The impact of cerebral source area and synchrony on recording scalp electroencephalography ictal patterns

PURPOSE: To determine the cerebral electroencephalography (EEG) substrates of scalp EEG seizure patterns, such as source area and synchrony, and in so doing assess the limitations of scalp seizure recording in the localization of seizure onset zones in patients with temporal lobe epilepsy. METHODS: We recorded simultaneously 26 channels of scalp EEG with subtemporal supplementary electrodes and 46-98 channels of intracranial EEG in presurgical candidates with temporal lobe epilepsy. We correlated intracranial EEG source area and synchrony at seizure onset with the corresponding scalp EEG. Eighty-six simultaneous intracranial- and scalp-recorded seizures from 23 patients were evaluated. RESULTS: Thirty-four intracranial ictal discharges (40%) from 9 patients (39%) had sufficient cortical source area (namely > 10 cm(2)) and synchrony at seizure onset to produce a simultaneous or nearly simultaneous focal scalp EEG ictal pattern. Forty-one intracranial ictal discharges (48%) from 10 patients (43%) gradually achieved the necessary source area and synchrony over several seconds to generate a scalp EEG ictal pattern. These scalp rhythms were lateralized, but not localizable as to seizure origin. Eleven intracranial ictal discharges (13%) from 4 patients (17%) recruited the necessary source area, but lacked sufficient synchrony to result in a clearly localized or lateralized scalp ictal pattern. CONCLUSIONS: Sufficient source area and synchrony are mandatory cerebral EEG requirements for generating scalp-recordable ictal EEG patterns. The dynamic interaction of cortical source area and synchrony at the onset and during a seizure is a primary reason for heterogeneous scalp ictal EEG patterns.     

Spatial distribution of intracranially recorded spikes in medial and lateral temporal epilepsies

Purpose: Although seizures and interictal spikes are not always colocalized, there may be valuable localizing information in the spatial distribution of spikes. To test this hypothesis, we studied the spatial distribution of intracranially recorded interictal spikes in patients with medial temporal (MT) and lateral temporal (LT) neocortical seizure onset. Methods: A total of 21 patients (MT n = 12, LT n = 9) who completed intracranial monitoring were selected for this study. Two 4‐h intracranial electroencephalography (icEEG) epochs were analyzed, one during wake and one during sleep, both at least 6 h removed from seizures. Spikes detected automatically in medial temporal structures [hippocampal formation (H) and entorhinal cortex (EC)], and in five cortical areas (occipital, frontal, parietal, lateral temporal, and inferior temporal) were tabulated. Results: Interictal spikes occurred broadly over medial temporal structures and cortical areas in MT and LT patients. The patients differed with a greater number of spikes in medial temporal structures in the MT group (p < 0.05 for H and p < 0.001 for EC) and a greater number of spikes in parietal (p < 0.01) and frontal (p < 0.001) areas in the LT group. There were sleep‐related increases in spike rates in inferomedial temporal structures in both groups. The two groups could be separated with a classifier based on medial temporal and parietal and frontal spikes (p < 0.0001). Discussion: MT and LT patients have different spatial distributions of interictal spikes and can be distinguished by the relative spike rates in medial temporal and extratemporal areas during sleep and wake.     

Prediction of Surgical Outcome by Interictal Epileptiform Abnormalities During Intracranial EEG Monitoring in Patients with Extrahippocampal Seizures

PURPOSE: Ictal intracranial EEG recordings obtained during continuous preoperative monitoring are often used to localize the region of seizure onset for purposes of surgical resection in patients with extrahippocampal seizures. Whether interictal epileptiform abnormalities during long-term monitoring can predict surgical outcome in this group is not established. METHODS: Intracranial EEGs of patients who underwent extrahippocampal resective epilepsy surgery were reviewed for interictal epileptiform abnormalities before medication discontinuation or first seizure occurrence. Interictal abnormalities were categorized as within or beyond the confines of surgical resection. We correlated these findings with the region of seizure onset, the pathologic substrate, and surgical outcome (by using Engel criteria) at 1-year minimum follow-up. RESULTS: Of 13 patients with interictal epileptiform abnormalities, six patients had interictal epileptiform discharges extending beyond the confines of surgical resection. These patients all had poor surgical outcome even if the region of electrographic seizure onset was resected. Seven patients had focal interictal epileptiform discharges, the entire extent of which were resected. All had good outcomes. All patients with structural lesions had focal interictal epileptiform abnormalities and good surgical outcomes. The spatial extent of interictal epileptiform discharges varied among patients with nonstructural lesions. However, those whose regions of interictal epileptiform abnormality were included in surgical resection also had good surgical outcome. CONCLUSIONS: The presence of interictal epileptiform discharges extending beyond the area of resection correlates with poor surgical outcome in patients with extrahippocampal epilepsy. In contrast, patients with focal interictal epileptiform discharges included in surgical resection have good surgical outcomes.     

Structures involved at the time of temporal lobe spikes revealed by interindividual group analysis of EEG/fMRI data

Purpose: We measured metabolic changes associated with temporal lobe (TL) spikes using combined electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). We selected 18 patients with temporal lobe epilepsy (TLE) who underwent a 2‐h simultaneous EEG–fMRI and had unilateral or bilateral independent TL spikes for interindividual group analysis, in order to identify consistent blood oxygenation level dependent (BOLD) responses to TL spikes. Methods: EEG was postprocessed and spikes were visually identified. fMRI data were preprocessed with motion correction, spatial smoothing, and removal of low frequency drifts. Spike timings were used as events for fMRI statistical analysis. Four hemodynamic response functions were used to account for variability in the BOLD response. Results: Group analysis revealed common areas of BOLD activations and deactivations. The hemodynamic response function (HRF) peaking 3 s after the spike showed activation involving ipsilaterally the mesial temporal structures (presumably the hippocampus), putamen/globus pallidus, inferior insula, and superior temporal gyrus. The HRF peaking at 5 s showed activations involving ipsi‐ and contralaterally the superior temporal gyrus and inferior insula. Both HRFs showed bilateral posterior cingulate deactivations. Discussion: We disclosed involvement of a network of activated areas during unilateral TL spikes, including ipsilateral mesial temporal structures, basal ganglia, and bilateral neocortical temporal regions. Despite the low temporal resolution of fMRI we demonstrated that contralateral temporal involvement occurred later than ipsilateral activation. This contralateral change took place in the absence of visible EEG changes. The posterior cingulate deactivation may reflect the interconnections between this region and other limbic structures. It may also partially correspond to a suspension of the default mode network, as previously described for TL spikes.     

颞叶癫痫发作初期头皮和颅内脑电定位价值的比较研究

目的 比较研究颞叶癫痫发作初期头皮脑电(sEEG)和颅内脑电(iEEG)的特点,探讨有定位意义的EEG指标.方法 常规行长程视频EEG(Video-EEG,V-EEG)监测,以捕捉到3次以上发作为标准.对sEEG难以定位的患者采用颅内埋置硬膜下和(或)深部电极,记录iEEG.结果 本组20例资料显示,sEEG和iEEG的定位检出率分别为50%和100%.经iEEG记录分析,7例sEEG不能定侧者5例完成定侧,10例广泛性sEEG异常者均定位为区域性或局限性表现.结论 低幅快节律、棘波和尖波节律具有重要的的定位价值;80%的sEEG低幅快节律表现者,与iEEG监测中表现一致;80%的sEEG颞叶棘波表现者,在iEEG监测中存在尖波节律.iEEG能明显提高致痫灶的定侧和定位准确性.     

Areas of interictal spiking are associated with metabolic dysfunction in MRI-negative temporal lobe epilepsy

PURPOSE: The objective of our study was to determine noninvasively whether metabolic dysfunction is present in focal areas of interictal electrophysiologic abnormality and whether metabolic dysfunction correlates with frequency of spiking. METHODS: We used a prospective, power analysis-driven, age-matched design to study 20 subjects with nonlesional temporal lobe epilepsy by using magnetoencephalography (MEG) and proton magnetic resonance spectroscopy (1H-MRS). MEG was used to localize the source area of interictal spikes. 1H-MRS measured integrated peak areas for N-acetyl compounds (NAA) and choline-containing compounds (Cho) in both hippocampi, the MEG spike zone, and the region contralateral to the MEG spike zone in all subjects. 1H-MRS was performed in seven controls. RESULTS: Fifteen of 20 subjects had a lower NAA/Cho ratio in the MEG spike zone compared with the contralateral homologous region. NAA/Cho was significantly decreased in the MEG spike zone (p < 0.01). NAA/Cho ratios were not significantly different between the hippocampus ipsilateral and contralateral to the spike activity, or from control hippocampi. NAA/Cho ratios did not correlate with spike frequency. CONCLUSIONS: Metabolic dysfunction is present in focal areas of interictal spiking in nonlesional temporal lobe epilepsy. These findings confirm that functional abnormalities can be detected in vivo in radiographically normal-appearing cortex exhibiting abnormal excitability.     

Interictal spikes on intracranial recording: behavior, physiology, and implications

Purpose: The physiological, pathological, and clinical meaning of interictal spikes (IISs) remains controversial. We systematically analyzed the frequency, occurrence, and distribution of IISs recorded from multiple intracranial electrodes in 34 refractory epileptic patients with respect to seizures and antiepileptic drug (AED) changes. Methods: Continuous spike counts from all recorded contacts of all implanted electrodes, and also separately for the subset of contacts involved at seizure onset, were tabulated for every hour of every day of recording, and expressed as spikes per hour in six preselected, 24‐h intervals (defined to exclude seizures): (1) on medications; (2) prepreseizure; (3) preseizure; (4) postseizure; (5) off meds; and (6) resumed meds. Mean spike rates were analyzed for differences between designated 24‐h intervals. Results: Spike rate in all recorded contacts consistently and significantly decreased after AED withdrawal, despite variability in initial spike rate, diurnal occurrence, seizure character/number/localization of onset, and type(s) of AED continued or withdrawn (p < 0.0001). A significant increase in spike rate was noted in the 24  h after seizures of medial temporal origin, in the medial temporal lobe contacts; neocortical onset seizures did not show any increase. Conclusions: These observations confirm and extend previous reports, suggesting a general effect of AED withdrawal, and a more specific effect of medial temporal lobe seizures, on IIS rate. AED mechanisms and efficacy might be demonstrated by quantifying IIS with changes in AEDs. Furthermore, variability in IIS rate after seizures distinguishes localization of seizure onset in medial temporal versus neocortical locations.     

Intracranial EEG in temporal lobe epilepsy: location of seizure onset relates to degree of hippocampal pathology

PURPOSE: To determine whether the specific location of electrographic seizure onset in the temporal lobe is related to hippocampal pathology in temporal lobe epilepsy (TLE). METHODS: Consecutive presurgical patients with scalp EEG-video evidence of TLE and no or mild hippocampal atrophy (HA) on magnetic resonance imaging (MRI) were prospectively studied by using depth and subdural strip electrode recordings to identify the site of the initial ictal discharge (IID). Thirty-four patients had either no or mild HA (HA- group). Four additional patients with moderate or marked HA (HA+ group) who required depth and strip electrodes served as a comparison group. Hippocampal pathology was assessed by MRI volumetrics and histopathologic grade of sclerosis (HS). RESULTS: Thirty-eight patients were investigated. In the HA- group, 10 patients had lobar ictal EEG onsets in the hippocampus (HF), medial paleocortex (MPC), and lateral neocortex (LNC); eight cases had regional IIDs in both HF and MPC; 12 persons had IIDs completely outside the HF; three cases lacked depth electrodes, and only one case (3%) had an IID confined to the HF. By contrast, three (75%) of four HA+ cases had IIDs confined to the HF (p = 0.002). Similarly, in 12 patients with low-grade HS, IIDs confined to the HF area were seen significantly less often than in six cases with high-grade HS (p = 0.025). CONCLUSIONS: In this study of a large number of patients with no to mild and a smaller group with moderate to marked HA and HS, the location of seizure onset in the temporal lobe was related to the degree of hippocampal pathology. Absence of HA and low-grade HS was each associated with IIDs in both the hippocampus and medial (with or without lateral) temporal cortex, or only the MPC or LNC. Marked HA and high-grade HS both were associated with IIDs restricted to the HF.     

Speech During Partial Seizures: Intracranial EEG Correlates

Vocalization during a seizure may help predict the location of seizure onset or identify structures ultimately involved in the seizure. Spontaneous vocalization during seizures was studied retrospectively in 22 patients with refractory complex partial seizures evaluated with bilateral intracranial electrodes. Of 22 patients, 12 vocalized during seizures. Seizures were as likely to originate from language-dominant (6/12) as from language-nondominant mesial temporal cortex (6/12). Fluent speech frequently occurred as seizure activity was recorded from language-dominant temporal lobe neocortex (6/12 seizures). Of the patients with well-localized seizure onsets who did not speak (6/10), seizures arose from both language-dominant and -nondominant mesial temporal cortex. We conclude that the presence or absence of vocalizations during a seizure does not reliably indicate the anatomic regions in which the seizure begins or spreads.     

Acute Psychosis During Intracranial EEG Monitoring: Close Relationship Between Psychotic Symptoms and Discharges in Amygdala

PURPOSE: This report examined the underlying mechanism of psychosis associated with epilepsy. METHODS: An adult patient with epilepsy manifesting acute psychosis during long-term EEG monitoring is presented, together with a literature review on this subject. RESULTS: A 25-year-old woman with intractable temporal lobe epilepsy developed acute psychosis while she underwent long-term intracranial EEG monitoring. After a clustering of seizures, she manifested psychotic symptoms including hallucination, stupor, and repeated fear. The transition of psychotic symptoms corresponded to the changes in frequency and morphology of seizure discharges restricted to the left amygdala. Improvement of psychosis coincided with disappearance of seizure discharges. CONCLUSIONS: This case confirmed a close relationship between psychotic symptoms and seizure discharges in the left amygdala. It is suggested that paroxysmal bombardment of the medial temporal lobe structure may be a pathogenetic factor of acute psychosis associated with epilepsy.     

Temporal and extratemporal BOLD responses to temporal lobe interictal spikes

PURPOSE: Simultaneous EEG and functional MRI (fMRI) allows measuring metabolic changes related to interictal spikes. Our objective was to investigate blood oxygenation level-dependent (BOLD) responses to temporal lobe (TL) spikes by using EEG-fMRI recording. METHODS: We studied 35 patients who had a diagnosis of temporal lobe epilepsy (TLE) and active TL spiking on routine scalp EEG recording. Two-hour sessions of continuous EEG-fMRI were recorded, and spikes were identified after offline artifact removal and used as events in the fMRI analysis. Each type of spike was analyzed separately, as one EEG-fMRI study. We determined significant (p < 0.05) positive (activation) and negative (deactivation) BOLD responses for each study. RESULTS: Twenty-seven patients had spikes during scanning (19 unilateral and eight bilateral). From a total of 35 fMRI studies, 29 (83%) showed BOLD responses: 14 had both activations and deactivations; 12, activations only; and three, deactivations only. Six (17%) showed no responses. Nineteen studies had mainly neocortical TL activation: Sixteen (84%) of 19 concordant with spikes, 12 of 16 with concomitant activation of the contralateral TL, and 16 of 19 with additional extratemporal activation; few showed exclusively mesial TL activation. Seventeen studies showed deactivation, either extratemporal plus temporal (n = 8) or exclusively extratemporal (n = 9). CONCLUSIONS: BOLD responses to TL spikes occurred in 83% of studies, predominated in the spiking temporal lobe, and manifested as activation or deactivation. Responses often involved the contralateral homologous cortex at the time of unilateral spikes and were frequently observed in extratemporal regions, suggesting that TL epileptic spikes can affect neuronal activity at a distance through synaptic connections.     

Lateralization of interictal spikes after corpus callosotomy

Objective

Corpus callosotomy may limit secondary bilateral synchrony into the primary epileptogenic hemisphere. This study investigated whether pre-operative EEG can predict post-operative spike lateralization.

Methods

The subjects included 14 patients with medically intractable drop attacks who underwent total corpus callosotomy. Pre-operative patterns of inter-hemispheric propagation were quantified by peak-latency analysis with the template-based spike averaging technique.

Results

Postoperative lateralization of interictal spikes was observed in 5 of the 14 patients. Inter-hemispheric latency was significantly longer in these 5 patients (mean 14.0 ms, range from 0 to 78 ms, versus mean 5.2 ms, range from 0 to 29 ms, p < 0.01). The lateralization occurred in association with the presence of structural lesions (p < 0.05). The post-operative spikes were lateralized to the lesion side in 3 of 4 patients with unilateral epileptogenic lesion. Three patients presented one-way inter-hemispheric propagation pattern pre-operatively. The post-operative spikes were lateralized to the hemisphere of the leading spikes in two.

Conclusions

Interictal spikes are lateralized to the epileptogenic hemisphere in some patients after callosotomy. Lateralization can be expected in the presence of structural lesions and/or longer inter-hemispheric latency.

Significance

Analysis of pre-operative EEG spikes may predict the primary epileptogenic hemisphere before corpus callosotomy.     

Mesial temporal spikes: a simultaneous comparison of sphenoidal, nasopharyngeal, and ear electrodes

A prospective study was performed to compare the relative ability of sphenoidal (SP), nasopharyngeal (NP), and ear electrodes for detecting mesial temporal lobe epileptiform discharges. Forty-four EEGs were performed on patients with complex partial seizures, simultaneously recording from NP, SP, and ear electrodes. Spikes were noted in SP derivations in 25 records, in ear derivations in 23 records, and in NP derivations in 20 records. A total of 875 spikes were counted, SP showing 99%, NP 57%, and ear 54% of discharges, with greatest amplitudes generally seen in SP derivations. The Mann-Whitney rank sum test showed SP electrodes superior to both NP and ear electrodes (p less than 0.0001) and no significant differences between NP and ear electrodes. We conclude that SP electrodes are superior to both NP and ear electrodes in detecting mesial temporal spikes.     

Tripolar concentric EEG electrodes reduce noise

ObjectiveTo assay EEG signal quality recorded with tripolar concentric ring electrodes (TCREs) compared to regular EEG electrodes.MethodsEEG segments were recorded simultaneously by TCREs and regular electrodes, low-pass filtered at 35 Hz (REG35) and 70 Hz (REG70). Clips were rated blindly by nine electroencephalographers for presence or absence of key EEG features, relative to the “gold-standard” of the clinical report.ResultsTCRE showed less EMG artifact (F = 15.4, p < 0.0001). Overall quality rankings were not significantly different. Focal slowing was better detected by TCRE and spikes were better detected by regular electrodes. Seizures (n = 85) were detected by TCRE in 64 cases (75.3%), by REG70 in 75 (88.2%) and REG35 in 69 (81.2%) electrodes. TCRE detected 9 (10.6%) seizures not detected by one of the other 2 methods. In contrast, 14 seizures (16.5%) were not detected by TCRE, but were by REG35 electrodes. Each electrode detected interictal spikes when the other did not.ConclusionsTCRE produced similar overall quality and confidence ratings versus regular electrodes, but less muscle artifact. TCRE recordings detected seizures in 7% of instances where regular electrodes did not.SignificanceThe combination of the two types increased detection of epileptiform events compared to either alone.     

Changes in current-source density of interictal spikes in benign epilepsy of childhood with centrotemporal spikes following treatment with oxcarbazepine

PurposeThe aim of this study was to detect clinical variables associated with the extent of change of the irritative zone in benign epilepsy of childhood with centrotemporal spikes (BECTS) after oxcarbazepine monotherapy.MethodBECTS patients receiving oxcarbazepine monotherapy were retrospectively reviewed. Changes in current-source density (CSD) of the maximum negative points of interictal spikes prior to the start of oxcarbazepine treatment were compared with CSD following oxcarbazepine treatment for 6–12 months. CSD was measured using low-resolution brain electromagnetic tomography (LORETA). Patients were divided into two groups based on the change in CSD: increased-extent or decreased-extent. Comparisons were made between the groups based on the age of onset, seizure frequency before treatment, time interval between seizure onset and treatment start, time interval between the two EEGs, oxcarbazepine dosage at the follow-up electroencephalography, occurrence of daytime seizures, and seizure control.ResultsFourteen patients were enrolled. Seven patients were in the decreased-extent group and six in the increased-extent group; one patient was excluded because she did not demonstrate any change in CSD. We found that seizure control differed significantly between the two groups: seizures were well-controlled in six out of seven patients in the decreased-extent group (85.7%), but in only one of six patients (16.7%) in the increased-extent group (p = 0.03). The other variables did not differ between the groups.ConclusionSeizure control may be associated with the extent of changes in the neuronal irritative zones of BECTS patients. We suggest that changes of CSD extent may be used as an imaging modality to evaluate clinical improvement in BECTS patients.     

Interictal and ictal EEG activity in the basal ganglia: an SEEG study in patients with temporal lobe epilepsy

PURPOSE: The interictal and ictal EEG activity in the basal ganglia in patients with temporal lobe epilepsy were studied during invasive EEG monitoring. METHODS: Eight epilepsy surgery candidates, each with a proven mesiotemporal seizure-onset zone, participated in the study. We used two invasive EEG methods to determine the seizure-onset zone. In both methods, diagonal electrodes were targeted into the amygdalohippocampal complex via a frontal approach and were passed through the basal ganglia with several leads. We analyzed 16 partial epileptic seizures, four of which became secondarily generalized. RESULTS: No epileptic interictal or ictal discharges were noticed in the basal ganglia. The interictal activity in the basal ganglia was a mixture of low-voltage beta activity and medium-voltage alpha-theta activity. When the ictal paroxysmal activity remained localized to the seizure-onset zone, the activity of the basal ganglia did not change. The spread of epileptic activity to other cortical structures was associated with the basal ganglia EEG slowing to a theta-delta range of 3-7 Hz. This slowing was dependent on the spread of ictal discharge within the ipsilateral temporal lobe (related to the investigated basal ganglia structures); alternatively, the slowing occurred in association with the regional spread of ictal activity from the mesiotemporal region to the temporal neocortex contralaterally to the investigated basal ganglia. Secondary generalization was associated with a further slowing of basal ganglia activity. CONCLUSIONS: The basal ganglia do not generate specific epileptic EEG activity. Despite the absence of spikes, the basal ganglia participate in changing or reflect changes in the distribution of the ictal epileptic activity.     

Non-linear analysis of intracranial human EEG in temporal lobe epilepsy.

OBJECTIVE: Intracranial EEG recordings from patients suffering from medically intractable temporal lobe epilepsy were analyzed with the aim of characterizing the dynamics of EEG epochs recorded before and during a seizure and comparing the classification of the EEG epochs on the basis of visual inspection to the results of the numerical analysis. METHODS: The stationarity of the selected EEGs was assessed qualitatively. The coarse-grained correlation dimension and coarse-grained correlation entropy were used for the non-linear characterization of the EEG epochs. RESULTS: High-pass filtering was necessary in order to make the majority of the epochs appear stationarity beyond a time scale of about 2 s. It was found that the dimension of the ictal EEGs decreased with respect to the epochs containing ongoing (interictal) activity. The entropy of the ictal recordings however increased. A scaling of the entropy was applied and it was found that the scaled entropy of the ictal EEG decreased, consistent with the increased regularity of the ictal EEG. The coarse-grained quantities discriminated well between EEG epochs recorded prior to and during seizures at locations displaying ictal activity and classification improved by including the linear autocorrelation time in the analysis. CONCLUSIONS: It is concluded that ictal and non-ictal EEG can be well distinguished on the basis of non-linear analysis. The results are in good agreement with the visual analysis.     

Multifactorial etiology of interictal behavior in frontal and temporal lobe epilepsy

Purpose: Based on discussions on the so called “epileptic personality” in patients with epilepsy, interictal behavioral impairments in frontal and temporal lobe epilepsies were examined in a multivariate approach that took demographic, clinical, and neuropsychological determinants into consideration. Methods: A total of 428 patients with epilepsies originating from the temporal (TLE; 84%) or frontal (FLE; 16%) lobes were examined in regard to personality (Fragebogen zur Persönlichkeit bei zerebralen Erkrankungen [FPZ], a clinical personality questionnaire) and mood (Beck Depression Inventory [BDI I]). Prevalence of impaired behavioral domains was determined. Etiologically relevant determinants of behavioral problems were identified via multiple regression analyses. Key Findings: Elevated depression scores (BDI) were evident in 42% of the patients, and not different in TLE and FLE. In regard to personality, introversion together with low mood, sociability, and self‐determination, as well as problems with interpersonal communication were frequent. The TLE group tended to show greater neuroticism and introversion, while FLE appeared more associated with behavioral aspects of an organic psychosyndrome. Multivariate analyses revealed demographic characteristics (age, gender, education), clinical aspects (psychiatric history, affected hemisphere, mesial pathology, seizure frequency, cognitive functions), and treatment (antiepileptic drug treatment) as relevant determinants, explaining up to 30% of the behavior. Significance: Behavioral abnormalities in patients with frontal or temporal lobe epilepsy are common but on the average mostly mild. Within a multivariate etiological model, localization (mesial yes/no) and lateralization (left > right) dependent behavioral problems in TLE and FLE seem to be overshadowed by other variables, of which patients’ and their families’ psychiatric history, patient characteristics and pharmacological treatment appear of major importance. Better education and cognitive capabilities may be discussed as protective features.     

Interictal EEG spikes identify the region of electrographic seizure onset in some,but not all,pediatric epilepsy patients

Purpose : The role of sharps and spikes, interictal epileptiform discharges (IEDs), in guiding epilepsy surgery in children remains controversial, particularly with intracranial electroencephalography (IEEG). Although ictal recording is the mainstay of localizing epileptic networks for surgical resection, current practice dictates removing regions generating frequent IEDs if they are near the ictal onset zone. Indeed, past studies suggest an inconsistent relationship between IED and seizure‐onset location, although these studies were based upon relatively short EEG epochs. Methods : We employ a previously validated, computerized spike detector to measure and localize IED activity over prolonged, representative segments of IEEG recorded from 19 children with intractable, mostly extratemporal lobe epilepsy. Approximately 8 h of IEEG, randomly selected 30‐min segments of continuous interictal IEEG per patient, were analyzed over all intracranial electrode contacts. Results : When spike frequency was averaged over the 16‐time segments, electrodes with the highest mean spike frequency were found to be within the seizure‐onset region in 11 of 19 patients. There was significant variability between individual 30‐min segments in these patients, indicating that large statistical samples of interictal activity were required for improved localization. Low‐voltage fast EEG at seizure onset was the only clinical factor predicting IED localization to the seizure‐onset region. Conclusions : Our data suggest that automated IED detection over multiple representative samples of IEEG may be of utility in planning epilepsy surgery for children with intractable epilepsy. Further research is required to better determine which patients may benefit from this technique a priori.