Utility of MRI, PET, and ictal SPECT in presurgical evaluation of non-lesional pediatric epilepsy

Nuclear Medicine Imaging in Epilepsy

Approximately one-third of patients with focal epilepsy have medically refractory focal epilepsy (MRFE), which significantly impacts their quality of life. Once a seizure focus is identified and determined to be in the noneloquent cortex, it can be surgically resected with the goal of freedom from seizures and minimal neurocognitive deficit. During noninvasive (phase I) presurgical planning, functional (nuclear) imaging and structural imaging are complementary in the accurate localization of the epileptogenic zone (EZ). PET and SPECT are complementary functional imaging modalities. Fluorine 18-fluorodeoxyglucose PET shows hypometabolism in the EZ, while SPECT radiotracers are used to assess regional cerebral perfusion. Functional imaging plays a more important role in patients with nonlesional epilepsy (approximately one-third of patients with MRFE), in patients with multiple lesions, or in the setting of electrophysiologic-structural discordance. Nuclear medicine imaging also helps in evaluating the functional integrity of the rest of the brain and unmasking abnormalities that are not apparent at structural imaging before surgery. During invasive (phase II) evaluation, the EZ seen at functional imaging helps in guiding intracranial electrode placement. This review of nuclear medicine imaging of epilepsy is focused on the radiotracers used, imaging acquisition and postprocessing, commonly encountered causes of MRFE in adults and children, radiologic appearances of MRFE, imaging artifacts, and interpretation pitfalls. The goal is to guide radiologists in optimally performing and interpreting these studies for effective multidisciplinary discussions of these complex patient cases. ©RSNA, 2025 Supplemental material is available for this article.

Alterations in white matter integrity and correlations with clinical characteristics in children with non-lesional temporal lobe epilepsy

PURPOSE

To complement the current research on altered white matter integrity in children with non-lesional temporal lobe epilepsy (NL-TLE), especially the correlation between diffusion metrics and clinical characteristics, so as to provide imaging evidence for clinical practice.

METHODS

Children with temporal lobe epilepsy and no lesions on magnetic resonance imaging (MRI) were retrospectively collected from 2016.01.01 to 2022.12.31, and typically developing children (TDC) with normal MRI were collected as control group. Tract-based spatial statistics (TBSS) was used to compare the fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) between the two groups. Twenty fiber bundles were used as regions of interest (ROIs) to extract and compare the diffusion metrics. Partial correlation analysis was performed to assess the association between diffusion parameters within ROIs and clinical characteristics.

RESULTS

TBSS and ROI analysis showed that FA values decreased and MD and RD values increased in the NL-TLE compared with the TDC, without significant differences in AD values. FA values in all ROIs increased with age, while the MD and RD values decreased in all ROIs, and the AD values decreased in most ROIs. Epilepsy duration was negatively correlated with FA values and positively correlated with MD and RD values in specific fibers. Frequency of seizures was negatively correlated with the FA values in a few trats. Full-scale intelligence quotient (FSIQ) was positively correlated with FA values and negatively with RD value in a few tracts.

CONCLUSION

Children with NL-TLE showed widespread alterations in white matter integrity, which were correlated with clinical characteristics.

Associations Between Testing and Treatment Pathways in a Case of Pediatric Nonlesional Epilepsy: A Census Survey of NAEC Center Directors

OBJECTIVE

Epilepsy surgery is vital in managing of children with drug-resistant epilepsy. Noninvasive and invasive testing modalities allow for evaluation and treatment of children with drug-resistant epilepsy. Evidence-based algorithms for this process do not exist. This study examines expert response to a vignette of pediatric nonlesional epilepsy to assess associations in evaluation and treatment choices.

METHODS

We analyzed annual report data and an epilepsy practice survey reported in 2020 from 135 pediatric epilepsy center directors in the United States. Characteristics of centers along with noninvasive and invasive testing and surgical treatment strategies were collected. Multivariable logistic regression modeling was performed.

RESULTS

The response rate was 100% with 135 responses included in the analyses. Most used noninvasive testing modalities included Neuropsychology evaluation (90%), interictal brain fluorodeoxyglucose-positron emission tomography (85%), and functional magnetic resonance imaging (MRI) (72%) with nearly half obtaining genetic testing. Choosing functional MRI was associated with stereo electroencephalography (EEG) (P = .025) and selecting Wada with subdural grid/strips (P = .038). Directors from pediatric-only centers were more likely to choose stereo EEG as opposed to combined centers (P = .042). Laser interstitial thermal therapy was almost 7 times as likely to be chosen as a treatment modality compared with open resection in dedicated pediatric centers (OR 6.96, P = .002).

SIGNIFICANCE

In a vignette of nonlesional childhood drug-resistant epilepsy, epilepsy center directors' patterns of noninvasive testing, invasive testing, and treatment were examined. Management choices were associated with pediatric versus combined pediatric/adult center characteristics. Expert opinions demonstrated equipoise in evaluation and management of children with drug-resistant epilepsy and the need for evidence-based management strategies.

Advances in magnetic resonance imaging for the assessment of paediatric focal epilepsy: a narrative review

Background and Objective

Epilepsy affects approximately 50 million people worldwide, with 30-40% of patients not responding to medication, necessitating alternative therapies such as surgical intervention. However, the accurate localization of epileptogenic lesions, particularly in pediatric magnetic resonance imaging (MRI)-negative drug-resistant epilepsy, remains a challenge. This paper reviews advanced neuroimaging techniques aimed at improving the detection of such lesions to enhance surgical outcomes.

Methods

A comprehensive literature search was conducted using PubMed, focusing on advanced MRI sequences, focal epilepsy, and the integration of artificial intelligence (AI) in the diagnostic process.

Key Content and Findings

New MRI sequences, including magnetization prepared 2 rapid gradient echo (MP2RAGE), edge-enhancing gradient echo (EDGE), and fluid and white matter suppression (FLAWS), have demonstrated enhanced capabilities in detecting subtle epileptogenic lesions. Quantitative MRI techniques, notably magnetic resonance fingerprinting (MRF), alongside innovative post-processing methods, are emphasized for their effectiveness in delineating cortical malformations, whether used alone or in combination with ultra-high field MRI systems. Furthermore, the integration of AI in radiology is progressing, providing significant support in accurately localizing lesions, and potentially optimizing pre-surgical planning.

Conclusions

While advanced neuroimaging and AI offer significant improvements in the diagnostic process for epilepsy, some challenges remain. These include long acquisition times, the need for extensive data analysis, and a lack of large, standardized datasets for AI validation. However, the future holds promise as research continues to integrate these technologies into clinical practice. These efforts will improve the clinical applicability and effectiveness of these advanced techniques in epilepsy management, paving the way for more accurate diagnoses and better patient outcomes.

MEG in MRI-Negative Patients with Focal Epilepsy

OBJECTIVES

To review the evidence on the clinical value of magnetic source imaging (MSI) in patients with refractory focal epilepsy without evidence for an epileptogenic lesion on magnetic resonance imaging ("MRI-negative" or "non-lesional MRI").

METHODS

We conducted a systematic literature search on PUBMED, which was extended by researchrabbit.ai using predefined criteria to identify studies that applied MSI in MRI-negative patients with epilepsy. We extracted data on patient characteristics, MSI methods, localization results, surgical outcomes, and correlation with other modalities.

RESULTS

We included 23 studies with a total of 512 non-lesional epilepsy patients who underwent MSI. Most studies used equivalent current dipole (ECD) models to estimate the sources of interictal epileptic discharges (IEDs). MEG detected IEDs in 32-100% of patients. MSI results were concordant with other modalities, such as EEG, PET, and SPECT, in 3892% of cases. If MSI concordant surgery was performed, 52-89% of patients achieved seizure freedom. MSI contributed to the decision-making process in 28-75% of cases and altered the surgical plan in 5-33% of cases.

CONCLUSIONS

MSI is a valuable diagnostic tool for MRI-negative patients with epilepsy, as it can detect and localize IEDs with high accuracy and sensitivity, and provides useful information for surgical planning and predicts outcomes. MSI can also complement and refine the results of other modalities, such as EEG and PET, and optimize the use of invasive recordings. MSI should be considered as part of the presurgical evaluation, especially in patients with non-lesional refractory epilepsy.

Treatment odyssey to epilepsy surgery in children with focal cortical dysplasia: Risk factors for delayed surgical intervention

OBJECTIVE

To elucidate the patient's journey to epilepsy surgery and identify the risk factors contributing to surgical delay in pediatric patients with drug-resistant epilepsy (DRE) due to focal cortical dysplasia (FCD).

METHODS

A retrospective review was conducted of 93 pediatric patients who underwent curative epilepsy surgery for FCD between January 2012 and March 2023 at a tertiary epilepsy center. The Odyssey plot demonstrated the treatment process before epilepsy surgery, including key milestones of epilepsy onset, first hospital visit, epilepsy diagnosis, MRI diagnosis, DRE diagnosis, and surgery. The primary outcome was surgical delay; the duration from DRE to surgery. Multivariate linear regression models were used to examine the association between surgical delay and clinical, investigative, and treatment characteristics.

RESULTS

The median age at seizure onset was 1.3 years (interquartile range [IQR] 0.14-3.1), and at the time of surgery, it was 6 years (range 1-11). Notably, 46% experienced surgical delays exceeding two years. The Odyssey plot visually highlighted that surgical delay comprised a significant portion of the patient journey. Although most patients underwent MRI before referral, MRI abnormalities were identified before referral only in 39% of the prolonged group, compared to 70% of the non-prolonged group. Multivariate analyses showed that delayed notification of MRI abnormalities, longer duration from epilepsy onset to DRE, older age at onset, number of antiseizure medications tried, and moderate to severe intellectual disability were significantly associated with prolonged surgical delay.

CONCLUSION

Pediatric DRE patients with FCD experienced a long journey until surgery. Early and accurate identification of MRI abnormalities is important to minimize surgical delays.

Determinants of successful ictal SPECT injection in phase 1 epilepsy presurgical evaluation: Findings from the pediatric epilepsy research consortium surgery database project

OBJECTIVES

The main goal of presurgical evaluation in drug-resistant focal epilepsy is to identify a seizure onset zone (SOZ). Of the noninvasive, yet resource-intensive tests available, ictal single-photon emission computed tomography (SPECT) aids SOZ localization by measuring focal increases in blood flow within the SOZ via intravenous peri-ictal radionuclide administration. Recent studies indicate that geographic and center-specific factors impact utilization of these diagnostic procedures. Our study analyzed successful ictal SPECT acquisition (defined as peri-ictal injection during inpatient admission) using surgery-related data from the Pediatric Epilepsy Research Consortium (PERC) surgery database. We hypothesized that a high seizure burden, longer duration of video EEG monitoring (VEEG), and more center-specific hours of SPECT availability would increase the likelihood of successful ictal SPECT.

METHODS

We identified study participants (≤18 years of age) who underwent SPECT as part of their phase 1 VEEG from January 2018 to June 2022. We assessed association between ictal SPECT outcomes (success vs. failure) and variables including patient demographics, epilepsy history, and center-specific SPECT practices.

RESULTS

Phase 1 VEEG monitoring with ictal SPECT injection was planned in 297 participants and successful in 255 participants (85.86%). On multivariable analysis, the likelihood of a successful SPECT injection was higher in patients of non-Hispanic ethnicity (p = 0.040), shorter duration VEEG (p = 0.004), and higher hours of available SPECT services (p < 0.001). Higher seizure frequency (p = 0.033) was significant only in bivariate analysis. Patients treated at centers with more operational hours were more likely to experience pre-admission protocols prior to VEEG (p = 0.002).

SIGNIFICANCE

There is inter-center variability in protocols and SPECT acquisition capabilities. Shorter duration of EEG monitoring, non-Hispanic ethnicity (when on private insurance), extended operational hours of nuclear medicine as noted on multivariate analysis and higher seizure frequency in bivariate analysis are strongly associated with successful ictal SPECT injection.

PLAIN LANGUAGE SUMMARY

In pediatric patients with drug-resistant epilepsy, single-photon emission computed tomography (SPECT) scans can be helpful in localizing seizure onset zone. However, due to many logistical challenges described below, which include not only the half-life of the technetium isotope used to inject intravenously during a seizure (called the ictal SPECT scan) but also available nuclear scanner time in addition to the unpredictability of seizures, obtaining an ictal SPECT during a planned elective inpatient hospital stay is not guaranteed. Thus, as healthcare costs increase, planning a prolonged hospital stay during which an ictal SPECT scan is not feasible is not optimal. We leveraged our prospective surgery database to look at center-specific factors and patient-specific factors associated with an ictal SPECT injection in the first, pediatric-focussed, large-scale, multicenter, prospective, SPECT feasibility study. We found that longer availability of the scanner is the most important center-specific factor in assuring ictal SPECT injection. Although seizure frequency is an important patient-specific factor on bivariate analysis, this factor lost statistical significance when other factors like patient insurance status and video EEG duration were also considered in our multivariable logistical model.

Unraveling the Neural Circuits: Techniques, Opportunities and Challenges in Epilepsy Research

Epilepsy, a prevalent neurological disorder characterized by high morbidity, frequent recurrence, and potential drug resistance, profoundly affects millions of people globally. Understanding the microscopic mechanisms underlying seizures is crucial for effective epilepsy treatment, and a thorough understanding of the intricate neural circuits underlying epilepsy is vital for the development of targeted therapies and the enhancement of clinical outcomes. This review begins with an exploration of the historical evolution of techniques used in studying neural circuits related to epilepsy. It then provides an extensive overview of diverse techniques employed in this domain, discussing their fundamental principles, strengths, limitations, as well as their application. Additionally, the synthesis of multiple techniques to unveil the complexity of neural circuits is summarized. Finally, this review also presents targeted drug therapies associated with epileptic neural circuits. By providing a critical assessment of methodologies used in the study of epileptic neural circuits, this review seeks to enhance the understanding of these techniques, stimulate innovative approaches for unraveling epilepsy's complexities, and ultimately facilitate improved treatment and clinical translation for epilepsy.

Effects of inverse methods and spike phases on interictal high-density EEG source reconstruction

OBJECTIVE

To determine the effect of inverse methods and timepoints of interictal epileptic discharges (IEDs) used for high-density electric source imaging (hd-ESI) in pharmacoresistant focal epilepsies.

METHODS

We retrospectively evaluated the hd-ESI and [18F]fluorodeoxyglucose positron emission tomography (18FDG-PET) of 21 operated patients with pharmacoresistant focal epilepsy (Engel I). Volumetric hd-ESI was performed with three different inverse methods such as the inverse solution linearly constrained minimum variance (LCMV, a beamformer method), standardized low resolution electromagnetic tomography (sLORETA) and weighted minimum-norm estimation (wMNE) and at different IED phases. Hd-ESI accuracy was determined by volumetric overlap and distance between hd-ESI source maximum, as well as 18FDG-PET hypometabolic region relative to the resection zone (RZ).

RESULTS

In our cohort, the shortest distances and greatest volumetric overlaps to the RZ were found in the half-rise and peak-phase for all inverse methods. The distance to the RZ was not different between the centroid of the clinical hypothesis-based cluster and the source maximum in peak-phase. However, the distance of the hypothesis-based cluster was significantly shorter compared to the cluster selected by the smallest p-value.

CONCLUSIONS

Hd-ESI provides the greatest accuracy in determining the RZ at the IED half-rise and peak-phase for all applied inverse methods, whereby sLORETA and LCMV were equally accurate.

SIGNIFICANCE

Our results offer guidance in selecting inverse methods and IED phases for hd-ESI, compare the performance of hd-ESI and 18FDG-PET and encourage future studies in investigating the relationship between interictal ESI and 18FDG-PET hypometabolism.

Neurosurgical robots in China: State of the art and future prospect

Neurosurgical robots have developed for decades and can effectively assist surgeons to carry out a variety of surgical operations, such as biopsy, stereo-electroencephalography (SEEG), deep brain stimulation (DBS), and so forth. In recent years, neurosurgical robots in China have developed rapidly. This article will focus on several key skills in neurosurgical robots, such as medical imaging systems, automatic manipulator, lesion localization techniques, multimodal image fusion technology, registration method, and vascular imaging technology; introduce the clinical application of neurosurgical robots in China, and look forward to the potential improvement points in the future based on our experience and research in the field.

Epileptic EEG Signal Detection Using Variational Modal Decomposition and Improved Grey Wolf Algorithm

Epilepsy does great harm to the human body, and even threatens human life when it is serious. Therefore, research focused on the diagnosis and treatment of epilepsy holds paramount clinical significance. In this paper, we utilized variational modal decomposition (VMD) and an enhanced grey wolf algorithm to detect epileptic electroencephalogram (EEG) signals. Data were extracted from each patient's preseizure period and seizure period of 200 s each, with every 2 s as a segment, meaning 100 data points could be obtained for each patient's health period as well as 100 data points for each patient's epilepsy period. Variational modal decomposition (VMD) was used to obtain the corresponding intrinsic modal function (VMF) of the data. Then, the differential entropy (DE) and high frequency detection (HFD) of each VMF were extracted as features. The improved grey wolf algorithm is adopted for a selected channel to improve the maximum value of the channel. Finally, the EEG signal samples were classified using a support vector machine (SVM) classifier to achieve the accurate detection of epilepsy EEG signals. Experimental results show that the accuracy, sensitivity and specificity of the proposed method can reach 98.3%, 98.9% and 98.5%, respectively. The proposed algorithm in this paper can be used as an index to detect epileptic seizures and has certain guiding significance for the early diagnosis and effective treatment of epileptic patients.

PET/MRI Applications in Pediatric Epilepsy

Epilepsy neuroimaging assessment requires exceptional anatomic detail, physiologic and metabolic information. Magnetic resonance (MR) protocols are often time-consuming necessitating sedation and positron emission tomography (PET)/computed tomography (CT) comes with a significant radiation dose. Hybrid PET/MRI protocols allow for exquisite assessment of brain anatomy and structural abnormalities, in addition to metabolic information in a single, convenient imaging session, which limits radiation dose, sedation time, and sedation events. Brain PET/MRI has proven especially useful for accurate localization of epileptogenic zones in pediatric seizure cases, providing critical additional information and guiding surgical decision making in medically refractory cases. Accurate localization of seizure focus is necessary to limit the extent of the surgical resection, preserve healthy brain tissue, and achieve seizure control. This review provides a systematic overview with illustrative examples demonstrating the applications and diagnostic utility of PET/MRI in pediatric epilepsy.

Clinical added value of interictal automated electrical source imaging in the presurgical evaluation of MRI-negative epilepsy: A real-life experience in 29 consecutive patients

OBJECTIVE

During the presurgical evaluation, manual electrical source imaging (ESI) provides clinically useful information in one-third of the patients but it is time-consuming and requires specific expertise. This prospective study aims to assess the clinical added value of a fully automated ESI analysis in a cohort of patients with MRI-negative epilepsy and describe its diagnostic performance, by evaluating sublobar concordance with stereo-electroencephalography (SEEG) results and surgical resection and outcome.

METHODS

All consecutive patients referred to the Center for Refractory Epilepsy (CRE) of St-Luc University Hospital (Brussels, Belgium) for presurgical evaluation between 15/01/2019 and 31/12/2020 meeting the inclusion criteria, were recruited to the study. Interictal ESI was realized on low-density long-term EEG monitoring (LD-ESI) and, whenever available, high-density EEG (HD-ESI), using a fully automated analysis (Epilog PreOp, Epilog NV, Ghent, Belgium). The multidisciplinary team (MDT) was asked to formulate hypotheses about the epileptogenic zone (EZ) location at sublobar level and make a decision on further management for each patient at two distinct moments: i) blinded to ESI and ii) after the presentation and clinical interpretation of ESI. Results leading to a change in clinical management were considered contributive. Patients were followed up to assess whether these changes lead to concordant results on stereo-EEG (SEEG) or successful epilepsy surgery.

RESULTS

Data from all included 29 patients were analyzed. ESI led to a change in the management plan in 12/29 patients (41%). In 9/12 (75%), modifications were related to a change in the plan of the invasive recording. In 8/9 patients, invasive recording was performed. In 6/8 (75%), the intracranial EEG recording confirmed the localization of the ESI at a sublobar level. So far, 5/12 patients, for whom the management plan was changed after ESI, were operated on and have at least one-year postoperative follow-up. In all cases, the EZ identified by ESI was included in the resection zone. Among these patients, 4/5 (80%) are seizure-free (ILAE 1) and one patient experienced a seizure reduction of more than 50% (ILAE 4).

CONCLUSIONS

In this single-center prospective study, we demonstrated the added value of automated ESI in the presurgical evaluation of MRI-negative cases, especially in helping to plan the implantation of depth electrodes for SEEG, provided that ESI results are integrated into the whole multimodal evaluation and clinically interpreted.

EEG Correlates of Qualitative Hypermetabolic FDG-PET in Patients With Neurologic Disorders

Background and Objectives

Case reports and case series have described fluorodeoxyglucose (FDG)-PET findings in critically ill patients with rhythmic or periodic EEG patterns, with one reporting that metabolic activity increases with increasing lateralized periodic discharge (LPD) frequency. However, larger studies examining the relationship between FDG-PET hypermetabolism and rhythmic or periodic EEG patterns are lacking. The goal of this study was to investigate the association of FDG-PET hypermetabolism with electroencephalographic features in patients with neurologic disorders.

Methods

This was a single-center, retrospective study of adult patients admitted with acute neurologic symptoms who underwent FDG-PET imaging and EEG monitoring within 24 hours. Subjects were divided into 2 groups based on their FDG-PET metabolism pattern: hypermetabolic activity vs hypometabolic or normal metabolic activity. Chi-square tests and logistic regression were used to determine the relationship of FDG-PET metabolism and EEG findings.

Results

Sixty patients met the inclusion criteria and underwent 63 FDG-PET studies and EEGs. Twenty-seven studies (43%) showed hypermetabolism while 36 studies (57%) showed either hypometabolism or no abnormalities on FDG-PET. Subjects with hypermetabolic FDG-PET were more likely to have electrographic seizures (44% vs 8%, p = 0.001) and LPDs with/without seizures (44% vs 14%, p = 0.007), but not other rhythmic or periodic EEG patterns (lateralized rhythmic delta activity, generalized periodic discharges, or generalized rhythmic delta activity). Subjects with hypermetabolism and LPDs were more likely to have concurrent electrographic seizures (58% vs 0%, p = 0.03), fast activity associated with the discharges (67% vs 0, p = 0.01), or spike morphology (67% vs 0, p = 0.03), compared with subjects with hypometabolic FDG-PET and LPDs.

Discussion

Adults admitted with acute neurologic symptoms who had hypermetabolic FDG-PET were more likely to show electrographic seizures and LPDs, but not other rhythmic or periodic EEG patterns, compared with those with hypometabolic FDG-PET. Subjects with hypermetabolic FDG-PET and LPDs were more likely to have LPDs with concurrent electrographic seizures, LPDs with a spike morphology, and LPDs +F, compared with subjects with hypometabolic FDG-PET.

The diagnostic value of ictal SPECT-A retrospective, semiquantitative monocenter study

OBJECTIVE

Ictal single photon emission computed tomography (SPECT) can be used as an advanced diagnostic modality to detect the seizure onset zone in the presurgical evaluation of people with epilepsy. In addition to visual assessment (VSA) of ictal and interictal SPECT images, postprocessing methods such as ictal-interictal SPECT analysis using SPM (ISAS) can visualize regional ictal blood flow differences. We aimed to evaluate and differentiate the diagnostic value of VSA and ISAS in the Bonn cohort.

METHODS

We included 161 people with epilepsy who underwent presurgical evaluation at the University Hospital Bonn between 2008 and 2020 and received ictal and interictal SPECT and ISAS. We retrospectively assigned SPECT findings to one of five categories according to their degree of concordance with the clinical focus hypothesis.

RESULTS

Seizure onset zones could be identified more likely on a sublobar concordance level by ISAS than by VSA (31% vs. 19% of cases; OR = 1.88; 95% Cl [1.04, 3.42]; P = 0.03). Both VSA and ISAS more often localized a temporal seizure onset zone than an extratemporal one. Neither VSA nor ISAS findings were predicted by the latency between seizure onset and tracer injection (P = 0.75). In people who underwent successful epilepsy surgery, VSA and ISAS indicated the correct resection site in 54% of individuals, while MRI and EEG showed the correct resection localization in 96% and 33% of individuals, respectively. It was more likely to become seizure-free after epilepsy surgery if ISAS or VSA had been successful. There was no MR-negative case with successful surgery, indicating that ictal SPECT is more useful for confirmation than for localization.

SIGNIFICANCE

The results of the most extensive clinical study of ictal SPECT to date allow an assessment of the diagnostic value of this elaborate examination and emphasize the importance of postprocessing routines.

Neurological update: structural and functional imaging in epilepsy surgery

Structural and functional imaging prior to surgery in drug-resistant focal epilepsy, has an important role to play alongside electroencephalography (EEG) techniques, in planning the surgical approach and predicting post-operative outcome. This paper reviews the role of structural and functional imaging of the brain, namely computed tomography (CT), magnetic resonance imaging (MRI), functional MRI (fMRI), single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging in the preoperative work-up of people with medically refractory epilepsy. In MRI-negative patients, the precise localisation of the epileptogenic zone may be established by demonstrating hypometabolism on PET imaging or hyperperfusion on SPECT imaging in the area surrounding the seizure focus. These imaging modalities are far less invasive than intracranial EEG, which is the gold standard but requires surgical placement of electrodes or recording grids. Even when intracranial EEG is needed, PET or SPECT imaging can assist in the planning of EEG electrode placement, due to its' limited spatial sampling. Multimodal imaging techniques now allow the multidisciplinary epilepsy surgery team to identify and better characterise focal pathology, determine its' relationship to eloquent areas of the brain and the degree of interconnectedness within both physiological and pathological networks, as well as improve planning and surgical outcomes for patients. This paper will update the reader on this whole field and provide them with a practical guide, to aid them in the selection of appropriate investigations, interpretation of the findings and facilitating patient discussions in individuals with drug-resistant focal epilepsy.

Epilepsy center characteristics and geographic region influence presurgical testing in the United States

OBJECTIVE

Persons with drug-resistant epilepsy may benefit from epilepsy surgery and should undergo presurgical testing to determine potential candidacy and appropriate intervention. Institutional expertise can influence use and availability of evaluations and epilepsy surgery candidacy. This census survey study aims to examine the influence of geographic region and other center characteristics on presurgical testing for medically intractable epilepsy.

METHODS

We analyzed annual report and supplemental survey data reported in 2020 from 206 adult epilepsy center directors and 136 pediatric epilepsy center directors in the United States. Test utilization data were compiled with annual center volumes, available resources, and US Census regional data. We used Wilcoxon rank-sum, Kruskal-Wallis, and chi-squared tests for univariate analysis of procedure utilization. Multivariable modeling was also performed to assign odds ratios (ORs) of significant variables.

RESULTS

The response rate was 100% with individual element missingness < 11% across 342 observations undergoing univariate analysis. A total of 278 complete observations were included in the multivariable models, and significant regional differences were present. For instance, compared to centers in the South, those in the Midwest used neuropsychological testing (OR = 2.87, 95% confidence interval [CI] = 1.2-6.86; p = .018) and fluorodeoxyglucose-positron emission tomography (OR = 2.74, 95% CI = = 1.14-6.61; p = .025) more commonly. For centers in the Northeast (OR = .46, 95% CI = .23-.93; p = .031) and West (OR = .41, 95% CI = .19-.87; p = .022), odds of performing single-photon emission computerized tomography were lower by nearly 50% compared to those in the South. Center accreditation level, demographics, volume, and resources were also associated with varying individual testing rates.

SIGNIFICANCE

Presurgical testing for drug-resistant epilepsy is influenced by US geographic region and other center characteristics. These findings have potential implications for comparing outcomes between US epilepsy centers and may inject disparities in access to surgical treatment.

Potential new roles for glycogen in epilepsy

Seizures often originate in epileptogenic foci. Between seizures (interictally), these foci and some of the surrounding tissue often show low signals with 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) in many epileptic patients, even when there are no radiologically detectable structural abnormalities. Low FDG-PET signals are thought to reflect glucose hypometabolism. Here, we review knowledge about metabolism of glucose and glycogen and oxidative stress in people with epilepsy and in acute and chronic rodent seizure models. Interictal brain glucose levels are normal and do not cause apparent glucose hypometabolism, which remains unexplained. During seizures, high amounts of fuel are needed to satisfy increased energy demands. Astrocytes consume glycogen as an additional emergency fuel to supplement glucose during high metabolic demand, such as during brain stimulation, stress, and seizures. In rodents, brain glycogen levels drop during induced seizures and increase to higher levels thereafter. Interictally, in people with epilepsy and in chronic epilepsy models, normal glucose but high glycogen levels have been found in the presumed brain areas involved in seizure generation. We present our new hypothesis that as an adaptive response to repeated episodes of high metabolic demand, high interictal glycogen levels in epileptogenic brain areas are used to support energy metabolism and potentially interictal neuronal activity. Glycogenolysis, which can be triggered by stress or oxidative stress, leads to decreased utilization of plasma glucose in epileptogenic brain areas, resulting in low FDG signals that are related to functional changes underlying seizure onset and propagation. This is (partially) reversible after successful surgery. Last, we propose that potential interictal glycogen depletion in epileptogenic and surrounding areas may cause energy shortages in astrocytes, which may impair potassium buffering and contribute to seizure generation. Based on these hypotheses, auxiliary fuels or treatments that support glycogen metabolism may be useful to treat epilepsy.

The Noninvasive Evaluation for Minimally Invasive Pediatric Epilepsy Surgery (MIPES): A Multimodal Exploration of the Localization-Based Hypothesis

Minimally invasive pediatric epilepsy surgery (MIPES) is a rising technique in the management of focal-onset drug-refractory epilepsy. Minimally invasive surgical techniques are based on small, focal interventions (such as parenchymal ablation or localized neuromodulation) leading to elimination of the seizure onset zone or interruption of the larger epileptic network. Precise localization of the seizure onset zone, demarcation of eloquent cortex, and mapping of the network leading to seizure propagation are required to achieve optimal outcomes. The toolbox for presurgical, noninvasive evaluation of focal epilepsy continues to expand rapidly, with a variety of options based on advanced imaging and electrophysiology. In this article, we will examine several of these diagnostic modalities from the standpoint of MIPES and discuss how each can contribute to the development of a localization-based hypothesis for potential surgical targets.

Multimodal combination of neuroimaging methods for localizing the epileptogenic zone in MR-negative epilepsy

The objective was to determine the optimal combination of multimodal imaging methods (IMs) for localizing the epileptogenic zone (EZ) in patients with MR-negative drug-resistant epilepsy. Data from 25 patients with MR-negative focal epilepsy (age 30 ± 10 years, 16M/9F) who underwent surgical resection of the EZ and from 110 healthy controls (age 31 ± 9 years; 56M/54F) were used to evaluate IMs based on 3T MRI, FDG-PET, HD-EEG, and SPECT. Patients with successful outcomes and/or positive histological findings were evaluated. From 38 IMs calculated per patient, 13 methods were selected by evaluating the mutual similarity of the methods and the accuracy of the EZ localization. The best results in postsurgical patients for EZ localization were found for ictal/ interictal SPECT (SISCOM), FDG-PET, arterial spin labeling (ASL), functional regional homogeneity (ReHo), gray matter volume (GMV), cortical thickness, HD electrical source imaging (ESI-HD), amplitude of low-frequency fluctuation (ALFF), diffusion tensor imaging, and kurtosis imaging. Combining IMs provides the method with the most accurate EZ identification in MR-negative epilepsy. The PET, SISCOM, and selected MRI-post-processing techniques are useful for EZ localization for surgical tailoring.

High density electric source imaging in childhood-onset epilepsy due to focal cortical dysplasia

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ESI with 64 electrodes allows accurate localization of the epileptogenic area in patients with FCD.

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Concordant results with other imaging techniques is associated with excellent outcome.

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ESI should become a standard imaging tool in pediatric surgical candidates with FCD.

Objective

The goal of this study was to investigate the diagnostic utility of electric source imaging (ESI) in the presurgical evaluation of children with focal cortical dysplasia (FCD) and to compare it with other imaging techniques.

Methods

Twenty patients with epilepsy onset before 18 years, surgically treated focal epilepsy with a minimal follow-up of 2 years, and histologically proven FCD were retrospectively selected. All patients underwent MRI, positron emission tomography (PET), and 16 patients also had ictal single-photon emission computed tomography (iSPECT). ESI, using EEG with 64 electrodes or more (HD-ESI), was performed in all 20 patients. We determined sensitivity, specificity and accuracy of ESI, and compared its yield to that of other imaging techniques.

Results

Twelve patients were seizure-free post-operatively (60%). Among all patients, highest localization accuracy (80%) was obtained with ESI, followed by PET and iSPECT (75%). When results from ESI and SPECT were concordant 100% of patients achieved Engel I outcome. If ESI and PET showed concordant localization, 90% of patients achieved postoperative seizure freedom.

Conclusions

Our findings demonstrate that HD-ESI allows accurate localization of the epileptogenic zone in patients with FCD.

Significance

In combination with other imaging modalities, ESI helps with planning a more accurate surgery and therefore, the chances of postoperative seizure control are higher. Since it is based on EEG recordings, it does not require sedation, which is particularly interesting in pediatric patients. ESI represents an important imaging tool in focal epilepsies due to cortical dysplasia, which might be difficult to detect on standard imaging.

Application of Three-Dimensional Pseudocontinuous Arterial Spin Labeling Perfusion Imaging in the Brains of Children With Autism

Objective

To explore the application of three-dimensional pseudocontinuous arterial spin labeling (3D-PCASL) perfusion imaging in the brains of children with autism and to understand the characteristics of cerebral blood perfusion in children with autism.

Methods

A total of 320 children with autism (160 men and 160 women) aged between 2 and 18 years and 320 age- and sex-matched healthy children participated in the study. All children were scanned by 3.0 T magnetic resonance axial T1 fluid-attenuated inversion recovery (FLAIR), T2 FLAIR, 3D-T1, and 3D-PCASL sequences. After postprocessing, cerebral blood flow (CBF) values in each brain region of children with autism and healthy children at the same age were compared and analyzed. Furthermore, CBF characteristics in each brain region of autistic children at various ages were determined.

Results

The CBF values of the frontal lobe, hippocampus, temporal lobe, and caudate nucleus of children with autism are lower than those of healthy children (P < 0.05). Additionally, as the ages of children with autism increase, the number of brain regions with decreased CBF values gradually increases. A receiver operating characteristic (ROC) analysis results show that the CBF values of the frontal lobe, hippocampus, temporal lobe, and caudate nucleus can distinguish children with autism [area under the ROC curve (AUC) > 0.05, P < 0.05].

Conclusion

The 3D-PCASL shows lower brain CBF values in children with autism.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier: ChiCTR2000034356.

Morphometric analysis program and quantitative positron emission tomography in presurgical localization in MRI-negative epilepsies: a simultaneous PET/MRI study

PURPOSE

To evaluate morphometric analysis program (MAP) and quantitative positron emission tomography (QPET) in epileptogenic zone (EZ) identification using a simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) system in MRI-negative epilepsies.

METHODS

Seventy-one localization-related MRI-negative epilepsies who underwent preoperative simultaneous PET/MRI examination and surgical resection were enrolled retrospectively. MAP was performed on a T1-weighted volumetric sequence, and QPET was analyzed using statistical parametric mapping (SPM) with comparison to age- and gender-matched normal controls. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MAP, QPET, MAP + QPET, and MAP/QPET in EZ localization were assessed. The correlations between surgical outcome and modalities concordant with cortical resection were analyzed.

RESULTS

Forty-five (63.4%) patients had Engel I seizure outcomes. The sensitivity, specificity, PPV, and NPV of MAP were 64.4%, 69.2%, 78.3%, and 52.9%, respectively. The sensitivity, specificity, PPV, NPV of QPET were 73.3%, 65.4%, 78.6%, and 58.6%, respectively. MAP + QPET, defined as two tests concordant with cortical resection, had reduced sensitivity (53.3%) but increased specificity (88.5%) relative to individual tests. MAP/QPET, defined as one or both tests concordant with cortical resection, had increased sensitivity (86.7%) but reduced specificity (46.2%) relative to individual tests. The regions determined by MAP, QPET, MAP + QPET, or MAP/QPET concordant with cortical resection were significantly associated with the seizure-free outcome.

CONCLUSION

QPET has a superior sensitivity than MAP, while the combined MAP + QPET obtained from a simultaneous PET/MRI scanner may improve the specificity of the diagnostic tests in EZ localization coupled with the preferable surgical outcome in MRI-negative epilepsies.

Machine learning applications on neuroimaging for diagnosis and prognosis of epilepsy: A review

Machine learning is playing an increasingly important role in medical image analysis, spawning new advances in the clinical application of neuroimaging. There have been some reviews on machine learning and epilepsy before, and they mainly focused on electrophysiological signals such as electroencephalography (EEG) and stereo electroencephalography (SEEG), while neglecting the potential of neuroimaging in epilepsy research. Neuroimaging has its important advantages in confirming the range of the epileptic region, which is essential in presurgical evaluation and assessment after surgery. However, it is difficult for EEG to locate the accurate epilepsy lesion region in the brain. In this review, we emphasize the interaction between neuroimaging and machine learning in the context of epilepsy diagnosis and prognosis. We start with an overview of epilepsy and typical neuroimaging modalities used in epilepsy clinics, MRI, DWI, fMRI, and PET. Then, we elaborate two approaches in applying machine learning methods to neuroimaging data: (i) the conventional machine learning approach combining manual feature engineering and classifiers, (ii) the deep learning approach, such as the convolutional neural networks and autoencoders. Subsequently, the application of machine learning on epilepsy neuroimaging, such as segmentation, localization, and lateralization tasks, as well as tasks directly related to diagnosis and prognosis are looked into in detail. Finally, we discuss the current achievements, challenges, and potential future directions in this field, hoping to pave the way for computer-aided diagnosis and prognosis of epilepsy.

Pediatric Epilepsy Surgery: Indications and Evaluation

Epilepsy is a common neurological condition in children. It is usually amenable to drug therapy. However, nearly one-third of patients may be refractory to antiseizure drugs. Poor compliance and nonepileptic events should be ruled out as possible causes of drug-resistant epilepsy (DRE). After failing adequate trials of two appropriate antiseizure drugs, patients with focal DRE or poorly classifiable epilepsy or epileptic encephalopathy with focal electro-clinical features should be worked up for surgical candidacy. A randomized controlled trial provided a class I evidence for epilepsy surgery in pediatric DRE. Pre-surgical screening workup typically includes a high-resolution epilepsy protocol brain magnetic resonance imaging (MRI) and a high-quality in-patient video electroencephalography evaluation. Advanced investigations such as positron emission tomography (PET), single-photon emission computed tomography (SPECT), and magnetoencephalography (MEG) may be required in selected cases especially when brain MRI is normal, and further evidence for anatomo-electro-clinical concordance is necessary to refine candidacy for surgery and surgical strategy. Some children may also need functional MRI to map eloquent regions of interest such as motor, sensory, and language functions to avoid unacceptable neurological deficits after surgery. Selected children may need invasive long-term electroencephalographic monitoring using stereotactically implanted intracranial depth electrodes or subdural grids. Surgical options include resective surgeries (lesionectomy, lobectomy, multilobar resections) and disconnective surgeries (corpus callosotomy, etc.) with the potential to obtain seizure freedom. Other surgical procedures, typically considered to be palliative are neuromodulation [deep brain stimulation (DBS), vagal nerve stimulation (VNS), and responsive neural stimulation (RNS)]. DBS and RNS are currently not approved in children. Pediatric DRE should be evaluated early considering the risk of epileptic encephalopathy and negative impact on cognition.

Underrepresented Populations in Pediatric Epilepsy Surgery

As awareness of pediatric epilepsy increases, accompanied by advancements in technology and research, it is important to identify certain types of patients that are overlooked for surgical management of epilepsy. Identifying these populations will allow us to study and elucidate the factors contributing to the underutilization and/or delayed application of surgical interventions. Demographically, African-American and Hispanic patients, as well as patients of certain Asian ethnicities, have relatively lower rates of undergoing epilepsy surgery than non-Hispanic and white patients. Among patients with epilepsy, those with higher odds of seizure-freedom following surgery are more likely to be referred for surgical evaluation by their neurologists, with the most common diagnosis being lesional focal epilepsy. However, patients with multifocal or generalized epilepsy, genetic etiologies, or normal (non-lesional) brain magnetic resonance imaging (MRI) are less likely be to referred for evaluation for resective surgery. With an increasing number of high-quality imaging modalities to help localize the epileptogenic zone as well as new techniques for both curative and palliative epilepsy surgery, there are very few populations of patients and/or types of epilepsy that should be precluded from evaluation to determine the suitability of epilepsy surgery. Ultimately, a clearer understanding of the populations who are underrepresented among those considered for epilepsy surgery, coupled with further study of the underlying reasons for this trend, will lead to less disparity in access to this critical treatment among patients with epilepsy.

Frontal lobe hypometabolism associated with Sudden Unexpected Death in Epilepsy (SUDEP) risk: An objective PET study

OBJECTIVE

Abnormalities of brain structures and neuronal networks have been identified in MRI studies of patients with Sudden Unexpected Death in Epilepsy (SUDEP) as well as in those at elevated risk. The goal of this study was to identify common patterns of objectively detected brain glucose metabolic abnormalities associated with SUDEP patients and those at high SUDEP risk.

METHODS

Patients with refractory epilepsy (n = 78, age: 16-61 years, 44 females), who underwent comprehensive presurgical evaluation, were assessed for their risk of SUDEP using the revised SUDEP-7 inventory. From the 57 patients with low SUDEP risk, 35 were selected to match their demographic and clinical characteristics to those with high SUDEP risk (n = 21). [¹⁸F]fluoro-deoxy-glucose positron emission tomography (FDG-PET) abnormalities were evaluated in the high- and low-SUDEP risk subgroups compared to FDG-PET scans of a healthy adult control group using statistical parametric mapping (SPM). Individual FDG-PET scans of 4 additional patients, who died from SUDEP, were also analyzed by SPM.

RESULTS

Mean SUDEP-7 score was 6.1 in the high and 2.7 in the low SUDEP risk group. MRI showed no lesion in 36 patients (64%). Statistical parametric mapping analysis of the high SUDEP risk subgroup showed bilateral medial frontal and inferior frontal hypometabolism as a common pattern. The low-risk group showed no specific common metabolic abnormalities on SPM group analysis. Individual PET scans of all 4 patients who died from SUDEP also showed bilateral frontal lobe hypometabolism.

CONCLUSIONS

These data show that bilateral frontal lobe involvement on FDG-PET, especially the medial and inferior frontal cortex, may be a common metabolic pattern associated with high SUDEP risk and SUDEP itself, in patients with refractory focal epilepsy.

Advances in Epilepsy Surgery

BACKGROUND

A large number of patients have epilepsy that is intractable and adversely affects a child's lifelong experience with addition societal burden that is disabling and expensive. The last two decades have seen a major explosion of new antiseizure medication options. Despite these advances, children with epilepsy continue to have intractable seizures. An option that has been long available but little used is epilepsy surgery to control intractable epilepsy.

METHODS

This article is a review of the literature as well as published opinions.

RESULTS

Epilepsy surgery in pediatrics is an underused modality to effectively treat children with epilepsy. Adverse effects of medication should be weighed against risks of surgery as well as risks of nonefficacy.

CONCLUSIONS

We discuss an approach to selecting the appropriate pediatric patient for consideration, a detailed evaluation including necessary evaluation, and the creation of an algorithm to approach patients with both generalized and focal epilepsy. We then discuss surgical options available including outcome data. New modalities are also addressed including high-frequency ultrasound and co-registration techniques including magnetic resonance imaging-guided laser therapy.

Advances in Brain Imaging Techniques for Patients With Intractable Epilepsy

Intractable epilepsy, also known as drug resistance or refractory epilepsy, is a major problem affecting nearly one-third of epilepsy patients. Surgical intervention could be an option to treat these patients. Correct identification and localization of epileptogenic foci is a crucial preoperative step. Some of these patients, however, have no abnormality on routine magnetic resonance imaging (MRI) of the brain. Advanced imaging techniques, therefore, can be helpful to identify the area of concern. Moreover, a clear delineation of certain anatomical brain structures and their relation to the surgical lesion or the surgical approach is essential to avoid postoperative complications, and advanced imaging techniques can be very helpful. In this review, we discuss and highlight the use of advanced imaging techniques, particularly positron emission tomography (PET)–MRI, single-photon emission computed tomography, functional MRI, and diffusion tensor imaging–tractography for the preoperative assessment of epileptic patients.

Consensus Statement for the Management and Treatment of Sturge-Weber Syndrome: Neurology, Neuroimaging, and Ophthalmology Recommendations

BACKGROUND

Sturge-Weber syndrome (SWS) is a sporadic, neurocutaneous syndrome involving the skin, brain, and eyes. Because of the variability of the clinical manifestations and the lack of prospective studies, consensus recommendations for management and treatment of SWS have not been published.

OBJECTIVE

This article consolidates the current literature with expert opinion to make recommendations to guide the neuroimaging evaluation and the management of the neurological and ophthalmologic features of SWS.

METHODS

Thirteen national peer-recognized experts in neurology, radiology, and ophthalmology with experience treating patients with SWS were assembled. Key topics and questions were formulated for each group and included (1) risk stratification, (2) indications for referral, and (3) optimum treatment strategies. An extensive PubMed search was performed of English language articles published in 2008 to 2018, as well as recent studies identified by the expert panel. The panel made clinical practice recommendations.

CONCLUSIONS

Children with a high-risk facial port-wine birthmark (PWB) should be referred to a pediatric neurologist and a pediatric ophthalmologist for baseline evaluation and periodic follow-up. In newborns and infants with a high-risk PWB and no history of seizures or neurological symptoms, routine screening for brain involvement is not recommended, but brain imaging can be performed in select cases. Routine follow-up neuroimaging is not recommended in children with SWS and stable neurocognitive symptoms. The treatment of ophthalmologic complications, such as glaucoma, differs based on the age and clinical presentation of the patient. These recommendations will help facilitate coordinated care for patients with SWS and may improve patient outcomes.

Searching for a paradigm shift in the research on the epilepsies and associated neuropsychiatric comorbidities. From ancient historical knowledge to the challenge of contemporary systems complexity and emergent functions

In this review, we will discuss in four scenarios our challenges to offer possible solutions for the puzzle associated with the epilepsies and neuropsychiatric comorbidities. We need to recognize that (1) since quite old times, human wisdom was linked to the plural (distinct global places/cultures) perception of the Universe we are in, with deep respect for earth and nature. Plural ancestral knowledge was added with the scientific methods; however, their joint efforts are the ideal scenario; (2) human behavior is not different than animal behavior, in essence the product of Darwinian natural selection; knowledge of animal and human behavior are complementary; (3) the expression of human behavior follows the same rules that complex systems with emergent properties, therefore, we can measure events in human, clinical, neurobiological situations with complexity systems' tools; (4) we can use the semiology of epilepsies and comorbidities, their neural substrates, and potential treatments (including experimental/computational modeling, neurosurgical interventions), as a source and collection of integrated big data to predict with them (e.g.: machine/deep learning) diagnosis/prognosis, individualized solutions (precision medicine), basic underlying mechanisms and molecular targets. Once the group of symptoms/signals (with a myriad of changing definitions and interpretations over time) and their specific sequences are determined, in epileptology research and clinical settings, the use of modern and contemporary techniques such as neuroanatomical maps, surface electroencephalogram and stereoelectroencephalography (SEEG) and imaging (MRI, BOLD, DTI, SPECT/PET), neuropsychological testing, among others, are auxiliary in the determination of the best electroclinical hypothesis, and help design a specific treatment, usually as the first attempt, with available pharmacological resources. On top of ancient knowledge, currently known and potentially new antiepileptic drugs, alternative treatments and mechanisms are usually produced as a consequence of the hard, multidisciplinary, and integrated studies of clinicians, surgeons, and basic scientists, all over the world. The existence of pharmacoresistant patients, calls for search of other solutions, being along the decades the surgeries the most common interventions, such as resective procedures (i.e., selective or standard lobectomy, lesionectomy), callosotomy, hemispherectomy and hemispherotomy, added by vagus nerve stimulation (VNS), deep brain stimulation (DBS), neuromodulation, and more recently focal minimal or noninvasive ablation. What is critical when we consider the pharmacoresistance aspect with the potential solution through surgery, is still the pursuit of localization-dependent regions (e.g.: epileptogenic zone (EZ)), in order to decide, no matter how sophisticated are the brain mapping tools (EEG and MRI), the size and location of the tissue to be removed. Mimicking the semiology and studying potential neural mechanisms and molecular targets - by means of experimental and computational modeling - are fundamental steps of the whole process. Concluding, with the conjunction of ancient knowledge, coupled to critical and creative contemporary, scientific (not dogmatic) clinical/surgical, and experimental/computational contributions, a better world and of improved quality of life can be offered to the people with epilepsy and neuropsychiatric comorbidities, who are still waiting (as well as the scientists) for a paradigm shift in epileptology, both in the Basic Science, Computational, Clinical, and Neurosurgical Arenas. This article is part of the Special Issue "NEWroscience 2018".

Epilepsy in patients with focal cortical dysplasia may be associated with autism spectrum disorder

INTRODUCTION

Patients with epilepsy associated with focal cortical dysplasia (FCD) may be associated with autism spectrum disorder (ASD). Therefore, the purpose of this study was to compare surgically treated patients with epilepsy secondary to FCD and normal volunteers without epilepsy and to review the neuropathological findings of patients with FCD.

METHODS

This study involved 38 patients with medically intractable focal onset epileptic seizures who underwent epilepsy surgery (Group 1). All patients had epilepsy associated with FCD. These patients and 38 normal volunteers without epilepsy (Group 2) were administered the autism spectrum quotient (AQ) test, and the groups were compared.

RESULTS

The 38 patients in Group 1 included 16 females and 22 males (age range 20-60, mean age, 33.0; standard deviation (SD), 11.8 years). The normal volunteers in Group 2 included 22 females and 16 males (age range 20-57, mean age, 30.6 years; SD, 8.8 years). Total AQ scores were significantly higher in Group 1 than Group 2 (p = 0.027). Patients with FCD I showed a higher AQ score than those with FCD II in the AQ test (p ≤ 0.001).

CONCLUSION

Patients with epilepsy secondary to FCD were associated with higher ASD score than normal volunteers. This tendency was seen more strongly in patients with FCD I than FCD II.

The Role of Magnetoencephalography and Single-Photon Emission Computed Tomography in Evaluation of Children With Drug-Resistant Epilepsy

Surgery holds the best outcomes for drug-resistant epilepsy in children, making localization of a seizure focus essential. However, there is limited research on the contribution of magnetoencephalography and single-photon emission computed tomography (SPECT) to the presurgical evaluation of lesional and nonlesional pediatric patients. This study proposed to evaluate the concordance of SPECT and magnetoencephalography (MEG) to scalp electroencephalography (EEG) to determine their effective contribution to the presurgical evaluation. On review, MEG and SPECT studies for 28 drug-resistant epilepsy cases were completed at Children's Hospital of Pittsburgh from May 2012 to August 2018. Although not reaching statistical significance, MEG had increased lobar concordance with EEG compared with SPECT (68% vs 46%). MEG or SPECT results effectively provided localization data leading to 6 surgical evaluations and 3 resections with outcomes of Engel class I or II at 12 months. This study suggests MEG and SPECT provide valuable localizing information for presurgical epilepsy evaluation of children with drug-resistant epilepsy.

Distinct changes of brain cortical thickness relate to post-treatment outcomes in children with epilepsy

PURPOSE

In the current study, we examined the potential of neuroanatomic measures to cluster patients into different subgroups and established their clinical relevance to post-treatment outcomes.

METHODS

We included seventy-two children with epilepsy (aged 14-195 months) who were treated with anti-seizure medication alone and 39 healthy participants (aged 36-60 months). High-resolution T1-weighted imaging was performed for all participants, and brain cortical thickness measurements were obtained for 68 cortical regions for each of them. Amongst the patients, data-driven hierarchical cluster analysis was performed using the selected cortical thickness measures as features. The average thickness measures in each of the 68 brain regions were then compared between patient subgroups and healthy controls.

RESULTS

Two distinct patient subgroups were identified but were not related to the clinical types. Patients within subgroup 1 (n = 56) had a significantly higher rate of recurrent seizure than those in subgroup 2 (n = 16) (41.1% vs. 14.3%, p<0.05), while the follow-up time or medication did not differ between them. This finding was further confirmed by a recent follow-up through phone calls. The demographic variables, rate of electroencephalogram abnormalities, or sleep problems did not significantly differ between patient subgroups. Compared with healthy controls, patients in subgroup 1 showed significantly increased cortical thickness in the neocortex, whereas patients in subgroup 2 only showed regional cortical thinning in the right superior temporal gyrus.

CONCLUSION

These findings suggest the potential existence of distinct subgroups of children with epilepsy that were especially relevant to the differential patterns of post-treatment outcomes, with regional cortical thinning in the temporal regions relative to controls predicting lower risk of recurrent seizure.

Neuroimaging and genetic characteristics of malformation of cortical development due to mTOR pathway dysregulation: clues for the epileptogenic lesions and indications for epilepsy surgery

Introduction: Malformation of cortical development (MCD) is strongly associated with drug-resistant epilepsies for which surgery to remove epileptogenic lesions is common. Two notable technological advances in this field are identification of the underlying genetic cause and techniques in neuroimaging. These now question how presurgical evaluation ought to be approached for 'mTORpathies.'Area covered: From review of published primary and secondary articles, the authors summarize evidence to consider focal cortical dysplasia (FCD), tuber sclerosis complex (TSC), and hemimegalencephaly (HME) collectively as MCD mTORpathies. The authors also consider the unique features of these related conditions with particular focus on the practicalities of using neuroimaging techniques currently available to define surgical targets and predict post-surgical outcome. Ultimately, the authors consider the surgical dilemmas faced for each condition.Expert opinion: Considering FCD, TSC, and HME collectively as mTORpathies has some merit; however, a unified approach to presurgical evaluation would seem unachievable. Nevertheless, the authors believe combining genetic-centered classification and morphologic findings using advanced imaging techniques will eventually form the basis of a paradigm when considering candidacy for early surgery.

Automated fusion of multimodal imaging data for identifying epileptogenic lesions in patients with inconclusive magnetic resonance imaging

Many methods applied to data acquired by various imaging modalities have been evaluated for their benefit in localizing lesions in magnetic resonance (MR) negative epilepsy patients. No approach has proven to be a stand-alone method with sufficiently high sensitivity and specificity. The presented study addresses the potential benefit of the automated fusion of results of individual methods in presurgical evaluation. We collected electrophysiological, MR, and nuclear imaging data from 137 patients with pharmacoresistant MR-negative/inconclusive focal epilepsy. A subgroup of 32 patients underwent surgical treatment with known postsurgical outcomes and histopathology. We employed a Gaussian mixture model to reveal several classes of gray matter tissue. Classes specific to epileptogenic tissue were identified and validated using the surgery subgroup divided into two disjoint sets. We evaluated the classification accuracy of the proposed method at a voxel-wise level and assessed the effect of individual methods. The training of the classifier resulted in six classes of gray matter tissue. We found a subset of two classes specific to tissue located in resected areas. The average classification accuracy (i.e., the probability of correct classification) was significantly higher than the level of chance in the training group (0.73) and even better in the validation surgery subgroup (0.82). Nuclear imaging, diffusion-weighted imaging, and source localization of interictal epileptic discharges were the strongest methods for classification accuracy. We showed that the automatic fusion of results can identify brain areas that show epileptogenic gray matter tissue features. The method might enhance the presurgical evaluations of MR-negative epilepsy patients.

Experimental Therapeutic Strategies in Epilepsies Using Anti-Seizure Medications

Epilepsies are among the most common neurological problems. The disease burden in patients with epilepsy is significantly high, and epilepsy has a huge negative impact on patients' quality of life with epilepsy and their families. Anti-seizure medications are the mainstay treatment in patients with epilepsy, and around 70% of patients will ultimately control with a combination of at least two appropriately selected anti-seizure medications. However, in one-third of patients, seizures are resistant to drugs, and other measures will be needed. The primary goal in using experimental therapeutic medication strategies in patients with epilepsy is to prevent recurrent seizures and reduce the rate of traumatic events that may occur during seizures. So far, various treatments using medications have been offered for patients with epilepsies, which have been classified according to the type of epilepsy, the effectiveness of the medications, and the adverse effects. Medications such as Levetiracetam, valproic acid, and lamotrigine are at the forefront of these patients' treatment. Epilepsy surgery, neuro-stimulation, and the ketogenic diet are the main measures in patients with medication-resistant epilepsies. In this paper, we will review the therapeutic approach using anti-seizure medications in patients with epilepsy. However, it should be noted that some of these patients still do not respond to existing treatments; therefore, the limited ability of current therapies has fueled research efforts for the development of novel treatment strategies. Thus, it seems that in addition to surgical measures, we should look for more specific agents that have less adverse events and have a greater effect in stopping seizures.

Injection of prophylactic lorazepam versus antiseizure drugs on the localization value of ictal SPECT studies and treatment-emergent adverse events: A single-center prospective study

OBJECTIVE

We aimed to examine the impact of resumption of home antiseizure drugs alone (ASD-) compared with adjunct administration of scheduled intravenous (IV) lorazepam 2 mg every 6 h (ASD+) following ictal single-photon emission computed tomography (SPECT) injection on the localization value of SPECT studies and treatment-emergent adverse events (TEAEs).

METHODS

We conducted a prospective study at Mayo Clinic inpatient epilepsy monitoring unit (EMU) between January 2018 and May 2020 in Jacksonville, Florida. The ASD- and ASD+ groups were compared for concordance of SPECT studies with the epilepsy surgical conference (ESC) consensus or intracranial electroencephalography (icEEG) findings as reference. Treatment-emergent adverse events, obtained from surveys at 24 h and one week postictal SPECT injection, were also compared between both groups.

RESULTS

Twenty-two consecutive patients with temporal (eight patients, 36%) and extratemporal (14 patients, 64%) epilepsy were included: 12 ASD+ and 10 ASD-. The two groups were well matched with regard to clinical and ictal SPECT injection characteristics including the occurrence of seizure between ictal and interictal SPECT injections. The localization value of SPECT studies was similar in the two groups. Patients in the ASD+ group reported higher rates of dizziness and excessive sedation at 24 h (p-value = 0.008). Fourteen patients (64%) underwent icEEG monitoring. For the entire cohort, the localization concordance of SPECT analysis by statistical parametric mapping (SPM) was superior to raw ictal SPECT (p-value = 0.003) and subtraction ictal SPECT coregistered to magnetic resonance imaging (MRI) (SISCOM; p-value = 0.021). Eventually, seven patients (31.8%) underwent resective brain surgery of whom four (57.1%) became seizure-free (median follow-up = 22 months).

CONCLUSIONS

Our findings suggest that resuming home ASDs without the addition of scheduled IV lorazepam following inpatient ictal SPECT injection is equally efficacious for seizure onset zone (SOZ) localization on SPECT studies, especially SPM. This approach is also associated with fewer transient TEAEs and lower financial cost with no difference in preventing seizure between ictal and interictal SPECT injections.

Thai National Guideline for Nuclear Medicine Investigations in Epilepsy

Epilepsy is a disorder of the brain, which is characterized by recurrent epileptic seizures. These patients are generally treated with antiepileptic drugs. However, more than 30% of the patients become medically intractable and undergo a series of investigations to define candidates for epilepsy surgery. Nuclear Medicine studies using Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) radiopharmaceuticals are among the investigations used for this purpose. Since available guidelines for the investigation of surgical candidates are not up-to-date, The Nuclear Medicine Society of Thailand, The Neurological Society of Thailand, The Royal College of Neurological Surgeons of Thailand, and The Thai Medical Physicist Society has collaborated to develop this Thai national guideline for Nuclear Medicine study in epilepsy. The guideline focuses on the use of brain perfusion SPECT and F-18 fluorodeoxyglucose PET (FDG-PET), the mainly used methods in day-to-day practice. This guideline aims for effective use of Nuclear Medicine investigations by referring physicians e.g. epileptologists and neurologists, radiologists, nuclear medicine physicians, medical physicists, nuclear medicine technologists and technicians.

PET and SPECT Imaging of the Brain: History, Technical Considerations, Applications, and Radiotracers

Advances in nuclear medicine have revolutionized our ability to accurately diagnose patients with a wide array of neurologic pathologies and provide appropriate therapy. The development of new radiopharmaceuticals has made possible the identification of regional differences in brain tissue composition and metabolism. In addition, the evolution of 3-dimensional molecular imaging followed by fusion with computed tomography and magnetic resonance imaging have allowed for more precise localization of pathologies. This review will introduce single photon emission computed tomography and positron emission tomographic imaging of the brain, including the history of their development, technical considerations, and a brief overview of pertinent radiopharmaceuticals and their applications.

Molecular Imaging of Brain Tumor-Associated Epilepsy

Epilepsy is a common clinical manifestation and a source of significant morbidity in patients with brain tumors. Neuroimaging has a pivotal role in neuro-oncology practice, including tumor detection, differentiation, grading, treatment guidance, and posttreatment monitoring. In this review, we highlight studies demonstrating that imaging can also provide information about brain tumor-associated epileptogenicity and assist delineation of the peritumoral epileptic cortex to optimize postsurgical seizure outcome. Most studies focused on gliomas and glioneuronal tumors where positron emission tomography (PET) and advanced magnetic resonance imaging (MRI) techniques can detect metabolic and biochemical changes associated with altered amino acid transport and metabolism, neuroinflammation, and neurotransmitter abnormalities in and around epileptogenic tumors. PET imaging of amino acid uptake and metabolism as well as activated microglia can detect interictal or peri-ictal cortical increased uptake (as compared to non-epileptic cortex) associated with tumor-associated epilepsy. Metabolic tumor volumes may predict seizure outcome based on objective treatment response during glioma chemotherapy. Advanced MRI, especially glutamate imaging, can detect neurotransmitter changes around epileptogenic brain tumors. Recently, developed PET radiotracers targeting specific glutamate receptor types may also identify therapeutic targets for pharmacologic seizure control. Further studies with advanced multimodal imaging approaches may facilitate development of precision treatment strategies to control brain tumor-associated epilepsy.

The Preoperative Evaluation of Drug-Resistant Epilepsy

Antiepileptic drugs afford good seizure control for approximately 70% of individuals with epilepsy. Epilepsy surgery is extremely helpful for appropriate individuals with drug resistance. Since antiquity, trephination was a crude and invasive technique to manage epilepsy. The late 1800s saw the advent of a more evidence-based approach with attempts to define seizure foci and determine areas of function. Seizure localization initially required direct brain stimulation during surgery before resection. Fortunately, improved knowledge of seizure semiology and advancements in preoperative investigations have enabled epilepsy specialists to better analyze the benefit of seizure reduction versus risk of functional harm. This preoperative phase and the investigative techniques used to analyze surgical candidacy will be discussed in this article.

Contribution of PET-MRI in brain diseases in clinical practice

PURPOSE OF REVIEW

Hybrid PET- MRI is a technique that has the ability to improve diagnostic accuracy in many applications, whereas PET and MRI performed separately often fail to provide accurate responses to clinical questions. Here, we review recent studies and current developments in PET-MRI, focusing on clinical applications.

RECENT FINDINGS

The combination of PET and MRI imaging methods aims at increasing the potential of each individual modality. Combined methods of image reconstruction and correction of PET-MRI attenuation are being developed, and a number of applications are being introduced into clinical practice. To date, the value of PET-MRI has been demonstrated for the evaluation of brain tumours in epilepsy and neurodegenerative diseases. Continued advances in data analysis regularly improve the efficiency and the potential application of multimodal biomarkers.

SUMMARY

PET-MRI provides simultaneous of anatomical, functional, biochemical and metabolic information for the personalized characterization and monitoring of neurological diseases. In this review, we show the advantage of the complementarity of different biomarkers obtained using PET-MRI data. We also present the recent advances made in this hybrid imaging modality and its advantages in clinical practice compared with MRI and PET separately.

Epilepsy surgery in children: what the radiologist needs to know

This review updates the radiologist on current epilepsy surgery practice in children, with a specific focus on the role of imaging in pre-surgical work-up, current and novel surgical techniques, expected post-surgical imaging appearances and important post-operative complications. A comprehensive review of the current and emerging international practices in paediatric epilepsy surgical planning and post-operative imaging is provided with details on case-based radiological findings. A detailed discussion of the pathophysiology and imaging features of different epileptogenic lesions will not be discussed as this is not the objective of this paper. Epilepsy surgery can be an effective method to control seizures in certain children with drug-resistant focal epilepsy. Early surgery in selected appropriate cases can lead to improved cognitive and developmental outcome. Advances in neurosurgical techniques, imaging and neuroanaesthesia have driven a parallel expansion in the array of epilepsy conditions which are potentially treatable with surgery. The range of surgical options is now wide, including minimally invasive ablative procedures for small lesions such as hypothalamic hamartomata, resections for focal lesions like hippocampal sclerosis and complex disconnective surgeries for multilobar conditions like Sturge Weber Syndrome and diffuse cortical malformations. An awareness of the surgical thinking when planning epilepsy surgery in children, and the practical knowledge of the operative steps involved will promote more accurate radiology reporting of the post-operative scan.