The value of intraoperative electrocorticography in surgical decision making for temporal lobe epilepsy with normal MRI

Purpose: We hypothesized that acute intraoperative electrocorticography (ECoG) might identify a subset of patients with magnetic resonance imaging (MRI)–negative temporal lobe epilepsy (TLE) who could proceed directly to standard anteromesial resection (SAMR), obviating the need for chronic electrode implantation to guide resection. Methods: Patients with TLE and a normal MRI who underwent acute ECoG prior to chronic electrode recording of ictal onsets were evaluated. Intraoperative interictal spikes were classified as mesial (M), lateral (L), or mesial/lateral (ML). Results of the acute ECoG were correlated with the ictal‐onset zone following chronic ECoG. Onsets were also classified as “M,”“L,” or “ML.” Positron emission tomography (PET), scalp‐EEG (electroencephalography), and Wada were evaluated as adjuncts. Key Findings: Sixteen patients fit criteria for inclusion. Outcomes were Engel class I in nine patients, Engel II in two, Engel III in four, and Engel IV in one. Mean postoperative follow‐up was 45.2 months. Scalp EEG and PET correlated with ictal onsets in 69% and 64% of patients, respectively. Wada correlated with onsets in 47% of patients. Acute intraoperative ECoG correlated with seizure onsets on chronic ECoG in all 16 patients. All eight patients with “M” pattern ECoG underwent SAMR, and six (75%) experienced Engel class I outcomes. Three of eight patients with “L” or “ML” onsets (38%) had Engel class I outcomes. Significance: Intraoperative ECoG may be useful in identifying a subset of patients with MRI‐negative TLE who will benefit from SAMR without chronic implantation of electrodes. These patients have uniquely mesial interictal spikes and can go on to have improved postoperative seizure‐free outcomes.     

脑磁图联合颅内电极脑电图在癫痫外科治疗中的应用

目的研究脑磁图(MEG)与颅内电极脑电图(i EEG)联合在癫痫外科治疗中的应用价值。方法应用MEG参与到将行颅内电极埋置患者的术前评估中:根据电-临床症状学、影像学、脑电图、MEG等结果设计出颅内电极埋置方案,进而行颅内电极置入并监测i EEG,捕捉发作期,最终根据定位结果行手术治疗。结果最终成功定位癫痫发作起始区并手术治疗者38例。其中证实为颞叶癫痫(TLE)的16例中,MEG与i EEG定位一致者仅6例,而颞叶以外癫痫(NTLE)22例中两者一致者达16例,两组结果有统计学差异。所有患者术后随访:EngelⅠ级28例,Ⅱ级5例,Ⅲ级3例,Ⅳ级2例。结论 MEG运用于NTLE时较TLE有着更高的与i EEG的一致率。区别于视频脑电图、MRI等其它的无创检查,MEG能够对有创的i EEG电极埋置起到额外指导作用。MEG与i EEG联合,能使电极埋置更合理精确、有针对性,能获得较高的癫痫手术疗效。     

"MRI-negative PET-positive" temporal lobe epilepsy: invasive EEG findings, histopathology, and postoperative outcomes

The aim of this retrospective study was to analyze invasive EEG findings, histopathology, and postoperative outcomes in patients with MRI-negative, PET-positive temporal lobe epilepsy (TLE) (MRI–/PET + TLE) who had undergone epilepsy surgery. We identified 20 patients with MRI-/PET + TLE (8.4% of all patients with TLE who had undergone surgery; 11 men, 9 women). Of the 20 patients, 16 underwent invasive EEG. The temporal pole and hippocampus were involved in the seizure onset zone in 62.5% of the patients. We did not identify a lateral temporal or extratemporal seizure onset in any patient. Of the 20 patients, 17 had follow-up periods > 1 year (mean follow-up = 3.3 years). At the final follow-up, 70.6% patients were classified as Engel I, 5.8% of patients as Engel II, and 11.8% of patients as Engel III and IV (11.8%). Histopathological evaluation showed no structural pathology in any resected hippocampus in 58% of all evaluated temporal poles. The most common pathology of the temporal pole was focal cortical dysplasia type IA or IB. MRI–/PET + TLE should be delineated from other “nonlesional TLE.” The ictal onset in these patients was in each case in the temporal pole or hippocampus, rather than in the lateral temporal neocortex. Standard surgery produced a good postoperative outcome, comparable to that for patients with lesional TLE. Histopathological findings were limited: the most common pathology was focal cortical dysplasia type I.     

Long-term epilepsy surgery outcomes in patients with MRI-negative temporal lobe epilepsy

Purpose: The outcome of surgery in patients with temporal lobe epilepsy (TLE) and normal high‐resolution magnetic resonance imaging (MRI) has been significantly worse than in patients with unilateral hippocampal damage upon MRI. The purpose of this study was to determine the long‐term outcomes of consecutive true MRI‐negative TLE patients who all underwent standardized preoperative evaluation with intracranial electroencephalography (EEG) electrodes. Methods: In this study we present all adult MRI‐negative TLE surgery candidates evaluated between January 1990 and December 2006 at Kuopio Epilepsy Center in Kuopio University Hospital, which provides a national center for epilepsy surgery in Finland. During this period altogether 146 TLE surgery candidates were evaluated with intracranial electrodes, of whom 64 patients with normal high‐resolution MRI were included in this study. Results: Among the 38 patients who finally underwent surgery, at the latest follow‐up (mean 5.8 years), 15 (40%) were free of disabling seizures (Engel class I) and 6 (16%) were seizure‐free (Engel class IA). Twenty‐one (55%) of 38 patients had poor outcomes (Engel class III–IV). Outcomes did not change compared to 12‐month follow‐up. Histopathologic examination failed to reveal any focal pathology in 68% of our MR‐negative cases. Only patients with noncongruent positron emission tomography (PET) results had worse outcomes (p = 0.044). Discussion: Our results suggest that epilepsy surgery outcomes in MRI‐negative TLE patients are comparable with extratemporal epilepsy surgery in general. Seizure outcomes in the long‐term also remain stable. Modern imaging techniques could further improve the postsurgical seizure‐free rate. However, these patients usually require chronic intracranial EEG evaluation to define epileptogenic areas.     

Intractable occipital lobe epilepsy: Clinical characteristics and surgical treatment

Intractable occipital lobe epilepsy remains a surgical challenge. Clinical characteristics of 14 patients were analyzed. Twelve patients had surgery, seven patients had visual auras (50%) and only eight patients (57%) had posterior scalp EEG changes. Ictal single‐proton emission computed tomography (SPECT) incorrectly localized in 7 of 10 patients. Six patients (50%) had Engel’s class I outcome. Patients with inferior occipital seizure onset appeared to fare better (three of four class I) than patients with lateral or medial occipital seizure onset (three of eight class I). Patients who had all three occipital surfaces covered with electrodes had a better outcome (four of five class I) than patients who had limited electroencephalography (EEG) coverage (two of seven class I). Magnetic resonance imaging (MRI) lesions did not guarantee a seizure free outcome. In conclusion, visual auras, scalp EEG, and imaging findings are not reliable for correct identification of occipital onset. Occipital seizure onset can be easily missed in nonlesional epilepsy. Comprehensive intracranial EEG coverage of all three occipital surfaces leads to better outcomes.     

Hyperkinetic seizures in patients with temporal lobe epilepsy: clinical features and outcome after temporal lobe resection

Purpose: Temporal lobe epilepsy (TLE) is usually associated with automatisms. Hyperkinetic seizures are supposed to be unusual. Because we witnessed several patients with TLE and ictal hyperkinetic symptoms, we retrospectively assessed the number, clinical findings, and seizure outcome in such patients who had undergone temporal lobe resection. Methods: We reviewed medical history, video–electroencephalography (EEG) recording and neuroimaging of adult patients who underwent epilepsy surgery for TLE at the Kork Epilepsy Center over the last 20 years with a minimum postoperative follow‐up of 12 months. Key Findings: Among 294 patients who were resected exclusively in the temporal region, we identified 17 (6%) who presented with hyperkinetic semiology such as violent vocalization, complex movements of the proximal segments of the limbs, rotation of the trunk, pelvic thrusting, or early tonic or dystonic posturing. Most of the patients had a preceding aura. Ictal EEG activity was located in the corresponding temporal region, usually with a wide distribution over temporal electrodes with fast spread to unilateral frontal electrodes and to the contralateral side. Neuroimaging revealed extended lesions in the temporal lobe involving mesial and neocortical structures. Most of the patients underwent classical anterior temporal lobe resection including amygdalo‐hippocampectomy. Fourteen patients (82%) became completely seizure‐free (Engel class Ia). Histopathology showed mainly focal cortical dysplasia plus hippocampal sclerosis. Significance: Hyperkinetic seizure semiology may occasionally occur in patients with TLE and is, therefore, no contradiction to the hypothesis of TLE if scalp EEG patterns and neuroimaging findings correspond. The postoperative seizure outcome is favorable in such patients and not different from outcome data in classical TLE.     

Is ‘burned-out hippocampus’ syndrome a distinct electro‐clinical variant of MTLE-HS syndrome?

AimTo study the clinical, electrophysiological and imaging characteristics of patients with unilateral mesial temporal lobe epilepsy (MTLE) with contralateral ictal onset on scalp EEG, viz. ‘burned-out hippocampus’ syndrome (MTLE-BHS).MethodsMTLE-BHS was defined as TLE with unilateral hippocampal sclerosis (HS) without any dual pathology on MRI and contralateral ictal onset on scalp EEG, unlike in classical hippocampal sclerosis (HS). Consecutive “MTLE-BHS” patients evaluated at our Centre for Comprehensive Epilepsy Care from January 2005 to July 2014 were studied. Twenty-five cases of classic MTLE-HS operated during the same period were also analyzed for comparison.ResultsSeventeen patients were diagnosed to have MTLE-BHS. Mean age of seizure onset was 9.5 ± 7.7 years and the mean duration of epilepsy was18.2 ± 7.3 years. Epigastric aura was more common in MTLE-HS and fear, secondary generalized seizures and temporal polar changes on MRI were more prevalent in the MTLE-BHS subgroup. In the latter group, five (29%) exhibited seizure semiology and 2 (12%) had interictal discharges discordant to the side of MTS. Eight (47%) patients in the MTLE-BHS sub-group had normal medial temporal volume on Scheltens scale. Eight patients among MTLE-BHS underwent surgery (4 following intracranial monitoring that localized to the side of HS) with Engel class I outcome at 1 year follow-up in 6 and Engel class II outcome in 2.ConclusionAttenuation of ipsilateral fast ictal rhythms on scalp EEG as well as neocortical changes are likely to be deterministic factors for MTLE-BHS as opposed to the severity of hippocampal atrophy. Considering good post-operative outcomes, intracranial monitoring for surgical selection is not mandatory in MTLE-BHS despite discordant semiology and ictal onset, in the presence of inter-ictal, functional imaging and neuropsychology data concordant to the side of HS.     

Stratifying differences on ictal/interictal subtraction SPECT images

PURPOSE: Subtraction of interictal from ictal single-photon emission computed tomography (SPECT) yields numerous foci that encompass a range of pixel values scattered in the brain. This preliminary study evaluated the significance of this range of values. METHODS: Subtraction images were obtained by registering, normalizing, and subtracting interictal from ictal SPECT for 13 patients. Pixel values of the resulting foci were divided into two groups: group I with 75-100% and group II with 50-75% of the maximal pixel value. Locations of these foci were determined, and concordance with surgical outcomes and scalp and invasive EEG findings was evaluated. RESULTS: In 10 of 13 cases, group I foci showed good concordance with ictal scalp EEG. In addition, group I foci corresponded well to invasive EEG findings in nine of 10 cases. Group I foci had bilateral distributions in seven of 13 cases. In 10 of 13 cases, group I foci corresponded well to regions of surgical resection. Of these 10 patients, nine showed good concordance with scalp EEG, eight showed good invasive EEG concordance, and eight were seizure free after resection. Conversely, group II foci had good concordance with ictal scalp EEG in only five of 13 cases, and invasive EEG findings, in only five of 10 cases. Group II foci had bilateral distributions in 10 of 13 cases. All 10 cases underwent unilateral surgical resections, and all had good surgical outcomes. In six of 13 cases, group II foci showed concordance with surgical sites. Of these six foci, four had poor concordance with scalp EEG, one had poor concordance with invasive EEG, and five had good surgical outcomes. Sensitivity and specificity for seizure localization of Group I foci were 40% and 88% respectively while sensitivity and specificity of Group II foci were 20% and 79% respectively. CONCLUSIONS: Our data demonstrate that foci with 75-100% of maximal pixel values show good concordance with seizure foci, whereas foci of 50-75% may not. Therefore stratifying ictal/interictal differences may improve the specificity and localizing value of subtraction SPECT.     

On the prognostic value of ictal EEG patterns in temporal lobe epilepsy surgery: A cohort study

PurposeTo investigate the prognostic value of ictal scalp EEG patterns in drug-resistant temporal lobe epilepsy associated with hippocampal sclerosis (MTLE-HS) prior to undergoing temporal lobectomy.MethodsScalp EEGs of the first seizure recorded during presurgical long-term video-EEG monitoring of 284 patients were reviewed. Patients were divided according to seizure laterality as either unilateral, when the EEG was restricted to one cerebral hemisphere for the entire seizure, or bilateral, when there was involvement of both hemispheres during the seizure. In patients with unilateral hippocampal sclerosis (HS), seizures were subdivided according to the side of initial ictal activity in relation to the side of the HS, as concordant, non-lateralising or contralateral. Postsurgical seizure outcome, according to Engel's classification, was verified at 1, 2, and 5 years after surgery.ResultsThere was no significant association between ictal EEG characteristics and postsurgical seizure outcome. An Engel I seizure outcome was observed in 87.1% of the patients with unilateral ictal EEGs and in 79.6% of those with bilateral ictal EEGs (p = 0.092).ConclusionAnalysis of the localisation, morphology, and lateralisation of ictal EEG patterns did not provide prognostic information regarding seizure-free status in patients with MTLE-HS undergoing temporal lobectomy.     

Prognostic value of the consistency of lateralizing ictal features and ictal EEG in patients undergoing temporal lobectomy for refractory complex partial seizures.

PURPOSE: Ictal and postictal clinical manifestations have lateralizing value in the presurgical evaluation of intractable seizures. The consistency and frequency of these signs during seizures and the associated implications for postoperative seizure outcome are unknown. METHODS: The videotaped complex partial seizures of 49 patients with known postoperative outcomes greater than 2 years after temporal lobectomy were blindly reviewed for: (1) unilateral hand posturing (UHP), (2) unilateral hand automatism (UHA), (3) forced and nonforced head turning (HT), and (4) postictal dysphasia (PID). The presence and laterality of each assessable sign were recorded. Data were analyzed as follows: (1) the prevalence of each sign in patients with Engel class 1 and Engel class 2-4, and (2) the postsurgical outcome when the sign was present in more than or less than 50% of the seizures for each patient. We reviewed patients' presurgical work-up, specifically ictal EEG and MRI. RESULTS: The prevalence of UHP, UHA, HT, and PID was similar for Engel class 1 and Engel class 2-4 patients. Engel class 1 outcome when UHP, UHA, HT, and PID were present for greater than 50% of seizures was no different compared to when these signs were present for less than 50% of seizures. Patients who had concordant ictal EEG and MRI abnormalities had the best postsurgical outcome. CONCLUSIONS: The consistency and frequency of ictal manifestations in the presurgical evaluation of complex partial seizures does not predict seizure outcome. The presence of any specific lateralizing sign need not be present in every complex partial seizure for the sign to hold predictive value. Concordant ictal EEG and MRI abnormalities are still the best predictors of outcome.     

Posterior quadrant epilepsy surgery: Predictors of outcome

PurposeTo identify predictors of seizure recurrence following posterior quadrant epilepsy surgery.MethodsBetween 1983 and 2008, 43 medically refractory epilepsy patients underwent posterior quadrant epilepsy surgery. Epilepsy surgery involved the occipital lobe in all cases; some cases also included resection of the adjacent parietal or temporal cortex. Using a logistic regression model, we evaluated the relationship between outcome (Engel class I–IV) and 5 outcome predictors: absence of a visual aura, a temporal lobe type aura, versive head movement unaccompanied by a visual aura, non-focal interictal scalp EEG, and surgical pathology other than low grade tumor or cortical dysplasia. We also determined the relative risk for significant post-operative cognitive decline of Wechsler intelligence test score among those receiving complete lobectomies compared to those receiving partial lobectomies.ResultsOverall, outcome was favorable at 1 year following surgery: 22 (51.2%) patients Engel class I, 10 (24%) patients Engel class II, 5 (12%) patients Engel class III, and 6 (14%) patients Engel class IV. The 3 best univariate predictors of seizure recurrence were versive head movement unaccompanied by visual aura, non-focal interictal scalp EEG, and pathology other than low grade tumor or cortical dysplasia. A multivariate predictor combining temporal lobe type aura, versive head movement unaccompanied by visual aura, non-focal interictal scalp EEG, and pathology other than low grade tumor or cortical dysplasia was optimum. Complete lobectomy significantly increased the risk of post-operative decline of Wechsler intelligence score.ConclusionsThese findings indicate that posterior quadrant epilepsy surgery may provide sustained seizure control. A multivariate model combining temporal lobe type aura, versive head movement unaccompanied by a visual aura, non-focal interictal scalp EEG, and pathology other than low grade tumor or cortical dysplasia may contribute to predicting seizure recurrence following posterior quadrant epilepsy surgery. The extent of cortical resection may predict significant cognitive decline in post-operative Wechsler intelligence score.     

Unilateral hippocampal sclerosis with contralateral temporal scalp ictal onset

PURPOSE: To investigate the clinical characteristics and surgical outcomes in patients with unilateral hippocampal sclerosis whose scalp ictal EEG recordings localize to the opposite temporal lobe. METHODS: We retrospectively reviewed the data of all adult patients who had undergone depth electrode implantation for suspected temporal lobe epilepsy (TLE) at UCLA (1993-2000) or the Montreal Neurological Institute (1991-1998) to identify patients who had (a) unilateral hippocampal atrophy, and (b) surface ictal recordings in which the majority of seizures appeared to initiate in the opposite temporal lobe, with few or none that were concordant with the hippocampal atrophy. RESULTS: Of 109 patients with suspected TLE who underwent depth electrode study at the two centers, five patients met the aforementioned criteria. Four of these five had very severe hippocampal atrophy, whereas the fifth had mild atrophy but extensive signal change on magnetic resonance imaging (MRI). Depth electrode recordings in four of the five patients yielded clear ictal onset in the mesial temporal lobe ipsilateral to the imaging abnormality (contralateral to apparent scalp ictal onset). One patient had an unusual bitemporal onset pattern, which was nonetheless suggestive of onset in the sclerotic hippocampus. No patient had intracranial ictal onset contralateral to the imaging abnormality. All patients underwent resection of the structurally abnormal temporal lobe. After follow-up of > or = 2 years, four (80%) of five patients were seizure free, while the fifth showed lesser improvement (class III). CONCLUSIONS: Some patients with severe hippocampal sclerosis (sometimes called a "burned-out hippocampus") have atypical spread of ictal discharges, resulting in apparent gross discordance between imaging and scalp ictal recordings. These patients nonetheless have excellent surgical outcomes on the whole. Whether such patients may forego intracranial recordings requires further study.     

Is ictal recording mandatory in temporal lobe epilepsy? Not when the interictal electroencephalogram and hippocampal atrophy coincide

OBJECTIVE: To investigate the concordance between scalp electroencephalogram (EEG) lateralization and side of hippocampal atrophy in patients with temporal lobe epilepsy (TLE). METHODS: We studied 184 consecutive patients with TLE without lesions other than those compatible with mesial temporal sclerosis. In this study, we studied specifically hippocampal atrophy and the results of scalp EEG investigation. Patients were classified according to the localization of interictal epileptiform discharges as unilateral, bilateral asymmetric, and bilateral symmetric. The EEG seizure onsets were also classified separately as unilateral, bilateral asymmetric, and bilateral symmetric. The hippocampal atrophy was determined by volumetric measurements using high-resolution magnetic resonance imaging (MRIVol). RESULTS: Only 3% of patients had discordance between the ictal and interictal EEG lateralizations; however, none of these had unilateral interictal EEG abnormalities. Interictal EEGs were considered unilateral in 62.0% of patients, bilateral asymmetric in 31.5%, and bilateral symmetric in 6.5%. Ictal EEGs were considered unilateral in 63.5% of patients, bilateral asymmetric in 30.0%, and bilateral symmetric in 6.5%. The MRIVol showed unilateral hippocampal atrophy in 60.9% of patients, bilateral asymmetric hippocampal atrophy in 19.0%, symmetric hippocampal atrophy in 3.8%, and normal volumes in 16.3%. There was a significant concordance between MRIVol lateralization and both interictal and ictal EEG lateralization (P<.001). All patients with unilateral hippocampal atrophy had concordant interictal and ictal EEG lateralization. Six (18.2%) of the 33 patients with bilateral asymmetric hippocampal atrophy had MRI lateralization discordant with EEG lateralization. CONCLUSIONS: We found a strong concordance between EEG and MRIVol lateralization in patients with TLE. Unilateral hippocampal atrophy predicted ipsilateral interictal epileptiform abnormalities and ipsilateral seizure onsets with no false lateralization. Previous studies in addition to the present series support that a concordant outpatient EEG evaluation in patients with TLE and unilateral hippocampal atrophy would obviate the need for inpatient EEG monitoring.     

MRI阴性的颞叶癫痫的外科治疗

目的 总结MRI阴性的颞叶癫痫的手术疗效.方法 对2004年4月至2009年12月间行前颞叶切除的并且MRI为阴性的32例颞叶癫痫患者的资料进行回顾性分析.包括术前检查、手术方式、术后病理及手术疗效.结果 Engel Ⅰ级为21例,占66％;EngelⅡ级为4例,占12％,EngelⅢ～Ⅳ级为7例,占22％,其中头皮视频脑电图痫波位于一侧颞叶的手术效果较好,86％可达到Engel Ⅰ级.结论 对MRI阴性的颞叶癫痫术前评估要更加全面,如检查结果趋于一致,手术效果良好,特别是癫痫样放电起源于一侧颞叶的手术效果更佳.     

The relevance of somatosensory auras in refractory temporal lobe epilepsies

The purpose of this study is to look at the prevalence, characteristics, and prognostic value of somatosensory auras (SSAs) in patients who have undergone temporal lobe epilepsy (TLE) surgery to treat drug‐resistant focal epilepsy. We retrospectively reviewed all patients with drug‐resistant epilepsy who underwent TLE surgery at Cleveland Clinic between 2005 and 2010 (n = 333) to study the prevalence, characteristics, and prognostic implications of SSA in the context of TLE surgery. Analyses were performed using two seizure outcome definitions: complete seizure freedom and Engel classification. Of the 333 patients, 26 (7.8%) had SSA. Almost half (12 patients) had unilateral sensory symptoms, whereas the rest had bilateral symptoms. Tingling and numbness were the most frequently reported sensations. Compared to their non‐SSA counterparts, patients with SSA had the same clinical and imaging characteristics, but had a higher rate of breakthrough seizures (p = 0.03), although most (54%) were still able to achieve Engel class of I (p = 0.02). Based on our results we would encourage detailed presurgical testing, which may include an invasive evaluation to analyze the extent of the epileptogenic zone in patients with SSA and suspected TLE.     

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.     

术前头皮长程视频脑电图表现与颞叶癫痫手术预后的关系

目的 探讨术前头皮长程视频脑电图(VEEG)发作间期放电、发作期起始侧别与颞叶癫痫(TLE)患者手术预后的关系.方法 回顾性分析75例颞叶癫痫手术治疗患者的临床资料.患者术后经过1～9年的随访,根据手术后有、无癫痫发作将患者分为发作组和无发作组.另外按两组患者中术前头皮脑电图发作间期放电及发作期起始侧别分组,比较各组患...     

Interictal indices of temporal seizure origin

Two studies assessed the value of temporal lobe interictal electroencephalographic (EEG) spikes and delta in indicating side of temporal epileptogenesis. The first study determined laterality of spikes/delta in awake recordings of 56 patients whose seizures all began unilaterally as proven by (1) EEG-recorded seizures and (2) >90% improvement after lobectomy. Spikes of 52 (93%) and delta of 46 (82%) patients predominated or appeared exclusively ipsilateral to seizure origin. Neither predominated contralaterally in any patient. The second study investigated laterality of temporal seizures in a separate group of 156 patients with various side vs side spike or delta ratios on 1 to ≥4 awake recordings. Ninety-nine of 104 patients (95%) with temporal spikes on four or more awake recordings had most or all seizures ipsilateral to most spikes, including 79 of 80 (99%) of those with ≥3 side vs side spike ratios. Among the 120 patients with high (≥3) side vs side spike ratios, most or all seizures of 118 (98%) originated ipsilateral to most spikes. Predominant seizure origin also correlated with lateralized arrhythmic delta—from 90% ipsilateral seizures of those with one EEG with delta to 100% with ≥4 such EEGs. Data from these two studies using opposite directions of analysis (seizures ← spikes/delta and spikes/delta → seizures) demonstrate high correlations between laterality of interictal and ictal entities, particularly if temporal spikes clearly predominate on one side and if unilateral temporal delta activity persists over several recordings. Such correlations suggest that the awake interictal scalp EEG cannot be ignored when assessing laterality of temporal epileptogenesis.     

Uncovered primary seizure foci in Lennox-Gastaut syndrome after corpus callosotomy

Purpose

Corpus callosotomy (CC) is a palliative surgical procedure to control atonic, tonic, or generalized tonic-clonic seizure in Lennox-Gastaut syndrome (LGS). Here, we report patients with LGS who underwent resective surgery, following CC better delineating the presumed seizure foci localized in one hemisphere.

Methods

We retrospectively reviewed seven patients with LGS who underwent CC and subsequent cortical resection. The median follow-up duration after lobectomy was 20 months (range, 15-54 months) and three patients had follow-up periods over 24 months. The findings of video electroencephalography (EEG) monitoring, structural and functional neuroimagings were compared between pre- and post-CC.

Results

Four patients had Engel class I and one patient had Engel class II outcomes following cortical resection; post-CC, compared to pre-CC, showed better localized ictal/interictal epileptiform discharges in the unilateral frontal area in two patients, in the unilateral parieto-temporo-occipital areas in one patient and in the unilateral fronto-temporal areas in the remaining two patients. Two patients had Engel Class III outcome following cortical resection; post-CC EEG continued to show multifocal epileptiform discharges but predominantly arising from a unilateral frontal area. Following CC, positron emission tomography showed localized glucose hypometabolism of which location was concordant with post-CC EEG abnormalities in all patient. Similarly, ictal/interictal single photon emission computed tomography also showed localized abnormalities concordant with post-CC EEG abnormalities in five of the six patients. Pathological assessment revealed cortical dysplasia in six patients, whereas no pathological abnormality was found in the remaining patient, who obtained Engel Class I outcome following cortical resection.

Conclusion

CC could change EEG findings, glucose metabolisms and cerebral blood flows, and it is sometimes helpful in delineating the primary seizure focus in patients with LGS.     

Unitemporal vs bitemporal hypometabolism in mesial temporal lobe epilepsy

BACKGROUND: Patients with mesial temporal lobe epilepsy (TLE) often show bilateral temporal hypometabolism (BTH), but the nature of this finding has not been well established. OBJECTIVE: To compare the clinical characteristics between unitemporal hypometabolism (UTH) and BTH patients in mesial TLE. DESIGN: Cross-sectional study. SETTING: Epilepsy center at university hospital in Seoul, Korea. PATIENTS: We enrolled 95 patients with mesial TLE, 87 of whom had subsequently undergone surgery. Seizures, interictal and ictal electroencephalography (EEG), brain magnetic resonance imaging, Wada test, and neuropsychological test results were reviewed. (18)F-fluorodeoxyglucose positron emission tomography scans were interpreted visually. Patients were divided into 2 groups: UTH and BTH. RESULTS: There were 59 UTH patients and 36 BTH patients. Semiologic analysis showed that UTH patients had higher frequencies of aura and unilateral dystonic posturing, whereas BTH patients had higher frequencies of a nonlateralized bilateral ictal EEG pattern and bilateral interictal spikes. Moreover, BTH patients had more frequent symmetric Wada memory scores and white matter changes in the bilateral temporal lobes on brain magnetic resonance imaging than UTH patients. All UTH patients with bilateral TLE on scalp EEG showed unilateral seizure onset on intracranial EEG. CONCLUSIONS: The characteristic clinical findings of mesial TLE with BTH were a more frequent nonlateralized ictal EEG pattern, bitemporal interictal spikes, symmetric Wada memory score, and the anterior temporal white matter changes, and less frequent aura and unilateral dystonic posturing. Surgical outcomes were similar and good in both groups, although surgery could not be performed in 8 BTH patients (22%).