Presurgical Evaluations Research Articles

Cerebral glucose hypometabolism is associated with mitochondrial dysfunction in patients with intractable epilepsy and cortical dysplasia.

Metabolic imaging studies, such as positron emission tomography (PET), allow for an assessment of physiologic functioning of the brain, and [(18)F]fluoro-2-deoxyglucose (FDG)-PET is now a commonly used technique in presurgical epilepsy evaluations. Focal interictal decreases in glucose consumption are often but inconsistently concordant with the ictal onset area, and the underlying mechanisms are poorly understood. The current study tests the hypothesis that areas of glucose hypometabolism, determined by FDG-PET, are associated with mitochondrial dysfunction in patients with medically intractable epilepsy associated with isolated focal cortical dysplasia (FCD). Measures of electron transport chain (ETC) functioning and mitochondrial abnormalities (ETC complex biochemistry, protein kinase B subtype 1 (Akt1), glial fibrillary acidic protein (GFAP)) were assessed in surgical resection specimens that had hypometabolic abnormalities and those that were normal on FDG-PET. Determination of FDG-PET abnormalities was based on coregistration of statistical parametric mapping (SPM) results with postsurgical images. Twenty-two patients (11 male, 11 female; mean age at the time of surgery 10.5 ± 4.4 years), with pathologically confirmed FCD, were included in this retrospective review. Complex IV function was found to be significantly reduced in areas of hypometabolism (p = 0.014), whereas there was a trend toward a significant reduction in complex II and III function in areas of hypometabolism (p = 0.08, p = 0.059, respectively). These decreases were independent of cortical dysplasia severity (p = 0.321) and other clinical epilepsy measures. This study suggests an association between glucose hypometabolism and reduced mitochondrial complex IV functioning, which is independent of the degree of cortical dysplasia. This supports the role of cellular energy failure as a potential mechanism for intractable epilepsy.

Multifractal detrended cross-correlation analysis for epileptic patient in seizure and seizure free status

This paper reports a study of EEG data of epileptic patients in terms of multifractal detrended cross-correlation analysis (MF-DXA). The EEG clinical data were obtained from the EEG Database available with the Clinic of Epileptology of the University Hospital of Bonn, Germany. The data sets (C, D, and E) were taken from five epileptic patients undergoing presurgical evaluations. The data sets consist of intracranial EEG recordings during seizure-free intervals (interictal periods) from within the epileptogenic zone (D) and from the hippocampal formation of the opposite hemisphere of the epileptic patients’ brain, respectively (C). The data set (E) was recorded during seizure activity (ictal periods). MF-DXA is a very rigorous and robust tool for assessment of cross-correlation among two nonlinear time series. The study reveals the degree of cross-correlation is more among seizure and seizure free interval in epileptogenic zone. These data are very significant for diagnosis, onset and prognosis of epileptic patients.

Successful treatment with adjunctive lacosamide in a patient with long term “drug resistant” focal epilepsy

SUMMARYIntroduction.A significant number of patients suffering from epilepsy prove to be resistant to antiepileptic drugs (AEDs). Recent studies, however, suggest that 10–20% of seemingly drug resistant patients may still become seizure-free under the influence of subsequent dosage modifications.Case report.We report on a young man with cryptogenic focal epilepsy. He had his first seizure at the age of fifteen. His seizure frequency was decreased during the following 11 years. However, seizure-freedom was never achieved even though he was treated with twelve to fourteen different AEDs during this time. Intensive presurgical evaluations did not allow identification of a surgically remediable focus. Adjunctive treatment with lacosamide 400 mg/day was not successful. However, the patient became seizure-free immediately after an increase of the lacosamide dose up to 500 mg/day. The patient is now seizure-free for more than two years based on a combination of 500 mg lacosamide and 350 mg lamotrigine, followed by 550 mg and 250 mg, respectively.Discussion and conclusion.This case report highlights that there is always a chance that modifying the medication can result in a drug-resistant epilepsy patient experiencing a significant reduction of seizures and becoming seizure-free. The decisive step in this example was the off-label prescription of a high dose of lacosamide which the patient tolerated well.

Presurgical Evaluations in Children with Pathology Confirmed Focal Cortical Dysplasia (S60.007)

Presurgical Evaluations in Children with Pathology Confirmed Focal Cortical Dysplasia (S60.007)

Is an epilepsy presurgical evaluation necessary for mid‐grade and high‐grade brain tumors presenting with seizures?

Patients with epilepsy caused by mid-grade and high-grade tumors do not usually undergo formal presurgical epilepsy evaluations before tumor resection. However, a minority of these patients may benefit significantly from just such a structured presurgical evaluation especially when seizure freedom or seizure reduction is a surgical aim in addition to total tumor resection. Typical cases comprise patients with multifocal tumors, tumors with bilateral extension, tumors over eloquent cortex, and the need for differentiation of spells of an uncertain nature, for example, epileptic versus psychogenic nonepileptic seizures. If they are epileptic, the definition of the epileptic lesion versus the epileptogenic zone and eloquent cortex can be another reason for monitoring. In addition to noninvasive recordings, invasive studies that use subdural or depths electrodes can be of special importance in these patients, leading to an exact delineation of the epileptogenic zone, usually extending beyond the epileptic lesion, and allow safe differentiation of epileptic from eloquent cortex.

Effects of positioning on radiographic measurements of ankle morphology: a computerized tomography-based simulation study

BackgroundMeasurements of the morphology of the ankle joint, performed mostly for surgical planning of total ankle arthroplasty and for collecting data for total ankle prosthesis design, are often made on planar radiographs, and therefore can be very sensitive to the positioning of the joint during imaging. The current study aimed to compare ankle morphological measurements using CT-generated 2D images with gold standard values obtained from 3D CT data; to determine the sensitivity of the 2D measurements to mal-positioning of the ankle during imaging; and to quantify the repeatability of the 2D measurements under simulated positioning conditions involving random errors.MethodFifty-eight cadaveric ankles fixed in the neutral joint position (standard pose) were CT scanned, and the data were used to simulate lateral and frontal radiographs under various positioning conditions using digitally reconstructed radiographs (DRR).Results and discussionIn the standard pose for imaging, most ankle morphometric parameters measured using 2D images were highly correlated (R > 0.8) to the gold standard values defined by the 3D CT data. For measurements made on the lateral views, the only parameters sensitive to rotational pose errors were longitudinal distances between the most anterior and the most posterior points of the tibial mortise and the tibial profile, which have important implications for determining the optimal cutting level of the bone during arthroplasty. Measurements of the trochlea tali width on the frontal views underestimated the standard values by up to 31.2%, with only a moderate reliability, suggesting that pre-surgical evaluations based on the trochlea tali width should be made with caution in order to avoid inappropriate selection of prosthesis sizes.ConclusionsWhile highly correlated with 3D morphological measurements, some 2D measurements were affected by the bone poses in space during imaging, which may affect surgical decision-making in total ankle arthroplasty, including the amount of bone resection and the selection of the implant sizes. The linear regression equations for the relationship between 2D and 3D measurements will be helpful for correcting the errors in 2D morphometric measurements for clinical applications.

Measurement of disordered eating in bariatric surgery candidates: a systematic review of the literature

Symptoms of disordered eating are common among patients seeking bariatric surgery, and assessment of eating pathology is typical in pre-surgical evaluations. This systematic review evaluates the methods used to assess disordered eating in bariatric surgery candidates. A systematic literature search of papers published from the emergence of bariatric surgery in the literature to March 2012 was conducted to identify original studies measuring eating psychopathology in adults seeking bariatric surgery. One hundred and forty-seven articles were identified, which featured 34 different questionnaires and 45 different interviews used in assessments prior to surgery. Limitations of the literature reviewed included the large variety and application of measures, limited description of assessments, and inconsistency in eating disorder criteria. Results demonstrate a lack of measures designed specifically for an obese sample and limited psychometric evaluation of measures in bariatric surgery candidates. The psychometric data available suggest that interview assessments are critical for accurately identifying binge episodes and diagnostic information, while self-report questionnaires may be beneficial for screening and providing additional information of clinical utility (e.g., eating, shape and weight-related cognitions). The use of validated measures will ensure accurate identification of disordered eating in the pre-surgical population, enabling appropriate targeting of intervention to optimise treatment success. This abstract was presented in the Disordered Eating – Characteristics & Treatment stream of the 2013 ANZAED Conference.

Fifty Consecutive Hemispherectomies

Techniques for achieving hemispheric disconnection in patients with epilepsy continue to evolve. To review the outcomes of the first 50 hemispherectomy surgeries performed by a single surgeon with an emphasis on outcomes, complications, and how these results led to changes in practice. The first 50 hemispherectomy cases performed by the lead author were identified from a prospectively maintained database. Patient demographics, surgical details, clinical outcomes, and complications were critically reviewed. From 2004 to 2012, 50 patients underwent hemispherectomy surgery (mean follow-up time, 3.5 years). Modified lateral hemispherotomy became the preferred technique and was performed on 44 patients. Forty patients (80%) achieved complete seizure freedom (Engel I). Presurgical and postsurgical neuropsychological evaluations demonstrated cognitive stability. Two cases were performed for palliation only. Previous hemispherectomy surgery was associated with worsened seizure outcome (2 of 6 seizure free; P .005). The use of Avitene was associated with a higher incidence of postoperative hydrocephalus (56% vs 18%; P = .03). In modified lateral hemispherotomy patients without the use of Avitene, the incidence of hydrocephalus was 13%. Complications included infection (n = 3), incomplete disconnection requiring reoperation (n = 1), reversible ischemic neurological deficit (n = 1), and craniosynostosis (n = 1). There were no (unanticipated) permanent neurological deficits or deaths. Minor technique modifications were made in response to specific complications. The modified lateral hemispherotomy is effective and safe for both initial and revision hemispherectomy surgery. Avitene use appears to result in a greater incidence of postoperative hydrocephalus.

O2-D-34. Functional mapping of praxis network: A combined direct cortical stimulation and CCEP study

The objective of our study is to elucidate a blueprint of the lateral parieto-frontal network for praxis by means of cortical stimulation. We employed two patients with intractable partial epilepsy, who underwent chronic subdural electrode implantation in the left parietal and frontal lobes for presurgical evaluations. 50 Hz electrical cortical stimulation was performed to map the cortical areas essential for language, motor functions and praxis. To investigate the functional connectivity, cortico-cortical evoked potentials (CCEPs) were employed. 50 Hz stimulation at the left supramarginal gyrus (SMG) elicited inability to pantomime the tool use in both patients while they were able to name and use the tools actually. CCEPs revealed site-specific connections from the SMG to the ventral premotor area (PMv), where 50 Hz cortical stimulation revealed negative motor responses. We successfully differentiated functional roles of the SMG and the PMv among praxis-related network. Negative motor response at the PMv could be explained as arrest of movements (i.e. extreme apraxia of fine movements) while impairment of tool-use pantomime at the SMG as ideomotor apraxia. A combined method of 50 Hz cortical stimulation and CCEP study is clinically useful to map the praxis network.

Mental health evaluations for adolescents prior to bariatric surgery: a review of existing practices and a specific example of assessment procedures

Best practice guidelines for adolescents considering bariatric surgery recommend a pre-operative mental health evaluation. However, only general information about these assessments appears in the literature, which makes consistency of administration challenging. This review proposes a specific empirically-derived format for pre-surgical mental health evaluations and summarizes currently available data on the psychiatric functioning of adolescents seeking bariatric surgery. Studies of mental health evaluations for adults preparing for bariatric surgery are reviewed, as is the limited literature relevant to adolescent evaluations. A specific and detailed example of an evaluation (clinical interview, self-report questionnaires, cognitive assessment) used for younger patients at a major metropolitan hospital center is presented, followed by data from an initial group of adolescents completing this evaluation. 200 adolescents (n=139 female; age: 14-18 y, BMI: 35.4-83.3 kg/m2) presenting for bariatric surgery. A notable subset of adolescents reported current Axis I conditions (31.5%) and current mental health treatment (29.5%), but reports of current illicit drug use (1.5%) and regular alcohol use (0.5%) were relatively rare. Procedures for using the completed evaluation and post-surgery monitoring of psychosocial issues are discussed. Adolescents considering weight loss surgery should receive comprehensive pre-surgical mental health evaluations, but additional data are needed to develop specific recommendations the use of these evaluations in post-operative care.

Reduction genioplasty enhances quality of life in female patients with prognathism and maxillary hypoplasia undergoing bimaxillary osteotomy

The structure of the chin determines facial attractiveness and is directly linked to quality of life (QoL). In patients with prognathism and maxillary hypoplasia, bimaxillary osteotomy (BIMAX) with mandibular setback does not always lead to a more slender chin or improved aesthetics. The aim of the present study was to evaluate whether QoL differed between females undergoing BIMAX alone (group I; n=30) and those undergoing BIMAX combined with reduction genioplasty (group II; n=30). Presurgical and postsurgical evaluations included cephalography, photogrammetry, and the Oral Health Impact Profile with one additional domain (aesthetics). Setback of the hard tissue pogonion was significantly greater (P=0.006) in group II (7.1mm) than in group I (2.7mm). Only in group II were soft tissue pogonion changes highly significant (P<0.001), amounting to a mean of 5mm. In both groups, the QoL domains ‘social disability’, ‘psychological discomfort’, and ‘dissatisfied with aesthetics’ changed significantly towards lower impact scores. Changes in the latter two domains were significantly greater in group II patients than in group I patients (P=0.021; P<0.001) and were correlated with changes in the soft tissue pogonion in the horizontal (P=0.024; P=0.022) and vertical directions (P=0.037; P=0.042). Genioplasty addresses both psychological and aesthetic concerns, and therefore significantly enhances postsurgical QoL.

Confirmatory factor analysis of the Beck Depression Inventory-II in bariatric surgery candidates.

Screening for depression is an integral part of psychological evaluations conducted prior to bariatric surgery. The Beck Depression Inventory-II (BDI-II) is the most commonly used measure of depression in these treatment evaluations. The reliability and validity of the BDI-II has not yet been evaluated within bariatric surgery-seeking samples, evidencing a significant gap in the present literature. The purpose of the present study is to evaluate the structural validity of the BDI-II and to examine the reliability and convergent and criterion validity of this instrument within a bariatric surgery-seeking sample. The study population consisted of 505 ethnically diverse bariatric surgery candidates presenting for presurgical psychological evaluations in a midwestern urban academic medical center. Confirmatory factor analytic results indicated that a 3-factor model consisting of affective, cognitive, and somatic factors was the best fitting model of depression within this sample. Internal consistency reliability was satisfactory for each subscale, ranging from .72 to .82. Moderate to large correlations were observed between each BDI-II subscale and a measure of depression previously validated with bariatric surgery candidates indicating adequate convergent validity. On the basis of clinical interview, 14% of the sample was diagnosed with current major depression. Significant mean differences were observed between depressed and nondepressed patients with respect to each BDI-II subscale score, demonstrating criterion-related validity. The BDI-II is a reliable and valid measure of depression for bariatric surgery candidates. Understanding the factor structure of the BDI-II can be useful for planning potential presurgical psychological interventions.

Information source in multiple MEG spike clusters can be identified by effective connectivity in focal cortical dysplasia

It has been reported that patients with a single MEG spike cluster have better postoperative outcomes compared to patients with multiple clusters. However, the problem of identifying a genuine source in the multiple MEG spike clusters remains unsolved. The aim of this study was to determine the focus of the epileptic activity in a situation with multiple MEG spike clusters. Five patients with intractable epilepsy with multiple MEG spike clusters were retrospectively investigated. They had pathologically proven type IA focal cortical dysplasia (FCD) with discordant multimodal presurgical evaluations, and showed a favorable postoperative outcome. MEG spikes were localized and clustered using a hierarchical clustering method. Then, effective connectivity (a phase-slope index method) referring to the causal interaction between distant structures in the brain was applied to the source waveforms extracted from the multiple MEG spike clusters. Finally, the information source, that is, the driver region between multiple clusters, could be identified. We found that 4 of the 5 FCD patients exhibited the driver regions were coincident with the resection area, which was also quite consistent at different epochs. Our results suggest that effective connectivity analysis has a potential value as a presurgical evaluation when multiple MEG spike clusters are found.

Localization of epileptogenic zones in Lennox–Gastaut syndrome using frequency domain source imaging of intracranial electroencephalography: a preliminary investigation

Although intracranial electroencephalography (iEEG) has been widely used to localize epileptogenic zones in epilepsy, visual inspection of iEEG recordings does not always result in a favorable surgical outcome, especially in secondary generalized epilepsy such as Lennox–Gastaut syndrome (LGS). Various computational iEEG analysis methods have recently been introduced to confirm the visual inspection results. Of these methods, high gamma oscillation in iEEG has attracted interest because a series of studies have reported a close relationship between epileptogenic zones and cortical areas with high gamma oscillation. Meanwhile, frequency domain source imaging of EEG and MEG oscillations has proven to be a useful auxiliary tool for identifying rough locations of epileptogenic zones. To the best of our knowledge, however, frequency domain source imaging of high gamma iEEG oscillations has not been studied. In this study, we investigated whether the iEEG-based frequency domain source imaging of high gamma oscillation (60–100 Hz) would be a useful supplementary tool for identifying epileptogenic zones in patients with secondary generalized epilepsy. The method was applied to three successfully operated on LGS patients, whose iEEG contained some ictal events with distinct high gamma oscillations before seizure onset. The resultant cortical source distributions were compared with surgical resection areas and with high gamma spectral power distributions on the intracranial sensor plane. While the results of the sensor-level analyses contained many spurious activities, the results of frequency domain source imaging coincided better with the surgical resection areas, suggesting that the frequency domain source imaging of iEEG high gamma oscillations might help enhance the accuracy of pre-surgical evaluations of patients with secondary generalized epilepsy.

Surgical treatment of refractory epilepsy after chemotherapy in two children with leukemia.

Refractory epilepsy is a rare, long-term complication in children with acute leukemia who are receiving chemotherapy. A few studies have reported cases of several patients who developed recurrent complex partial seizures after the initiation of chemotherapy. In these cases, the cause of the refractory seizures was identified as mesial temporal lobe sclerosis. Here, we report on two patients with extratemporal lesions accompanied by refractory seizures, a long-term complication of acute lymphocytic leukemia. Using presurgical evaluations and measures of the surgical outcomes, the lesions were identified as epileptogenic and were located in the mesial temporal lobe. The underlying pathophysiological background is discussed to aid in understanding this uncommon long-term complication.

Temporal trends in pre-surgical evaluations and epilepsy surgery in the U.S. from 1998 to 2009

To analyze trends in utilization of pre-surgical evaluations including video-EEG (VEEG) monitoring, intracranial EEG (IEEG) monitoring, and epilepsy surgery from 1998 to 2009 in the U.S. Data from the Nationwide Inpatient Sample were used to identify admissions for pre-surgical evaluations and surgery. Surgical treatment of epilepsy was identified by the presence of primary ICD-9-CM procedure codes 01.52 (hemispherectomy), 01.53 (lobectomy), or 01.59 (other excision of the brain, including amygdalohippocampectomy). We calculated annual rates of pre-surgical evaluations and surgery based on published estimates of prevalence of epilepsy in the U.S. In addition, we examined variations by region and hospital characteristics, and conducted multivariable analysis to detect temporal trends, adjusting for changes in the population. Sensitivity analysis was also conducted using different algorithms to identify the study population and outcomes. We detected an increase in the rate of hospitalizations related to intractable epilepsy. Similarly, we noted a significant increase in hospitalizations for VEEG monitoring, but not in IEEG monitoring or in surgery. Multivariable analysis and sensitivity analysis confirmed these results. In addition, there was a significant increase in the proportion of pre-surgical evaluations and surgery performed in non-teaching hospitals. Despite the increase in VEEG monitoring, the availability of guideline and evidences demonstrating benefits of epilepsy surgery was not associated with a greater employment of surgery over time. Nevertheless, access to pre-surgical evaluations and epilepsy surgery is no longer limited to large medical centers.

Stability of synchronization clusters and seizurability in temporal lobe epilepsy.

PurposeIdentification of critical areas in presurgical evaluations of patients with temporal lobe epilepsy is the most important step prior to resection. According to the “epileptic focus model”, localization of seizure onset zones is the main task to be accomplished. Nevertheless, a significant minority of epileptic patients continue to experience seizures after surgery (even when the focus is correctly located), an observation that is difficult to explain under this approach. However, if attention is shifted from a specific cortical location toward the network properties themselves, then the epileptic network model does allow us to explain unsuccessful surgical outcomes.MethodsThe intraoperative electrocorticography records of 20 patients with temporal lobe epilepsy were analyzed in search of interictal synchronization clusters. Synchronization was analyzed, and the stability of highly synchronized areas was quantified. Surrogate data were constructed and used to statistically validate the results. Our results show the existence of highly localized and stable synchronization areas in both the lateral and the mesial areas of the temporal lobe ipsilateral to the clinical seizures. Synchronization areas seem to play a central role in the capacity of the epileptic network to generate clinical seizures. Resection of stable synchronization areas is associated with elimination of seizures; nonresection of synchronization clusters is associated with the persistence of seizures after surgery.DiscussionWe suggest that synchronization clusters and their stability play a central role in the epileptic network, favoring seizure onset and propagation. We further speculate that the stability distribution of these synchronization areas would differentiate normal from pathologic cases.

Lateralization of temporal lobe epilepsy using resting functional magnetic resonance imaging connectivity of hippocampal networks

Early surgical intervention can be advantageous in the treatment of refractory temporal lobe epilepsy (TLE). The success of TLE surgery relies on accurate lateralization of the seizure onset. The purpose of this study was to determine whether resting functional MRI (fMRI) connectivity mapping of the hippocampus has the potential to complement conventional presurgical evaluations in distinguishing left from right TLE. In addition, we sought to determine whether this same network might separate patients with favorable from unfavorable postoperative outcomes. Resting fMRI acquisitions were performed on 21 patients with TLE and 15 healthy controls. The patients included seven patients with left TLE and seven patients with right TLE with seizure-free postoperative outcome, and five patients with left TLE and two patients with right TLE with recurring seizures after surgery. Functional connectivity maps to each hippocampus were determined for each subject and were compared between the controls and the seizure-free patients with left TLE and with right TLE. The one network identified was then quantified in the patients with TLE and recurring seizures. The resting functional connectivity between the right hippocampus and the ventral lateral nucleus of the right thalamus was the most statistically significant network to distinguish between seizure-free patients with left TLE and with right TLE with high sensitivity and specificity. This connectivity was also significantly greater in the seizure-free patients with left TLE than the healthy controls. Finally, six of the seven patients in whom seizures recurred after surgery had connectivity values in this network unlike those who were seizure-free. This study identified a region in the ventral lateral nucleus of the right thalamus whose connectivity to the hippocampi separates left from right TLE subjects. This suggests that the quantification of resting-state functional magnetic resonance imaging (MRI) connectivity across this network may be a potential indicator of lateralization of TLE that may be added to other presurgical MRI assessments. Further validation in a larger, independent cohort is required.

Glissandi: transient fast electrocorticographic oscillations of steadily increasing frequency, explained by temporally increasing gap junction conductance

We describe a form of very fast oscillation (VFO) in patient electrocorticography (ECoG) recordings, that can occur prior to ictal events, in which the frequency increases steadily from ≈ 30-40 to >120 Hz, over a period of seconds. We dub these events "glissandi" and describe a possible model for them. Four patients with epilepsy had presurgical evaluations (with ECoG obtained in two of them), and excised tissue was studied in vitro, from three of the patients. Glissandi were seen spontaneously in vitro, associated with ictal events-using acute slices of rat neocortex-and they were simulated using a network model of 15,000 detailed layer V pyramidal neurons, coupled by gap junctions. Glissandi were observed to arise from human temporal neocortex. In vitro, they lasted 0.2-4.1 s, prior to ictal onset. Similar events were observed in the rat in vitro in layer V of frontal neocortex when alkaline solution was pressure-ejected; glissandi persisted when γ-aminobutyric acid A (GABA(A)), GABA(B), and N-methyl-d-aspartate (NMDA), and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors were blocked. Nonalkaline conditions prevented glissando generation. In network simulations it was found that steadily increasing gap junction conductance would lead to the observed steady increase in VFO field frequency. This occurred because increasing gap junction conductance shortened the time required for an action potential to cross from cell to cell. The in vitro and modeling data are consistent with the hypothesis that glissandi arise when pyramidal cell gap junction conductances rise over time, possibly as a result of an alkaline fluctuation in brain pH.

Effect of magnetoencephalography on intracranial electrode placement strategy in intractable partial epilepsy

Objective To study whether magnetoencephalography (MEG) could indicate intracranial electroencephalography(icEEG) by affecting electrode placement and localization of the seizure onset zone,and then improve the curative effect of the surgical patients of refractory partial epilepsy.Methods Of all consecutive epilepsy surgery candidates between 2009 -2010,83 cases who meet the refractory partial epilepsy diagnostic criteria were prospectively enrolled in this research.The 83 patients were randomly divided into two groups.In one group (MEG + icEEG group),including 43 patients,the MEG results were provided to affect the initial intracranial electrodes placement decision which was based on case -history,semilogy,EEG,MRI.By contrast,for the other group(icEEG group),including 40 patients,the MEG localization results were not provided.All patients underwent epileptogenic foci surgical resection.The follow-up was performed at least 12 months after the operation.The surgical outcome was evaluated by Engel curative effect grading.Engel Ⅰ,Ⅱ,Ⅲ was defined as effectiv whereas Engel Ⅳ was recognized as invalid.Results According to the surgical outcome of icEEG group,23 patients (54％) obtained good postsurgical seizure outcome.While in MEG + icEEG group,the rate was 78％ (31/40).There was statistically significant difference between the two groups(x2 =5.256,P =0.022).Conclusions MEG spike localization could affect icEEG by indicating the electrodes placement,increasing the chance that the seizure onset zone is sampled and improving diagnostic yield of icEEG when patients undergo icEEG for presurgical epilepsy evaluations,finally promote the effectiveness of the surgical resection. Key words: Magnetoencephalography; Intracranial electroencephalography; Epilepsy; Surgery