Extratemporal Epilepsy Surgery Research Articles

Epilepsy Surgery in Extratemporal vs Temporal Lobe Epilepsy: Changes in Surgical Volumes and Seizure Outcome Between 1990 and 2017.

Seizure outcome after extratemporal lobe epilepsy (exTLE) surgery has often been poorer than after temporal lobe epilepsy (TLE) surgery, but recent improvements in diagnostics and surgery may have changed this. Our aim was to analyze the changes in presurgical and surgical volumes and seizure outcome 2 years after surgery for patients with exTLE compared with those with TLE. We performed a retrospective, single-center cohort study including patients from the Bethel presurgical-surgical-postsurgical database from 1990 to 2017. We used logistic regression to analyze factors influencing the odds for surgery and the odds for seizure freedom after surgery. We included 3,822 patients with presurgical evaluation, 2,404 of whom had subsequently undergone surgery. The proportion of patients with exTLE in presurgical evaluation increased from 41% between 1990 and 1993 to 64% in 2014-2017. The odds for surgery decreased over time (2003-2011: odds ratio [OR] 0.50 [95% CI 0.36-0.70]; 2012-2017: OR 0.24 [CI 0.17-0.35]; reference: 1990-2002) and patients with exTLE had lower odds for surgery than patients with TLE, but this difference diminished over time (exTLE vs TLE 1990-2002: OR 0.14 [CI 0.09-0.20]; 2003-2011: OR 0.32 [CI 0.24-0.44]; 2012-2017: OR 0.46 [CI 0.34-0.63]). Etiology, the side of the epileptogenic lesion, and invasive recordings influenced the odds for surgery. The most frequent reasons for not undergoing surgery were missing identification of a circumscribed epileptogenic zone or an unacceptable risk of postsurgical deficits in patients with exTLE and the patient's decision in patients with TLE. Compared with patients with TLE, the odds for seizure freedom after surgery started lower for patients with exTLE in earlier years, but increased (≤2 lobes 1990-2002: OR 0.47 [CI 0.33-0.68]; 2003-2011: OR 0.62 [CI 0.44-0.87]; 2012-2017: OR 0.78 [CI 0.53-1.15]; ≥3 lobes 1990-2002: OR 0.37 [CI 0.22-0.62]; 2003-2011: OR 0.73 [CI 0.43-1.23]; 2012-2017: OR 1.46 [CI 0.91-2.42]). Etiology, age at surgery, and invasive recordings were further predictors for the odds for seizure freedom. Over the past 28 years, the success of resective surgery for patients with exTLE has improved. At the same time, the number of patients with exTLE being evaluated for surgery increased, as well as their odds for undergoing surgery.

Seizure latency and epilepsy localization as predictors of recurrence following epilepsy surgery

The primary purpose is to determine whether the time between epilepsy surgery and first seizure recurrence can estimate the timing of the next seizure event for temporal and extratemporal epilepsy. A secondary endpoint aimed to compare temporal and extratemporal epilepsy surgery and examine which subgroup has a higher hazard of subsequent seizure recurrence. Data used were from a retrospective database at Thomas Jefferson University Hospital. Records were stratified into temporal (n=943) and extratemporal (n=125) surgeries. Analyses were done using SAS and utilized Cox proportional hazards models while controlling for demographics and clinical factors. The primary predictor of time between surgery and first recurrence was treated as a nominal variable binned into six segments, whereas secondary endpoints used a categorical predictor of epilepsy location while controlling for seizure latency. Generally, as seizure latency following surgery increased, the time between first seizure and second seizure increased. These results were statistically meaningful in the temporal set (Wald chi-squared = 40.4715, df=5, p<.0001). Outcomes could also be interpreted based on predictor group; for instance, if Seizure 1 occurred 1-2 months following surgery in the temporal set, the median number of days until the next seizure was 35.5days (95% confidence interval [CI] = 21-89days). Secondary analysis showed that temporal lobe epilepsy had a lower hazard of a second seizure than extratemporal lobe epilepsy (89.2% reduction in hazard; 95% CI = .015-.795). This analysis provides a framework to use initial seizure latency to predict the median number of days until the next seizure event, while stratifying based on epilepsy location and controlling for multiple variables. It also suggests that the hazard of seizure recurrence in temporal lobe epilepsy is lower than in extratemporal lobe epilepsy.

Factors Associated with Short-Term Seizure Recurrence in Extratemporal Epilepsy Surgery

Introduction: Drug-resistant extratemporal epilepsy is the second cause of referral to epilepsy surgery. Objectives: To identify factors associated with short-term seizure recurrence following extratemporal epilepsy surgery. Materials and Methods: We performed a retrospective study of 19 consecutive patients who underwent surgery for drug-resistant extratemporal epilepsy at the National Institute of Neurology and Neurosurgery of Havana, Cuba, from September 2014 to October 2019. All patients had at least one year of postoperative follow-up. Fisher's exact test was used to search for an association between dichotomous variables. A value of p≤0.05 was considered significant. Results: After one year of follow-up, seizure freedom reached 31.6% (Engel I) and 36.8% showed significant improvement in the number of seizures (Engel II). The frontal location (p=0.046) and incomplete resection of the epileptogenic zone (p=0.017), bilateral interictal discharges on the preoperative electroencephalogram (EEG) (p=0.017), the presence of epileptiform discharges on the postsurgical EEG (p=0.001), and the occurrence of seizures after the sixth month of surgery (p=0.001), were associated with seizures recurrence. Conclusions: After one year, 31.6% of patients operated on for extratemporal epilepsy were seizure-free. The incomplete resection of the epileptogenic zone and the presence of epileptogenic discharges in the postsurgical EEG, and the presence of seizures after the sixth month of surgery were the most significant factors of seizure recurrence.

Epilepsy surgery for refractory seizures: a systematic review and meta-analysis in different complications

BackgroundNearly one-third of epilepsy patients are refractory/resistant to medical treatment. Developments made in surgical techniques have significantly increased the effectiveness and safety of these techniques, as such techniques have been demonstrated to improve seizure control/freedom outcomes.ObjectivesThe aim of this systematic review and meta-analysis was to evaluate the complications of epilepsy surgery.Patient and methodsThe searches were conducted by three independent researchers to find the relevant studies published from January 1, 2009, until the end of January 6, 2019. For English published statistical studies, all studies conducted on epileptic patients who have undergone epilepsy surgery were included.Statistical analysisA meta-analysis was conducted in the STATA14 statistical software.ResultsA total of 6735 patients with epilepsy who had undergone the epilepsy surgery were studied. The overall prevalence of complications was 5%. The prevalence of major and minor complications was 5.4% and 3.2% respectively. The prevalence of complications related to the temporal epilepsy surgery and the extra-temporal epilepsy surgery based on 3 studies was 7.9% and 8.2 % respectively. The frequency of neurological and surgical complications after epilepsy surgery was 4.4% and 4.1% respectively.ConclusionThe overall rate of complications caused by epilepsy surgery was reasonably low (5%), implying that epilepsy surgery especially temporal lobe resection can be safe preferably when performed by an experienced surgeon.

Surgical Treatment of Extratemporal Epilepsy: Results and Prognostic Factors.

Surgery is a widely accepted option for the treatment of pharmacoresistant epilepsies of extratemporal origin. To analyze clinical and epileptological results and to provide prognostic factors influencing seizure outcome. This retrospective single-center study comprises a consecutive series of 383 patients, most of whom had an identifiable lesion on MRI, who underwent resective surgery for extratemporal epilepsy. Data including diagnostic modalities, surgical treatment, histopathology, prognostic factors, and epileptological outcome were analyzed. Resective procedures were located as follows: frontal (n = 183), parietal (n = 44), occipital (n = 24), and insular (n = 24). In 108 cases resection included more than 1 lobe. Histopatholological evaluation revealed focal cortical dysplasias (n = 178), tumors (n = 110), cavernomas (n = 27), gliosis (n = 42), and nonspecific findings (n = 36). A distinct epileptogenic lesion was detected in 338 (88.7%) patients. After a mean follow-up of 54 mo, 227 (62.5%) patients remained free from disabling seizures (Engel class I), and 178 (49%) were completely seizure free (Engel class Ia). There was no perioperative mortality. Permanent morbidity was encountered in 46 cases (11.8%). The following predictors were significantly associated with excellent seizure outcome (Engel I): lesion visible on magnetic resonance imaging (MRI; P = .02), noneloquent location (P = .01), complete resection of the lesion (P = .001), absence of epileptic activity postoperatively (P = .001), circumscribed histological findings (P = .001), lower age at surgery (P = .008), and shorter duration of epilepsy (P = .02). Surgical treatment of extratemporal epilepsy provides satisfying epileptological results with an acceptable morbidity. Best results can be achieved in younger patients with circumscribed MRI lesions, which can be resected completely.

Psychosocial outcome in epilepsy after extratemporal surgery

ObjectiveOnly limited data exist on psychosocial long-term outcome after epilepsy surgery in patients with extratemporal epilepsy. The aim of this study was to investigate psychosocial outcome after extratemporal epilepsy surgery and to assess factors predicting favorable outcome. MethodSixty-five out of 104 eligible patients who had undergone extratemporal epilepsy surgery at our epilepsy center between 1990 and 2015 (mean age: 42.2. years; 75% of the resections in the frontal lobe) completed a questionnaire asking about seizure status, employment status, marital and living situation, driving status, depressive symptoms, and quality of life (QOL). Follow-up was on average 9.2years after surgery (range: 1–26years). ResultsThirty-eight (58%) patients were free of disabling seizures (Engel class I), and 28 (43%) have not experienced any seizures after surgery (Engel class IA). Employment rate in the primary labor market remained at 45%, but more patients lost employment (14%) than gained employment (8%). Postoperative employment was predicted by preoperative employment (p=.007), seizure freedom (p=.025), older age at seizure onset (p=.018), younger age at follow-up (p=.035), and female gender (p=.048). Seizure-free patients were more likely to be driving; have a partner, particularly in males; and have lower depressive scores. Quality of life at follow-up was best predicted by employment (p=.012), partnership (p=.025), and seizure freedom (p=.025). In contrast, recurrence of seizures and early seizure onset were associated with poor psychosocial outcome, particularly in men. ConclusionThe study provides support that extratemporal surgery can lead to improved QOL and favorable psychosocial outcome. Seizure freedom is important but not the only determinant of good psychosocial outcome.

Insular Cortex Surgery for the Treatment of Refractory Epilepsy.

Focal epilepsy originating from the insular cortex is rare. One reason is the small amount of cortical tissue compared with other lobes of the brain. However, the incidence of insular epilepsy might be underestimated because of diagnostic difficulties. The semiology and the surface EEG are often not meaningful or even misleading, and elaborated imaging might be necessary. The close connections of the insular cortex with other potentially epileptogenic areas, such as the temporal lobe or frontal/central cortex, is increasingly recognized as possible reason for failure of epilepsy surgery for temporal or extratemporal seizures. Therefore, some centers consider invasive EEG recording of the insular cortex not only in case of insular epilepsy but also in other focal epilepsies with nonconclusive results from the presurgical work-up. The surgical approach to and resection of insular cortex is challenging because of its deep location and proximity to highly eloquent brain structures. Over the last decades, technical adjuncts like navigation tools, electrophysiological monitoring and intraoperative imaging have improved the outcome after surgery. Nevertheless, there is still a considerable rate of postoperative transient or permanent deficits, in some cases as unavoidable and calculated deficits. In most of the recent series, seizure outcome was favorable and comparable with extratemporal epilepsy surgery or even better. Up to now, the data volume concerning long-term follow-up is limited. This review focusses on the surgical challenges of resections to treat insular epilepsy, on prognostic factors concerning seizure outcome, on postoperative deficits and complications. Moreover, less invasive surgical techniques to treat epilepsy in this highly eloquent area are summarized.

Mesial Extratemporal Lobe Epilepsy: Clinical Features and Surgical Strategies.

Extratemporal lobe epilepsy surgery remains a diagnostic and therapeutic challenge. Scalp electroencephalography (EEG) correlates, clinical semiology, and imaging findings are often ambiguous or difficult to interpret, necessitating the need for invasive recordings. This is particularly true for those extratemporal lobe epilepsy cases in which seizures develop from the midline. The aim of this study was to examine the clinical features and surgical strategies in mesial extratemporal lobe epilepsy. A retrospective study reviewing clinical and surgical characteristics was conducted in 30 patients who underwent epilepsy surgery in mesial extratemporal areas at our institution between 1991 and 2011. Although the location of the epileptogenic zone was associated with specific seizure types, semiology proved to be heterogeneous. Although scalp EEG was of good lateralizing value, it was poor for localizing the epileptogenic zone, necessitating a frequent need for invasive electroencephalographic recordings. Surgical resections in mesial extratemporal regions were found to be safe and resulted in satisfactory seizure outcomes.

Resection planning in extratemporal epilepsy surgery using 3D multimodality imaging and intraoperative MRI

Surgical resection in non-lesional, extratemporal epilepsy, informed by stereoEEG recordings, is challenging. There are no clear borders of resection, and the surgeon is often operating in deep areas of the brain that are difficult to access. We present a technical note where 3D multimodality image integration in EpiNavTM is used to build a planned resection model, based on a previous intracranial EEG evaluation. Intraoperative MRI is then used to ensure a complete resection of the planned model. As stereoEEG becomes more common in the presurgical evaluation of epilepsy, these tools will become increasingly important to facilitate targeted cortical resections.

Rate and complications of adult epilepsy surgery in North America: Analysis of multiple databases

Epilepsy surgery is under-utilized, but recent studies reach conflicting conclusions regarding whether epilepsy surgery rates are currently declining, increasing, or remaining steady. However, data in these prior studies are biased toward high-volume epilepsy centers, or originate from sources that do not disaggregate various procedure types.All major epilepsy surgery procedures were extracted from the Centers for Medicare and Medicaid Services Part B National Summary Data File and the American College of Surgeons National Surgical Quality Improvement Program. Procedure rates, trends, and complications were analyzed, and patient-level predictors of postoperative adverse events were identified.Between 2000–2013, 6200 cases of epilepsy surgery were identified. Temporal lobectomy was the most common procedure (59% of cases), and most did not utilize electrocorticography (63–64%). Neither temporal nor extratemporal lobe epilepsy surgery rates changed significantly during the study period, suggesting no change in utilization. Adverse events, including major and minor complications, occurred in 15.3% of temporal lobectomies and 55.6% of hemispherectomies.Our findings suggest stagnant rates of both temporal and extratemporal lobe epilepsy surgery across U.S. surgical centers over the past decade. This finding contrasts with prior reports suggesting a recent dramatic decline in temporal lobectomy rates at high-volume epilepsy centers. We also observed higher rates of adverse events when both low- and high-volume centers were examined together, as compared to reports from high-volume centers alone. This is consistent with the presence of a volume-outcome relationship in epilepsy surgery.

Role of concordance between ictal-subtracted SPECT and PET in predicting long-term outcomes after epilepsy surgery

F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) and ictally subtracted single photon emission tomography (iSPECT) are important for localizing the epileptogenic focus. The following study analyzes the role of inter-concordance between FDG-PET and iSPECT in predicting long-term outcomes after epilepsy surgery. We prospectively evaluated (January 2003-January 2008) patients undergoing surgery for temporal or extratemporal drug refractory epilepsy (DRE) who had at least a 5 years follow up. Patients with MRI and video EEG (vEEG) concordance for the seizure focus underwent iSPECT and FDG-PET. Concordance of the iSPECT and FDG-PET with each other and with the substrate (defined by MRI and vEEG) for temporal and extra-temporal epilepsies was evaluated and correlated with outcomes. One hundred twenty-three patients (74 males) were included in the study (mean age at time of surgery: 18.9±10.41 years). The mean age of onset of seizures was 9.87±8.37 years. The most common semiology was complex partial (45%). When both FDG-PET and iSPECT were concordant with each other, this translated into a (class I Engel at 5 years) outcome of 62% for extra-temporal epilepsies (provided they were also concordant with the lesion, as defined by MRI and vEEG). This percentage was significant (p<0.01) compared with all other situations (both FDG-PET/iSPECT not concordant to MRI/vEEG, only PET or iSPECT concordant with MRI/vEEG). This correlation was not found for the temporal epilepsies, where the MRI and vEEG were the most important prognostic parameters. In both temporal and extratemporal epilepsies the concordance of the iSPECT/FDG-PET with the MRI/vEEG correlated with a better 5-year outcome (temporal: 70% vs 25%; extra-temporal: 62% vs 33%; p<0.05). Concordance between non-invasive investigations iSPECT and FDG-PET is an important predictive factor for surgical outcomes in extra-temporal epilepsy.

Acute postoperative seizures and long-term outcome following pediatric epilepsy surgery

PurposeAcute post-operative seizures (APOS) after epilepsy surgery, previously believed to be benign, are increasingly associated with poor long-term prognosis. Prior literature has focused primarily on adult temporal lobe epilepsy. This retrospective study aimed to identify the prevalence, prognostic significance and risk factors for APOS in pediatric epilepsy surgery at a single center. MethodRetrospective chart review of all children aged 0–21 years undergoing resective surgery for epilepsy between 2009 and 2012 at a single center. APOS were defined as seizures within 30 days of resection. Surgical outcome was determined, using a minimum of 12 months postoperative follow-up for inclusion. ResultsAPOS, defined as a seizure within 30 days of resection, were identified in 50/112 (44%) of patients. APOS were a significant predictor of poor postoperative seizure outcome (ILAE 4–6); only 26% of those with APOS had a good outcome (ILAE 1–3), compared to 76% without APOS. Timing of postoperative seizure was not correlated with outcome. Most (54%) with APOS and good outcome had continued seizures between 14-30 days postoperatively. Patients with APOS after temporal (p=0.05) and extratemporal (p<0.001) resections had a significantly worse prognosis. APOS after hemispherectomy were not associated with a worse prognosis (p=0.22). Key risk factors for APOS include lack of ictal EEG lateralization to operated hemisphere/side of MRI abnormality. ConclusionThis study shows an association between APOS and poor outcome in both temporal and extratemporal pediatric epilepsy surgery. Findings support the expansion of APOS duration to 30 days.

Long-term Outcomes After Nonlesional Extratemporal Lobe Epilepsy Surgery

A focal lesion detected by use of magnetic resonance imaging (MRI) is a favorable prognostic finding for epilepsy surgery. Patients with normal MRI findings and extratemporal lobe epilepsy have less favorable outcomes. Most studies investigating the outcomes of patients with normal MRI findings who underwent (nonlesional) extratemporal epilepsy surgery are confined to a highly select group of patients with limited follow-up. To evaluate noninvasive diagnostic test results and their association with excellent surgical outcomes (defined using Engel classes I-IIA of surgical outcomes) in a group of patients with medically resistant nonlesional extratemporal epilepsy. A retrospective study. Mayo Clinic, Rochester, Minnesota. From 1997 through 2002, we identified 85 patients with medically resistant extratemporal lobe epilepsy who had normal MRI findings. Based on a standardized presurgical evaluation and review at a multidisciplinary epilepsy surgery conference, some of these patients were selected for intracranial electroencephalographic (EEG) monitoring and epilepsy surgery. Nonlesional extratemporal lobe epilepsy surgery. The results of noninvasive diagnostic tests and the clinical variables potentially associated with excellent surgical outcome were examined in patients with a minimum follow-up of 1 year (mean follow-up, 9 years). Based on the noninvasive diagnostic test results, a clear hypothesis for seizure origin was possible for 47 of the 85 patients (55%), and 31 of these 47 patients (66%) proceeded to intracranial EEG monitoring. For 24 of these 31 patients undergoing long-term intracranial EEG (77%), a seizure focus was identified and surgically resected. Of these 24 patients, 9 (38%) had an excellent outcome after resective epilepsy surgery. All patients with an excellent surgical outcome had at least 10 years of follow-up. Univariate analysis showed that localized interictal epileptiform discharges on scalp EEGs were associated with an excellent surgical outcome. Scalp EEG was the most useful test for identifying patients with normal MRI findings and extratemporal lobe epilepsy who were likely to have excellent outcomes after epilepsy surgery. Extending outcome analysis beyond the resective surgery group to the entire group of patients who were evaluated further highlights the challenge that these patients pose. Although 9 of 24 patients undergoing resective surgery (38%) had excellent outcomes, only 9 of 31 patients undergoing intracranial EEG (29%) and only 9 of 85 patient with nonlesional extratemporal lobe epilepsy (11%) had long-term excellent outcomes.

Update on the surgical treatment of epilepsy

Using the most recent evidence, we provide an update about epilepsy surgery, focusing on the presurgical evaluation and surgical planning, epilepsy surgery outcomes, and utilization. Great strides are being achieved in the presurgical evaluation and planning for epilepsy surgery, including fundamental advances in imaging and neurophysiology. A recent randomized controlled trial demonstrates that early surgery for patients with mesial temporal lobe epilepsy (TLE) is superior to medical therapy. The enduring benefits of surgery continue to be demonstrated, particularly after TLE surgery. However, studies examining the long-term outcomes after extratemporal lobe epilepsy surgery are scarce. Surgery is generally associated with an improvement in depression, but mostly in those with good surgical outcome. Complications from invasive monitoring or after epilepsy surgery are generally temporary, or limited in their symptomatology. One area in need of prospective studies is the topic of antiepileptic drug withdrawal after epilepsy surgery (Who? When? How?). Despite its proven effectiveness, epilepsy surgery continues to be underutilized, but new tools for health professionals are emerging to guide appropriate surgical referrals. Important contributions to the field of epilepsy surgery are discussed, in particular emerging imaging (fMRI) and neurophysiological (high-frequency oscillations) techniques. Epilepsy surgery is effective, well tolerated but still underutilized.

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 12years 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 3.14years, and mean age at surgery was 11.23years. 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.

Excellent outcomes after extratemporal epilepsy surgery in children

This commentary is on the original article by D’Argenzio et al. on pages 995‐1000 of this issue.

Feasibility of antiepileptic drug withdrawal following extratemporal resective epilepsy surgery

To identify the rate of successful antiepileptic drug (AED) withdrawal after resective surgery and the predictors of postwithdrawal seizure recurrence in patients with extratemporal epilepsy. We retrospectively analyzed the postoperative AED profile of 106 consecutive patients who had completed 2 or more years after resections involving frontal, parietal, and occipital lobes for AED-resistant epilepsy. To identify the potential predictors of seizure recurrence, we compared the attributes of recurred and nonrecurred groups by univariate and multivariate analyses. We attempted AED withdrawal in 94 (88.7%) patients. Forty-four (41.5%) patients had seizure recurrence while reducing AED, of which 14 (31.8%) did not become seizure-free subsequently. On multivariate analysis, an abnormal postoperative EEG and longer preoperative duration of epilepsy predicted seizure recurrence, while early postoperative seizures and presence of gliosis or dysplasia were additional predictors on univariate analysis. At mean follow-up duration of 4.6 years, 63 (59.4%) patients were seizure-free. The cumulative probability of achieving complete AED-free status was 20% at fourth year, 34% at sixth year, 40% at eighth year, and 52% at 10th year after surgery. Following resective extratemporal epilepsy surgery, AED can be successfully discontinued in only in a minority of patients. One-third of patients who recur fail to regain seizure control upon AED reintroduction. Longer duration of epilepsy prior to surgery, abnormal postoperative EEG, early postoperative seizures, and focal gliosis or dysplasia as substrate predispose to seizure recurrence. This information will be helpful in making rational decisions on AED withdrawal following extratemporal resective epilepsy surgery.

Seizure outcome after extratemporal epilepsy surgery in childhood

The aim of the study was to describe seizure outcome following surgery for focal extratemporal epilepsy and identify factors associated with prolonged postsurgical freedom from seizures. In this retrospective cohort study, children with drug-resistant focal extratemporal epilepsy were treated surgically and followed up in a single tertiary care centre between 1997 and 2008. Eighty children were identified for inclusion in the study (42 males, 38 females; median age 9y 1mo, range 3mo-18y 7mo). The aetiology was identified as focal cortical dysplasia (n=37), low-grade tumour (n=22), tuberous sclerosis (n=9), or non-specific (n=12). Children were followed for a median of 3 years 1 month (range 8mo-10y 7mo) after surgery. Overall, at last follow-up, 50% of the children had been completely seizure free since surgery (Engel class Ia); of these 40 individuals, 15 had discontinued all antiepileptic drugs. Several presurgical factors were associated with a favourable outcome. However, after controlling for confounding factors, aetiology appeared to be the only determinant of long-term seizure outcome as non-specific lesion pathology was associated with seizure recurrence (hazard ratio 10.43; 95% confidence interval 3.26-33.39). In 50% of cases, children with surgically treated drug-resistant extratemporal epilepsies have an excellent long-term outcome. The aetiology of the epileptogenic lesion appears to be the only significant determinant of surgical outcome in this population of children. It is difficult to correctly identify non-specific pathology on presurgical magnetic resonance imaging.

Prognostic significance of serial postoperative EEG in extratemporal lobe epilepsy surgery

ObjectiveTo assess the prognostic value of postoperative EEG in patients surgically treated for drug-resistant extra-temporal lobe (ET) epilepsy. MethodsWe studied 63 consecutive patients with ET epilepsy who underwent epilepsy surgery and were followed up for at least 2years (mean duration of follow-up 6.2±2.3years, range 2–12). Follow-up evaluations were performed 2, 12, and 24months after surgery, and included standard EEG (at 2months) and long-term video-EEG monitoring during both wakefulness and sleep (at 12 and 24months). Seizure outcome was determined at each follow-up evaluation, and then at yearly intervals. Patients who were in Engel Class I at the last contact were classified as having a good outcome. ResultsSeizure outcome was good in 39 patients (62%). The presence of interictal epileptiform discharges (IED) in postoperative EEG at each time point was found to be associated with poor outcome. The strength of this association was greater for awake plus sleep recording as compared with awake recording alone. In a multiple regression model including all pre- and post-operative factors identified as predictors of outcome in univariate analysis, the presence of early (2months after surgery) EEG epileptiform abnormalities was found to be independently associated with poor seizure outcome. ConclusionsPostoperative IED may predict long-term outcome in patients undergoing resective surgery for ET epilepsy. SignificanceThe increase in risk of unfavourable outcome associated with EEG epileptiform abnormalities detected as early as two months after surgery may have substantial practical importance. Serial postoperative EEGs including sleep recording may add further predictive power and help making decision about antiepileptic drug discontinuation.

An audit of the presurgical evaluation and patient selection for extratemporal resective epilepsy surgery in a resource-poor country

PurposeThe selection of ideal candidates for extratemporal resective epilepsy surgery is a challenge in resource-poor countries because of the limited presurgical diagnostic facilities and their affordability. To audit the presurgical evaluation strategy and selection for extratemporal resective epilepsy surgery in a resource-poor region. MethodsFrom the prospective database maintained at an epilepsy surgery center in southern India, we reviewed the data of consecutive patients who underwent presurgical evaluation from January 2005 through December 2008 for antiepileptic drug-resistant focal epilepsies emanating from the frontal, parietal and occipital lobes. Out of 285 patients, only 71 (24.9%) underwent resective surgery; the remaining 214 (75.1%) patients could not be selected for surgery. We inquired the reasons for their exclusion from surgery. ResultsThe difference in the rates of seizure-free outcome between surgical and non-surgical groups was highly significant (73.2% vs. 7.7%, P<0.0005). The major reasons for exclusion from surgery were normal MRI in 107 (50%), inability to afford invasive EEG monitoring in 40 (18.7%) and lesion location adjacent to eloquent cortical areas in 27 (12.6%) patients. While clustering of seizures and presence of preoperative neurological deficits favored surgical selection, the presence of secondary generalized seizures and discordant interictal epileptiform abnormalities were associated with exclusion from surgery. ConclusionsWe conclude that, in a resource-poor country, ideal candidates for extratemporal resective epilepsy surgery are those with well-circumscribed lesions not adjoining eloquent cortical areas. In such patients, concordant EEG findings and absence of preoperative secondary generalized seizures reinforce selection for surgery.