Predictors of surgical outcome and pathologic considerations in focal cortical dysplasia

Who are the Better Candidates for Epilepsy Surgery?

The resective epilepsy surgery can be the effective procedure to get seizure-free outcome in these drug resistant epilepsy (DRE) patients. Class I evidence firmly establishes the superiority of epilepsy surgery over medical treatments in both seizure control and quality of life for DRE patients. For the effective identification of optimal surgical candidates, it's essential to understand the prognostic factors of epilepsy surgery based on the surgical methods employed. Established positive prognostic indicators for temporal resection include the presence of hippocampal sclerosis on magnetic resonance imaging (MRI), focal lesions on MRI, unilateral temporal spikes, concordant ictal electroencephalography (EEG), and a history of prolonged febrile convulsion. Potential negative predictors encompass preoperative secondary generalized tonic-clonic seizures, a normal MRI, postoperative EEG spikes, and age at the time of surgery. For neocortical epilepsy, the prognostic factors identified through multivariate analysis were the presence of a discrete lesion, localized hypometabolism on Fluorodeoxyglucose positron emission tomography (FDG-PET), and localized ictal EEG. A significant correlation was found between achieving a seizure-free outcome in no visible lesion on MRI (MR-negative) epilepsy patients and having concordance in two or more presurgical evaluations, specifically in interictal EEG, ictal EEG, FDG-PET, and ictal single-photon emission computed tomography. There was a marked improvement in the seizure-free outcome in MR-negative temporal lobe epilepsy (TLE) by the application of this strategy. The better surgical candidates for epilepsy surgery are the followings: patients displaying a discrete lesion on MRI with concordant video-EEG monitoring (VEM) results, patients diagnosed with unilateral hippocampal sclerosis who have concordant VEM results, patients with unilateral hippocampal sclerosis but discordant VEM results, patients with focal cortical dysplasia and concordant VEM results, and patients diagnosed with MR-negative TLE who exhibit two or more consistent results from presurgical evaluations.

Interictal high-frequency oscillations, spikes, and connectivity profiles: A fingerprint of epileptogenic brain pathologies

OBJECTIVE

Focal cortical dysplasia (FCD), hippocampal sclerosis (HS), nonspecific gliosis (NG), and normal tissue (NT) comprise the majority of histopathological results of surgically treated drug-resistant epilepsy patients. Epileptic spikes, high-frequency oscillations (HFOs), and connectivity measures are valuable biomarkers of epileptogenicity. The question remains whether they could also be utilized for preresective differentiation of the underlying brain pathology. This study explored spikes and HFOs together with functional connectivity in various epileptogenic pathologies.

METHODS

Interictal awake stereoelectroencephalographic recordings of 33 patients with focal drug-resistant epilepsy with seizure-free postoperative outcomes were analyzed (15 FCD, 8 HS, 6 NT, and 4 NG). Interictal spikes and HFOs were automatically identified in the channels contained in the overlap of seizure onset zone and resected tissue. Functional connectivity measures (relative entropy, linear correlation, cross-correlation, and phase consistency) were computed for neighboring electrode pairs.

RESULTS

Statistically significant differences were found between the individual pathologies in HFO rates, spikes, and their characteristics, together with functional connectivity measures, with the highest values in the case of HS and NG/NT. A model to predict brain pathology based on all interictal measures achieved up to 84.0% prediction accuracy.

SIGNIFICANCE

The electrophysiological profile of the various epileptogenic lesions in epilepsy surgery patients was analyzed. Based on this profile, a predictive model was developed. This model offers excellent potential to identify the nature of the underlying lesion prior to resection. If validated, this model may be particularly valuable for counseling patients, as depending on the lesion type, different outcomes are achieved after epilepsy surgery.

WNT pathway in focal cortical dysplasia compared to perilesional nonlesional tissue in refractory epilepsies

BACKGROUND

Focal cortical dysplasia (FCD) is a malformation of cortical development that causes medical refractory seizures, and one of the main treatments may be surgical resection of the affected area of the brain. People affected by FCD may present with seizures of variable severity since childhood. Despite many medical treatments available, only surgery can offer cure. The pathophysiology of the disease is not yet understood; however, it is known that several gene alterations may play a role. The WNT/β-catenin pathway is closely related to the control and balance of cell proliferation and differentiation in the central nervous system. The aim of this study was to explore genes related to the WNT/β-catenin pathway in lesional and perilesional brain tissue in patients with FCD type II.

METHODS

Dysplastic and perilesional tissue from the primary dysplastic lesion of patients with FCD type IIa were obtained from two patients who underwent surgical treatment. The analysis of the relative expression of genes was performed by a qRT-PCR array (super array) containing 84 genes related to the WNT pathway.

RESULTS

Our results suggest the existence of molecular alteration in some genes of the WNT pathway in tissue with dysplastic lesions and of perilesional tissue. We call this tissue of normal-appearing adjacent cortex (NAAC). Of all genes analyzed, a large number of genes show similar behavior between injured, perilesional and control tissues. However, some genes have similar characteristics between the perilesional and lesional tissue and are different from the control brain tissue, presenting the perilesional tissue as a molecularly altered material.

CONCLUSION

Our results suggest that the perilesional area after surgical resection of tissue with cortical dysplasia presents molecular changes that may play a role in the recurrence of seizures in these patients. The perilesional tissue should receive expanded attention beyond the somatic mutations described and associated with FCD, such as mTOR, for example, to new signaling pathways that may play a crucial role in seizure recurrence.

Hypometabolic patterns of focal cortical dysplasia in PET-MRI co-registration imaging: a retrospective evaluation in a series of 83 patients

Objective

To characterize the PET-MRI co-registration of hypometabolic patterns in focal cortical dysplasia (FCD) types I and II and provide some suggestions in presurgical evaluation of epilepsy surgery.

Methods

We retrospectively analyzed PET-MRI co-registration imaging data from a cohort of 83 epilepsy patients with histologically confirmed FCD types I and II. Hypometabolic patterns were classified into 4 types: bottom of sulcus hypometabolism (BOSH), single island of sulcus hypometabolism (SIOS), single gyrus or sulcus hypometabolism (SGOS), and multiple gyri and sulci hypometabolism (MGOS).

Results

Most of cases that were overlooked by conventional MRI and PET evaluation but positive in PET-MRI co-registration were focalized lesions in dorsolateral frontal lobe (9/15) and FCD type IIa was the most prevalent pathological type (11/15). The FCD histological types (p = 0.027) and locations (p < 0.001) were independent predictors of PET-MRI co-registration hypometabolic patterns. Focalized hypometabolic patterns (BOSH, SIOS, SGOS) were primarily observed in the frontal lobe (33/39) and FCD type II (43/62) and extensive pattern (MGOS) in temporal lobe (18/20) and FCD type I (16/21; p < 0.005).

Conclusion

PET-MRI co-registration enhanced the detection of FCD type IIa compared with conventional MRI and PET reading. The hypometabolic patterns of FCD type I and temporal lobe FCD were more extensive than those of FCD type II and frontal lobe FCD, respectively. The predilection of focalized hypometabolic patterns in frontal lobe FCD suggested that subtle lesions should be checked carefully in patients with suspected frontal lobe epilepsy.

Lesion Detection Through MRI Postprocessing in Pathology-Proven Focal Cortical Dysplasia: Experience at a Single Institution in the Republic of Korea

BACKGROUND AND PURPOSE

Focal cortical dysplasia (FCD) is one of the most common causes of drug-resistant epilepsy, and necessitates a multimodal evaluation to ensure optimal surgical treatment. This study aimed to determine the supportive value of the morphometric analysis program (MAP) in detecting FCD using data from a single institution in Korea.

METHODS

To develop a standard reference for the MAP, normal-looking MRIs by two scanners that are frequently used in this center were chosen. Patients with drug-resistant epilepsy and FCD after surgery were candidates for the analysis. The three-dimensional T1-weighted MRI scans of the patients were analyzed as test cases using the MAP.

RESULTS

The MRI scans of 87 patients were included in the analysis. The radiologist detected abnormal findings correlated with FCD (RAD positive [RAD(+)]) in 34 cases (39.1%), while the MAP could detect FCD in 25.3% of cases. A combination of the MAP (MAP[+] cases) with interpretations by the radiologist increased the detection to 42.5% (37 cases). The lesion detection rate was not different according to the type of reference scanners except in one case. MAP(+)/RAD(-) presented in three cases, all of which had FCD type IIa. The detection rate was slightly higher using the same kind of scanner as a reference, but not significantly (35.0% vs. 22.4% p=0.26).

CONCLUSIONS

The results of postprocessing in the MAP for detecting FCD did not depend on the type of reference scanner, and the MAP was the strongest in detecting FCD IIa. We suggested that the MAP could be widely utilized without developing institutional standards and could become an effective tool for detecting FCD lesions.

Prevalence and Risk Factors for Pharmacoresistance in Children With Focal Cortical Dysplasia-Related Epilepsy

BACKGROUND AND OBJECTIVES

Focal cortical dysplasia (FCD) is the most common cause of surgically remediable epilepsy in children. Little is known about the risk factors for the timing and development of pharmacoresistance in this population. This study sought to evaluate the prevalence and risk factors for pharmacoresistance in pediatric FCD-related epilepsy.

METHODS

In this retrospective single-center cohort design, patients were identified from search of centralized radiology report database and a central epilepsy surgical database. Inclusion criteria consisted of 3T MRI-confirmed FCD from January, 2011, to January, 2020; ages 0 days to 22 years at MRI; and at least 18 months of documented follow-up after MRI, unless had single seizure or incidentally discovered FCD. Records were excluded if there was dual pathology (except for mesial temporal sclerosis), hemimegalencephaly, or tuberous sclerosis complex present in imaging or history.

RESULTS

One hundred forty-three patients with confirmed FCD met the inclusion criteria. One hundred twenty-four children had epilepsy (87% of patients with FCD) with median age at seizure onset 2.7 years (IQR 0.75-6 years, range 0-17 years). Twelve children (8.5%) had a single lifetime seizure (provoked or unprovoked) or recurrent provoked seizures. Seven children (4.9%) had incidental FCD. Ninety-two patients (74%) of those with epilepsy met criteria for pharmacoresistance. Of children with epilepsy of all types, 93 children (75%) were seizure-free at the last visit; 82 patients underwent epilepsy surgery, of whom 59 (72%) achieved seizure freedom. Seven percent (9/124) achieved seizure freedom with a second ASM and 5.6% (7/124) with a third or more ASMs. Failure of only 1 antiseizure medication is associated with enormous increased incidence and earlier development of pharmacoresistance (OR 346; 95% CI 19.6-6,100); Cox regression showed FCD lobar location, pathologic subtype, and age at seizure onset are not.

DISCUSSION

Failure of 1 antiseizure medication is associated with substantial risk of pharmacoresistance. These data support an operational redefinition of pharmacoresistance, for surgical planning, in FCD-related epilepsy to the failure of 1 antiseizure medication and support early, potentially curative surgery to improve outcomes in this patient population.

Long-term Outcome of Epilepsy and Cortical Malformations Due to Abnormal Migration and Postmigrational Development: A Cohort Study

OBJECTIVE

To evaluate the long-term outcome of patients with epilepsy and malformations of cortical development (MCD).

METHODS

We conducted a historical cohort study of patients with epilepsy and MCD due to impaired neuronal migration and postmigration organization, and with a follow-up period of ≥5 years. For each patient, MCD was classified after accurate neuroimaging reappraisal by an expert neuroradiologist. The primary outcome was remission, defined as a period of seizure freedom ≥5 years at any time from epilepsy onset. We used Kaplan-Meier estimates for survival analysis, and univariate and multivariate Cox regression analyses to evaluate baseline variables as possible factors associated with remission.

RESULTS

The cohort included 71 patients (M/F=31/40) with a 17-year median follow-up (1506 person-years). About half (49.3%) had heterotopia, 35.2% polymicrogyria, 7% lissencephaly and 8.5% had the combination of two MCD. The mean age at seizure onset was 12.4±7.2 years. Intellectual disability and neurological deficits were observed in 30.4% and 40.9%, respectively. More than 60% of patients had refractory epilepsy. In three patients who underwent epilepsy surgery, MCD diagnosis was confirmed by histology. At last visit, 44% of patients had been seizure-free during the previous year, however none of them had stopped anti-seizure medication. Thirty patients achieved remission (Remission group, 42.2%) at some point in their disease history, whereas 41 individuals (Non Remission group, 57.8%) had never been in remission for ≥5 years. The cumulative remission rate was 38% by 20 years from inclusion. In the Cox model, unilateral distribution of MCD (HR: 2.68, 95% CI: 1.04-6.92) and a low seizure frequency at onset (HR: 5.01, 95% CI: 1.12-22.5) were significantly associated with remission.

CONCLUSIONS

Patients with epilepsy and MCD showed a remission rate of 38% by 20 years from onset. Unilateral distribution of the MCD is associated with a three-fold probability of achieving remission. About 40% of patients showed a drug-sensitive condition with risk of relapse during their epilepsy course.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in patients with epilepsy and MCD, unilateral MCD and low seizure frequency at onset are associated with achieving epilepsy remission.

Localizing and Lateralizing Value of Seizure Onset Pattern on Surface EEG in FCD Type II

BACKGROUND

Surface ictal electroencephalographic (EEG) monitoring has an important role in the presurgical evaluation of patients with focal cortical dysplasia (FCD). This study aimed to examine the characteristics of seizure onset pattern (SOP) on surface ictal EEG. This information will be useful for invasive monitoring planning.

METHODS

We reviewed 290 seizures from 31 patients with intractable seizures related to FCD type II (6 patients with FCD IIa and 25 patients with FCD IIb). We categorized the SOPs into five patterns and evaluated the relationships between the SOPs and the location and pathology of the FCD II subtype.

RESULTS

The most common SOP was no apparent change (39.0%), followed by rhythmic slow wave and repetitive spikes/sharp waves. The SOP of rhythmic slow wave was associated with FCD II in the temporal lobe (P < 0.001), and the SOP of no apparent change was associated with FCD II in the occipital lobe (P = 0.012). The SOPs of rhythmic slow waves and fast activity were most common in FCD IIa, P < 0.001 and 0.031, respectively. The repetitive spikes/sharp waves SOP was the most common pattern in FCD IIb (P < 0.001). The surface SOPs provided correct localization and lateralization of epileptic foci in FCD in 62.1% and 62.7%, respectively. In 61.3% of the patients, over 50% of the SOPs in each patient indicated accurate localization.

CONCLUSIONS

SOPs in surface EEG monitoring are beneficial for presurgical evaluation and lead to localization of epileptic foci and pathologic subtypes of FCD.

Interictal pattern on scalp electroencephalogram predicts excellent surgical outcome of epilepsy caused by focal cortical dysplasia

OBJECTIVE

Focal cortical dysplasia (FCD) represents an essential cause of drug-resistant epilepsy with surgery as an effective treatment option. This study aimed to identify the important predictors of favorable surgical outcomes and the impact of the interictal scalp electroencephalogram (EEG) patterns in predicting postsurgical seizure outcomes.

METHODS

We retrospectively evaluated 210 consecutive patients between 2015 and 2019. They were diagnosed with FCD by pathology, underwent resection, and had at least one year of postsurgical follow-up. Predictors of seizure freedom were analyzed.

RESULTS

Based on the information at the latest follow-up, seizure outcome was classified as Engel Class I (seizure-free) in 81.4% and Engel Class II-IV (non-seizure-free) in 18.6% of patients. There were 43, 105, and 62 cases of FCD type I, type II, and type III, respectively. The interictal EEG showed a repetitive discharge pattern (REDP) in 87 (41.4%) patients, polyspike discharge pattern (PDP) in 41 (19.5%), and the coexistence of REDP and PDP in the same location in 32 (15.2%) patients. The analyzed patterns in order of frequency were repetitive discharges lasting 5 seconds or more (32.4%); polyspikes (16.7%); RED type 1 (11.4%); continuous epileptiform discharges occupying >80% of the recording (11.4%); RED type 2 (6.2%); brushes (3.3%); focal, fast, continuous spikes (2.4%); focal fast rhythmic epileptiform discharges (1.43%); and frequent rhythmic bursting epileptiform activity (1.4%). The coexistence of REDP and PDP in the same location on scalp EEG and complete resection of the assumed epileptogenic zone (EZ) was independently associated with favorable postsurgical prognosis.

SIGNIFICANCE

Resective epilepsy surgery for intractable epilepsy caused by FCD has favorable outcomes. Interictal scalp EEG patterns were revealed to be predictive of excellent surgical outcomes and may help clinical decision-making and enable better presurgical evaluation.

Electroclinical and Multimodality Neuroimaging Characteristics and Predictors of Post-Surgical Outcome in Focal Cortical Dysplasia Type IIIa

Focal cortical dysplasia (FCD) type IIIa is an easily ignored cause of intractable temporal lobe epilepsy. This study aimed to analyze the clinical, electrophysiological, and imaging characteristics in FCD type IIIa and to search for predictors associated with postoperative outcome in order to identify potential candidates for epilepsy surgery. We performed a retrospective review including sixty-six patients with FCD type IIIa who underwent resection for drug-resistant epilepsy. We evaluated the clinical, electrophysiological, and neuroimaging features for potential association with seizure outcome. Univariate and multivariate analyses were conducted to explore their predictive role on the seizure outcome. We demonstrated that thirty-nine (59.1%) patients had seizure freedom outcomes (Engel class Ia) with a median postsurgical follow-up lasting 29.5 months. By univariate analysis, duration of epilepsy (less than 12 years) (p = 0.044), absence of contralateral insular lobe hypometabolism on PET/MRI (p_Log-rank = 0.025), and complete resection of epileptogenic area (p_Log-rank = 0.004) were associated with seizure outcome. The incomplete resection of the epileptogenic area (hazard ratio = 2.977, 95% CI 1.218–7.277, p = 0.017) was the only independent predictor for seizure recurrence after surgery by multivariate analysis. The results of past history, semiology, electrophysiological, and MRI were not associated with seizure outcomes. Carefully included patients with FCD type IIIa through a comprehensive evaluation of their clinical, electrophysiological, and neuroimaging characteristics can be good candidates for resection. Several preoperative factors appear to be predictive of the postoperative outcome and may help in optimizing the selection of ideal candidates to benefit from epilepsy surgery.

Predictors of surgical outcome in focal cortical dysplasia and its subtypes

OBJECTIVE

The authors analyzed predictors of surgical outcome in patients with focal cortical dysplasia (FCD) and its ILAE (International League Against Epilepsy) subtypes after noninvasive multimodal evaluation and calculated time to first seizure.

METHODS

Data of 355 patients with refractory epilepsy, confirmed FCD pathology, and 2-13 years of postsurgical follow-up were analyzed to determine the predictive roles of clinical, EEG, imaging, and surgical factors that influence seizure freedom.

RESULTS

The mean ± SD age at surgery was 20.26 ± 12.18 years. In total, 142 (40.0%) patients had daily seizures and 90 (25.3%) had multiple seizure types. MRI showed clear-cut FCD in 289 (81.4%) patients. Pathology suggested type I FCD in 27.3% of patients, type II in 28.4%, and type III in 42.8% of patients. At latest follow-up, 72.1% of patients were seizure free and 11.8% were seizure free and not receiving antiepileptic drugs. Among the subtypes, 88.8% of patients with type III, 69.3% with type II, and 50.5% with type I FCD were seizure free. Multiple seizure types, acute postoperative seizures (APOS), and type I FCD were predictors of persistent seizures, whereas type III FCD was the strongest predictor of seizure freedom. Type I FCD was associated with daily seizures, frontal and multilobar distribution, subtle findings on MRI, incomplete resection, and persistent seizures. Type II and III FCD were associated with clear-cut lesion on MRI, regional interictal and ictal EEG onset pattern, focal pattern on ictal SPECT, complete resection, and seizure freedom. Type III FCD was associated with temporal location, whereas type I and II FCD were associated with extratemporal location. Nearly 80% of patients with persistent seizures, mostly those with type I FCD, had their first seizure within 6 months postsurgery.

CONCLUSIONS

Long-term seizure freedom after surgery can be achieved in more than two-thirds of patients with FCD after noninvasive multimodal evaluation. Multiple seizure types, type I FCD, and APOS were predictors of persistent seizures. Seizures recurred in about 80% of patients within 6 months postsurgery.

The effect of injection time on rates of epileptogenic zone localization using SISCOM and STATISCOM

BACKGROUND

The identification of hyperperfusion on ictal single-photon emission computed tomography (SPECT) scan is a technique for the localization of the epileptogenic zone (EZ) in patients with focal epilepsy undergoing presurgical evaluation. The accuracy of this technique has been improved by subtraction from an interictal image and coregistration with magnetic resonance imaging (MRI) (subtraction ictal SPECT coregistered to MRI (SISCOM)), and subsequently by the development of Statistical Ictal SPECT Co-registered to MRI (STATISCOM) which is reported to further improve localization accuracy by statistically accounting for random variation between images. However, the use of ictal SPECT is limited by the necessity for rapid injection of the radiotracer. The purpose of this study was to investigate the effect of tracer injection time on EZ localization rates using both STATISCOM and SISCOM.

METHODS

Consecutive patients with drug-resistant focal epilepsy who had an ictal SPECT scan while admitted to the video-electroencephalography (EEG) monitoring unit at the Royal Melbourne Hospital, Victoria, Australia, and a subsequent interictal scan, between 2009 and 2017 were included. The information collected included age, sex, seizure type, epilepsy diagnosis, and injection time. Statistical Ictal SPECT Co-registered to MRI and SISCOM images were generated and reviewed by two blinded reviewers. The rates of potential localization of the EZ, and the agreement with the EEG, were determined for each scan. Localization rates were compared between ictal scans with different radiotracer injection time windows (<30 s, 30-45 s, 45-60 s, 60-90 s, 90-120 s, >120 s).

RESULTS

Seventy patients (male = 32, 16-67 years) were included in the study. Overall agreement between the primary raters was moderate for STATISCOM (k = 0.44) and SISCOM (k = 0.57). The ability of SPECT to localize the potential EZ was 69% (48/70) for STATISCOM and 59% (41/70) for SISCOM. Injection time was not associated with the rate of localizing the potential EZ for STATISCOM (p = 0.64), whereas for SISCOM there was a trend that shorter injection times were associated with better ability to localize the potential EZ (p = 0.06). Agreement between SPECT and video-EEG data was 54% (38/70) for STATISCOM and 39% (27/70) for SISCOM. Statistical Ictal SPECT Co-registered to MRI did not show any difference of agreement across injection time groups (p = 0.42) whereas SISCOM showed better agreement with video-EEG data in the earlier injection time groups (p = 0.02). No differences in agreement between SPECT and video-EEG data were seen between patients with and without MRI lesions for either STATISCOM or SISCOM. Statistical Ictal SPECT Co-registered to MRI showed significantly better agreement for temporal than extratemporal seizures, with no difference of agreement between early (<45 s) and late (>45 s) injections.

CONCLUSION

Statistical Ictal SPECT Co-registered to MRI showed overall higher agreement rates with EZ localization by video-EEG than SISCOM, which was not affected by the injection times. Statistical Ictal SPECT Co-registered to MRI may provide localizing information for "late" injections where visual reads and SISCOM are inconclusive.

Surgical outcome and prognostic factors in epilepsy patients with MR-negative focal cortical dysplasia

Objective

Focal cortical dysplasia (FCD) represents a heterogeneous group of disorders of the cortical formation and is one of the most common causes of epilepsy. Magnetic resonance imaging (MRI) is the modality of choice for detecting structural lesions, and the surgical prognosis in patients with MR lesions is favorable. However, the surgical prognosis of patients with MR-negative FCD is unknown. We aimed to evaluate the long-term surgical outcomes and prognostic factors in MR-negative FCD patients through comprehensive presurgical data.

Methods

We retrospectively reviewed data from 719 drug-resistant epilepsy patients who underwent resective surgery and selected cases in which surgical specimens were pathologically confirmed as FCD Type I or II. If the epileptogenic focus and surgical specimens were obtained from brain areas with a normal MRI appearance, they were classified as MR-negative FCD. Surgical outcomes were evaluated at 2 and 5 years, and clinical, neurophysiological, and neuroimaging data of MR-negative FCD were compared to those of MR-positive FCD.

Results

Finally, 47 MR-negative and 34 MR-positive FCD patients were enrolled in the study. The seizure-free rate after surgery (Engel classification I) at postoperative 2 year was 59.5% and 64.7% in the MR-negative and positive FCD groups, respectively (p = 0.81). This rate decreased to 57.5% and 44.4% in the MR-negative and positive FCD groups (p = 0.43) at postoperative 5 years. MR-negative FCD showed a higher proportion of FCD type I (87.2% vs. 50.0%, p = 0.001) than MR-positive FCD. Unilobar cerebral perfusion distribution (odds ratio, OR 5.41) and concordance of interictal epileptiform discharges (OR 5.10) were significantly associated with good surgical outcomes in MR-negative FCD.

Conclusion

In this study, MR-negative and positive FCD patients had a comparable surgical prognosis, suggesting that comprehensive presurgical evaluations, including multimodal neuroimaging studies, are crucial for obtaining excellent surgical outcomes even in epilepsy patients with MR-negative FCD.

A review of magnetoencephalography use in pediatric epilepsy: an update on best practice

Introduction: Magnetoencephalography (MEG) is a noninvasive technique that is used for presurgical evaluation of children with drug-resistant epilepsy (DRE).Areas covered: The contributions of MEG for localizing the epileptogenic zone are discussed, in particular in extra-temporal lobe epilepsy and focal cortical dysplasia, which are common in children, as well as in difficult to localize epilepsy such as operculo-insular epilepsy. Further, the authors review current evidence on MEG for mapping eloquent cortex, its performance, application in clinical practice, and potential challenges.Expert opinion: MEG could change the clinical management of children with DRE by directing placement of intracranial electrodes thereby enhancing their yield. With improved identification of a circumscribed epileptogenic zone, MEG could render more patients as suitable candidates for epilepsy surgery and increase utilization of surgery.

Neuropathology of Surgically Managed Epilepsy Specimens

Epilepsy is characterized as recurrent seizures, and it is one of the most prevalent disorders of the human nervous system. A large and diverse profile of different syndromes and conditions can cause perturbations in neural networks that are associated with epilepsy. Advances in neuroimaging and electrophysiological monitoring have enhanced our ability to localize the neuropathological lesions that alter the neural networks giving rise to epilepsy, whereas advances in surgical management have resulted in excellent seizure control in many patients following resections. Histopathologic study using a variety of special stains, molecular analysis, and functional studies of these resected tissues has facilitated the neuropathological characterization of these lesions. Here, we review the neuropathology of common structural lesions that cause epilepsy and are amenable to neurosurgical resection, such as hippocampal sclerosis, focal cortical dysplasia, and its associated principal lesions, including long-term epilepsy-associated tumors, as well as other malformations of cortical development and Rasmussen encephalitis.

Surgical treatment of nonlesional temporal lobe epilepsy

PURPOSE

One-third of the patients with drug-resistant temporal lobe epilepsy (TLE) have a normal MRI, but there are only a few studies regarding the surgical outcomes and the efficacy of anterior temporal lobectomy (ATL) in patients with nonlesional TLE. The objective of this study is to evaluate the surgical outcomes and efficacy of ATL in patients with nonlesional TLE.

METHODS

We included 77 consecutive patients without MRI-identifiable lesions who had undergone surgical resection for drug-resistant TLE. We performed univariate and multivariate logistic regression analyses to identify the predictors of surgical outcomes, and the efficacy of ATL in patients with nonlesional TLE.

RESULTS

More than two-thirds of patients (51/76, 67.3 %) had achieved seizure freedom at the last follow-up. Presence of oroalimentary automatism, localized hypometabolism in FDG-PET, and concordant results in presurgical evaluations were associated with better surgical outcomes. Only 15 out of 77 patients (19.2 %) with nonlesional TLE were treated with ATL, and the surgically resected areas were located within the resection margin of ATL in one-third of the patients (26/77, 33.8 %). Patients with auras suggesting neocortical ictal onset and lateralizing semiological features had a higher chance that their potentially epileptogenic areas were located beyond or outside the resection margin of ATL.

CONCLUSION

Our study showed that the potentially epileptogenic areas were located beyond or outside the margin of the ATL in nearly two-thirds of the patients. Several clinical factors may be useful in predicting the location of an epileptogenic area, which can help optimize a surgical strategy in these patients.

Bottom-of-sulcus dysplasia: the role of 18F-FDG PET in identifying a focal surgically remedial epileptic lesion

PURPOSE

Bottom-of-sulcus dysplasia (BOSD) is a type of focal cortical dysplasia and an important cause of intractable epilepsy. While the MRI features of BOSD have been well documented, the contribution of PET to the identification of these small lesions has not been widely explored. The aim of this study was to investigate the role of F-18 fluorodeoxyglucose (¹⁸F-FDG) PET in the identification of BOSD.

METHODS

Twenty patients with BOSD underwent both ¹⁸F-FDG PET and structural MRI scans as part of preoperative planning for surgery. Visual PET analysis was performed, and patients were classified as positive if they exhibited a focal or regional hypometabolic abnormality, or negative in the absence of a hypometabolic abnormality. MRI data were reviewed to determine if any structural abnormality characteristic of BOSD were observed before and after co-registration with PET findings.

RESULTS

PET detected hypometabolic abnormalities consistent with the seizure focus location in 95% (19/20) of cases. Focal abnormalities were detected on ¹⁸F-FDG PET in 12/20 (60%) patients, while regional hypometabolism was evident in 7/20 (35%). BOSD lesions were missed in 20% (4/20) of cases upon initial review of MRI scans. Co-registration of ¹⁸F-FDG PET with MRI enabled detection of the BOSD in all four cases where the lesion was initially missed.

CONCLUSION

Our findings show that ¹⁸F-FDG PET provides additional clinical value in the localisation and detection of BOSD lesions, when used in conjunction with MRI.

Focal cortical dysplasia: etiology, epileptogenesis, classification, clinical presentation, imaging, and management

BACKGROUND

Focal cortical dysplasia (FCD) is the most prevalent cause of intractable epilepsy in children. It was first described by Taylor et al. in 1971. In 2011, the International League against Epilepsy described an international consensus of classification for FCD. However, the exact mechanism causing this pathology remains unclear. The diagnosis and recognition of FCD increase with the advances in neuroradiology and electrophysiology.

FOCUS OF REVIEW

In this paper, we discuss the literature regarding management of FCD with a focus on etiology, pathophysiology, classification, clinical presentation, and imaging modalities. We will also discuss certain variables affecting surgical outcome of patients with FCD.

CONCLUSION

Based on our review findings, it is concluded that surgical management with complete resection of the lesion following preoperative localization of the epileptogenic zone in patients with FCD subtypes can provide a seizure-free outcome.

Surgical strategy for focal cortical dysplasia based on the analysis of the spike onset and peak zones on magnetoencephalography

OBJECTIVE

The aim of this study was to elucidate the surgical strategy for focal cortical dysplasia (FCD) based on the interictal analysis on magnetoencephalography (MEG). For this purpose, the correlation between the spike onset zone (Sp-OZ) and the spike peak zone (Sp-PZ) on MEG was evaluated to clarify the differences in the Sp-OZ and its correlation with Sp-PZ in FCD subtypes to develop an appropriate surgical strategy.

METHODS

Forty-one FCD patients (n = 17 type I, n = 13 type IIa, and n = 11 type IIb) were included. The Sp-OZ was identified by the summation of gradient magnetic-field topography (GMFT) magnitudes at interictal MEG spike onset, and Sp-PZ was defined as the distribution of the equivalent current dipole (ECD) at spike peak. Correlations between Sp-OZ and Sp-PZ distributions were evaluated and compared with clinical factors and seizure outcomes retrospectively.

RESULTS

Good seizure outcomes (Engel class I) were obtained significantly more often in patients with FCD type IIb (10/11, 90.9%) than those with type IIa (4/13, 30.8%; p = 0.003) and type I (6/17, 35.3%; p = 0.004). The Sp-OZ was significantly smaller (1 or 2 gyri) in type IIb (10, 90.9%) than in type IIa (4, 30.8%; p = 0.003) or type I (9, 53.0%; p = 0.036). Concordant correlations between the Sp-OZ and Sp-PZ were significantly more frequent in type IIb (7, 63.6%) than in type IIa (1, 7.7%; p = 0.015) or type I (1, 5.8%; p = 0.004). Complete resection of the Sp-OZ achieved significantly better seizure outcomes (Engel class I: 9/10, 90%) than incomplete resection (11/31, 35.5%) (p = 0.003). In contrast, complete resection of the Sp-PZ showed no significant difference in good seizure outcomes (9/13, 69.2%) compared with incomplete resection (11/28, 39.3%).

CONCLUSIONS

The Sp-OZ detected by MEG using GMFT and its correlation with Sp-PZ were related to FCD subtypes. A discordant distribution between Sp-OZ and Sp-PZ in type I and IIa FCD indicated an extensive epileptogenic zone and a complex epileptic network. Type IIb showed a restricted epileptogenic zone with the smaller Sp-OZ and concordance between Sp-OZ and Sp-PZ. Complete resection of the Sp-OZ provided significantly better seizure outcomes than incomplete resection. Complete resection of the Sp-PZ was not related to seizure outcomes. There was a definite difference in the epileptogenic zone among FCD subtypes; hence, an individual surgical strategy taking into account the correlation between the Sp-OZ and Sp-PZ should be considered.

Distinguishing Focal Cortical Dysplasia From Glioneuronal Tumors in Patients With Epilepsy by Machine Learning

Purpose: We are aiming to build a supervised machine learning-based classifier, in order to preoperatively distinguish focal cortical dysplasia (FCD) from glioneuronal tumors (GNTs) in patients with epilepsy. Methods: This retrospective study was comprised of 96 patients who underwent epilepsy surgery, with the final neuropathologic diagnosis of either an FCD or GNTs. Seven classical machine learning algorithms (i.e., Random Forest, SVM, Decision Tree, Logistic Regression, XGBoost, LightGBM, and CatBoost) were employed and trained by our dataset to get the classification model. Ten features [i.e., Gender, Past history, Age at seizure onset, Course of disease, Seizure type, Seizure frequency, Scalp EEG biomarkers, MRI features, Lesion location, Number of antiepileptic drug (AEDs)] were analyzed in our study. Results: We enrolled 56 patients with FCD and 40 patients with GNTs, which included 29 with gangliogliomas (GGs) and 11 with dysembryoplasic neuroepithelial tumors (DNTs). Our study demonstrated that the Random Forest-based machine learning model offered the best predictive performance on distinguishing the diagnosis of FCD from GNTs, with an F1-score of 0.9180 and AUC value of 0.9340. Furthermore, the most discriminative factor between FCD and GNTs was the feature "age at seizure onset" with the Chi-square value of 1,213.0, suggesting that patients who had a younger age at seizure onset were more likely to be diagnosed as FCD. Conclusion: The Random Forest-based machine learning classifier can accurately differentiate FCD from GNTs in patients with epilepsy before surgery. This might lead to improved clinician confidence in appropriate surgical planning and treatment outcomes.

Advances in the Surgical Management of Epilepsy: Drug-Resistant Focal Epilepsy in the Adult Patient

Pharmacoresistant seizures occur in nearly one-third of people with epilepsy. Medial temporal lobe and lesional epilepsy are the most favorable surgically remediable epileptic syndromes. Successful surgery may render the patient seizure-free, reduce antiseizure drug(s) adverse effects, improve quality of life, and decrease mortality. Surgical management should not be considered a procedure of "last resort." Despite the results of randomized controlled trials, surgery remains an underutilized treatment modality for patients with drug-resistant epilepsy (DRE). Important disparities affect patient referral and selection for surgical treatment. This article discusses the advances in surgical treatment of DRE in adults with focal seizures.

[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.

5-Aminolevulinic Acid-Induced Fluorescence in Focal Cortical Dysplasia: Report of 3 Cases

BACKGROUND

Three patients enrolled in a clinical trial of 5-aminolevulinic-acid (5-ALA)-induced fluorescence-guidance, which has been demonstrated to facilitate intracranial tumor resection, were found on neuropathological examination to have focal cortical dysplasia (FCD).

OBJECTIVE

To evaluate in this case series visible fluorescence and quantitative levels of protoporphyrin IX (PpIX) during surgery and correlate these findings with preoperative magnetic resonance imaging (MRI) and histopathology.

METHODS

Patients were administered 5-ALA (20 mg/kg) approximately 3 h prior to surgery and underwent image-guided, microsurgical resection of their MRI- and electrophysiologically identified lesions. Intraoperative visible fluorescence was evaluated using an operating microscope adapted with a commercially available blue light module. Quantitative PpIX levels were assessed using a handheld fiber-optic probe and a wide-field imaging spectrometer. Sites of fluorescence measurements were co-registered with both preoperative MRI and histopathological analysis.

RESULTS

Three patients with a pathologically confirmed diagnosis of FCD (Types 1b, 2a, and 2b) underwent surgery. All patients demonstrated some degree of visible fluorescence (faint or moderate), and all patients had quantitatively elevated concentrations of PpIX. No evidence of neoplasia was identified on histopathology, and in 1 patient, the highest concentrations of PpIX were found at a tissue site with marked gliosis but no typical histological features of FCD.

CONCLUSION

FCD has been found to be associated with intraoperative 5-ALA-induced visible fluorescence and quantitatively confirmed elevated concentrations of the fluorophore PpIX in 3 patients. This finding suggests that there may be a role for fluorescence-guidance during surgical intervention for epilepsy-associated FCD.

Focal cortical dysplasia imaging discrepancies between MRI and FDG-PET: Unique association with temporal lobe location

PURPOSE

Although magnetic resonance imaging (MRI) and ¹⁸F-2-fluorodeoxyglucose-positron emission tomography (FDG-PET) are used for pre-surgical assessment of focal cortical dysplasia (FCD), they often disagree. This study aimed to identify factors that contribute to discrepancies in FCD imaging between MRI and FDG-PET.

METHODS

Sixty-two patients (mean age, 18.9 years) with a FCD type I or II were retrospectively selected. These patients were visually categorized into two groups: 1) extent of PET abnormality larger than MRI abnormality and 2) vice versa or equivalent. Predictive factors of these two groups were analyzed by multivariate logistic regression. The extent of hypometabolic transient zone surrounding FCDs and their mean standardized uptake values were measured and compared by the Mann-Whitney U-test.

RESULTS

FCDs were detected on MRI and PET in 46 and 55 patients, respectively, whereas no abnormality was detected in 4 patients. The PET hypometabolic areas were larger than the MRI abnormal areas in 26 patients (88 % in the temporal lobe), whereas the PET hypometabolic areas were equivalent or smaller than the MRI abnormal areas in 32 patients (69 % in the frontal lobe). The temporal lobe location was an independent predictor for differentiating the two groups (OR = 35.2, 95 % CI = 6.81-168.0, P < .001). The temporal lobe lesions had significantly wider transient zones and lower standardized uptake values than those in the other lobes (P < .001, both).

CONCLUSION

The discrepancies between MRI and FDG-PET findings of FCD were associated with temporal lobe location.

Ultra-High-Field Targeted Imaging of Focal Cortical Dysplasia: The Intracortical Black Line Sign in Type IIb

BACKGROUND AND PURPOSE

Conventional MR imaging has limitations in detecting focal cortical dysplasia. We assessed the added value of 7T in patients with histologically proved focal cortical dysplasia to highlight correlations between neuropathology and ultra-high-field imaging.

MATERIALS AND METHODS

Between 2013 and 2019, we performed a standardized 7T MR imaging protocol in patients with drug-resistant focal epilepsy. We focused on 12 patients in whom postsurgical histopathology revealed focal cortical dysplasia and explored the diagnostic yield of preoperative 7T versus 1.5/3T MR imaging and the correlations of imaging findings with histopathology. We also assessed the relationship between epilepsy surgery outcome and the completeness of surgical removal of the MR imaging-visible structural abnormality.

RESULTS

We observed clear abnormalities in 10/12 patients using 7T versus 9/12 revealed by 1.5/3T MR imaging. In patients with focal cortical dysplasia I, 7T MR imaging did not disclose morphologic abnormalities (n = 0/2). In patients with focal cortical dysplasia II, 7T uncovered morphologic signs that were not visible on clinical imaging in 1 patient with focal cortical dysplasia IIa (n = 1/4) and in all those with focal cortical dysplasia IIb (n = 6/6). T2*WI provided the highest added value, disclosing a peculiar intracortical hypointense band (black line) in 5/6 patients with focal cortical dysplasia IIb. The complete removal of the black line was associated with good postsurgical outcome (n = 4/5), while its incomplete removal yielded unsatisfactory results (n = 1/5).

CONCLUSIONS

The high sensitivity of 7T T2*-weighted images provides an additional tool in defining potential morphologic markers of high epileptogenicity within the dysplastic tissue of focal cortical dysplasia IIb and will likely help to more precisely plan epilepsy surgery and explain surgical failures.

Ultrasonographic features of focal cortical dysplasia and their relevance for epilepsy surgery

OBJECTIVE Surgery has proven to be the best therapeutic option for drug-refractory cases of focal cortical dysplasia (FCD)-associated epilepsy. Seizure outcome primarily depends on the completeness of resection, rendering the intraoperative FCD identification and delineation particularly important. This study aims to assess the diagnostic yield of intraoperative ultrasound (IOUS) in surgery for FCD-associated drug-refractory epilepsy. METHODS The authors prospectively enrolled 15 consecutive patients with drug-refractory epilepsy who underwent an IOUS-assisted microsurgical resection of a radiologically suspected FCD between January 2013 and July 2016. The findings of IOUS were compared with those of presurgical MRI postprocessing and the sonographic characteristics were analyzed in relation to the histopathological findings. The authors investigated the added value of IOUS in achieving completeness of resection and improving postsurgical seizure outcome. RESULTS The neurosurgeon was able to identify the dysplastic tissue by IOUS in all cases. The visualization of FCD type I was more challenging compared to FCD II and the demarcation of its borders was less clear. Postsurgical MRI showed residual dysplasia in 2 of the 3 patients with FCD type I. In all FCD type II cases, IOUS allowed for a clear intraoperative visualization and demarcation, strongly correlating with presurgical MRI postprocessing. Postsurgical MRI confirmed complete resection in all FCD type II cases. Sonographic features correlated with the histopathological classification of dysplasia (sonographic abnormalities increase continuously in the following order: FCD IA/IB, FCD IC, FCD IIA, FCD IIB). In 1 patient with IOUS features atypical for FCD, histopathological investigation showed nonspecific gliosis. CONCLUSIONS Morphological features of FCD, as identified by IOUS, correlate well with advanced presurgical imaging. The resolution of IOUS was superior to MRI in all FCD types. The appreciation of distinct sonographic features on IOUS allows the intraoperative differentiation between FCD and non-FCD lesions as well as the discrimination of different histological subtypes of FCD. Sonographic demarcation depends on the underlying degree of dysplasia. IOUS allows for more tailored resections by facilitating the delineation of the dysplastic tissue.

Surgery for epilepsy

BACKGROUND

This is an updated version of the original Cochrane review, published in 2015.Focal epilepsies are caused by a malfunction of nerve cells localised in one part of one cerebral hemisphere. In studies, estimates of the number of individuals with focal epilepsy who do not become seizure-free despite optimal drug therapy vary between at least 20% and up to 70%. If the epileptogenic zone can be located, surgical resection offers the chance of a cure with a corresponding increase in quality of life.

OBJECTIVES

The primary objective is to assess the overall outcome of epilepsy surgery according to evidence from randomised controlled trials.Secondary objectives are to assess the overall outcome of epilepsy surgery according to non-randomised evidence, and to identify the factors that correlate with remission of seizures postoperatively.

SEARCH METHODS

For the latest update, we searched the following databases on 11 March 2019: Cochrane Register of Studies (CRS Web), which includes the Cochrane Epilepsy Group Specialized Register and the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid, 1946 to March 08, 2019), ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP).

SELECTION CRITERIA

Eligible studies were randomised controlled trials (RCTs) that included at least 30 participants in a well-defined population (age, sex, seizure type/frequency, duration of epilepsy, aetiology, magnetic resonance imaging (MRI) diagnosis, surgical findings), with an MRI performed in at least 90% of cases and an expected duration of follow-up of at least one year, and reporting an outcome related to postoperative seizure control. Cohort studies or case series were included in the previous version of this review.

DATA COLLECTION AND ANALYSIS

Three groups of two review authors independently screened all references for eligibility, assessed study quality and risk of bias, and extracted data. Outcomes were proportions of participants achieving a good outcome according to the presence or absence of each prognostic factor of interest. We intended to combine data with risk ratios (RRs) and 95% confidence intervals (95% CIs).

MAIN RESULTS

We identified 182 studies with a total of 16,855 included participants investigating outcomes of surgery for epilepsy. Nine studies were RCTs (including two that randomised participants to surgery or medical treatment (99 participants included in the two trials received medical treatment)). Risk of bias in these RCTs was unclear or high. Most of the remaining 173 non-randomised studies followed a retrospective design. We assessed study quality using the Effective Public Health Practice Project (EPHPP) tool and determined that most studies provided moderate or weak evidence. For 29 studies reporting multivariate analyses, we used the Quality in Prognostic Studies (QUIPS) tool and determined that very few studies were at low risk of bias across domains.In terms of freedom from seizures, two RCTs found surgery (n = 97) to be superior to medical treatment (n = 99); four found no statistically significant differences between anterior temporal lobectomy (ATL) with or without corpus callosotomy (n = 60), between subtemporal or transsylvian approach to selective amygdalohippocampectomy (SAH) (n = 47); between ATL, SAH and parahippocampectomy (n = 43) or between 2.5 cm and 3.5 cm ATL resection (n = 207). One RCT found total hippocampectomy to be superior to partial hippocampectomy (n = 70) and one found ATL to be superior to stereotactic radiosurgery (n = 58); and another provided data to show that for Lennox-Gastaut syndrome, no significant differences in seizure outcomes were evident between those treated with resection of the epileptogenic zone and those treated with resection of the epileptogenic zone plus corpus callosotomy (n = 43). We judged evidence from the nine RCTs to be of moderate to very low quality due to lack of information reported about the randomised trial design and the restricted study populations.Of the 16,756 participants included in this review who underwent a surgical procedure, 10,696 (64%) achieved a good outcome from surgery; this ranged across studies from 13.5% to 92.5%. Overall, we found the quality of data in relation to recording of adverse events to be very poor.In total, 120 studies examined between one and eight prognostic factors in univariate analysis. We found the following prognostic factors to be associated with a better post-surgical seizure outcome: abnormal pre-operative MRI, no use of intracranial monitoring, complete surgical resection, presence of mesial temporal sclerosis, concordance of pre-operative MRI and electroencephalography, history of febrile seizures, absence of focal cortical dysplasia/malformation of cortical development, presence of tumour, right-sided resection, and presence of unilateral interictal spikes. We found no evidence that history of head injury, presence of encephalomalacia, presence of vascular malformation, and presence of postoperative discharges were prognostic factors of outcome.Twenty-nine studies reported multi-variable models of prognostic factors, and showed that the direction of association of factors with outcomes was generally the same as that found in univariate analyses.We observed variability in many of our analyses, likely due to small study sizes with unbalanced group sizes and variation in the definition of seizure outcome, the definition of prognostic factors, and the influence of the site of surgery AUTHORS' CONCLUSIONS: Study design issues and limited information presented in the included studies mean that our results provide limited evidence to aid patient selection for surgery and prediction of likely surgical outcomes. Future research should be of high quality, follow a prospective design, be appropriately powered, and focus on specific issues related to diagnostic tools, the site-specific surgical approach, and other issues such as extent of resection. Researchers should investigate prognostic factors related to the outcome of surgery via multi-variable statistical regression modelling, where variables are selected for modelling according to clinical relevance, and all numerical results of the prognostic models are fully reported. Journal editors should not accept papers for which study authors did not record adverse events from a medical intervention. Researchers have achieved improvements in cancer care over the past three to four decades by answering well-defined questions through the conduct of focused RCTs in a step-wise fashion. The same approach to surgery for epilepsy is required.

The Concept of Drug-Resistant Epileptogenic Zone

Resective surgery is the most effective way to treat drug-resistant epilepsy. Despite extensive pre-surgical evaluation, only 30–70% patients would become seizure-free after surgery. New approaches and strategies are needed to improve the outcome of epilepsy surgery. It is commonly observed in clinical practice that antiepileptic drugs (AEDs) could maintain seizure freedom in a large proportion of patients after surgery, who were uncontrolled before the operation. In some patients cessation of AEDs leads to seizure recurrence which, in most cases, can be controlled by resuming AEDs. These observations suggest that the surgery has converted the epilepsy from drug-resistant to drug-responsive, implying that the operation has removed the brain tissue accounting for pharmacoresistance, rather than the pathological substrate of epilepsy (at least not completely). Based on these observations, it is hypothesized that there is a drug-resistant epileptogenic zone (DREZ) which overlaps with the epileptogenic zone (EZ), and has both epileptogenic and drug-resistant properties. DREZ is necessary and sufficient to cause drug-resistant epilepsy, and its remove would render the epilepsy drug-responsive. Testing the hypothesis requires the development of new methods to define the DREZ, which may be used to guide surgical planning when the epileptogenic zone cannot be completely excised. This concept can also help understand the mechanisms of drug-resistant epilepsy, leading to new therapeutic strategies.

Focal Cortical Dysplasia and Refractory Epilepsy: Role of Multimodality Imaging and Outcome of Surgery

BACKGROUND AND PURPOSE

Focal cortical dysplasia (FCD) is one of the most common causes of drug resistant epilepsy. Our aim was to evaluate the role of presurgical noninvasive multimodality imaging techniques in selecting patients with refractory epilepsy and focal cortical dysplasia for epilepsy surgery and the influence of the imaging modalities on long-term seizure freedom.

MATERIALS AND METHODS

We performed a retrospective analysis of data of 188 consecutive patients with FCD and refractory epilepsy with at least 2 years of postsurgery follow-up. Predictors of seizure freedom and the sensitivity of neuroimaging modalities were analyzed.

RESULTS

MR imaging showed clear-cut FCD in 136 (72.3%) patients. Interictal FDG-PET showed focal hypo-/hypermetabolism in 144 (76.6%); in 110 patients in whom ictal SPECT was performed, focal hyperperfusion was noted in 77 (70.3%). Focal resection was the most common surgery performed in 112 (59.6%). Histopathology revealed FCD type I in 102 (54.3%) patients. At last follow-up, 124 (66.0%) were seizure-free. Complete resection of FCD and type II FCD were predictors of seizure freedom. Localization of FCD on either MR imaging or PET or ictal SPECT had the highest sensitivity for seizure freedom at 97.5%. Among individual modalities, FDG-PET had the highest sensitivity (78.2%), followed by MR imaging (75.8%) and ictal SPECT (71.8%). The sensitivity of MR imaging to localize type I FCD (60.8%) was significantly lower than that for type II FCD (84.8%, P < .001). Among 37 patients with subtle MR imaging findings and a focal FDG-PET pattern, 30 patients had type I FCD.

CONCLUSIONS

During presurgical multimodality evaluation, localization of the extent of the epileptogenic zone in at least 2 imaging modalities helps achieve seizure freedom in about two-thirds of patients with refractory epilepsy due to FCD. FDG-PET is the most sensitive imaging modality for seizure freedom, especially in patients with type I FCD.

The Surgical and Cognitive Outcomes of Focal Cortical Dysplasia

Focal cortical dysplasia (FCD) is the major cause of intractable focal epilepsy in childhood leading to epilepsy surgery. The overall seizure freedom after surgery ranges between 50–75% at 2 years after surgery and the long-term seizure freedom remain relatively stable. Seizure outcome after surgery depends on a various factors such as pathologic etiologies, extent of lesion, and types of surgery. Therefore, seizure outcome after surgery for FCD should be analyzed carefully considering cohorts’ characteristics. Studies of pediatric epilepsy surgery emphasize the early surgical intervention for a better cognition. Early surgical intervention and cessation of seizure activity are important for children with intractable epilepsy. However, there are limited data on the cognitive outcome after surgery in pediatric FCD, requiring further investigation. This paper reviews the seizure and cognitive outcomes of epilepsy surgery for FCD in children. Several prognostic factors influencing seizure outcome after surgery will be discussed in detail.

Long-term seizure outcome after epilepsy surgery in patients with mild malformation of cortical development and focal cortical dysplasia

Focal cortical dysplasia (FCD) and mild malformation of cortical development (mMCD) are frequent histopathologic diagnoses in patients who undergo surgery for refractory epilepsy. Literature concerning surgical outcome in patients with mMCD, as well as its contrast with FCD, has been scarce. We studied 88 patients with a histopathologic diagnosis of isolated FCD (n = 57) or mMCD (n = 31), revised according to the latest International League Against Epilepsy (ILAE) guidelines, who underwent resective or disconnective surgery. Our findings suggest differences between mMCD and FCD in clinical presentation and surgical outcome after surgery. Patients with mMCD developed seizures later in life, and their lesions had a predilection for location in the temporal lobe and remained undetected by magnetic resonance imaging (MRI) more frequently. A diagnosis of mMCD has a less favorable surgical outcome. Still, 32% of these patients reached continuous seizure freedom (Engel class 1A) at a latest median follow-up duration of 8 years, compared to 59% in FCD. A histopathologic diagnosis of mMCD, extratemporal surgery, and indication of an incomplete resection each were independent predictors of poor outcome.

Surgical treatment of epilepsy in Vietnam: program development and international collaboration

OBJECTIVE

The purpose of this report was to describe an international collaboration model to facilitate the surgical treatment of children with epilepsy in Vietnam.

METHODS

This model uses three complementary methods to achieve a meaningful expansion in epilepsy surgery capacity: US-based providers visiting Hanoi, Vietnam; Vietnamese providers visiting the US; and ongoing telecollaboration, including case review and real-time mentorship using internet-based communication platforms.

RESULTS

Introductions took place during a US neurosurgeon’s visit to Vietnam in 2014. Given the Vietnamese surgeon’s expertise in intraventricular tumor surgery, the focus of the initial visit was corpus callosotomy. After two operations performed jointly, the Vietnamese surgeon went on to perform 10 more callosotomy procedures in the ensuing 6 months with excellent results. The collaborative work grew and matured in 2016–2017, with 40 pediatric epilepsy surgeries performed from 2015 through 2017. Because pediatric epilepsy care requires far more than neurosurgery, teams traveling to Vietnam included a pediatric neurologist and an electroencephalography (EEG) technologist. Also, in 2016–2017, a neurosurgeon, two neurologists, and an EEG nurse from Vietnam completed 2- to 3-month fellowships at Children’s of Alabama (COA) in the US. These experiences improved EEG capabilities and facilitated the development of intraoperative electrocorticography (ECoG), making nonlesional epilepsy treatment more feasible. The final component has been ongoing, i.e., regular communication. The Vietnamese team regularly sends case summaries for discussion to the COA epilepsy conference. Three patients in Vietnam have undergone resection guided by ECoG without the US team present, although there was communication via internet-based telecollaboration tools between Vietnamese and US EEG technologists. To date, two of these three patients remain seizure free. The Vietnamese team has presented the results of their epilepsy experience at two international functional and epilepsy surgery scientific meetings.

CONCLUSIONS

Ongoing international collaboration has improved the surgical care of epilepsy in Vietnam. Experience suggests that the combination of in-country and US-based training, augmented by long-distance telecollaboration, is an effective paradigm for increasing the capacity for highly subspecialized, multidisciplinary neurosurgical care.

Surgical Treatment of Lesional Mesial Temporal Lobe Epilepsy

Lesional mesial temporal lobe epilepsy (mTLE) concerns a lesion other than mesial hippocampal sclerosis present in the mesial temporal lobe and causing seizures. The lesions are usually composed of focal cortical dysplasia (FCD) or are tumorous. These are good candidates for surgical treatment. Sometimes, it is difficult to distinguish between tumors and FCD and to determine the extent of required removal. ¹¹C-methionine positron emission tomography (PET) is helpful in differentiating lesions before surgery in lesional mTLE. In ¹¹C-methionine PET imaging, tumors show a hot uptake, whereas FCD does not. In case of tumorous conditions, the removal of only specific lesions may be considered because the seizure outcome is dependent on complete excision of the tumor. There are several ways to safely access mesial temporal structures. The transsylvian-transcisternal approach is a good way to access the mesial structures while preserving the lateral and basal temporal structures. Actual lesions associated with epileptogenesis in FCD may be larger than they appear on magnetic resonance imaging. For this reason, evaluations to locate sufficient epileptogenic foci, including invasive studies, should be completed for FCD, and epilepsy surgery should be performed according to these results. Regardless, the ultimate goal of all epilepsy surgeries is to maximize seizure control while maintaining neurological function. Therefore, a tailored approach based on the properties of the lesion is needed.

An initial cost-effectiveness analysis of intraoperative magnetic resonance imaging (iMRI) in pediatric epilepsy surgery

PURPOSE

Previous studies have illustrated the clinical utility of the addition of intraoperative magnetic resonance imaging (iMRI) to conventional microsurgical resection. While iMRI requires initial capital cost investment, long-term reduction in costly follow-up management and reoperation costs may prove economically efficacious. The objective of this study is to investigate the cost-effectiveness of the addition of iMRI utilization versus conventional microsurgical techniques in focal cortical dysplasia (FCD) resection in pediatric patients with medically refractory epilepsy.

METHODS

We retrospectively reviewed the medical records of pediatric subjects who underwent surgical resection of FCD at the Children's National Health System between March 2005 and April 2015. Patients were assigned to one of three cohorts: iMRI-assisted resection, conventional resection with iMRI-assisted reoperation, or conventional resection. Direct costs included preoperative, operative, postoperative, long-term follow-up, and antiepileptic drug (AED) costs. The cost-effectiveness was calculated as the sum total of all direct medical costs over the quality-adjusted life years (QALYs). We also performed sensitivity analysis on numerous variables to assess the validity of our results.

RESULTS

Fifty-six consecutive pediatric patients underwent resective surgery for medically intractable FCD. Ten patients underwent iMRI-assisted resection; 7 underwent conventional resection followed by iMRI-assisted reoperation; 39 patients underwent conventional microsurgical resection. Taken over the lifetime of the patient, the cumulative discounted QALY of patients in the iMRI-assisted resection cohort was about 2.91 years, versus 2.61 years in the conventional resection with iMRI-assisted reoperation cohort, and 1.76 years for the conventional resection cohort. Adjusting for inflation, iMRI-assisted surgeries have a cost-effectiveness ratio of $16,179 per QALY, versus $28,514 per QALY for the conventional resection with iMRI-assisted reoperation cohort, and $49,960 per QALY for the conventional resection cohort. Sensitivity analysis demonstrated that no one single variable significantly altered cost-effectiveness across all three cohorts compared to the baseline results.

CONCLUSION

The addition of iMRI to conventional microsurgical techniques for resection of FCD in pediatric patients with intractable epilepsy resulted in increased seizure freedom and reduction in long-term direct medical costs compared to conventional surgeries. Our data suggests that iMRI may be a cost-effective addition to the surgical armamentarium for epilepsy surgery.

Growth Associated Protein 43 (GAP-43) as a Novel Target for the Diagnosis, Treatment and Prevention of Epileptogenesis

We previously showed increased growth associated protein 43 (GAP-43) expression in brain samples resected from patients with cortical dysplasia (CD), which was correlated with duration of epilepsy. Here, we used a rat model of CD to examine the regulation of GAP-43 in the brain and serum over the course of epileptogenesis. Baseline GAP-43 expression was higher in CD animals compared to control non-CD rats. An acute seizure increased GAP-43 expression in both CD and control rats. However, GAP-43 expression decreased by day 15 post-seizure in control rats, which did not develop spontaneous seizures. In contrast, GAP-43 remained up-regulated in CD rats, and over 50% developed chronic epilepsy with increased GAP-43 levels in their serum. GAP-43 protein was primarily located in excitatory neurons, suggesting its functional significance in epileptogenesis. Inhibition of GAP-43 expression by shRNA significantly reduced seizure duration and severity in CD rats after acute seizures with subsequent reduction in interictal spiking. Serum GAP-43 levels were significantly higher in CD rats that developed spontaneous seizures. Together, these results suggest GAP-43 as a key factor promoting epileptogenesis, a possible therapeutic target for treatment of progressive epilepsy and a potential biomarker for epilepsy progression in CD.

Surgical outcome and predictive factors of epilepsy surgery in pediatric isolated focal cortical dysplasia

OBJECTIVE

Focal cortical dysplasia (FCD) is a common cause of medically intractable epilepsy in children. Epilepsy surgery has been a valuable treatment option to achieve seizure freedom in these intractable epilepsy patients. We aimed to present long-term surgical outcome, in relation to pathological severity, and to assess predictive factors of epilepsy surgery in pediatric isolated FCD.

METHODS

We retrospectively analyzed the data of 58 children and adolescents, with FCD International League Against Epilepsy (ILAE) task force classification types I and II, who underwent resective epilepsy surgery and were followed for at least 2 years after surgery.

RESULTS

The mean age at epilepsy onset was 4.3 years (0-14.2 years), and mean age at epilepsy surgery was 9.4 years (0.4-17.5 years). The mean duration of postoperative follow-up was 5.1±2.6 years (2-12.4 years). Of 58 patients, 62% of patients achieved Engel class I at 2 years postoperatively, 58% at 5 years postoperatively, and 53% at the last follow up. Forty eight percent of our cohort successfully discontinued antiepileptic medication. Of 30 patients with seizure recurrence, 83% of seizures recurred within 2 years after surgery. We observed that FCD type IIb was significantly associated with a better surgical outcome. At fifth postoperative year, 88% of FCD IIb patients were seizure free compared with 21% of type I and 57% of type IIa patients (P=0.043). By multivariate analysis, lesion on MRI (P=0.02) and complete resection (P<0.01) were the most important predictive factors for a seizure-free outcome.

SIGNIFICANCE

Epilepsy surgery is highly effective; more than half of medically intractable epilepsy patients achieved seizure freedom after surgery. In addition, we found significant difference in surgical outcomes according to the ILAE task force classification. Lesion on MRI and complete resection were the most important predictive factors for favorable seizure outcome in isolated FCD patients.

Comparison of clinical features and surgical outcome in focal cortical dysplasia type 1 and type 2

INTRODUCTION

Recent ILAE classification defined focal cortical dysplasia (FCD) patients with accompanying epileptic lesions as a separate group. We investigated data of patients with sole FCD lesions regarding long-term seizure outcome and different characteristics of FCD type 1 and type 2 patients.

METHODS

Eighty children and adult patients underwent surgery for FCD were included to the analysis of factors differentiating FCD type 1 and type 2 groups and their effect on long-term outcome.

RESULTS

FCD type 2 patients had earlier epilepsy onset (8.1 vs. 6.1 years. p=0.019) and underwent surgery younger than type 1 (18.2 vs. 23.7 years. p=0.034). FCD type 2 patients were more prominently MR positive (77.8% vs. 53.8%. p=0.029), which increased within FCD type 2 group as patients become younger (p=0.028). FCD Type 1 lesions showed mostly multilobar extension and FCD type 2 mostly located in frontal lobe. Seizure freedom was achieved in 65.4% of FCD type 1 patients and 70.4% of FCD type 2 patients. Seven patients had permanent de novo neurological deficits. Mean follow-up time was 5.5 years (Range: 1-11 years).

CONCLUSION

Surgical intervention in carefully selected patients may facilitate favorable seizure outcome leading to better quality of life. FCD type 1 and type 2 groups present with evident differences, which may promote medical and surgical management of these pathologies.

Seizure Outcome of Patients with Magnetic Resonance Imaging-Negative Epilepsies: Still An Ongoing Debate

BACKGROUND

Surgical results regarding MRI-negative epilepsy were presented and related clinical and histopathological parameters were discussed.

METHODS

Thirty-six MRI-negative epilepsy patients were retrospectively analyzed. Histopathological specimens were re-reviewed by 2 blind neuropathologists and re-classified based on the current classifications.

RESULTS

The mean age at surgery and seizure onset was 24.5 years and 9.3 years, respectively. Eight patients were younger than 18 years. Mean duration of seizures was 15.3 years. All but 2 underwent invasive monitorization. Eighteen patients had hypometabolism on FDG-PET with temporal lobe involvement in majority (66.7%). Hypometabolism was found in all patients with hippocampal sclerosis (HS), which was present in 50% and 66.7% of focal cortical dysplasia (FCD) type I and II patients, respectively. The frontal lobe resection was the most frequent type of operation followed by resections in temporal, parietal and occipital lobes. In 7 patients, multilobar resection was performed. Histopathological diagnosis was FCD type I, II, III, HS, and gliosis in 14, 12, 2, 3 and 2 patients, respectively. The mean follow-up was 5.8 years. Seventeen patients were seizure free and favorable outcome (Engel's I and II) was found in 69.7%. FCD type I tend to have more favorable seizure outcome. Duration of epilepsy and hypometabolism on FDG-PET was significantly related to outcome, whereas involved lobe was not.

CONCLUSIONS

Our results suggest it is worth pursuing resective surgery in adults as well as in children with drug-resistant epilepsy with normal MRI.

Surgical outcomes in two different age groups with Focal Cortical Dysplasia type II: Any real difference?

OBJECTIVE

Focal Cortical Dysplasias (FCDs) represent a common architectural cortical disorder underlying drug-resistant focal epilepsy. So far, studies aimed at evaluating whether age at surgery is a factor influencing surgical outcome are lacking, so that data on the comparison between patients harboring Type II FCD operated at younger age and those operated at adult age are still scarce. We compared presurgical clinical features and surgical outcomes of patients with histopathologically diagnosed Type II FCD undergoing surgery at an earlier age with those operated after 20 years of age.

METHODS

We retrospectively analyzed 1660 consecutive patients operated at the "Claudio Munari" Epilepsy Surgery Centre. There were 289 patients (17.4%) with a neuropathological diagnosis of Type II FCD. We included two different groups of patients, the first one including patients operated on at less than 6years, the second sharing the same seizure onset age but with delayed surgery, carried out after the age of 20. Seizure characteristics and, neuropsychological and postoperative seizure outcomes were evaluated by study group.

RESULTS

Forty patients underwent surgery before the age of 6 and 66 patients after the age of 20. Surgical outcome was favorable in the whole population (72.6% were classified in Engel's Class Ia+Ic), independently from age at surgery. In the children group, 32 patients were classified in Class I, including 30 (75%) children in classes Ia and Ic. In the adult group, 53 belonged to Class I of whom 47 (71%) were in classes Ia and Ic. The percentage of permanent complications, the surgical outcomes, and AED withdrawal did not significantly differ by study group.

CONCLUSION

Our results indicate that there is no difference between the groups, suggesting that outcome depends mainly on the histological findings and not on timing of surgery.

Clinical characteristics and epilepsy outcomes following surgery caused by focal cortical dysplasia (type IIa) in 110 adult epileptic patients

The aim of the present study was to investigate the effects of surgical intervention of focal cortical dysplasia (FCD) IIa on the outcome of epilepsy, and to evaluate the prognostic factors of seizure freedom. Patient data from epilepsy surgeries were retrospectively reviewed at the Second Affiliated Hospital of Dalian Medical University between 2007 and 2015. A total of 110 patients with a definite pathological diagnosis of FCD IIa were included. Moreover, the clinical characteristics, seizure outcome and quality of life in adults with FCD IIa were evaluated. The Engel seizure outcome achievements were class I in 72, class II in 20, class III in 11 and class IV in 7 patients. In addition, the Engel seizure outcome was relevant with the resection range of the lesions (P=0.028). The assessments of electrocorticography (ECoG) patterns and magnetic resonance imaging (MRI) are relevant to determining the extent of the resection, which may influence the surgery outcome (P=0.001 and P=0.023). Using multivariate regression analyses, the extent of resection, seizure frequency, preoperative ECoG and location of resection were the most important risk factors for seizure recurrence. The results of quality of life in epilepsy-10 scoring revealed that the quality of life improved significantly following surgery (P<0.01). Moreover, surgical intervention, EcoG, MRI positioning and complete resection helped to have improved seizure control, relief of anxiety and quality of life. All these observations strongly recommend an early consideration of epilepsy surgery in FCD IIa patients.

The Role of Radionuclide Imaging in Epilepsy, Part 1: Sporadic Temporal and Extratemporal Lobe Epilepsy

Epilepsy is one of the most common yet diverse neurologic disorders, affecting almost 1%-2% of the population. Presently, radionuclide imaging such as PET and SPECT is not used in the primary diagnosis or evaluation of recent-onset epilepsy. However, it can play a unique and important role in certain specific situations, such as in noninvasive presurgical localization of epileptogenic brain regions in intractable-seizure patients being considered for epilepsy surgery. Radionuclide imaging can be particularly useful if MR imaging is either negative for lesions or shows several lesions of which only 1 or 2 are suspected to be epileptogenic and if electroencephalogram changes are equivocal or discordant with the structural imaging. Similarly, PET and SPECT can also be useful for evaluating the functional integrity of the rest of the brain and may provide useful information on the possible pathogenesis of the neurocognitive and behavioral abnormalities frequently observed in these patients.

Epilepsy prevalence and severity predictors in MRI-identified focal cortical dysplasia

OBJECTIVES

To determine the prevalence of epilepsy and drug-resistant epilepsy in pediatric patients with focal cortical dysplasia (FCD) identified by magnetic resonance imaging (MRI). To determine clinical and imaging differences between those with drug-resistant epilepsy, drug-responsive epilepsy, and no epilepsy among children with MRI-identified FCD.

METHODS

A keyword search of a hospital radiology database identified 97 study participants for inclusion in this retrospective study. Participants were included if they were under 18 years of age at time of database query and had an MRI between 2004 and 2013 showing FCD. Exclusion was based on imaging and clinical characteristics. Data was gathered using a chart review and supplemental questionnaire.

RESULTS

In this cohort of patients with imaging findings compatible with FCD, 29% had not developed epilepsy. The prevalence of epilepsy and drug-resistant epilepsy was 71.13% (95% C.I.=61.05-79.89%) and 32.99% (95% C.I.=23.78-43.27%), respectively. Patients with epilepsy were more likely to have temporal (p=0.029) or frontal (p=0.044) lobe lesions and a family history of seizures (p=0.003) than those without epilepsy. Age of seizure onset was later in those with drug-responsive epilepsy than those with drug-resistant epilepsy (p=0.0002). A later age of seizure onset (OR=1.22, p=0.0441, 95% C.I.=1.00-1.486) and absence of developmental delay (OR=3.624, p=0.0497, 95% C.I.=1.002-13.110) predicted a less severe epilepsy phenotype.

CONCLUSIONS

Previous studies have only assessed patient cohorts with FCD and epilepsy, limiting the data on "asymptomatic" or "atypically presenting" FCD. Identifying a surprisingly large, novel cohort of children with FCD that had not developed epilepsy helps define prognosis and inform clinical management of children with FCD on imaging.

Seven tesla MRI improves detection of focal cortical dysplasia in patients with refractory focal epilepsy

Objective

The aim of this study is to determine whether the use of 7 tesla (T) MRI in clinical practice leads to higher detection rates of focal cortical dysplasias in possible candidates for epilepsy surgery.

Methods

In our center patients are referred for 7 T MRI if lesional focal epilepsy is suspected, but no abnormalities are detected at one or more previous, sufficient‐quality lower‐field MRI scans, acquired with a dedicated epilepsy protocol, or when concealed pathology is suspected in combination with MR‐visible mesiotemporal sclerosis—dual pathology. We assessed 40 epilepsy patients who underwent 7 T MRI for presurgical evaluation and whose scans (both 7 T and lower field) were discussed during multidisciplinary epilepsy surgery meetings that included a dedicated epilepsy neuroradiologist. We compared the conclusions of the multidisciplinary visual assessments of 7 T and lower‐field MRI scans.

Results

In our series of 40 patients, multidisciplinary evaluation of 7 T MRI identified additional lesions not seen on lower‐field MRI in 9 patients (23%). These findings were guiding in surgical planning. So far, 6 patients underwent surgery, with histological confirmation of focal cortical dysplasia or mild malformation of cortical development.

Significance

Seven T MRI improves detection of subtle focal cortical dysplasia and mild malformations of cortical development in patients with intractable epilepsy and may therefore contribute to identification of surgical candidates and complete resection of the epileptogenic lesion, and thus to postoperative seizure freedom.