Origin and propagation of epileptic spasms delineated on electrocorticography

Identification and treatment of surgically-remediable causes of infantile epileptic spasms syndrome

INTRODUCTION

Infantile epileptic spasms syndrome (IESS) is a common developmental and epileptic encephalopathy with poor long-term outcomes. A substantial proportion of patients with IESS have a potentially surgically remediable etiology. Despite this, epilepsy surgery is underutilized in this patient group. Some surgically remediable etiologies, such as focal cortical dysplasia and malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE), are under-diagnosed in infants and young children. Even when a surgically remediable etiology is recognised, for example, tuberous sclerosis or focal encephalomalacia, epilepsy surgery may be delayed or not considered due to diffuse EEG changes, unclear surgical boundaries, or concerns about operating in this age group.

AREAS COVERED

In this review, the authors discuss the common surgically remediable etiologies of IESS, their clinical and EEG features, and the imaging techniques that can aid in their diagnosis. They then describe the surgical approaches used in this patient group, and the beneficial impact that early epilepsy surgery can have on developing brain networks.

EXPERT OPINION

Epilepsy surgery remains underutilized even when a potentially surgically remediable cause is recognized. Overcoming the barriers that result in under-recognition of surgical candidates and underutilization of epilepsy surgery in IESS will improve long-term seizure and developmental outcomes.

Electroclinical Features of Infantile Epileptic Spasms Syndrome

Epileptic spasms are a unique, age-dependent manifestation of epilepsies in infancy and early childhood, commonly occurring as part of infantile epileptic spasms syndrome. Developmental stagnation and subsequent decline may occur in children with epileptic spasms, partly due to the abundant high-amplitude interictal epileptiform and slow wave abnormalities. Early recognition and treatment of epileptic spasms, along with the reversal of the electroencephalography (EEG) findings, are critical for improving outcomes. Recognizing hypsarrhythmia and its variations is key to confirming the diagnosis. The various patterns of hypsarrhythmia are not etiology specific, but could indicate the severity of the disease. Several scoring systems have been proposed to improve the inter-rater reliability of recognizing hypsarrhythmia and to assess EEG progress in response to treatment. Ictal patterns during spasms are brief and composed of slow waves, sharp transients, fast activity, and voltage attenuation, either in isolation or more commonly as a combination of these waveforms. Ictal patterns are commonly diffuse, but may be lateralized to one hemisphere in children with structural etiology. A subset of patients with epileptic spasms has a surgically remediable etiology, with readily identifiable lesions on neuroimaging in most cases. Asymmetry in epileptic spasms, concurrent focal seizures, and asymmetric interictal and ictal EEG findings may be present, but a lack of focality in electrophysiological findings is not uncommon. Intracranial EEG features of epileptic spasms have been described, but the utility of intracranial EEG monitoring in surgical candidates with overt focal epileptogenic lesions on magnetic resonance imaging is questionable, and surgery could be performed using noninvasive data.

Mechanisms of infantile epileptic spasms syndrome: What have we learned from animal models?

The devastating developmental and epileptic encephalopathy of infantile epileptic spasms syndrome (IESS) has numerous causes, including, but not limited to, brain injury, metabolic, and genetic conditions. Given the stereotyped electrophysiologic, age-dependent, and clinical findings, there likely exists one or more final common pathways in the development of IESS. The identity of this final common pathway is unknown, but it may represent a novel therapeutic target for infantile spasms. Previous research on IESS has focused largely on identifying the neuroanatomic substrate using specialized neuroimaging techniques and cerebrospinal fluid analysis in human patients. Over the past three decades, several animal models of IESS were created with an aim to interrogate the underlying pathogenesis of IESS, to identify novel therapeutic targets, and to test various treatments. Each of these models have been successful at recapitulating multiple aspects of the human IESS condition. These animal models have implicated several different molecular pathways in the development of infantile spasms. In this review we outline the progress that has been made thus far using these animal models and discuss future directions to help researchers identify novel treatments for drug-resistant IESS.

Electroclinical Features in Epilepsy Surgery Candidates With Epileptic Spasms

SUMMARY

Electroclinical features in surgical candidates with epileptic spasms differ significantly from the other focal epilepsy phenotypes. EEG findings tend to be more diffuse and less localizing in children with epileptic spasms. These are illustrated with five case studies to highlight three different categories of findings on interictal and ictal EEG: lateralizing , nonlateralizing , and false lateralizing . Hemihypsarrhythmia on interictal EEG is the most striking lateralizing abnormality that occurs in a minority of surgical candidates. Persistent focal epileptiform discharges in one region or asymmetric physiologic rhythms decreased over the abnormal hemisphere may provide localization clues. Ictal EEG patterns are diffuse and nonlocalizing in over half of the patients. Ictal patterns are best expressed in the posterior head regions even in patients with epileptogenic zone in anterior regions. Semiologically, epileptic spasms tend to be symmetrical in majority of surgical candidates. Asymmetric spasms and coexisting focal seizures (concurrent or remote), when present, may provide localization findings. False lateralizing interictal or ictal EEG abnormalities, paradoxically higher over the healthier hemisphere, occur in the setting of large encephaloclastic/volume loss lesions. In these patients, the diffuse discharges are less expressed over the abnormal hemisphere with less cerebral tissue. Recognition of such false lateralizing findings is important to avoid excluding appropriate surgical candidates based on the EEG findings alone. Epileptogenic lesions are visible on brain MRI in majority of surgical candidates with epileptic spasms. Electroclinical findings are often concordant with the lesion, but discordant findings are not uncommon in children with epileptic spasms.

Clinical neuroscience and neurotechnology: An amazing symbiosis

In the last decades, clinical neuroscience found a novel ally in neurotechnologies, devices able to record and stimulate electrical activity in the nervous system. These technologies improved the ability to diagnose and treat neural disorders. Neurotechnologies are concurrently enabling a deeper understanding of healthy and pathological dynamics of the nervous system through stimulation and recordings during brain implants. On the other hand, clinical neurosciences are not only driving neuroengineering toward the most relevant clinical issues, but are also shaping the neurotechnologies thanks to clinical advancements. For instance, understanding the etiology of a disease informs the location of a therapeutic stimulation, but also the way stimulation patterns should be designed to be more effective/naturalistic. Here, we describe cases of fruitful integration such as Deep Brain Stimulation and cortical interfaces to highlight how this symbiosis between clinical neuroscience and neurotechnology is closer to a novel integrated framework than to a simple interdisciplinary interaction.

Periodic electroencephalographic discharges and epileptic spasms involve cortico-striatal-thalamic loops on Arterial Spin Labeling Magnetic Resonance Imaging

Periodic discharges are a rare peculiar electroencephalogram pattern, occasionally associated with motor or other clinical manifestations, usually observed in critically ill patients. Their underlying pathophysiology remains poorly understood. Epileptic spasms in clusters and periodic discharges with motor manifestations share similar electroencephalogram pattern and some aetiologies of unfavourable prognosis such as subacute sclerosing panencephalitis or herpes encephalitis. Arterial spin labelling magnetic resonance imaging identifies localizing ictal and inter-ictal changes in neurovascular coupling, therefore assumed able to reveal concerned cerebral structures. Here, we retrospectively analysed ictal and inter-ictal arterial spin labelling magnetic resonance imaging in patients aged 6 months to 15 years (median 3 years 4 months) with periodic discharges including epileptic spasms, and compared these findings with those of patients with drug-resistant focal epilepsy who never presented periodic discharges nor epileptic spasms as well as to those of age-matched healthy controls. Ictal electroencephalogram was recorded either simultaneously with arterial spin labelling magnetic resonance imaging or during the close time lapse of patients' periodic discharges, whereas inter-ictal examinations were performed during the patients' active epilepsy but without seizures during the arterial spin labelling magnetic resonance imaging. Ictal arterial spin labelling magnetic resonance imaging was acquired in five patients with periodic discharges [subacute sclerosing panencephalitis (1), stroke-like events (3), West syndrome with cortical malformation (1), two of them also had inter-ictal arterial spin labelling magnetic resonance imaging]. Inter-ictal group included patients with drug-resistant epileptic spasms of various aetiologies (14) and structural drug-resistant focal epilepsy (8). Cortex, striatum and thalamus were segmented and divided in six functional subregions: prefrontal, motor (rostral, caudal), parietal, occipital and temporal. Rest cerebral blood flow values, absolute and relative to whole brain, were compared with those of age-matched controls for each subregion. Main findings were diffuse striatal as well as cortical motor cerebral blood flow increase during ictal examinations in generalized periodic discharges with motor manifestations (subacute sclerosing panencephalitis) and focal cerebral blood flow increase in corresponding cortical-striatal-thalamic subdivisions in lateralized periodic discharges with or without motor manifestations (stroke-like events and asymmetrical epileptic spasms) with straight topographical correlation with the electroencephalogram focus. For inter-ictal examinations, patients with epileptic spasms disclosed cerebral blood flow changes in corresponding cortical-striatal-thalamic subdivisions (absolute-cerebral blood flow decrease and relative-cerebral blood flow increase), more frequently when compared with the group of drug-resistant focal epilepsies, and not related to Vigabatrin treatment. Our results suggest that corresponding cortical-striatal-thalamic circuits are involved in periodic discharges with and without motor manifestations, including epileptic spasms, opening new insights in their pathophysiology and new therapeutical perspectives. Based on these findings, we propose a model for the generation of periodic discharges and of epileptic spasms combining existing pathophysiological models of cortical-striatal-thalamic network dynamics.

Epileptic spasms are associated with increased stereo-electroencephalography derived functional connectivity in tuberous sclerosis complex

OBJECTIVE

Epileptic spasms (ES) are common in tuberous sclerosis complex (TSC). However, the underlying network alterations and relationship with epileptogenic tubers are poorly understood. We examined interictal functional connectivity (FC) using stereo-electroencephalography (SEEG) in patients with TSC to investigate the relationship between tubers, epileptogenicity, and ES.

METHODS

We analyzed 18 patients with TSC who underwent SEEG (mean age = 11.5 years). The dominant tuber (DT) was defined as the most epileptogenic tuber using the epileptogenicity index. Epileptogenic zone (EZ) organization was quantitatively separated into focal (isolated DT) and complex (all other patterns). Using a 20-min interictal recording, FC was estimated with nonlinear regression, h² . We calculated (1) intrazone FC within all sampled tubers and normal-appearing cortical zones, respectively; and (2) interzone FC involving connections between DT, other tubers, and normal cortex. The relationship between FC and (1) presence of ES as a current seizure type at the time of SEEG, (2) EZ organization, and (3) epileptogenicity was analyzed using a mixed generalized linear model. Spike rate and distance between zones were considered in the model as covariates.

RESULTS

Six patients had ES as a current seizure type at time of SEEG. ES patients had a greater number of tubers with a fluid-attenuated inversion recovery hypointense center (p < .001), and none had TSC1 mutations. The presence of ES was independently associated with increased FC within both intrazone (p = .033) and interzone (p = .011) networks. Post hoc analyses identified that increased FC was associated with ES across tuber and nontuber networks. EZ organization and epileptogenicity biomarkers were not associated with FC.

SIGNIFICANCE

Increased cortical synchrony among both tuber and nontuber networks is characteristic of patients with ES and independent of both EZ organization and tuber epileptogenicity. This further supports the prospect of FC biomarkers aiding treatment paradigms in TSC.

Lesional Intractable Epileptic Spasms in Children: Electroclinical Localization and Postoperative Outcomes

To analyze the influence of seizure semiology, electroencephalography (EEG) features and magnetic resonance imaging (MRI) change on epileptogenic zone localization and surgical prognosis in children with epileptic spasm (ES) were assessed. Data from 127 patients with medically intractable epilepsy with ES who underwent surgical treatment were retrospectively analyzed. ES semiology was classified as non-lateralized, bilateral asymmetric, and focal. Interictal epileptiform discharges were divided into diffusive or multifocal, unilateral, and focal. MRI results showed visible local lesions for all patients, while the anatomo-electrical-clinical value of localization of the epileptogenic zone was dependent on the surgical outcome. During preoperative video EEG monitoring, among all 127 cases, 53 cases (41.7%) had ES only, 46 (36.2%) had ES and focal seizures, 17 (13.4%) had ES and generalized seizures, and 11 (8.7%) had ES with focal and generalized seizures. Notably, 35 (27.6%) and 92 cases (72.4%) showed simple and complex ES, respectively. Interictal EEG showed that 22 cases (17.3%) had bilateral multifocal discharges or hypsarrhythmia, 25 (19.7%) had unilateral dominant discharges, and 80 (63.0%) had definite focal or regional discharges. Ictal discharges were generalized/bilateral in 71 cases (55.9%) and definite/lateralized in 56 cases (44.1%). Surgically resected lesions were in the hemisphere (28.3%), frontal lobe (24.4%), temporal lobe (16.5%), temporo-parieto-occipital region (14.2%), and posterior cortex region (8.7%). Seizure-free rates at 1 and 4 years postoperatively were 81.8 and 72.7%, respectively. There was no significant difference between electroclinical characteristics of ES and seizure-free rate. Surgical treatment showed good outcomes in most patients in this cohort. Semiology and ictal EEG change of ES had no effect on localization, while focal or lateralized epileptiform discharges of interictal EEG may affect lateralization and localization. Complete resection of epileptogenic lesions identified via MRI was the only factor associated with a positive surgical outcome.

In Vivo Neural Interfaces—From Small- to Large-Scale Recording

Brain functions arise from the coordinated activation of neuronal assemblies distributed across multiple brain regions. The electrical potential from the neuron captured by the electrode can be processed to extract brain information. A large number of densely and simultaneously recorded neuronal potential signals from neurons spanning multiple brain regions contribute to the insight of specific behaviors encoded by the neural ensembles. In this review, we focused on the neural interfaces developed for small- to large-scale recordings and discussed the developmental challenges and strategies in microsystem, electrode device, and interface material levels for the future larger-scale neural ensemble recordings.

The role of neurosurgery in the management of tuberous sclerosis complex–associated epilepsy: a systematic review

OBJECTIVE

Tuberous sclerosis complex (TSC) is an autosomal dominant, multisystem neurocutaneous disorder associated with cortical tubers, brain lesions seen in nearly all patients with TSC, which are frequently epileptogenic. Seizures are often the earliest clinical manifestation of TSC, leading to epilepsy in over 70% of patients. Medical management with antiepileptic drugs constitutes early therapy, but over 50% develop medically refractory epilepsy, necessitating surgical evaluation and treatment. The objective of this study was to summarize the literature and report seizure outcomes following surgical treatment for TSC-associated epilepsy.

METHODS

A systematic literature review was performed in accordance with the PRISMA guidelines. The PubMed and Embase databases were searched for journal articles reporting seizure outcomes following epilepsy surgery in TSC patients. Included studies were placed into one of two groups based on the surgical technique used. Excellent and worthwhile seizure reductions were defined for each group as outcomes and extracted from each study.

RESULTS

A total of 46 studies were included. Forty of these studies reported seizure outcomes following any combination of resection, disconnection, and ablation on a collective 1157 patients. Excellent and worthwhile seizure reductions were achieved in 59% (683/1157) and 85% (450/528) of patients, respectively. Six of these studies reported seizure outcomes following treatment with neuromodulation. Excellent and worthwhile seizure reductions were achieved in 34% (24/70) and 76% (53/70) of patients, respectively.

CONCLUSIONS

Surgery effectively controls seizures in select patients with TSC-associated epilepsy, but outcomes vary. Further understanding of TSC-associated epilepsy, improving localization strategies, and emerging surgical techniques represent promising avenues for improving surgical outcomes.

Diffusion tractography predicts propagated high-frequency activity during epileptic spasms

OBJECTIVE

Determine the structural networks that constrain propagation of ictal oscillations during epileptic spasm events, and compare observed propagation patterns across patients with successful or unsuccessful surgical outcomes.

METHODS

Subdural electrode recordings of 18 young patients (age 1-11 years) were analyzed during epileptic spasm events to determine ictal networks and quantify the amplitude and onset time of ictal oscillations across the cortical surface. Corresponding structural networks were generated with diffusion MRI tractography by seeding the cortical region associated with the earliest average oscillation onset time, and white matter pathways connecting active electrode regions within the ictal network were isolated. Properties of this structural network were used to predict oscillation onset times and amplitudes, and this relationship was compared across patients who did and did not achieve seizure freedom following resective surgery.

RESULTS

Onset propagation patterns were relatively consistent across each patients' spasm events. An electrode's average ictal oscillation onset latency was most significantly associated with the length of direct corticocortical tracts connecting to the area with the earliest average oscillation onset (p < .001, model R²  = 0.54). Moreover, patients demonstrating a faster propagation of ictal oscillation signals within the corticocortical network were more likely to have seizure recurrence following resective surgery (p = .039). Ictal oscillation amplitude was also associated with connecting tractography length and weighted fractional anisotropy (FA) measures along these pathways (p = .002/.030, model R²  = 0.31/0.25). Characteristics of analogous corticothalamic pathways did not show significant associations with ictal oscillation onset latency or amplitude.

SIGNIFICANCE

Spatiotemporal propagation patterns of high-frequency activity in epileptic spasms align with length and FA measures from onset-originating corticocortical pathways. Considering data in this individualized framework may help inform surgical decision making and expectations of surgical outcomes.

Advanced Bioelectrical Signal Processing Methods: Past, Present and Future Approach-Part II: Brain Signals

As it was mentioned in the previous part of this work (Part I)-the advanced signal processing methods are one of the quickest and the most dynamically developing scientific areas of biomedical engineering with their increasing usage in current clinical practice. In this paper, which is a Part II work-various innovative methods for the analysis of brain bioelectrical signals were presented and compared. It also describes both classical and advanced approaches for noise contamination removal such as among the others digital adaptive and non-adaptive filtering, signal decomposition methods based on blind source separation, and wavelet transform.

Preoperative evaluation and surgical strategy for epileptic spasms in children

Epileptic spasm (ES) is one of the most common types of seizures in children. It is primarily characterized by brief axial contractions lasting less than 2 s and recurring in short clusters. It usually occurs in children of 3 to 12 months of age, although it can also occur after the age of 1 year. In general, children with ES develop other symptoms of epilepsy, such as tonic, tonic‐clonic, or focal seizures, after 3 to 5 years of age. ES in children is often damaging and usually results in developmental regression. First‐line treatments for spasm seizures include adrenocorticotropic hormone (ACTH) and vigabatrin. However, many patients fail to respond to these medications, and continued to have spasms associated with progressive neurodevelopmental degeneration. Therefore, it is important to consider whether children with drug resistance meet surgical indications to consider surgical treatment in such conditions. In this study, we reviewed and summarized the importance of preoperative evaluation in order to provide surgical options for treatment of children with ES.

Intracranial recording in patients with aphasia using nanomaterial-based flexible electronics: promises and challenges

In recent years, researchers have studied how nanotechnology could enhance neuroimaging techniques. The application of nanomaterial-based flexible electronics has the potential to advance conventional intracranial electroencephalography (iEEG) by utilising brain-compatible soft nanomaterials. The resultant technique has significantly high spatial and temporal resolution, both of which enhance the localisation of brain functions and the mapping of dynamic language processing. This review presents findings on aphasia, an impairment in language and communication, and discusses how different brain imaging techniques, including positron emission tomography, magnetic resonance imaging, and iEEG, have advanced our understanding of the neural networks underlying language and reading processing. We then outline the strengths and weaknesses of iEEG in studying human cognition and the development of intracranial recordings that use brain-compatible flexible electrodes. We close by discussing the potential advantages and challenges of future investigations adopting nanomaterial-based flexible electronics for intracranial recording in patients with aphasia.

Early seizure spread and epilepsy surgery: A systematic review

OBJECTIVE

A fundamental question in epilepsy surgery is how to delineate the margins of cortex that must be resected to result in seizure freedom. Whether and which areas showing seizure activity early in ictus must be removed to avoid postoperative recurrence of seizures is an area of ongoing research. Seizure spread dynamics in the initial seconds of ictus are often correlated with postoperative outcome; there is neither a consensus definition of early spread nor a concise summary of the existing literature linking seizure spread to postsurgical seizure outcomes. The present study is intended to summarize the literature that links seizure spread to postoperative seizure outcome and to provide a framework for quantitative assessment of early seizure spread.

METHODS

A systematic review was carried out according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A Medline search identified clinical studies reporting data on seizure spread measured by intracranial electrodes, having at least 10 subjects and reporting at least 1-year postoperative outcome in the English literature from 1990 to 2019. Studies were evaluated regarding support for a primary hypothesis: Areas of early seizure spread represent cortex with seizure-generating potential.

RESULTS

The search yielded 4562 studies: 15 studies met inclusion criteria and 7 studies supported the primary hypothesis. The methods and metrics used to describe seizure spread were heterogenous. The timeframe of seizure spread associated with seizure outcome ranged from 1-14 seconds, with large, well-designed, retrospective studies pointing to 3-10 seconds as most likely to provide meaningful correlates of postoperative seizure freedom.

SIGNIFICANCE

The complex correlation between electrophysiologic seizure spread and the potential for seizure generation needs further elucidation. Prospective cohort studies or trials are needed to evaluate epilepsy surgery targeting cortex involved in the first 3-10 seconds of ictus.

Sensor Modalities for Brain-Computer Interface Technology: A Comprehensive Literature Review

Brain-computer interface (BCI) technology is rapidly developing and changing the paradigm of neurorestoration by linking cortical activity with control of an external effector to provide patients with tangible improvements in their ability to interact with the environment. The sensor component of a BCI circuit dictates the resolution of brain pattern recognition and therefore plays an integral role in the technology. Several sensor modalities are currently in use for BCI applications and are broadly either electrode-based or functional neuroimaging-based. Sensors vary in their inherent spatial and temporal resolutions, as well as in practical aspects such as invasiveness, portability, and maintenance. Hybrid BCI systems with multimodal sensory inputs represent a promising development in the field allowing for complimentary function. Artificial intelligence and deep learning algorithms have been applied to BCI systems to achieve faster and more accurate classifications of sensory input and improve user performance in various tasks. Neurofeedback is an important advancement in the field that has been implemented in several types of BCI systems by showing users a real-time display of their recorded brain activity during a task to facilitate their control over their own cortical activity. In this way, neurofeedback has improved BCI classification and enhanced user control over BCI output. Taken together, BCI systems have progressed significantly in recent years in terms of accuracy, speed, and communication. Understanding the sensory components of a BCI is essential for neurosurgeons and clinicians as they help advance this technology in the clinical setting.

Cortical high-frequency oscillation loops initiate spasm seizures

Some epileptic spasms are classified into focal-onset seizures. However, the cortical network underlying this kind of spasm seizure is not yet clear. Four patients with epileptic spasms who underwent intracranial electrode implantation and focal resection surgery were studied. All the patients had good outcomes, and three of them with intellectual disability showed improved intelligence after surgery. The power spectra characteristics of electrocorticography and the dynamic functional network changes of epileptic spasms were investigated. Electrocorticography power in the resected zone peaked 0.5 seconds before the clinical seizure onset and was especially prominent in the γ and ripple bands. The functional network analysis showed particular dynamic patterns of high-frequency activity among the resected zone, sensorimotor cortex, and the other region. In the gamma band, during the interictal segment, the information flow from the resected zone and the other region to the sensorimotor cortex was prominent. During the preictal segment, the information flow from the resected zone and sensorimotor cortex to the other region became stronger. In the ripple band, during the interictal segment, the information flow from the resected zone to the sensorimotor cortex and the other region was high. During the preictal segment, the information flow between the resected zone and sensorimotor cortex became stronger. Our results suggest that the sensorimotor cortex is a requisite for spasm seizure initiation, and the ripple activity loop between the resected zone and sensorimotor cortex may give rise to the seizure onset with the help of the gamma activity loop between the sensorimotor cortex and the other region for activation spreading.

Neurorestoration: Advances in human brain–computer interface using microelectrode arrays

Neural damage has been a great challenge to the medical field for a very long time. The emergence of brain–computer interfaces (BCIs) offered a new possibility to enhance the activity of daily living and provide a new formation of entertainment for those with disabilities. Intracortical BCIs, which require the implantation of microelectrodes, can receive neuronal signals with a high spatial and temporal resolution from the individual’s cortex. When BCI decoded cortical signals and mapped them to external devices, it displayed the ability not only to replace part of the human motor function but also to help individuals restore certain neurological functions. In this review, we focus on human intracortical BCI research using microelectrode arrays and summarize the main directions and the latest results in this field. In general, we found that intracortical BCI research based on motor neuroprosthetics and functional electrical stimulation have already achieved some simple functional replacement and treatment of motor function. Pioneering work in the posterior parietal cortex has given us a glimpse of the potential that intracortical BCIs have to control external devices and receive various sensory information.

Symmetry of ictal slow waves may predict the outcomes of corpus callosotomy for epileptic spasms

We aimed to analyse the ictal electrographic changes on scalp electroencephalography (EEG), focusing on high-voltage slow waves (HVSs) in children with epileptic spasms (ES) and tonic spasms (TS) and then identified factors associated with corpus callosotomy (CC) outcomes. We enrolled 17 patients with ES/TS who underwent CC before 20 years of age. Post-CC Engel’s classification was as follows: I in 7 patients, II in 2, III in 4, and IV in 4. Welch’s t-test was used to analyse the correlation between ictal HVSs and CC outcomes based on the following three symmetrical indices: (1) negative peak delay: interhemispheric delay between negative peaks; (2) amplitude ratio: interhemispheric ratio of amplitude values for the highest positive peaks; and (3) duration ratio: interhemispheric ratio of slow wave duration. Ages at CC ranged from 17–237 months. Four to 15 ictal EEGs were analysed for each patient. The negative peak delay, amplitude ratio and duration ratio ranged from 0–530 ms, 1.00–7.40 and 1.00–2.74, respectively. The negative peak delay, amplitude ratio and duration ratio were significantly higher in the seizure residual group (p = 0.017, <0.001, <0.001, respectively). Symmetry of ictal HVSs may predict favourable outcomes following CC for ES/TS.

High Frequency Oscillations in Epilepsy: Detection Methods and Considerations in Clinical Application

High frequency oscillations (HFOs) is a brain activity observed in electroencephalography (EEG) in frequency ranges between 80–500 Hz. HFOs can be classified into ripples (80–200 Hz) and fast ripples (200–500 Hz) by their distinctive characteristics. Recent studies reported that both ripples and fast fipples can be regarded as a new biomarker of epileptogenesis and ictogenesis. Previous studies verified that HFOs are clinically important both in patients with mesial temporal lobe epilepsy and neocortical epilepsy. Also, in epilepsy surgery, patients with higher resection ratio of brain regions with HFOs showed better outcome than a group with lower resection ratio. For clinical application of HFOs, it is important to delineate HFOs accurately and discriminate them from artifacts. There have been technical improvements in detecting HFOs by developing various detection algorithms. Still, there is a difficult issue on discriminating clinically important HFOs among detected HFOs, where both quantitative and subjective approaches are suggested. This paper is a review on published HFO studies focused on clinical findings and detection techniques of HFOs as well as tips for clinical applications.

Transcranial Direct Current Stimulation for Patients With Pharmacoresistant Epileptic Spasms: A Pilot Study

Background: Epileptic spasms (ES) is a severe seizure type and lack of adequate methods for controlling of clinical attacks. Previous studies have indicated that cathodal transcranial direct current stimulation (tDCS) reduces seizure frequency for patients with epilepsy. ES are proposed to have a focal cortical origin. We hypothesized that patients with ES exhibit hyperactive network hubs in the parietal lobe, and that cathodal tDCS targeting the bilateral parietal region can reduce seizure frequency in patients with pharmacoresistant ES.

Materials and Methods: The present study consisted of three basic phases: (a) a pre-treatment monitoring period for 14 days; (b) a consecutive 14-day treatment period during which patients were treated with 1 or 2 mA cathode tDCS for 40 min once per day; (c) and a follow-up period for at least 28 days. During the first 20 min of treatment, the cathode was placed over the right parietal lobe (P4) with the reference electrode over the contralateral supra-orbital area. In the second 20 min, the cathode was placed over the left parietal lobe (P3), with the reference electrode over the contralateral supra-orbital area. All patients received active tDCS treatment, and some patients underwent more than one treatment block. Patients maintained a seizure diary throughout the study. Antiepileptic drug therapy remained unchanged throughout the study. K-related samples Friedman tests and two-related samples tests were used to analyze data from all patients.

Results: Seven patients with pharmacoresistant ES were included, receiving a total of eighteen 14-day blocks of tDCS treatment. We observed a significant difference in seizure frequency at the second month (p = 0.028, unadjusted), as well as a trend toward decreased seizure frequency at the fourth month (p = 0.068, unadjusted) of the first follow-up, relative to baseline. Three of seven patients (42.9%) exhibited sustained seizure reduction, while one (14.3%) experienced a short-term reduction in seizure frequency following cathodal tDCS treatment. Treatment was well tolerated in all patients.

Conclusions: Repeated tDCS with the cathode placed over the bilateral parietal region is safe and may be effective for reducing seizure frequency in a subgroup of patients with pharmacoresistant ES.

Interictal spike connectivity in human epileptic neocortex

OBJECTIVE

Interictal spikes are a biomarker of epilepsy, yet their precise roles are poorly understood. Using long-term neocortical recordings from epileptic patients, we investigated the spatial-temporal propagation patterns of interictal spiking.

METHODS

Interictal spikes were detected in 10 epileptic patients. Short time direct directed transfer function was used to map the spatial-temporal patterns of interictal spike onset and propagation across different cortical topographies.

RESULTS

Each patient had unique interictal spike propagation pattern that was highly consistent across times, regardless of the frequency band. High spiking brain regions were often not spike onset regions. We observed frequent spike propagations to shorter distances and that the central sulcus forms a strong barrier to spike propagation. Spike onset and seizure onset seemed to be distinct networks in most cases.

CONCLUSIONS

Patients in epilepsy have distinct and unique network of causal propagation pattern which are very consistent revealing the underlying epileptic network. Although spike are epileptic biomarkers, spike origin and seizure onset seems to be distinct in most cases.

SIGNIFICANCE

Understanding patterns of interictal spike propagation could lead to the identification patient-specific epileptic networks amenable to surgical or other treatments.

Surgical and developmental outcomes of corpus callosotomy for West syndrome in patients without MRI lesions

OBJECTIVE

This retrospective study was designed to assess the impact of corpus callosotomy (CC) in patients with intractable West syndrome (WS) without lesions on magnetic resonance imaging (MRI).

METHODS

This study involved 56 patients with WS who underwent CC between January 2000 and December 2014. Seizure outcomes and changes in psychomotor development were analyzed.

RESULTS

Mean age at the onset of epilepsy and at the time of CC was 5.1 and 22.6 months, respectively. Mean duration of epilepsy before CC was 17.6 months. Video-electroencephalography (EEG) monitoring showed bilateral ictal and interictal abnormalities before CC. Mean follow-up duration was 36.6 months. At final follow-up, seizure outcomes after CC were seizure-free in 18 patients (32.1%), excellent (E: >80% reduction in seizure frequency) in 15 (26.8%), good (G: >50% reduction) in 10 (17.9%), and poor (P: <50% reduction) in 13 (23.2%). Epileptic spasms (ES) were eliminated in 24 patients (42.9%). However, tonic seizure (TS) outcomes were poor (P < 0.05). Of preoperative predictive factors related to seizure outcome, developmental delay before epilepsy onset correlated with poor outcome (P < 0.05). One year post-CC, 6 patients (10.7%) had no epileptic abnormality on EEG, 19 (33.9%) had lateralized epileptic abnormalities, and 31 (55.4%) had bilateral asynchronous epileptic abnormalities. All patients without epileptic discharge achieved seizure freedom. Fifteen of 19 (78.9%) patients in the lateralized group and 12 of 31 (38.7%) in the bilateral asynchronous group had worthwhile outcomes (F + E). The patterns of EEG changes after CC correlated with seizure outcome (P < 0.01). Progressive declines in developmental quotient were prevented in patients with worthwhile outcomes.

SIGNIFICANCE

CC represents an important therapeutic option for patients with WS without resectable MRI lesions. Transcallosal seizure bilateralization is critical for bilateral ES generation. Early identification of potential CC candidates and surgical intervention are important for better seizure control and cognitive capacity preservation before severe developmental delay development.

Blending Electronics with the Human Body: A Pathway toward a Cybernetic Future

At the crossroads of chemistry, electronics, mechanical engineering, polymer science, biology, tissue engineering, computer science, and materials science, electrical devices are currently being engineered that blend directly within organs and tissues. These sophisticated devices are mediators, recorders, and stimulators of electricity with the capacity to monitor important electrophysiological events, replace disabled body parts, or even stimulate tissues to overcome their current limitations. They are therefore capable of leading humanity forward into the age of cyborgs, a time in which human biology can be hacked at will to yield beings with abilities beyond their natural capabilities. The resulting advances have been made possible by the emergence of conformal and soft electronic materials that can readily integrate with the curvilinear, dynamic, delicate, and flexible human body. This article discusses the recent rapid pace of development in the field of cybernetics with special emphasis on the important role that flexible and electrically active materials have played therein.

Longitudinal Findings of MRI and PET in West Syndrome with Subtle Focal Cortical Dysplasia

BACKGROUND AND PURPOSE

Despite the development of neuroimaging, identification of focal cortical dysplasia remains challenging. The purpose of this study was to show the longitudinal changes of MR imaging and FDG-PET in patients with West syndrome and subtle focal cortical dysplasia.

MATERIALS AND METHODS

Among 52 consecutive patients with West syndrome, 4 were diagnosed with subtle focal cortical dysplasia on 3T MR imaging. MR imaging and PET findings were evaluated longitudinally at onset and at 12 and 24 months of age.

RESULTS

At the onset of West syndrome, MR imaging demonstrated focal signal abnormalities of the subcortical white matter in 2 patients. In the other 2 patients, focal subcortical high-intensity signals became visible on follow-up T2WI as myelination progressed. PET at onset showed focal cortical hypometabolism in 3 patients, with 1 of these patients also having focal hypermetabolism and 1 having normal findings. On PET at 24 months, hypometabolism persisted in 2 patients and disappeared in 1, and hypermetabolism disappeared in 1. In 1 patient with normal MR imaging and PET findings at onset, focal hyperintensity and hypometabolism first appeared at 24 months of age. The findings on MR imaging and PET in these patients evolved differently with brain maturation and the clinical course.

CONCLUSIONS

Subtle focal cortical dysplasia can be undetectable on MR imaging at the onset of West syndrome and is not always accompanied by hypometabolism or hypermetabolism on PET. Longitudinal MR imaging and PET studies may be useful for detecting such lesions. Even in West syndrome with a congenital structural abnormality, PET findings evolve differently with brain maturation and the clinical condition.

Multimodal localization and surgery for epileptic spasms of focal origin: a review

Epileptic spasms (ES) are a common manifestation of intractable epilepsy in early life and can lead to devastating neurodevelopmental consequences. Epilepsy surgery for ES is challenging because of inherent difficulties in localizing the epileptogenic zone in affected infants and children. However, recent clinical series of resective neurosurgery for ES suggest that not only is surgery a viable option for appropriately selected patients, but postoperative seizure outcomes can be similar to those achieved in other types of focal epilepsy. Increased awareness of ES as a potentially focal epilepsy, along with advances in neuroimaging and invasive monitoring technologies, have led to the ability to surgically treat many patients with ES who were previously not considered surgical candidates. In this study, the authors review the current state of epilepsy surgery for ES. Specifically, they address how advances in neuroimaging and invasive monitoring have facilitated patient selection, presurgical evaluation, and ultimately, resection planning.

A convex-shaped, PDMS-parylene hybrid multichannel ECoG-electrode array

Long-term electrode implant is a challenge for successful brain-computer interfaces (BCIs). It is well known that electrocorticography (ECoG) using flexible planar electrodes is more suitable for long-term implants than intracortical neural recordings using penetrative electrodes. In this study, we propose a convex-shaped, PDMS-parylene hybrid multi-electrode array for long-term stable ECoG recording on the brain or the spinal cord. The electrode array consists of 10 gold recording sites which show impedance values between 50 and 70 kOhm at 1 kHz with a diameter of 100 μm. It is designed like octopus's leg to tightly adhere to the ellipsoidal brain. To assess its performance, epidural ECoG recordings were performed from the main olfactory bulb (MOB) of an anesthetized rat during odor stimulation. The odor-evoked response was shown with an increase of the power in the beta band.

Strong coupling between slow oscillations and wide fast ripples in children with epileptic spasms: Investigation of modulation index and occurrence rate

OBJECTIVE

Epileptic spasms (ES) often become drug-resistant. To reveal the electrophysiological difference between children with ES (ES+) and without ES (ES-), we compared the occurrence rate (OR) of high-frequency oscillations (HFOs) and the modulation index (MI) of coupling between slow and fast oscillations. In ES+, we hypothesized that (1) pathological HFOs are more widely distributed and (2) slow oscillations show stronger coupling with pathological HFOs than in ES-.

METHODS

We retrospectively reviewed 24 children with drug-resistant multilobar onset epilepsy, who underwent intracranial video electroencephalography prior to multilobar resections. We measured the OR of HFOs and determined the electrodes with a high rate of HFOs by cluster analysis. We calculated MI, which reflects the degree of coupling between HFO (ripple/fast ripple [FR]) amplitude and 5 different frequency bands of delta and theta activities (0.5-1 Hz, 1-2 Hz, 2-3 Hz, 3-4 Hz, 4-8 Hz).

RESULTS

In ES+ (n = 10), the OR_(FRs) , the number of electrodes with high-rate FRs, and the MI_{(FRs & 3-4 Hz)} in all electrodes were significantly higher than in ES- (n = 14). In both the ES+ and ES- groups, MI_{(ripples/FRs & 3-4 Hz)} was the highest among the 5 frequency bands. Within the good seizure outcome group, the OR_(FRs) and the MI_{(FRs & 3-4 Hz)} in the resected area in ES+ were significantly higher than in ES- (OR_[FRs] , P = .04; MI_{[FRs & 3-4 Hz]} , P = .04).

SIGNIFICANCE

In ES+, the larger number of high-rate FR electrodes indicates more widespread epileptogenicity than in ES-. High values of OR_(FRs) and MI_{(FRs & 3-4 Hz)} in ES+ compared to ES- are a signature of the severity of epileptogenicity. We proved that ES+ children who achieved seizure freedom following multilobar resections exhibited strong coupling between slow oscillations and FRs.

Non-invasive, multimodal analysis of cortical activity, blood volume and neurovascular coupling in infantile spasms using EEG-fNIRS monitoring

Although infantile spasms can be caused by a variety of etiologies, the clinical features are stereotypical. The neuronal and vascular mechanisms that contribute to the emergence of infantile spasms are not well understood. We performed a multimodal study by simultaneously recording electroencephalogram and functional Near-infrared spectroscopy in an intentionally heterogeneous population of six children with spasms in clusters. Regardless of the etiology, spasms were accompanied by two phases of hemodynamic changes; an initial change in the cerebral blood volume (simultaneously with each spasm) followed by a neurovascular coupling in all children except for the one with a large porencephalic cyst. Changes in cerebral blood volume, like the neurovascular coupling, occurred over frontal areas in all patients regardless of any brain damage suggesting a diffuse hemodynamic cortical response. The simultaneous motor activation and changes in cerebral blood volume might result from the involvement of the brainstem. The inconstant neurovascular coupling phase suggests a diffuse activation of the brain likely resulting too from the brainstem involvement that might trigger diffuse changes in cortical excitability.

Spatiotemporal Mapping of Interictal Spike Propagation: A Novel Methodology Applied to Pediatric Intracranial EEG Recordings

Synchronized cortical activity is implicated in both normative cognitive functioning and many neurologic disorders. For epilepsy patients with intractable seizures, irregular synchronization within the epileptogenic zone (EZ) is believed to provide the network substrate through which seizures initiate and propagate. Mapping the EZ prior to epilepsy surgery is critical for detecting seizure networks in order to achieve postsurgical seizure control. However, automated techniques for characterizing epileptic networks have yet to gain traction in the clinical setting. Recent advances in signal processing and spike detection have made it possible to examine the spatiotemporal propagation of interictal spike discharges across the epileptic cortex. In this study, we present a novel methodology for detecting, extracting, and visualizing spike propagation and demonstrate its potential utility as a biomarker for the EZ. Eighteen presurgical intracranial EEG recordings were obtained from pediatric patients ultimately experiencing favorable (i.e., seizure-free, n = 9) or unfavorable (i.e., seizure-persistent, n = 9) surgical outcomes. Novel algorithms were applied to extract multichannel spike discharges and visualize their spatiotemporal propagation. Quantitative analysis of spike propagation was performed using trajectory clustering and spatial autocorrelation techniques. Comparison of interictal propagation patterns revealed an increase in trajectory organization (i.e., spatial autocorrelation) among Sz-Free patients compared with Sz-Persist patients. The pathophysiological basis and clinical implications of these findings are considered.

Unilobar surgery for symptomatic epileptic spasms

Objective

To assess factors associated with favorable seizure outcome after surgery for symptomatic epileptic spasms and improve knowledge on pathophysiology of this seizure type.

Methods

Inclusion criteria were: (1) age between 6 months and 15 years at surgery; (2) active epileptic spasms; (3) follow‐up after surgery >1 year.

Results

We retrospectively studied 80 children (aged 1.3 ± 2 years at seizure onset; 5.8 ± 4 years at surgery, 11.7 ± 5.7 years at last follow up). Magnetic resonance imaging (MRI) revealed structural abnormalities in 77/80 patients (96.3%; unilateral in 69: 89.6%). We performed invasive recordings in 24 patients (30%). In 21 patients in whom MRI or histopathology detected a lesion, electrodes exploring it constantly captured initial ictal activity at spasm onset. Fifty‐eight patients (72.5%) underwent unilobar and 22 (27.5%) multilobar or hemispheric procedures. At last follow‐up, 49 patients (61.3%) were in Engel class I. Multivariate logistic models showed completeness of resection of the seizure onset zone (OR = 0.016, 95%CI: 0.002, 0.122) and of the MRI visible lesion (OR = 0.179, 95% CI: 0.032, 0.999) to be significantly associated with Engel class IA outcome. Unfavorable outcome was associated with an older age at surgery, when it reflected a longer duration of epilepsy (OR = 1.383, 95% CI: 0.994,1.926).

Interpretation

Data emerging from invasive recordings and the good seizure outcome following removal of discrete epileptogenic lesions support a focal cortical origin of spasms. In patients with discrete epileptogenic lesions, the pragmatic approach to surgery should follow the same principles applied to focal epilepsy favoring, whenever possible, unilobar, one‐stage resections.

Intraoperative video-rate hemodynamic response assessment in human cortex using snapshot hyperspectral optical imaging

Using light, we are able to visualize the hemodynamic behavior of the brain to better understand neurovascular coupling and cerebral metabolism. In vivo optical imaging of tissue using endogenous chromophores necessitates spectroscopic detection to ensure molecular specificity as well as sufficiently high imaging speed and signal-to-noise ratio, to allow dynamic physiological changes to be captured, isolated, and used as surrogate of pathophysiological processes. An optical imaging system is introduced using a 16-bands on-chip hyperspectral camera. Using this system, we show that up to three dyes can be imaged and quantified in a tissue phantom at video-rate through the optics of a surgical microscope. In vivo human patient data are presented demonstrating brain hemodynamic response can be measured intraoperatively with molecular specificity at high speed.

Epilepsy surgery in pediatric epileptic encephalopathy: when interictal EEG counts the most

PURPOSE

Traditionally, seizure onset localization in ictal electro-encephalography (EEG) is the main factor guiding resective epilepsy surgery. The situation is often different in infantile epileptic encephalopathy. We demonstrate the importance of the underrated interictal (rather than ictal) surface EEG in informing decision-making in epilepsy surgery for children with epileptic encephalopathy caused by subtle focal cortical dysplasia (FCD).

METHODS

We present a small case series of three children who had an epileptic encephalopathy with either epileptic spasms or tonic seizures. All three were thought initially to have normal neuroimaging.

RESULTS

Ictal EEG localizing features were seen in none and lateralizing features were seen only clinically in one of the three. However, the interictal EEG showed persistent and consistent focal irregular slowing in all, particularly after medically resolving the diffuse encephalopathy. Subtle FCDs were uncovered in all. Surgery was performed in all with excellent outcome.

CONCLUSION

In infantile epileptic encephalopathy caused by subtle FCD, the often underrated interictal surface EEG (particularly persistent foal irregular slowing) informs the most; not only to the target area for surgical resection but also to its extent. This may negate the need for unnecessary and sometimes non-informative invasive monitoring in these cases. A matter of "zooming out" to define the extent of a resectable abnormality rather than "zooming in" to define a seemingly localized epileptic focus that may change with time.

High-Performance Bioinstrumentation for Real-Time Neuroelectrochemical Traumatic Brain Injury Monitoring

Traumatic brain injury (TBI) has been identified as an important cause of death and severe disability in all age groups and particularly in children and young adults. Central to TBIs devastation is a delayed secondary injury that occurs in 30-40% of TBI patients each year, while they are in the hospital Intensive Care Unit (ICU). Secondary injuries reduce survival rate after TBI and usually occur within 7 days post-injury. State-of-art monitoring of secondary brain injuries benefits from the acquisition of high-quality and time-aligned electrical data i.e., ElectroCorticoGraphy (ECoG) recorded by means of strip electrodes placed on the brains surface, and neurochemical data obtained via rapid sampling microdialysis and microfluidics-based biosensors measuring brain tissue levels of glucose, lactate and potassium. This article progresses the field of multi-modal monitoring of the injured human brain by presenting the design and realization of a new, compact, medical-grade amperometry, potentiometry and ECoG recording bioinstrumentation. Our combined TBI instrument enables the high-precision, real-time neuroelectrochemical monitoring of TBI patients, who have undergone craniotomy neurosurgery and are treated sedated in the ICU. Electrical and neurochemical test measurements are presented, confirming the high-performance of the reported TBI bioinstrumentation.

Nociceptive Local Field Potentials Recorded from the Human Insula Are Not Specific for Nociception

The insula, particularly its posterior portion, is often regarded as a primary cortex for pain. However, this interpretation is largely based on reverse inference, and a specific involvement of the insula in pain has never been demonstrated. Taking advantage of the high spatiotemporal resolution of direct intracerebral recordings, we investigated whether the human insula exhibits local field potentials (LFPs) specific for pain. Forty-seven insular sites were investigated. Participants received brief stimuli belonging to four different modalities (nociceptive, vibrotactile, auditory, and visual). Both nociceptive stimuli and non-nociceptive vibrotactile, auditory, and visual stimuli elicited consistent LFPs in the posterior and anterior insula, with matching spatial distributions. Furthermore, a blind source separation procedure showed that nociceptive LFPs are largely explained by multimodal neural activity also contributing to non-nociceptive LFPs. By revealing that LFPs elicited by nociceptive stimuli reflect activity unrelated to nociception and pain, our results confute the widespread assumption that these brain responses are a signature for pain perception and its modulation.

Local field potentials elicited in the human insular cortex by painful stimuli reflect cortical activity that is unrelated to pain perception and so cannot be used as an objective measure of pain.

A widely accepted notion is that the insula, especially its posterior portion, plays a specific role in the perception of pain. This has led a number of researchers to consider activity recorded from this so-called “ouch zone” as an objective correlate of pain perception. We provide compelling evidence to the contrary. Using direct intracerebral recordings, we demonstrate that painful and nonpainful stimuli elicit very similar responses throughout the human insula. This observation argues against the notion that these responses reflect the brain activity through which pain emerges from nociception in the human brain. These findings have implications for basic theories, as well as for the development of diagnostic tests and the identification of therapeutic targets for the treatment of chronic pain. They question the use of these insular responses to assess the effects of pharmacological treatment or to assess pain in patients unable to communicate. Furthermore, they have legal implications, as they contradict the proposal that these responses could be used to determine unequivocally whether plaintiffs are truly experiencing the pain for which they are seeking redress. Finally, they undermine the rationale for neurosurgical procedures aiming at alleviating pain by targeting the posterior insula.

Occurrence of bilaterally independent epileptic spasms after a corpus callosotomy in West syndrome

We report a patient with intractable West syndrome whose epileptic spasms (ESs) were initially bilaterally synchronous, as is typical; after a complete corpus callosotomy, however, bilaterally independent ESs originated in either hemisphere. Activity of probable cortical origin associated with ESs was detected by observing ictal gamma oscillations. Brain MRI revealed no structural abnormality before surgery. This case suggests that ESs with a hemispheric origin may appear generalized because of synchronizing effects in the corpus callosum in some patients.

Surgical treatment for refractory epileptic spasms: The Detroit series

OBJECTIVE

We reviewed our experience of surgery for epileptic spasms (ES) with or without history of infantile spasms.

METHODS

Data were reviewed from 65 (33 male) patients with ES who underwent surgery between 1993 and 2014; palliative cases were excluded.

RESULTS

Mean age at surgery was 5.1 (range 0.2-19) years, with mean postsurgical follow-up of 45.3 (6-120) months. Mean number of anticonvulsants used preoperatively was 4.2 (2-8), which decreased to 1.2 (0-4) postoperatively (p < 0.0001). Total hemispherectomy was the most commonly performed surgery (n = 20), followed by subtotal hemispherectomy (n = 17), multilobar resection (n = 13), lobectomy (n = 7), tuberectomy (n = 6), and lobectomy + tuberectomy (n = 2), with International League Against Epilepsy (ILAE) class I outcome in 20, 10, 7, 6, 3, and 0 patients, respectively (total 46/65 (71%); 22 off medication). Shorter duration of epilepsy (p = 0.022) and presence of magnetic resonance imaging (MRI) lesion (p = 0.026) were independently associated with class I outcome. Of 34 patients operated <3 years after seizure onset, 30 (88%) achieved class I outcome. Thirty-seven (79%) of 47 patients with lesional MRI had class-I outcome, whereas 9 (50%) of 18 with normal MRI had class I outcome. Positron emission tomography (PET) scan was abnormal in almost all patients [61 (97%) of 63 with lateralizing/localizing findings in 56 (92%) of 61 patients, thus helping in surgical decision making and guiding subdural grid placements, particularly in patients with nonlesional MRI. Fifteen patients had postoperative complications, mostly minor.

SIGNIFICANCE

Curative epilepsy surgery in ES patients, with or without history of infantile spasms, is best accomplished at an early age and in those patients with lesional abnormalities on MRI with electroencephalography (EEG) concordance. Good outcomes can be achieved even when there is no MRI lesion but positive PET localization.

A practical, simple, and useful method of categorizing interictal EEG features in children

We introduce a simple scheme of categorizing interictal EEG in patients with pediatric epilepsy. Five patterns of EEG can be determined by using 2 interictal EEG domains: organization of the background activity and a morphology/topography of epileptiform discharges. These patterns relate to commonly recognized categories of pediatric epilepsy: familial epilepsies, genetic generalized epilepsies, self-limited epilepsies, epilepsies with encephalopathy, and focal structural epilepsies. Each group has distinguishable clinical presentations, inheritance patterns, and outcomes. This categorization may be a useful educational tool; it may also guide decisions about further testing and management.

Intracranial EEG analysis in tumor-related epilepsy: Evidence of distant epileptic abnormalities

OBJECTIVE

In patients with tumor-related epilepsy (TRE), surgery traditionally focuses on tumor resection; but identification and removal of associated epileptogenic zone may improve seizure outcome. Here, we study spatial relationship of tumor and seizure onset and early spread zone (SOSz). We also perform quantitative analysis of interictal epileptiform activities in patients with both TRE and non-lesional epilepsy in order to better understand the electrophysiological basis of epileptogenesis.

METHODS

Twenty-five patients (11 with TRE and 14 with non-lesional epilepsy) underwent staged surgery using intracranial electrodes. Tumors were outlined on MRI and images were coregistered with post-implantation CT images. For each electrode, distance to the nearest tumor margin was measured. Electrodes were categorized based on distance from tumor and involvement in seizure. Quantitative EEG analysis studying frequency, amplitude, power, duration and slope of interictal spikes was performed.

RESULTS

At least part of the SOSz was located beyond 1.5 cm from the tumor margin in 10/11 patients. Interictally, spike frequency and power were higher in the SOSz and spikes near tumor were smaller and less sharp. Interestingly, peritumoral electrodes had the highest spike frequencies and sharpest spikes, indicating greatest degree of epileptic synchrony. A complete resection of the SOSz resulted in excellent seizure outcome.

CONCLUSIONS

Seizure onset and early spread often involves brain areas distant from the tumor.

SIGNIFICANCE

Utilization of epilepsy surgery approach for TRE may provide better seizure outcome and study of the intracranial EEG may provide insight into pathophysiology of TRE.

The start and development of epilepsy surgery in Europe: a historical review

Epilepsy has not always been considered a brain disease, but was believed to be a demonic possession in the past. Therefore, trepanation was done not only for medical but also for religious or spiritual reasons, originating in the Neolithic period (3000 BC). The earliest documentation of trepanation for epilepsy is found in the writings of the Hippocratic Corpus and consisted mainly of just skull surgery. The transition from skull surgery to brain surgery took place in the middle of the nineteenth century when the insight of epilepsy as a cortical disorder of the brain emerged. This led to the start of modern epilepsy surgery. The pioneer countries in which epilepsy surgery was performed in Europe were the UK, Germany, and The Netherlands. Neurosurgical forerunners like Sir Victor Horsley, William Macewen, Fedor Krause, and Otfrid Foerster started with "modern" epilepsy surgery. Initially, epilepsy surgery was mainly done with the purpose to resect traumatic lesions or large surface tumours. In the course of the twentieth century, this changed to highly specialized microscopic navigation-guided surgery to resect lesional and non-lesional epileptogenic cortex. The development of epilepsy surgery in Southern Europe, which has not been described until now, will be elaborated in this manuscript. To summarize, in this paper, we provide (1) a detailed description of the evolution of European epilepsy surgery with special emphasis on the pioneer countries; (2) novel, never published information about the development of epilepsy surgery in Southern Europe; and (3) we review the historical dichotomy of invasive electrode implantation strategy (Anglo-Saxon surface electrodes versus French-Italian stereoencephalography (SEEG) model).