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Objective: The beneficial effects of thalamic deep brain stimulation (DBS) at various target sites in treating chronic central neuropathic pain (CPSP) remain unclear. This study aimed to evaluate the effectiveness of DBS at a previously untested target site in the central lateral (CL) thalamus, together with classical sensory thalamic stimulation (ventral posterior [VP] complex)., Materials and Methods: We performed a monocentric retrospective study of a consecutive series of six patients with CPSP who underwent combined DBS lead implantation of the CL and VP. Patient-reported outcome measures were recorded before and after surgery using the numeric rating scale (NRS), short-form McGill pain questionnaire (sf-MPQ), EuroQol 5-D quality-of-life questionnaire, and Beck Depression Inventory. DBS leads were reconstructed and projected onto a three-dimensional stereotactic atlas., Results: NRS-but not sf-MPQ-rated pain intensity-was significantly reduced throughout the follow-up period of 12 months compared with baseline (p = 0.005, and p = 0.06 respectively, Friedman test). At the last available follow-up (12 to 30 months), three patients described a more than 50% reduction. Two of the three long-term responders were stimulated in the CL (1000 Hz, 90 μs, 3.5-5.0 mA), whereas the third preferred VP complex stimulation (50 Hz, 200 μs, 0.7-1.2 mA). No persistent procedure- or stimulation-associated side effects were noted., Conclusions: These preliminary findings suggest that DBS of the CL might constitute a promising alternative target in cases in which classical VP complex stimulation does not yield satisfactory postoperative pain reduction. The results need to be confirmed in larger, prospective series of patients., (Copyright © 2022 International Neuromodulation Society. Published by Elsevier Inc. All rights reserved.)

Objectives: This study aims to describe the state of literature regarding the use of intraoperative neurophysiological monitoring (IONM) during spinal cord stimulator surgery., Materials and Methods: A systematic review of the use of IONM during spinal cord stimulation (SCS) surgery was performed using the following three data bases: PubMed, Ovid MEDLINE, and Embase. Research techniques included systematic research following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol by Cochrane, and backward searching. Qualitative analysis of included articles was performed using the methodologic index for nonrandomized studies assessment tool. Direction of effect, consistency across studies, and cost-effectiveness were narratively synthesized., Results: A total of 15 records were identified through data base searching. All records used IONM methods under general anesthesia for guidance of epidural lead placement. IONM techniques used for determining lateralization in the found articles were compound muscle action potentials (CMAPs) (n = 8), somatosensory evoked potentials (SSEPs) (n = 3) or both (n = 4). Motor evoked potentials were used in three trials for neuroprotection purposes. Two studies were comparative, and 12 were noncomparative., Conclusions: We found a good body of level II evidence that using IONM during SCS surgery is a valid alternative to awake surgery and may even be superior regarding pain management, cost-effectiveness, and postoperative neurologic deficits. In direct comparison, the found evidence suggested using CMAP provided more consistently favorable results than using SSEP for midline placement of epidural leads under general anesthesia. Selection of IONM modality should be made on the basis of pathophysiology of disease, individual IONM experience, and the individual patient., Competing Interests: Conflict of Interest Janine-Ai Schlaeppi is a consultant for Abbott and Nevro. Claudio Pollo is cofounder of Aleva Neurotherapeutics and reports consultancy fees from Boston Scientific and Abbott in the field of deep brain stimulation. Raphael Schreen and Kathleen Seidel reported no conflict of interest. Stimulation parameters are listed as far as specified in the publication., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Objective: The aim of this feasibility study was to investigate the properties of median nerve somatosensory evoked potential (SEPs) recorded from segmented Deep Brain Stimulation (DBS) leads in the sensory thalamus (VP) and how they relate to clinical and anatomical findings., Methods: We analyzed four patients with central post-stroke pain and DBS electrodes placed in the VP. Median nerve SEPs were recorded with referential and bipolar montages. Electrode positions were correlated with thalamus anatomy and tractography-based medial lemniscus. Early postoperative clinical paresthesia mapping was performed by an independent pain nurse. Finally, we performed frequency and time-frequency analyses of the signals., Results: We observed differences of SEP amplitudes recorded along different directions in the VP. SEP amplitudes did not clearly correlate to both atlas-based anatomical position and fiber-tracking results of the medial lemniscus. However, the contacts of highest SEP amplitude correlated with the contacts of lowest effect-threshold to induce paraesthesia., Conclusions: SEP recordings from directional DBS leads offer additional information about the neurophysiological (re)organization of the sensory thalamus., Significance: Directional recordings of thalamic SEPs bear the potential to assist clinical decision-making in DBS for pain., Competing Interests: Conflict of interest None of the authors have potential conflicts of interest to be disclosed., (Copyright © 2023 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objectives: Subthalamic nucleus (STN) deep brain stimulation (DBS) programming in patients with Parkinson disease (PD) may be challenging, especially when using segmented leads. In this study, we integrated a previously validated probabilistic STN sweet spot into a commercially available software to evaluate its predictive value for clinically effective DBS programming., Materials and Methods: A total of 14 patients with PD undergoing bilateral STN DBS with segmented leads were included. A nonlinear co-registration of a previously defined probabilistic sweet spot onto the manually segmented STN was performed together with lead reconstruction and tractography of the corticospinal tract (CST) in each patient. Contacts were ranked (level and direction), and corresponding effect and side-effect thresholds were predicted based on the overlap of the volume of activated tissue (VTA) with the sweet spot and CST. Image-based findings were correlated with postoperative clinical testing results during monopolar contact review and chronic stimulation parameter settings used after 12 months., Results: Image-based contact prediction showed high interrater reliability (Cohen kappa 0.851-0.91). Image-based and clinical ranking of the most efficient ring level and direction of stimulation were matched in 72% (95% CI 57.0-83.3) and 65% (95% CI 44.9-81.2), respectively, across the whole cohort. The mean difference between the predicted and clinically observed effect thresholds was 0.79 ± 0.69 mA (p = 0.72). The median difference between the predicted and clinically observed side-effect thresholds was -0.5 mA (p < 0.001, Wilcoxon paired signed rank test)., Conclusions: Integration of a probabilistic STN functional sweet spot into a surgical programming software shows a promising capability to predict the best level and directional contact(s) as well as stimulation settings in DBS for PD and could be used to optimize programming with segmented lead technology. This integrated image-based programming approach still needs to be evaluated on a bigger data set and in a future prospective multicenter cohort., (Copyright © 2021 International Neuromodulation Society. Published by Elsevier Inc. All rights reserved.)

Background: Deep brain stimulation (DBS) programming of multicontact DBS leads relies on a very time-consuming manual screening procedure, and strategies to speed up this process are needed. Beta activity in subthalamic nucleus (STN) local field potentials (LFP) has been suggested as a promising marker to index optimal stimulation contacts in patients with Parkinson disease., Objective: In this study, we investigate the advantage of algorithmic selection and combination of multiple resting and movement state features from STN LFPs and imaging markers to predict three relevant clinical DBS parameters (clinical efficacy, therapeutic window, side-effect threshold)., Materials and Methods: STN LFPs were recorded at rest and during voluntary movements from multicontact DBS leads in 27 hemispheres. Resting- and movement-state features from multiple frequency bands (alpha, low beta, high beta, gamma, fast gamma, high frequency oscillations [HFO]) were used to predict the clinical outcome parameters. Subanalyses included an anatomical stimulation sweet spot as an additional feature., Results: Both resting- and movement-state features contributed to the prediction, with resting (fast) gamma activity, resting/movement-modulated beta activity, and movement-modulated HFO being most predictive. With the proposed algorithm, the best stimulation contact for the three clinical outcome parameters can be identified with a probability of almost 90% after considering half of the DBS lead contacts, and it outperforms the use of beta activity as single marker. The combination of electrophysiological and imaging markers can further improve the prediction., Conclusion: LFP-guided DBS programming based on algorithmic selection and combination of multiple electrophysiological and imaging markers can be an efficient approach to improve the clinical routine and outcome of DBS patients., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Objective: We aimed to demonstrate the feasibility of using motor evoked responses to intraoperative double-train stimulation to guide lead placement and matching of intraoperative contacts with postoperative electrode programming in spinal cord stimulation for pain performed under general anesthesia., Materials and Methods: The study included a series of 20 consecutive patients with refractory pain operated on under general anesthesia. Either percutaneous or paddle leads were implanted and positioned according to the intraoperative mapping results. Neurophysiologic mapping was performed with a double-train stimulation paradigm (intertrain interval of 60 milliseconds, three to five cathodal pulses with 0.5-millisecond pulse duration, and within-train interstimulus intervals of 2-4 milliseconds). The sites where dorsal column responses of the targeted dermatomes were detected were considered optimal for lead placement (intraoperative best contacts). Following spinal cord stimulator (SCS) lead placement, blinded postoperative programming of electrode contacts was matched with the intraoperative best contacts and the pain-paresthesia overlap for the trial phase. A binominal test was used as a statistical method; pre- and postoperative numeric rating scale (NRS) after three months was obtained., Results: A total of 15 patients underwent spinal cord stimulation trial for intractable pain. Of these, ten patients (66%) had a successful trial and received permanent implants; one patient had a successful trial but was never intended to be implanted because of her poor health condition; four patients (26%) had an unsuccessful trial, leading to trial electrode explantation; and five patients had already had an implant with percutaneous leads and therefore underwent electrode revision, of whom four patients received paddle leads. In 18 of the 20 operated patients (90%), we found a match between the best intraoperative contacts and the postoperatively programmed contacts (significantly better than chance, p = 8.2 × 10 -15 ). In 90% of the patients, a pain-paresthesia overlap of 100% was found. In the remaining two patients (10%), the postoperatively best programmed contacts were one contact away from the intraoperative neurophysiologic best contact. A mean preoperative NRS score of 8.2 (variance) and a mean follow-up NRS score after three months of 3.6 (variance) were obtained for all patients with implants., Conclusion: In this proof-of-concept study, we were able to demonstrate that SCS lead placement using a double-train stimulation paradigm performed under general anesthesia is a safe and feasible technique, offering reliable prediction of contacts for postoperative programming and excellent pain-paresthesia coverage., (Copyright © 2022 International Neuromodulation Society. Published by Elsevier Inc. All rights reserved.)

Objectives: Cerebral vasospasm is a severe and potentially lethal complication in patients with subarachnoid hemorrhage (SAH). Its pathogenesis is still not completely understood. The efficacy of current treatments, such as triple-H therapy or calcium channel blockers, is unsatisfactory, and a new therapy model would therefore be valuable. Electrical stimulation may have a considerable influence on cerebrovascular innervation. This systematic review gives an overview of the studies that have applied electrical stimulation in models of cerebral vasospasm., Materials and Methods: We performed a systematic review of the literature, searching PubMed and Ovid Embase with the keywords "electric stimulation," "cerebral vasospasm," "subarachnoid hemorrhage," "sympathetic," and "parasympathetic." Additional papers were identified from the reference lists of the articles identified in the literature search., Results: Increased cerebral blood flow (CBF) is a widely observed effect of spinal cord stimulation and sphenopalatine ganglion stimulation in models of physiological conditions or experimental cerebral vasospasm. Most studies were conducted in animals, 15 under physiological conditions and 11 in animals with SAH. Eight studies in humans were identified that examined the stimulation effect on CBF under physiological conditions. Only two studies looked at patients after SAH: one applied spinal cord stimulation (SCS) and the other transcutaneous electrical neurostimulation. Different mechanisms leading to stimulation-induced CBF increase that were discussed included "reversible functional sympathectomy," activation of brainstem vasomotor centers, involvement of central ascending pathways, release of neurohumoral factors, and interaction with sympathetic, parasympathetic, and trigeminal innervation. The results indicate that electrical stimulation is a promising procedure for prevention and treatment of cerebral vasospasm., Conclusion: Electrical stimulation, especially SCS and sphenopalatine ganglion stimulation, is a promising adjunct for existing therapies for vasospasm after SAH. Further experiments and prospective clinical studies are needed to establish its potential usefulness as a therapy or prevention option., (Copyright © 2022 International Neuromodulation Society. Published by Elsevier Inc. All rights reserved.)

Background: Brain sensing devices are approved today for Parkinson's, essential tremor, and epilepsy therapies. Clinical decisions for implants are often influenced by the premise that patients will benefit from using sensing technology. However, artifacts, such as ECG contamination, can render such treatments unreliable. Therefore, clinicians need to understand how surgical decisions may affect artifact probability., Objectives: Investigate neural signal contamination with ECG activity in sensing enabled neurostimulation systems, and in particular clinical choices such as implant location that impact signal fidelity., Methods: Electric field modeling and empirical signals from 85 patients were used to investigate the relationship between implant location and ECG contamination., Results: The impact on neural recordings depends on the difference between ECG signal and noise floor of the electrophysiological recording. Empirically, we demonstrate that severe ECG contamination was more than 3.2x higher in left-sided subclavicular implants (48.3%), when compared to right-sided implants (15.3%). Cranial implants did not show ECG contamination., Conclusions: Given the relative frequency of corrupted neural signals, we conclude that implant location will impact the ability of brain sensing devices to be used for "closed-loop" algorithms. Clinical adjustments such as implant location can significantly affect signal integrity and need consideration., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Deep Brain Stimulation of the posterior subthalamic area is an emergent target for the treatment of Essential Tremor. Due to the heterogeneous and complex anatomy of the posterior subthalamic area, it remains unclear which specific structures mediate tremor suppression and different side effects. The objective of the current work was to yield a better understanding of what anatomical structures mediate the different clinical effects observed during directional deep brain stimulation of that area. We analysed a consecutive series of 12 essential tremor patients. Imaging analysis and systematic clinical testing performed 4-6 months postoperatively yielded location, clinical efficacy and corresponding therapeutic windows for 160 directional contacts. Overlap ratios between individual activation volumes and neighbouring thalamic and subthalamic nuclei as well as individual fiber tracts were calculated. Further, we generated stimulation heatmaps to assess the area of activity and structures stimulated during tremor suppression and occurrence of side effects. Stimulation of the dentato-rubro-thalamic tract and the zona incerta was most consistently correlated with tremor suppression. Both individual and group analysis demonstrated a similar pattern of activation for tremor suppression and different sorts of side-effects. Unlike current clinical concepts, induction of spasms and paresthesia were not correlated with stimulation of the corticospinal tract and the medial lemniscus. Furthermore, we noticed a significant difference in the therapeutic window between the best and worst directional contacts. The best directional contacts did not provide significantly larger therapeutic windows than omnidirectional stimulation at the same level. Deep brain stimulation of the posterior subthalamic area effectively suppresses all aspects of ET but can be associated with concomitant side effects limiting the therapeutic window. Activation patterns for tremor suppression and side effects were similar and predominantly involved the dentato-rubro-thalamic tract and the zona incerta. We found no different activation patterns between different types of side effects and no clear correlation between structure and function. Future studies with use of more sophisticated modelling of activation volumes taking into account fiber heterogeneity and orientation may eventually better delineate these different clusters, which may allow for a refined targeting and programming within this area., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Directional deep brain stimulation (dDBS) of the subthalamic nucleus for Parkinson's disease (PD) increases the therapeutic window. However, empirical programming of the neurostimulator becomes more complex given the increasing number of stimulation parameters. A better understanding of dDBS is needed to improve therapy and help guide postoperative programming., Objective: To determine whether clinical effects of dDBS can be predicted in individual patients based on lead location and volume of tissue activated (VTA) modelling., Methods: We analysed a prospective series of 28 PD patients. Imaging analysis and systematic clinical testing performed 4-6 months postoperatively yielded location, clinical efficacy and corresponding therapeutic windows for 272 directional contacts. We calculated the corresponding VTAs to build a probabilistic stimulation map using voxel-wise statistical analysis., Results: We found a positive and statistically significant correlation between the overlap ratio of a patient's individual stimulation volume and the probabilistic map's sweet spot -defined as the 10% voxels with the highest clinical efficacy values (average Spearman's rho = 0.43, average p ≤ 0.036). Patients who had a larger therapeutic window with directional compared to omnidirectional stimulation had a larger distance between the electrode and the sweet spot centroid (average distances 2.3 vs. 1.5 mm, p = 0.0019)., Conclusion: Our analysis provides new insights into how the definition of a probabilistic sweet spot based on directional stimulation data and individual VTA modelling can be applied to predict clinically effective directional stimulation and help guide clinicians with the intricate postoperative DBS programming., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: Functional processes in the brain are segregated in both the spatial and spectral domain. Motivated by findings reported at the cortical level in healthy participants we test the hypothesis in the basal ganglia of Parkinson's disease patients that lower frequency beta band activity relates to motor circuits associated with the upper limb and higher beta frequencies with lower limb movements., Methods: We recorded local field potentials (LFPs) from the subthalamic nucleus using segmented "directional" DBS leads, during which patients performed repetitive upper and lower limb movements. Movement-related spectral changes in the beta and gamma frequency-ranges and their spatial distributions were compared between limbs., Results: We found that the beta desynchronization during leg movements is characterised by a strikingly greater involvement of higher beta frequencies (24-31 Hz), regardless of whether this was contralateral or ipsilateral to the limb moved. The spatial distribution of limb-specific movement-related changes was evident at higher gamma frequencies., Conclusion: Limb processing in the basal ganglia is differentially organised in the spectral and spatial domain and can be captured by directional DBS leads., Significance: These findings may help to refine the use of the subthalamic LFPs as a control signal for adaptive DBS and neuroprosthetic devices., (Copyright © 2019 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Background: Accurate interindividual comparability of deep brain stimulation (DBS) lead locations in relation to the surrounding anatomical structures is of eminent importance to define and understand effective stimulation areas. The objective of the current work is to compare the accuracy of the DBS lead localisation relative to the STN in native space with four recently developed three-dimensional subcortical brain atlases in the MNI template space. Accuracy is reviewed by anatomical and volumetric analysis as well as intraoperative electrophysiological data., Methods: Postoperative lead localisations of 10 patients (19 hemispheres) were analysed in each individual patient based on Brainlab software (native space) and after normalization into the MNI space and application of 4 different human brain atlases using Lead-DBS toolbox within Matlab (template space). Each patient's STN was manually segmented and the relation between the reconstructed lead and the STN was compared to the 4 atlas-based STN models by applying the Dice coefficient. The length of intraoperative electrophysiological STN activity along different microelectrode recording tracks was measured and compared to reconstructions in native and template space. Descriptive non-parametric statistical tests were used to calculate differences between the 4 different atlases., Results: The mean STN volume of the study cohort was 153.3 ± 40.3 mm3 (n = 19). This is similar to the STN volume of the DISTAL atlas (166 mm3; p = .22), but significantly larger compared to the other atlases tested in this study. The anatomical overlap of the lead-STN-reconstruction was highest for the DISTAL atlas (0.56 ± 0.18) and lowest for the PD25 atlas (0.34 ± 0.17). A total number of 47 MER trajectories through the STN were analysed. There was a statistically significant discrepancy of the electrophysiogical STN activity compared to the reconstructed STN of all four atlases (p < .0001)., Conclusion: Lead reconstruction after normalization into the MNI template space and application of four different atlases led to different results in terms of the DBS lead position relative to the STN. Based on electrophysiological and imaging data, the DISTAL atlas led to the most accurate display of the reconstructed DBS lead relative to the DISTAL-based STN., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

Introduction: Deep brain stimulation (DBS) nowadays is a well-established treatment of motor symptoms in Parkinson's disease. The subthalamic nucleus (STN) is a common target for DBS, because motor improvements have been shown to be superior to best medical therapy, if DBS electrodes have been appropriately positioned. DBS target identification can be assisted by MRI beyond structural imaging by spatially resolved measurement of T2-relaxation times (T2r)., Aim: We pose the question, whether T2r of the STN is linked to the severity of the disease and whether outcome of DBS may be correlated to an asymmetric manifestation of the disease. Further, we investigated if abnormal T2r in the STN may be predictive for outcome of DBS., Methods: Twelve patients underwent preoperative MR imaging including a multi echo relaxometry sequence (3 Tesla, Siemens Medical Systems, Erlangen, Germany) ahead of DBS. T2r were determined for STN, substantia nigra (SN), red nucleus (RN) and centrum semiovale (CSO). Unified Parkinson's disease Rating Scale (UPDRS) scores were tested before and after DBS. Patients' T2r and deduced values representing left-right asymmetry of measurements were correlated with UPDRS scores and measures for outcome of DBS. Furthermore, patients' T2r were compared with T2r measurements in 12 healthy controls (HC)., Results: Patients' T2r for SN (mean 45.4 ms ± 4.4 ms) and STN (mean 56.4 ms ± 3.8 ms) were significantly shorter than T2r in HCs for SN (mean 60.7 ± 4.6) and STN (mean 66.1 ms ± 4.0 ms). While no mean T2r asymmetry was found in the SN, patients' mean T2r for STN showed a weakened left-right correlation (Pearson correlation coefficient 0.19 versus 0.72 in HC) indicating asymmetric degeneration. T2r asymmetry was not linked to the more severely affected hemisphere. The respective lower T2r within the left or right target region was significantly correlated to the outcome in terms of UPDRS III improvement in "off" state (Pearson correlation 0.82 corresponding to p ≪ 0.01). Patients with T2r of STN lower than 50 ms showed no response to DBS in the UPDRS. The maximum T2r for SN correlated to the improvement between UPDRS "off" minus and "on" (Dopamine response) but failed to predict DBS outcome., Conclusions: The lower boundaries of T2r in the STN predict motor outcome in DBS. T2r asymmetry in the STN is not associated with increased clinical symptoms, but with response to therapy. Thus, patients with very low T2r may be inappropriate candidates for DBS.

Objective: To show that time-irreversible EEG signals recorded with intracranial electrodes during seizures can serve as markers of the epileptogenic zone., Methods: We use the recently developed method of mapping time series into directed horizontal graphs (dHVG). Each node of the dHVG represents a time point in the original intracranial EEG (iEEG) signal. Statistically significant differences between the distributions of the nodes' number of input and output connections are used to detect time-irreversible iEEG signals., Results: In 31 of 32 seizure recordings we found time-irreversible iEEG signals. The maximally time-irreversible signals always occurred during seizures, with highest probability in the middle of the first seizure half. These signals spanned a large range of frequencies and amplitudes but were all characterized by saw-tooth like shaped components. Brain regions removed from patients who became post-surgically seizure-free generated significantly larger time-irreversibilities than regions removed from patients who still had seizures after surgery., Conclusions: Our results corroborate that ictal time-irreversible iEEG signals can indeed serve as markers of the epileptogenic zone and can be efficiently detected and quantified in a time-resolved manner by dHVG based methods., Significance: Ictal time-irreversible EEG signals can help to improve pre-surgical evaluation in patients suffering from pharmaco-resistant epilepsies., (Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)

Purpose: A case is presented and a systematic review of the literature is provided to update our current knowledge of induction of fear by cortical stimulation., Methods: We present a case of refractory epilepsy associated with a lesion where fear could be induced by intraoperative electrical stimulation of the posterior inner part of the superior temporal gyrus. We performed a systematic review of the literature using PubMed with the key words "epilepsy AND emotion", "cortical stimulation AND emotion," and "human brain stimulation AND behavior"., Results: Intraoperative cortical stimulation of the inner part of the posterior superior temporal gyrus reliably induced fear and progressive screaming behavior. Stimulation through subdural grid electrodes did not induce this phenomenon. A systematic review of the literature identified fear induction by stimulation of different widespread cortical areas including the temporal pole, the insula, and the anterior cingulate cortex. The posterior part of the superior temporal gyrus has so far not been associated with fear induction after electrical stimulation., Conclusion: Although our observation suggests that this area of the brain could be part of a network involved in the elicitation of fear, dysfunction of this network induced by epilepsy could also explain the observed phenomenon. Electrophysiologic and imaging studies must be conducted to improve our understanding of the cortical networks forming the neuroanatomical substrate of higher brain functions and experiences such as fear., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Purpose: To study the clinical outcome in hippocampal deep brain stimulation (DBS) for the treatment of patients with refractory mesial temporal lobe epilepsy (MTLE) according to the electrode location., Methods: Eight MTLE patients implanted in the hippocampus and stimulated with high-frequency DBS were included in this study. Five underwent invasive recordings with depth electrodes to localize ictal onset zone prior to chronic DBS. Position of the active contacts of the electrode was calculated on postoperative imaging. The distances to the ictal onset zone were measured as well as atlas-based hippocampus structures impacted by stimulation were identified. Both were correlated with seizure frequency reduction., Results: The distances between active electrode location and estimated ictal onset zone were 11±4.3 or 9.1±2.3mm for patients with a >50% or <50% reduction in seizure frequency. In patients (N=6) showing a >50% seizure frequency reduction, 100% had the active contacts located <3mm from the subiculum (p<0.05). The 2 non-responders patients were stimulated on contacts located >3mm to the subiculum., Conclusion: Decrease of epileptogenic activity induced by hippocampal DBS in refractory MTLE: (1) seems not directly associated with the vicinity of active electrode to the ictal focus determined by invasive recordings; (2) might be obtained through the neuromodulation of the subiculum., (Copyright © 2013 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.)

This paper presents a new and original variational framework for atlas-based segmentation. The proposed framework integrates both the active contour framework, and the dense deformation fields of optical flow framework. This framework is quite general and encompasses many of the state-of-the-art atlas-based segmentation methods. It also allows to perform the registration of atlas and target images based on only selected structures of interest. The versatility and potentiality of the proposed framework are demonstrated by presenting three diverse applications: In the first application, we show how the proposed framework can be used to simulate the growth of inconsistent structures like a tumor in an atlas. In the second application, we estimate the position of nonvisible brain structures based on the surrounding structures and validate the results by comparing with other methods. In the final application, we present the segmentation of lymph nodes in the Head and Neck CT images, and demonstrate how multiple registration forces can be used in this framework in an hierarchical manner., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The objective of this study was to evaluate the efficiency and the effects of changes in parameters of chronic amygdala-hippocampal deep brain stimulation (AH-DBS) in mesial temporal lobe epilepsy (TLE). Eight pharmacoresistant patients, not candidates for ablative surgery, received chronic AH-DBS (130 Hz, follow-up 12-24 months): two patients with hippocampal sclerosis (HS) and six patients with non-lesional mesial TLE (NLES). The effects of stepwise increases in intensity (0-Off to 2 V) and stimulation configuration (quadripolar and bipolar), on seizure frequency and neuropsychological performance were studied. The two HS patients obtained a significant decrease (65-75%) in seizure frequency with high voltage bipolar DBS (≥1 V) or with quadripolar stimulation. Two out of six NLES patients became seizure-free, one of them without stimulation, suggesting a microlesional effect. Two NLES patients experienced reductions of seizure frequency (65-70%), whereas the remaining two showed no significant seizure reduction. Neuropsychological evaluations showed reversible memory impairments in two patients under strong stimulation only. AH-DBS showed long-term efficiency in most of the TLE patients. It is a valuable treatment option for patients who suffer from drug resistant epilepsy and who are not candidates for resective surgery. The effects of changes in the stimulation parameters suggest that a large zone of stimulation would be required in HS patients, while a limited zone of stimulation or even a microlesional effect could be sufficient in NLES patients, for whom the importance of the proximity of the electrode to the epileptogenic zone remains to be studied. Further studies are required to ascertain these latter observations., (Copyright © 2011 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.)

In patients with pharmacologically intractable epilepsy who are not eligible for surgery, deep brain stimulation is currently under evaluation as an alternative treatment. Optimal stimulation parameters, including high (HFS) versus low frequency (LFS) stimulation, are not well defined. Here, we report the effects of HFS (130 pulses per second, pps) and LFS (5pps) of the principal epileptogenic focus, in three patients with non-lesional temporal lobe epilepsy. HFS, but not LFS, was associated with a reduction of the interictal discharges and absence of seizures. HFS may be beneficial in patients with non-lesional temporal lobe epilepsy who are not surgical candidates.

Objective: To quantify the usefulness of the neuronal activity recorded on a standard microelectrode track to the subthalamic nucleus (STN) for the determination of the transition between the thalamus and the STN., Methods: The study is based on analysis of 689 extracelullar single units recorded on 70 tracks passing through the thalamus and the STN. Using four neuron parameters that were correlated with electrode depth, a quality index (QI) for each track was computed and compared with the subjective assessment by the electrophysiologist of the track quality., Results: Subjectively, the transition between the thalamus and the STN was detected in 49 tracks (usual track) and not detected on 21 tracks (unusual tracks). Objectively, spike frequency, cell burst index (BI), signal relative root mean square (RMS) and spike relative amplitude were correlated with electrode depth and used to compute track QI. The average QI index of usual and unusual tracks was 0.25 +/- 0.9 and 0.85 +/- 0.15 (mean +/- confidence interval at P < 0.001), respectively. In 20 patients, QI correlates with post-operative measurement of electrode length in the STN., Conclusion: These results demonstrate that simple statistical analysis taking into account the variation of single-unit characteristics with electrode depth can discriminate between useful and useless tracks for the determination of the STN localisation.