Postoperative EEG and seizure outcome in temporal lobe epilepsy surgery.

OBJECTIVE: To assess the prognostic value of scalp electroencephalogram (EEG) after epilepsy surgery, we investigated whether postoperative EEG abnormalities (interictal epileptiform discharges, IED; interictal slow activity, ISA) were associated with seizure outcome and other patient characteristics after resective surgery in patients with temporal lobe epilepsy (TLE). METHODS: Sixty-two patients with medically refractory TLE who underwent surgery were studied. Patients were categorized according to etiology (mesiotemporal sclerosis vs. tumors/cortical dysplasias); extent of surgical resection (extensive vs. limited); and amount of preoperative IED on wake EEG (oligospikers, <1 IED/h, vs. spikers). Patients were also classified as seizure-free (SF) or having persistent seizures/auras (not-SF) during follow up visits 1 month and 1 year after surgery. Preoperative 60-min interictal EEGs were evaluated for IED and ISA, and compared to postoperative wake EEGs. RESULTS: Seizures/auras persisted in 16/62 (25.8%) patients at 1 month and in 8/62 (12.9%) at 1 year follow up. ISA was not significantly related to outcome. Of 42 patients with EEG negative for IED at 1 month, 4 were not-SF; at 1 year, one of 44 such patients was not-SF. IED was significantly associated with seizure/aura persistence in patients categorized as mesiotemporal sclerosis and with extensive surgery. Oligospikers and spikers on preoperative EEG showed no differences in the postoperative seizure outcome, excellent in both cases; moreover, the presence of postoperative IEDs indicated auras/seizures persistence apart from the preoperative EEG spike frequency. CONCLUSIONS: Our study showed that the presence of IED of postoperatve EEG strongly indicates seizure/aura persistence. Therefore, serial EEGs should be included in postoperative follow up schedules as a crucial tool in evaluating seizure outcome.     

Spike frequency is dependent on epilepsy duration and seizure frequency in temporal lobe epilepsy.

OBJECTIVES: We wanted to investigate factors that are associated with frequency of interictal epileptiform discharges by investigating 303 patients with temporal lobe epilepsy (TLE). METHODS: We included all patients who consecutively underwent the adult presurgical evaluation program at our center and who had intractable, medial TLE with complex partial seizures due to unilateral medial temporal lobe lesions. The interictal EEG samples were automatically recorded and stored on computer. The location and frequency of interictal epileptiform discharges were assessed by visual analysis of interictal EEG samples of 2-minute duration every hour. RESULTS: There were 303 patients (aged 16-63) who met the inclusion criteria. The median interictal epileptiform discharge frequency was 15 IED/h, the median seizure frequency was 4 seizures/month. According to univariate analyses, we found that age at monitoring, epilepsy duration, and higher seizure frequency were associated with higher interictal epileptiform discharge frequency. In the logistic regression analysis, we found that higher seizure frequency (p < 0.001) and longer epilepsy duration (p = 0.007) were independently associated with higher spike frequency, while the age at monitoring was not. CONCLUSIONS: Seizure frequency and epilepsy duration (years of patient's life with seizure activity) were independently associated with IED frequency, suggesting that IED are modulated by seizures.     

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.     

Spikes on the postoperative EEG are related to preoperative spike frequency and postoperative seizures

PURPOSE: To investigate the factors which influence the persistence of interictal epileptiform discharges (IED) after epilepsy surgery. METHODS: In this retrospective study we included patients with intractable medial temporal lobe epilepsy (MTLE) who underwent presurgical evaluation including high-resolution MRI and video-EEG monitoring with seizure registration prior to an anterior temporal lobe resection. The postsurgical outcome was assessed by our team 6 months and 2 years after the surgery. RESULTS: One hundred and forty-seven patients fulfilled the inclusion criteria. The mean age of the patients was 31.8 (range 16-59 years). In 22 patients (15%) interictal epileptiform discharges were present on the postoperative routine EEG. We found that both the preoperative spike frequency ( P < 0.001 ) and postoperative seizures ( P = 0.04 ) were independently associated with the presence of IED on the postoperative routine EEG. The preoperative spike frequency was not associated with the postoperative outcome. The extent of resection showed no influence on the presence of postoperative IED. CONCLUSION: We hypothesize that two factors independently influence the presence of postoperative spikes: chronic interictal disturbance (represented as preoperative spike frequency) and the acute (postoperative) seizures. Our study confirmed that persistent postoperative IED had a prognostic value regarding the outcome of the epilepsy surgery.     

Bilateral mesial temporal lobe epilepsy: comparison of scalp EEG and hippocampal MRI-T2 relaxometry

OBJECTIVE: Bilateral hippocampal abnormality is frequent in mesial temporal lobe sclerosis and might affect outcome in epilepsy surgery. The objective of this study was to compare the lateralization of interictal and ictal scalp EEG with MRI T2 relaxometry. MATERIAL AND METHODS: Forty-nine consecutive patients with intractable mesial temporal lobe epilepsy (MTLE) were studied with scalp EEG/video monitoring and MRI T2 relaxometry. RESULTS: Bilateral prolongation of hippocampal T2 time was significantly associated with following bitemporal scalp EEG changes: (i) in ictal EEG left and right temporal EEG seizure onsets in different seizures, or, after regionalized EEG onset, evolution of an independent ictal EEG over the contralateral temporal lobe (left and right temporal asynchronous frequencies or lateralization switch; P = 0.002); (ii) in interictal EEG both left and right temporal interictal slowing (P = 0.007). Bitemporal T2 changes were not, however, associated with bitemporal interictal epileptiform discharges (IED). Lateralization of bilateral asymmetric or unilateral abnormal T2 findings were associated with initial regionalization of the ictal EEG in all but one patient (P < 0.005), with lateralization of IED in all patients (P < 0.005), and with scalp EEG slowing in 28 (82,4%) of 34 patients (P = 0.007). CONCLUSION: Our data suggest that EEG seizure propagation is more closely related to hippocampal T2 abnormalities than IED. Interictal and ictal scalp EEG, including the recognition of ictal propagation patterns, and MRI T2 relaxometry can help to identify patients with bitemporal damage in MTLE. Further studies are needed to estimate the impact of bilateral EEG and MRI abnormal findings on the surgical outcome.     

伴有癫痫发作的结节性硬化症患者的脑电图特点

目的分析伴有癫痫发作的结节性硬化症(TSC)患者的脑电图特点。方法总结101例有痫性发作的TSC患者的临床资料,对其发作间期及发作期脑电图进行分析。结果癫痫的发病年龄从10d～28岁不等,3岁以内发病者68人(67%)。101例患者均行24h视频脑电图监测,3例脑电图正常,98例脑电图异常,其中3例存在高幅失律,23例为慢波背景活动,72例背景活动正常或接近正常,但其中11例患者脑电图可见较多慢活动。在有痉挛发作的13例患者中,3例脑电图背景为高幅失律,7例为慢波背景活动。发作间期显示痫样波在双侧均明显者35例,一侧痫样波明显者63例,主要集中在前头部。48例患者监测到发作,监测到的发作最常见为部分性发作(27例),26例可以明确起源,主要集中在额颞叶。结论大多数TSC患者脑电图异常,可见痫样波发放,54%TSC患者通过视频脑电图可以明确痫样波起源,主要在额颞叶,左右两侧无明显差异。     

Postoperative routine EEG correlates with long-term seizure outcome after epilepsy surgery.

We investigated the correlation of interictal epileptiform discharges (IED) in routine EEG 6 and 24 months after epilepsy surgery with regard to long-term seizure outcome. In 148 patients (74% temporal lobe epilepsy (TLE), 26% extratemporal epilepsy) EEG results (IED present or absent) were correlated with the postoperative outcome using the Engel classification 6 and 24 months after resection (PO6m and PO2y, respectively). Self-evaluation was conducted 3 and 5 years after resection (PO3y and PO5y, respectively). Ninety-one patients (62%) were seizure-free 5 years after resection; 88% of them showed no IED in PO6m. Twenty-eight patients (19%) displayed IED in routine EEG 6 months after resection; 61% of them had recurrent seizures at PO5y, whereas of 120 patients without IED only 33% had recurrent seizures at PO5y; p=0.01. Absence of IED in PO6m and PO2y correlated with good outcome: 71% without IED remained seizure-free, whereas only 25% with IED at PO6m and PO2y remained seizure-free; p=0.001. Seizure-free patients (Engel 1) and patients with less favourable outcome (Engel 3-4) at PO6m and PO2y rarely changed categories of outcome during the following years (p<0.001). Half of the patients with favourable seizure reduction (Engel 2) changed to seizure-free (Engel 1) or to a worse outcome category (Engel 3-4). Postoperative routine EEG is a good prognostic instrument for the prediction of long-term seizure outcome, especially for TLE. It predicts the running up and down of fits in patients with rare seizures (Engel 2).     

Seizure recurrence following epilepsy surgery: Is post-operative EEG helpful?

ObjectivesWe examined whether the relationship between interictal epileptiform discharges (IED) on post-operative EEG and seizure recurrence after epilepsy surgery was different in patients with neocortical and mesiotemporal resections.MethodsWe reviewed the records of 93 consecutive patients who underwent epilepsy surgery at our center and who had adequate post-operative follow-up and a post-operative EEG to determine the type of surgery, the recurrence of seizures and the presence of IED on post-operative EEG.ResultsChi-square test revealed that for the entire group, there was a significant relationship between the presence of IED and seizure recurrence. However, this relationship was significant in neocortical surgery but not in mesiotemporal surgery. Time distribution of seizure recurrence revealed that in more than half the cases, seizures recurred with the first 3 months. Time distribution was not influenced by the presence of IED.ConclusionsThis study revealed that IED on early post-operative EEG correlate with seizure recurrence in neocortical but not mesiotemporal surgeries and may be used to guide patient counseling in this group of patients.     

The seizure onset zone drives state-dependent epileptiform activity in susceptible brain regions

ObjectiveDue to variability in the patterns of propagation of interictal epileptiform discharges (IEDs), qualitative definition of the irritative zone has been challenging. Here, we introduce a quantitative approach toward exploration of the dynamics of IED propagation within the irritative zone.MethodsWe examined intracranial EEG (iEEG) in nine participants undergoing invasive monitoring for seizure localization. We used an automated IED detector and a community detection algorithm to identify populations of electrodes exhibiting IED activity that co-occur in time, and to group these electrodes into communities.ResultsWithin our algorithmically-identified communities, IED activity in the seizure onset zone (SOZ) tended to lead IED activity in other functionally coupled brain regions. The tendency of pathological activity to arise in the SOZ, and to spread to non-SOZ tissues, was greater in the asleep state.ConclusionsIED activity, and, by extension, the variability observed between the asleep and awake states, is propagated from a core seizure focus to nearby less pathological brain regions.SignificanceUsing an unsupervised, computational approach, we show that the spread of IED activity through the epilepsy network varies with physiologic state.     

The long-term course of temporal lobe epilepsy: From unilateral to bilateral interictal epileptiform discharges in repeated video-EEG monitorings

IntroductionBilateral interictal epileptiform discharges (IED) and ictal patterns are common in temporal lobe epilepsy (TLE) and have been associated with decreased chances of seizure freedom after epilepsy surgery. It is unclear whether secondary epileptogenesis, although demonstrated in experimental models, exists in humans and may account for progression of epilepsy.Material and methodsWe reviewed consecutive video-EEG recordings from 1992 to 2014 repeated at least two years apart (mean interval 6.14 years) in 100 people diagnosed with TLE.ResultsIctal EEG patterns and IED remained restricted to one hemisphere in 36 people (group 1), 46 exhibited bilateral abnormalities from the first recording (group 2), 18 progressed from unilateral to bilateral EEG pathology over time (group 3). No significant differences between the three groups were seen with respect to age at epilepsy onset, duration, or underlying pathology. Extra-temporal IED during the first EEG recording were associated with an increased risk of developing bilateral epileptiform changes over time (hazard ratio 3.67; 95% CI 1.4, 9.4).ConclusionOur findings provide some support of progression in TLE and raise the possibility of secondary epileptogenesis in humans. The development of an independent contra-lateral epileptogenic focus is known to be associated with a less favorable surgical outcome. We defined reliable EEG markers for an increased risk of progression to more widespread or independent bitemporal epileptogenicity at an early stage, thus allowing for individualized pre-surgical counselling.     

Consistent localization of interictal epileptiform activity on EEGs of patients with tuberous sclerosis complex

PURPOSE: We addressed consistent localization of focal interictal epileptiform activity on EEGs of patients with tuberous sclerosis complex (TSC) and epilepsy. METHODS: Twenty-one patients with TSC with a 10-year history of epilepsy and interictal epileptiform activity in three or more EEG recordings were included. None of the patients had undergone epilepsy surgery. Local maxima of interictal epileptiform activity were measured from 76 EEG traces and 33 EEG reports. Information about the patients' clinical course was extracted from their medical records. Magnetic resonance imaging (MRI) and neuropsychological examinations were performed. Statistical analysis was performed with the Mann-Whitney U test. RESULTS: In eight patients, interictal epileptiform activity was consistently detected in one or two regions (group 1), and in 13 patients, epileptiform activity was detected in three or more regions (group 2). The number of foci increased throughout the disease course in both groups. Age at seizure onset and IQ were significantly higher in group 1. Complex partial seizures occurred more often in the patients of group 1. In 19 of the 21 patients, the most consistent epileptiform activity was localized in the frontotemporal region. CONCLUSIONS: Ninety percent of patients with TSC showed at least one region of consistent interictal epileptiform activity. Patients with one or two regions of epileptiform activity were older at seizure onset, often experienced complex partial seizures, and had mild or no mental deficits. These patients may be candidates for epilepsy surgery.     

Can single pulse electrical stimulation provoke responses similar to spontaneous interictal epileptiform discharges?

ObjectiveTo estimate the proportion of patients where EEG responses to single pulse electrical stimulation (SPES) are similar to spontaneous interictal epileptiform discharges (IEDs) in the same patient, and whether such resemblance is related to seizure onset.MethodsWe have visually compared the morphology, topography and distribution of IEDs and of SPES responses in 36 patients with intracranial EEG recordings during presurgical evaluation.ResultsEach patient showed between 3 and 17 different IED patterns, located at seizure onset zone and elsewhere. Only 13 patients showed the highest incidence and amplitude of IEDs at the site of focal seizure onset. Twenty-eight patients showed early responses which were similar to at least one IED pattern. Thirty patients showed delayed responses which were always similar to at least one IED pattern and were always located at seizure onset or in its vicinity.ConclusionsEarly SPES responses often, and delayed responses always, were similar to at least one IED pattern in the same patient. The IEDs resembling delayed responses were those associated with seizure onset.SignificanceThe similarities between IEDs and SPES responses suggest that SPES can trigger the mechanisms responsible for generating IEDs, which may become a tool to study the pathophysiology of IEDs.     

Factors underlying scalp-EEG interictal epileptiform discharges in intractable frontal lobe epilepsy.

AIMS: Scalp-EEG interictal epileptiform discharges (IEDs) may be less predictive of the outcome of frontal lobe epilepsy surgery than of temporal lobe epilepsy surgery. We identified factors associated with the location of scalp-EEG IEDs in intractable frontal lobe epilepsy. METHODS: Ten factors were assessed in a retrospective review of 53 patients with either concordant (frontal lobe seizure focus) or discordant (generalized or outside frontal seizure focus) IED or both, who had excellent surgical outcomes. The Fisher exact test and the Wilcoxon rank sum test determined statistically significant associations. RESULTS: Thirty-six patients (68%) had concordant IED, 24 (45%) discordant IED, and 17 (32%) both. Younger age at onset was significantly associated with discordant IED (mean, 7.5 years versus 17 years for patients without discordant IED; P < 0.01), whereas duration of epilepsy was not. Seizure foci at the frontal convexity were associated with concordant IED. About 72% of patients with a convexity seizure focus had concordant IED, compared with only 33% of patients with mesial frontal foci having concordant IED (P = 0.06). CONCLUSIONS: Early seizure onset in intractable frontal lobe epilepsy is associated with IEDs discordant with seizure focus. Frontal convexity seizure foci are more likely than mesial frontal seizure foci to be associated with concordant discharges.     

视频脑电图监测对癫痫的诊断价值

目的探讨视频脑电图(Video-EEG)对癫痫的诊断价值.方法对252例发作性疾病患者进行连续12～24小时监测,其中包括清醒、睡眠及诱发试验,分析临床发作和异常放电的关系,异常放电出现的时相,癫痫分型与异常放电的关系,临床发作前脑电图的改变以及临床发作间期和发作期异常脑电图的不同表现.结果252例监测到临床发作142例,其中同时伴异常放电者为111例;252例检出异常放电187例,其中出现于睡眠期者146例;确诊的111例中103例确定了发作类型,其中25例修正了发作类型;确诊的111例监测到发作前脑电图的异常改变,表现为背景脑电波频率和波幅的改变,或者出现痫样放电;111例不同发作类型癫痫患者发作间期和发作期有不同的异常脑电图表现.结论视频脑电图可提高痫样放电的检出率,有助于癫痫的诊断及分型,有利于观察癫痫患者发作间期及发作期脑电图的表现.     

病灶性癫痫的手术治疗及影响其预后的因素分析

目的 探讨病灶性癫痫的手术方法，并分析影响手术预后的一些因素。方法 回顾性地分析自2001年4月～2003年4月之间在我研究所接受手术治疗的所有病灶性癫痫患者的临床资料。33例患者手术后随访时间皆在1年或1年以上。按照Engel疗效分级标准，将其分为效果满意组与不满意组，对术前临床特点、电生理情况、手术方法等因素进行分析比较。结果 手术后效果满意率为73％。下列因素与手术效果有相关性：癫痫患病时间、发作频率以及脑电图发作间期痫性放电是否局限在病灶的脑叶上。另一方面，比较发病时年龄、是否有既发全面强直阵挛性发作以及是否完全切除术中皮层脑电监测(ECoG)为阳性的皮层三个因素，两组间无显著差异。不满意组中，皮质发育不全的患者占多数。结论 对于病灶性癫痫，手术采用病灶与周围致痫灶同时切除的方法，可获得满意的效果。癫痫患病时间、发作频率以及脑电图发作间期痫性放电是否局限在病灶的脑叶上与手术的效果有一定的相关性。     

Latency to first spike in the EEG of epilepsy patients.

BACKGROUND: Routine EEGs in individuals with epilepsy have interictal spikes in 56% of cases. The availability of prolonged EEG has changed the use of EEG in the assessment of epilepsy. OBJECTIVE: To determine the time to first epileptiform activity on EEG in patients with epilepsy. This data will help optimize the duration of electrographic assessment for interictal activity in epileptic individuals. METHODS: 46 consecutive patients aged 10 years or older with epilepsy were evaluated. Individuals with seizures in the prior 24h or with acute symptomatic seizures were excluded. Continuous EEG (for 1-7 days) was analyzed to find the first definite epileptiform activity and the latency assessed. RESULTS: 37% of the patients had epileptiform activity in the first 20min of the continuous recording (duration of a routine EEG). 89% had epileptiform activity within 24h. The yield drops beyond 24h. 8% of the individuals had no epileptiform activity even after 72h. CONCLUSIONS: The study suggests the need to consider a change in EEG strategy to assess interictal epileptiform activity. The greatest probability of capturing an interictal abnormality within 20min was in individuals with generalized epilepsy. In individuals with suspected epilepsy in whom electrographic interictal spike confirmation is deemed necessary, after a first nonspecific or normal routine EEG, a 24h EEG should be the next step in the electrographic assessment. This study suggests that there may not be much benefit in monitoring for durations longer than 24h, unless capturing a seizure is the intent.     

Lateralization of interictal EEG findings.

Several reports indicate that interictal epileptiform discharges (IED) may be more likely to occur over the left cerebral hemisphere than over the right. The objective of our study was to determine the frequency and type of IED on routine and multihour EEGs in a tertiary epilepsy center to estimate the frequency of left-sided versus right-sided IED and to determine interictal spike distribution pattern differences between adult and pediatric epilepsy patients. The current study retrospectively reviewed 31,207 EEGs (25,793 routine EEGs and 5414 multihour EEGs) recorded on 24,003 patients during the period from 1993 to 2003. All EEGs were read according to a systematic EEG classification system. Every patient was considered only once by including the first abnormal EEG. Regional unilateral or bilateral IEDs were recorded in 1707 patients (7%). Regional unilateral or bilateral slow was recorded in 2297 patients (9.6%). Left-sided regional IED were seen in 828 patients and accounted for 58% of all unilateral IED. Left-sided slow was seen in 1389 patients and accounted for 65% of all unilateral slow. Lateralization of slow was due to intermittent slow, whereas continuous slow involved both hemispheres equally. There was no lateralization difference in benign focal epileptiform discharges of childhood. Lateralization shows a tendency toward greater left-sided lateralization of interictal findings with aging. Benign focal epileptiform discharges were only seen under the age of 20 years old. Regional IEDs were seen in approximately 7% of patients and slowing occurs in 10% of patients. Both abnormalities were seen more frequently in the left hemisphere. Age adjusted analysis of the data revealed that this left-sided predominance was mildly increased in adults as compared with pediatric patients.     

Usefulness of Unilateral Interictal Sharp Waves of Temporal Lobe Origin in Prolonged Video-EEG Monitoring Studies

The value of EEG interictal epileptiform activity in predicting location of the seizure focus remains controversial. In 64 patients, scalp video-EEG monitoring studies showed one or two ipsilateral interictal foci in the temporal lobe. The site of these interictal foci correlated with location of the seizure focus recorded during prolonged video-electrocorticography (ECoG) with use of subdural grids placed under the mesiobasal temporal region and over the lateral temporal convexity. Our findings suggest that unilateral anterotemporal interictal foci can accurately predict location of seizure onset. This is also true in patients with two ipsilateral temporal interictal foci, provided that the dominant focus is localized in anterotemporal regions. We believe that in such patients invasive recordings are not warranted, but we caution against sole use of interictal epileptiform criteria for localization of the seizure focus. Correlation with clinical information, ictal EEG, neuropsychometric, and neu-roimaging studies is required before performance of epilepsy surgery.     

114例特发性夜间额叶癫痫的临床及脑电图研究

目的 分析114例特发性夜间额叶癫痫(NFLE)患者的临床特征、脑电图和神经影像学表现、治疗效果及预后.方法 回顾性分析解放军总医院癫痫门诊自1999年6月至2007年1月收治的114例NFLE患者的临床资料.结果 NFLE以夜间成串的偏转性、姿势性强直及过度运动发作为最显著的临床特征;本组22.9%清醒发作间期常规脑电图及28%清醒发作间期动态脑电图可见额叶癫痫样放电,38%睡眠发作间期动态脑电图可见额叶癫痫样放电,66.7%发作期脑电图可见额叶癫痫样放电;79.8%药物治疗有效,其中29.7%可完全控制.结论 NTLE具有特征性的临床发作特点,发作期及发作间期脑电图改变阳性率不高,临床上应注意鉴别.额叶癫痫容易在夜间发作,睡眠腩电图对NFLE具有重要的诊断价值.