EEG source imaging in pediatric epilepsy surgery: a new perspective in presurgical workup

PURPOSE: Epilepsy is a relatively frequent disease in children, with considerable impact on cognitive and social life. Successful epilepsy surgery depends on unambiguous focus identification and requires a comprehensive presurgical workup, including several neuroimaging techniques [magnetic resonance imaging, positron emission tomography (PET), and single-photon emission computed tomography (SPECT)]. These may be difficult to apply in younger or developmentally delayed children or both, requiring sedation, and hence, a significant workforce. Modern electric source imaging (ESI) provides accurate epileptic source-localization information in most patients, with minimal patient discomfort or need for cooperation. The purpose of the present study was to determine the usefulness of ESI in pediatric EEG recordings performed with routine electrode arrays. METHODS: Preoperative EEGs recorded from 19 to 29 scalp electrodes were reviewed, and interictal epileptiform activity was analyzed by using a linear source-imaging procedure (depth-weighted minimum norm) in combination with statistical parametric mapping. RESULTS: In 27 (90%) of 30 patients, the ESI correctly localized the epileptogenic region. These numbers compare favorably with the results from other imaging techniques in the same patients (PET, 82%; ictal SPECT, 70%). In extratemporal epilepsy, ESI was correct in all cases, and in temporal lobe epilepsy, in 10 of 13 cases. In two temporal lobe patients showing less-accurate ESI results, 128-electrode data could be analyzed, and in both cases, the 128-electrode ESI was correct. CONCLUSIONS: ESI with standard clinical EEG recordings provides excellent localizing information in pediatric patients, in particular in extratemporal lobe epilepsy. The lower yield in temporal lobe epilepsy seems to be due to undersampling of basal temporal areas with routine scalp recordings.     

Status epilepticus on the intensive care unit

Status epilepticus occurs on the intensive care unit, either because the patient has been transferred with refractory status epilepticus or as an incidental finding. Management of refractory status epilepticus on the intensive care unit is necessary for adequate treatment of the physiological compromise that occurs in convulsive status epilepticus. In addition, anaesthesia is sometimes necessary for the treatment of status epilepticus, and provided that the potential benefit of anaesthesia offsets the associated morbidity, then such an approach is warranted. In certain instances of nonconvulsive status epilepticus, especially in the elderly, the risks of anaesthesia outweigh the benefits of such aggressive treatment, and thus some caution must be exercised. Status epilepticus is also under-recognised as a cause of persistent coma on the intensive care unit, though the gain from aggressive treatment in this situation is unknown. In most instances, status epilepticus in coma carries such a poor prognosis that aggressive treatment is probably justified. Myoclonic status epilepticus also occurs on the intensive care unit, usually following cardiorespiratory arrest; this does not necessarily represent an agonal event especially if the intial insult was hypoxia related. Received: 11 November 2002, Accepted: 9 December 2002 Correspondence to M. C. Walker     

Multimodality language mapping in patients with left-hemispheric language dominance on Wada test

Objective

We determined the utility of electrocorticography (ECoG) and stimulation for detecting language-related sites in patients with left-hemispheric language-dominance on Wada test.

Methods

We studied 13 epileptic patients who underwent language mapping using event-related gamma-oscillations on ECoG and stimulation via subdural electrodes. Sites showing significant gamma-augmentation during an auditory-naming task were defined as language-related ECoG sites. Sites at which stimulation resulted in auditory perceptual changes, failure to verbalize a correct answer, or sensorimotor symptoms involving the mouth were defined as language-related stimulation sites. We determined how frequently these methods revealed language-related sites in the superior-temporal, inferior-frontal, dorsolateral-premotor, and inferior-Rolandic regions.

Results

Language-related sites in the superior-temporal and inferior-frontal gyri were detected by ECoG more frequently than stimulation (p < 0.05), while those in the dorsolateral-premotor and inferior-Rolandic regions were detected by both methods equally. Stimulation of language-related ECoG sites, compared to the others, more frequently elicited language symptoms (p < 0.00001). One patient developed dysphasia requiring in-patient speech therapy following resection of the dorsolateral-premotor and inferior-Rolandic regions containing language-related ECoG sites not otherwise detected by stimulation.

Conclusions

Language-related gamma-oscillations may serve as an alternative biomarker of underlying language function in patients with left-hemispheric language-dominance.

Significance

Measurement of language-related gamma-oscillations is warranted in presurgical evaluation of epileptic patients.     

EEG features of absence seizures in idiopathic generalized epilepsy: Impact of syndrome, age, and state

Purpose:   Factors influencing the electroencephalography (EEG) features of absence seizures in newly presenting children with idiopathic generalized epilepsy (IGE) have not been rigorously studied. We examined how specific factors such as state, provocation, age, and epilepsy syndrome affect the EEG features of absence seizures.
Methods:   Children with untreated absence seizures were studied using video-EEG recording. The influence of state of arousal, provocation (hyperventilation, photic stimulation), age, and epilepsy syndrome on specific EEG features was analyzed.
Results:   Five hundred nine seizures were evaluated in 70 children with the following syndromes: childhood absence epilepsy (CAE) 37, CAE+ photoparoxysmal response (PPR) 10, juvenile absence epilepsy (JAE) 8, juvenile myoclonic epilepsy (JME) 6, and unclassified 9. Polyspikes occurred in all syndromes but were more common in JME. They were brought out by drowsiness and sleep in fragments of generalized spike and wave (GSW). Polyspikes were more likely to occur during photic stimulation, but were not influenced by age independently. GSW was more likely to be disorganized in JME than JAE, and in JAE than CAE. Increasing age and levels of arousal were more likely to result in organized GSW. Factors specific to each child independently influenced EEG features; the nature of these factors has not been identified.
Discussion:   The EEG features of absence seizures are influenced by a complex interaction of age, epilepsy syndrome, level of arousal, provoking factors, and other intrinsic factors. Epilepsy syndrome alone cannot predict specific features of GSW; however, JME is more frequently associated with polyspikes and disorganization of the paroxysm.     

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.     

EEG findings in minor head trauma as a clue for indication to CT scan

In order to investigate the role of EEG in minor head traumata in the pediatric age, EEG and CT scan findings were compared in a series of 103 consecutive cases of children hospitalized within 24 h after head trauma. The EEGs were classified as normal in 50 patients, borderline in 10 patients, and abnormal in 43 patients. CT scan showed contusion in 6 patients and extracerebral hematoma in 4. All cases of abnormal CT scans were reported for patients with frankly abnormal EEG findings. In contrast, no pathological findings were found in CT scans for patients with normal EEG. The data suggest that EEG findings can play a major role in the diagnostic workup of patients with minor head traumata. Specifically, in the case of asymptomatic patients with normal EEG findings, it is likely that the CT scan will also be normal.Presented at the 11th Meeting of the European Society for Paediatric Neurosurgery, Naples 1988     

Sulthiame as monotherapy in children with benign childhood epilepsy with centrotemporal spikes: a 6-month randomized, double-blind, placebo-controlled study. Sulthiame Study Group

PURPOSE: To evaluate the efficacy and tolerability of sulthiame (STM) as monotherapy in children with benign childhood epilepsy with centrotemporal spikes (BECTS). METHODS: Sixty-six BECTS patients entered a 6-month double-blind trial and were randomized to receive either STM (5 mg/kg/day) or a placebo. All patients had had two or more seizures during the 6 months preceding the trial and were aged 3-11 years. Seizures were recorded by parents in a diary. STM plasma levels and electroencephalograms (EEGs) were overseen by patient-blinded observers. The primary effectiveness variable was the rate of treatment failure events (TFEs) per group. TFEs consisted of a first seizure after a 7-day run-in period, intolerable adverse events (AEs), development of another epileptic syndrome, or termination of the trial by parents or patient. RESULTS: Twenty-five of the 31 STM-treated patients (81%) and 10 of the 35 placebo-treated patients (29%) completed the trial without any TFEs (p = 0.00002). Most TFEs were seizures (n = 4 for the STM patients, n = 21 for the placebo group). Parents requested termination for two placebo-treated patients. Four patients were terminated for administrative reasons. No patient was withdrawn for AEs. While all patients displayed at least one specific focus in either the awake or asleep EEG initially, 11 STM-treated patients had a normal awake EEG and 10 had a normal asleep one after 6 months. CONCLUSIONS: STM was remarkably effective in preventing seizures in patients with BECTS. Patients suffering from > or = 2 seizures during the past 6 months had a high risk of early recidivism. STM was well tolerated and should be considered for children with BECTS who are in need of treatment.     

The influence of sulthiame on EEG in children with benign childhood epilepsy with centrotemporal spikes (BECTS)

PURPOSE: To evaluate the effects of sulthiame (Ospolot; STM) monotherapy compared with placebo on the EEG in children with benign childhood epilepsy with centrotemporal spikes (BECTS). METHODS: Sixty-six patients (aged 3-11 years) entered a 6-month double-blind trial and were randomized to either STM (n = 31) or placebo (n = 35). Clinical data and general results have been reported elsewhere (1). One-hundred seventy-nine sleep EEGs were recorded at screening and after 4 weeks, 3 months, and 6 months. EEGs were analyzed by a blind reviewer using a standard protocol for each EEG. This standard protocol collected data on general changes, specific epileptiform, and nonspecific focal and generalized changes. A classification system was defined depending on rating of pathologic EEG changes. Because of the higher number of treatment-failure events (i.e., seizures) in the placebo group, there was an increasing imbalance between the two groups regarding the number of recorded sleep EEGs over time (STM, 104; placebo, 74). A Wilcoxon-Mann-Whitney U test was used to describe differences in the grade of pathology during individual follow-up between the two groups. RESULTS: The sleep-EEG was found to be normalized in 21 patients treated with STM (12/21 transient) and in five patients treated with placebo (4/5 transient). In the STM group, the EEG showed a marked improvement during intraindividual course when comparing the classification of follow-up EEGs at each time point with the screening EEG. Comparable improvements were not observed in the placebo group (exact two-tailed p value at 4 weeks, p < 0.0001; at 3 months, p = 0.0010; and at 6 months, p < 0.0001). CONCLUSIONS: STM had marked effects on the EEG in BECTS, which led to normalization in the majority of the patients. Most of those whose EEGs were not normalized showed improvement in the grade of EEG pathology. Normalization persisted in >50% of patients during the investigation. Spontaneous normalization in the placebo group reflects the wide spectrum of individual courses, which must be considered when analyzing drug effects on EEG in BECTS.     

Association Study of Theta EEG Asymmetry and Brain-derived Neurotrophic Factor Gene Variants in Childhood-onset Mood Disorder

Background Childhood-onset mood disorders (COMD) include various serious, disabling psychiatric conditions that are heterogeneous in presentation and etiology. Because intermediate phenotypes may help to identify genetic contributors to COMD, we tested for an association between variants in the brain-derived neurotrophic factor (BDNF) gene and theta EEG asymmetry, both of which have been independently implicated in affective disorders. Methods Theta EEG asymmetry measures were calculated for a total of 191 individuals with COMD and 93 controls, who were also genotyped at seven BDNF single-nucleotide polymorphism (SNPs), two intergenic flanking SNPs, and one SNP in the lin-7 homolog C (Caenorhabditis elegans) (LIN7C) gene. Results Adjusting for sex and ethnicity in linear models of asymmetry scores at ten brain regions, significant genotype and genotype-by-ethnicity interactions were observed for marker Val66Met in two parietal (P3/4 and P7/8) regions in the depressed group only. Conclusions Our results suggest that the functional Val66Met polymorphism affects theta EEG asymmetry in parietal brain regions specifically in individuals with COMD. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Electroencephalography in epilepsy surgery planning

Objective To describe localizing value of surface EEG recording in the presurgical evaluation of medically intractable pediatric epilepsy patients.Methods We review the relevant concepts required for understanding the role of surface EEG in the presurgical evaluation and in identifying the epileptogenic zone. The unique features of EEG and its limitations are discussed.Conclusion Despite recent technological advancements, surface EEG continues to play a crucial role in defining the epileptogenic zone, and thus in presurgical planning.     

Ictal high-frequency oscillations at 80-200 Hz coupled with delta phase in epileptic spasms

Previous studies of epileptic spasms reported that ictal events were associated with high-frequency oscillations (HFOs) or delta waves involving widespread regions. We determined whether ictal HFOs at 80-200 Hz were coupled with a phase of slow-wave, whether ictal slow-waves were diffusely or locally synchronous signals, and whether the mode of coupling between HFOs and slow-wave phases differed between ictal and interictal states. We studied 11 children who underwent extraoperative electrocorticography (ECoG) recording. The phases and amplitudes of slow-waves were measured at the peak of ictal and interictal HFOs in the seizure-onset sites. Ictal HFOs were locked tightly to the phase of slow-wave at ≤1 Hz. Ictal slow-waves propagated from the seizure-onset site to other regions. In contrast, interictal HFOs in the seizure-onset site were loosely locked to the phase of slow-wave at ≤1 Hz but tightly to that of ≥3-Hz. Ictal slow-waves coupled with HFOs can be explained as near-field and locally synchronized potentials generated by the neocortex rather than far-field potentials generated by subcortical structures. Ictal slow-waves in epileptic spasms may be generated by a mechanism different from what generates interictal HFOs-slow-wave complexes.     

Dynamic imaging of seizure activity in pediatric epilepsy patients

Objective

To investigate the feasibility of using noninvasive EEG source imaging approach to image continuous seizure activity in pediatric epilepsy patients.

Methods

Nine pediatric patients with medically intractable epilepsy were included in this study. Eight of the patients had extratemporal lobe epilepsy and one had temporal lobe epilepsy. All of the patients underwent resective surgery and seven of them underwent intracranial EEG (iEEG) monitoring. The ictal EEG was analyzed using a noninvasive dynamic seizure imaging (DSI) approach. The DSI approach separates scalp EEGs into independent components and extracts the spatio-temporal ictal features to achieve dynamic imaging of seizure sources. Surgical resection and intracranial recordings were used to validate the noninvasive imaging results.

Results

The DSI determined seizure onset zones (SOZs) in these patients were localized within or in close vicinity to the surgically resected region. In the seven patients with intracranial monitoring, the estimated seizure onset sources were concordant with the seizure onset zones of iEEG. The DSI also localized the multiple foci involved in the later seizure propagation, which were confirmed by the iEEG recordings.

Conclusions

Dynamic seizure imaging can noninvasively image the seizure activations in pediatric patients with both temporal and extratemporal lobe epilepsy.

Significance

EEG seizure imaging can potentially be used to noninvasively image the SOZs and aid the pre-surgical planning in pediatric epilepsy patients.     

300例癫痫及可疑癫痫患者AEEG分析

目的：对３００例癫痫及可疑癫痫患者的动态脑电图的应用价值进行了初步探讨。方法;使用北京明思公司ＳＷ－ＪＨ系列智能化脑电监护仪描记,并与常规脑电图比较。结果：３００例中ＥＥＧ异常５４例,ＡＥＥＧ异常１７８例ＡＥＥＧ痫样放电检出率明显高天ＥＥＧ。１４４例继发性癫痫患者中,ＥＥＧ异常８例,ＡＥＥＧ异常１０例,二者无显著性差异。