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Pathophysiological Findings explored via Epilepsy Surgery

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Abstract

This report describes the surgical indications for various epilepsy types and demonstrates the standard procedure and anatomy for mesial temporal lobectomy. In addition, we introduce the original technique of multiple subpial transection of hippocampus to preserve memory function. Real-time mapping by electrocorticogram is practically useful to obtain rough functional distributions on the electrodes. HGA indicates the most essential areas related to each task and clearly indicates the language related areas. Linguistic HGA mapping quickly identified the language area in the temporal lobe. Furthermore electric stimulation by linguistic HGA mapping to the identified temporal receptive language area evokes CCEP on the frontal lobe. The combination of linguistic HGA and frontal CCEP, which is called “Super Passive Mapping” does not need any patient cooperation and the sensitivity and specificity are 93.8% and 95%, respectively. In epilepsy surgery, there have been additional surgical options to control seizures, such as disconnection of abnormal networks, measuring cortico-cortico evoked potentials and vagal nerve stimulation. Finally, we refer to depth electrodes and laser ablation as novel diagnostic and treatment techniques.

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Background: We developed a functional brain analysis system that enabled us to perform real-time task-related electrocorticography (ECoG) and evaluated its potential in clinical practice. We hypothesized that high gamma activity (HGA) mapping would provide better spatial and temporal resolution with high signal-to-noise ratios. Methods: Seven awake craniotomy patients were evaluated. ECoG was recorded during language tasks using subdural grids, and HGA (60-170 Hz) maps were obtained in real time. The patients also underwent electrocortical stimulation (ECS) mapping to validate the suspected functional locations on HGA mapping. The results were compared and calculated to assess the sensitivity and specificity of HGA mapping. For reference, bed-side HGA-ECS mapping was performed in five epilepsy patients. Results: HGA mapping demonstrated functional brain areas in real time and was comparable with ECS mapping. Sensitivity and specificity for the language area were 90.1% ± 11.2% and 90.0% ± 4.2%, respectively. Most HGA-positive areas were consistent with ECS-positive regions in both groups and there were no statistical between-group differences. Conclusions: Although this study included a small number of subjects, it showed real-time HGA mapping with the same setting and tasks under different conditions. This study demonstrates the clinical feasibility of real-time HGA mapping. Real-time HGA mapping enabled simple and rapid detection of language functional areas in awake craniotomy. The mapping results were highly accurate, although the mapping environment was noisy. Further studies of HGA mapping may provide the potential to elaborate complex brain functions and networks.
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The Seventh International Workshop on Advances in Electrocorticography (ECoG) convened in Washington, DC, on November 13-14, 2014. Electrocorticography-basecl research continues to proliferate widely across basic science and clinical disciplines. The 2014 workshop highlighted advances in neurolinguistics, brain-computer interface, functional mapping, and seizure termination facilitated by advances in the recording and analysis of the ECoG signal. The following proceedings document summarizes the content of this successful multidisciplinary gathering. (c) 2015 Elsevier Inc.
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OBJECTIVE The authors undertook this study to validate the feasibility and safety of stereotactic radiofrequency thermocoagulation (SRT) for the surgical treatment of giant hypothalamic hamartoma (HH). METHODS Of the 109 patients who underwent SRT for hypothalamic hamartoma (HH) at the authors' institution between 1997 and 2013, 16 patients (9 female, 7 male) had giant HHs (maximum diameter ≥ 30 mm). The clinical records of these 16 patients were retrospectively reviewed. RESULTS The patients' age at first SRT ranged from 1 to 22 years (median 5 years). The maximum diameter of their HHs was 30–80 mm (mean 38.5 mm). Eleven HHs had bilateral attachments to the hypothalamus. All patients had gelastic seizures (GS), and 12 had types of seizures other than GS. Some of these patients also had mental retardation (n = 10, 62.5%), behavioral disorders (n = 8, 50.0%), and precocious puberty (n = 11, 68.8%). A total of 22 SRT procedures were performed; 5 patients underwent repeat SRT procedures. There was no mortality or permanent morbidity. After 17 of the 22 procedures, the patients experienced transient complications, including high fever (n = 7), hyperphagia (n = 3), hyponatremia (n = 6), disturbance of consciousness (n = 1), cyst enlargement (n = 1), and epidural hematoma (n = 1). Thirteen patients (81.3%) achieved freedom from GS after the final SRT procedure during a follow-up period ranging from 6 to 60 months (mean 23 months). Twelve patients had nongelastic seizures in addition to GS, and 7 (58.3%) of these 12 patients experienced freedom from their nongelastic seizures. CONCLUSIONS SRT provided minimal invasiveness and excellent seizure outcomes even in patients with giant HHs. Repeat SRT is safe for residual GS. SRT is a feasible single surgical strategy for HH regardless of the tumor's size or shape.
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Minimally invasive surgical techniques for the treatment of medically intractable epilepsy, which have been developed by neurosurgeons and epileptologists almost simultaneously with standard open epilepsy surgery, provide benefits in the traditional realms of safety and efficacy and the more recently appreciated realms of patient acceptance and costs. In this review, the authors discuss the shortcomings of the gold standard of open epilepsy surgery and summarize the techniques developed to provide minimally invasive alternatives. These minimally invasive techniques include stereotactic radiosurgery using the Gamma Knife, stereotactic radiofrequency thermocoagulation, laser-induced thermal therapy, and MRI-guided focused ultrasound ablation.
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This book brings to date the reports and conclusions from the Montreal Neurological Institute's clinical, physiological, and neuro-surgical studies of epilepsy, and is, in a sense, a sequal to "Epilepsy and cerebral localization," published in 1941. There is extensive addition of new material on subcortical mechanisms, functional cortical localization, surgical and medical treatment and electroencephalography. The book is illustrated with 8 color plates and 314 black and white illustrations. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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Functional magnetic resonance imaging (fMRI) is a less invasive way of mapping brain functions. The reliability of fMRI for localizing language-related function is yet to be determined. We performed a detailed analysis of language fMRI reliability by comparing the results of 3-T fMRI with maps determined by extraoperative electrocortical stimulation (ECS). This study was performed on 8 epileptic patients who underwent subdural electrode placement. The tasks performed during fMRI included verb generation, abstract/concrete categorization, and picture naming. We focused on the frontal lobe, which was effectively activated by these tasks. In extraoperative ECS, 4 tasks were combined to determine the eloquent areas: spontaneous speech, picture naming, reading, and comprehension. We calculated the sensitivity and specificity with different Z score thresholds for each task and appropriate matching criteria. For further analysis, we divided the frontal lobe into 5 areas and investigated intergyrus variations in sensitivity and specificity. The abstract/concrete categorization task was the most sensitive and specific task in fMRI, whereas the picture naming task detected eloquent areas most efficiently in ECS. The combination of the abstract/concrete categorization task and a 3-mm matching criterion gave the best tradeoff (sensitivity, 83%; specificity, 61%) when the Z score was 2.24. As for intergyrus variation, the posterior inferior frontal gyrus showed the best tradeoff (sensitivity, 91%; specificity, 59%), whereas the anterior middle frontal gyrus had low specificity. Despite different tasks for fMRI and extraoperative ECS, the relatively low specificity might be caused by a fundamental discrepancy between the 2 techniques. Reliability of language fMRI activation might differ, depending on the brain region.
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False lateralization of ictal onset by scalp EEG has been reported in patients with severe hippocampal sclerosis associated with hemispheric lesions or atrophy. There has been no report of cases of false lateralization by scalp EEG in patients without detectable structural abnormalities on MRI, or in patients with neocortical temporal lobe epilepsy. We report a case of false lateralization of ictal onset by scalp EEG in a patient with neocortical temporal lobe epilepsy and a normal MRI examination, investigated by intracranial EEG recordings. The ictal activity failed to propagate in the ipsilateral temporal lobe, but was strongly propagated to the contralateral temporal lobe resulting in a false lateralization of seizure onset by scalp EEG. It is possible that the poor homolateral propagation and evolution of ictal activity in this patient may be due to a functional rather than structural abnormality of the ipsilateral hippocampus, causing reduced synchrony and amplitude in the ipsilateral temporal cortex.
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To evaluate the ability of MEG to detect medial temporal spikes in patients with known medial temporal lobe epilepsy (MTLE) and to use magnetic source imaging (MSI) with equivalent current dipoles to examine localization and orientation of spikes and their relation to surgical outcome. We prospectively obtained MSI on a total of 25 patients previously diagnosed with intractable MTLE. MEG was recorded with a 275 channel whole-head system with simultaneous 21-channel scalp EEG during inpatient admission one day prior to surgical resection. The patients' surgical outcomes were classified based on one-year follow-up after surgery. Nineteen of the 22 patients (86.4%) had interictal spikes during the EEG and MEG recordings. Thirteen of 19 patients (68.4%) demonstrated unilateral temporal dipoles ipsilateral to the site of surgery. Among these patients, five (38.5%) patients had horizontal dipoles, one (7.7%) patient had vertical dipoles, and seven (53.8%) patients had both horizontal and vertical dipoles. Sixty percent of patients with non-localizing ictal scalp EEG had well-localized spikes on MSI ipsilateral to the side of surgery and 66.7% of patients with non-localizing MRI had well-localized spikes on MSI ipsilateral to the side of surgery. Concordance between MSI localization and the side of lobectomy was not associated with a likelihood of an excellent postsurgical outcome. MSI can detect medial temporal spikes. It may provide important localizing information in patients with MTLE, especially when MRI and/or ictal scalp EEG are not localizing. This study demonstrates that MSI has a good ability to detect interictal spikes from mesial temporal structures.
Article
To validate the safety and efficacy of magnetic resonance imaging (MRI)-guided stereotactic radiofrequency thermocoagulation (SRT) for epileptogenic hypothalamic hamartoma (HH), we evaluated surgical outcomes and revised the MRI classification. We retrospectively reviewed 25 consecutive patients with HH (age range, 2-36 years; mean age, 14.8 years) with gelastic seizures. Other seizure types were exhibited in 22 patients (88.0%), precocious puberty in 8 (32.0%), behavioral disorder in 10 (40.0%), and mental retardation in 14 (56.0%). We classified HH into 3 subtypes according to coronal MRI: intrahypothalamic, parahypothalamic, and mixed hypothalamic type. Maximum diameter ranged from 8 to 30 mm (mean, 15.3 mm). All patients underwent SRT (74 degrees C, 60 seconds) for HH. HH subtype and size were correlated with precocious puberty, mental retardation, and behavioral disorder. Thirty-one SRT procedures were performed, requiring 1 to 8 tracks (mean, 3.8 tracks) and involving 1 to 18 lesions (mean, 7.2 lesions). There were no adaptive limitations, regardless of size or subtype. Mixed-type HHs needed more tracks and more lesions. No permanent complications persisted after SRT, and gelastic seizures disappeared in all but 2 patients. Complete seizure freedom was achieved in 19 patients (76.0%). These patients had not only disappearance of all seizure types and behavioral disorder but also intellectual improvement. The present SRT procedure has favorable efficacy and invasiveness and has no adaptive limitations. SRT should therefore be considered before adulthood. The new HH classification is useful to understand clinical symptoms and to determine surgical strategies.
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Intracranial electroencephalography (ICEEG) with chronically implanted electrodes is a costly invasive diagnostic procedure that remains necessary for a large proportion of patients who undergo evaluation for epilepsy surgery. This study was designed to evaluate whether magnetic source imaging (MSI), a noninvasive test based on magnetoencephalography source localization, can supplement ICEEG by affecting electrode placement to improve sampling of the seizure onset zone(s). Of 298 consecutive epilepsy surgery candidates (between 2001 and 2006), 160 patients were prospectively enrolled by insufficient localization from seizure monitoring and magnetic resonance imaging results. Before presenting MSI results, decisions were made whether to proceed with ICEEG, and if so, where to place electrodes such that the hypothetical seizure-onset zone would be sampled. MSI results were then provided with allowance of changes to the original plan. MSI indicated additional electrode coverage in 18 of 77 (23%) ICEEG cases. In 39% (95% confidence interval, 16.4-61.4), seizure-onset ICEEG patterns involved the additional electrodes indicated by MSI. Sixty-two patients underwent surgical resection based on ICEEG recording of seizures. Highly localized MSI was significantly associated with seizure-free outcome (mean, 3.4 years; minimum, >1 year) for the entire surgical population (n = 62). MSI spike localization increases the chance that the seizure-onset zone is sampled when patients undergo ICEEG for presurgical epilepsy evaluations. The clinical impact of this effect, improving diagnostic yield of ICEEG, should be considered in surgery candidates who do not have satisfactory indication of epilepsy localization from seizure semiology, electroencephalogram, and magnetic resonance imaging.
Article
Magnetic source imaging (MSI) is used routinely in epilepsy presurgical evaluation and in mapping eloquent cortex for surgery. Despite increasing use, the diagnostic yield of MSI is uncertain, with reports varying from 5% to 35%. To add benefit, a diagnostic technique should influence decisions made from other tests, and that influence should yield better outcomes. We report preliminary results of an ongoing, long-term clinical study in epilepsy, where MSI changed surgical decisions. We determined whether MSI changed the surgical decision in a prospective, blinded, crossover-controlled, single-treatment, observational case series. Sixty-nine sequential patients diagnosed with partial epilepsy of suspected neocortical origin had video-EEG and imaging. All met criteria for intracranial EEG (ICEEG). At a surgical conference, a decision was made before and after presentation of MSI. Cases where MSI altered the decision were noted. MSI gave nonredundant information in 23 patients (33%). MSI added ICEEG electrodes in 9 (13%) and changed the surgical decision in another 14 (20%). Based on MSI, 16 patients (23%) were scheduled for different ICEEG coverage. Twenty-eight have gone to ICEEG, 29 to resection, and 14 to vagal nerve stimulation, including 17 where MSI changed the decision. Additional electrodes in 4 patients covered the correct: hemisphere in 3, lobe in 3, and sublobar ictal onset zone in 1. MSI avoided contralateral electrodes in 2, who both localized on ICEEG. MSI added information to ICEEG in 1. Magnetic source imaging (MSI) provided nonredundant information in 33% of patients. In those who have undergone surgery to date, MSI added useful information that changed treatment in 6 (9%), without increasing complications. MSI has benefited 21% who have gone to surgery.
Article
We studied 30 patients with partial epilepsy and a radiological or pathological diagnosis of localized neuronal migration disorders, with a view to surgical treatment. Eight patients had identifiable prenatal etiological factors. The frequency of complex partial, partial motor, and secondarily generalized seizures was approximately 70% each. Drop attacks were present in 27%: Their presence usually correlated with a lesion involving the central region. Partial motor or generalized convulsive status epilepticus occurred in 30%, and was most frequently associated with extensive structural abnormalities involving two or more lobes. A full-scale intelligence quotient of less than 80 was found in 44%. Magnetic resonance imaging (MRI) was superior to computed tomography for identification of the dysplastic cortical lesions. In one third, MRI showed only subcortical abnormalities. It did not allow distinction between true pachygyria, focal cortical dysplasia, or the forme fruste of tuberous sclerosis. The epileptogenic area was usually more extensive than the lesion; it was multilobar in more than 70% of patients. Of 26 surgically treated patients, a histological diagnosis of the type of neuronal migration disorder was possible in 22: 12 had focal cortical dysplasia and 10 the forme fruste of tuberous sclerosis. In the remaining 4, no definite histological diagnosis was made, since the maximally abnormal tissue could not be examined. In the latter, and in the 4 nonoperated patients, the diagnosis of neuronal migration disorder was based on imaging findings. The presence of the forme fruste of tuberous sclerosis correlated with delayed psychomotor development and more extensive epileptogenic areas.
Article
Visual inspection and qualitative impressions of clinical EEG abnormalities are being replaced by quantitative characterization of scalp voltage fields and dipole modeling of underlying cerebral sources. Three approaches have been used in the analysis of focal spikes of complex partial epilepsy. 1) Instantaneous, single dipole, inverse solutions for the voltage topography of the spike peak have revealed two distinct equivalent dipole configurations in the brain lobe beneath the negative extreme-radial and oblique (mixed radial and tangential). Only radial dipoles have been found for frontal and fronto-central spikes, while either type have been found for temporal and occipital spike foci. 2) Dipole stability can be assessed by an inspection of sequential instantaneous solutions encompassing the spike complex or by calculating the standard deviation of dipole location (x,y,z) and orientation (elevation, azimuth) parameters during this period. Two-thirds of spike dipoles of the radial type and essentially all of the oblique equivalent dipoles were found to be stable, whereas one-third of the radial dipoles were unstable in position or orientation. 3) Spatio-temporal analysis can identify multiple underlying sources and their potentials. Modeling separate radial and tangential dipoles over the course of the spike has revealed a composite character for spike fields with oblique dipoles and often has defined leads or lags in activity that suggested propagation between infero-mesial and lateral temporal cortex. Correlations with clinical and intracranial EEG data suggest that patients with mesial temporal sclerosis have spikes with oblique and stable equivalent dipoles; patients with discrete cortical lesions have spikes with radial and stable dipoles; patients with extensive or multi-focal cortical insults have spikes with radial and unstable dipoles.
Ten of 16 patients with complex partial epilepsy displayed an interictal spike-slow wave sequence with characteristic morphology and depth voltage topography. This 'typical slow wave' (TSW) lasted 300-600 msec, was usually largest and negative in the anterior hippocampus, and positive in the amygdala. Simultaneous recordings from ipsilateral cingulate, supplementary motor, orbitofrontal, and lateral temporal cortices, as well as from the contralateral medial temporal lobe (MTL), revealed only small, apparently volume-conducted, wave forms. Simultaneously recorded multiunit activity within the focal MTL was profoundly inhibited during the TSW. The TSW propagated to the scalp, producing a large widespread positivity. A large endogenous potential with similar latency range and task correlates as the scalp-P3 was recorded from the MTL to infrequent tones in a simple discrimination task. This 'depth-P3' had very similar polarity and relative amplitude across MTL sites, as was observed for the TSW at the same electrode contacts. However, at more superficial intracranial sites, the TSW was relatively smaller than the P3. Similarly, from MTL to surface, the P3 was found to decrement about half as much as the TSW decrements. This evidence suggests that the surface P3 is generated, but in part only, by the MTL.
Article
The precision between dipole Brain Electric Source Analysis (BESA) and brain distributed Variable Resolution Electromagnetic Tomography (VARETA) models for the localization of brain sources of interictal epileptiform discharges in patients with partial complex epilepsy was compared. The localization of brain sources calculated with dipole analysis and variable resolution electromagnetic tomography in 20 interictal recordings was analyzed. The origin of the dipoles was temporal in 18 cases, frontal in 1 and occipital in another. One dipole was enough in 7 cases, whereas two dipoles were necessary in 13 cases. The localization of paroxysmal activity was the same with BESA and VARETA in 17 patients. BESA and VARETA are useful methods for EEG sources analysis; BESA has more precision for the localization of punctate epileptogenic regions, and VARETA provides more information concerning the extension of the epileptic zone.
Article
The aim of this study was to evaluate the use of functional magnetic resonance imaging as an alternative to intraoperative electrocortical stimulation mapping for the localization of critical language areas in the temporoparietal region. We investigated several requirements that functional magnetic resonance imaging must fulfill for clinical implementation: high predictive power for the presence as well as the absence of critical language function in regions of the brain, user-independent statistical methodology, and high spatial accuracy. Thirteen patients with temporal lobe epilepsy performed four different functional magnetic resonance imaging language tasks (ie, verb generation, picture naming, verbal fluency, and sentence comprehension) before epilepsy surgery that included intraoperative electrocortical stimulation mapping. To assess the optimal statistical threshold for functional magnetic resonance imaging, images were analyzed with three different statistical thresholds. Functional magnetic resonance imaging information was read into a surgical guidance system for identification of cortical areas of interest. Intraoperative electrocortical stimulation mapping was recorded by video camera, and stimulation sites were digitized. Next, a computer algorithm indicated whether significant functional magnetic resonance imaging activation was present or absent within the immediate vicinity (<6.4mm) of intraoperative electrocortical stimulation mapping sites. In 2 patients, intraoperative electrocortical stimulation mapping failed during surgery. Intraoperative electrocortical stimulation mapping detected critical language areas in 8 of the remaining 11 patients. Correspondence between functional magnetic resonance imaging and intraoperative electrocortical stimulation mapping depended heavily on statistical threshold and varied between patients and tasks. In 7 of 8 patients, sensitivity of functional magnetic resonance imaging was 100% with a combination of 3 functional magnetic resonance imaging tasks (ie, functional magnetic resonance imaging correctly detected all critical language areas with high spatial accuracy). In 1 patient, sensitivity was 38%; in this patient, functional magnetic resonance imaging was included in a larger area found with intraoperative electrocortical stimulation mapping. Overall, specificity was 61%. Functional magnetic resonance imaging reliably predicted the absence of critical language areas within the region exposed during surgery, indicating that such areas can be safely resected without the need for intraoperative electrocortical stimulation mapping. The presence of functional magnetic resonance imaging activity at noncritical language sites limited the predictive value of functional magnetic resonance imaging for the presence of critical language areas to 51%. Although this precludes current replacement of intraoperative electrocortical stimulation mapping, functional magnetic resonance imaging can at present be used to speed up intraoperative electrocortical stimulation mapping procedures and to guide the extent of the craniotomy.
Article
To test the sensitivity of extracranial magnetoencephalography (MEG) for epileptic spikes in different cerebral sites. We simultaneously recorded MEG and electrocorticography (ECoG) by using subdural electrodes with 1-cm interelectrode distances for one patient with lateral frontal epilepsy and one patient with basal temporal epilepsy. We analyzed MEG spikes associated with ECoG spikes and compared the maximal amplitude and number of electrodes involved. We estimated and evaluated the locations and moments of the equivalent current dipoles (ECDs) of MEG spikes. In patient 1, MEG detected 100 (53%) of 188 ECoG lateral frontal spikes, including 31 (46%) of 67 spikes that activated three subdural electrodes. MEG spike amplitudes correlated with ECoG spike amplitudes and the number of electrodes activated (p < 0.01). ECDs were perpendicular to the superior frontal sulcus. In patient 2, MEG detected 31 (26%) of 121 ECoG basal temporal spikes, but none that activated only three subdural electrodes. ECDs were localized in the entorhinal and parahippocampal gyri, oriented perpendicular to those basal temporal cortical surfaces. The ECD strength was 136.6 +/- 71.5 nAm in the frontal region, but 274.5 +/- 150.6 nAm in the temporal region (p < 0.01). When lateral frontal ECoG spikes extend >3 cm2 across the fissure, MEG can detect >50%, correlating with spatial activation and voltage. In the basal temporal region, MEG requires higher-amplitude discharges over a more extensive area. MEG shows a significantly higher sensitivity to lateral convexity epileptic discharges than to discharges in isolated deep basal temporal regions.
Article
The Wada test has historically been the conventional procedure for determining language lateralization before neurosurgery. However, functional magnetic resonance imaging (fMRI) offers a less invasive alternative to the Wada procedure. Research indicates that the two techniques used together may provide comparable, and sometimes complementary, information that results in improved prediction of postsurgical language ability. We present a case in which use of fMRI in conjunction with Wada testing provided complementary information about language lateralization before neurosurgical resection of a mesial temporal subependymoma for seizure control in a patient with schizencephaly.
Article
A better understanding of the mechanisms involved in human higher cortical functions requires a detailed knowledge of neuronal connectivity between functional cortical regions. Currently no good method for tracking in vivo neuronal connectivity exists. We investigated the inter-areal connections in vivo in the human language system using a new method, which we termed 'cortico-cortical evoked potentials' (CCEPs). Eight patients with epilepsy (age 13-42 years) underwent invasive monitoring with subdural electrodes for epilepsy surgery. Six patients had language dominance on the side of grid implantation and two had bilateral language representation by the intracarotid amobarbital test. Conventional cortical electrical stimulation was performed to identify the anterior and posterior language areas. Single pulse electrical stimuli were delivered to the anterior language (eight patients), posterior language (four patients) or face motor (two patients) area, and CCEPs were obtained by averaging electrocorticograms (ECoGs) recorded from the perisylvian and extrasylvian basal temporal language areas time-locked to the stimulus. The subjects were not asked to perform any tasks during the study. Stimulation at the anterior language area elicited CCEPs in the lateral temporo-parietal area (seven of eight patients) in the middle and posterior part of the superior temporal gyrus, the adjacent part of the middle temporal gyrus and the supramarginal gyrus. CCEPs were recorded in 3-21 electrodes per patient. CCEPs occurred at or around the particular electrodes in the posterior language area which, when stimulated, produced speech arrest. Similar early and late CCEPs were obtained from the basal temporal area by stimulating the anterior language area (three of three patients). In contrast, stimulation of the adjacent face motor area did not elicit CCEPs in language areas but rather in the postcentral gyrus. Stimulation of the posterior language area produced CCEPs in the anterior language (three of four patients) as well as in the basal temporal area (one of two patients). These CCEPs were less well defined. These findings suggest that perisylvian and extrasylvian language areas participate in the language system as components of a network by means of feed-forward and feed-back projections. Different from the classical Wernicke-Geschwind model, the present study revealed a bidirectional connection between Broca's and Wernicke's areas probably through the arcuate fasciculus and/or the cortico-subcortico-cortical pathway. CCEPs were recorded from a larger area than the posterior language area identified by electrical stimulation. This suggests the existence of a rather broad neuronal network surrounding the previously recognized core region of this area.
Article
To be considered for resective (curative) surgery, most seizures have to been proved to arise exclusively from one area of the brain that is functionally silent. The drug-resistance must be certain, and the patient must be strongly motivated to undergo surgery. Temporal lobectomy for drug-resistant temporo-mesial epilepsy is now scientifically validated by a randomized controlled trial. Hemispherotomy, which consists in complete disconnection of one hemisphere, is a curative technique, which may be considered where there is a pre-existing hemiplegia associated with a structural abnormality of the contralateral hemisphere. Therefore, it is rarely performed in adult patients. Stereotactic radiosurgery is also a curative technique, which shares most of its indications with those of temporo-mesial resections. Callosotomy is a palliative technique, which consists in disconnecting the hemispheres, one from the other. It may be considered in individuals having frequent atonic seizures (drop attacks). Multiple subpial transection involves transection of transverse fibers, leaving longitudinal fibers intact. It may be performed if the epileptogenic focus is located in an eloquent brain area. The complication rate of resective surgery is low. Controlateral motor impairement is the main permanent complication related to cortical resection. It is a rare occurrence (1 to 2 percent of cases) due to peroperative lesions of the sylvian vasculature, or of the anterior choroidal artery, or even of the motor area. Postoperative hematomas, infections, or hydrocephalus may also occur in 2 to 6 percent of cases, depending on the authors. Some postoperative neuropsychological complications are reported in the literature, especially after surgery on the dominant side. Hydrocephalus and infection are the most frequent complications occurring after hemispherotomy (10 percent of cases). Dysconnexion syndrome is a rare complication, which can be seen after total callosotomy. It is unusual for the effects of disconnection after anterior callosotomy to represent significant handicap. Permanent postoperative worsening of a pre-existing neurological impairement, as well as hematomas, are seen in less than 10 percent of the cases after multiple subpial transection. In conclusion, surgery is an important therapeutic option, which has to be considered as soon as the epileptic disease appears to be drug-resistant, particularly in case of temporo-mesial epilepsy.
Article
Noninvasive brain imaging tests can potentially supplement or even replace the use of intracranial electroencephalogram (ICEEG), an invasive, costly procedure used in presurgical epilepsy evaluation. This study prospectively examined the agreement between magnetic source imaging (MSI) and ICEEG localization in epilepsy surgery candidates. Patients completing video monitoring with scalp EEG who had intractable partial epilepsy based on ictal electro-clinico-anatomical features were screened. Forty-nine enrolled patients (mean age, 27 years; range, 1-61 years) completed MSI and ICEEG studies. Decisions about ICEEG and surgery were made at a consensus conference where MSI could only influence ICEEG coverage by indicating supplemental coverage to that already planned by an original hypothesis. The positive predictive value of MSI for seizure localization was 82 to 90%, depending on whether computed against ICEEG alone or in combination with surgical outcome. The kappa score of agreement for MSI with ICEEG was 0.2744 (p < 0.01) MSI yields localizing information with a high positive predictive value in epilepsy surgery candidates who typically require ICEEG. This finding suggests that enough clinical validity exists for MSI to potentially replace ICEEG for seizure localization.
Article
Due to the reported variability of the language laterality index (LI) across fMRI studies, reliable distinction between patients with unilateral and mixed language dominance is currently not possible, preventing clinical implementation of fMRI as a replacement for the invasive Wada test. Variability of the LI may be related to differences in experimental and control tasks, and statistical methodology. The goal of this study was to improve detection power of fMRI for hemispheric language dominance by using a combined analysis of four different language tasks (CTA), that has previously shown more reliable and robust Lls in groups of normal volunteers than individual task analyses (see Ramsey et al). The CTA targets brain areas that are common to different language tasks, thereby focusing on areas that are critical for language processing. Further advantage of the CTA is that it is relatively independent of specific task and control conditions. 18 patients with typical (i.e., left-sided, n = 11) and atypical (i.e., right-sided or mixed, respectively, n = 3 and n = 4) language dominance according to the Wada test underwent fMRI (groups respectively denoted as WadaL, WadaR, and WadaM patients). Statistical methodology (including thresholding of activity maps) was fixed to assure a user-independent approach. CTA yielded better results than any of the individual task analyses: it was more robust (on average 2.5 times more brain activity was detected due to its higher statistical power) and more reliable (concordance for WadaL, WadaM and WadaR patients was respectively 10/11 (91%), 3/4 (75%), and 2/3 patients (67%)). Overall, a significant correlation was observed between frontal and temporoparietal LIs. Remarkably, brain activity for WadaM patients was significantly lower than for WadaL or WadaR patients, and a dissociation in lateralization was observed between frontal (right-sided) and temporoparietal (left-sided) activity in three of four patients. Of the individual task analyses, the verb generation task yielded best results for patients with unilateral language dominance (same concordance as CTA). However, in contrast to CTA results, the verb generation task was unable to identify WadaM patients (concordance in one of four patients). In conclusion, the CTA is a promising approach for clinical implementation of fMRI for the prediction of hemispheric language dominance.
Article
It is known that functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) are sensitive to the frontal and temporal language function, respectively. Therefore, we established combined use of fMRI and MEG to make reliable identification of the global language dominance in pathological brain conditions. We investigated 117 patients with brain lesions whose language dominance was successfully confirmed by the Wada test. All patients were asked to generate verbs related to acoustically presented nouns (verb generation) for fMRI and to read three-letter words for fMRI and MEG. fMRI typically showed prominent activations in the inferior and middle frontal gyri, whereas calculated dipoles on MEG typically clustered in the superior temporal region and the fusiform gyrus of the dominant hemisphere. A total of 87 patients were further analyzed using useful data from both the combined method and the Wada test. Remarkably, we observed a 100% match of the combined method results with the results of the Wada test, including two patients who showed expressive and receptive language areas dissociated into bilateral hemispheres. The results demonstrate that this non-invasive and repeatable method is not only highly reliable in determining language dominance, but can also locate the expressive and receptive language areas separately. The method may be a potent alternative to invasive procedures of the Wada test and useful in treating patients with brain lesions.
Combining ESI, ASL and PET for quantitative assessment of drug-resistant focal epilepsy
  • Sf Storti
  • Boscolo Galazzo
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  • A Pizzini
  • Fb Arcaro
  • C Formaggio
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Effect of epilepsy magnetic source imaging on intracranial electrode placement
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Knowlton RC, Razdan SN, Limdi N, Elgavish RA, Killen J, Blount J, Van Hoef L, Paige L, Fraught E, Kankirawatana P, Bartolucci A, Riley K Effect of epilepsy magnetic source imaging on intracranial electrode placement. Ann Neurol 65 716 723, 2009.
Ravindran AV CAN-MAT Depression Work Group Canadian Network for Mood and Anxiety Treatments CANMAT 2016 clinical guidelines for the management of adults with major depressive disorder section 4. Neurostimulation treatments
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Milev RV, Giacobbe P, Kennedy SH, Blumberger DM, Daskalakis ZJ, Downar J, Modirrousta M, Patry S, Vila Rodriguez F, Lam RW, MacQueen GM, Parikh SV, Ravindran AV CAN-MAT Depression Work Group Canadian Network for Mood and Anxiety Treatments CANMAT 2016 clinical guidelines for the management of adults with major depressive disorder section 4. Neurostimulation treatments. Can J Psychiatry 61 561 575, 2016.
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ASL and PET for quantitative assessment of drug resistant focal epilepsy
  • S F Storti
  • Boscolo Galazzo
  • Del Felice
  • A Pizzini
  • F B Arcaro
  • C Formaggio
  • E Mai
  • R Manganofli
  • P Combining
Storti SF, Boscolo Galazzo I, Del Felice A, Pizzini FB, Arcaro C, Formaggio E, Mai R, Manganofli P Combining ESI, ASL and PET for quantitative assessment of drug resistant focal epilepsy. Neuroimage 102 Pt 1 49 59, 2014.