局灶性皮质发育不良所致难治性癫痫的微创神经外科治疗

目的应用神经导航结合术中皮质电极描记,微创治疗局灶性皮质发育不良(focal cortical dysplasia,FCD)所致的难治性癫痫。方法 26例局灶性皮质发育不良所致的难治性癫痫患者,术前常规使用CT、磁共振成像(magnetic resonanceimaging,MRI)、长程视频脑电图(digital video signal and electroencephalogram,VEEG)、磁共振波谱分析(MR Spectroscopy,MRS)等检查,如病灶位于功能区则行功能性磁共振成像(functional magnetic resonance imaging,fMRI)。术中通过神经导航确定的病灶与ECoG确定的致痫灶位置及范围进行对比,了解两者的吻合程度及差异,综合分析后精确并标记出癫痫波的起源位置和范围,将局灶性皮质发育不良病灶和周边的致痫皮质切除;如致痫灶位于功能区或附近,在保留功能区皮质的基础上,给予低功率皮质热灼。结果术后病理结果:26例患者病理标本符合FCD。术后患者无明显并发症出现。根据Engel术后效果分级进行评估,Ⅰ级23例,Ⅱ级2例,Ⅲ级1例。结论神经导航结合术中皮质电极描记在局灶性皮质发育不良所致的难治性癫痫手术中,具有定位准确、损伤少的优点,在切除致痫灶的同时能最大程度保护脑功能。     

皮层脑电图监测下手术治疗继发性癫痫

目的 探讨术中皮层脑电图(ECoG)监测下继发性癫痫的手术治疗效果.方法 选择自2004年9月至2008年1月贵州省人民医院收治的84例继发性癫痫患者行手术治疗,术中通过ECoG定位癫痫灶,显微手术切除原发病变,再根据癫痫发作的临床表现、病灶部位及ECoG监测所提示的异常脑电图波释放情况决定是否进行致痫灶切除及扩大致痫灶切除术,皮层热灼术,前颞叶切除术,海马、杏仁核切除术,胼胝体前部切开术.结果 84例患者切除病变前ECoG均可记录到癫痫波,原发病变切除后即时ECoG监测病变周围可记录到异常癫痫波80例,检出率为95.24%.其中13例致痫波发放区域位于非功能区者对该范围内皮层予以完全切除,术后即时ECoG提示癫痫波消失.67例位于或毗邻重要功能区者,采用低功率热灼该处皮层后,60例癫痫波消失.7例患者经联合胼胝体前部切开和(或)海马、杏仁核切除,术后即时ECoG监测效果满意.术后随访10个月～4年,按Engle标准评定疗效:Ⅰ级56例(66.67%),Ⅱ级21例(25.00%),Ⅲ级4例(4.76%),Ⅳ级3例(3.57%);手术总有效率为96.42%.结论 ECoG监测可明显提高手术治疗继发性癫痫的效果.

Abstract：

Objective To investigate the therapeutic effect of surgical management on patients with secondary epilepsy under the monitoring of cortical electrocorticography (ECoG). Methods Eighty-four patients with secondary epilepsy, admitted to our hospital from September 2004 to January 2008, were chosen; intraoperative ECoG monitoring was performed to locate the epileptic foci before the resection of the primary lesion. After the resection of primary lesion, resection of epileptic foci, enlarged resection of epileptic foci, cortical thermocoagulation, anterior temporal lobectomy,amygdalohippocampectomy and anterior callosotomy were performed, respectively, in different patients according to the clinical manifestations of seizures, and the locations of lesions and epileptic waveform discharges detected by intraoperative ECoG monitoring. Results The epileptic waveform discharges in 84 patients were noted before the resection of primary lesion. The epileptic waves were found in 80patients at the peripheral areas of the primary nidus under immediately postoperative ECoG monitoring,with a relevance ratio reaching 95.24%; after the resection of residual cortical zone with epileptic wave discharges, epileptic wave disappeared on immediately postoperative ECoG in 13 patients whose lesion located in nonfunctional area; normal signals were noted in 60 of the 67 patients performed cortical thermocoagulation whose cortical zone with epileptic wave discharges were located or neighbored in functional area, and good outcomes under the immediately postoperative ECoG monitoring were noted in the other 7 patients performed thermocoagulation combined with anterior callosotomy and/or amygdalohippocampectomy. The follow-up studies for 10 months to 4 years showed that grade Ⅰ in 56patients (66.67%), grade Ⅱ in 21 (25.00%), grade Ⅲ in 4 (4.76%) and grade Ⅳ in 3 (3.57%) according to the Engle standard of curative effect were achieved; the total effective rate was 96. 42%. Conclusion ECoG monitoring can significantly improve the efficiency of surgical management of secondary epilepsy.     

A case of medial temporal lobe epilepsy associated with occult focal cortical dysplasia in the lateral temporal neocortex]

A 29-year-old male with medial temporal lobe epilepsy(MTLE) was revealed to have "occult" focal cortical dysplasia(FCD) in the lateral temporal neocortex. He had no history of febrile convulsion and developed complex partial seizure at the age of 14 year, which became intractable. Although MRI failed to reveal structural abnormality in the temporal lobe, even retrospectively, the findings of non-invasive preoperative examination, such as video-EEG monitoring and interictal ECD-SPECT and FDG-PET, were consistent with those of the left MTLE. Intraoperative electrocorticography(ECoG) demonstrated almost continuous paroxysmal activities on the anterior part of the inferior temporal gyrus(ITG). Anterior temporal lobectomy(ATL) with hippocampectomy was performed. Histological examination revealed FCD in the small area with 0.8 mm in diameter of the resected ITG. In the ATL without preoperative invasive examination such as chronic subdural electrode recording, intraoperative ECoG recording is mandatory.     

MEG predicts epileptic zone in lesional extrahippocampal epilepsy: 12 pediatric surgery cases

PURPOSE: To discover whether the spatial distribution of spike sources determined by magnetoencephalography (MEG) provides reliable information for planning surgery and predicting outcomes in pediatric patients with lesional extrahippocampal epilepsy. METHODS: We retrospectively studied 12 children with extrahippocampal epilepsy secondary to cortical dysplasia (CD), tumor, or porencephalic cyst. We compared interictal MEG spike source locations and somatosensory evoked fields derived from equivalent-current dipole modeling with intraoperative or extraoperative electrocorticography (ECoG). RESULTS: MEG spike sources were found in proximity to the lesion in all patients and extended from lesions in five patients with CD. Marginal spike sources were noted in three patients with tumors, one patient with a cyst, and one with CD, and extramarginal sources in three patients with tumors. Three patients with tumors underwent lesionectomy only; two had further cortical excisions. One patient with CD underwent lesionectomy only, three had lesionectomy and cortical excisions, and two had lesionectomy and multiple subpial transection. Asymmetric MEG spike sources correlated with ECoG findings in all patients. Residual epileptiform discharges on postexcisional ECoG corresponded to spike sources in three patients with tumors and one patient with a cyst. Eleven patients have been seizure free for 1-6 years (mean, 4 years). One patient had residual seizures after incomplete excision of right temporal CD. CONCLUSIONS: MEG delineated asymmetric epileptogenicity surrounding lesions and the eloquent cortex. Complete tumor resection produced favorable outcomes despite residual postexcisional ECoG spikes and extramarginal MEG spike sources. CD characterized by clusters of MEG spike sources within and extending from lesions seen on magnetic resonance imaging (MRI) should be removed to prevent seizures.     

Focal cortical dysplasia: pathophysiological approach

Overview Clinical and experimental studies on focal cortical dysplasia (FCD) were carried out.Materials and methods For the experimental study, an experimental FCD model of rats was developed. Twenty Wistar rats at 0–2 days after birth were used for the study. Kainic acid (KA) solution was injected stereotaxically into medial and lateral sites of the sensori-motor cortex. Bipolar electrodes were inserted in five rats. Their behavior and electroencephalogram (EEG) were recorded using a digital-video-EEG monitoring system. After observation periods of 1, 2, and 6 months, rats were perfused for pathological study. FCD was observed adjacent to the site of KA injection in all rats more than 1 month after the injection.Results and discussions EEG recording demonstrated focal spike discharges in and around the site of injection. However, clinical seizure was not observed. Pathological studies showed decrease in GABA-A receptors and increase in GABA-B receptors not only in the lesion but also in perilesional areas. Fifteen surgical cases of FCD with intractable epilepsy were subjected to the clinical study. Neuro-imaging studies including high-resolution magnetic resonance imaging and single-photon emission computed tomography were performed. Conventional EEG studies demonstrated focal EEG abnormalities with epileptic phenomena. At surgery, intraoperative electrocorticography (ECoG) was performed to localize epileptic foci under neuroleptoanalgesia. Thirteen patients showed epileptiform discharges on preresection ECoG. All foci in non-eloquent areas were resected. Pathological studies including immunohistochemical staining were performed, and the characteristics of the FCD in relation to EEG findings were analyzed. Patients in whom total lesionectomy with complete focus resection was performed had favorable postoperative courses. Nine patients (64.3%) have been seizure-free with reduced medication, and significant improvement was achieved in two patients (14.3%). Electrophysiological examination revealed epileptogenecity not only in the lesions but also in perilesional areas. The immunohistochemical studies showed a decrease in GABA-A receptors and an increase in GABA-B receptors in both the lesions and perilesional areas, but N-methyl-d-aspartate receptors were almost negative in both areas. Glutamate R1 was decreased in both areas, but glutamate R2 was increased in both areas. These findings support the results of a electrophysiological study.Conclusions In conclusion, not only the epileptic property of experimental focal cortical dysplasia but also perilesional epileptogenesis was demonstrated. These findings supported the results of surgery for patients with focal cortical dysplasia. In cases of FCD, total removal of the lesion and resection of the perilesional epileptic focus are needed for a good outcome.     

Microscopic mild focal cortical dysplasia in temporal lobe dual pathology: An electrocorticography study

BackgroundAssociations between electrophysiological and histological findings might provide an insight into the epileptogenicity of mild focal cortical dysplasia (FCD) in patients with temporal lobe epilepsy (TLE) and a dual pathology.Subjects and methodsA total of 22 patients with pharmacoresistant TLE were included in the study, 16 of them with histologically confirmed hippocampal sclerosis (HS) associated with neocortical temporal mild Palmini Type-I FCD subtypes and 6 with HS. Intraoperative electrocorticography (ECoG) recordings were analysed for epileptiform discharge frequency and morphology. Associations between histological, and electrocorticography pattern findings in these patients were analysed. Electroclinical outcomes in these patients were also evaluated.ResultsNeocortical areas with mild Palmini Type-I FCD showed a significantly higher spike frequency (SF) recorded in the inferior temporal gyrus than those neocortical areas in patients with HS. There was a tendency to higher spike frequency and lower amplitude in neocortical areas with histopathologic subtype IB FCD in relation with IA during intraoperative ECoG. Post-SF excision and amplitude were significantly lower during neocortical post-excision intraoperative ECoG than during neocortical pre-excision recording. There was no difference found in the clinical outcome between patients with and without FCD.ConclusionsIntraoperative electrocorticographic interictal spike frequency recorded in the neocortical inferior temporal gyrus may help to characterize the histopathologic subtypes of mild Palmini Type-I FCD in patients with temporal lobe epilepsy (TLE) and a dual pathology. Our data support the epileptogenicity of neocortical mild FCD in TLE and assessments of ECoG patterns are relevant to determine the extent of the resection in these patients which can influence the electroclinical outcome.     

A novel technique of detecting MRI‐negative lesion in focal symptomatic epilepsy: Intraoperative ShearWave Elastography

Focal symptomatic epilepsy is the most common form of epilepsy that can often be cured with surgery. A small proportion of patients with focal symptomatic epilepsy do not have identifiable lesions on magnetic resonance imaging (MRI). The most common pathology in this group is type II focal cortical dysplasia (FCD), which is a subtype of malformative brain lesion associated with medication‐resistant epilepsy. We present a patient with MRI‐negative focal symptomatic epilepsy who underwent invasive electrode recordings. At the time of surgery, a novel ultrasound‐based technique called ShearWave Elastography (SWE) was performed. A 0.5 cc lesion was demonstrated on SWE but was absent on B‐mode ultrasound and 3‐T MRI. Electroencephalography (EEG), positron emission tomography (PET), and magnetoencephalography (MEG) scans demonstrated an abnormality in the right frontal region. On the basis of this finding, a depth electrode was implanted into the lesion. Surgical resection and histology confirmed the lesion to be type IIb FCD. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here .     

伴有癫癇发作的脑内病灶的手术治疗

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ILAE focal cortical dysplasia type IIIc in the ictal onset zone in epileptic patients with solitary meningioangiomatosis

“Solitary” meningioangiomatosis (MA) is a rare, benign, hamartomatous lesion of the cerebral cortex and frequently leads to epilepsy. However, the source of the epileptogenicity in meningioangiomatosis remains controversial. We report two surgically‐treated meningioangiomatosis cases with medically intractable epilepsy. In both cases, chronic subdural electrocorticogram (ECoG) recordings identified the ictal onset zone on apparently normal cortex, adjacent to and/or above the meningioangiomatosis lesion, not on the meningioangiomatosis lesion itself. The ictal onset zone was resected, along with the MA lesion, and good seizure outcome was achieved. Histological examination of the ictal onset zone revealed the presence of ILAE focal cortical dysplasia (FCD) type IIIc. Our case studies suggest that in the surgical management of epilepsy with meningioangiomatosis, it is important to identify undetected, but epileptogenic, ILAE FCD Type IIIc, using preoperative multimodal examinations, including chronic ECoG recordings.     

Correlation between scalp-recorded electroencephalographic and electrocorticographic activities during ictal period.

OBJECTIVE: To investigate the correlation between scalp-recorded electroencephalographic (EEG) and electrocorticographic (ECoG) activities during ictal periods. METHODS: Simultaneous EEG and ECoG recordings with chronic subdural electrodes were performed in eight patients with partial epilepsy. RESULTS: In two cases where the ictal ECoG discharges originated in deep brain structures such as the hippocampus and interhemispheric surface of the frontal lobe, ictal discharges could not be detected on EEG until they expanded to the cortex of convexity. In four cases, the ictal onset zones were located in the lateral convexity. When synchronous or near synchronous ictal ECoG discharges with amplitudes of 200-2000muV were recorded on more than 8-15cm(2) of cortex, corresponding discharges were recorded on EEG in these four cases. However, in a case of frontal lobe epilepsy, asynchronous ictal ECoG discharges were recorded on 10 electrodes of convexity but no ictal EEG activity was recorded. Furthermore, in two frontal lobe epilepsy cases, ictal EEG discharges did not always reflect the ictal ECoG spike, but occasionally reflected slow background ECoG activity around the ictal discharges. CONCLUSIONS: Multiple factors such as the width of the cortical area involved, amplitude of ictal discharges and degree of synchronization of electrical potentials play important roles in the appearance of ictal EEG recordings, and the relationship between ictal EEG and ECoG is not straightforward.     

Limited resection of focal cortical dysplasia and associated epileptogenic cortex may lead to positive surgical outcome

A drug-resistant epilepsy patient with premotor type IIb focal cortical dysplasia is described with a positive postoperative outcome following partial resection of the lesion and epileptogenic zone. Presurgical fMRI of the sensorimotor areas showed haemodynamic responses over the posterior border of the lesion and ictal EEG-fMRI revealed activation of both the primary sensorimotor strip and premotor lesion area. Almost continuous 1-2 Hz interictal spiking was recorded during a chronic ECoG study over the primary sensorimotor cortex. Following partial resection of the lesion, an acute ECoG revealed marked reduction of epileptic activity over the sensorimotor area. Post-operatively, seizure control was significantly improved (class IV ILAE outcome). Although partial FCD resections predict a worse postoperative outcome, individual patients may still respond favourably. The type of lesion, resected portion, and histopathology may be included among factors related to successful outcome.     

开颅手术治疗顽固性癫(癎)138例分析

目的评价顽固性癫痫的致痫灶定位方法和皮层电极监测下致痫灶切除,加行多处软脑膜下横纤维切断术（MST）治疗癫痫的疗效。方法对138例顽固性癫痫病人的致病灶,采用CT＋MRI＋EEC＋单光子发射计算机体层摄影（SPECT）＋皮层脑电图（ECoG）联合检测定位。对检出的阳性病灶在皮层电极监测显微镜下行致痢灶切除,切除后检测仍有癫痫波者加行MST;致痫灶位于重要功能区者单行MST。结果致痫灶阳性检出率86％。皮层电极监测显微镜下致痂灶切除加MST,术后91％的病人癫痫发作停止,一年后约15％的病人复发,但症状较术前减轻,持续时间较术前短。结论CT＋MRI＋EEG＋SPECT＋ECoG联合检测,对手术定位具有较高价值。皮层电极监测下致痫灶切除术及MST创伤轻微、效果比较可靠、治愈率高、并发症少、复发率低。病灶及致痫灶的不完全切除和形成皮层软化及疤痕,可能是导致癫痫复发的重要原因。     

磁共振阴性的局灶性脑皮质发育不良的手术治疗

目的探讨磁共振难以确定病灶的致痫性局灶性脑皮质发育不良的诊断和定位方法,提高手术治疗效果。方法回顾性分析联合应用视频脑电图(VEEG)、脑磁图(MEG)及术中皮层电极脑电图监测(ECo G)检查,诊断、定位并经手术后病理证实为局灶性皮质发育不良(FCD)的24例磁共振检查阴性的难治性癫痫患者的临床资料。结果 24例癫痫患者行手术治疗,病理FCDⅠa型5例,FCDⅠb型3例,FCDⅠc型5例,FCDⅡa型6例,FCDⅡb型5例。术后随访1~5年,EngelⅠ级9例,EngelⅡ级5例,EngelⅢ级8例,EngelⅣ级2例。结论联合应用VEEG、MEG和(或)ECo G技术有助于准确诊断和定位磁共振阴性的FCD,提高FCD致难治性癫痫的手术疗效。     

Spatially filtered magnetoencephalography compared with electrocorticography to identify intrinsically epileptogenic focal cortical dysplasia

This study was carried out to evaluate Synthetic Aperture Magnetometry-kurtosis (SAM(g(2))), a spatially filtered source localization technique in magnetoencephalography (MEG), for identification of epileptogenic areas of focal cortical dysplasia (FCD). Three children with FCD were investigated to localize the ictal onset zone (IOZ). All patients subsequently had extraoperative electrocorticography (ECoG) for intractable epilepsy and surgical resection. SAM(g(2)) analysis showed overlapping of interictal MEG spike sources with the IOZ on ECoG in all children. We recommend MEG-SAM(g(2)) and MEG interictal spike source localization in patients with epileptogenic FCD.     

Feasibility and limitations of magnetoencephalographic detection of epileptic discharges: simultaneous recording of magnetic fields and electrocorticography

Magnetoencephalography (MEG) is considered clinically useful in localizing the epileptogenic focus in partial epilepsy. However, the relationship between the extent of the brain involved in paroxysmal activities and the magnetic field changes at the scalp has not been fully clarified. Furthermore, whether paroxysmal activities generated in deep brain structures such as the hippocampus can be detected magnetically is uncertain. Eight patients with temporal lobe epilepsy and two with extratemporal lobe epilepsy underwent chronic recording from subdural electrodes. Magnetic and electrocorticographic discharges representing epileptic activity were recorded simultaneously. MEG recorded magnetic field changes originating from paroxysmal activity in the superiolateral cerebral cortex when the amplitudes of the electrical paroxysmal activities exceeded 100 microV and extended over more than 3 cm2 of cortical surface. MEG failed to record paroxysmal activity localized to the medial temporal lobe. MEG is often useful in identifying a spike focus in the superiolateral aspects of the cerebral hemisphere, but not discharges arising from the medial temporal lobe. Rapid decay of the magnetic field is likely to be the reason for this limited sensitivity to medial discharges.     

脑皮质发育不良继发顽固性癫痫的病理分型及手术治疗

目的 探讨局灶性脑发育不良(FCD)的临床特征、病理学、影像学的特点及手术疗效.方法 42例外科手术切除致痫灶并经病理证实为FCD的患者中,根据Palmini病理学分型进行分类,并对其临床特征、影像学特点及手术疗效进行回顾性分析.结果 42例患者中,按致痫灶部位分类颢叶24例、额叶14例、顶叶6例及枕叶3例,其中多脑叶5例.术前影像学检查阳性率62%.组织学分型FCDⅠA型9例,FCDⅠB型21例,FCDⅡA型5例,FCDⅡB型7例,其中以FCD Ⅰ B型最为常见,多位于颞叶且常伴有海马硬化.所有患者术后至少随访1年以上,癫痫术后治愈率FCD位于颞叶67%,颞叶以外43%(EngleⅠa).结论 FCD是难治性癫痫常见的病理学改变,其病理分型与临床特征和致痫灶部位存在相关性,为制定手术方案和判定手术效果提供了依据.     

Taylor-type focal cortical dysplasia in infants: some MRI lesions almost disappear with maturation of myelination

Identification of focal cortical dysplasia (FCD) on magnetic resonance (MR) images of young children with refractory focal epilepsy is important, as surgical resection may offer improvement of seizure control and subsequent developmental progress. However, the MR appearances of malformations of cortical development may change during brain maturation. We report 4 children with refractory focal epilepsy, whose MR images in infancy showed localized cortical and subcortical signal abnormalities (hypointense on T(2)-weighted and hyperintense on T(1)-weighted images), suggestive of abnormal cortical development. The visibility of these lesions was significantly reduced on later MR images. Subtle blurring of the gray-white matter junction in these areas was the only indicator of cortical abnormality in 3 patients, which was recognized only after comparison with earlier images. Taylor-type FCD was subsequently confirmed in all patients, following surgical cortical resection of the lesions. MR images performed early within the first year of life in children with epilepsy are important to identify areas of FCD. The appearances of FCD on later scans can be very subtle escaping recognition, and conclusions may be misleading with respect to diagnosis and appropriateness of surgical treatment.     

Multiple focal cortical dysplasias presenting with intractable epilepsy: case report]

A 14-year-old female, who had intractable epilepsy associated with multiple focal cortical dysplasias (FCD), was reported. She developed intractable epilepsy at the age of 7 and was diagnosed as having frontal lobe epilepsy based on the seizure semiology and interictal EEG. MRI revealed multiple lesions in the right frontal, bilateral occipital and left parietal lobes. EEG demonstrated that ictal discharge was preceded by spike on the right frontal region and FDG-PET showed hypometabolic area in the right frontal lobe. Chronic subdural electrode recordings from the right frontal lobe indicated that ictal onset zone was located around the right frontal lesion, especially frontal tip and base, and these areas including the lesion were resected. Postoperatively, residual seizure was noted although seizure frequency was decreased. It is well known that, postoperatively, satisfactory seizure outcome can be obtained in patients with FCD. However, further investigation in terms of surgical indication and strategies for multiple FCD should be needed.     

Neuroimaging of Focal Cortical Dysplasia

Focal cortical dysplasia (FCD) is a common cause of pharmacoresistant epilepsy that is amenable to surgical resective treatment. The identification of structural FCD by magnetic resonance imaging (MRI) can contribute to the detection of the epileptogenic zone and improve the outcome of epilepsy surgery. MR epilepsy protocols that include specific T1 and T2 weighted, and fluid-attenuated inversion recovery (FLAIR) sequences give complementary information about the characteristic imaging features of FCD; focal cortical thickening, blurring of the gray-white junction, high FLAIR signal, and gyral anatomical abnormalities. Novel imaging techniques such as magnetic resonance spectroscopy (MRS), magnetization transfer imaging (MTI), and diffusion tensor imaging (DTI) can improve the sensitivity of MR to localize the anatomical lesion. Functional/metabolic techniques such as positron emission tomography (PET), ictal subtraction single photon emission computed tomography (SPECT), functional MRI (fMRI), and magnetic source imaging (MSI) have the potential to visualize the metabolic, vascular, and epileptogenic properties of the FCD lesion, respectively. Identification of eloquent areas of cortex, to assist in the surgical resection plan, can be obtained non-invasively through the use of fMRI and MSI. Although a significant number of FCD lesions remain unidentified using current neuroimaging techniques, future advances should result in the identification of an increasing number of these cortical malformations.     

Intrinsic epileptogenicity of human dysplastic cortex as suggested by corticography and surgical results

Cortical dysplastic lesions (CDyLs) are often associated with severe partial epilepsies. We describe the electrographic counterpart of this high degree of epileptogenicity, manifested by continuous or frequent rhythmic epileptogenic discharges recorded directly from CDyLs during intraoperative electrocorticography (ECoG). These ictal or continuous epileptogenic discharges (I/CEDs) assumed one of the following three patterns: (1) repetitive electrographic seizures, (2) repetitive bursting discharges, or (3) continuous or quasicontinuous rhythmic spiking. One or more of these patterns were present in 23 of 34 patients (67%) with intractable partial epilepsy associated with CDyLs, and in only 1 of 40 patients (2.5%) with intractable partial epilepsy associated with other types of structural lesions. I/CEDs were usually spatially restricted, thus contrasting with the more widespread interictal ECoG epileptic activity, and tended to colocalize with the magnetic resonance imaging–defined lesion. Completeness of excision of cortical tissue displaying I/CEDs correlated positively with surgical outcome in patients with medically intractable seizures; i.e., three-fourths of the patients in whom it was entirely excised had favorble surgical outcome; in contrast, uniformly poor outcome was observed in those patients in whom areas containing I/CEDs remained in situ. We conclude that CDyLs are highly and intrinsically epileptogenic, and that intraoperative ECoG identification of this intrinsically epileptogenic dysplastic cortical tissue is crucial to decide the extent of excision for best seizure control.