Resective reoperation for failed epilepsy surgery: Seizure outcome in 64 patients

The clinical application of neuro-robot in the resection of epileptic foci: a novel method assisting epilepsy surgery

During surgery for foci-related epilepsy, neurosurgeons face significant difficulties in identifying and resecting MRI-negative or deep-seated epileptic foci. Here, we present a neuro-robotic navigation system that is specifically designed for resection of MRI negative epileptic foci. We recruited 52 epileptic patients, and randomly assigned them to treatment group with either neuro-robotic navigation or conventional neuronavigation system. For each patient, in the neuro-robotic navigation group, we integrated multimodality imaging including MRI and PET-CT into the robotic workstation and marked the boundary of foci from the fused image. During surgery, this boundary was delineated by the robotic laser device with high accuracy, guiding resection for the surgeon. For deeply seated foci, we exploited the neuro-robotic navigation system to localize the deepest point with biopsy needle insertion and methylene dye application to locate the boundary of the foci. Our results show that, compared with the conventional neuronavigation, the neuro-robotic navigation system performs equally well in MRI positive epilepsy patients (ENGEL I ratio: 71.4% vs 100%, p = 0.255) systems and show better performance in patients with MRI-negative focal cortical dysplasia (ENGEL I ratio: 88.2% vs 50%, p = 0.0439). At present, there are no documented neurosurgery robots with similar function and application in the field of epilepsy. Our research highlights the added value of using neuro-robotic navigation systems in resection surgery for epilepsy, particularly in cases that involve MRI-negative or deep-seated epileptic foci.

Transuncal Selective Amygdalohippocampectomy by an Inferolateral Preseptal Endoscopic Approach Through Inferior Eyelid Conjunctival Incision: An Anatomic Study

BACKGROUND

Transorbital endoscopic approaches have been described for pathologies of anterior and middle fossae. Standard lateral orbitotomy gives access to mesial temporal lobe, but the axis of work is partially obscured by the temporal pole and working corridor is limited.

OBJECTIVE

To evaluate the usefulness of an inferolateral orbitotomy to provide a more direct corridor to perform a transuncal selective amygdalohippocampectomy.

METHODS

Three adult cadaveric specimens were used for a total of 6 dissections. A step-by-step description and illustration of the transuncal corridor for a selective amygdalohippocampectomy were performed using the inferolateral orbitotomy through an inferior eyelid conjunctival incision. The anatomic landmarks were demonstrated in detail. Orbitotomies and angles of work were measured from computed tomography scans, and the area of resection was illustrated by postdissection MRI.

RESULTS

Inferior eyelid conjunctival incision was made for exposure of the inferior orbital rim. Inferolateral transorbital approach was performed to access the transuncal corridor. Endoscopic selective amygdalohippocampectomy was performed through the entorhinal cortex without damage to the temporal neocortex or Meyer's loop. The mean horizontal diameter of the osteotomy was 14.4 mm, and the vertical one was 13.6 mm. The mean angles of work were 65° and 35.5° in the axial and sagittal planes, respectively. Complete amygdalohippocampectomy was achieved in all 6 dissections.

CONCLUSION

Transuncal selective amygdalohippocampectomy was feasible in cadaveric specimens using the inferolateral transorbital endoscopic approach avoiding damage to the temporal neocortex and Meyer's loop. The inferior eyelid conjunctival incision may result in an excellent cosmetic outcome.

Seizure onset zone classification based on imbalanced iEEG with data augmentation

Objective. Identifying the seizure onset zone (SOZ) in patients with focal epilepsy is the critical information required for surgery. However, collecting this information is challenging, time-consuming, and subjective. Some machine learning methods reduce the workload of clinical experts in intracranial electroencephalogram (iEEG) visual diagnosis but face significant challenges because interictal iEEG clinical data often suffer from a significant class imbalance. We aim to generate synthetic data for the minority class.Approach. To make the clinically imbalanced data suitable for machine learning, we introduce an EEG augmentation method (EEGAug). The EEGAug method randomly selects several samples from the minority class and transforms them into the frequency domain. Then, different frequency bands from different samples are used to compose new data. Finally, a synthetic sample is generated after converting the new data back to the time domain.Main results. The imbalanced clinical iEEG data can be balanced and applied to machine learning models using the method. A one-dimensional convolutional neural network model is used to classify the SOZ and non-SOZ data. We compare the EEGAug method with other data augmentation methods and another method of class-balanced focal loss function, which is also used for solving the data imbalance problem by adjusting the weights between the minority and majority classes. The results show that the EEGAug method performs best in most data.Significance. Data imbalance is a widespread clinical problem. The EEGAug method can flexibly generate synthetic data for the minority class, yielding synthetic and raw data with a high distribution similarity. By using the EEGAug method, clinical data can be used in machine learning models.

Predictors of longitudinal seizure outcomes after epilepsy surgery in childhood

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Long term seizure outcome in children following epilepsy surgery is favorable.

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Histopathology is an independent determinant of long-term seizure outcome.

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Long-term seizure outcome remains stable in children with tumours and FCD type 2b, whereas seizure freedom declines with time in children with other types of FCD and cortical malformations.

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Children with moderate to severe developmental disability and younger age of seizure onset have higher seizure recurrence reflecting broader epileptic networks.

There is a paucity of data on longitudinal seizure outcome of children undergoing epilepsy surgery. All children (n = 132) who underwent resective epilepsy surgery from January 1998 to December 2015 were identified. Relevant clinical, neurophysiological, imaging, surgical and seizure outcome data were extracted. Multivariable logistic regression analysis and Kaplan-Meier survival with Cox proportional hazard modelling were performed. The mean age at surgery was 7.8 years (range 0.2–17.9). 71% were seizure-free at a mean follow up of 5.3 ± 2.7 years. Of those who were seizure-free, 65 patients were able to completely wean off anti- seizure medications successfully. Using survival analysis, the probability of Engel Class I outcome at one year after surgery was 81% (95% confidence interval [CI] 87%–75%). This dropped to 73% at two years (95% CI 81%–65%), 58% at five years (95% CI 67.8%–48%), and 47% at ten years. Proportional hazard modelling showed that the presence of moderate to severe developmental disability (HR 6.5; p = 0.02) and lack of complete resection (HR 0.4; p = 0.02) maintain association as negative predictors of seizure-free outcome. Our study demonstrates favorable long-term seizure control following pediatric epilepsy surgery and highlights important predictors of seizure outcome guiding case selection and counseling of expectations prior to surgery.

Predictors of Seizure Outcome after Repeat Pediatric Epilepsy Surgery: Reasons for Failure, Sex, Electrophysiology, and Temporal Lobe Surgery

Considering that seizure freedom is one of the most important goals in the treatment of epilepsy, repeat epilepsy surgery could be considered for patients who continue to experience drug-resistant seizures after epilepsy surgery. However, the chance of seizure freedom is reported to be below 50% after reoperation for failed epilepsy surgery. This study aimed to elucidate the predictive factors for seizure outcomes after repeat pediatric epilepsy surgery. In all, 39 pediatric patients who underwent repeat curative epilepsy surgery between 2008 and 2020 at our institution were retrospectively studied. The relationship between preoperative clinical factors and postoperative seizure freedom at the last follow-up was statistically evaluated. The mean age at the first surgery was 5.5 years (0-16). The etiology of epilepsy was malformation of cortical development in 33 patients. The average time to seizure recurrence after the first surgery was 6.4 months (range, 0-26 months). In all, 16 patients (41.0%) achieved seizure freedom after the second surgery. Seven patients underwent a third surgery, and three (42.9%) achieved seizure freedom. Overall, 19 patients achieved seizure freedom after repeat epilepsy surgery (48.7%). Female sex, surgical failure due to technical limitations, congruent electroencephalography (EEG) findings, lesional magnetic resonance imaging (MRI) and Rt-sided surgery were predictive of seizure freedom, and surgery limited to the temporal lobe was predictive of residual seizures, as determined in the multivariate analysis. The reoperation of failed epilepsy surgery is challenging. Consideration of the above predictive factors can be helpful in deciding whether to reoperate on pediatric patients whose initial surgical intervention failed.

Resective epilepsy surgery in patients aged 50years and older - a retrospective study regarding seizure outcome, memory performance, and psychopathology

PURPOSE

To assess clinical and demographic characteristics in two cohorts of elderly patients with drug-resistant focal epilepsy, undergoing resective epilepsy surgery (RES). Further, to determine seizure, neuropsychological, and mental health outcomes after RES and evaluate possible influencing factors.

METHODS

Consecutive patients aged ≥50 years with temporal lobe epilepsy (TLE) who underwent curative RES in the Hamburg epilepsy surgery program (2004-2017) were identified. Data were retrospectively analyzed. Seizure outcome was classified according to ILAE and Engel outcome scales in patients with first-time surgeries and with reoperations. Previously reported predictors of the seizure outcome were evaluated using regression analyses. Changes in verbal memory were assessed for patients with complete pre- and postoperative datasets (n=30) using repeated-measures analysis of variance. For evaluation of possible predictors of psychopathologic changes after RES a regression analysis was conducted.

RESULTS

Fifty-one elderly patients underwent RES of the temporal lobe, including twelve aged ≥60 years, and five with reoperations. After one year, 65% of the patients with first-time surgeries were seizure free and 91% had a favorable outcome. At last follow-up, 49% were seizure free since surgery. Three reoperated patients had an Engel I outcome. Seizure outcome was not dependent on age at surgery, duration of epilepsy, or other evaluated variables. There was no significant decline in the memory performance after surgery. Significant improvements in mental health were found.

CONCLUSION

RES for drug-resistant TLE is safe, effective, and improves mental health also in patients aged ≥ 50 years. Thus, it should be evaluated as the treatment of choice also in this age group.

[Redo surgery in children with epilepsy]

OBJECTIVE

To analyze the causes of ineffective operations and the results of redo surgery in children with recurrent epileptic seizures.

MATERIAL AND METHODS

The results of redo surgery were analyzed in 41 (10.6%) out of 387 children with drug resistant epilepsy treated surgically at the Russian Polenov Neurosurgical Institute for the period from 1994 to 2014. Patients with recurrent epilepsy after temporal resection (n=20), extratemporal resection (n=7), multifocal resection (n=6), callosotomy and stereotaxic destruction (n=8) were selected for analysis.

RESULTS

Seizure-free period ranged from early postoperative period to 4 years. According to MRI data, lesions were not completely resected during primary surgery in 23 (56.1%) children. The causes of inefficiency of primary operations were inaccurate identification of epileptic focus in 15 (36.6%) patients; incomplete resection of epileptogenic and / or epileptic foci or incomplete disconnection of paroxysmal activity distribution pathways in 14 (34.1%) cases; epileptic foci de novo in 8 (19.5%) cases; inadequate surgical strategy in 4 (9.8%) patients. Redo surgery usually implied an extended previous resection in 34 (82.9%) patients. Engel I outcome after 3 years was achieved in 41.1% of patients, after 5 years - 38.3%, after 10 years - 36.4%.

CONCLUSION

Redo surgery is quite effective and minimally traumatic. Therefore, patients with recurrent epileptic seizures should be considered as candidates for repeated operations if previous interventions turned out to be ineffective.

Long-term outcomes of reoperations in epilepsy surgery

OBJECTIVE

To analyze longitudinal seizure outcomes following epilepsy surgery, including reoperations, in patients with intractable focal epilepsy.

METHODS

Clinicoradiological characteristics of patients who underwent epilepsy surgery from 1995 to 2016 with follow-up of ≥1 year were reviewed. In patients undergoing reoperations, the latest resection was considered the index surgery. The primary outcome was complete seizure freedom (Engel I) at last follow-up. Potentially significant outcome variables were first identified using univariate analyses and then fit in multivariate Cox proportional hazards models.

RESULTS

Of 898 patients fulfilling study criteria, 110 had reoperations; 92 had one resection prior to the index surgery and 18 patients had two or more prior resective surgeries. Two years after the index surgery, 69% of patients with no prior surgeries had an Engel score of I, as opposed to only 42% of those with one prior surgery, and 33% of those with two or more prior resections (P < .001). Among surgical outcome predictors, the number of prior epilepsy surgeries, female sex, lesional initial magnetic resonance imaging, no prior history of generalization, and pathology correlated with better seizure outcomes on univariate analysis. However, only sex (P = .011), history of generalization (P = .016), and number of prior surgeries (P = .002) remained statistically significant in the multivariate model.

SIGNIFICANCE

Although long-term seizure control is possible in patients with failed prior epilepsy surgery, the chances of success diminish with every subsequent resection. Outcome is additionally determined by inherent biological markers (sex and secondary generalization tendency), rather than traditional outcome predictors, supporting a hypothesis of "surgical refractoriness."

Measure thrice, cut twice: On the benefit of reoperation for failed pediatric epilepsy surgery

OBJECTIVE

To determine whether clinical outcomes are improved after repeat surgery for medically refractory epilepsy in children.

METHODS

This is a single-center retrospective cohort analysis of all patients who received repeat resective surgery for ongoing seizures from 2000-2017. From a total of 251 consecutive individual epilepsy surgical patients for focal resection, 53 patients met study inclusion criteria and had adequate follow-up documented.

RESULTS

Median age of seizure-onset was 2.0-years-old (IQR 0.3-5.5 years). The median age at first epilepsy surgery was 6.3-years-old (IQR 2.9-9.2 years) and at second epilepsy surgery was 8.4-years-old (IQR 4.7-12.6 years). Overall, 53 % (n = 28) of this series achieved Engel Class I (seizure freedom); with improved seizure control (Engel Class I-II) in 83 % (n = 44) of the cohort. 64 % (n = 34) had one reoperation; 26 % (n = 14) had two; and 9% (n = 5) had three. Pathology: 58 % (n = 31) had focal cortical dysplasia; 13 % (n = 10) tumor; 9% (n = 5) encephalitis; 6% (n = 3) gliosis; 4% (n = 2) mesial temporal sclerosis; and 2% (n = 1) hemimegalencephaly. Tumor pathology was associated with increased chance (p = 0.01) for seizure freedom (90 % of tumor patients had Engel Class I outcome). MTS had worse outcome with both patients having ongoing seizures (Engel II-IV). There were 6 patients who developed post-operative hemiparesis; one was unplanned but resolved.

SIGNIFICANCE

Reoperation for pediatric epilepsy surgery can lead to seizure freedom in many cases and improved seizure control in most cases. Reoperation for brain tumor pathology is associated with a high rate of seizure freedom.

Rates and predictors of success and failure in repeat epilepsy surgery: A meta-analysis and systematic review

OBJECTIVE

Medically refractory epilepsy is a debilitating disorder that is particularly challenging to treat in patients who have already failed a surgical resection. Evidence regarding outcomes of further epilepsy surgery is limited to small case series and reviews. Therefore, our group performed the first quantitative meta-analysis of the literature from the past 30 years to assess for rates and predictors of successful reoperations.

METHODS

A PubMed search was conducted for studies reporting outcomes of repeat epilepsy surgery. Studies were excluded if they reported fewer than five eligible patients or had average follow-ups < 1 year, and patients were excluded from analysis if they received a nonresective intervention. Outcomes were stratified by each variable of interest, and quantitative meta-analysis was performed to generate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Seven hundred eighty-two patients who received repeat resective epilepsy surgery from 36 studies were included. Engel I outcome was observed in 47% (n = 369) of patients. Significant predictors of seizure freedom included congruent over noncongruent electrophysiology data (OR = 3.6, 95% CI = 1.6-8.2), lesional over nonlesional epilepsy (OR = 3.2, 95% CI = 1.9-5.3), and surgical limitations over disease-related factors associated with failure of the first surgery (OR = 2.6, 95% CI = 1.3-5.3). Among patients with at least one of these predictors, seizure freedom was achieved in 58%. Conversely, the use of invasive monitoring was associated with worse outcome (OR = 0.4, 95% CI = 0.2-0.9). Temporal lobe over extratemporal/multilobe resection (OR = 1.5, 95% CI = 0.8-3.0) and abnormal over normal preoperative magnetic resonance imaging (OR = 1.9, 95% CI = 0.6-5.4) showed nonsignificant trends toward seizure freedom.

SIGNIFICANCE

This analysis supports considering further resection in patients with intractable epilepsy who continue to have debilitating seizures after an initial surgery, especially in the context of factors predictive of a favorable outcome.

Reoperation after failed resective epilepsy surgery in children

OBJECTIVE Although epilepsy surgery is an effective treatment option, at least 20%-40% of patients can continue to experience uncontrolled seizures resulting from incomplete resection of the lesion, epileptogenic zone, or secondary epileptogenesis. Reoperation could eliminate or improve seizures. Authors of this study evaluated outcomes following reoperation in a pediatric population. METHODS A retrospective single-center analysis of all patients who had undergone resective epilepsy surgery in the period from 2001 to 2013 was performed. After excluding children who had repeat hemispherotomy, there were 24 children who had undergone a second surgery and 2 children who had undergone a third surgery. All patients underwent MRI and video electroencephalography (VEEG) and 21 underwent magnetoencephalography (MEG) prior to reoperation. RESULTS The mean age at the first and second surgery was 7.66 (SD 4.11) and 10.67 (SD 4.02) years, respectively. The time between operations ranged from 0.03 to 9 years. At reoperation, 8 patients underwent extended cortical resection; 8, lobectomy; 5, lesionectomy; and 3, functional hemispherotomy. One year after reoperation, 58% of the children were completely seizure free (International League Against Epilepsy [ILAE] Class 1) and 75% had a reduction in seizures (ILAE Classes 1-4). Patients with MEG clustered dipoles were more likely to be seizure free than to have persistent seizures (71% vs 40%, p = 0.08). CONCLUSIONS Reoperation in children with recurrent seizures after the first epilepsy surgery could result in favorable seizure outcomes. Those with residual lesion after the first surgery should undergo complete resection of the lesion to improve seizure outcome. In addition to MRI and VEEG, MEG should be considered as part of the reevaluation prior to reoperation.

Failed epilepsy surgery: is this the end?

Resective epilepsy surgery can lead to sustained seizure control in 70-80% of patients evaluated for epilepsy surgery, indicating that up to 30% of patients still have recurrent seizures after surgery. Definitions of failed epilepsy surgery vary amongst studies. This review focuses on seizure outcome predictors after reoperation, possible mechanisms of failure and best management for this difficult patient population.

Interictal high-frequency oscillations in focal human epilepsy

PURPOSE OF REVIEW

Localization of focal epileptic brain is critical for successful epilepsy surgery and focal brain stimulation. Despite significant progress, roughly half of all patients undergoing focal surgical resection, and most patients receiving focal electrical stimulation, are not seizure free. There is intense interest in high-frequency oscillations (HFOs) recorded with intracranial electroencephalography as potential biomarkers to improve epileptogenic brain localization, resective surgery, and focal electrical stimulation. The present review examines the evidence that HFOs are clinically useful biomarkers.

RECENT FINDINGS

Performing the PubMed search 'High-Frequency Oscillations and Epilepsy' for 2013-2015 identifies 308 articles exploring HFO characteristics, physiological significance, and potential clinical applications.

SUMMARY

There is strong evidence that HFOs are spatially associated with epileptic brain. There remain, however, significant challenges for clinical translation of HFOs as epileptogenic brain biomarkers: Differentiating true HFO from the high-frequency power changes associated with increased neuronal firing and bandpass filtering sharp transients. Distinguishing pathological HFO from normal physiological HFO. Classifying tissue under individual electrodes as normal or pathological. Sharing data and algorithms so research results can be reproduced across laboratories. Multicenter prospective trials to provide definitive evidence of clinical utility.

The delta between postoperative seizure freedom and persistence: Automatically detected focal slow waves after epilepsy surgery

OBJECTIVE

In this study, we use a novel automated method for localization and quantitative comparison of magnetoencephalographic (MEG) delta activity in patients with and without recurrent seizures after epilepsy surgery as well as healthy controls.

METHODS

We identified the generators of delta activity by source location in frequency domain between 1 and 4 Hz in spontaneous MEG data. Comparison with healthy control subjects by z-transform emphasized relative changes of activation in patients. The individual results were compared to spike localizations and statistical group analysis was performed. Additionally, MEG results were compared to 1-4 Hz activity in invasive EEG (iEEG) in two patients, in whom this data was available.

RESULTS

Patients with recurrent seizures exhibited significantly increased focal MEG delta activity both in comparison to healthy controls and seizure free patients. This slow activity showed a correlation to interictal epileptic activity and was not explained by consequences of the resection alone. In two patients with iEEG, iEEG analysis was concordant with the MEG findings.

SIGNIFICANCE

The quantity of delta activity could be used as a diagnostic marker for recurrent seizures. The close relation to epileptic spike localizations and the resection volume of patients with successful second surgery imply involvement in seizure recurrence. This initial evidence suggests a potential application in the planning of second epilepsy surgery.

Epilepsy surgery in the posterior part of the brain

Posterior cortex epilepsy surgery is rarely performed and is associated with a high number of surgical failures, partly because accurate localization of the epileptogenic zone in the posterior part of the brain is extremely difficult. We present the characteristics as well as the surgical outcome and its determinants of a cohort of 208 consecutive patients (adults/children: 125/83) operated on for drug-resistant posterior cortex epilepsy at the "Claudio Munari" Epilepsy Surgery Centre, Milan between May 1996 and May 2013 (mean postsurgical follow-up: 9.6years). In addition, we highlight the differences in anatomoelectroclinical features and outcome between (i) patients who necessitated an invasive preoperative evaluation and those who proceeded directly to surgery and (ii) adults and children. Mean age at epilepsy onset was 6.8years (91.4% with onset before 14years of age). A high seizure frequency was reported by 51% of subjects, interictal and ictal EEG features were localizing in 16% and 28% of cases, and 86% of patients had a positive, judged as more or less informative, MRI. Invasive presurgical evaluation by stereoelectroencephalography was performed in 54% of patients; explorations may schematically be grouped in three main implantation patterns. Globally, 70% of subjects achieved seizure freedom, and further, 10% achieved Engel class II, with the patients operated on in childhood achieving significantly better postsurgical results in terms of seizure freedom and drug discontinuation. Duration of epilepsy represented the most consistent predictor of surgical outcome, with early surgery being correlated with higher chances of surgical success. Therefore, we recommend an early surgical referral in cases of pharmacoresistant posterior cortex seizures. Furthermore, we suggest that surgical failure might be predicted very early, namely within the first 6 postoperative months. We conclude that surgical management of posterior cortex epilepsy may attain excellent results.

Resective surgery for focal cortical dysplasia in children: a comparative analysis of the utility of intraoperative magnetic resonance imaging (iMRI)

PURPOSE

Seizure freedom following resection of focal cortical dysplasia (FCD) correlates with complete resection of the dysplastic cortical tissue. However, difficulty with intraoperative identification of the lesion may limit the ability to achieve the surgical objective of complete extirpation of these lesions. Intraoperative magnetic resonance imaging (iMRI) may aid in FCD resections. The objective of this study is to compare rates of postoperative seizure freedom, completeness of resection, and need for reoperation in patients undergoing iMRI-assisted FCD resection versus conventional surgical techniques.

METHODS

We retrospectively reviewed the medical records of pediatric subjects who underwent surgical resection of FCD at Children's National Medical Center between March 2005 and April 2015.

RESULTS

At the time of the last postoperative follow-up, 11 of the 12 patients (92 %) in the iMRI resection group were seizure free (Engel Class I), compared to 14 of the 42 patients (33 %) in the control resection group (p = 0.0005). All 12 of the iMRI patients (100 %) achieved complete resection, compared to 24 of 42 patients (57 %) in the control group (p = 0.01). One (8 %) patient from the iMRI-assisted resection group has required reoperation, compared to 17 (40 %) patients in the control resection group.

CONCLUSION

Our results suggest that the utilization of iMRI during surgery for resection of FCD results in improved postoperative seizure freedom, completeness of lesion resection, and reduction in the need for reoperation.

A second chance--reoperation in patients with failed surgery for intractable epilepsy: long-term outcome, neuropsychology and complications

OBJECT

Resective surgery is a safe and effective treatment of drug-resistant epilepsy. If surgery has failed reoperation after careful re-evaluation may be a reasonable option. This study was to summarise the risks and benefits of reoperation in patients with epilepsy.

METHODS

This is a retrospective single centre study comprising clinical data, long-term seizure outcome, neuropsychological outcome and postoperative complications of patients, who had undergone a second resective epilepsy surgery from 1989 to 2009.

RESULTS

A total of 66 patients with median follow-up of 10.3 years were included into the study. Fifty-one patients (77%) had surgery for temporal lobe epilepsy, the remaining 15 cases for extra-temporal lobe epilepsies. The most frequent histological findings were tumours (n=33, 50%), followed by dysplasia, gliosis (n=11, each) and hippocampus sclerosis (n=9). The main reasons for seizure recurrence were incomplete resection (59.1%) of the putative epileptogenic lesion. After reoperation 46 patients (69.7%) were completely seizure-free International League Against Epilepsy 1 (ILAE 1) at the last available follow-up. The neuropsychological evaluation demonstrated that repeated losses in the same cognitive domain, that is, successive changes from better to worse performance categories, were rare and that those losses after first surgery were followed by improvement rather than decline. However, reoperations lead to an increased rate of permanent neurological deficits (9%), overall surgical complications (9%) and visual field deficits (67%).

CONCLUSIONS

Reoperation after failed resective epilepsy surgery led to approximately 70% long-time seizure freedom and reasonable neuropsychological outcome. There is an increased risk of permanent postoperative neurological deficits, which should be taken into consideration when counselling for reoperation.

Factors associated with failed focal neocortical epilepsy surgery

BACKGROUND

Seizure outcomes after focal neocortical epilepsy (FNE) surgery are less favorable than after temporal lobectomy, and the reasons for surgical failure are incompletely understood. Few groups have performed an in-depth examination of seizure recurrences to identify possible reasons for failure.

OBJECTIVE

To elucidate factors contributing to FNE surgery failures.

METHODS

We reviewed resections for drug-resistant FNE performed at our institution between 1998 and 2011. We performed a quantitative analysis of seizure outcome predictors and a detailed qualitative review of failed surgical cases.

RESULTS

Of 138 resections in 125 FNE patients, 91 (66%) resulted in freedom from disabling seizures (Engel I outcome). Mean ± SEM patient age was 20.0 ± 1.2 years; mean follow-up was 3.8 years (range, 1-17 years); and 57% of patients were male. Less favorable (Engel II-IV) seizure outcome was predicted by higher preoperative seizure frequency (odds ratio = 0.85; 95% confidence interval, 0.78-0.93), a history of generalized tonic-clonic seizures (odds ratio = 0.42; 95% confidence interval, 0.18-0.97), and normal magnetic resonance imaging (odds ratio = 0.30; 95% confidence interval, 0.09-1.02). Among 36 surgical failures examined, 26 (72%) were related to extent of resection, with residual epileptic focus at the resection margins, whereas 10 (28%) involved location of resection, with an additional epileptogenic zone distant from the resection. Of 16 patients who received reoperation after seizure recurrence, 10 (63%) achieved seizure freedom.

CONCLUSION

Insufficient extent of resection is the most common reason for recurrent seizures after FNE surgery, although some patients harbor a remote epileptic focus. Many patients with incomplete seizure control are candidates for reoperation.

Repeat resective surgery in complex pediatric refractory epilepsy: lessons learned

OBJECT Resection can sometimes offer the best chance of meaningful seizure reduction in children with medically intractable epilepsy. However, when surgery fails to achieve the desired outcome, reoperation may be an option. The authors sought to investigate outcomes following resective reoperation in pediatric patients with refractory epilepsy, excluding tumoral epilepsies. Differences in preoperative workup between surgeries are analyzed to identify factors influencing outcomes and complications in this complex group. METHODS Medical records were reviewed for all pediatric patients undergoing a repeat resective surgery for refractory epilepsy at the authors' institution between 2005 and 2012. Tumor and vascular etiologies were excluded. Preoperative evaluation and outcomes were analyzed for each surgery and compared. RESULTS Ten patients met all inclusion criteria. The median age at seizure onset was 4.5 months. Preoperative MRI revealed no lesion in 30%. Nonspecific gliosis and cortical dysplasia were the most common pathologies. The majority of preoperative workups included MRI, video-electroencephalography (EEG), and SISCOM. Intracranial EEG was performed for 60% for the first presurgical evaluation and 70% for the second evaluation. The goal of surgery was palliative in 4 patients with widespread cortical dysplasia. The final Engel outcome was Class I in 50%. The rate of favorable outcome (Engel Class I-II) was 70%. The complication rate for the initial surgery was 10%. However, the rate increased to 50% with the second surgery, and 3 of these 5 complications were pseudomeningoceles requiring shunt placement (2 of the 3 patients underwent hemispherotomy). CONCLUSIONS Resective reoperation for pediatric refractory epilepsy has a high rate of favorable outcome and should be considered in appropriate candidates, even as a palliative measure. Intracranial EEG monitoring should be considered on initial workup in cases where the results of imaging or EEG studies are ambiguous or conflicting. Epilepsy secondary to cortical dysplasia, especially if the dysplasia is not seen clearly on MRI, can be difficult to cure surgically. Therefore, in these cases, as large a resection as can be safely accomplished should be done, particularly when the goal is palliative. The rate of complications, particularly pseudomeningocele ultimately requiring shunt placement, is much higher following reoperation, and patients should be counseled accordingly.

Effect of EEG electrode number on epileptic source localization in pediatric patients

OBJECTIVE

To investigate the relationship between EEG source localization and the number of scalp EEG recording channels.

METHODS

128 EEG channel recordings of 5 pediatric patients with medically intractable partial epilepsy were used to perform source localization of interictal spikes. The results were compared with surgical resection and intracranial recordings. Various electrode configurations were tested and a series of computer simulations based on a realistic head boundary element model were also performed in order to further validate the clinical findings.

RESULTS

The improvement seen in source localization substantially decreases as the number of electrodes increases. This finding was evaluated using the surgical resection, intracranial recordings and computer simulation. It was also shown in the simulation that increasing the electrode numbers could remedy the localization error of deep sources. A plateauing effect was seen in deep and superficial sources with further increasing the electrode number.

CONCLUSION

The source localization is improved when electrode numbers increase, but the absolute improvement in accuracy decreases with increasing electrode number.

SIGNIFICANCE

Increasing the electrode number helps decrease localization error and thus can more ably assist the physician to better plan for surgical procedures.

Reoperation for refractory epilepsy in childhood: a second chance for selected patients

BACKGROUND

Reoperations account for >10% in pediatric epilepsy surgery cohorts, and they are especially relevant in young children with catastrophic epilepsy.

OBJECTIVE

To determine surgical outcomes and their predictive factors in reoperations for refractory epilepsy in childhood.

METHODS

We retrospectively analyzed presurgical findings, resections, and outcomes of 23 consecutive children who underwent reoperations from 2000 to 2011.

RESULTS

Etiology included cortical dysplasia with/without glioneuronal tumor in 19 patients (83%), sole glioneuronal tumor in 2, and tuberous sclerosis and Rasmussen encephalitis in 1 each. The reasons for the failure of the initial surgery were functional considerations in 8 (35%), incorrect delineation of the epileptogenic zone in 8 (35%), and resection not performed as initially planned in 7 (30%) cases. Final procedures included 8 (35%) intralobar, 8 (35%) multilobar resections, and 7 (30%) hemispherotomies. Following reoperations, 14 (61%) patients were seizure free, 6 (26%) showed significant or worthwhile improvement, and 3 (13%) did not respond to surgery. Six of 8 patients who underwent the first resection before the age of 3 years, 6 of 8 whose first resection was limited by functional considerations, and all 7 with hemispherotomy as the final resection achieved seizure freedom after reoperation.

CONCLUSION

Reoperation is particularly beneficial for selected children with refractory epilepsy associated with cortical dysplasia that did not respond to an initial limited and/or early resection but achieved seizure freedom after extensive procedures. When indicated, reoperation should be performed at the youngest possible age to profit from higher functional plasticity in compensating for neurological deficit.

Health Technology Assessment report on the presurgical evaluation and surgical treatment of drug-resistant epilepsy

PURPOSE

Epilepsy is a neurologic disorder with major social impact. Surgery is a valuable option in patients who are not responding to antiepileptic drugs. The literature reports demonstrate that a proportion ranging from 40 to 100% of patients with epilepsy achieve seizure remission after surgery. A presurgical evaluation (clinical and instrumental) must be performed in all patients with drug-resistant epilepsy to assess their suitability for surgical intervention. Health Technology Assessment (HTA) represents a modern approach to the analysis of technologies used for health care. HTA could be considered a bridge between science that produces evidence and the decisions that can be taken on the basis of that evidence at different levels of the health care system. The aim of this study is the HTA of epilepsy surgery including clinical, ethical, social, and economic features.

METHODS

The present study includes an analysis of the diagnostic and surgical workup performed at the Italian centers for the diagnosis and treatment of drug-resistant epilepsy (DRE). The study includes the following issues: (1) social, ethical impact, and costs of the disease; (2) clinical results, efficacy, and safety of surgery; (3) ethics and quality of life after surgery; and (4) economic impact and productivity regained after surgery. The cost of managing a patient with DRE included in the presurgical study was estimated by the bottom-up microcosting technique that starts from a detailed collection of data on consumption of resources and full costing. The phases analyzed were (1) noninvasive diagnostic workup; (2) neurosurgical intervention; and (3) follow-up.

KEY FINDINGS

The literature reports indicate epilepsy surgery as an effective treatment both on clinical results and on ethical, social, and quality of life aspects. The workup including the noninvasive presurgical study followed by surgery has a total cost of €20,827. Management of short-term follow-up increases the overhead to €22,291 at the first year, and then to €23,571 after 5 years. According to the estimates made in this survey, funding based on diagnosis-related group (DRG) tariff for the noninvasive diagnostic stage involving hospital admission is not remunerative in Italy either at regional or national levels. Effectively the difference between full cost and DRG has a delta of €3,402 and €2,537 respectively. The total cost of the presurgical, surgical, and follow-up evaluation is not remunerative for €10,554 (national data).

SIGNIFICANCE

Economic surveys in Italy have shown that surgery for DRE is an advantageous treatment from the standpoint of third-party payers and is cost-effective for society. DRE presurgical evaluation and surgery are not remunerative either at regional or national levels.

Long-term seizure outcome following resective surgery for epilepsy: to be or not to be completely cured?

Surgical intervention is expected to improve the quality of life in patients with intractable epilepsy by providing adequate seizure control. Although many previous studies showed various rates of seizure freedom, definite conclusions have not yet been made regarding outcomes. In order to clarify the long-term postoperative outcome for a period up to 10 years, a retrospective review of our patients was performed longitudinally by using the survival analysis method. The postoperative state of epilepsy in 76 patients who underwent resection surgery was assessed based on Engel’s criteria. In addition, Kaplan-Meier survival analysis was used to calculate the probability of seizure freedom. In this patient group, abnormal lesion were detected by MRI in 70 out of 76 cases, and the ictal onset zone was finally identified within temporal lobe in 51 cases. The most favorable outcome, defined as Engel Class Ia, was observed in 26 (37%), 24 (40%), and 18 (41%) cases at 2, 5, and 10 years after surgery, respectively. The Kaplan-Meier survival curve in the overall group estimated the probability of seizure freedom as 75% (95% confidence interval [CI] 70–80%), 67% (62–72%), and 51% (45–57%) at 2, 5, and 10 years follow up, respectively. Half of all seizure recurrences occurred within the first 2 postoperative years. In this study, we showed that long-term favorable outcome of seizure control following resection surgery can be achieved in more than half of the patients.

Is reoperation an option for patients with temporal lobe epilepsy after failure of surgery?

PURPOSE

Epilepsy surgery is the most efficacious therapeutic modality for patients with medically refractory focal epilepsies, but surgical failures remain a challenge to the epilepsy treatment team. The aim of present study was to evaluate the postoperative outcome of patients who underwent reoperation after a failed epilepsy surgery on the temporal lobe.

METHODS

We systematically analyzed the results of comprehensive preoperative evaluations before the first surgery, and before and after reoperation in 17 patients with drug resistant temporal lobe epilepsies.

RESULTS

Overall, 13 of 17 patients (76.5%) improved after reoperation: five patients (29.4%) were completely seizure free after reoperation (median duration 60months, range 12-72); six patients (35.3%) were seizure free at least 12month before observation points (median duration 120.5months, range 35-155) and two patients (11.8%) had a decrease in seizure frequency. Four patients (23.5%) remained unchanged with respect to seizure frequency and severity. There was no correlation between the improvement in seizure outcome after reoperation and other clinical data except of the history of traumatic brain injury (TBI). The patients who had no history of TBI improved after reoperation, compared to patients with TBI (p=0.044). The postoperative seizure outcome of patients with incongruent Video-EEG results before the first surgery (p=0.116) and before reoperation (p=0.622) was not poorer compared to patients with congruent Video-EEG results.

CONCLUSIONS

Reoperation can considerably improve the operative outcome of the first failed epilepsy surgery in patients with drug resistant temporal lobe epilepsies. Epilepsy centres should be encouraged to report the results of failed epilepsy surgeries.

Individually tailored extratemporal epilepsy surgery in children: anatomo-electro-clinical features and outcome predictors in a population of 53 cases

Surgery for refractory extratemporal lobe epilepsy (ETLE) in the pediatric age group has been reported to be associated with a high percentage of failure and relapse. We performed a retrospective study of 53 consecutive patients with epilepsy onset before 12 years of age, who underwent, mostly at a pediatric age, an individually tailored ETLE surgery (32 in frontal and 21 in posterior cerebral areas) for pharmacoresistant seizures; these patients were selected and followed by a single national tertiary care pediatric center. Mean age at seizure onset was 3.14 years, and mean age at surgery was 11.23 years. Complete seizure freedom was achieved in 75% of the subjects. Short duration of illness before surgery, MRI features, no invasive pre-surgical evaluation, a localized interictal and ictal pattern as well as the presence of ictal fast activity on scalp EEG, localized interictal fast rhythms and absence of a diffuse initial ictal modification during SEEG, a complete resection of the epileptogenic zone, a type II FCD, and the absence of acute postoperative seizures correlated in a statistically significant way with a seizure-free outcome. We conclude that the seizure outcome of ETLE surgery in a carefully selected pediatric population can be excellent.

Seizure source imaging by means of FINE spatio-temporal dipole localization and directed transfer function in partial epilepsy patients

OBJECTIVE

To investigate the usage of a high-density EEG recording system and source imaging technique for localizing seizure activity in patients with medically intractable partial epilepsy.

METHODS

High-density, 76-channel scalp EEG signals were recorded in 10 patients with partial epilepsy. The patients underwent routine clinical pre-surgical evaluation and all had resective surgery with seizure free outcome. After applying a FINE (first principle vectors) spatio-temporal source localization and DTF (directed transfer function) connectivity analysis approach, ictal sources were imaged. Effects of number of scalp EEG electrodes on the seizure localization were also assessed using 76, 64, 48, 32, and 21 electrodes, respectively.

RESULTS

Surgical resections were used to assess the source imaging results. Results from the 76-channel EEG in the 10 patients showed high correlation with the surgically resected brain regions. The localization of seizure onset zone from 76-channel EEG showed improved source detection accuracy compared to other EEG configurations with fewer electrodes.

CONCLUSIONS

FINE together with DTF was able to localize seizure onset zones of partial epilepsy patients. High-density EEG recording can help achieve improved seizure source imaging.

SIGNIFICANCE

The present results suggest the promise of high-density EEG and electrical source imaging for noninvasively localizing seizure onset zones.

Impact of Failed Intracranial Epilepsy Surgery on the Effectiveness of Subsequent Vagus Nerve Stimulation

BACKGROUND

Using the Cyberonics registry, Amar and colleagues reported poorer efficacy of vagus nerve stimulation (VNS) in patients who failed intracranial epilepsy surgery (IES).

OBJECTIVE

To study the impact of failed IES and other surrogate marker of severe epilepsy on VNS effectiveness in a large cohort with treatment-resistant epilepsy (TRE).

METHODS

We retrospectively reviewed 376 patients (188 female patients; 265 adults; mean age, 29.4 years at implantation) with TRE who underwent VNS implantation between 1997 and 2008 and had at least 1 year of follow-up. One hundred ten patients (29.3%) had failed ≥1 prior craniotomies for TRE, and 266 (70.7%) had no history of IES.

RESULTS

The mean duration of VNS therapy was 5.1 years. Patients with prior IES were more commonly male and adult, had a greater number of seizure types, and more commonly had focal or multifocal vs generalized seizures (P &gt; .05). There was no significant difference in the mean percentage seizure reduction between patients with and without a history of IES (59.1% vs 56.5%; P = .42). There was no correlation between type of failed IES (callosotomy vs resection) and seizure reduction with VNS therapy.

CONCLUSION

Failed IES did not affect the response to VNS therapy. Unlike prior reports, patients with callosotomy did not respond better than those who had resective surgery. Nearly 50% of patients experienced at least 50% reduction in seizure frequency. For patients with TRE, including patients who failed cranial epilepsy surgeries, VNS should be considered a palliative treatment option.

Reoperation after selective amygdalohippocampectomy: an MRI analysis of the extent of temporomesial resection in ten cases

BACKGROUND

Selective amygdalohippocampectomy (SAHE) yields 60-80% of patients with medically refractory mesial temporal lobe epilepsy seizure-free and seems to be equally effective compared to the more extended temporal lobe resections. The resection of the entire entorhinal cortex (EC) is of crucial importance to warrant complete seizure control for those patients. Thus, evidence of residual EC could be a predictor of a potentially successful reoperation in patients with recurrent seizures after SAHE. We performed an analysis of preoperative and postoperative magnetic resonance imaging (MRI) in patients who underwent a reoperation after an unsuccessful transsylvian SAHE to assess the presence of residual EC before reoperation and to determine whether certain anatomical variants may dispose patients to incomplete resection of EC.

MATERIALS AND METHODS

Ten patients who underwent reoperation after SAHE for the recurrence of medically refractory seizures were studied. MRI after SAHE was assessed for the presence of residual EC using T2-weighted and inversion recovery sequences perpendicularly to the main axis of the hippocampus. The results were compared with a control group of ten patients who became seizure-free after SAHE. In the nine patients of the study group, the sulcal anatomy of the basal temporal lobe was graphically outlined and analysed on MRI scans performed before SAHE to characterise the sulcal boundaries of the EC.

FINDINGS

Residual EC was found in nine of ten patients and was absent in the control group. After reoperation (median follow-up of 36.5 months), eight out of ten patients were completely seizure-free. In seven out of nine patients, a discontinuous course of the lateral sulcal boundaries of the EC was determined.

CONCLUSIONS

Careful analysis of MRI verified residual mesiotemporal structures in the majority of patients who became seizure-free after reoperation. Certain temporobasal sulcal patterns might dispose for a higher risk of incomplete resection of the EC. The study confirms that reoperation is an effective treatment modality for patients with recurrent seizures after transsylvian SAHE.

AES 2009 Annual Course: Reoperation for medically refractory epilepsy

A significant percentage of patients undergoing resective surgery for medically refractory epilepsy have persistent or recurrent disabling seizures. In these patients, the objective of seizure freedom justifies the consideration of repeat resective surgery. In this report, the available published experience with repeat resective surgery is analyzed. The reoperated patients are subdivided into three categories: patients with residual medial temporal structures, patients with an unresected or partially resected structural/mass (non-glioma) lesion and patients with non-lesional neocortical epilepsy. This analysis indicates that the chance of achieving seizure freedom is significant, although lower than with the initial surgery. The chance of significant morbidity (particularly significant neurologic deficit) is low, although higher than with the initial surgery. A proper evaluation can identify appropriate candidates for a resective reoperation. Palliative surgical options should be strongly considered for all patients, especially for those with lower chance of seizure freedom and/or elevated risk of morbidity.

Acute postoperative seizures after epilepsy surgery - a long-term outcome predictor?

OBJECTIVES

The prognostic value of acute postoperative seizures (APS) after epilepsy surgery is much debated. This study evaluated APS, defined as seizures in the first week post-surgery, as a predictor of long-term seizure outcome, and investigated the utility of other potential outcome predictors.

MATERIALS AND METHODS

Medical records of 48 patients with temporal and extra-temporal epilepsy surgery were studied. Forty patients had lesional surgery. All had at least 2 year postoperative follow-up.

RESULTS

At 2 year follow-up, 25 patients (53%) were seizure free. Univariate analysis showed that APS (P = 0.048), using ≥ six AEDs prior to surgery (P = 0.03), pathological postoperative EEG (P = 0.043) and female gender (P = 0.012) were associated with seizure recurrence.

CONCLUSIONS

Univariate analysis indicate that APS, a high number of AEDs used prior to surgery, and pathological postoperative EEG are possible predictors of seizure recurrence after epilepsy surgery. Only gender retained significance in the multivariate analysis.

Analysis of Reoperation in Mesial Temporal Lobe Epilepsy With Hippocampal Sclerosis

BACKGROUND:

Most patients do well after epilepsy surgery for mesial temporal lobe sclerosis, and in only 8 to 12% of all operations, the outcome is classified as not improved.

OBJECTIVE:

To analyze the outcome of reoperation in cases of incomplete resection of mesial temporal lobe structures in patients with mesial temporal lobe sclerosis in temporal lobe epilepsy.

METHODS:

We analyzed 22 consecutive patients who underwent reoperation for mesial temporal lobe sclerosis (follow-up, 23-112 months; mean, 43.18 months) by evaluating noninvasive electroencephalographic/video monitoring before the first and second surgeries (semiology, interictal epileptiform discharges, ictal electroencephalography with special attention to the secondary contralateral evolution of the electroencephalographic seizure pattern after the initial regionalization), and magnetic resonance imaging (resection indices after the first and second surgeries on the amygdala, hippocampus, lateral temporal lobe). In 18 of 22 patients T2 relaxometry of the contralateral hippocampus was performed.

RESULTS:

Nine of 22 patients became seizure free; another 4 patients had a decrease in seizures and eventually became seizure free (range, 16-51 months; mean, 30.3). Recurrence of seizures is associated with (1) ictal electroencephalography with later evolution of an independent pattern over the contralateral temporal lobe (0 of 5 patients seizure free vs 5 of 7 patients non–seizure free; P = .046) and (2) a smaller amount of lateral temporal lobe resection in the second surgery (1.06 ± 0.59 cm vs 2.18 ± 1.37 cm; P = .019). No significant correlation with outcome was found for lateralization of interictal epileptiform discharges, change in semiology, other resection indices, T2 relaxometry, onset and duration of epilepsy, duration of follow-up, and side of surgery.

CONCLUSION:

Patients have a less favorable outcome with a reoperation if they show ictal scalp electroencephalography with secondary contralateral propagation and if only a small second resection of the lateral temporal lobe is performed.

Temporal lobe epilepsy surgery failures: predictors of seizure recurrence, yield of reevaluation, and outcome following reoperation

Object

The authors provide a systematic analysis of electroclinical characteristics in patients with persistent seizures following temporal lobe epilepsy (TLE) surgery and identify ideal candidates for reoperation.

Methods

The authors retrospectively reviewed the records of 68 adult patients (mean follow-up 8.7 years) who underwent a video electroencephalography evaluation and high-resolution imaging after failed TLE surgery performed between 1990 and 2004 at The Cleveland Clinic. Multivariate logistic regression analyses were performed to identify predictors of the yield of a repeat evaluation, location of the recurrence focus, and outcome following reoperation.

Results

Although a focus of recurrence was identified in 44 patients, only 15 underwent reoperation, and only 6 of these became seizure free. Localized foci of recurrence were successfully identified in patients with early (within 1 postoperative year) and frequent (≥ 4 per month) recurrent seizures (yield of 100% if both conditions were fulfilled). Predictors of contiguity of the focus of recurrence to the initial surgical bed were variable depending on the type of the initial surgery: patients with baseline contralateral temporal spiking were 6 times (OR 6.34, p < 0.05) more likely to experience seizure recurrence from the contralateral temporal lobe after a “standard” temporal lobectomy, while the need to use subdural electrodes and the timing of recurrence were more significant following limited temporal resections. The focus of recurrence was distant to the original surgical bed when subdural electrodes were used prior to first surgery (OR 28.0, p = 0.01) or when seizures recurred early (within < 6 postoperative months; OR 12.5, p = 0.04). With reoperation, only patients with mesial and basal extension of the temporal resections became seizure free. Interestingly, seizure freedom was achieved with medical therapy alone in 42% of patients with a nonidentifiable recurrence focus as opposed to 4% of those with an unoperated identifiable focus.

Conclusions

The timing and frequency of recurrent seizures following unsuccessful TLE surgery provide useful guidelines for the yield of a surgical reevaluation, and potentially for the mechanisms of surgical failure.

Stereotactic electroencephalography with temporal grid and mesial temporal depth electrode coverage: does technique of depth electrode placement affect outcome?

OBJECT

Intracranial monitoring for temporal lobe seizure localization to differentiate neocortical from mesial temporal onset seizures requires both neocortical subdural grids and hippocampal depth electrode implantation. There are 2 basic techniques for hippocampal depth electrode implantation. This first technique uses a stereotactically guided 8-contact depth electrode directed along the long axis of the hippocampus to the amygdala via an occipital bur hole. The second technique involves direct placement of 2 or 3 4-contact depth electrodes perpendicular to the temporal lobe through the middle temporal gyrus and overlying subdural grid. The purpose of this study was to determine whether one technique was superior to the other by examining monitoring success and complications.

METHODS

Between 1997 and 2005, 41 patients underwent invasive seizure monitoring with both temporal subdural grids and depth electrodes placed in 2 ways. Patients in Group A underwent the first technique, and patients in Group B underwent the second technique.

RESULTS

Group A consisted of 26 patients and Group B 15 patients. There were no statistically significant differences between Groups A and B regarding demographics, monitoring duration, seizure localization, or outcome (Engel classification). There was a statistically significant difference at the point in time at which these techniques were used: Group A represented more patients earlier in the series than Group B (p < 0.05). The complication rate attributable to the grids and depth electrodes was 0% in each group. It was more likely that the depth electrodes were placed through the grid if there was a prior resection and the patient was undergoing a new evaluation (p < 0.05). Furthermore, Group A procedures took significantly longer than Group B procedures.

CONCLUSIONS

In this patient series, there was no difference in efficacy of monitoring, complications, or outcome between hippocampal depth electrodes placed laterally through temporal grids or using an occipital bur hole stereotactic approach. Placement of the depth electrodes perpendicularly through the grids and middle temporal gyrus is technically more practical because multiple head positions and redraping are unnecessary, resulting in shorter operative times with comparable results.

Surgical outcomes in lesional and non-lesional epilepsy: a systematic review and meta-analysis

PURPOSES

To provide evidence-based quantitative summary estimates of seizure outcomes in patients with non-lesional and lesional epilepsy treated with surgery, and to assess the consistency of results among published studies.

METHODS

An exhaustive literature search identified articles published since 1995, describing outcomes according to lesional status in patients of any age who underwent resective epilepsy surgery. Two reviewers independently assessed study eligibility and extracted the data. Disagreements were resolved through discussion. Random effects meta-analyses were used after assessing the dataset for heterogeneity.

RESULTS

Forty articles fulfilled eligibility criteria and described outcomes in 697 patients with non-lesional epilepsy and 2860 patients with lesional epilepsy. Overall, the odds of being seizure-free after surgery were 2.5 times higher in patients with lesions on MRI or histopathology (OR 2.5, 95%CI 2.1, 3.0, p<0.001). In patients with temporal lobe epilepsy surgery the odds were 2.7 times higher in those with lesions (OR 2.7, 95%CI 2.1, 3.5, p<0.001). In patients with extratemporal epilepsy surgery the odds were 2.9 higher in those with lesions (OR 2.9, 95%CI 1.6, 5.1, p<0.001). Outcomes were similar in children, adults, and studies that used MRI or histopathology to identify lesions.

DISCUSSION

Overall, the odds of seizure freedom after surgery are two to three times higher in the presence of a lesion on histopathology or MRI. The results are clinically and statistically significant, consistent across various subgroups, and quite homogeneous across studies.