Focal cortical dysplasias in temporal lobe epilepsy surgery: Challenge in defining unusual variants according to the last ILAE classification

ObjectiveFocal cortical dysplasias (FCDs) represent a common architectural cortical disorder underlying pharmacoresistant focal epilepsy. The recent ILAE classification defines different types of FCDs based on their histopathological features, MRI imaging, and presumed pathogenesis; however, their clinical features and their prognostic significance are still incompletely defined. In addition, the combination of different histopathological abnormalities can represent “unusual” subtypes that can be difficult to classify. The aim of our study was to analyze the incidence and the significance of these “unusual” subtypes of FCDs in drug-resistant mesial temporal lobe epilepsy (MTLE).MethodsWe retrospectively analyzed 133 patients consecutively submitted to tailored anteromesial temporal lobe resection for pharmacoresistant MTLE. Seizure onset, seizure duration, age at surgery, and postoperative seizure outcome were evaluated in relation to the different neuropathological groups defined according to the new ILAE classification.ResultsFocal cortical dysplasias were found in 80 out of 133 patients. Six patients were affected by isolated FCD type I, 12 patients by FCD type II, and 44 patients by FCD type III. Furthermore, we found 18 “atypical” cases (20.5% of all FCD cases and 26.6% of FCDs associated with a principal lesion): 10 cases of associated FCD type II–hippocampal sclerosis (HS) and 8 cases associated with FCD II–epilepsy-associated tumors (EATs).ConclusionOur results indicate that “unusual” subtypes of FCDs, in particular associated FCD type II, are not uncommon findings, suggesting that they deserve a classification recognition. Similarities in seizure outcome and immunohistochemical and molecular evidences, shared by FCD type II + EATs and EATs, suggest a common pathogenic link. The choice to create a specific unifying class or, on the contrary, to also include “associated FCD type II” in the definition of the new unifying class FCD type III should be further discussed.     

Different presurgical characteristics and seizure outcomes in children with focal cortical dysplasia type I or II

Purpose:   Cortical dysplasia (FCD) is a frequent cause of epilepsy in childhood. Two major pathological variants are distinguished, FCD type I and II. The aim of the study was to characterize differences between FCD type I and II with respect to imaging and EEG findings, clinical and neuropsychological presentations, and surgical outcome.
Methods:   Forty children with refractory epilepsy and histopathologically confirmed FCD were retrospectively analyzed. FCD type I was identified in 24 and FCD type II in 16 patients.
Results:   Characteristic MRI abnormalities in FCD type I included subtle white matter signal changes and regional reduction of the white matter volume. Typical MRI findings in FCD type II were increased cortical thickness, transmantle sign, gray-white matter junction blurring, fluid-attenuated inversion recovery (FLAIR) and proton density (PD) gray matter signal changes as well as T1w, and PD white matter signal changes. Continuous EEG slowing was significantly more common in patients with FCD type I. Children with FCD type I presented with lower levels of intelligence and were suffering more often from maladaptive behavior and behavioral disorders. Surgical outcome was significantly worse in the FCD type I group (seizure freedom was achieved in 21% FCD type I patients and in 75% FCD type II subjects, p < 0.001).
Conclusions:   Clinically important differences were found in children with distinct histopathological subtypes of FCD. Due to prominent neuropsychological deficits and worse seizure outcome, treatment strategies in FCD type I are more challenging than previously reported and these children should be recognized and specifically addressed within the incoherent group of patients with malformative brain disorders.     

Electro- and magneto-encephalographic spike source localization of small focal cortical dysplasia in the dorsal peri-rolandic region

ObjectiveSmall focal cortical dysplasia (FCD) may be ambiguous or overlooked on magnetic resonance (MR) imaging. Source localization of EEG and magnetoencephalography (MEG) spikes was evaluated to confirm the diagnosis of small FCD.MethodsThis study included 6 epilepsy patients with a single small lesion on MR imaging suggesting FCD within a single gyrus among 181 consecutive epilepsy patients admitted to our epilepsy monitoring unit over 27 months. Stereotypical interictal spikes were detected on simultaneous EEG and MEG recordings and the onset-related source of averaged spikes was estimated.ResultsAll 6 patients had unique clinical characteristics as follows: leg sensori-motor seizures in 5 patients and eye version in 1 patient; a small MR imaging lesion suggesting FCD in the dorsal peri-rolandic region, which had been overlooked until our evaluation; and both EEG and MEG dipoles were estimated adjacent to the MR imaging lesion.ConclusionsSource localization of EEG and MEG spikes can confirm the diagnosis of FCD based on a single small MR imaging lesion, which was overlooked by previous examination of MR images.SignificanceExamination of MR images should be based on spike source localization as well as seizure semiology to identify subtle MR imaging abnormalities.     

Dysembryoplastic neuroepithelial tumors: Epileptogenicity related to histologic subtypes

ObjectiveTo analyze the electroclinical features and the relationship between the epileptogenic zone (EZ), the tumor and focal cortical dysplasia (FCD) in the three histologic subtypes of dysembryoplastic neuroepithelial tumors (DNTs) (“simple”, “complex” and “non-specific forms”).MethodsWe analyzed electroclinical data from 78 patients (50 males; 3–54 years) operated for intractable epilepsy due to a DNT. We compared EZ extent, defined by stereo-electroencephalography (n = 33), with the tumor and FCD areas, in each DNT subtype.ResultsNon-specific forms (68%) and temporal location were predominant (73%). The main characteristics consisted of late childhood epilepsy onset (median 12 years), drug-resistant partial seizures and EEG abnormalities concordant with tumor location. In all DNT subtypes, intrinsic epileptogenicity was demonstrated by intralesional recordings (n = 30), displaying a depressed background activity interrupted by rapid spikes or polyspikes. EZ co-localized with the tumor in all simple and complex DNTs, but in only 1/3 of non-specific DNTs. The main discordance between the EZ and tumor extent was found in temporal non-specific DNTs associated with extensive FCD.ConclusionThese results are helpful when planning surgery for DNTs.SignificanceIntrinsic epileptogenicity characterizes all DNTs; however, the EZ differs according to histologic subtypes and is particularly widespread in non-specific temporal forms.     

Neuroimaging in identifying focal cortical dysplasia and prognostic factors in pediatric and adolescent epilepsy surgery

Purpose: The purpose of this study is to determine the sensibility of each imaging tool in identifying focal cortical dysplasia (FCD) in children and adolescents with epilepsy and to define the prognostic factors of pediatric and adolescent epilepsy surgery. Methods: We identified 48 children with FCD who underwent resective surgery and analyzed their preoperative data. The results of various anatomic and functional neuroimaging studies were compared for accuracy in locating the lesion. We also investigated clinical factors that affected the outcome of surgical treatment. Key Findings: Brain magnetic resonance imaging (MRI) was able to localize FCD in 30 patients and fluorodeoxyglucose positron emission tomography (FDG‐PET) and/or subtraction ictal single photon emission computed tomography (SPECT) coregistered with MRI provided additional information that helped to define the lesion in 13 patients. When comparing the pathologic results between a mild malformation of cortical development (MCD) and FCD type I and II, we noted a strong tendency for patients with FCD to have MRI abnormalities (p = 0.005). In addition, severe pathologic features (Palmini’s classification, FCD type II) (p = 0.025) showed significant correlation with a better surgical outcome. To define the primary epileptogenic area, various interictal epileptiform discharges and the results of multimodal neuroimaging studies were helpful, and younger age at the time of operation could aid in more favorable surgical outcomes (p = 0.048). Significance: Our study showed a significant relationship between pathologic grade and the detectability of FCD by brain MRI. In addition, early surgery can be justified by showing that advanced neuroimaging studies in children with FCD and even with extensive epileptiform discharges have a higher rate of success.     

Patient satisfaction with temporal lobectomy/selective amygdalohippocampectomy for temporal lobe epilepsy and its relationship with Engel classification and the side of lobectomy

PurposeThe aim of this study was to investigate not only the effectiveness of epilepsy surgery in improving seizure control but also patient satisfaction with the result of the procedure in a sample of patients operated on at a specialized epilepsy unit.MethodsPatients with temporal lobe epilepsy who had undergone epilepsy surgery (temporal lobectomy/amygdalohippocampectomy) were interviewed in a standardized telephone survey about their satisfaction with the results of the surgery. The morbidity of the surgery was also analyzed retrospectively. The initial study population consisted of 6 amygdalohippocampectomy and 102 temporal lobectomy patients and was reduced to a final sample consisting of 4 amygdalohippocampectomy and 67 lobectomy patients, as the other patients were not available for interview. Surgical results were based on the Engel classification, and satisfaction with the surgery was assessed by asking patients to rate their result and state whether they would make the same decision (to be operated on) again.ResultsA significant number of patients classified as Engel I or II, who considered the surgical outcome good or excellent, said they would have the surgery again (p < 0.001). Left temporal lobectomy patients whose results fell in the Engel III/IV bracket were less satisfied (p = 0.001) than right temporal lobectomy patients with the same Engel classifications (0.048). Left temporal lobectomy patients who were classified as Engel class III and IV were less likely to have the surgery again if they had the choice (p = 0.016).DiscussionPatient satisfaction with the results of epilepsy surgery may depend not only on achieving seizure control but also on the temporal lobe resected. Since worse results were associated with lower satisfaction rates only for left temporal resection patients, it is possible that the cognitive consequences of this procedure compound the worse surgical result, leading to decreased satisfaction.     

The evaluation of interictal focal EEG findings in adult patients with absence seizures

PurposeTo investigate the focal interictal EEG abnormalities in adult patients with absence seizures (ASs) and to identify their clinical, EEG and semiological correlates.MethodsFifty patients older than 18 years, diagnosed as having IGE with AS documented with ictal recordings. Interictal focal sharp or spike–waves and strictly focal paroxysmal slow activity were considered as focal EEG features. The patients having focal EEG features were classified as “Group I”, whereas the remaining of them was classified as “Group II”.ResultsWe observed focal findings in 34% of the patients, mainly in frontotemporal (41%), and frontal (29%) regions. There were no significant differences with respect to the clinical parameters such as sex, epilepsy duration, positive family history and the age of the onset between the groups. Psychiatric co-morbidities were significantly higher in Group I when compared to Group II (P = 0.00). Accompanying automatisms were higher in Group I, whereas eye deviation during absences was higher in Group II. In Group I, the asymmetry of the ictal discharges was more frequently observed. Focal EEG features were more frequently seen in juvenile absence epilepsy syndrome, without reaching a significance level.ConclusionThe focal findings in adult absence epilepsy patients could have some unknown etio-pathogenetic and prognostic implications. We emphasize the cautious interpretation of isolated interictal focal EEG abnormalities to prevent a wrong diagnosis of focal epilepsy in patients who may indeed suffer from generalized epilepsy.     

Comprehensive preoperative work-up and surgical treatment of low grade tumor/benign lesion related temporal lobe epilepsy

ObjectiveGenerally low-grade tumor/benign lesion related temporal lobe epilepsy (LGT/BL-TLE) is considered easier to treat and has better prognosis when compared to non-lesional TLE. However, multiple disputes exist in surgical management of this epilepsy entity. This study aims to discuss comprehensive preoperative work-up, surgical strategies and outcome of it.MethodsA retrospective review of sixty LGT/BL-TLE cases which underwent comprehensive preoperative work-up and then resective surgeries was conducted. Surgical strategies were categorized into limited and expanded resections. Surgical efficacy was evaluated using Engel grading after telephone or clinic follow-up and compared statistically.ResultsPreoperative work-up includes magnetic resonance imaging (MRI), conventional electroencephalography, semiology evaluation, positron emission tomography (PET) and 256-channel dense-array electroencephalography source imaging (256-ch dESI). In aspect of concordance with epileptic lesions demonstrated on MRI, 256-ch dESI was more accurate than PET (72.7% vs. 39.4%) (p < 0.05). Limited resections were performed in 28 cases while expanded resections in 32 cases. Altogether the surgical efficacy was: Engel grade I 86.7%, I + II 95.0%. Comparison of surgical outcome showed neither the outcome between limited and expanded resection nor the outcome between mesial and neocortical TLE (mTLE & nTLE) undergoing limited resections was significantly different (p > 0.05).ConclusionsFor LGT/BL-TLE, most surgical strategies can be made preoperatively after comprehensive work-up rather than intraoperatively. Limited and expanded strategies yield similar surgical outcome in either nTLE or mTLE as long as comprehensive work-up supports the strategy and the epileptic lesion is totally removed. 256-ch dESI which can visualize both structural and electrophysiological lesions may be contributable to surgical planning of this entity.     

Clinical characteristics and post-surgical outcomes of focal cortical dysplasia subtypes

We retrospectively studied 105 patients with a focal cortical dysplasia (FCD) diagnosed on pathological examination, and investigated the long term postoperative seizure outcomes, different clinical characteristics of the three FCD subtypes, particularly type I and II, and surgical outcomes for each group. FCD is a common cause of drug-resistant epilepsy, which is divided into three different subtypes according to its involvement at different stages of brain development. Each of these groups may have different characteristics and may even have different surgical outcomes. After treatment, 55% of patients were completely seizure-free, with two significant predictive variables for poorer outcomes: focal MRI findings and electrode implantation. FCD type I had relatively poor surgical outcomes compared to FCD type II and type IIIa. Compared with FCD type I, type II, particularly IIb, had a higher frequency of seizure attacks, predominantly located in the extratemporal lobes, and was more readily detected and diagnosed via focal lesions on MRI and localized electroencephalogram abnormalities. FCD type II patients seem to show better surgical outcomes than FCD type I, but the difference was not significant. Larger cohort studies are needed for further evaluation of the seizure outcomes of different FCD subtypes.     

Semiology of hypermotor (hyperkinetic) seizures

BackgroundHypermotor seizures (HMSs) consist of complex movements involving proximal segments of the limbs and trunk that appear violent and inappropriate for the situation.MethodsWe analyzed hypermotor seizure videos in seizure-free patients (Engel class I) following resective epilepsy surgery. After completion of video analysis, we reviewed EEG and neuroimaging data.ResultsSearch of our epilepsy surgery database yielded 116 patients classified as having hypermotor seizures between 1996 and 2013. From this subset, 17/31 (55%) patients had been seizure-free for > 6 months (mean follow-up: 3.3 years). Mean seizure duration was 35 s (range: 6–91 s), of which the HM phase lasted a mean of 22 s (range: 3–53 s). In 16 patients (95%), hypermotor activity was seen at or within 10 s of clinical seizure onset.Type I semiology occurred in 6 patients, type II semiology in 10 patients, and 1 patient exhibited features of both. Type I and type II semiologies were noted in patients who had frontal lobe as well as extrafrontal resections. Nonversive head and body turning occurred in 10 patients (ranging from 90° to 270°) which was ipsilateral to the side of resection in all patients and seen both in frontal and extrafrontal resections. Six out of eleven patients with abnormal MRI and 4/6 patients with nonlesional MRI underwent invasive EEG evaluation. Eight patients (47%) had frontal lobe resection, 4/17 (23%) patients had temporal lobe resection, and one patient each had parietal lobe, insular, temporoparietooccipital, or motor sparing resection; 1 patient had functional hemispherectomy.ConclusionHypermotor semiology typically occurs at or within 10 s after seizure onset. Ipsilateral head/body turning appears to be of lateralizing value whereas asymmetry of limb movement was not lateralizing. Hypermotor semiology is most often seen in frontal lobe epilepsy but may occur in seizures arising from other locations.     

Seizure outcome after AED failure in pediatric focal epilepsy: Impact of underlying etiology

ObjectiveThis study aimed to identify long-term seizure outcome in pediatric nonsyndromic focal epilepsy after failure of serial antiepileptic drugs (AEDs) due to lack of efficacy.MethodsChildren (1 month–17 years) with new-onset focal epilepsy not meeting the criteria for a defined electroclinical syndrome diagnosed between 1980 and 2009 while residing in Olmsted County, MN, were retrospectively identified. Medical records of those followed for ≥ 2 years were reviewed to assess etiology, the number of AEDs that failed due to lack of efficacy, and seizure outcome at final follow-up. Etiology was classified into structural/metabolic, genetic, or unknown. Favorable outcome was defined as seizure freedom ≥ 1 year, on or off AEDs, without prior epilepsy surgery. Poor outcome was defined as ongoing seizures in the preceding year or having undergone prior epilepsy surgery.ResultsNonsyndromic focal epilepsy accounted for 275/468 (59%) of all patients with newly diagnosed epilepsy — of these, 256 (93%) were followed for a minimum of two years and were included in the study. Median duration of follow-up was 10.0 years. At least one AED had failed due to lack of efficacy in 100 (39.1%) children. Favorable outcomes occurred in 149/156 (95.5%) children with no AED failure, 16/30 (53.3%) with one AED failure, 8/25 (32%) with two AED failures, and only 2/45 (4.4%) with three AED failures. After two AED failures, the seizures of nearly one-quarter of children who had epilepsy with an unknown cause responded favorably to the third AED compared with only 7.8% of the cohort that had epilepsy with a structural/metabolic cause. Children with a remote brain insult had a significantly higher likelihood of favorable outcome with serial AEDs than those with other structural abnormalities.SignificanceEtiology is an important determinant of pharmacoresistance in nonsyndromic focal epilepsy. Surgical evaluation should be considered after failure of 1–2 AEDs in those who have epilepsy with structural causes, excluding remote brain insults. Conversely, as surgical success is lower with normal MRI or more diffuse brain insults, it appears reasonable to hold off surgical evaluation until 2–3 AEDs have failed in such children.     

The impact of stereotactic laser ablation at a typical epilepsy center

PurposeStereotactic laser ablation (SLA) is a novel form of epilepsy surgery for patients with drug-resistant focal epilepsy. We evaluated one hundred consecutive surgeries performed for patients with epilepsy to address the impact of SLA on our therapeutic approach, as well as patient outcomes.MethodsA retrospective, single center analysis of the last one hundred neurosurgeries for epilepsy was performed from 2013 to 2015. Demographics, surgical procedures, and postoperative measures were assessed up to 5 years to compare the effect of SLA on outcome. Confidence intervals (CI) and comparative tests of proportions compared outcomes for SLA and resective surgery. Procedural categorical comparison used Chi-square and Kaplan–Meier curves. Student t-test was utilized for single variables such as age at procedure and seizure onset.ResultsOne hundred surgeries for epilepsy yielded thirty-three SLAs and twenty-one resections with a mean of 21.7-month and 21.3-month follow-up, respectively. The temporal lobe was the most common target for SLA (92.6%) and resection (75%). A discrete lesion was present on brain magnetic resonance imaging (MRI) in 27/32 (84.4%) of SLA patients compared with 7/20 (35%) of resection patients with a normal MRI. Overall, 55–60% of patients became seizure-free (SF). Four of five patients with initial failure to SLA became SF with subsequent resection surgery. Complications were more frequent with resection although SF outcomes did not differ (Chi square; p = 0.79). Stereotactic laser ablation patients were older than those with resections (47.0 years vs. 35.4 years, p = 0.001). The mean length of hospitalization prior to discharge was shorter for SLA (1.18 days) compared with open resection (3.43 days; SD: 3.16 days) (p = 0.0002).ConclusionWe now use SLA as a first line therapy at our center in patients with lesional temporal lobe epilepsy (TLE) before resection. Seizure-free outcome with SLA and resection was similar but with a shorter length of stay. Long-term follow-up is recommended to determine sustained SF status from SLA.     

脑皮质发育不良继发顽固性癫痫的病理分型及手术治疗

目的 探讨局灶性脑发育不良(FCD)的临床特征、病理学、影像学的特点及手术疗效.方法 42例外科手术切除致痫灶并经病理证实为FCD的患者中,根据Palmini病理学分型进行分类,并对其临床特征、影像学特点及手术疗效进行回顾性分析.结果 42例患者中,按致痫灶部位分类颢叶24例、额叶14例、顶叶6例及枕叶3例,其中多脑叶5例.术前影像学检查阳性率62%.组织学分型FCDⅠA型9例,FCDⅠB型21例,FCDⅡA型5例,FCDⅡB型7例,其中以FCD Ⅰ B型最为常见,多位于颞叶且常伴有海马硬化.所有患者术后至少随访1年以上,癫痫术后治愈率FCD位于颞叶67%,颞叶以外43%(EngleⅠa).结论 FCD是难治性癫痫常见的病理学改变,其病理分型与临床特征和致痫灶部位存在相关性,为制定手术方案和判定手术效果提供了依据.     

Quality control of elective surgery for drug-resistant epilepsy in a German reference centre—A long-term outcome study

PurposeResective epilepsy surgery is the recommended treatment for a well-defined group of patients with drug-resistant epilepsy. Long-term outcome studies are an appropriate quality control to assess the value of elective surgical procedures ethically and economically. This paper reports the long-term post-surgical follow-up of adult patients of the Kork Epilepsy Centre.MethodData collection was performed by means of a questionnaire to obtain updated information about postsurgical outcome, frequency and postsurgical seizure semiology in case of relapse, postsurgical use of antiepileptic drugs, social issues and satisfaction rates. We classified seizure outcome according to the ILAE surgery outcome scale (OC 1–OC 6).ResultsOutcome data of 340 adult patients were obtained. Mean post-operative follow-up was 6.7 years (range 1.0–21.6 years). Seizure remission was 67% if comprising patients with postoperative auras only (OC 1 + OC 2). Sixty-two per cent of patients were completely seizure free. The majority of patients (78%) underwent temporal lobe resections. Sixty-four per cent of these and 52% of the patients with extra-temporal resections became completely seizure-free (OC 1). Only 34% of the patients with negative MRI achieved complete seizure-freedom.ConclusionIn line with others our huge cohort sample that covers decades of experience with epilepsy surgery revealed satisfying long-term outcome results. Best results were obtained in lesional temporal lobe epilepsy, least favourable results in MRI-negative epilepsy.     

Mesio-temporal ictal semiology as an indicator for surgical treatment of epilepsies with large multilobar cerebral lesions

PurposeMesio-temporal ictal semiology is sometimes observed in patients with large multilobar lesion. In this situation, surgery is often discarded because of the lesion size and/or suspicion of extended or multifocal epileptogenic areas. In this retrospective study we evaluated the surgical outcome of such patients in order to assess whether the electro-clinical presentation of seizures could be a prognostic marker of surgical outcome.MethodsAmong the temporal lobe epilepsy population explored in our department between 2000 and 2011 (240 patients), we identified 7 patients who presented an extensive lesion on brain Magnetic Resonance Imaging (MRI) (multilobar in four, hemispheric in two, and bilateral in one). All patients underwent ¹⁸Fluorodeoxyglucose Positron Emission Tomography, which showed large, hemispheric or multilobar, areas of glucose hypometabolism. Because of the large lesion size, all patients were explored by stereoelectroencephalography (SEEG) before taking a decision regarding surgical indication.ResultsSEEG confirmed the temporal origin of the seizures and discarded the possibility of multiple epileptogenic zones. A temporal lobectomy, tailored on the basis of SEEG data, was proposed to the seven patients. The seven patients are classified Engel class I after the surgery (mean follow-up: 37.4 ± 22.1 months).ConclusionOur data thus suggest that, even in the absence of hippocampal MRI abnormality, ictal symptoms compatible with a temporal origin of seizures should be considered as a reliable indicator for surgery eligibility regardless of MRI lesion size. On the basis of our findings, the mesio-temporal semiology of seizures appears as one of the most reliable markers of operability in patients with large MRI lesions. These patients should not be excluded a priori from invasive exploration and surgical treatment, even if a large portion of their lesion is likely to be left in place after surgery.     

Long-term outcome and predictors of resective surgery prognosis in patients with refractory extratemporal epilepsy

PurposeWe analyzed the long-term postoperative outcome and possible predictive factors of the outcome in surgically treated patients with refractory extratemporal epilepsy.MethodsWe retrospectively analyzed 73 patients who had undergone resective surgery at the Epilepsy Center Brno between 1995 and 2010 and who had reached at least 1 year outcome after the surgery. The average age at surgery was 28.3 ± 11.4 years. Magnetic resonance imaging (MRI) did not reveal any lesion in 24 patients (32.9%). Surgical outcome was assessed annually using Engel's modified classification until 5 years after surgery and at the latest follow-up visit.ResultsFollowing the surgery, Engel Class I outcome was found in 52.1% of patients after 1 year, in 55.0% after 5 years, and in 50.7% at the last follow-up visit (average 6.15 ± 3.84 years). Of the patients who reached the 5-year follow-up visit (average of the last follow-up 9.23 years), 37.5% were classified as Engel IA at each follow-up visit. Tumorous etiology and lesions seen in preoperative MRI were associated with significantly better outcome (p = 0.035; p < 0.01). Postoperatively, 9.6% patients had permanent neurological deficits.ConclusionSurgical treatment of refractory extratemporal epilepsy is an effective procedure. The presence of a visible MRI-detected lesion and tumorous etiology is associated with significantly better outcome than the absence of MRI-detected lesion or other etiology.     

Prognostic significance of acute postoperative seizures in extra-temporal lobe epilepsy surgery

ObjectiveThis study aims to assess the prognostic value of acute postoperative seizures (APOS) in patients surgically treated for drug-resistant extra-temporal lobe (ET) epilepsy.MethodsWe studied 77 consecutive patients with ET epilepsy who underwent epilepsy surgery and were followed up for at least 2 years (mean duration of follow-up 6.2 years, range 2–14). Medical charts were reviewed to identify APOS, defined as ictal events with the exception of auras occurring within the first 7 days after surgery. Seizure outcome was determined at annual intervals. Patients who were in Engel Class I at the last contact were classified as having a favourable outcome.ResultsSeizure outcome was favourable in 47 patients (61%). The occurrence of APOS and incompleteness of resection were found to be independently associated with unfavourable outcome in a multiple regression model including all preoperative factors identified as outcome predictors in univariate analysis. Duration of illness was the only independent preoperative predictor of APOS.ConclusionsOur study suggests that APOS may predict long-term outcome in patients undergoing resective surgery for ET epilepsy. Given some study limitations, our findings should be regarded as preliminary and need confirmation from future larger, prospective, multicentre studies.SignificanceCaution may be required in the clinical management of patients experiencing APOS.     

Long-term postoperative atrophy of contralateral hippocampus and cognitive function in unilateral refractory MTLE with unilateral hippocampal sclerosis

ObjectiveThis study aimed to evaluate long-term atrophy in contralateral hippocampal volume after surgery for unilateral MTLE, as well as the cognitive outcome for patients submitted to either selective transsylvian amygdalohippocampectomy (SelAH) or anterior temporal lobe resection (ATL).MethodsWe performed a longitudinal study of 47 patients with MRI signs of unilateral hippocampal sclerosis (23 patients with right-sided hippocampal sclerosis) who underwent surgical treatment for MTLE. They underwent preoperative/postoperative high-resolution MRI as well as neuropsychological assessment for memory and estimated IQ. To investigate possible changes in the contralateral hippocampus of patients, we included 28 controls who underwent two MRIs at long-term intervals.ResultsThe volumetry using preoperative MRI showed significant hippocampal atrophy ipsilateral to the side of surgery when compared with controls (p < 0.0001) but no differences in contralateral hippocampal volumes. The mean postoperative follow-up was 8.7 years (± 2.5 SD; median = 8.0). Our patients were classified as Engel I (80%), Engel II (18.2%), and Engel III (1.8%). We observed a small but significant reduction in the contralateral hippocampus of patients but no volume changes in controls. Most of the patients presented small declines in both estimated IQ and memory, which were more pronounced in patients with left TLE and in those with persistent seizures. Different surgical approaches did not impose differences in seizure control or in cognitive outcome.ConclusionsWe observed small declines in cognitive scores with most of these patients, which were worse in patients with left-sided resection and in those who continued to suffer from postoperative seizures. We also demonstrated that manual volumetry can reveal a reduction in volume in the contralateral hippocampus, although this change was mild and could not be detected by visual analysis. These new findings suggest that dynamic processes continue to act after the removal of the hippocampus, and further studies with larger groups may help in understanding the underlying mechanisms.     

Visual and semiautomated evaluation of epileptogenicity in focal cortical dysplasias — An intracranial EEG study

IntroductionThe aim of the study was the evaluation of the added value of depth to subdural electrodes in delineating epileptogenicity of focal cortical dysplasias (FCDs) and to test the Epileptogenicity Index (EI) in this setting.Material and methodsFifteen patients with FCD underwent iEEG with subdural and depth electrodes. Visual/EI analysis was performed in up to three habitual seizures per patient.ResultsVisual analysis: Grid onset seizures (n = 10) started in electrodes overlying the lesion in 7 and remote from it in 3 cases. Depth onset seizures (n = 7) affected only intralesional contacts in 4, intra- and extralesional in 2, and exclusively extralesional in 1 patient. Seizures started in depth and grid contacts simultaneously in 2 cases.EI analysis: The EI completely confirmed visual localization of seizure onset in 8 cases and depicted ictal onset-time accurately in 13. Beta/gamma ictal patterns were most reliably captured.Impact on surgical decision: Resection outline differed from MRI lesion in 7 patients based on grid and in three based on depth electrode information.DiscussionIn FCD, seizures can be generated within gyral/deep tissue appearing normal on imaging.ConclusionInvestigating FCD with subdural and depth electrodes is efficient to outline the seizure onset zone. The EI is a helpful additional tool to quantify epileptogenicity. Specific ictal patterns are prerequisite for reliable results.