Resection Of Epileptogenic Zone Research Articles

Improving the accuracy of epileptogenic zone localization in stereo EEG with machine learning algorithms

The precise identification of the epileptogenic zone (EZ) is paramount in the presurgical evaluation of epilepsy patients to ensure successful surgical outcomes. The analysis of Stereo EEG, an instrumental tool for EZ localization, poses considerable challenges even for experienced epileptologists. Consequently, the development of machine learning (ML)-based computational tools for enhanced EZ localization is imperative. In this investigation, we developed ML models utilizing Stereo EEG from 15 patients, who remained seizure-free (Engel 1 a-d) following EZ resection, over an average follow-up period of 44.4 months. Utilizing Delphos and MNI detectors, spikes and High Frequency Oscillations (HFOs) were identified from Stereo EEG in Resected Zone (RZ) and non-Resected Zone (non-RZ). Linear and non-linear features were estimated from each modality using MATLAB. A total of 27,744 spikes, 7,790 ripples, and 7,632 fast ripples, along with their combinations, were employed to train the ML models. The Gradient Boosting classifier demonstrated the highest prediction accuracy of 98.5% for EZ localization in Mesial Temporal Lobe Epilepsy (MTLE) when trained with features derived from the spike-ripple combination. In the case of Neocortical Epilepsy (NE), the Extra Trees classifier achieved an accuracy of 87.6% when utilizing features from fast ripples. The Random Forest, Extra Trees, and Gradient Boosting algorithms were the most effective for predicting the RZ. Linear features outperformed non-linear features in predicting epileptogenic zones within the epileptic brain. Our study establishes the capability of ML methodologies in localizing epileptogenic zones with high accuracy. Future studies that focus on increasing the training sample size and incorporating more advanced machine learning (ML) algorithms have the potential to significantly improve the accuracy of these models in pinpointing epileptogenic networks. Additionally, implementing this ML approach across multiple research centers would contribute to the broader validation and generalizability of this technique.

Posterior Cingulate Epilepsy: A Systematic Review.

In this review, authors discuss epilepsy originating from posterior cingulate regions, a challenging entity to diagnose and most likely underrecognized. A systematic review of posterior middle and posterior cingulate epilepsy cases was conducted to present a summary of current knowledge about this localization-based type of epilepsy. The literature search identified 32 articles, for a total of 69 patients (34 with posterior middle cingulate epilepsy [pMCE] and 35 with posterior cingulate epilepsy [PCE]). Most patients were children and young adults with drug-resistant lesional epilepsy with high seizure burden. In both groups, most patients reported auras, mainly sensory, but various types were reported, including autonomic, behavioral, and cognitive manifestations. Most pMCE and PCE showed motor manifestations (mainly respectively asymmetric tonic posturing and automotor features). Impaired awareness during seizures was more frequently reported in PCE than in pMCE. As for ictal scalp EEG, epileptogenic abnormalities were poorly lateralized and did not localize the seizure onset zone. An ictal temporal involvement was only observed in PCE. Interictal EEG findings were nonspecific. As for other presurgical noninvasive investigations, data are limited, and no studies have adequately assessed their value. Partly explained by our inclusion criteria, most patients underwent a surgical procedure (either lesionectomy or resection of epileptogenic zone as defined by intracranial EEG study results), which overall yielded good outcomes.

MEG abnormalities and mechanisms of surgical failure in neocortical epilepsy.

Epilepsy surgery fails to achieve seizure freedom in 30%-40% of cases. It is not fully understood why some surgeries are unsuccessful. By comparing interictal magnetoencephalography (MEG) band power from patient data to normative maps, which describe healthy spatial and population variability, we identify patient-specific abnormalities relating to surgical failure. We propose three mechanisms contributing to poor surgical outcome: (1) not resecting the epileptogenic abnormalities (mislocalization), (2) failing to remove all epileptogenic abnormalities (partial resection), and (3) insufficiently impacting the overall cortical abnormality. Herein we develop markers of these mechanisms, validating them against patient outcomes. Resting-state MEG recordings were acquired for 70 healthy controls and 32 patients with refractory neocortical epilepsy. Relative band-power spatial maps were computed using source-localized recordings. Patient and region-specific band-power abnormalities were estimated as the maximum absolute z-score across five frequency bands using healthy data as a baseline. Resected regions were identified using postoperative magnetic resonance imaging (MRI). We hypothesized that our mechanistically interpretable markers would discriminate patients with and without postoperative seizure freedom. Our markers discriminated surgical outcome groups (abnormalities not targeted: area under the curve [AUC]=0.80, p=.003; partial resection of epileptogenic zone: AUC=0.68, p=.053; and insufficient cortical abnormality impact: AUC=0.64, p=.096). Furthermore, 95% of those patients who were not seizure-free had markers of surgical failure for at least one of the three proposed mechanisms. In contrast, of those patients without markers for any mechanism, 80% were ultimately seizure-free. The mapping of abnormalities across the brain is important for a wide range of neurological conditions. Here we have demonstrated that interictal MEG band-power mapping has merit for the localization of pathology and improving our mechanistic understanding of epilepsy. Our markers for mechanisms of surgical failure could be used in the future to construct predictive models of surgical outcome, aiding clinical teams during patient pre-surgical evaluations.

The Efficacy, Safety, and Outcomes of Brain-responsive Neurostimulation (RNS® System) therapy in older adults.

ObjectivesThe gold standard for the management of drug‐resistant focal epilepsy (DRE) is resection of epileptogenic zone. However, some patients may not be candidates for resection. Responsive neurostimulation is approved in patients above 18 years of age for such patients. We aimed to investigate whether RNS outcomes and safety varied based on age.MethodsWe performed a single‐center retrospective cohort study of patients with DRE who were treated with RNS between May 2008 and February 2020. We included patients who had been implanted with RNS for >6 months (N = 55), dividing them into older (N = 11) and younger adults (N = 44) depending on implantation age (≥50 and <50 years, respectively).ResultsMean age at implantation in older adults was 54.9 ± 3.5 years. Seizure onset age, epilepsy duration, and comorbidities were significantly higher in older adults ( P < .01). Stimulation parameters, treatment duration, and median seizure frequency reduction (76% in older vs 50% in younger adults) were statistically comparable between the two cohorts. Posttreatment, antiseizure medication burden was significantly decreased in older compared with younger adults (P = .048). Postoperative and delayed adverse events among older adults were mild. Compared with three younger adults, none of the older adults required device explantation due to surgical site infection.ConclusionOur study suggests that older adults treated with the RNS System achieve seizure outcomes comparable to younger adults with the additional benefit of a significant postimplantation medication reduction. With efficacy and safety similar to younger adults, brain‐responsive neurostimulation was well‐tolerated in older adults.

Occult focal cortical dysplasia may predict poor outcome of surgery for drug-resistant mesial temporal lobe epilepsy.

PurposeThe results of surgery in patients with mesial temporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS) are favorable, with a success rate over 70% following resection. An association of HS with focal cortical dysplasia (FCD) in the temporal lobe is one of the potential causes for poor surgical outcome in MTLE. We aimed to analyzed seizure outcome in a population of MTLE patients and recognize the role of occult FCD in achieving postoperative seizure control.MethodsWe retrospectively analyzed postoperative outcomes for 82 consecutive adult patients with the syndrome of MTLE due to HS, who had no concomitant lesions within temporal lobe in MRI and who underwent surgical treatment in the years 2005–2016, and correlated factors associated with seizure relapse.ResultsAt the latest follow-up evaluation after surgery, 59 (72%) were free of disabling seizures (Engel Class I) and 48 (58,5%) had an Engel Class Ia. HS associated with FCD in neocortical structures were noted in 33 patients (40%). Analyzes have shown that dual pathology was the most significant negative predictive factor for Engel class I and Engel class Ia outcome.ConclusionsThe incidence of dual pathology in patients with temporal lobe epilepsy seems to be underestimated. An incomplete epileptogenic zone resection of occult focal temporal dysplasia within temporal lobe is supposed to be the most important negative prognostic factor for seizure freedom after epilepsy surgery in MTLE-HS patients. The study indicates the need to improve diagnostics for other temporal lobe pathologies, despite the typical clinical and radiological picture of MTLE-HS.

Clinicopathologic characteristics and causes of difficulty in locating the "difficult to locate" intractable epilepsy

Objective: To summarize the clinicopathological characteristics of "difficult to locate" intractable epilepsy patients, and investigate the causes of difficulty in their location. Method: Retrospective analysis was performed on the clinical data of 58 patients who underwent resection of the epileptogenic zones after intracranial electroencephalography (iEEG) detection at the Department of Neurosurgery of the First Affiliated Hospital of Fujian Medical University from January 2010 to December 2018. Clinicopathological characteristics and lesion lobes of "difficult to locate" intractable epilepsy were summarized. The prognosis of patients was assessed according to Engel grading.Univariate and multivariate logistic regression analysis were used to investigate the relevant factors affecting the prognosis of patients with "difficult to locate" intractable epilepsy related to malformation of cortical development(MCD). Results: Among the 58 patients, there were 47 cases of MCD (12 cases with mild malformation of cortical development (mMCD), 35 cases with focal cortical dysplasia (FCD)), and 11 cases of other types. Among the 47 MCD cases, univariate analysis showed that patients with preoperative magnetic resonance imaging(MRI) positive and completed resection of the epileptogenic zones had better prognosis (P<0.05). Multivariate analysis indicated that completed resection of epileptogenic zones was an independent factor affecting the postoperative efficacy of MCD (P=0.013,Wald χ(2)=6.149, 95%CI: 0.07-0.56). And among the 47 MCD cases, 18 cases were with mono-lobar lesions and 29 cases were with multi-lobar lesions, however, there was no significant difference of the efficacy between the two groups (P=0.511). Conclusions: MCD, especially FCD, is the main pathological types of patients with "difficult to locate" intractable epilepsy. Multi-lobar pathological changes, especially multi-lobar MCD, are the main reasons of being difficult to locate, however, accurate locating of epileptogenic zones and functional areas via effective use of iEEG can achieve satisfactory efficacy in these patients after resection of the epileptogenic zones.

Intraoperative real-time guidance using ShearWave Elastography for epilepsy surgery

PurposeIn epilepsy surgery, seizure outcome is determined by the integrity of epileptogenic zone resection. ShearWave elastography (SWE) is a noninvasive imaging technique that generates a quantitative assessment of elasticity values permitting intraoperative real time tissue mapping by differentiating normal and pathological epileptogenic tissue. The aim of this study was to evaluate the contribution of SWE intraoperative guidance on the advancement of epileptogenic zone detection in epilepsy surgery. MethodsWe prospectively analyzed epileptogenic zone resections using SWE guidance for 28 patients with severe and/or disabling drug-resistant focal epilepsy. ResultsConventional B-mode images visualized echogenicity differences between the epileptogenic lesion and normal brain tissue in 71.4% of cases, while SWE detected a significant difference in stiffness in 92.8% of cases (p = 0.02). Regarding cryptogenic epilepsy, none of the 4 MRI-negative focal cortical dysplasias was visualized by B-mode images, while 3 cases were detected by SWE. Postoperative brain MRI showed a complete resection of the epileptogenic zone in all MRI-positive cases. One year after the surgery, 85.7% of the patients were seizure free (ILAE class 1). ConclusionDespite some technical limitations, SWE improves the intraoperative detection of epileptogenic lesions and should be considered for all patients with cryptogenic and lesional epilepsy. Naturally this ought to be confirmed by larger case series additionally investigating long-term seizure outcome.

Morphological analysis of brain MRI and its application in focal cortical dysplasia

Objective To investigate the clinical value of MRI morphological analysis in identification of focal cortical dysplasia (FCD) in presurgical evaluation of epileptogenic zone (EZ). Methods We retrospectively analyzed the clinical data of 53 patients who were admitted to Epilepsy Center, Tsinghua University Yuquan Hospital and underwent surgical removal of epileptic foci and were pathologically confirmed as FCD Ⅰ or FCD Ⅱ. Morphometric analysis programme was used to post-process presurgical high-resolution MRI to obtain the gray-white matter junction imaging (MAP+ region) and statistical analysis was used to determine the consistency of the MAP+ region and surgical site and postoperative epilepsy control. Results In this series, the probability of postoperative seizure-free (67.9%, 36/53) was higher in patients whose MAP+ regions were resected than that (7.5%, 4/53) in patients whose MAP+ regions were not resected (P=0.002). In the MRI-negative group, the probability of postoperative seizure-free (62.5%, 20/32) was higher in patients whose MAP+ regions were resected than that (9.4%, 3/32) in patients whose MAP+ regions were not resected (P=0.006). In the MRI positive group, MAP+ regional resection was not associated with the clinical outcome (P=0.352). Conclusions The gray-white matter junction imaging could improve the detection rate of FCD lesions, which might have clinical value in localization of EZ and resection of EZ and making electrode plan of stereotactic electroencephalogram (SEEG). Key words: Epilepsy; Malformations of cortical development; Gray matter and white matter junction imaging; Morphometric analysis programme

Pannexin-1 channels contribute to seizure generation in human epileptic brain tissue and in a mouse model of epilepsy.

Epilepsies are characterized by recurrent seizures, which disrupt normal brain function. Alterations in neuronal excitability and excitation-inhibition balance have been shown to promote seizure generation, yet molecular determinants of such alterations remain to be identified. Pannexin channels are nonselective, large-pore channels mediating extracellular exchange of neuroactive molecules. Recent data suggest that these channels are activated under pathological conditions and regulate neuronal excitability. However, whether pannexin channels sustain or counteract chronic epilepsy in human patients remains unknown. We studied the impact of pannexin-1 channel activation in postoperative human tissue samples from patients with epilepsy displaying epileptic activity ex vivo. These samples were obtained from surgical resection of epileptogenic zones in patients suffering from lesional or drug-resistant epilepsy. We found that pannexin-1 channel activation promoted seizure generation and maintenance through adenosine triphosphate signaling via purinergic 2 receptors. Pharmacological inhibition of pannexin-1 channels with probenecid or mefloquine-two medications currently used for treating gout and malaria, respectively-blocked ictal discharges in human cortical brain tissue slices. Genetic deletion of pannexin-1 channels in mice had anticonvulsant effects when the mice were exposed to kainic acid, a model of temporal lobe epilepsy. Our data suggest a proepileptic role of pannexin-1 channels in chronic epilepsy in human patients and that pannexin-1 channel inhibition might represent an alternative therapeutic strategy for treating lesional and drug-resistant epilepsies.

S173. Automatic detection of high frequency oscillations (HFOs) to locate epileptogenic zone

Introduction Surgical resection of epileptogenic zone is the first choice for the treatment of refractory epilepsy, and accurate localization of epileptogenic zone is the key to determine the outcome of the operation. In recent years, There are many research show that high-frequency oscillations (HFOs) is a promising biomarker for the epileptogenic zone. Visual HFOs evaluation is subjectivity and time-consuming. It seriously limits the application of the HFOs in clinic. Therefore, it is very important to develop high frequency oscillation automatic detection program to precisely locate the epileptogenic zone for improving the curative effect of epilepsy surgery. Methods We retrospectively studied EEG data from 20 patients at Xuanwu hospital, Capital Medical University in who underwent epilepsy surgery (from January 2017 to March 2017). Inclusion criterion: 1. Patients with complete medical records and underwent surgery resection. 2. Implanted subdural grids, depth electrode or stereotactic deep electrode (for SEEG). 3. Sampling rate > 2000 Hz. 4. For more than half a year’s follow-up. Exclusion criterion: 1. EEG data with obvious artifacts. 2. Patients with bilateral lesions. 3. Patients with occipital lobe epilepsy. Inclusion criterion of channels: HFOs rate > 1/min (the number of highest HFOs channels is less than 10/min, then all channels are analyzed). All patients signed informed consent and the project was approved by the Ethics Committee of Xuanwu hospital, Capital Medical University. We applied the automatic detection program based on maximum distribution peak point calculating the baseline which developed by our laboratory to perform HFOs analysis for all of patients. After that, we sort the channels from high to low according to the number of HFOs, then the resection ratio was calculated used the total number of channels which from the highest frequency channels to the first channel without resected divided the total number of produced HFOs channel. Finally, the resection rate was compared with the prognosis of the patients. Results Patients are in two groups based on Engel Classification. thirteen patients in good outcome which means Engel Ia (seizure free), and seven patients in poor outcome which means Engel Ib-IV (non-seizure free). In good outcome patients’ group, the resection ratio of ripples is 24% and fast ripple is 82% (the lowest ratio is 40%). In poor outcome patients’ group, the resection ratio of ripples is 6% and fast ripples is 12% (the highest ratio is 21.4%). We found that resection ratio of fast ripple has obvious statistical significance (P Conclusion Our results show that patients who remove higher ratio channels of the Fast ripple would have better surgical outcome, therefore, fast ripple is more accurate than ripple in localizing epileptogenic zone.

Frameless robot-assisted stereoelectroencephalography in children: technical aspects and comparison with Talairach frame technique.

OBJECTIVE Robot-assisted stereoelectroencephalography (SEEG) is gaining popularity as a technique for localization of the epileptogenic zone (EZ) in children with pharmacoresistant epilepsy. Here, the authors describe their frameless robot-assisted SEEG technique and report preliminary outcomes and relative complications in children as compared to results with the Talairach frame-based SEEG technique. METHODS The authors retrospectively analyzed the results of 19 robot-assisted SEEG electrode implantations in 17 consecutive children (age < 17 years) with pharmacoresistant epilepsy, and compared these results to 19 preceding SEEG electrode implantations in 18 children who underwent the traditional Talairach frame-based SEEG electrode implantation. The primary end points were seizure-freedom rates, operating time, and complication rates. RESULTS Seventeen children (age < 17 years) underwent a total of 19 robot-assisted SEEG electrode implantations. In total, 265 electrodes were implanted. Twelve children went on to have EZ resection: 4 demonstrated Engel class I outcomes, whereas 2 had Engel class II outcomes, and 6 had Engel class III-IV outcomes. Of the 5 patients who did not have resection, 2 underwent thermocoagulation. One child reported transient paresthesia associated with 2 small subdural hematomas, and 3 other children had minor asymptomatic intracranial hemorrhages. There were no differences in complication rates, rates of resective epilepsy surgery, or seizure freedom rates between this cohort and the preceding 18 children who underwent Talairach frame-based SEEG. The frameless robot-assisted technique was associated with shorter operating time (p < 0.05). CONCLUSIONS Frameless robot-assisted SEEG is a safe and effective means of identifying the EZ in children with pharmacoresistant partial epilepsy. Robot-assisted SEEG is faster than the Talairach frame-based method, and has equivalent safety and efficacy. The former, furthermore, facilitates more electrode trajectory possibilities, which may improve the localization of epileptic networks.

A study of the timing of epileptogenic zonectomy following stereotactic intracranial electrode implantation

Objective To explore the correlation between cranial infection and the timing of epileptogenic zonectomy following intracranial electrode implantation assisted by robotized stereotactic assistant (ROSA). Methods The clinical data of 132 epilepsy patients admitted to Beijing Sanbo Brain Hospital from March 2012 to December 2015 who underwent implantation of intracranial electrodes assisted by ROSA and resection of epileptogenic zones, including 5 cases undergoing epileptogenic zonectomy combined with bipolar electro-coagulation on functional cortex (BCFC), were collected and retrospectively analyzed. Results Sixteen patients (12.1%) underwent surgical resection on the day of electrode removal; 10 patients (7.6%) received surgical resection within 1 week post intracranial electrode removal; 33 patients(25%)underwent surgical resection from 1 week to 1 month following intracranial electrodes removal; 27 patients (20.5%) experienced surgical resection from 1 to 3 months post electrode removal; and the remaining 46 patients (34.8%) underwent epileptogenic zonectomy 3 months post electrode removal. Postoperative intracranial infection was noted in 4 patients (3.0%), who underwent surgical resection 16, 65, 109 and 120 days after electrode removal, respectively. The infection was subsequently cured in all cases with conservative therapy. There was no statistical difference in the infection rate between groups varying in timing of epileptogenic zonectomy (P=0.839). Conclusion There seems to be no statistical correlation between cranial infection and the timing of epileptogenic zone resection following intracranial electrode removal. Key words: Epilepsy; Neurosurgical procedure; Time management; Infection; Robotized stereotactic assistant

Correlation between resection of high frequency oscillation region and outcomes of epilepsy surgery

Objective To explore the relationship between removal of areas where high frequency oscillations (HFOs) were detected by a new automatic detector and the prognosis of epilepsy surgical. Methods In this study, 7 patients with intractable epilepsy were enrolled and their clinical data were retrospectively studied, who underwent intracranial electroencephalography (EEG) monitoring and subsequent epileptogenic zone resection from January 2013 and December 2014 at Epilepsy Center of Beijing Haidian Hospital. An automatic detector of HFOs was employed using maximum distributed peak points to calculate baseline. Then the relationship between the removal ratio of HFOs and surgical outcomes was investigated. Results Among the 7 cases of refractory epilepsy, the resection ratio of ripple area was 19.4% ~ 96.4% and that of fast ripple area was 29.3% ~ 96.0% . The surgical removal ratio of HFO areas was higher than 50% in 5 cases, 4 out of whom achieved good outcomes after surgery. In the other 2 patients whose removal ratio of HFO area was lower than 50%, poor surgical outcome was reported in 1 and good outcome was obtained in the other who had extensive area demonstrating suspicious physiological HFOs in the occipital lobe. Conclusions The automatic detector of HFOs using maximum distributed peak points to calculate baseline seems to be accurate for detection of HFOs. The ratio of resection in areas with HFOs might be closely related to the surgical outcomes. Key words: Epilepsy; Neurosurgical procedures; Maximum distributed peak points; High frequency oscillations; Prognosis

Epileptic Zone Resection for Magnetic Resonance Imaging-Negative Refractory Epilepsy Originating from the Primary Motor Cortex.

Because of the balance between achieving complete seizure freedom and minimizing the postoperative neurologic deficits, surgery for refractory epilepsy originating from the primary motor cortex is difficult. Here, we report the outcomes of surgery for magnetic resonance imaging-negative refractory epilepsy originating from the primary motor cortex in a case series. Nine patients with refractory epilepsy originating from the primary motor cortex underwent intracranial electrodes implantation after preoperative evaluation. Subdural grid electrodes and depth electrodes were implanted through craniotomy assisted by stereotactic technique. We delineated the epileptic zone and executed tailored resection according to results of intracranial electroencephalography and mapping. The patients were followed up for at least 1 year. Muscle strength was evaluated at different postoperative times (day 1, 2 weeks, and 1 year). Regarding seizure outcome at the last follow-up, Engel class I outcome was achieved in 5 patients, class II was achieved in 3 patients, and class III was achieved in 1 patient. All cases had postoperative hemiparesis of different degree on the first day after operation. Three patients experienced distal muscle strength of single limb with grade 3 or lower and had obvious dysfunction at 1 year after operation. Six patients experienced distal muscle strength of grade 4 or 5 (Medical Research Council 6-point scale) and had no obvious dysfunction at that time. Most patients of refractory epilepsy originating from the primary motor cortex were seizure freeand had no obvious neurologic deficits at follow-up. Epileptogenic zone resection may not always be contraindicated for patients with nonlesional refractory epilepsy originating from the primary motor cortex.

An Intracranial Electroencephalography (iEEG) Brain Function Mapping Tool with an Application to Epilepsy Surgery Evaluation.

Objects: Before epilepsy surgeries, intracranial electroencephalography (iEEG) is often employed in function mapping and epileptogenic foci localization. Although the implanted electrodes provide crucial information for epileptogenic zone resection, a convenient clinical tool for electrode position registration and Brain Function Mapping (BFM) visualization is still lacking. In this study, we developed a BFM Tool, which facilitates electrode position registration and BFM visualization, with an application to epilepsy surgeries.Methods: The BFM Tool mainly utilizes electrode location registration and function mapping based on pre-defined brain models from other software. In addition, the electrode node and mapping properties, such as the node size/color, edge color/thickness, mapping method, can be adjusted easily using the setting panel. Moreover, users may manually import/export location and connectivity data to generate figures for further application. The role of this software is demonstrated by a clinical study of language area localization.Results: The BFM Tool helps clinical doctors and researchers visualize implanted electrodes and brain functions in an easy, quick and flexible manner.Conclusions: Our tool provides convenient electrode registration, easy brain function visualization, and has good performance. It is clinical-oriented and is easy to deploy and use. The BFM tool is suitable for epilepsy and other clinical iEEG applications.

Application of stereoelectroencephalography in preoperative assessment of patients with drug-refractory epilepsy

Objective To investigate the application value of stereoelectroencephalography (SEEG) in the preoperative assessment of epilepsy surgery. Methods The clinical data of 78 patients with drug-refractory epilepsy assessed with SEEG before procedure at the Epilepsy Center, Guangdong 999 Brain Hospital from April 2014 to April 2015 were analyzed retrospectively. The noninvasive assessment was conducted first, and the SEEG electrode placement scheme was designed according to the clinical and imaging data, and then under the guidance of robotized stereotactic assistant (ROSA), the electrode implantation was completed. The SEEG monitoring was conducted in order to complete the resection of epileptogenic zone finally under the guidance of neuronavigation. Results Seventy-eight patients completed 81 SEEG electrode implantations (3 patients had additional electrode implantations), including 16 (20.5%) bilateral implantations. A total of 940 SEEG electrodes were implanted and the average number of implanted electrodes was 12.3 per case. Only 1 patient had an epidural hematoma in the electrode region, and other patients did not have the complications, such as serious hemorrhage, infection, cerebrospinal fluid leakage, electrode fraction or displacement. Seventy-six patients successfully completed the resection of epileptogenic zone, and 2 patients failed to undergo surgery. Fifty-nine patients were followed up for 6-18 months. The seizure control for Engel rating grades were grade Ⅰ in 47 cases (79.7%), grade Ⅱ in 2 cases (3.4%), grade Ⅲ in 6 cases (10.2%), and grade Ⅳ in 4 cases (6.8%). In 51 patients with MRI positive, the Engel grade Ⅰ was in 42 cases (82.4%); in 8 patients with MRI negative, the Engel grade Ⅰ was in 5 cases. There was no significant difference in the seizure control rate between the 2 groups (P>0.05). Conclusion The surgical treatment of epilepsy under the guidance of SEEG is both safe and effective. Key words: Epilepsy; Electroencephalography; Stereoelectroencephalography; Robotized stereotactic assistant; Multimodel images

Temporal lobe epilepsy and cavernous malformations: surgical strategies and long-term outcomes.

Cerebral cavernous malformations (CCM) of the temporal lobe often present with seizures. Surgical resection of these lesions can offer durable seizure control. There is, however, no universally accepted methodology for assessing and surgically treating these patients. We propose an algorithm to maximize positive surgical outcomes (seizure control) while minimizing post-surgical neurological deficit. A retrospective review of 34 patients who underwent epilepsy surgery for radiographically proven temporal lobe CCM was conducted. Patients underwent a relatively standard work-up for seizure localization. In patients with mesial temporal lobe epilepsy (MTLE), a complete resection of the epileptogenic zone was performed including amygdalo-hippocampectomy in addition to a lesionectomy if not contraindicated by pre-operative work-up. Patients with neocortical epilepsy underwent intraoperative electrocorticography (ECoG)-guided lesionectomy. Seizure-free rate for mesial and neocortical (anterior, lateral, and basal) location was 90 vs. 83 %, respectively. Complete resection of the lesion, irrespective of location, was statistically significant for seizure control (p = 0.018). There was no difference in seizure control based on disease duration or location (p > 0.05). Patients with mesial temporal CCM who presented with MTLE were presumed to also have mesial temporal sclerosis (MTS), or dual pathology. These patients underwent routine resection of the mesial structures. Interestingly, patients who had MTLE and basal (neocortical) lesions who underwent a mesial resection for suspected MTS were found not to have dual pathology. Patients with temporal lobe CCM should be offered resection for durable seizure control, prevention of secondary epileptogenic foci, and elimination of hemorrhage risk. The preoperative work-up should follow a team approach. Surgical intervention should include complete lesionectomy in all cases. Intra or extra-operative ECoG for neocortical lesions may be beneficial. Management of mesial temporal CCMs (archicortex) should consider resection of a well-defined epileptogenic zone (including mesial structures) due to high probability of pathologically proven MTS. The use of this treatment algorithm is useful for the education and treatment of these patients.

Treatment and outcome of epileptogenic temporal cavernous malformations.

Background:The aim of this study is to explore the treatment and outcome of epileptogenic temporal lobe cavernous malformations (CMs).Methods:We analyzed retrospectively the profiles of 52 patients diagnosed as temporal lobe CMs associated with epilepsy. Among the 52 cases, 11 underwent a direct resection of CM along with the adjacent zone of hemosiderin rim without electrocorticogram (ECoG) monitoring while the other 41 cases had operations under the guidance of ECoG. Forty-six patients were treated by lesionectomy + hemosiderin rim while the other six were treated by lesionectomy + hemosiderin rim along with extended epileptogenic zone resection. The locations of lesions, the duration of illness, the manifestation, the excision ranges and the outcomes of postoperative follow-up were analyzed, respectively.Results:All of the 52 patients were treated by microsurgery. There was no neurological deficit through the long-term follow-up. Outcomes of seizure control are as follows: 42 patients (80.8%) belong to Engel Class I, 5 patients (9.6%) belong to Engel Class II, 3 patients (5.8%) belong to Engel Class III and 2 patients (3.8%) belong to Engel Class IV.Conclusion:Patients with epilepsy caused by temporal CMs should be treated as early as possible. Resection of the lesion and the surrounding hemosiderin zone is necessary. Moreover, an extended excision of epileptogenic cortex or cerebral lobes is needed to achieve a better prognosis if the ECoG indicates the existence of an extra epilepsy onset origin outside the lesion itself.

The stereotactic approach for mapping epileptic networks: a prospective study of 200 patients.

Stereoelectroencephalography (SEEG) is a methodology that permits accurate 3D in vivo electroclinical recordings of epileptiform activity. Among other general indications for invasive intracranial electroencephalography (EEG) monitoring, its advantages include access to deep cortical structures, its ability to localize the epileptogenic zone when subdural grids have failed to do so, and its utility in the context of possible multifocal seizure onsets with the need for bihemispheric explorations. In this context, the authors present a brief historical overview of the technique and report on their experience with 2 SEEG techniques (conventional Leksell frame-based stereotaxy and frameless stereotaxy under robotic guidance) for the purpose of invasively monitoring difficult-to-localize refractory focal epilepsy. Over a period of 4 years, the authors prospectively identified 200 patients with refractory epilepsy who collectively underwent 2663 tailored SEEG electrode implantations for invasive intracranial EEG monitoring and extraoperative mapping. The first 122 patients underwent conventional Leksell frame-based SEEG electrode placement; the remaining 78 patients underwent frameless stereotaxy under robotic guidance, following acquisition of a stereotactic ROSA robotic device at the authors' institution. Electrodes were placed according to a preimplantation hypothesis of the presumed epileptogenic zone, based on a standardized preoperative workup including video-EEG monitoring, MRI, PET, ictal SPECT, and neuropsychological assessment. Demographic features, seizure semiology, number and location of implanted SEEG electrodes, and location of the epileptogenic zone were recorded and analyzed for all patients. For patients undergoing subsequent craniotomy for resection, the type of resection and procedure-related complications were prospectively recorded. These results were analyzed and correlated with pathological diagnosis and postoperative seizure outcomes. The epileptogenic zone was confirmed by SEEG in 154 patients (77%), of which 134 (87%) underwent subsequent craniotomy for epileptogenic zone resection. Within this cohort, 90 patients had a minimum follow-up of at least 12 months; therein, 61 patients (67.8%) remained seizure free, with an average follow-up period of 2.4 years. The most common pathological diagnosis was focal cortical dysplasia Type I (55 patients, 61.1%). Per electrode, the surgical complications included wound infection (0.08%), hemorrhagic complications (0.08%), and a transient neurological deficit (0.04%) in a total of 5 patients (2.5%). One patient (0.5%) ultimately died due to intracerebral hematoma directly ensuing from SEEG electrode placement. Based on these results, SEEG methodology is safe, reliable, and effective. It is associated with minimal morbidity and mortality, and serves as a practical, minimally invasive approach to extraoperative localization of the epileptogenic zone in patients with refractory epilepsy.

Surgical outcome and prognostic factors in focal cortical dysplasia with intractable epilepsy

To analyze surgical outcome and relevant surgical parameters including resection extent of epileptogenic zone,pathological subtype, brain MRS and MRI results in FCD with intractable epilepsy. We retrospectively analyzed surgical outcomes of 35 patients with intractable epilepsy related to focal cortical dysplasia, accepted surgery in the first affiliated hospital of Fujian Medical University from January 2008 to January 2010, with 12-36 months of postoperative follow-up. The relevance between complete resection, pathological subtype, MRS and MRI result and surgical outcome were statistically evaluated. 22 patients (66.7%) were Engel class I, 5 patients (14.3%) were class II, 6 patients (17.2%) were class III, 2 patients (5.8%) were class IV. Complete resection of epileptogenic zone (P < 0.05), FCD type I (P < 0.05) correlated significantly with favorable surgical outcome. Other factors such as MRI results, abnormal NAA/CHO + Cr ratio on the contralateral side of epileptogenic zone, as well as MRS-accurate lateralization did not influence outcome. Overall, the surgical outcome of FCD is favorable. Complete resection, FCD type I correlates significantly with favorable surgical outcome.