNT-LIEDs and pre-operative sEEG-IEDs were examined with respect to seizure onset location and seizure outcome following ANT-DBS. LIEDs were identified in all eight patients, in the ANT, DMNT, or both. ANT-LIEDs were observed in all patients with an unequivocal temporal seizure onset zone. The ANT-LIED frequency correlated with pre-surgical sEEG-IED frequency (ρ=0.76, p=0.033) and predicted ANT-DBS responsiveness (T=-2.6; p=0.0428). Of the five patients with bilateral sEEG-IEDs, all had ANT-LIEDs, but only one patient had DMNT-LIEDs. All patients with no or unilateral sEEG-IEDs had DMNT-LIEDs. Observation of LIEDS in the ANT and DMNT supports the hypothesis that these nuclei are involved in propagation of focal epileptic activity. Their correspondence with differing electro-clinical features suggests that these nuclei are functionally distinguishable nodes within the epileptic networks of individual patients.

Identifying epileptic source location and extent: an iterative sparse electromagnetic source imaging algorithm.

In this paper we have introduced a novel electromagnetic source imaging (ESI) technique and demonstrated its validity and excellent performance in imaging the location and extent of underlying epileptic sources in patients suffering from focal epilepsy. The proposed algorithm employs ideas from sparse signal processing literature and convex optimization theories to improve source imaging results obtained from scalp-recorded electroencephalogram (EEG). EEG source imaging results generally use subjective methods to determine the extent of the underlying brain activity. The proposed technique provides significant improvement in dealing with such shortcomings and eliminates the need for thresholding. The results of our computer simulations and clinical validation study demonstrate the excellent performance of the proposed algorithm and suggest it may become a useful tool for objectively determining the location and extent of focal epileptic activity in a noninvasive fashion.