Extratemporal Lobe Research Articles

Epilepsy surgery: current status and ongoing challenges.

This article reviews the current status of surgical treatment of epilepsy and introduces the ongoing challenges. Seizure outcome of resective surgery for focal seizures associated with focal lesions is satisfactory. Particularly for mesial temporal lobe epilepsy, surgical treatment should be considered from the earlier stage of the disease. Meanwhile, surgical outcome in nonlesional extratemporal lobe epilepsy is still to be improved using various approaches. Disconnective surgeries reduce surgical complications of extensive resections while achieving equivalent or better seizure outcomes. Multiple subpial transection is still being modified expecting a better outcome by transection to the vertical cortices along the sulci- and multi-directional transection from a single entry point. Hippocampal transection is expected to preserve memory function while interrupting the abnormal epileptic synchronization. Proper selection or combination of subdural and depth electrodes and a wide-band analysis of electroencephalography may improve the accurate localization of epileptogenic region. Patients for whom curative resective surgery is not indicated because of generalized or bilateral multiple nature of their epilepsies, neuromodulation therapies are options of treatment which palliate their seizures.

Spatial Coherence Profiles of Ictal High-Frequency Oscillations Correspond to Those of Interictal Low-Frequency Oscillations in the ECoG of Epileptic Patients.

We have previously demonstrated that the coherence of high-frequency oscillations (HFOs; 80-300Hz) increased during extratemporal lobe seizures in a consistent and spatially focused electrode cluster. In this study, we have investigated the relationship between cohered HFO intracranial EEG (iEEG) activity with that of slower low-frequency oscillations (LFOs; <80Hz). We applied wavelet phase coherence analysis to the iEEGs of patients with intractable extratemporal lobe epilepsy (ETLE). It was observed that areas on the implanted patient subdural grids, which exhibited strong ictal HFO coherence were similar to tissue regions displaying strong interictal LFO coherence in the 5-12Hz frequency range, relative to all other electrodes. A positive surgical outcome was correlated with having the clinically marked seizure onset zone(s) in close proximity to HFO/LFO coherence highlighted regions of interest (ROIs). Recent studies have suggested that LFOs (in the 8-12Hz frequency range) play an important role in controlling cortical excitability, by exerting an inhibitory effect on cortical processing, and that the presence of strong theta activity (4-8Hz) in awake adults is suggestive of abnormal and/or pathological activity. We speculate that the overlapping spatial regions exhibiting increased coherence in both ictal HFOs and interictal LFOs identified local abnormalities that underlie epileptogenic networks. Whereas it is worthwhile to note that the small patient group ( n = 7) studied here, somewhat limits the clinical significance of our study, the results presented here suggest targeting HFO activity in the 80-300Hz frequency range and/or interictal LFO activity in the 5-12Hz frequency range, when defining seizure-related ROIs in the iEEGs of patients with ETLE.

Functional network alterations and their structural substrate in drug-resistant epilepsy.

The advent of MRI has revolutionized the evaluation and management of drug-resistant epilepsy by allowing the detection of the lesion associated with the region that gives rise to seizures. Recent evidence indicates marked chronic alterations in the functional organization of lesional tissue and large-scale cortico-subcortical networks. In this review, we focus on recent methodological developments in functional MRI (fMRI) analysis techniques and their application to the two most common drug-resistant focal epilepsies, i.e., temporal lobe epilepsy related to mesial temporal sclerosis and extra-temporal lobe epilepsy related to focal cortical dysplasia. We put particular emphasis on methodological developments in the analysis of task-free or “resting-state” fMRI to probe the integrity of intrinsic networks on a regional, inter-regional, and connectome-wide level. In temporal lobe epilepsy, these techniques have revealed disrupted connectivity of the ipsilateral mesiotemporal lobe, together with contralateral compensatory reorganization and striking reconfigurations of large-scale networks. In cortical dysplasia, initial observations indicate functional alterations in lesional, peri-lesional, and remote neocortical regions. While future research is needed to critically evaluate the reliability, sensitivity, and specificity, fMRI mapping promises to lend distinct biomarkers for diagnosis, presurgical planning, and outcome prediction.

Insights into pediatric herpes simplex encephalitis from a cohort of 21 children from the California Encephalitis Project, 1998-2011.

Twenty-one children with confirmed herpes simplex encephalitis were identified in the California Encephalitis Project.Noteworthy features included 6 (29%) patients with an initial negative herpes simplex virus cerebrospinal fluid polymerase chain reaction test and 13 (62%) patients with extratemporal lobe involvement identified by neuroimaging [corrected]. Eleven cases were <4 years of age, but all 4 fatal cases occurred in adolescents.

Altered functional connectivity in seizure onset zones revealed by fMRI intrinsic connectivity.

Objective:The purpose of this study was to investigate functional connectivity (FC) changes in epileptogenic networks in intractable partial epilepsy obtained from resting-state fMRI by using intrinsic connectivity contrast (ICC), a voxel-based network measure of degree that reflects the number of connections to each voxel.Methods:We measured differences between intrahemispheric- and interhemispheric-ICC (ICCintra−inter) that could reveal localized connectivity abnormalities in epileptogenic zones while more global network changes would be eliminated when subtracting these values. The ICCintra−inter map was compared with the seizure onset zone (SOZ) based on intracranial EEG (icEEG) recordings in 29 patients with at least 1 year of postsurgical follow-up. Two independent reviewers blindly interpreted the icEEG and fMRI data, and the concordance rates were compared for various clinical factors.Results:Concordance between the icEEG SOZ and ICCintra−inter map was observed in 72.4% (21/29) of the patients, which was higher in patients with good surgical outcome, especially in those patients with temporal lobe epilepsy (TLE) or lateral temporal seizure localization. Concordance was also better in the extratemporal lobe epilepsy than the TLE group. In 85.7% (18/21) of the cases, the ICCintra−inter values were negative in the SOZ, indicating decreased FC within the epileptic hemisphere relative to between hemispheres.Conclusions:Assessing alterations in FC using fMRI-ICC map can help localize the SOZ, which has potential as a noninvasive presurgical diagnostic tool to improve surgical outcome. In addition, the method reveals that, in focal epilepsy, both intrahemispheric- and interhemispheric-FC may be altered, in the presence of both regional as well as global network abnormalities.

Perioperative anesthetic implications of epilepsy surgery: a retrospective analysis.

Drug-resistant epilepsy (DRE) occurs in about 30% of individuals with epilepsy. For seizure control, a wide range of surgical procedures are performed, depending on the underlying pathology. To address the anesthetic and perioperative concerns in these patients, we analyzed the data of persons with DRE who underwent epilepsy surgery at our institute. A retrospective analysis of patients who underwent epilepsy surgery from 2005-2010 was performed. For data collection and analysis, patients were divided into three groups: Group I (temporal lobe epilepsy), Group II (extratemporal lobe epilepsy), and Group III (multilobar epilepsy and others). A total of 241 surgical procedures were performed on 235 persons with DRE. The procedures included temporal (149) and extratemporal (47) lobe resection, hemispherotomy (31), corpus callosotomy (5), vagus nerve stimulation (3), and implantation of invasive cerebral electrodes (6). General anesthesia was the more common anesthetic technique; awake craniotomy was performed in only five cases. Intraoperative neuromonitoring was used most frequently in Group II. Patients in Group III had the longest intraoperative course and the greatest blood loss. The overall incidence of postoperative mechanical ventilation was 17.84%, with 53.84% of patients in Group III alone. At one-year follow-up, a good outcome was seen in 78% of temporal lobe resection, 55% of extratemporal cortical resection, 82% of hemispherotomy, and 80% of corpus callosotomy procedures. Careful preoperative selection and meticulous perioperative management are the most significant factors for success of epilepsy surgery. Although temporal and extratemporal lobe surgeries have a fairly stable perioperative course, multilobar epilepsy requiring disconnective surgery poses a greater challenge.

Subclinical seizures during intracranial EEG recording: Are they clinically significant?

To evaluate the clinical significance, characteristics and prognostic value of subclinical seizures of temporal and extra-temporal origin. Our epilepsy database from 2003 to 2011 was reviewed to identify patients with subclinical seizures during intracranial EEG recording who underwent surgical resection. Two groups were formed: Group 1 where both the clinical and subclinical seizures had the same seizure onset region, and Group 2 where some or all of the clinical and subclinical seizures originated from different regions. A total of 27 patients were identified with 791 seizures, of which 310 were subclinical. In Group 1 (n=14), 64% had good surgical outcome, and 36% had poor surgical outcome. In Group 2 (n=12), 83% had poor outcome while 17% had good outcome. One patient had only subclinical seizures. Eleven patients had subclinical seizures that propagated to a region beyond their onset zone. Of those 11 patients, 6 patients had subclinical seizures propagate to a different anatomical region than their clinical seizures. These six patients had poor surgical outcome. Our study, like others, found that subclinical seizures are clinically significant and including their onset region in the volume of surgical resection correlates with good surgical outcome for both temporal and extra-temporal lobe epilepsy (Fisher's exact test p=0.017). Propagation of subclinical seizures to a different region than clinical seizures can affect surgical outcome (Fisher's exact test p=0.06). Subclinical seizures may represent a distinct epileptic network.

Magnetoencephalography helps delineate the extent of the epileptogenic zone for surgical planning in children with intractable epilepsy due to porencephalic cyst/encephalomalacia.

Porencephalic cyst/encephalomalacia (PC/E) is a brain lesion caused by ischemic insult or hemorrhage. The authors evaluated magnetoencephalography (MEG) spike sources (MEGSS) to localize the epileptogenic zone in children with intractable epilepsy secondary to PC/E. The authors retrospectively studied 13 children with intractable epilepsy secondary to PC/E (5 girls and 8 boys, age range 1.8-15 years), who underwent prolonged scalp video-electroencephalography (EEG), MRI, and MEG. Interictal MEGSS locations were compared with the ictal and interictal zones as determined from scalp video-EEG. Magnetic resonance imaging showed PC/E in extratemporal lobes in 3 patients, within the temporal lobe in 2 patients, and in both temporal and extratemporal lobes in 8 patients. Magnetoencephalographic spike sources were asymmetrically clustered at the margin of PC/E in all 13 patients. One cluster of MEGSS was observed in 11 patients, 2 clusters in 1 patient, and 3 clusters in 1 patient. Ictal EEG discharges were lateralized and concordant with MEGSS in 8 patients (62%). Interictal EEG discharges were lateralized and concordant with MEGSS hemisphere in 9 patients (69%). Seven patients underwent lesionectomy in addition to MEGSS clusterectomy with (2 patients) and without (5 patients) intracranial video-EEG. Temporal lobectomy was performed in 1 patient and hemispherectomy in another. Eight of 9 patients achieved seizure freedom following surgery. Magnetoencephalography delineated the extent of the epileptogenic zone adjacent to PC/E in patients with intractable epilepsy. Complete resection of the MEGSS cluster along with PC/E can provide favorable seizure outcomes.

The utility of 18F-fluorodeoxyglucose PET (FDG PET) in epilepsy surgery

To investigate the utility of 18F-fluorodeoxyglucose Positron Emission Tomography (FDG PET) in helping decision making for epilepsy surgery. All patients with medically refractory focal epilepsy and MRI that was normal or discordant with clinical and EEG data underwent FDG PET. FDG PET scans were reported by two investigators blinded to clinical data using visual assessment aided by the semiquantitative assessment. All clinical, MRI and FDG PET data were reviewed in the multidisciplinary patient management conferences for the localization and further decisions, which were recorded in the electronic database. For this study, we reviewed the charts of all these patients to decide the usefulness of PET in further decision making. FDG PET was considered to be useful if led directly to surgery, helped in planning intracranial EEG or helped in excluding patients from further evaluation. 194 consecutive adult patients (median age, 32.5 years) underwent FDG PET; 158 had normal MRI, 12 had subtle MRI abnormalities and 24 had discordant non-invasive data. Final localization was temporal lobe epilepsy (TLE, n=64), frontal lobe epilepsy (FLE, n=66), temporal-plus epilepsy (n=26) and other extratemporal lobe epilepsies (ETE, n=38). PET scans were normal in 72 (37%) patients, showed unifocal hypometabolism in 98 (50.5%) and bilateral hypometabolism in 24 (12%) patients. The TLE group had a higher proportion of abnormal PET scans (67%) than FLE (52%) and ETE (61%). PET data were useful in 103 (53%) patients, more in TLE (63%) than FLE (38%) or ETE (50%). It led directly to surgery in 12 (6%) cases, helped in planning intracranial EEG in 67 (35%) patients and excluded 24 (12%) patients from further evaluation. Focal hypometabolism on FDG PET increased the odds of being selected for surgery or intracranial EEG by five fold [odds ratio, 5.1 (2.8-9.4); p<0.0001]. FDG PET scan can help decision making in 53% of presurgical patients with normal or discordant MRI. PET findings need to be evaluated in conjunction with other data.

Does the region of epileptogenicity influence the pattern of change in cortical excitability?

ObjectiveTo investigate whether cortical excitability measures on transcranial magnetic stimulation (TMS) differed between groups of patients with different focal epilepsy syndromes. Methods85 Patients with focal epilepsy syndromes divided into temporal and extra-temporal lobe epilepsy were studied. The cohorts were further divided into drug naïve-new onset, refractory and seizure free groups. Motor threshold (MT) and paired pulse TMS at short (2, 5, 10, 15ms) and long (100–300ms) interstimulus intervals (ISIs) were measured. Results were compared to those of 20 controls. ResultsCortical excitability was higher at 2 & 5ms and 250, 300ms ISIs (p<0.01) in focal epilepsy syndromes compared to controls however significant inter-hemispheric differences in MT and the same ISIs were only seen in the drug naïve state early at onset and were much more prominent in temporal lobe epilepsy. ConclusionDisturbances in cortical excitability are more confined to the affected hemisphere in temporal lobe epilepsy but only early at onset in the drug naïve state. SignificanceGroup TMS studies show that cortical excitability measures are different in temporal lobe epilepsy and can be distinguished from other focal epilepsies early at onset in the drug naïve state. Further studies are needed to determine whether these results can be applied clinically as the utility of TMS in distinguishing between epilepsy syndromes at an individual level remains to be determined.

Evaluation of subcortical grey matter abnormalities in patients with MRI-negative cortical epilepsy determined through structural and tensor magnetic resonance imaging.

BackgroundAlthough many studies have found abnormalities in subcortical grey matter (GM) in patients with temporal lobe epilepsy or generalised epilepsies, few studies have examined subcortical GM in focal neocortical seizures. Using structural and tensor magnetic resonance imaging (MRI), we evaluated subcortical GM from patients with extratemporal lobe epilepsy without visible lesion on MRI. Our aims were to determine whether there are structural abnormalities in these patients and to correlate the extent of any observed structural changes with clinical characteristics of disease in these patients.MethodsTwenty-four people with epilepsy and 29 age-matched normal subjects were imaged with high-resolution structural and diffusion tensor MR scans. The patients were characterised clinically by normal brain MRI scans and seizures that originated in the neocortex and evolved to secondarily generalised convulsions. We first used whole brain voxel-based morphometry (VBM) to detect density changes in subcortical GM. Volumetric data, values of mean diffusivity (MD) and fractional anisotropy (FA) for seven subcortical GM structures (hippocampus, caudate nucleus, putamen, globus pallidus, nucleus accumbens, thalamus and amygdala) were obtained using a model-based segmentation and registration tool. Differences in the volumes and diffusion parameters between patients and controls and correlations with the early onset and progression of epilepsy were estimated.ResultsReduced volumes and altered diffusion parameters of subcortical GM were universally observed in patients in the subcortical regions studied. In the patient-control group comparison of VBM, the right putamen, bilateral nucleus accumbens and right caudate nucleus of epileptic patients exhibited a significantly decreased density Segregated volumetry and diffusion assessment of subcortical GM showed apparent atrophy of the left caudate nucleus, left amygdala and right putamen; reduced FA values for the bilateral nucleus accumbens; and elevated MD values for the left thalamus, right hippocampus and right globus pallidus A decreased volume of the nucleus accumbens consistently related to an early onset of disease. The duration of disease contributed to the shrinkage of the left thalamus.ConclusionsPatients with neocortical seizures and secondary generalisation had smaller volumes and microstructural anomalies in subcortical GM regions. Subcortical GM atrophy is relevant to the early onset and progression of epilepsy.

Object location performance: Detection of functional impairment in right temporal lobe epilepsy

A prominent role of the right temporal lobe in nonverbal memory and visuospatial memory is widely accepted. A variety of neuropsychological tests have been shown to be sensitive to functional deficits related to right temporal lobe epilepsies mainly after surgical interventions, whereas preoperative deficits were seldom used to demonstrate test sensitivities. Furthermore, compensation processes or additional cognitive deficits related to left temporal or extratemporal dysfunctions are often not adequately taken into account. We used a modified object location task to demarcate preoperative visuospatial memory deficits of right temporal origin against such processes in patients with clinically verified right temporal, left temporal, or extratemporal lobe epilepsies. Healthy subjects served as controls. By using 8 “unnameable” objects, the positional memory accuracy of patients with right temporal lobe epilepsy was significantly lower than the positional memory performance of patients with left temporal and extratemporal lobe epilepsies, while object location memory performance differentiated patients with right temporal and extratemporal lobe epilepsies from patients with left temporal lobe epilepsy. Our version of a classical object location task might be a useful tool to detect mnestic deficits specifically related to right temporal lobe dysfunction. Future studies should focus on the refinement of testing conditions in order to detect differences induced by more distinct structural or functional deficits.

Clinical predictors of 2-year outcome of resective epilepsy surgery in adults with refractory epilepsy: a cohort study

ObjectivesResective epilepsy surgery is currently a standard treatment for intractable epilepsy. Seizure freedom and discontinuation of antiepileptic drugs are the ultimate goals of epilepsy treatment. This study was carried out...

Automatic classification of epilepsy types using ontology-based and genetics-based machine learning.

In the presurgical analysis for drug-resistant focal epilepsies, the definition of the epileptogenic zone, which is the cortical area where ictal discharges originate, is usually carried out by using clinical, electrophysiological and neuroimaging data analysis. Clinical evaluation is based on the visual detection of symptoms during epileptic seizures. This work aims at developing a fully automatic classifier of epileptic types and their localization using ictal symptoms and machine learning methods. We present the results achieved by using two machine learning methods. The first is an ontology-based classification that can directly incorporate human knowledge, while the second is a genetics-based data mining algorithm that learns or extracts the domain knowledge from medical data in implicit form. The developed methods are tested on a clinical dataset of 129 patients. The performance of the methods is measured against the performance of seven clinicians, whose level of expertise is high/very high, in classifying two epilepsy types: temporal lobe epilepsy and extra-temporal lobe epilepsy. When comparing the performance of the algorithms with that of a single clinician, who is one of the seven clinicians, the algorithms show a slightly better performance than the clinician on three test sets generated randomly from 99 patients out of the 129 patients. The accuracy obtained for the two methods and the clinician is as follows: first test set 65.6% and 75% for the methods and 56.3% for the clinician, second test set 66.7% and 76.2% for the methods and 61.9% for the clinician, and third test set 77.8% for the methods and the clinician. When compared with the performance of the whole population of clinicians on the rest 30 patients out of the 129 patients, where the patients were selected by the clinicians themselves, the mean accuracy of the methods (60%) is slightly worse than the mean accuracy of the clinicians (61.6%). Results show that the methods perform at the level of experienced clinicians, when both the methods and the clinicians use the same information. Our results demonstrate that the developed methods form important ingredients for realizing a fully automatic classification of epilepsy types and can contribute to the definition of signs that are most important for the classification.

A reduction of sleep spindles heralds seizures in focal epilepsy

ObjectivesSleep has profound effects on epilepsy. It may alter the occurrence of interictal discharges (IEDs) and seizures. Vice versa, an active epilepsy changes sleep. Sleep spindles are typically associated with an increase of IEDs. We examined whether seizures change the number and power of spindles preceding nightly seizures. MethodsWe retrospectively examined the nightly EEG recordings of presurgical epilepsy patients from our EEG-video-monitoring unit. We evaluated the 200s before the EEG seizure onset for spindle density (spindles per minute) and spindle power and compared that to the interictal baseline sleep. ResultsThe spindle density and the spindle power decreased significantly before the first seizure. The reduction before secondarily generalized seizures (8.7±2.5; p=0.001) was more pronounced than before focal seizures (10.5±2.5; p=0.003) compared to baseline (12.2±2.7). This finding was more pronounced in extratemporal lobe epilepsies than in temporal lobe epilepsies. The reduction of spindle power was also significant and was more pronounced in XTLE. These results were consistent for all other seizures during sleep, the mean spindle density decreased significantly in all focal (10.2±1.9; p=0.001) and generalized preictal period (8.8±2.4; p=0.001) compared to the mean interictal period (12.1±2.1). These were also more significant in XTLE than TLE group. ConclusionsOur data demonstrate that the occurrence of seizures and propensity of seizure generalisation in focal epilepsy is modulated by specific characteristics of light sleep such as sleep spindles. SignificanceThis study supports the notion that changes in the epileptic network precede the seizure onset and have an influence on seizure generation and termination.

Increased population of oligodendroglia-like cells in pediatric intractable epilepsy

Pediatric focal epilepsies often involve more extratemporal regions than adult epilepsies. This study aims to investigate the population of oligodendroglia-like cells (OLCs) in the pediatric focal epilepsy patients requiring surgery. We hypothesize that OLCs are one of the factors that extend the pediatric epileptic network in intractable epilepsy. Thirty (18 female) patients (1.8–16.9 years old with a mean of 9.7 years), who underwent resective surgery for the intractable epilepsy from 2010 to 2012 were retrospectively studied. Seizure types consisted of epileptic spasms in nine patients, partial seizures in 17 patients and partial seizure with secondary generalization in four patients. Eight autopsy cases without neurological disease served as controls. The neuropathology examination utilized the H&E/LFB stain and immunohistochemical staining for NeuN, GFAP and Olig2 as a marker of OLCs. OLCs were counted in three sites: (a) gray matter, (b) junction of gray/white matter, and (c) white matter. We also examined the correlation between the density of OLC among the three sites and the clinical features. Fifteen (50%) patients underwent multiple lobe resections, consisting of both temporal and extratemporal lobe resections in 12 patients and extratemporal lobe resections in 3 patients. The other 15 (50%) patients underwent single lobe resection including 3 (10%) patients with temporal lobectomy sparing hippocampus. Pathological diagnosis of epilepsy patients was as follows: 14 (47%) patients=focal cortical dysplasia (type I, 4; II, 9; III, 1); 6 (20%)=oligodendrogliosis; 6 (20%)=astrocytic gliosis; 2 (7%)=hyaline protoplasmic astrocytopathy and 2 (7%)=tuberous sclerosis complex. The numbers of OLCs at all three sites in epilepsy group were significantly higher than those of control group (p<0.001). In the epilepsy group, there was a significant difference among the number of OLCs at gray matter, junction of gray and white matter, and white matter (p<0.001). The number of OLCs significantly increased from gray matter and junction of gray/white matter to white matter. In the control group, there was no difference among the number of OLCs at three sites. There was no significant difference in the numbers of OLCs between focal cortical dysplasia types I and II. The significantly increased OLCs, especially in the white matter may contribute to the extensive epileptic network in children with intractable focal epilepsy.

Statistical SPECT processing in MRI-negative epilepsy surgery

To evaluate the benefit of statistical SPECT processing over traditional subtraction methods, we compared ictal-interictal SPECT analyzed by statistical parametric mapping (SPM) (ISAS), statistical ictal SPECT coregistered to MRI (STATISCOM), and subtraction ictal-interictal SPECT coregistered with MRI (SISCOM) in patients with MRI-negative focal temporal lobe epilepsy (nTLE) and extratemporal lobe epilepsy (nETLE). We retrospectively identified 49 consecutive cases of drug-resistant focal epilepsy that had a negative preoperative MRI and underwent interictal and ictal SPECT prior to resective epilepsy surgery. Interictal and ictal SPECT scans were analyzed using SISCOM, ISAS, and STATISCOM to create hyperperfusion and hypoperfusion maps for each patient. Reviewers blinded to clinical data and the SPECT analysis method marked the site of probable seizure origin and indicated their confidence in the localization. In nTLE and nETLE, the hyperperfusions detected by STATISCOM (71% nTLE, 57% nETLE) and ISAS (67% nTLE, 53% nETLE) were more often colocalized with surgery resection site compared to SISCOM (38% nTLE, 36% nETLE). In nTLE, localization of the hyperperfusion to the region of surgery was associated with an excellent outcome for STATISCOM (p = 0.005) and ISAS (p = 0.027), but not in SISCOM (p = 0.071). This association was not present in nETLE for any method. In an unselected group of patients with normal MRI and focal epilepsy, SPM-based methods of SPECT processing showed better localization of SPECT hyperperfusion to surgical resection site and higher interobserver agreement compared to SISCOM. These results show the benefit of statistical SPECT processing methods and further highlight the challenge of nETLE.

Resecting without detecting the lesion in extratemporal lobe epilepsy?

Nonlesional extratemporal lobe epilepsy (ETLE) often persists following resection of the site of ictal onset, localized with definitive intracranial EEG recordings.(1,2) In lesional ETLE, however, lesionectomy with resection of a single electrophysiologically defined ictal onset (ictogenic) zone often stops seizures immediately and permanently.(1,2) In temporal lobe epilepsy (TLE), a single ictogenic site can be resected, either with an accompanying lesion or in the absence of an MRI-detected lesion, and is a highly efficacious epilepsy therapy.(2) Efforts to increase surgical efficacy in nonlesional ETLE have focused on localization by functional imaging to substitute for lesion localization by structural imaging.

Automatic seizure detection in long-term scalp EEG using an adaptive thresholding technique: A validation study for clinical routine

ObjectiveIn a previous study we proposed a robust method for automatic seizure detection in scalp EEG recordings. The goal of the current study was to validate an improved algorithm in a much larger group of patients in order to show its general applicability in clinical routine. MethodsFor the detection of seizures we developed an algorithm based on Short Time Fourier Transform, calculating the integrated power in the frequency band 2.5–12Hz for a multi-channel seizure detection montage referenced against the average of Fz-Cz-Pz. For identification of seizures an adaptive thresholding technique was applied. Complete data sets of each patient were used for analyses for a fixed set of parameters. Results159 patients (117 temporal-lobe epilepsies (TLE), 35 extra-temporal lobe epilepsies (ETLE), 7 other) were included with a total of 25,278h of EEG data, 794 seizures were analyzed. The sensitivity was 87.3% and number of false detections per hour (FpH) was 0.22/h. The sensitivity for TLE patients was 89.9% and FpH=0.19/h; for ETLE patients sensitivity was 77.4% and FpH=0.25/h. ConclusionsThe seizure detection algorithm provided high values for sensitivity and selectivity for unselected large EEG data sets without a priori assumptions of seizure patterns. SignificanceThe algorithm is a valuable tool for fast and effective screening of long-term scalp EEG recordings.

The Principles of Surgical Treatment in Pediatric Epilepsy: Intractability to Medication, Determination of Potential Surgical Candidates and Advanced Techniques That Were Used for in Pediatric Epilepsy

Summary Majority of the epileptic syndromes in children are consisted of epilepsies arising from extratemporal lobes often associated with developmental abnormalities. Almost all the epilepsies in this group are associated with refractory seizures that require early consideration of surgical cure. Differences in the semiological and EEG properties of the seizures in the younger age group as compared to adults’ influence the decision of the surgical tecnique preferred. Seizure monitorizations of candidates are performed in comprehensive epilepsy centers. Highresolution MRIs and functional imaging techniques (PET, SPECT, fMRI) are used with spesific purposes. The main goal of epilepsy surgery is to stop the seizures without additional neurological deficit. However, in some situations like in the control of catastrophic seizures in small children, extensive resections such as hemispherectomy may be needed; yet plasticity may reduce the deficits, which were resulted from surgery to the minimum. In some special circumstances, palliative surgeries (corpus callosotomy, multiple subpial transections) could be performed to protect the patients from negative effects of multiple antiepileptics and the refractory seizures. Therefore, surgical treatments have to be chosen specifically for each patient.