•MEG connectivity and network-based analyses are powerful for characterizing childhood absence epilepsy (CAE).•Highly-connected regions (“hubs”) represent critical regions for childhood absence ...epilepsy.•Group network parcellation reveals ictal hubs within focal cortical, subcortical, and cerebellar regions.
Absence seizures are thought to be linked to abnormal interplays between regions of a thalamocortical network. However, the complexity of this widespread network makes characterizing the functional interactions among various brain regions challenging. Using whole-brain functional connectivity and network analysis of magnetoencephalography (MEG) data, we explored pre-treatment brain hubs (“highly connected nodes”) of patients aged 6 to 12 years with childhood absence epilepsy. We analyzed ictal MEG data of 74 seizures from 16 patients. We employed a time-domain beamformer technique to estimate MEG sources in broadband (1–40 Hz) where the greatest power changes between ictal and preictal periods were identified. A phase synchrony measure, phase locking value, and a graph theory metric, eigenvector centrality (EVC), were utilized to quantify voxel-level connectivity and network hubs of ictal > preictal periods, respectively. A volumetric atlas containing 116 regions of interests (ROIs) was utilized to summarize the network measures. ROIs with EVC (z-score) > 1.96 were reported as critical hubs. ROIs analysis revealed functional-anatomical hubs in a widespread network containing bilateral precuneus (right/left, z = 2.39, 2.18), left thalamus (z = 2.28), and three anterior cerebellar subunits of lobule “IV-V” (z = 3.9), vermis “IV-V” (z = 3.57), and lobule “III” (z = 2.03). Findings suggest that highly connected brain areas or hubs are present in focal cortical, subcortical, and cerebellar regions during absence seizures. Hubs in thalami, precuneus and cingulate cortex generally support a theory of rapidly engaging and bilaterally distributed networks of cortical and subcortical regions responsible for seizures generation, whereas hubs in anterior cerebellar regions may be linked to terminating motor automatisms frequently seen during typical absence seizures. Whole-brain network connectivity is a powerful analytic tool to reveal focal components of absence seizures in MEG. Our investigations can lead to a better understanding of the pathophysiology of CAE.
Abstract We review the evidence that BECTS may be associated with cognitive dysfunction and behavioral problems, the extent to which these problems may be associated with patterns of EEG ...abnormalities in BECTS, and the impact of antiepileptic medication on cognition and behavior in BECTS. A growing literature examining cognitive and behavioral outcomes suggests that children with BECTS perform below the level of their peers. Consistent with this, neuroimaging studies reveal that BECTS has an impact on structural and functional brain development, but the potential influence of frequency and lateralization of centrotemporal spikes (CTS) on cognition and behavior is not well understood. Treatment with AEDs is an option in BECTS, but existing studies have not clearly shown a clear relationship between elimination of CTS and improved cognitive or behavioral outcomes.
Source localization for clinical magnetoencephalography recordings is challenging, and many methods have been developed to solve this inverse problem. The most well-studied and validated tool for ...localization of the epileptogenic zone is the equivalent current dipole. However, it is often difficult to summarize the richness of the magnetoencephalography data with one or a few point sources. A variety of source localization algorithms have been developed to more fully explain the complexity of clinical magnetoencephalography data used to define the epileptogenic network. In this review, various clinically available source localization methods are described and their individual strengths and limitations are discussed.
According to the latest operational 2017 ILAE classification of epileptic seizures, the generalized epileptic seizure is still conceptualized as "originating at some point within and rapidly ...engaging, bilaterally distributed networks." In contrast, the focal epileptic seizure is defined as "
." Hence, one of the main concepts of "generalized" and "focal" epilepsy comes from EEG descriptions before the era of source localization, and a presumed simultaneous bilateral onset and bi-synchrony of epileptiform discharges remains a hallmark for generalized seizures. Current literature on the pathophysiology of generalized epilepsy supports the concept of a cortical epileptogenic focus triggering rapidly generalized epileptic discharges involving intact corticothalamic and corticocortical networks, known as the
. Likewise, focal epilepsy with rich connectivity can give rise to generalized spike and wave discharges resulting from widespread bilateral synchronization. Therefore, making this key distinction between generalized and focal epilepsy may be challenging in some cases, and for the first time, a combined generalized and focal epilepsy is categorized in the 2017 ILAE classification. Nevertheless, treatment options, such as the choice of antiseizure medications or surgical treatment, are the reason behind the importance of accurate epilepsy classification. Over the past several decades, plentiful scientific research on the pathophysiology of generalized epilepsy has been conducted using non-invasive neuroimaging and postprocessing of the electromagnetic neural signal by measuring the spatiotemporal and interhemispheric latency of bi-synchronous or generalized epileptiform discharges as well as network analysis to identify diagnostic and prognostic biomarkers for accurate diagnosis of the two major types of epilepsy. Among all the advanced techniques, magnetoencephalography (MEG) and multiple other methods provide excellent temporal and spatial resolution, inherently suited to analyzing and visualizing the propagation of generalized EEG activities. This article aims to provide a comprehensive literature review of recent innovations in MEG methodology using source localization and network analysis techniques that contributed to the literature of idiopathic generalized epilepsy in terms of pathophysiology and clinical prognosis, thus further blurring the boundary between focal and generalized epilepsy.
Summary
Objective
The understanding of childhood absence epilepsy (CAE) has been revolutionized over the past decade, but the biological mechanisms responsible for variable treatment outcomes are ...unknown. Our purpose in this prospective observational study was to determine how pretreatment ictal network pathways, defined using a combined electroencephalography (EEG)–functional magnetic resonance imaging (EEG‐fMRI) and magnetoencephalography (MEG) effective connectivity analysis, were related to treatment response.
Methods
Sixteen children with newly diagnosed and drug‐naive CAE had 31 typical absence seizures during EEG‐fMRI and 74 during MEG. The spatial extent of the pretreatment ictal network was defined using fMRI hemodynamic response with an event‐related independent component analysis (eICA). This spatially defined pretreatment ictal network supplied prior information for MEG‐effective connectivity analysis calculated using phase slope index (PSI). Treatment outcome was assessed 2 years following diagnosis and dichotomized to ethosuximide (ETX)–treatment responders (N = 11) or nonresponders (N = 5). Effective connectivity of the pretreatment ictal network was compared to the treatment response.
Results
Patterns of pretreatment connectivity demonstrated strongest connections in the thalamus and posterior brain regions (parietal, posterior cingulate, angular gyrus, precuneus, and occipital) at delta frequencies and the frontal cortices at gamma frequencies (P < .05). ETX treatment nonresponders had pretreatment connectivity, which was decreased in the precuneus region and increased in the frontal cortex compared to ETX responders (P < .05).
Significance
Pretreatment ictal connectivity differences in children with CAE were associated with response to antiepileptic treatment. This is a possible mechanism for the variable treatment response seen in patients sharing the same epilepsy syndrome.
Objective
The aim of this study was to determine the frequency‐dependent, spatiotemporal involvement of corticothalamic networks to the generation of absence seizures.
Methods
Magnetoencephalography ...recordings were obtained in 12 subjects (44 seizures) with untreated childhood absence seizures. Time‐frequency analysis of each seizure was performed to determine bandwidths with significant power at ictal onset. Source localization was then completed to determine brain regions contributing to generalized spike and wave discharges seen on electroencephalogram.
Results
Significant power in the time‐frequency analysis was seen within 1 to 20Hz, 20 to 70Hz, and 70 to 150Hz bandwidths. Source localization revealed that sources localized to the frontal cortex similarly for the low‐ and gamma‐frequency bandwidths, whereas at the low‐frequency bandwidth (3–20Hz) significantly more sources localized to the parietal cortex (odds ratio OR = 16.7). Cortical sources within the high‐frequency oscillation (HFO) bandwidth (70–150Hz) localized primarily to the frontal region compared to the parietal (OR = 7.32) or temporal (OR = 2.78) areas.
Interpretation
Neuromagnetic activity within frontal and parietal cortical regions provides further confirmation of hemodynamic changes reported using functional magnetic resonance imaging that have been associated with absence seizures. The frequency‐dependent nature of these networks has not previously been reported, and the presence of HFOs during absence seizures is a novel finding. Co‐occurring frontal and parietal corticothalamic networks may interact to produce a pathological state that contributes to the generation of spike and wave discharges. The clinical and pathophysiological implications of HFOs within the frontal cortical region are unclear and should be further investigated. Ann Neurol 2014;76:558–567
Few effective second-line treatments exist for women with recurrent or metastatic cervical cancer. Accordingly, we aimed to evaluate the efficacy and safety of tisotumab vedotin, a tissue ...factor-directed antibody–drug conjugate, in this patient population.
This multicentre, open-label, single-arm, phase 2 study was done across 35 academic centres, hospitals, and community practices in Europe and the USA. The study included patients aged 18 years or older who had recurrent or metastatic squamous cell, adenocarcinoma, or adenosquamous cervical cancer; disease progression on or after doublet chemotherapy with bevacizumab (if eligible by local standards); who had received two or fewer previous systemic regimens for recurrent or metastatic disease; had measurable disease based on Response Evaluation Criteria in Solid Tumors (RECIST; version 1.1); and had an Eastern Cooperative Oncology Group performance status of 0 or 1. Patients received 2·0 mg/kg (up to a maximum of 200 mg) tisotumab vedotin intravenously once every 3 weeks until disease progression (determined by the independent review committee) or unacceptable toxicity. The primary endpoint was confirmed objective response rate based on RECIST (version 1.1), as assessed by the independent review committee. Activity and safety analyses were done in patients who received at least one dose of the drug. This study is ongoing with recruitment completed and is registered with ClinicalTrials.gov, NCT03438396.
102 patients were enrolled between June 12, 2018, and April 11, 2019; 101 patients received at least one dose of tisotumab vedotin. Median follow-up at the time of analysis was 10·0 months (IQR 6·1–13·0). The confirmed objective response rate was 24% (95% CI 16–33), with seven (7%) complete responses and 17 (17%) partial responses. The most common treatment-related adverse events included alopecia (38 38% of 101 patients), epistaxis (30 30%), nausea (27 27%), conjunctivitis (26 26%), fatigue (26 26%), and dry eye (23 23%). Grade 3 or worse treatment-related adverse events were reported in 28 (28%) patients and included neutropenia (three 3% patients), fatigue (two 2%), ulcerative keratitis (two 2%), and peripheral neuropathies (two 2% each with sensory, motor, sensorimotor, and neuropathy peripheral). Serious treatment-related adverse events occurred in 13 (13%) patients, the most common of which included peripheral sensorimotor neuropathy (two 2% patients) and pyrexia (two 2%). One death due to septic shock was considered by the investigator to be related to therapy. Three deaths unrelated to treatment were reported, including one case of ileus and two unknown causes.
Tisotumab vedotin showed clinically meaningful and durable antitumour activity with a manageable and tolerable safety profile in women with previously treated recurrent or metastatic cervical cancer. Given the poor prognosis for this patient population and the low activity of current therapies in this setting, tisotumab vedotin, if approved, would represent a new treatment for women with recurrent or metastatic cervical cancer.
Genmab, Seagen, Gynaecologic Oncology Group, and European Network of Gynaecological Oncological Trial Groups.
Objective
Electrical stimulation mapping (ESM) is the clinical standard for functional localization with subdural electrodes (SDE). As stereoelectroencephalography (SEEG) has emerged as an ...alternative option, we compared functional responses, afterdischarges (ADs), and unwanted ESM‐induced seizures (EISs) between the two electrode types.
Methods
Incidence and current thresholds for functional responses (sensory, motor, speech/language), ADs, and EISs were compared between SDE and SEEG using mixed models incorporating relevant covariates.
Results
We identified 67 SEEG ESM and 106 SDE ESM patients (7207 and 4980 stimulated contacts, respectively). We found similar incidence of language and motor responses between electrode types; however, more SEEG patients reported sensory responses. ADs and EISs occurred less commonly with SEEG than SDE. Current thresholds for language, face motor, and upper extremity (UE) motor responses and EIS significantly decreased with age. However, they were not affected by electrode type, premedication, or dominant hemispheric stimulation. AD thresholds were higher with SEEG than with SDE. For SEEG ESM, language thresholds remained below AD thresholds up to 26 years of age, whereas this relationship was inverse for SDE. Also, face and UE motor thresholds fell below AD thresholds at earlier ages for SEEG than SDE. AD and EIS thresholds were not affected by premedication.
Significance
SEEG and SDE have clinically relevant differences for functional brain mapping with electrical stimulation. Although evaluation of language and motor regions is comparable between SEEG and SDE, SEEG offers a higher likelihood of identifying sensory areas. A lower incidence of ADs and EISs, and a favorable relationship between functional and AD thresholds suggest superior safety and neurophysiologic validity for SEEG ESM than SDE ESM.
A left perisylvian network is known to support language in healthy adults. Low-beta (13-23 Hz) event-related desynchrony (ERD) has been observed during verb generation, at approximately 700-1200 ms ...post-stimulus presentation in past studies; the signal is known to reflect increased neuronal firing and metabolic demand during language production. In contrast, concurrent beta event-related synchrony (ERS) is thought to reflect neuronal inhibition but has not been well studied in the context of language. Further, while low-beta ERD for expressive language has been found to gradually shift from bilateral in childhood to left hemispheric by early adulthood, developmental lateralization of ERS has not been established. We used magnetoencephalography to study low beta ERS lateralization in a group of children and adolescents (n = 78), aged 4 to less than 19 years, who performed covert verb generation. We found that the youngest children had bilateral ERD and ERS. By adolescence, low-beta ERD was predominantly left lateralized in perisylvian cortex (i.e., Broca's and Wernicke's regions), while beta ERS was predominantly right lateralized. Increasing lateralization was significantly correlated to age for both ERD (Spearman's r = 0.45, p < 0.01) and ERS (Spearman's r = - 0.44, p < 0.01). Interestingly, while ERD lateralized in a linear manner, ERS lateralization followed a nonlinear trajectory, suggesting distinct developmental trajectories. Implications to early-age neuroplasticity and neuronal inhibition are discussed.
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