Tool For Presurgical Evaluation Research Articles

Genetic testing, another important tool in presurgical evaluation of focal epilepsies in childhood.

Epilepsy surgery may be a curative therapy for patients with drug-resistant epilepsies when focal lesions or foci are identified. Genetic testing is not yet routinely included in many presurgical evaluation programs although recent evidence support that finding a germline genetic mutation could help to better delineate the patient candidacy to surgery and provide valuable information on the expected surgery outcome. In this study, we report nine patients presenting drug-resistant focal epilepsy enrolled in presurgical evaluation. We show how the identification of genetic pathogenic variant in epilepsy known genes led to the interruption of the presurgical work-up and ruled out surgery in 7 of them. We observed that the co-existence of some recurrent clinical characteristics as early seizures' onset, frequent precipitating factors including fever, and developmental delay or intellectual disability may be useful markers for germline genetic pathogenic variants. In this group, genetic assessment should be mandatory during presurgical work up, mainly in patients with negative magnetic resonance imaging (MRI) or doubtful structural lesions. The integration of next generation targeted sequencing into the presurgical evaluation can improve the selection of candidates for resective surgery and fosters a personalized medicine approach with a better outcome. PLAINE LANGUAGE ABSTRACT: Genetic testing is not yet systematically included in the pre-surgical assessment of patients with drug-resistant focal epilepsies. In this study, through the description of nine patients, we underline how the integration of genomics into the presurgical work up can help in evaluating the patient candidacy to surgery and provide valuable information on expected surgery outcome.

Role of magnetoencephalography in predicting the epileptogenic zone and post-operative seizure outcome - A retrospective study

PurposeStudy assessed the role of MSI in predicting the post-operative seizure outcome. MethodsThis retrospective study included patients who underwent MEG and epilepsy surgery and had a minimum 6 months of postoperative follow-up. Concordance of MEG cluster with post-surgical resection cavity was classified as follows Class I) Concordant and region-specific, Class II) Concordant and region non-specific, Class III) Concordant lateralization only and Class IV) Discordant lateralization. The relationship between MSI concordance and post-operative seizure outcome was assessed. ResultsA total of 183 patients (M: F = 109:74) were included. The mean age at onset of seizures: 8.0 ± 6.4 years. The dipoles were frequent in 123(67.2 %). The primary cluster orientation was regular in 59 (32.2 %) and mixed in 124 (67.8 %) patients. Concordance between MEG and resection cavity: Class I - 124 (67.8 %), class II- 30 (16.4 %), class III- 23 (12.6 %), and class IV- 6 (3.3 %). The post-surgically mean duration of follow-up was 19.52 ± 11.27 months. At 6-month follow-up period, 144 (78.7 %) patients had complete seizure freedom out of which 106 (73.6 %) had class I concordance. Concordance of MEG with resection cavity was associated with a good outcome at 6 months (p = 0.001), 1 year (p = 0.001), 2 years (p = 0.0005) and 5 years (p = 0.04). MEG cluster characteristics had no association with seizure outcome except the strength of the cluster and outcome at 3 years (p = 0.02) follow-up. ConclusionThe study supports that the complete resection of the MEG cluster had high chance of seizure-freedom and can be used as a complementary noninvasive presurgical evaluation tool.

Use, experience and perspectives of high-density EEG among Italian epilepsy centers: a national survey.

High-density EEG (hdEEG) is a validated tool in presurgical evaluation of people with epilepsy. The aim of this national survey is to estimate diffusion and knowledge of hdEEG to develop a network among Italian epilepsy centers. A survey of 16 items (and 15 additional items) was distributed nationwide by email to all members of the Italian League Against Epilepsy and the Italian Society of Clinical Neurophysiology. The data obtained were analyzed using descriptive statistics. A total of 104 respondents were collected from 85 centers, 82% from the Centre-North of Italy; 27% of the respondents had a hdEEG. The main applications were for epileptogenic focus characterization in the pre-surgical evaluation (35%), biomarker research (35%) and scientific activity (30%). The greatest obstacles to hdEEG were economic resources (35%), acquisition of dedicated personnel (30%) and finding expertise (17%). Dissemination was limited by difficulties in finding expertise and dedicated personnel (74%) more than buying devices (9%); 43% of the respondents have already published hdEEG data, and 91% of centers were available to participate in multicenter hdEEG studies, helping in both pre-processing and analysis. Eighty-nine percent of respondents would be interested in referring patients to centers with established experience for clinical and research purposes. In Italy, hdEEG is mainly used in third-level epilepsy centers for research and clinical purposes. HdEEG diffusion is limited not only by costs but also by lack of trained personnel. Italian centers demonstrated a high interest in educational initiatives on hdEEG as well as in clinical and research collaborations.

Does Stereoelectroencephalography Add Value in Patients with Lesional Epilepsy?

Stereoelectroencephalography (SEEG) has gained popularity as an invasive monitoring modality for epileptogenic zone (EZ) localization. The need and indications for SEEG in patients with evident brain lesions or associated abnormalities on imaging is debated. We report our experience with SEEG as a presurgical evaluation tool for patients with lesional epilepsy. A retrospective cohort study was performed of 131 patients with lesional or magnetic resonance imaging abnormality-associated medically refractory focal epilepsy who underwent resections from 2010 to 2017. Seventy-one patients had SEEG followed by resection, and 60 had no invasive recordings. Volumetric analysis of resection cavities from 3T magnetic resonance imaging was performed. Mean lesion and resection volumes for SEEG and non-SEEG were 16.2 (standard deviation [SD]= 29) versus 23.7 cm3 (SD= 38.4) and 28.1 (SD= 23.2) versus 43.6 cm3 (SD= 43.5), respectively (P= 0.009). Comparing patients with seizure recurrence and patients who remained seizure free, significantly associated variables with seizure recurrence included mean number of failed antiseizure medications (6.86 [SD= 0.32] vs. 5.75 [SD= 0.32]; P= 0.01) and in SEEG patients the mean number of electrodes implanted (8.1 [SD= 0.8] vs. 5.0 [SD= 0.8]; P= 0.005). After multivariate analysis, only failed numbers of medication remained significantly associated with seizure recurrence. Seizure outcomes did not correlate with final resection volume after SEEG evaluation. SEEG evaluation presurgically can be used to maintain the efficacy of resection and decrease the volume and subsequent risk of extensive tissue removal. We believe that this technology allows resective surgery to proceed in a subpopulation of patients with lesional epilepsy who may otherwise not have been considered surgical candidates.

Proximity of the mandibular anterior root apices to the buccal bone surface: A cone-beam computed tomographic study

Aim: The aim of this study is to evaluate the distance from the buccal cortical bone surface to the root apex in the anterior mandibular teeth using cone-beam computed tomography (CBCT) and to correlate it to various associated factors (tooth type, gender, and age).Materials and Methods: CBCT images of mandibular anterior teeth from 120 patient records with a sample size of 360 teeth were analyzed. The distance from the buccal bone surface to root apex and 3 mm above the root apex in the sagittal view was reconstructed using the Romexis software version 3.2.1.Results: Distances from the buccal cortical bone surface to the apices of the root and 3 mm from the apex of the root were greater at the mandibular canine region than the central and lateral incisor (P < 0.001). The buccal bone was significantly thicker corresponding to the apices of the teeth compared to the region 3 mm from the apex (P < 0.001) The mean distance value from the cortical buccal bone surface to the lateral incisor apex (4.03 mm) was significant more among females (P = 0.006). Furthermore, the measured distance at the root apex and 3 mm above the of the root apex of the mandibular anterior roots were significantly more in patients below the age of 40 years (P < 0.05).Conclusion: The distance from the buccal bone's surface to the apex and 3 mm from the apex in the mandibular anterior region is significantly affected by the tooth type and patients' age. CBCT is a reliable tool for presurgical evaluation for both these parameters during endodontic surgeries and implant placement.

Developing fMRI protocol for clinical use Comparison of 6 Arabic paradigms for brain language mapping in native Arabic speakers.

Objectives:To assess a baseline assessment using developed functional magnetic resonance imaging (fMRI) language paradigms for Arabic-speakers.Methods:24-healthy right-handed volunteers scanned on a 3.0 Tesla MRI machine. For fMRI, a BOLD-sensitive sequence used to measure signals over time across 6 language paradigms: rhyming (RH), semantic category generations (SCG), silent word generation (SWG), verb generation picture (VGp), verb generation word (VGw), and verb generation audio (VGa). fMRI data was analyzed using FMRIB Software Library (FSL).Results:We found that VGa, SWG, VGw and VGp robustly activated language-related regions in the dominant hemisphere. RH and SCG failed to adequately define these activation regions but this may be related to the study’s preliminary nature and limitations. After assessment of their validity, considerable activation of the inferior frontal gyrus during VGa, SWG, VGw and VGp suggests that these paradigms have the potential for localizing of Broca’s area in native Arabic speakers.Conclusion:Set of well adapted, and evidence-based, fMRI paradigms were established for Arabic-speakers to enable accurate and sufficient localization and lateralization of the language area. After validation, these paradigms may provide sequences for accurate localization of brain language areas, and could be used as a presurgical evaluation tool.

A new scoring system for predicting extent of resection in medial sphenoid wing meningiomas based on three-dimensional multimodality fusion imaging

BackgroundThree-dimensional (3D) fusion imaging has been proved to be a promising neurosurgical tool for presurgical evaluation of tumor removal. We aim to develop a scoring system based on this new tool to predict the resection grade of medial sphenoid wing meningiomas (mSWM) intuitively.MethodsWe included 46 patients treated for mSWM from 2014 to 2019 to evaluate their tumors’ location, volume, cavernous sinus involvement, vascular encasement, and bone invasion by 3D multimodality fusion imaging. A scoring system based on the significant parameters detected by statistical analysis was created and evaluated.ResultsThe tumor volumes ranged from 0.8 cm3 to 171.9 cm3. A total of 39 (84.8%) patients had arterial involvement. Cavernous sinus (CS) involvement was observed in 23 patients (50.0%) and bone invasion was noted in 10 patients (21.7%). Simpson I resection was achieved in 10 patients (21.7%) and Simpson II resection was achieved in 17 patients (37.0%). Fifteen patients (32.6%) underwent Simpson III resection and 4 patients (8.7%) underwent Simpson IV resections. A scoring system was created. The score ranged from 1 to 10 and the mean score of our patients was 5.3 ± 2.8. Strong positive monotonic correlation existed between the score and resection grade (Rs = 0.772, P < 0.001). The scoring system had good predictive capacity with an accuracy of 69.60%.ConclusionsWe described a scoring system that enabled neurosurgeons to predict extent of resection and outcomes for mSWM preoperatively with 3D multimodality fusion imaging.Trial registrationRetrospectively registered

Outcomes of stereoelectroencephalography exploration at an epilepsy surgery center.

Epilepsy surgery is offered in resistant focal epilepsy. Non-invasive investigations like scalp video EEG monitoring (SVEM) help delineate epileptogenic zone. Complex cases may require intracranial video EEG monitoring (IVEM). Stereoelectroencephalography (SEEG)-based intracerebral electrode implantation has better spatial resolution, lower morbidity, better tolerance, and superiority in sampling deep structures. Our objectives were to assess IVEM using SEEG with regard to reasoning behind implantation, course, surgical interventions, and outcomes. Seventy-two admissions for SEEG from January 2014 to December 2018 were included in the study. Demographic and clinical data were retrospectively collected. The cohort comprised of 69 adults of which 34 (47%) had lesional MRI. Reasons for SEEG consideringall cases includednon-localizing ictal onset (76%), ictal-interictal discordance (21%), discordant semiology (17%), proximity to eloquent cortex (33%), nuclear imaging discordance (34%), and discordance with neuropsychology (19%). Among lesional cases, additional reasons included SVEM discordance (68%) and dual or multiple pathology (47%). Forty-eight patients (67%) were offered resective surgery, and 41 underwent it. Twenty-three (56%) had at least one year post-surgical follow-up of which 14 (61%) had Engels class I outcome. Of the remaining 23 who were continued on medical management, 4 (17%) became seizure-free and 12 (51%) had reduction in seizure frequency. SEEG monitoring is an important and safe tool for presurgical evaluation with good surgical and non-surgical outcomes. Whether seizure freedom following non-surgical management could be related to SEEG implantation, medication change, or natural course needs to be determined.

Presurgical evaluation of basal cell carcinoma using combined reflectance confocal microscopy–optical coherence tomography: A prospective study

Initial biopsy of basal cell carcinoma (BCC) may fail to show aggressive histologic subtypes. Additionality, the clinical evaluation of BCC before surgery can miss subclinical extension. Reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) are emerging tools that can help in the presurgical evaluation of BCCs. To assess the feasibility of a combined RCM-OCT imaging modality for presurgical evaluation of biopsy-proven BCCs for residual tumor, margin status, and depth. Thirty-eight BCCs in 35 patients referred to a tertiary cancer center for Mohs micrographic surgery (MMS) were imaged with combined RCM-OCT. Images were correlated to MMS frozen sections. Thirty-eight BCCs were analyzed. The mean age of patients was 67.34 years (range, 36-84 years), and 20 patients were female (57.14%). Twenty four BCCs were located on the head (63.16%) , and the mean size was 8.58 mm (range, 3-30 mm). RCM-OCT showed an overall agreement of 91.1% with MMS frozen sections. A sensitivity of 82.6% (95% confidence interval [CI], 69%-92%), specificity of 93.8% (95% CI, 88%-97%), and receiver operating characteristic curve of 0.88 (95% CI, 0.82-0.94) was found. OCT depth was highly correlated with MMS depth (r2 = 0.9). Small sample size and difficulty evaluating certain challenging anatomic sites. Combined RCM-OCT may emerge as a useful tool for presurgical evaluation of BCCs.

Conductive gel bridge sensor for motion tracking in simultaneous EEG-fMRI recordings

EEG-fMRI allows the localization of the hemodynamic correlates of neural activity and has been shown to be useful as a diagnostic tool in pre-surgical evaluation of refractory epilepsy. However, EEG recordings may be highly contaminated by artifacts induced by movements inside the magnetic field thus rendering the scan difficult for interpretation. Existing methods for motion correction require additional equipment or hardware modification. We introduce a simple method for motion artifact detection, the conductive gel bridge sensor (CGBS), easily applicable using the standard setup. We report examples of CGBS use in two patients with epilepsy and demonstrate the method’s ability to successfully differentiate between epochs of brain activity and those of movement.

Integration of resting state functional MRI into clinical practice - A large single institution experience.

Functional magnetic resonance imaging (fMRI) is an important tool for pre-surgical evaluation of eloquent cortex. Classic task-based paradigms require patient participation and individual imaging sequence acquisitions for each functional domain that is being assessed. Resting state fMRI (rs-fMRI), however, enables functional localization without patient participation and can evaluate numerous functional domains with a single imaging session. To date, post-processing of this resting state data has been resource intensive, which limits its widespread application for routine clinical use. Through a novel automated algorithm and advanced imaging IT structure, we report the clinical application and the large-scale integration of rs-fMRI into routine neurosurgical practice. One hundred and ninety one consecutive patients underwent a 3T rs-fMRI, 83 of whom also underwent both motor and language task-based fMRI. Data were processed using a novel, automated, multi-layer perceptron algorithm and integrated into stereotactic navigation using a streamlined IT imaging pipeline. One hundred eighty-five studies were performed for intracranial neoplasm, 14 for refractory epilepsy and 33 for vascular malformations or other neurological disorders. Failure rate of rs-fMRI of 13% was significantly better than that for task-based fMRI (38.5%,) (p <0.001). In conclusion, at Washington University in St. Louis, rs-fMRI has become an integral part of standard imaging for neurosurgical planning. Resting state fMRI can be used in all patients, and due to its lower failure rate than task-based fMRI, it is useful for patients who are unable to cooperate with task-based studies.

Presurgical Evaluation of Impacted Mandibular Third Molar using Digital Fluoroscopy

Background: In order to evaluate the impacted mandibular third molar preparation there are many radiographic techniques used include conventional and digital techniques, the aim of the study is to establish the use of digital fluoroscopy in evaluation of impacted mandibular third molar.Material and Method: - Digital fluoroscopy and conventional bisecting line angle techniques were done for 20 Iraqi adult males 20 -25 years with class one normal occlusion according to angle classification. Measurements were done according to classification system which includes angulations relation to the ramous, depth of impaction, nature of overlying tissue, root morphology, relation to second molar, and its relation to inferior dental canal.Results: It was revealed that there are non significant differences in radiographic assessments of impacted mandibular third molar between digital fluoroscopy and conventional bisecting line angle technique for all classification systems of impacted mandibular third molar at P ≤ 0.01.Conclusion:-The value received from this study showed that digital fluoroscopy could be applied as a diagnostic tool in presurgical evaluation of impacted mandibular third molar.

PET and ictal SPECT can be helpful for localizing epileptic foci.

Purpose of reviewFunctional neuroimaging with PET and SPECT is a commonly used tool in presurgical evaluation. The following article reviews the literature of PET and SPECT in presurgical assessment of epilepsies published in the last year.Recent findingsFDG-PET adds concomitant information in temporal and extratemporal lobe epilepsy in adults and children. The pattern of hypometabolism in FDG-PET is a good additional predictor or seizure outcome in TLE with mesial temporal sclerosis or negative MRI. There is growing evidence that diagnostic value of FDG-PET increases with postprocessing. Although several methods were applied in the reviewed literature, all of them seem to outperform the visual analysis. Imaging of the epileptic focus with ictal SPECT is depending on short injection latencies. It is particularly useful in patients with nonlesional MRI and mostly of extratemporal localization. Areas of hyperperfusion remote of SOZ are reflecting the epileptic network. Combining more concordant investigations including PET and SPECT in MRI-negative evaluation adds to better presurgical stratification and therefore, better postsurgical outcome. FET-PET shows increased uptake in status epilepticus.SummaryPET and SPECT are important investigations to localize the epileptic focus in temporal lobe and nonlesional extratemporal epilepsies. Postprocessing for both modalities is important to increase diagnostic value.

Reproducibility of EEG-MEG fusion source analysis of interictal spikes: Relevance in presurgical evaluation of epilepsy.

Fusion of electroencephalography (EEG) and magnetoencephalography (MEG) data using maximum entropy on the mean method (MEM-fusion) takes advantage of the complementarities between EEG and MEG to improve localization accuracy. Simulation studies demonstrated MEM-fusion to be robust especially in noisy conditions such as single spike source localizations (SSSL). Our objective was to assess the reliability of SSSL using MEM-fusion on clinical data. We proposed to cluster SSSL results to find the most reliable and consistent source map from the reconstructed sources, the so-called consensus map. Thirty-four types of interictal epileptic discharges (IEDs) were analyzed from 26 patients with well-defined epileptogenic focus. SSSLs were performed on EEG, MEG, and fusion data and consensus maps were estimated using hierarchical clustering. Qualitative (spike-to-spike reproducibility rate, SSR) and quantitative (localization error and spatial dispersion) assessments were performed using the epileptogenic focus as clinical reference. Fusion SSSL provided significantly better results than EEG or MEG alone. Fusion found at least one cluster concordant with the clinical reference in all cases. This concordant cluster was always the one involving the highest number of spikes. Fusion yielded highest reproducibility (SSR EEG = 55%, MEG = 71%, fusion = 90%) and lowest localization error. Also, using only few channels from either modality (21EEG+272MEG or 54EEG+25MEG) was sufficient to reach accurate fusion. MEM-fusion with consensus map approach provides an objective way of finding the most reliable and concordant generators of IEDs. We, therefore, suggest the pertinence of SSSL using MEM-fusion as a valuable clinical tool for presurgical evaluation of epilepsy.

P235 Localizing non-epileptic abnormal brain function in children using high density EEG (HDEEG): Electric source imaging (ESI) of focal slowing

Objectives Interictal focal slowing is an important EEG index of brain activity dysfunction, possibly representing an additional tool for presurgical evaluation in pediatric epilepsy. Here, we investigate the accuracy of electric source imaging (ESI) applied to pathological focal EEG slowing (FS) as new neurophysiological index localizing the epileptic focus in children with drug-resistant epilepsy. Method We selected16 children (12 ± 4yrs), who performed hdEEG, presurgical evaluation and underwent surgical resection with at least 1 year of post-operative seizure freedom. For each patient, we exported 15 FS-epochs of 2 s. The S-transform was applied to select the frequency band (delta/theta: 1–4 Hz/4–8 Hz) with maximal power. ESI was performed using a distributed linear inverse solution and an individual head model. The solution point with maximal average power in the band of interest was selected as the source of focal slowing (ESI-FS). Finally, we computed the Euclidian distance between the ESI-FS and the nearest solution point included in the resection with a 5 mm margin. Results In 11/16 (69%), ESI of focal slowing (ESI-FS) was inside the margins of resection. The remaining 5/16 cases had distances 15 mm. Discussion and Conclusions These findings suggest that a “non-epileptiform” activity, such as focal slowing, could help to localize the epileptogenic zone. ESI-FS may aid presurgical lateralization in patients without focal interictal spikes improving the identification of possible good candidate for surgical treatment. Significance The study provides a new quantitative marker of brain dysfunction in children, with a potential application to other neurological disorders, using a non-invasive tool as hdEEG.

Etomidate: A Complementary Diagnostic Tool for Pre-Surgical Evaluation in Temporal Lobe Epilepsy

Context: Temporal lobe epilepsy is the most frequent drug-resistant epilepsy. It has a high success rate in surgical treatment, provided that the epileptic zone (EZ) was accurately localized through a pre-surgical evaluation and removed. Pharmacological activation inducing interictal activity is tested as a complementary method in the pre-surgical diagnosis, although with nonspecific results and limited safety, due to poorly tolerated side effects. Evidence Acquisition: Etomidate is a well-tolerated, fast onset and rapid decline drug with a few side effects. Studies conducted to evaluate the safety and usefulness of etomidate to identify the EZ showed that etomidate activates irritative zone only in the areas where spikes previously appeared in basal conditions, besides having a high coefficient of lateralization for ictal onset zone (IOZ). Regarding the analysis of the topography of the voltage sources, it is shown that interictal, ictal and etomidate-induced activities greatly overlap, indicating that the biophysical mechanisms are similar, and the cortical areas where all types of activities appear are likely the same or closely related. In addition, from the point of view of complex networks, etomidate produces very similar changes in the limbic network to those occurring during temporal seizures i.e. an impaired connectivity in the ipsilateral side to the IOZ. Results: All findings suggest that etomidate, in a specific manner, activates the neural and biophysical mechanisms of spontaneous epilepsy. Conclusions: This technique can be used as a diagnostic tool during the pre-surgical evaluation of patients with TLE to define the region resected during epilepsy surgery with confidence.

EEG-fMRI Co-Registration: From Research to a Potential Pre- Surgical Tool

Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are validated modalities for identifying neuronal activity and they are complementary in that fMRI offers high spatial resolution while EEG provides high temporal resolution. Hence integration of these two modalities would in turn be a promising tool to delineate a focal ictal onset zone, both as part of research and for focal resection of the same zone to abolish drug-resistant seizures This review focuses on this new technique with details of the biophysical difficulties encountered, methodology with relevant EEG-fMRI integration studies in epilepsy research and emphasis on its application as a potential presurgical evaluation tool in evaluation of drug resistant epilepsy.

Validating the effect of muscle artifact suppression in localizing focal epilepsy.

Source localization of an epileptic seizure is becoming an important diagnostic tool in pre-surgical evaluation of epileptic patients. However, for localizing the epileptogenic zone precisely, the epileptic activity needs to be isolated from other activities that are not related to the epileptic source. In this study, we aim at an investigation of the effect of muscle artifact suppression by using a low-pass filter (LPF), independent component analysis (ICA), and a combination of ICA-LPF prior to source localization in focal epilepsy. These techniques were applied on the EEG data obtained from a left-temporal lobe epileptic patient by artificially contaminating the isolated spike interval, present in the four left-temporal electrodes, with a muscle artifact. The results show that the muscle artifact was fully suppressed. Applying the dipole and current-density reconstruction (CDR) source-analysis algorithms on the filtered data, we were able to identify the location of the epileptogenic zone similar to that of the original undistorted data.

Clinical Application of Spatiotemporal Distributed Source Analysis in Presurgical Evaluation of Epilepsy

Magnetoencephalography (MEG), which acquires neuromagnetic fields in the brain, is a useful diagnostic tool in presurgical evaluation of epilepsy. Previous studies have shown that MEG affects the planning intracranial electroencephalography placement and correlates with surgical outcomes by using a single dipole model. Spatiotemporal source analysis using distributed source models is an advanced method for analyzing MEG, and has been recently introduced for analyzing epileptic spikes. It has advantages over the conventional single dipole analysis for obtaining accurate sources and understanding the propagation of epileptic spikes. In this article, we review the source analysis methods, describe the techniques of the distributed source analysis, interpretation of source distribution maps, and discuss the benefits and feasibility of this method in evaluation of epilepsy.

Electroencephalography/functional magnetic resonance imaging responses help predict surgical outcome in focal epilepsy

Simultaneous electroencephalography/functional magnetic resonance imaging (EEG/fMRI) recording can noninvasively map in the whole brain the hemodynamic response following an interictal epileptic discharge. EEG/fMRI is gaining interest as a presurgical evaluation tool. This study aims to determine how hemodynamic responses related to epileptic activity can help predict surgical outcome in patients considered for epilepsy surgery. Thirty-five consecutive patients with focal epilepsy who had significant hemodynamic responses and eventually surgical resection, were studied. The statistical map of hemodynamic responses were generated and co-registered to postoperative anatomic imaging. Patients were classified into four groups defined by the relative relationship between the location of the maximum hemodynamic response and the resection: group 1, fully concordant; group 2, partially concordant; group 3, partially discordant; and group 4, fully discordant. These findings were correlated with surgical outcome with at least 12-month follow-up. Ten patients in group 1 had the maximum t value (t-max) inside the resection; nine in group 2 had the t-max outside but close to the resection and the cluster with t-max overlapped the resection; five in group 3 had the t-max remote from resection, but with another less significant cluster in the resection; and 11 in group 4 had no response in the resection. The degree of concordance correlated largely with surgical outcome: a good surgical outcome (Engel's class I) was found in 7 of 10 patients of group 1, 4 of 9 of group 2, 3 of 5 of group 3, and only 1 of 11 of group 4. These results indicate that the partially concordant and partially discordant groups are best considered as inconclusive. In contrast, in the fully concordant and fully discordant groups, the sensitivity, specificity, positive predictive value, and negative predictive value were high, 87.5%, 76.9%, 70%, and 90.9%, respectively. This study demonstrates that hemodynamic responses related to epileptic activity can help delineate the epileptogenic region. Full concordance between maximum response and surgical resection is indicative of seizure freedom, whereas a resection leaving the maximum response intact is likely to lead to a poor outcome. EEG/fMRI is noninvasive but is limited to patients in whom interictal epileptic discharges can be recorded during the 60-90 min scan.