Search

Epilepsy surgery in genetic drug‐resistant epilepsy is a debated subject as more histological and molecular data are available. We retrospectively collected data from focal drug‐resistant epilepsy patients that underwent stereoelectroencephalography (SEEG) invasive recordings. Patients with nonlesional brain imaging or in whom a first epilepsy surgery failed to control seizures were selected. We computed and displayed the intracranial ictal onset activity pattern on structural imaging. Patients underwent epilepsy gene panel testing, next generation sequencing—NGS. Of 113 patients, 13 underwent genetic testing, and in 6 patients, a mechanistic target of rapamycin pathway gene germline mutation (mTOR) was identified. Brain imaging was nonlesional except for one patient in whom two abnormalities suggestive of focal cortical dysplasia (FCD) were found. Patients underwent tailored brain surgery based on SEEG data, tissue analysis revealed FCD and postsurgical outcome was favorable. Our findings are similar to previous case series suggesting that epilepsy surgery can be a treatment option in patients with mTOR pathway mutation. In patients with mTOR pathway mutation, the postsurgical outcome is favorable if complete resection of the epileptogenic zone is performed. Electrophysiological seizure onset patterns in FCDs associated with mTOR pathway mutations display low‐voltage fast activity as previously described. [ABSTRACT FROM AUTHOR]

Electrophysiological mapping (EM) using acute electrode probes is a common procedure performed during functional neurosurgery. Due to their constructive specificities, the EM probes are lagging in innovative enhancements. This work addressed complementing a clinically employed EM probe with carbonic and circumferentially segmented macrocontacts that are operable both for neurophysiological sensing ("recording") of local field potentials (LFP) and for test stimulation. This paper illustrates in-depth the development that is based on the direct writing of functional materials. The unconventional fabrication processes were optimized on planar geometry and then transferred to the cylindrically thin probe body. We report and discuss the constructive concept and architecture of the probe, characteristics of the electrochemical interface deduced from voltammetry and chronopotentiometry, and the results of in vitro and in vivo recording and pulse stimulation tests. Two- and three-directional macrocontacts were added on probes having shanks of 550 and 770 μm diameters and 10–23 cm lengths. The graphitic material presents a ~2.7 V wide, almost symmetric water electrolysis window, and an ultra-capacitive charge transfer. When tested with clinically relevant 150 μs biphasic current pulses, the interfacial polarization stayed safely away from the water window for pulse amplitudes up to 9 mA (135 μC/cm2). The in vivo experiments on adult rat models confirmed the high-quality sensing of LFPs. Additionally, the in vivo-prevailing increase in the electrode impedance and overpotential are discussed and modeled by an ionic mobility-reducing spongiform structure; this restricted diffusion model gives new applicative insight into the in vivo-uprisen stimulation overpotential. [ABSTRACT FROM AUTHOR]

IInvestigating cognitive brain functions using non-invasive electrophysiology can be challenging due to the particularities of the task-related EEG activity, the depth of the activated brain areas, and the extent of the networks involved. Stereoelectroencephalographic (SEEG) investigations in patients with drug-resistant epilepsy offer an extraordinary opportunity to validate information derived from non-invasive recordings at macro-scales. The SEEG approach can provide brain activity with high spatial specificity during tasks that target specific cognitive processes (e.g., memory). Full validation is possible only when performing simultaneous scalp SEEG recordings, which allows recording signals in the exact same brain state. This is the approach we have taken in 12 subjects performing a visualmemory task that requires the recognition of previously viewed objects. The intracranial signals on 965 contact pairs have been compared to 391 simultaneously recorded scalp signals at a regional and whole-brain level, using multivariate pattern analysis. The results show that the task conditions are best captured by intracranial sensors, despite the limited spatial coverage of SEEG electrodes, compared to the whole-brain non-invasive recordings. Applying beamformer source reconstruction or independent component analysis does not result in an improvement of the multivariate task decoding performance using surface sensor data. By analyzing a joint scalp and SEEG dataset, we investigated whether the two types of signals carry complementary information that might improve the machine-learning classifier performance. This joint analysis revealed that the results are driven by the modality exhibiting best individual performance, namely SEEG. [ABSTRACT FROM AUTHOR]

Recording from deep neural structures such as hippocampus noninvasively and yet with high temporal resolution remains a major challenge for human neuroscience. Although it has been proposed that deep neuronal activity might be recordable during cognitive tasks using magnetoencephalography (MEG), this remains to be demonstrated as the contribution of deep structures to MEG recordings may be too small to be detected or might be eclipsed by the activity of large‐scale neocortical networks. In the present study, we disentangled mesial activity and large‐scale networks from the MEG signals thanks to blind source separation (BSS). We then validated the MEG BSS components using intracerebral EEG signals recorded simultaneously in patients during their presurgical evaluation of epilepsy. In the MEG signals obtained during a memory task involving the recognition of old and new images, we identified with BSS a putative mesial component, which was present in all patients and all control subjects. The time course of the component selectively correlated with stereo‐electroencephalography signals recorded from hippocampus and rhinal cortex, thus confirming its mesial origin. This finding complements previous studies with epileptic activity and opens new possibilities for using MEG to study deep brain structures in cognition and in brain disorders. [ABSTRACT FROM AUTHOR]

Cognitive tasks are commonly used to identify brain networks involved in the underlying cognitive process. However, inferring the brain networks from intracranial EEG data presents several challenges related to the sparse spatial sampling of the brain and the high variability of the EEG trace due to concurrent brain processes. In this manuscript, we use a well-known facial emotion recognition task to compare three different ways of analyzing the contrasts between task conditions: permutation cluster tests, machine learning (ML) classifiers, and a searchlight implementation of multivariate pattern analysis (MVPA) for intracranial sparse data recorded from 13 patients undergoing presurgical evaluation for drug-resistant epilepsy. Using all three methods, we aim at highlighting the brain structures with significant contrast between conditions. In the absence of ground truth, we use the scientific literature to validate our results. The comparison of the three methods' results shows moderate agreement, measured by the Jaccard coefficient, between the permutation cluster tests and the machine learning [0.33 and 0.52 for the left (LH) and right (RH) hemispheres], and 0.44 and 0.37 for the LH and RH between the permutation cluster tests and MVPA. The agreement between ML and MVPA is higher: 0.65 for the LH and 0.62 for the RH. To put these results in context, we performed a brief review of the literature and we discuss how each brain structure's involvement in the facial emotion recognition task. [ABSTRACT FROM AUTHOR]

Direct electrical stimulation (DES) is considered to be the gold standard for mapping cortical function. A careful mapping of the eloquent cortex is key to successful resective or ablative surgeries, with a minimal postoperative deficit, for treatment of drug‐resistant epilepsy. There is accumulating evidence suggesting that not only local, but also remote activations play an equally important role in evoking clinical effects. By introducing a new intracranial stimulation paradigm and signal analysis methodology allowing to disambiguate EEG responses from stimulation artifacts we highlight the spatial extent of the networks associated with clinical effects. Our study includes 26 patients that underwent stereoelectroencephalographic investigations for drug‐resistant epilepsy, having 337 depth electrodes with 4,351 contacts sampling most brain structures. The routine high‐frequency electrical stimulation protocol for eloquent cortex mapping was altered in a subtle way, by alternating the polarity of the biphasic pulses in a train, causing the splitting the spectral lines of the artifactual components, exposing the underlying tissue response. By performing a frequency‐domain analysis of the EEG responses during DES we were able to capture remote activations and highlight the effect's network. By using standard intersubject averaging and a fine granularity HCP‐MMP parcellation, we were able to create local and distant connectivity maps for 614 stimulations evoking specific clinical effects. The clinical value of such maps is not only for a better understanding of the extent of the effects' networks guiding the invasive exploration, but also for understanding the spatial patterns of seizure propagation given the timeline of the seizure semiology. [ABSTRACT FROM AUTHOR]

Stereoelectroencephalography (SEEG) in children with intractable epilepsy presents particular challenges. Their thin and partially ossified cranium, specifically in the temporal area, is prone to fracture while attaching stereotactic systems to the head or stabilizing the head in robot's field of action. Postponing SEEG in this special population of patients can have serious consequences, reducing their chances of becoming seizure-free and impacting their social and cognitive development. This study demonstrates the safety and accuracy offered by a frameless personalized 3D printed stereotactic implantation system for SEEG investigations in children under 4 years of age. SEEG was carried out in a 3-year-old patient with drug-resistant focal epilepsy, based on a right temporal-perisylvian epileptogenic zone hypothesis. Fifteen intracerebral electrodes were placed using a StarFix patient-customized stereotactic fixture. The median lateral entry point localization error of the electrodes was 0.90 mm, median lateral target point localization error was 1.86 mm, median target depth error was 0.83 mm, and median target point localization error was 1.96 mm. There were no perioperative complications. SEEG data led to a tailored right temporal-insular-opercular resection, with resulting seizure freedom (Engel IA). In conclusion, patient-customized stereotactic fixtures are a safe and accurate option for SEEG exploration in young children. [ABSTRACT FROM AUTHOR]

Body awareness is the result of sensory integration in the posterior parietal cortex; however, other brain structures are part of this process. Our goal is to determine how the cingulate cortex is involved in the representation of our body. We retrospectively selected patients with drug‐resistant epilepsy, explored by stereo‐electroencephalography, that had the cingulate cortex sampled outside the epileptogenic zone. The clinical effects of high‐frequency electrical stimulation were reviewed and only those sites that elicited changes related to body perception were included. Connectivity of the cingulate cortex and other cortical structures was assessed using the h2 coefficient, following a nonlinear regression analysis of the broadband EEG signal. Poststimulation changes in connectivity were compared between two sets of stimulations eliciting or not eliciting symptoms related to body awareness (interest and control groups). We included 17 stimulations from 12 patients that reported different types of body perception changes such as sensation of being pushed toward right/left/up, one limb becoming heavier/lighter, illusory sensation of movement, sensation of pressure, sensation of floating or detachment of one hemi‐body. High‐frequency stimulation in the cingulate cortex (1 anterior, 15 middle, 1 posterior part) elicits body perception changes, associated with a decreased connectivity of the dominant posterior insula and increased coupling between other structures, located particularly in the nondominant hemisphere. [ABSTRACT FROM AUTHOR]

Presents a study which reported the successful carbidation of titanium in a layer forming on the surface of a titanium sample submitted to multipulse excimer laser treatment in methane at a slightly superatmospheric pressure. Background on titanium carbide; Description of the experimental setup; Results.

Proposes a new laser method for the deposition of high purity, hard fcc titanium nitride layers of unlimited thickness. Requisite for titanium nitride formation; Results of electron microscopy investigations.

Background/Objectives: To create an open-source method for reconstructing microelectrode recording (MER) and deep brain stimulation (DBS) electrode coordinates along multiple parallel trajectories with patient-specific DBS implantation platforms to facilitate DBS research. Methods: We combined the surgical geometry (extracted from WayPoint Planner), pre-/intra-/postoperative computed tomography (CT) and/or magnetic resonance (MR) images, and integrated them into the Analysis of Functional NeuroImages (AFNI) neuroimaging analysis environment using functions written in Python. Electrode coordinates were calculated from image-based electrode surfaces and recording trajectory depth values. Coordinates were translated into appropriate trajectories, and were tested for proximity to patient-specific or atlas-based anatomical structures. Final DBS electrode coordinates for 3 patient populations (ventral intermediate nucleus [VIM], subthalamic nucleus [STN], and globus pallidus pars interna [GPi]) were calculated. For STN cases, MER site coordinates were then analyzed to see whether they were inside or outside the STN. Results: Final DBS electrode coordinates were described for VIM, STN, and GPi patient populations. 115/169 (68%) STN MER sites were within 1 mm of the STN in AFNI’s Talairach and Tournoux (TT) atlas. Conclusions: DBStar is a robust tool kit for understanding the anatomical location and context of electrode locations, and can easily be used for imaging, behavioral, or electrophysiological analyses. [ABSTRACT FROM AUTHOR]

Objective Technology for localizing epileptogenic brain regions plays a central role in surgical planning. Recent improvements in acquisition and electrode technology have revealed that high-frequency oscillations ( HFOs) within the 80-500 Hz frequency range provide the neurophysiologist with new information about the extent of the epileptogenic tissue in addition to ictal and interictal lower frequency events. Nevertheless, two decades after their discovery there remain questions about HFOs as biomarkers of epileptogenic brain and there use in clinical practice. Methods In this review, we provide practical, technical guidance for epileptologists and clinical researchers on recording, evaluation, and interpretation of ripples, fast ripples, and very high-frequency oscillations. Results We emphasize the importance of low noise recording to minimize artifacts. HFO analysis, either visual or with automatic detection methods, of high fidelity recordings can still be challenging because of various artifacts including muscle, movement, and filtering. Magnetoencephalography and intracranial electroencephalography ( iEEG) recordings are subject to the same artifacts. Significance High-frequency oscillations are promising new biomarkers in epilepsy. This review provides interested researchers and clinicians with a review of current state of the art of recording and identification and potential challenges to clinical translation. [ABSTRACT FROM AUTHOR]

Cortical direct electrical stimulation (DES) is a method of brain mapping used during invasive presurgical evaluation of patients with intractable epilepsy. Intellectual auras like intrusive thoughts, also known as forced thinking (FT), have been reported during frontal seizures. However, there are few reports on FT obtained during DES in frontal cortex. We report three cases in which we obtained intrusive thoughts while stimulating the dorsolateral prefrontal cortex and the white matter in the prefrontal region. In order to highlight the effective connectivity that might explain this clinical response, we have analyzed cortico-cortical potentials evoked by single pulse electrical stimulation. [ABSTRACT FROM AUTHOR]

Background: The stereoelectroencephalographic (SEEG) implantation procedures still represent a challenge due to the intrinsic complexity of the method and the number of depth electrodes required. Objectives: We aim at designing and evaluating the accuracy of a custom stereotactic fixture based on the StarFix™ technology (FHC Inc., Bowdoin, ME) that significantly simplifies and optimizes the implantation of depth electrodes used in presurgical evaluation of patients with drug-resistant epilepsy. Methods: Fiducial markers that also serve as anchors for the fixture are implanted into the patient's skull prior to surgery. A 3D fixture model is designed within the surgical planning software, with the planned trajectories incorporated in its design, aligned with the patient's anatomy. The stereotactic fixture is built using 3D laser sintering technology based on the computer-generated model. Bilateral rectangular grids of guide holes orthogonal to the midsagittal plane and centered on the midcommissural point are incorporated in the fixture design, allowing a wide selection of orthogonal trajectories. Up to two additional grids can be accommodated for targeting structures where oblique trajectories are required. The frame has no adjustable parts, this feature reducing the risk of inaccurate coordinate settings while simultaneously reducing procedure time significantly. Results: We have used the fixture for the implantation of depth electrodes for presurgical evaluation of 4 patients with drug-resistant focal epilepsy, with nearly 2-fold reduction in the duration of the implantation procedure. We have obtained a high accuracy with a submillimetric mean positioning error of 0.68 mm for the anchor bolts placed at the trajectory entry point and 1.64 mm at target. Conclusions: The custom stereotactic fixture design greatly simplifies the planning procedure and significantly reduces the time in the operating room, while maintaining a high accuracy. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

An internal model for predictive saccades in frontal cortex was investigated by recording neurons in monkey frontal eye field (FEF) during an inferred motion task. Monkeys were trained to make saccades to the extrapolated position of a small moving target that was rendered temporarily invisible and whose trajectory was altered. On approximately two-thirds of the trials, monkeys made multiple saccades while the target was invisible. Primary saccades were correlated with extrapolated target position. Secondary saccades significantly reduced residual errors resulting from imperfect accuracy of the first saccade. These observations suggest that the second saccade was corrective. Because there was no visual feedback, corrective saccades could only be driven by an internally generated error signal. Neuronal activity in the frontal eye field was directionally tuned before both primary and secondary saccades. Separate subpopulations of cells encoded either saccade direction or direction error before the second saccade. These results suggest that FEF neurons encode the error after the first saccade, as well as the direction of the second saccade. Hence, FEF appears to contribute to detecting and correcting movement errors based on internally generated signals. [ABSTRACT FROM AUTHOR]

A long-standing issue concerning the executive function of the primate dorsolateral prefrontal cortex is how the activity of prefrontal neurons is linked to behavioral response selection. To establish a functional relationship between prefrontal memory fields and saccade target selection, we trained three macaque monkeys to make saccades to the remembered location of a visual cue in a delayed spatial match-to-sample saccade task. We electrically stimulated sites in the prefrontal cortex with subthreshold currents during the delay epoch while monkeys performed this task. Our results show that the artificially injected signal interacts with the neural activity responsible for target selection, biasing saccade choices either towards the receptive/movement field (RF/MF) or away from the RF/MF, depending on the stimulation site. These findings might reflect a functional link between prefrontal signals responsible for the selection bias by modulating the balance between excitation and inhibition in the competitive interactions underlying behavioral selection. [ABSTRACT FROM AUTHOR]

We investigated the internal representation of invisible moving targets using electrical microstimulation in the prefrontal cortex. Monkeys were trained to make saccades to the extrapolated position of a small moving target that was rendered invisible during part of its trajectory. Although the target was invisible, involuntary saccades were evoked by electrical microstimulation of the frontal eye field. Stimulation was applied at different times relative to the disappearance of the target while the monkey fixated. When stimulation was applied immediately after target disappearance, electrically evoked saccades were biased toward the starting point of the target trajectory. When stimulation was applied later in the trial, evoked saccades were biased toward the end of the trajectory. The bias in evoked saccade direction changed continuously overtime. The magnitude and statistical significance of the electrically evoked saccade deviation depended on the accuracy of the monkeys' voluntary saccades relative to the invisible target. The results suggest that covert tracking is accompanied by a continuously shifting saccade plan that moves along the target path. [ABSTRACT FROM AUTHOR]

Working memory involves transient storage of information and the ability to manipulate that information for short-range planning and prediction. The computational aspect of working memory can be probed using dynamic sensorimotor behavior requiring complex stimulus-response mappings. Such a transformation occurs when extrapolating the future location of a moving target that is rendered temporarily invisible. Estimating the trajectory of an invisible moving target requires encoding and storing several target features, including the direction and speed of motion. We trained monkeys to make saccades to the estimated position of invisible targets moving at various speeds. The activity of neurons in the frontal eye field (FEF) was consistently modulated according to the speed of target motion. A reconstruction algorithm showed that estimates of target speed based on FEF activity were similar to behavioral speed estimates. FEF may therefore be involved in updating an internal representation of target trajectory for predictive saccades. [ABSTRACT FROM AUTHOR]

To investigate the mechanisms of fixation disengagement and saccade initiation, we electrically stimulated the macaque frontal eye fields (FEF) while monkeys performed a visual fixation task. We tested the effect of introducing a temporal gap between fixation target offset and the onset of the electrical stimulus. We found that the duration of the gap had a pronounced effect on the probability of producing electrically evoked saccades at a given current level. The highest probability was found for gaps of 200 ms duration. There were also effects of gap duration on saccade latency and amplitude for most of the stimulation sites. The increase in saccade probability may be associated with lower current thresholds for evoking saccades. [ABSTRACT FROM AUTHOR]

Introduction: Transcranial magnetic stimulation (TMS) can induce speech arrest at 25 Hz repetitive TMS used for brain mapping in a population of epileptic patients scheduled for epilepsy surgery (Pascual-Leone1991). It is based on reversible temporal brain tissue lesion principle. There are date suggesting that speech arrest could offer information not only on dominant hemisphere but on spatial Brocca area localization in the brain (Jennum). Method: A total of 72 patients were evaluated for epilepsy surgery. An innovative Neuro MSD device was used for TMS studies. The maximum TMS output of this device is in the range of 0 to 4 Tesla (for iron core). The figure eight shaped stimulation coil and an iron cone shaped core were used for focalization. Motor threshold is the intensity of stimulation needed to induce contraction in thumb. This intensity was used to block Brocca area activity in digit span. Different word picture association tasks were used. Results: None of our patients presented postoperative permanent language deficits. We found that TMS not even block speech but elicit misjudgment of word picture association. It was categorized as wrong, late, slow or absent. Wernike area was more difficult to localize, but we found that there are different patterns depending on stimulus timing before, during and short after naming tasks which are presented. Discussion: Temporary lesions is comparable to current stimulation or Wada test and is obtained by TMS noninvasively. This is helpful during dominant hemisphere resection for epilepsy or other lesions. TMS blocks speech in most of subjects but not in all. Head motor primary area is mainly involved in speech arrest but real motor aphasia is rear and bilateral speech control is found mostly in reeducated left handed subjects. Conclusion: TMS is a noninvasive method of modulating cortex and is proper for study of language in humans. It can give information on hemispheric dominance a motor area localization. Standardized study could provide important insights on the organization of this function not explained by evolution theory. [ABSTRACT FROM AUTHOR]

Objectives: We aim at describing the surgical approaches for the implantation of perisylvian depth electrodes in patients with drug-resistant epilepsy. Based on a retrospective analysis of functional mapping using electrical stimulation in a population of patients, we aim at providing guidelines for targeting specific functional areas. Methods: In a population of 8 patients undergoing presurgical evaluation for drug-resistant epilepsy, we have implanted depth electrodes that are targeting the insular-opercular areas using three main approaches: a) orthogonal trans-opercular; b) parasagittal oblique anterior; c) parasagittal oblique posterior. Functional mapping using 50 Hz electrical stimulation is performed, and the results are co-registered across patients using FreeSurfer and Matlab scripts to provide combined insularopercular functional maps. Results: Perisylvian implantations (Fig 1a, patient 8) have been performed without complications, including parasagittal oblique trajectories (Fig. 1b). A number of 142 clinical symptoms evoked by electrical stimulation were co-registered across patients to create functional maps. Some symptoms showed a spatial segregation, as illustrated in the cortical surface reconstruction (Fig. 1c) and the inflated version (Fig. 1d). Conclusion: Targeting perisylvian structures using approaches guided by the functional maps contributes to the success of the SEEG investigations. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to evaluate the clinical accuracy of a new generation of custom stereotactic fixtures for placement of depth electrodes in stereo-EEG presurgical evaluation of patients with drug-resistant epilepsy. Methods: A newly designed custom stereotactic fixture based on the StarFix technology (FHC Inc, Bowdoin, ME) has been used for anchorless implantation of 101 depth electrodes (Integra, Plainsboro, NJ) in 13 patients undergoing presurgical evaluation for drug resistant epilepsy. The stereotactic fixture (a) incorporates tool guides, anchoring and structural elements whose location and geometry are calculated and optimized using algorithms implemented in Matlab (Mathworks, Natick, MA). DEETO (Arnulfo et al., 2015) software package was used to automatically detect the electrodes' contacts on post-implantation CT (b), therefore eliminating any subjectivity in calculating the targeting errors. Results: As a result of using custom geometry of the stereotactic platform, calculated through algorithms we have developed, the new design is optimized for each patient and streamlines the surgical procedures. The most important result characterizing platform's accuracy is the value of 1.75 mm for the mean lateral target localization error (c). Conclusions: Personalized stereotactic fixtures are a safe and accurate alternative to using robotic arm for the implantation of depth electrodes in patients undergoing presurgical evaluation for drug-resistant epilepsy. [ABSTRACT FROM AUTHOR]

Introduction: Minimally invasive techniques in epilepsy surgery offer many advantages to conventional surgery including addressability, cost reductions and a decrease in primary and secondary morbidity. (Quigg and Hardy, 2014) Radiofrequency thermocoagulation (RFTC) on the same depth electrodes used for diagnosis has been demonstrated to be safe and moderately effective (Guenot 2004, 2008, 2011; Catenoix 2008, 2015) although a limited number of centers have reported their series. We are presenting the initial results obtained in our center. Methods: eight patients received RFTC treatment at the end of their SEEG procedure from Jan. 2015 to April 2016. Lesions were produced between 2 contiguous contacts on depth electrodes (Dixi, Becancon, FR) implanted with custom (FHC Inc, Maine, USA) and standard (Leksell, Elekta, Stockholm, SW) stereotactic frames allowing reaching most difficult targets. A 50-V, 120-mA current was applied for 10 to 40 seconds to reach an estimated temperature of 78-82 C. Tissue impedance was monitored throughout the procedure. Contacts in the cortex showing low voltage fast activity or spike and wave activity at seizure onset were targeted. Prior physiologic responses obtained at direct electrical stimulation (DES) were an exclusion criteria. Lesions morphology was estimated at 3 months with post-procedure MRI. Results: 2 to 10 contact pairs were coagulated per procedure (6 patients had frontal epilepsy, 1 occipital and 1 opercular). 6 were MRI negative cases - classically not viewed as candidates for RFCT, while 2 showed a malformation of cortical development. Median follow-up was 6 months (range 1-15). 3 (37%) are seizure free (Engel I A), 4 (50%) experienced a significant improvement in either seizure frequency or seizure duration (Engel III) 2 of which after an initial seizure free period, while 1 (13%) obtained no benefit. No acute or long-term complications were registered. Conclusions: Our early experience, confirms the technique's safety profile and efficiency, even in a difficult non-lesional population. [ABSTRACT FROM AUTHOR]