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Focal cortical lesions are known to result in large-scale functional alterations involving distant areas; however, little is known about the electrophysiological mechanisms underlying these network effects. Here, we addressed this issue by analysing the short and long distance intracranial effects of controlled structural lesions in humans. The changes in Stereo-Electroencephalographic (SEEG) activity after Radiofrequency-Thermocoagulation (RFTC) recorded in 21 epileptic subjects were assessed with respect to baseline resting wakefulness and sleep activity. In addition, Cortico-Cortical Evoked Potentials (CCEPs) recorded before the lesion were employed to interpret these changes with respect to individual long-range connectivity patterns. We found that small structural ablations lead to the generation and large-scale propagation of sleep-like slow waves within the awake brain. These slow waves match those recorded in the same subjects during sleep, are prevalent in perilesional areas, but can percolate up to distances of 60 mm through specific long-range connections, as predicted by CCEPs. Given the known impact of slow waves on information processing and cortical plasticity, demonstrating their intrusion and percolation within the awake brain add key elements to our understanding of network dysfunction after cortical injuries., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objective: We evaluated four imaging techniques, i.e. Electroencephalography (EEG)-functional Magnetic Resonance Imaging (MRI) (EEG-fMRI), High-resolution EEG (HR-EEG), Magnetoencephalography (MEG) and 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (PET), for the identification of the epileptogenic zone (EZ) in 41 patients with negative MRI, candidate to neurosurgery., Methods: For each technique, results were compared to the Stereo-EEG. Diagnostic measures were calculated with respect to the post-surgical outcome, either for all the patients (39/41, two patients excluded) and for the subgroup of patients with the EZ involving more than one lobe (20/41)., Results: When considered individually, each functional technique showed accuracy values ranging 54,6%-63,2%, having PET, MEG and HR-EEG higher sensitivity, and EEG-fMRI higher specificity. In patients with multilobar epileptogenic zone, functional techniques achieved the best accuracies (up to 80%) when three techniques, including EEG-fMRI, were considered together., Conclusions: The study highlights the accuracy of a combination of functional imaging techniques in the identification of EZ in MRI negative focal epilepsy. The best diagnostic yield was obtained if the combination of PET, MEG (or HR-EEG as alternative), EEG-fMRI were considered together., Significance: The functional imaging techniques may improve the presurgical workup of MRI negative focal epilepsy, if epileptogenic zone involves more than one lobe., Competing Interests: Declaration of Competing Interest None of the authors has any conflict of interest to disclose. We confirm that we have read the journal’s position on the issues involved in ethical publication, and affirm that this report is consistent with those guidelines., (Copyright © 2020 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Objective: Activity-dependent changes have been reported in animal models and in human epileptic specimens and could potentially be used as tissue biomarkers to evaluate the propensity of a tissue to generate seizure activity. In this context, cAMP-response element binding protein (CREB) activation was specifically reported in human epileptic foci and related mainly to interictal spike activity. To get further insights into CREB activation in human epilepsy, we analyzed pCREB expression on brain tissue samples from patients who underwent surgery for drug-resistant focal epilepsy, correlating this expression with intracranial stereo-electroencephalography (SEEG) recording in a subgroup., Methods: Neocortical specimens from patients with neuropathological diagnosis of no lesion (cryptogenic), malformations of cortical development,mainly type II focal cortical dysplasia (FCD), and hippocampi with and without hippocampal sclerosis have been analyzed by immunohistochemistry. Peritumoral cortex from non-epileptic patients and autoptic samples were used as controls, whereas rat brains were used to test possible loss of pCREB antigenicity due to fixation procedures and postmortem delay., Results: pCREB was consistently expressed in layer II neuronal nuclei in regions with normal cortical lamination both in epileptic and non-epileptic surgical tissues. In patients with SEEG recordings, this anatomical pattern was unrelated to the presence of interictal spike activity. Conversely, in the core of type II FCD, as well as in other developmental malformations, pCREB was scattered without any laminar specificity. Furthermore, quantitative data did not reveal significant differences between epileptic and non-epileptic tissues, except for an increased immunoreactivity in the core of type IIB FCD lesion related mainly to reactive glial and balloon cells., Significance: The present data argue against the reliability of pCREB immunohistochemistry as a marker of epileptic focus but underscores its layer-related expression, suggesting a potential application in the study of malformations of cortical development, a wide range of diseases arising from perturbations of normal brain development., (© 2020 International League Against Epilepsy.)

Objective: To analyze relationships between CD34 expression and several demographic, clinical, and pathologic features in patients with histopathologic evidence of low-grade epilepsy-associated tumors who underwent epilepsy surgery., Methods: A retrospective study enrolling 187 patients with low-grade epilepsy-associated tumors who underwent surgery between January 2009 and June 2015 at 8 Italian epilepsy surgery centers was conducted. All cases were histologically diagnosed according to the World Health Organization classification of central nervous system tumors. Univariate and multivariate analyses were performed to identify variables associated with CD34 expression., Results: Of 187 patients, 95 (50.8%) were CD34 positive. Tumor type and duration of epilepsy were independently associated with CD34 expression on multivariate analysis. Ganglioglioma and pleomorphic xanthoastrocytoma were the histologic types with the strongest association with CD34 positivity with an odds ratio of 9.2 and 10.4, respectively, compared with dysembryoplastic neuroepithelial tumors. Patients with a duration of epilepsy >10 years had a significantly greater likelihood to show CD34 expression, with an odds ratio of 2.8 compared with patients with a duration of epilepsy <2 years. On univariate analysis, CD34 expression appeared to be significantly related to older age at surgery, higher antiepileptic drug intake, and female sex., Conclusions: CD34 expression holds promise as a useful biomolecular marker for patients with low-grade epilepsy-associated tumors with evidence of a link with clinicopathologic features. This study confirmed the association between CD34 expression and tumor type and demonstrated a significantly higher probability of CD34 expression in patients with longer duration of epilepsy, independent of histology., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Sleep-related hypermotor epilepsy (SHE) is an epilepsy syndrome that is characterized by the occurrence of sleep-related hypermotor seizures of variable complexity and duration. Seizures usually arise in the frontal lobe, but extrafrontal seizure onset zones are well described. To identify clinically relevant ictal features of SHE that could distinguish a frontal from an extrafrontal onset zone, we conducted a retrospective analysis of seizure characteristics in 58 patients with drug-resistant SHE (43 frontal and 15 extrafrontal) who underwent video-stereo-electroencephalographic recordings and became seizure-free after epilepsy surgery. We found that the mean duration of electrographic seizures and clinically observable ictal manifestations were significantly shorter in frontal SHE compared to extrafrontal SHE. The mean latency between electrographic seizure onset and the onset of hypermotor manifestations was also shorter in frontal SHE. Accordingly, a latency > 5 seconds between the first video-detectable movement (eg, eye opening or a minor motor event) and the onset of hypermotor manifestations yielded a sensitivity of 75% and a specificity of 90% for an extrafrontal onset, thereby indicating that specific ictal features in SHE can provide clinically useful clues to increase diagnostic accuracy in this syndrome., (Wiley Periodicals, Inc. © 2018 International League Against Epilepsy.)

Objective: We aimed to (1) assess the concordance between various polymicrogyria (PMG) types and the associated epileptogenic zone (EZ), as defined by stereoelectroencephalography (SEEG), and (2) determine the postsurgical seizure outcome in PMG-related drug-resistant epilepsy., Methods: We retrospectively analyzed 58 cases: 49 had SEEG and 39 corticectomy or hemispherotomy., Results: Mean age at SEEG or surgery was 28.3 years (range, 2-50). PMG was bilateral in 9 (16%) patients and unilateral in 49, including 17 (29%) unilobar, 12 (21%) multilobar, 15 (26%) perisylvian, and only 5 (9%) hemispheric. Twenty-eight (48%) patients additionally had schizencephaly, heterotopia, or focal cortical dysplasia. The SEEG-determined EZ was fully concordant with the PMG in only 8 (16%) cases, partially concordant in 74%, and discordant in 10%. The EZ included remote cortical areas in 21 (43%) cases and was primarily localized in those in 5 (10%), all related to the mesial temporal structures. All but 1 PMG patient with corticectomy or hemispherotomy had a unilateral PMG. At last follow-up (mean, 4.6 years; range, 1-16), 28 (72%) patients remained seizure free. Shorter epilepsy duration to surgery was an independent predictor of seizure freedom., Interpretation: PMG-related drug-resistant epilepsy warrants a comprehensive presurgical evaluation, including SEEG investigations in most cases, given that the EZ may only partially overlap with the PMG or include solely remote cortical areas. Seizure freedom is feasible in a large proportion of patients. PMG extent should not deter from exploring the possibility of epilepsy surgery. Our data support the early consideration of epilepsy surgery in this patient group. Ann Neurol 2017;82:781-794., (© 2017 American Neurological Association.)

Background: Detailed neuropathological information on the structural brain lesions underlying seizures is valuable for understanding drug-resistant focal epilepsy., Methods: We report the diagnoses made on the basis of resected brain specimens from 9523 patients who underwent epilepsy surgery for drug-resistant seizures in 36 centers from 12 European countries over 25 years. Histopathological diagnoses were determined through examination of the specimens in local hospitals (41%) or at the German Neuropathology Reference Center for Epilepsy Surgery (59%)., Results: The onset of seizures occurred before 18 years of age in 75.9% of patients overall, and 72.5% of the patients underwent surgery as adults. The mean duration of epilepsy before surgical resection was 20.1 years among adults and 5.3 years among children. The temporal lobe was involved in 71.9% of operations. There were 36 histopathological diagnoses in seven major disease categories. The most common categories were hippocampal sclerosis, found in 36.4% of the patients (88.7% of cases were in adults), tumors (mainly ganglioglioma) in 23.6%, and malformations of cortical development in 19.8% (focal cortical dysplasia was the most common type, 52.7% of cases of which were in children). No histopathological diagnosis could be established for 7.7% of the patients., Conclusions: In patients with drug-resistant focal epilepsy requiring surgery, hippocampal sclerosis was the most common histopathological diagnosis among adults, and focal cortical dysplasia was the most common diagnosis among children. Tumors were the second most common lesion in both groups. (Funded by the European Union and others.).

Objective: The contribution of recurring seizures to the progression of epileptogenesis is debated. Seizure-induced brain damage is not conclusively demonstrated either in humans or in animal models of epilepsy. We evaluated the expression of brain injury biomarkers on postsurgical brain tissue obtained from 20 patients with frequent seizures and a long history of drug-resistant focal epilepsy., Methods: The expression patterns of specific glial, neuronal, and inflammatory molecules were evaluated by immunohistochemistry in the core of type II focal cortical dysplasias (FCD-II), at the FCD boundary (perilesion), and in the adjacent normal-appearing area included in the epileptogenic region. We also analyzed surgical specimens from cryptogenic patients not presenting structural alterations at imaging., Results: Astroglial and microglial activation, reduced neuronal density, perivascular CD3-positive T-lymphocyte clustering, and fibrinogen extravasation were demonstrated in the core of FCD-II lesions. No pathological immunoreactivity was observed outside the FCD-II or in cryptogenetic specimens, where the occurrence of interictal and ictal epileptiform activity was confirmed by either stereo-electroencephalography or intraoperative electrocorticography., Interpretation: Recurrent seizures do not induce the expression of brain damage markers in nonlesional epileptogenic cortex studied in postsurgical tissue from cryptogenic and FCD patients. This evidence argues against the hypothesis that epileptiform activity per se contributes to focal brain injury, at least in the neocortical epilepsies considered here. Ann Neurol 2017;82:331-341., (© 2017 American Neurological Association.)

Objective: Several studies have reported that inhibitory networks are altered in dysplastic tissue obtained from epilepsy surgery specimens. A consistent decrease in the number of inhibitory interneuronal subpopulation that expresses parvalbumin (PV) was reported in postsurgical tissue from patients with focal cortical dysplasia (FCD). We tested if the decrease in PV protein expression observed in epileptic tissue corresponds to a parallel impairment in the γ-aminobutyric acid (GABA)ergic compartment., Methods: We analyzed postsurgical tissue from 30 surgically treated patients who underwent surgery for intractable epilepsy including 26 patients with FCD (types I, II, and III) and 4 patients without any microscopic visible lesion (cryptogenic) as controls. Serial sections were processed using in situ hybridization with GAD-65 and GAD-67 probes and immunocytochemistry with antibody against PV. The density of inhibitory PV-immunoreactive interneurons in relation to GABAergic cells was estimated in controls and in all different pathologic groups by using a two- and three-dimensional (2D and 3D) cell-counting technique. Field fraction and line profile analyses were added to estimate immunostaining proportion and distribution of PV signal generated in gray matter., Results: A reduction of PV-positive cells and PV-immunoreactivity was observed exclusively in FCD type I/III specimens compared with cryptogenic tissue from control patients with a poor postsurgical outcome. In FCD type II, a profound rearrangement in the cortical distribution of PV immunoreactivity was observed, without a quantitative reduction of the number of neurons and terminals. In situ hybridization did not reveal significant variations of GAD expression in any FCD subtype., Significance: Our study suggests a preservation of inhibitory networks in FCD postsurgical tissue, demonstrated by a substantial normal count of GABAergic neurons. A selective PV expression impairment is demonstrated in FCD type I and III and an abnormal, but not reduced, distribution of PV cells and terminals is confirmed in type II FCD. Possible functional consequences are discussed., (Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.)

Purpose: Temporal lobe epilepsy (TLE) with bilateral ictal involvement (bitemporal epilepsy, BTLE) is an intriguing form of TLE whose characteristics need to be carefully identified as BTLE patients are not good surgical candidates. The purpose of this study was to define the anatomo-electro-clinical features differentiating BTLE from unilateral TLE (UTLE)., Methods: Forty-eight BTLE patients underwent long-term video-EEG monitoring (VEEG) and experienced seizures with bilateral temporal lobe involvement. Their main electro-clinical (demographics, interictal and ictal EEG, ictal signs) and neuro-imaging [brain magnetic resonance imaging (MRI)] data were compared with those of a group of 38 UTLE patients., Results: In comparison with the UTLE patients, the BTLE cohort was significantly older at the time of epilepsy onset (p = 0.023), more frequently experienced bilateral asynchronous interictal epileptiform discharges during wakefulness (p = 0.001) and sleep (p < 0.001), bilateral upper limb dystonia (p = 0.005), and auditory auras (p = 0.027), and less frequently showed a recognisable initial ictal EEG pattern of focal flattening or low-voltage fast activity (p < 0.001), post-ictal memory of seizures (p = 0.001), staring (p < 0.001), head deviation (p = 0.004), oro-alimentary automatisms (p = 0.006), and positive brain MRI (p < 0.001). MRI revealed neoplastic lesions (p = 0.007) or alterations other than hippocampal sclerosis (p = 0.028) only in the UTLE patients., Conclusion: The possibility of recognising BTLE patients during pre-surgical evaluation or being able to suspect bitemporal seizures before VEEG by identifying particular anatomo-electro-clinical patterns is diagnostically important for epileptologists and can help to prevent possible surgical failures., (Copyright © 2015 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.)

Surgical disconnection of the affected hemisphere is considered the treatment of choice for Rasmussen encephalitis (RE), however few data on long-term outcomes after disconnective surgery are available. We report on long-term seizure, cognitive and motor outcomes after disconnective surgery in 16 (8 M, 8 F) RE patients. Pre- and post-operative evaluations included long-term video-EEG monitoring, MRI, assessment of motor function, and cognitive evaluation. Hemispherotomy, by various techniques was used to obtain functional disconnection of the affected hemisphere. The patients, of median current age 23.5 years, range 12-33, were operated on between 1993 and 2009. Median age at disease onset was 5.8 years (range 3-11.4). Median time from seizure onset to surgery was 3.8 years, range 8 months to 21 years. Post-surgical follow-up was a median of 9.5 years, range 3-20. At surgery all patients were receiving two or more antiepileptic drugs (AEDs). All but three patients were seizure-free at latest follow-up. AEDs had been stopped in ten patients; in the remaining six AEDs were markedly reduced. Postural control improved in all patients. Gain in cognitive functioning was significantly (p=0.002) related to disease duration. The long-term outcomes, in terms of seizure control, motor improvement, and cognitive improvement provide important support for disconnective surgery as first choice treatment for RE., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Cerebral cavernous malformations (CCMs) are a diffuse cerebrovascular disease affecting approximately 0.5% of the population. A CCM is characterized by abnormally enlarged and leaky capillaries arranged in mulberry-like structures with no clear flow pattern. The lesion might predispose to seizures, focal neurological deficits or fatal intracerebral hemorrhage. However, a CCM can also remain neurologically silent. It might either occur sporadically or as an inherited disorder with incomplete penetrance and variable expressivity. Due to advances in imaging techniques, the incidence of CCM diagnoses are increasing, and the patient must be managed on a multidisciplinary basis: genetic counselling, treatment if needed, and follow-up. Advances have been made using radiological and pathological correlates of CCM lesions adding to the accumulated knowledge of this disease, although management of these patients is very variable among centers. This review is aimed at providing an update in genetic and molecular insights of this condition. Included are implications for genetic counselling, and possible approaches to prevention and treatment that derive from the understanding of pathogenetic mechanisms., (© 2012 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.)

Introduction: This study aims to review the magnetic resonance imaging (MRI) aspects of a large series of patients with focal cortical dysplasia type II (FCD II) and attempt to identify distinctive features in the two histopathological subtypes IIa and IIb., Methods: We retrospectively reviewed the MRI scans of 118 patients with histological proven FCD IIa (n = 37) or IIb (n = 81) who were surgically treated for intractable epilepsy., Results: MRI was abnormal in 93 patients (79 %) and unremarkable in 25 (21 %). A dysplastic lesion was identified in 90 cases (97 %) and classified as FCD II in 83 and FCD non-II in seven cases. In three cases, the MRI diagnosis was other than FCD. There was a significant association between the presence of cortical thickening (p = 0.002) and the "transmantle sign" (p < 0.001) and a correct MRI diagnosis of FCD II. MRI positivity was more frequent in the patients with FCD IIb than in those with FCD IIa (91 % vs. 51 %), and the detection rate of FCD II was also better in the patients with type IIb (88 % vs. 32 %). The transmantle sign was significantly more frequent in the IIb subgroup (p = 0.003)., Conclusions: The rates of abnormal MRI results and correct MRI diagnoses of FCD II were significantly higher in the IIb subgroup. Although other MRI stigmata may contribute to the diagnosis, the only significant correlation was between the transmantle sign and FCD IIb.

The clinical features of nocturnal frontal lobe epilepsy (NFLE) consist of a spectrum of paroxysmal motor manifestations ranging from minor motor events (MMEs) to paroxysmal arousals (PAs) and major seizures. During MMEs and PAs scalp EEG generally does not show definite ictal abnormalities. We describe the clinical and electrophysiological features of three patients affected by drug-resistant NFLE studied with intracerebral electrodes during a presurgical evaluation. The stereo-EEG (SEEG) investigation revealed that MMEs can be fragments of the major seizure and occur during a brief epileptic discharge or on the following arousal. PAs, in the same subject, do not show a definite stereotypy despite the morphological and topographic similarity of the epileptic discharges, thus indicating that other variables may influence the clinical features of PAs.

Purposes: To show the results of the investigation conducted with intracerebral electrodes in a patient with drug-resistant nocturnal frontal lobe epilepsy, characterized by sleep-related paroxysmal motor attacks of increasing complexity ranging from simple and brief stereotyped motor events to paroxysmal arousals and major attacks., Methods: The patient was studied with long-term video-stereo-electroencephalographic monitoring by means of stereotactically implanted intracerebral electrodes., Results: Video-stereo-electroencephalography demonstrated that minor events and paroxysmal arousals, as well as major attacks, were correlated with a discharge in the right supplementary motor area and central cingulate gyms. The increasing complexity of these sleep-related ictal motor behaviors reflected a different pattern of discharge, with a progressive spread to other frontal and extrafrontal areas in the fully developed attacks. Surgical resection of the right supplementary motor area and central cingulate gyrus was performed. In the 5 years since the operation, the patient has remained completely seizure free., Conclusion: This study clearly demonstrates the ictal origin of minor events in nocturnal frontal lobe epilepsy. The increasing complexity of the motor behaviors from minor to major attacks reflects different duration, amplitude, and spread of the epileptic discharge.

Herein we reviewed the histopathological findings in 327 consecutive surgical specimens from patients with pharmaco-resistant epilepsy (PRE). Three major pathological groups (78.3% of all cases) were identified: Ammon's horn sclerosis (85 cases as an isolated lesion plus 18 as one part of a dual pathology), tumors (94 cases), and malformations (77 cases). Tumors, often associated with cortical dysplasias (CDs), were all of low histological grade and included 61 dysembryoplastic neuroepithelial tumors (DNTs), 29 gangliogliomas, and 4 pleomorphic xanthoastrocytomas (PXAs). Among the malformations were observed 52 CDs, 13 cavernomas, 8 cortical tubers, and 4 cysts. The remaining findings consisted of 16 scars (mostly post-traumatic) and 4 Rasmussen's encephalitis. Fifty-one (15.6%) specimens contained non-specific changes, and histological samples from 215 patients with presurgical implantation of electrodes revealed iatrogenic changes. All these figures are in agreement with the most recent and comparable series, and confirm the high incidence of DNTs that appear clearly as the most common tumoral entity in PRE. Our data also support the hypothesis of a close histogenetic relationship between DNT, ganglioglioma, and PXA, with a putative common origin from pluripotential progenitor CD34 positive cells of the subpial granular layer. As for CDs, our study confirms the clinical relevance of two main subtypes: severe CD (or Taylor's type CD) with neuronal cytomegaly and balloon cells, and non-Taylor's type CDs with a better outcome. Eventually, this series demonstrates that most patients have significant histopathological lesions, among which, aspects that are relevant to the diagnostic surgical pathologist are highlighted [published with a complete image database on CD-Rom].

Magnetic resonance imaging allows the identification of heterotopic gray matter (HGM) in medically intractable partial epilepsies. The relationships between HGM and the epileptogenic zone remain, however, unclear. In a case of a temporo-parietal epilepsy studied by stereo-EEG, interictal and ictal electrical activity of a temporal HGM were recorded, showing: (1) an intralesional electrical activity, (2) the possible presence of asynchronous spikes, and (3) an early but never initial, or isolated, involvement during ictal discharges. This suggests that the presurgical and surgical management of HGM must be guided, as for other lesions, by the coherence existing between ictal clinical and electrical features, and anatomical data.

Since January 1990, 70 patients with medically intractable partial epilepsy underwent a stereo-EEG investigation in our center. We first described technical requirements, and gave an overview of the variety of the explored cerebral regions and implantation patterns realized, pointing out the low rate of morbidity (1.4%). The three-dimensional epileptogenic zone thus defined led to a tailored individualized surgical excision in 60 patients, while 9 are waiting for surgery and the remaining 1 has been excluded (1.4%). Conceptual and technical aspects of the stereo-EEG methodology were discussed in order to underline its peculiarities in the field of "depth recordings", and more generally among the broader group of "invasive" procedures.

In patients with severe drug-resistant partial epilepsy, undergoing Stereo-EEG investigations, spatial definition of the "epileptogenic area" is mainly based on spontaneous seizures recordings, but also on seizures induced by intracerebral electrical stimulation (ES). Only "trains" ES (TES, 50 pps) are currently used with this aim; "shocks" ES (SES, 1 pps) are principally applied to localize motor pathways. We have shown, during a prospective study concerning 10 temporal lobe epileptic patients, that SES could frequently induce seizures, especially when stimulation is applied in the anterior part of the Ammon's horn. Even if its efficacy seems lower than by TES, this kind of stimulation, in the majority of the cases, does reproduce isolated ictal subjective symptomatology, allowing the visualization of the progressive organisation of ictal electrical discharges, and avoids "unexpected" ("false positive"?) clinical responses.

Low Frequency (1 Hz) Electrical Stimulation (LFES) has been systematically utilized, during stereo-EEG investigations, in 24 consecutive young adult patients considered for surgical treatment of severe drug-resistant partial epilepsy. Ninety seizures (1-14/patient) identical to the spontaneous ones previously recorded were thus obtained in 19 patients (79%). LFES is less effective for induction of seizures than high frequency (50 Hz) stimulation (5.9% vs 22.9%), and it also provokes less "false positive" responses (1% vs 17%). The main "sensitive" structures to LFES are the hippocampus, the amygdala, and the hippocampal gyrus. However, seizures were also induced by stimulating the temporal lobe white matter, the temporal pole, and the temporal neocortex, as well as the orbito-frontal cortex (in the only patient with fronto-temporal epilepsy). The more frequently observed electrical pattern is a gradual increase of spikes and spikes and waves frequency, with or without occurrence of low voltage fast activity. The high percentage of early "subjective" manifestations similar to the spontaneous ones, the lack of major electrical artifact, and the good visualization of the spatial evolution of the induced-discharge, strongly suggest that LFES is of great help for defining the "epileptogenic area".