Language organization and reorganization in epilepsy

Naming assessment in bilinguals for epilepsy surgery-adaptation and standardization of Boston Naming Test in India

PURPOSE

Naming difficulty is associated with temporal lobe epilepsy and a decline in naming ability is reported following dominant temporal lobe resections. The Boston Naming Test (BNT) is the most frequently used test for assessing naming ability. Evaluating naming ability in bilingual/multilingual populations is a challenge when participants are restricted to responding in one language. The study aimed to adapt and standardize the BNT as a valid clinical tool for evaluating bilingual/multilingual people undergoing epilepsy surgery in urban India.

RESULTS

Culture-appropriate adaptations were done, and participants were allowed to respond in any language. Data from 197 participants showed a strong education effect. The adaptation showed strong internal consistency, reliability, construct validity, and high sensitivity to left temporal lobe epilepsy performance.

CONCLUSIONS

The adapted version that allowed for flexible use of more than one language is a useful clinical tool for evaluating bilingual people undergoing epilepsy surgery.

Structural connectome combining DTI features predicts postoperative language decline and its recovery in glioma patients

OBJECTIVES

A decline in language function is a common complication after glioma surgery, affecting patients' quality of life and survival. This study predicts the postoperative decline in language function and whether it can be recovered based on the preoperative white matter structural network.

MATERIALS AND METHODS

Eighty-one right-handed patients with glioma involving the left hemisphere were retrospectively included. Their language function was assessed using the Western Aphasia Battery before and 1 week and 3 months after surgery. Structural connectome combining DTI features was selected to predict postoperative language decline and recovery. Nested cross-validation was used to optimize the models, evaluate the prediction performance of the models, and identify the most predictive features.

RESULTS

Five, seven, and seven features were finally selected as the predictive features in each model and used to establish predictive models for postoperative language decline (1 week after surgery), long-term language decline (3 months after surgery), and language recovery, respectively. The overall accuracy of the three models in nested cross-validation and overall area under the receiver operating characteristic curve were 0.840, 0.790, and 0.867, and 0.841, 0.778, and 0.901, respectively.

CONCLUSION

We used machine learning algorithms to establish models to predict whether the language function of glioma patients will decline after surgery and whether postoperative language deficit can recover, which may help improve the development of treatment strategies. The difference in features in the non-language decline or the language recovery group may reflect the structural basis for the protection and compensation of language function in gliomas.

CLINICAL RELEVANCE STATEMENT

Models can predict the postoperative language decline and whether it can recover in glioma patients, possibly improving the development of treatment strategies. The difference in selected features may reflect the structural basis for the protection and compensation of language function.

KEY POINTS

• Structural connectome combining diffusion tensor imaging features predicted glioma patients' language decline after surgery. • Structural connectome combining diffusion tensor imaging features predicted language recovery of glioma patients with postoperative language disorder. • Diffusion tensor imaging and connectome features related to language function changes imply plastic brain regions and connections.

Variability in Hemispheric Functional Segregation Phenotypes: A Review and General Mechanistic Model

Many functions of the human brain are organized asymmetrically and are subject to strong population biases. Some tasks, like speaking and making complex hand movements, exhibit left hemispheric dominance, whereas others, such as spatial processing and recognizing faces, favor the right hemisphere. While pattern of preference implies the existence of a stereotypical way of distributing functions between the hemispheres, an ever-increasing body of evidence indicates that not everyone follows this pattern of hemispheric functional segregation. On the contrary, the review conducted in this article shows that departures from the standard hemispheric division of labor are routinely observed and assume many distinct forms, each having a different prevalence rate. One of the key challenges in human neuroscience is to model this variability. By integrating well-established and recently emerged ideas about the mechanisms that underlie functional lateralization, the current article proposes a general mechanistic model that explains the observed distribution of segregation phenotypes and generates new testable hypotheses.

Neuropsychological assessment in pediatric epilepsy surgery: A French procedure consensus

Neuropsychological assessment is a mandatory part of the pre- and post-operative evaluation in pediatric epilepsy surgery. The neuropsychology task force of the ILAE - French Chapter aims to define a neuropsychological procedure consensus based on literature review and adapted for French practice. They performed a systematic review of the literature published between 1950 and 2023 on cognitive evaluation of individuals undergoing presurgical work-up and post-surgery follow-up and focused on the pediatric population aged 6-16. They classified publications listed in the PubMed database according to their level of scientific evidence. The systematic literature review revealed no study with high statistical power and only four studies using neuropsychological scales in their French version. Afterwards, the experts defined a neuropsychological consensus strategy in pediatric epilepsy surgery according to the psychometric determinants of cognitive tests, specificity of epilepsy, surgery context, French culture and literature reports. A common French neuropsychological procedure dedicated to pediatric epilepsy surgery is now available. This procedure could serve as a guide for the pre- and post-surgical work-up in French centers with pediatric epilepsy surgery programs. The main goal is to anticipate the functional risks of surgery, to support the postoperative outcome beyond the seizure-related one, while taking into consideration the plasticity and vulnerability of the immature brain and allowing the possibility of collaborative studies.

Application of the International Classification of Cognitive Disorders in Epilepsy (IC-CoDE) to frontal lobe epilepsy using multicenter data

RATIONALE

The International Classification of Cognitive Disorders in Epilepsy (IC-CoDE) was recently introduced as a consensus-based, empirically-driven taxonomy of cognitive disorders in epilepsy and has been effectively applied to patients with temporal lobe epilepsy (TLE). The purpose of this study was to apply the IC-CoDE to patients with frontal lobe epilepsy (FLE) using national multicenter data.

METHODS

Neuropsychological data of 455 patients with FLE aged 16 years or older were available across four US-based sites. First, we examined test-specific impairment rates across sites using two impairment thresholds (1.0 and 1.5 standard deviations below the normative mean). Following the proposed IC-CoDE guidelines, patterns of domain impairment were determined based on commonly used tests within five cognitive domains (language, memory, executive functioning, attention/processing speed, and visuospatial ability) to construct phenotypes. Impairment rates and distributions across phenotypes were then compared with those found in patients with TLE for which the IC-CoDE classification was initially validated.

RESULTS

The highest rates of impairment were found among tests of naming, verbal fluency, speeded sequencing and set-shifting, and complex figure copy. The following IC-CoDE phenotype distributions were observed using the two different threshold cutoffs: 23-40% cognitively intact, 24-29% single domain impairment, 13-20% bi-domain impairment, and 18-33% generalized impairment. Language was the most common single domain impairment (68% for both thresholds) followed by attention and processing speed (15-18%). Overall, patients with FLE reported higher rates of cognitive impairment compared with patients with TLE.

CONCLUSIONS

These results demonstrate the applicability of the IC-CoDE to epilepsy syndromes outside of TLE. Findings indicated generally stable and reproducible phenotypes across multiple epilepsy centers in the U.S. with diverse sample characteristics and varied neuropsychological test batteries. Findings also highlight opportunities for further refinement of the IC-CoDE guidelines as the application expands.

Brain language networks and cognitive outcomes in children with frontotemporal lobe epilepsy

Introduction

Pediatric frontal and temporal lobe epilepsies (FLE, TLE) have been associated with language impairments and structural and functional brain alterations. However, there is no clear consensus regarding the specific patterns of cerebral reorganization of language networks in these patients. The current study aims at characterizing the cerebral language networks in children with FLE or TLE, and the association between brain network characteristics and cognitive abilities.

Methods

Twenty (20) children with FLE or TLE aged between 6 and 18 years and 29 age- and sex-matched healthy controls underwent a neuropsychological evaluation and a simultaneous functional near-infrared spectroscopy and electroencephalography (fNIRS-EEG) recording at rest and during a receptive language task. EEG was used to identify potential subclinical seizures in patients. We removed these time intervals from the fNIRS signal to investigate language brain networks and not epileptogenic networks. Functional connectivity matrices on fNIRS oxy-hemoglobin concentration changes were computed using cross-correlations between all channels.

Results and discussion

Group comparisons of residual matrices (=individual task-based matrix minus individual resting-state matrix) revealed significantly reduced connectivity within the left and between hemispheres, increased connectivity within the right hemisphere and higher right hemispheric local efficiency for the epilepsy group compared to the control group. The epilepsy group had significantly lower cognitive performance in all domains compared to their healthy peers. Epilepsy patients' local network efficiency in the left hemisphere was negatively associated with the estimated IQ (p = 0.014), suggesting that brain reorganization in response to FLE and TLE does not allow for an optimal cognitive development.

The effect of different brain lesions on the reorganization of language functions within the dominant hemisphere assessed with task-based BOLD-fMRI

BACKGROUND AND PURPOSE

Language reorganization has been described in brain lesions with respect to their location and timing, but little is known with respect to their etiology. We used fMRI to investigate the effects of different types of left hemisphere lesions (GL = gliomas, TLE = temporal lobe epilepsy and CA = cavernous angioma) on the topographic intra-hemispheric language plasticity, also considering their location.

METHODS

Forty-seven right-handed patients with 3 different left hemisphere lesions (16 GL, 15 TLE and 16 CA) and 17 healthy controls underwent BOLD fMRI with a verb-generation task. Euclidean distance was used to measure activation peak shifts among groups with respect to reference Tailarach coordinates of Inferior Frontal Gyrus, Superior Temporal Sulcus and Temporo-Parietal Junction. Mixed-model ANOVAs were used to test for differences in activation peak shifts.

RESULTS

Significant activation peak shifts were found in GL patients with respect both to HC and other groups (TLA and CA). In addition, in the same group of patients a significant effect of tumor location (anterior or posterior) was detected.

CONCLUSIONS

We demonstrated that intra-hemispheric language plasticity is influenced by the type of lesion affecting the left hemisphere and that fMRI is especially valuable in the preoperative assessment of such reorganization in glioma patients.

Task-Based and Resting-State Functional MRI in Observing Eloquent Cerebral Areas Personalized for Epilepsy and Surgical Oncology Patients: A Review of the Current Evidence

Functional magnetic resonance imaging (fMRI) is among the newest techniques of advanced neuroimaging that offer the opportunity for neuroradiologists, neurophysiologists, neuro-oncologists, and neurosurgeons to pre-operatively plan and manage different types of brain lesions. Furthermore, it plays a fundamental role in the personalized evaluation of patients with brain tumors or patients with an epileptic focus for preoperative planning. While the implementation of task-based fMRI has increased in recent years, the existing resources and evidence related to this technique are limited. We have, therefore, conducted a comprehensive review of the available resources to compile a detailed resource for physicians who specialize in managing patients with brain tumors and seizure disorders. This review contributes to the existing literature because it highlights the lack of studies on fMRI and its precise role and applicability in observing eloquent cerebral areas in surgical oncology and epilepsy patients, which we believe is underreported. Taking these considerations into account would help to better understand the role of this advanced neuroimaging technique and, ultimately, improve patient life expectancy and quality of life.

Intracerebral Electrophysiological Recordings to Understand the Neural Basis of Human Face Recognition

Understanding how the human brain recognizes faces is a primary scientific goal in cognitive neuroscience. Given the limitations of the monkey model of human face recognition, a key approach in this endeavor is the recording of electrophysiological activity with electrodes implanted inside the brain of human epileptic patients. However, this approach faces a number of challenges that must be overcome for meaningful scientific knowledge to emerge. Here we synthesize a 10 year research program combining the recording of intracerebral activity (StereoElectroEncephaloGraphy, SEEG) in the ventral occipito-temporal cortex (VOTC) of large samples of participants and fast periodic visual stimulation (FPVS), to objectively define, quantify, and characterize the neural basis of human face recognition. These large-scale studies reconcile the wide distribution of neural face recognition activity with its (right) hemispheric and regional specialization and extend face-selectivity to anterior regions of the VOTC, including the ventral anterior temporal lobe (VATL) typically affected by magnetic susceptibility artifacts in functional magnetic resonance imaging (fMRI). Clear spatial dissociations in category-selectivity between faces and other meaningful stimuli such as landmarks (houses, medial VOTC regions) or written words (left lateralized VOTC) are found, confirming and extending neuroimaging observations while supporting the validity of the clinical population tested to inform about normal brain function. The recognition of face identity - arguably the ultimate form of recognition for the human brain - beyond mere differences in physical features is essentially supported by selective populations of neurons in the right inferior occipital gyrus and the lateral portion of the middle and anterior fusiform gyrus. In addition, low-frequency and high-frequency broadband iEEG signals of face recognition appear to be largely concordant in the human association cortex. We conclude by outlining the challenges of this research program to understand the neural basis of human face recognition in the next 10 years.

Concordance of Lateralization Index for Brain Asymmetry Applied to Identify a Reliable Language Task

How can we determine which language task is relevant for examining functional hemispheric asymmetry? A problem in measuring brain asymmetry using functional magnetic resonance imaging lies in the uncertain reliability of the computed index regarding the “true” asymmetry degree. Strictly speaking, the results from the Wada test or direct cortical stimulation cannot be an exact “ground truth”, specifically for the degree of asymmetry. Therefore, we developed a method to evaluate task performance using reproducibility independent of the phenomenon of functional lateralization. Kendall’s coefficient of concordance (W) was used as the statistical measure. The underlying idea was that although various algorithms to compute the lateralization index show considerably different index values for the same data, a superior language task would reproduce similar individual ranking sequences across the algorithms; the high reproducibility of rankings across various index types would indicate a reliable task to investigate functional asymmetry regardless of index computation algorithms. Consequently, we found specificity for brain locations; a verb-generation task demonstrated the highest concordance across index types along with sufficiently high index values in the inferior frontal gyrus, whereas a narration–listening task demonstrated the highest concordance in the posterior temporo-parietal junction area.

Reliable change on the selective reminding test in a series of left-hemisphere language dominant patients with right temporal lobe epilepsy

The Selective Reminding Test (SRT) is widely used in pre-surgical evaluations for people with epilepsy; however, important characteristics such as reliability and stability over time within an epilepsy-specific control cohort are unclear. In this study, we document test-retest reliabilities, practice effects, and Reliable Change Indices (RCI) for this test in a sample of right temporal lobe epilepsy patients who are left hemisphere dominant for language and underwent surgical resection on the right temporal lobe. A sample of 101 adults with a right temporal lobe seizure focus (mean age = 38.5) was administered the SRT pre- and post-right temporal lobe surgery. Test-retest reliabilities were modest (r = 0.44-0.59). Practice effects were minimal (0.25-2.04). Reliable Change Indices were calculated and ranged from 4 to 26 depending on the SRT index. The RCI's indicate that relatively moderate to large changes on the SRT are needed for a change score to be considered a significant change in an individual's performance. The RCIs can be used to detect a reliable change in patients undergoing left temporal lobe epilepsy surgery who are at significant risk for verbal memory decline.

Quality of life after epilepsy surgery: How domain-specific cognitive changes impact QOL within the context of seizure outcome

PURPOSE

Neurosurgery is an effective treatment option for pharmacoresistant epilepsy. Although post-surgical seizure freedom is considered the primary goal of epilepsy surgery, other factors that impact Quality of Life (QOL) are also important to consider, including post-surgical cognitive changes. This study aimed to examine the impact of post-surgical cognitive changes on QOL in the context of seizure outcomes.

METHODS

Participants were 196 adults with focal epilepsy who underwent either frontal (n = 27) or temporal (n = 169) lobe resection. Each participant completed pre- and post-surgical neuropsychological evaluations, and cognitive composites were constructed for the following domains: language, attention/processing speed, memory, executive function, and visuospatial skill. The Quality of Life in Epilepsy (QOLIE-10) questionnaire was used to assess QOL. Seizure outcome was determined by seizure status six months post-surgery.

RESULTS

Eighty-one percent of patients were seizure-free post-surgery and generally reported improved QOL. While a significant portion of patient's demonstrated declines in language and verbal memory following surgery, only a decline in verbal memory was associated with worse QOL; however, this relationship was no longer significant after controlling for seizure outcome. Instead, reduced post-surgical QOL was primarily observed in those who experienced both seizure recurrence and a decline in executive function. Notably, depression was a significant covariate in all of the models.

CONCLUSIONS

The findings from this study improve our ability to counsel patients about the trade-off between cognitive decline and seizure remittance in the greater context of overall QOL. Reassuringly, it appears that QOL is improved regardless of cognitive changes when patients have good seizure outcomes. However, for those that experience a "double hit" (i.e., cognitive decline without seizure remission), post-surgical QOL may be reduced. Changes in depression also appear to play a crucial role in QOL outcomes.

Intact speech perception after resection of dominant hemisphere primary auditory cortex for the treatment of medically refractory epilepsy: illustrative case

BACKGROUND

In classic speech network models, the primary auditory cortex is the source of auditory input to Wernicke's area in the posterior superior temporal gyrus (pSTG). Because resection of the primary auditory cortex in the dominant hemisphere removes inputs to the pSTG, there is a risk of speech impairment. However, recent research has shown the existence of other, nonprimary auditory cortex inputs to the pSTG, potentially reducing the risk of primary auditory cortex resection in the dominant hemisphere.

OBSERVATIONS

Here, the authors present a clinical case of a woman with severe medically refractory epilepsy with a lesional epileptic focus in the left (dominant) Heschl's gyrus. Analysis of neural responses to speech stimuli was consistent with primary auditory cortex localization to Heschl's gyrus. Although the primary auditory cortex was within the proposed resection margins, she underwent lesionectomy with total resection of Heschl's gyrus. Postoperatively, she had no speech deficits and her seizures were fully controlled.

LESSONS

While resection of the dominant hemisphere Heschl's gyrus/primary auditory cortex warrants caution, this case illustrates the ability to resect the primary auditory cortex without speech impairment and supports recent models of multiple parallel inputs to the pSTG.

Brain Imaging in Epilepsy-Focus on Diffusion-Weighted Imaging

Epilepsy is a common neurological disorder; 1% of people worldwide have epilepsy. Differentiating epileptic seizures from other acute neurological disorders in a clinical setting can be challenging. Approximately one-third of patients have drug-resistant epilepsy that is not well controlled by current antiepileptic drug therapy. Surgical treatment is potentially curative if the epileptogenic focus is accurately localized. Diffusion-weighted imaging (DWI) is an advanced magnetic resonance imaging technique that is sensitive to the diffusion of water molecules and provides additional information on the microstructure of tissue. Qualitative and quantitative analysis of peri-ictal, postictal, and interictal diffusion images can aid the differential diagnosis of seizures and seizure foci localization. This review focused on the fundamentals of DWI and its associated techniques, such as apparent diffusion coefficient, diffusion tensor imaging, and tractography, as well as their impact on epilepsy in terms of differential diagnosis, epileptic foci determination, and prognosis prediction.

Neural Regulation of Cancer: Cancer-Induced Remodeling of the Central Nervous System

In recent years, there have been significant advances in understanding the neuronal influence on the biology of solid tumors such as prostate, pancreatic, gastric, and brain cancers. An increasing amount of experimental evidence across multiple tumor types strongly suggests the existence of bidirectional crosstalk between cancer cells and the neural microenvironment. However, unlike cancers affecting many solid organs, brain tumors, namely gliomas, can synaptically integrate into neural circuits and thus can exert a greater potential to induce dynamic remodeling of functional circuits resulting in long-lasting behavioral changes. The first part of the review describes dynamic changes in language, sensory, and motor networks following glioma development and presents evidence focused on how different patterns of glioma-induced cortical reorganization may predict the degree and time course of functional recovery in brain tumor patients. The second part focuses on the network and cellular-level mechanisms underlying glioma-induced cerebral reorganization. Finally, oncological and clinical factors influencing glioma-induced network remodeling in glioma patients are reviewed.

Brain mapping of emotional prosody in patients with drug-resistant temporal epilepsy: An indicator of plasticity

INTRODUCTION

Emotional prosody, a suprasegmental component of language, is predominantly processed by right temporo-frontal areas of the cerebral cortex. In temporal lobe epilepsy (TLE), brain disturbances affecting prosody processing frequently occur. This research assesses compensatory brain mechanisms of prosody processing in refractory TLE using fMRI.

METHODS

Patients with focal unilateral epilepsy, right (RTLE) (N = 19), left (LTLE) (N = 19), and healthy controls (CTRL) (N = 20) were evaluated during a prosody decoding fMRI task. The stimuli consisted in spoken numbers with different tones of voice (joy, fear, anger, neutral and silent trials). Participants were instructed to label the emotion with a keypad. "Joy" was removed from the analysis due to a high degree of variability. A lateralization index (LI) was used to see individual differences in the interhemispheric activations of each participant.

RESULTS

Behaviorally, The LTLE and RTLE groups did not differ significantly from each other neither from CTRL. In Negative Emotions versus Baseline contrast, the whole sample analysis showed extensive activations in bilateral superior temporal gyrus, bilateral precentral and post-central gyrus, right putamen, and left cerebellar vermis. Compared to the LTLE and CTRL, RTLE activated similar areas, but to a lesser extent. The LI analysis revealed significant differences in hemispheric laterality of the temporal lobe and the parietal lobe between RTLE compared to LTLE and CTRL, being the RTLE group lateralized towards the left, unlike the other two groups.

DISCUSSION

The LI indicated that, since the CTRL and the LTLE groups recruited putative prosodic regions, the RTLE lateralized prosody processing towards the left, recruiting contralateral nodes, homotopic to the putative areas of the prosody. Considering that the groups did not differ in prosody task performance, the findings suggest that, in the RTLE group, alternative brain nodes were recruited for the task, demonstrating plasticity.

A resting-state fMRI study of temporal lobe epilepsy using multivariate pattern analysis and Granger causality analysis

BACKGROUND AND PURPOSE

Understanding the pathogenesis of temporal lobe epilepsy (TLE) is essential for its diagnosis and treatment. The study aimed to explore regional homogeneity (ReHo) and changes in effective connectivity (EC) between brain regions in TLE patients, hoping to discover potential abnormalities in certain brain regions in TLE patients.

METHODS

Resting-state functional magnetic resonance data were collected from 23 TLE patients and 32 normal controls (NC). ReHo was used as a feature of multivariate pattern analysis (MVPA) to explore the ability of its alterations in identifying TLE. Based on the results of the MVPA, certain brain regions were selected as seed points to further explore alterations in EC between brain regions using Granger causality analysis.

RESULTS

MVPA results showed that the classification accuracy for the TLE and NC groups was 87.27%, and the right posterior cerebellum lobe, right lingual gyrus (LING_R), right cuneus (CUN_R), and left superior temporal gyrus (STG_L) provided significant contributions. Moreover, the EC from STG_L to right fusiform gyrus (FFG_R) and LING_R and the EC from CUN_R to the right occipital superior gyrus (SOG_R) and right occipital middle gyrus (MOG_R) were altered compared to the NC group.

CONCLUSION

The MVPA results indicated that ReHo abnormalities in brain regions may be an important feature in the identification of TLE. The enhanced EC from STG_L to FFG_R and LING_R indicates a shift in language processing to the right hemisphere, and the weakened EC from SOG_R and MOG_R to CUN_R may reveal an underlying mechanism of TLE.

Understanding Language Reorganization With Neuroimaging: How Language Adapts to Different Focal Lesions and Insights Into Clinical Applications

When the language-dominant hemisphere is damaged by a focal lesion, the brain may reorganize the language network through functional and structural changes known as adaptive plasticity. Adaptive plasticity is documented for triggers including ischemic, tumoral, and epileptic focal lesions, with effects in clinical practice. Many questions remain regarding language plasticity. Different lesions may induce different patterns of reorganization depending on pathologic features, location in the brain, and timing of onset. Neuroimaging provides insights into language plasticity due to its non-invasiveness, ability to image the whole brain, and large-scale implementation. This review provides an overview of language plasticity on MRI with insights for patient care. First, we describe the structural and functional language network as depicted by neuroimaging. Second, we explore language reorganization triggered by stroke, brain tumors, and epileptic lesions and analyze applications in clinical diagnosis and treatment planning. By comparing different focal lesions, we investigate determinants of language plasticity including lesion location and timing of onset, longitudinal evolution of reorganization, and the relationship between structural and functional changes.

Mapping of Language-and-Memory Networks in Patients With Temporal Lobe Epilepsy by Using the GE2REC Protocol

Preoperative mapping of language and declarative memory functions in temporal lobe epilepsy (TLE) patients is essential since they frequently encounter deterioration of these functions and show variable degrees of cerebral reorganization. Due to growing evidence on language and declarative memory interdependence at a neural and neuropsychological level, we propose the GE2REC protocol for interactive language-and-memory network (LMN) mapping. GE2REC consists of three inter-related tasks, sentence generation with implicit encoding (GE) and two recollection (2REC) memory tasks: recognition and recall. This protocol has previously been validated in healthy participants, and in this study, we showed that it also maps the LMN in the left TLE (N = 18). Compared to healthy controls (N = 19), left TLE (LTLE) showed widespread inter- and intra-hemispheric reorganization of the LMN through reduced activity of regions engaged in the integration and the coordination of this meta-network. We also illustrated how this protocol could be implemented in clinical practice individually by presenting two case studies of LTLE patients who underwent efficient surgery and became seizure-free but showed different cognitive outcomes. This protocol can be advantageous for clinical practice because it (a) is short and easy to perform; (b) allows brain mapping of essential cognitive functions, even at an individual level; (c) engages language-and-memory interaction allowing to evaluate the integrative processes within the LMN; (d) provides a more comprehensive assessment by including both verbal and visual modalities, as well as various language and memory processes. Based on the available postsurgical data, we presented preliminary results obtained with this protocol in LTLE patients that could potentially inform the clinical practice. This implies the necessity to further validate the potential of GE2REC for neurosurgical planning, along with two directions, guiding resection and describing LMN neuroplasticity at an individual level.

Neurobehavioural comorbidities of epilepsy: towards a network-based precision taxonomy

Cognitive and behavioural comorbidities are prevalent in childhood and adult epilepsies and impose a substantial human and economic burden. Over the past century, the classic approach to understanding the aetiology and course of these comorbidities has been through the prism of the medical taxonomy of epilepsy, including its causes, course, characteristics and syndromes. Although this 'lesion model' has long served as the organizing paradigm for the field, substantial challenges to this model have accumulated from diverse sources, including neuroimaging, neuropathology, neuropsychology and network science. Advances in patient stratification and phenotyping point towards a new taxonomy for the cognitive and behavioural comorbidities of epilepsy, which reflects the heterogeneity of their clinical presentation and raises the possibility of a precision medicine approach. As we discuss in this Review, these advances are informing the development of a revised aetiological paradigm that incorporates sophisticated neurobiological measures, genomics, comorbid disease, diversity and adversity, and resilience factors. We describe modifiable risk factors that could guide early identification, treatment and, ultimately, prevention of cognitive and broader neurobehavioural comorbidities in epilepsy and propose a road map to guide future research.

Clinical Speech fMRI in Children and Adolescents : Development of an Optimal Protocol and Analysis Algorithm

Purpose

In patients with drug-resistant focal epilepsy, surgical resection is often the only treatment option to achieve long-term seizure control. Prior to brain surgery involving potential language areas, identification of hemispheric language dominance is crucial. Our group developed and validated a functional magnetic resonance imaging (fMRI) battery of four pediatric language tasks. The present study aimed at optimizing fMRI data acquisition and analysis using these tasks.

Methods

We retrospectively analyzed speech fMRI examinations of 114 neuropediatric patients (age range 5.8–17.8 years) who were examined prior to possible epilepsy surgery. In order to evaluate hemispheric language dominance, 1–4 language tasks (vowel identification task VIT, word-chain task WCT, beep-story task BST, synonym task SYT) were measured.

Results

Language dominance was classified using fMRI activation in the 13 validly lateralizing ROIs (VLR) in frontal, temporal and parietal lobes and cerebellum of the recent validation study from our group: 47/114 patients were classified as left-dominant, 34/114 as bilateral and 6/114 as right-dominant. In an attempt to enlarge the set of VLR, we then compared for each task agreement of these ROI activations with the classified language dominance. We found four additional task-specific ROIs showing concordant activation and activation in ≥ 10 sessions, which we termed validly lateralizing (VLR_new). The new VLRs were: for VIT the temporal language area and for SYT the middle frontal gyrus, the intraparietal sulcus and cerebellum. Finally, in order to find the optimal sequence of measuring the different tasks, we analyzed the success rates of single tasks and all possible task combinations. The sequence 1) VIT 2) WCT 3) BST 4) SYT was identified as the optimal sequence, yielding the highest chance to obtain reliable results even when the fMRI examination has to be stopped, e.g., due to lack of cooperation.

Conclusion

Our suggested task order together with the enlarged set of VLR_new may contribute to optimize pediatric speech fMRI in a clinical setting.

Supplementary Information

The online version of this article (10.1007/s00062-021-01097-z) contains supplementary material, which is available to authorized users.

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

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

Language Familiarity and Proficiency Leads to Differential Cortical Processing During Translation Between Distantly Related Languages

In the midst of globalization, English is regarded as an international language, or Lingua Franca, but learning it as a second language (L2) remains still difficult to speakers of other languages. This is true especially for the speakers of languages distantly related to English such as Japanese. In this sense, exploring neural basis for translation between the first language (L1) and L2 is of great interest. There have been relatively many previous researches revealing brain activation patterns during translations between L1 and English as L2. These studies, which focused on language translation with close or moderate linguistic distance (LD), have suggested that the Broca area (BA 44/45) and the dorsolateral prefrontal cortex (DLPFC; BA 46) may play an important role on translation. However, the neural mechanism of language translation between Japanese and English, having large LD, has not been clarified. Thus, we used functional near infrared spectroscopy (fNIRS) to investigate the brain activation patterns during word translation between Japanese and English. We also assessed the effects of translation directions and word familiarity. All participants’ first language was Japanese and they were learning English. Their English proficiency was advanced or elementary. We selected English and Japanese words as stimuli based on the familiarity for Japanese people. Our results showed that the brain activation patterns during word translation largely differed depending on their English proficiency. The advanced group elicited greater activation on the left prefrontal cortex around the Broca’s area while translating words with low familiarity, but no activation was observed while translating words with high familiarity. On the other hand, the elementary group evoked greater activation on the left temporal area including the superior temporal gyrus (STG) irrespective of the word familiarity. These results suggested that different cognitive process could be involved in word translation corresponding to English proficiency in Japanese learners of English. These difference on the brain activation patterns between the advanced and elementary group may reflect the difference on the cognitive loads depending on the levels of automatization in one’s language processing.

Beta synchrony for expressive language lateralizes to right hemisphere in development

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.

Assessing risk: Characterizing language performance in pediatric patients with intractable epilepsy pre- and post-surgical resection

Neuropsychologists play an important role in assessing risk for post-surgical cognitive decline in pediatric patients with medically refractory epilepsy. Families, neurologists, and neurosurgeons are particularly concerned about the possibility for language decline for patients with a dominant, most often left, hemisphere epileptic focus and planned surgical resection. This study aims to describe language functioning in pediatric epilepsy patients following resection and evaluate the accuracy of a clinical approach of assessing risk. This study proposes a risk assessment method that considers a patient's pattern of lateralized dysfunction across cognitive domains, suspected neuroanatomical reorganization of language functions, and planned site of resection. Pediatric patients (N = 47) were dichotomized as being at minimal risk or at greater risk for post-surgical language decline based on the proposed risk assessment method. Retrospective chart review was utilized to obtain neuropsychological (Boston Naming Test and Weschler Vocabulary subtest) and clinical variables of interest. Patients in the minimal risk group demonstrated significantly improved BNT scores at post-surgery. Most patients remained stable in their Vocabulary knowledge. The proposed risk assessment method correctly classified patients 77% of the time based on BNT performance. Cluster analysis examining the individual components of the proposed method revealed three distinct patient subgroups. Clinical implications are discussed.

Central Nervous System Plasticity Influences Language and Cognitive Recovery in Adult Glioma

Gliomas exist within the framework of complex neuronal circuitry in which network dynamics influence both tumor biology and cognition. The generalized impairment of cognition or loss of language function is a common occurrence for glioma patients. The interface between intrinsic brain tumors such as gliomas and functional cognitive networks are poorly understood. The ability to communicate effectively is critically important for receiving oncological therapies and maintaining a high quality of life. Although the propensity of gliomas to infiltrate cortical and subcortical structures and disrupt key anatomic language pathways is well documented, there is new evidence offering insight into the network and cellular mechanisms underpinning glioma-related aphasia and aphasia recovery. In this review, we will outline the current understanding of the mechanisms of cognitive dysfunction and recovery, using aphasia as an illustrative model.

Comparison of Language and Memory Lateralization by Functional MRI and Wada Test in Epilepsy

The intracarotid sodium amobarbital procedure (ISAP or Wada test) lateralizes cerebral functions to the cerebral hemispheres preoperatively. Functional magnetic resonance imaging (fMRI) is increasingly used to characterize preoperative language and memory lateralization. In this study, concordance of fMRI with Wada was examined in patients with medically intractable seizures. The relationship of the distance between the epileptogenic focus to functional activation area with patients' post-operative deficits in language was also analyzed. 27 epilepsy patients with preoperative fMRI and Wada data were analyzed using established fMRI paradigms for language and memory. Activation of Broca's and Wernicke's areas were measured in three dimensions. Language and memory lateralization were determined, and standard neuropsychiatry Wada test procedures were used for comparison. The shortest distance between a language area to the border of surgical focus (LAD) was also measured and compared with postoperative language deficits. Our study found that concordance between fMRI and Wada testing was 0.41 (Kappa's 'fair to good' concordance) for language dominance and 0.1 (Kappa's 'poor' concordance) for memory. No significant correlation was found between LAD and post-op language deficit (p=0.439). A correlation was found between LAD and post-op memory deficit (p=0.049; the further distance from surgical lesion to language area is associated with less post-operative memory loss). Females demonstrated significantly increased postoperative seizure improvement (Fisher's p-value=0.0296; female=8; male=6). A significant association between handedness (right-handed subjects) and postoperative seizure improvement was found (p=0.02) as well as a significant trend for interaction of gender and handedness on postoperative seizure improvement (p=0.09). Overall, our results demonstrate fMRI as a useful preoperative adjunct to Wada testing for language lateralization in patients with medically intractable seizures.

Retained absolute pitch after selective amygdalohippocampectomy

This study assessed the pre-operative chronic condition and effect of epilepsy surgery in a 21-year-old Japanese woman with drug-resistant right temporal lobe epilepsy (TLE). For this patient, it was crucially important to preserve language and her music capabilities, including absolute pitch (AP), which is found in the general population at less than 0.1%. The patient became seizure free, and her AP capability was preserved after selective amygdalohippocampectomy in the non-dominant right hemisphere. Most of the neuropsychological test (WAIS-III and WMS-R) scores remained in the normal range, except for low scores in verbal memory and markedly improved attention/concentration index. The patient's pre- and postoperative brain function related to language and music capabilities were investigated using functional magnetic resonance imaging (fMRI) based on two language tasks and a music task (listening to melodies). While task performance was similar in pre- and postoperative examinations, her brain activation patterns markedly differed. The most striking difference was during the music task: areas with significant activation existed in the bilateral frontal and temporal lobes before surgery, whereas postoperative activation was confined to a very limited region in the left angular gyrus. The authors speculate that the surgery triggered some change in functional organization in the brain, which contributed to preserving her capabilities.

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A music student with drug-resistant temporal lobe epilepsy (TLE) became seizure free.

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Postoperative evaluation exhibited almost stable AP ability and cognitive function.

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Brain activation patterns on fMRI showed a notable change after surgery.

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Surgery possibly triggered some change in functional organization of the brain.

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Change in functional organization possibly contributed to preserving the capabilities.

Language network reorganization before and after temporal lobe epilepsy surgery

OBJECTIVE

Epilepsy surgery is the recommended treatment option for patients with drug-resistant temporal lobe epilepsy (TLE). This method offers a good chance of seizure freedom but carries a considerable risk of postoperative language impairment. The extremely variable neurocognitive profiles in surgical epilepsy patients cannot be fully explained by extent of resection, fiber integrity, or current task-based functional MRI (fMRI). In this study, the authors aimed to investigate pathology- and surgery-triggered language organization in TLE by using fMRI activation and network analysis as well as considering structural and neuropsychological measures.

METHODS

Twenty-eight patients with unilateral TLE (16 right, 12 left) underwent T1-weighted imaging, diffusion tensor imaging, and task-based language fMRI pre- and postoperatively (n = 15 anterior temporal lobectomy, n = 11 selective amygdalohippocampectomy, n = 2 focal resection). Twenty-two healthy subjects served as the control cohort. Functional connectivity, activation maps, and laterality indices for language dominance were analyzed from fMRI data. Postoperative fractional anisotropy values of 7 major tracts were calculated. Naming, semantic, and phonematic verbal fluency scores before and after surgery were correlated with imaging parameters.

RESULTS

fMRI network analysis revealed widespread, bihemispheric alterations in language architecture that were not captured by activation analysis. These network changes were found preoperatively and proceeded after surgery with characteristic patterns in the left and right TLEs. Ipsilesional fronto-temporal connectivity decreased in both left and right TLE. In left TLE specifically, preoperative atypical language dominance predicted better postoperative verbal fluency and naming function. In right TLE, left frontal language dominance correlated with good semantic verbal fluency before and after surgery, and left fronto-temporal language laterality predicted good naming outcome. Ongoing seizures after surgery (Engel classes ID-IV) were associated with naming deterioration irrespective of seizure side. Functional findings were not explained by the extent of resection or integrity of major white matter tracts.

CONCLUSIONS

Functional connectivity analysis contributes unique insight into bihemispheric remodeling processes of language networks after epilepsy surgery, with characteristic findings in left and right TLE. Presurgical contralateral language recruitment is associated with better postsurgical language outcome in left and right TLE.

Left hemispherectomy in older children and adolescents: outcome of cognitive abilities

PURPOSE

Hemispherectomy is an effective treatment option for pharmacoresistant epilepsy. Nevertheless, when high cortical functions are at risk during the presurgical evaluation, especially for older children, and for the left hemisphere, despite good seizure outcome, the anticipated decrease of cognitive functions may prevent a decision to perform surgery. The objective of this study is to report the cognitive outcome, based on verbal and performance intelligence skills, in a series of older children and adolescents who underwent left hemispherectomy, analyzing the risks (residual cognitive deficit) and benefits (seizure reduction) of surgery.

METHODS

We retrospectively analyzed pre- and postoperative clinical and neuropsychological data from our patients who underwent left hemispherectomy, aged between 6 and 18 years.

RESULTS

We included 15 patients, with a mean follow-up of 3.1 years, 12 patients (80%) were Engel I, and the other three were classified as Engel II, III, and IV. Nine patients were tested by Wechsler Scales of Intelligence; postsurgically all but one kept the same intellectual levels; verbal intelligence quotient (VIQ) remained unchanged in 13 and improved in one, whereas performance intelligence quotient (PIQ) decreased in four patients. Both Total Vineland and communication scores of Vineland Adaptive Behavior Scales were obtained in six patients: in all, scores were classified as deficient adaptive functioning pre- and postoperatively, remaining unchanged.

CONCLUSION

The evaluation of the remaining intellectual abilities after left hemispherectomy in older children and adolescents is useful to discuss the risks and benefits of this surgery, enabling better and safer decisions regarding surgical indications and timing.

Atypical language localization in right temporal lobe epilepsy: An fMRI case report

We report a 41- year-old, left-handed patient with drug-resistant right temporal lobe epilepsy (TLE). Presurgical fMRI was conducted to examine whether the patient had language functioning in the right hemisphere given that left-handedness is associated with a higher prevalence of right hemisphere dominance for language. The fMRI results revealed bilateral activation in Broca's and Wernicke's areas and activation of eloquent cortex near the region of planned resection in the right temporal lobe. Due to right temporal language-related activation, the patient underwent an awake right-sided temporal lobectomy with intraoperative language mapping. Intraoperative direct cortical stimulation (DCS) was conducted in the regions corresponding to the fMRI activation, and the patient showed language abnormalities, such as paraphasic errors, and speech arrest. The decision was made to abort the planned anterior temporal lobe procedure, and the patient instead underwent a selective amygdalohippocampectomy via the Sylvian fissure at a later date. Post-operatively the patient was seizure-free with no neurological deficits. Taken together, the results support previous findings of right hemisphere language activation in left-handed individuals, and should be considered in cases in which presurgical localization is conducted for left-hand dominant patients undergoing neurosurgical procedures.

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The report evaluates evidence for the possibility of right hemisphere language activation in a left-handed right TLE patient

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The results of the fMRI tasks showed bilateral speech regions, such as left and right Broca's area and Wernicke's area

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The results support previous findings of right hemisphere language activation in left-handed individuals

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The report discusses the value of fMRI of language tasks for presurgical planning in epilepsy cases

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Report highlights how fMRI findings can alter surgical strategy and how intraoperative brain mapping validates these findings

Mapping language networks and their association with verbal abilities in paediatric epilepsy using MEG and graph analysis

Recent theoretical models of language have emphasised the importance of integration within distributed networks during language processing. This is particularly relevant to young patients with epilepsy, as the topology of the functional network and its dynamics may be altered by the disease, resulting in reorganisation of functional language networks. Thus, understanding connectivity within the language network in patients with epilepsy could provide valuable insights into healthy and pathological brain function, particularly when combined with clinical correlates. The objective of this study was to investigate interactions within the language network in a paediatric population of epilepsy patients using measures of MEG phase synchronisation and graph-theoretical analysis, and to examine their association with language abilities. Task dependent increases in connectivity were observed in fronto-temporal networks during verb generation across a group of 22 paediatric patients (9 males and 13 females; mean age 14 years). Differences in network connectivity were observed between patients with typical and atypical language representation and between patients with good and poor language abilities. In addition, node centrality in left frontal and temporal regions was significantly associated with language abilities, where patients with good language abilities had significantly higher node centrality within inferior frontal and superior temporal regions of the left hemisphere, compared to patients with poor language abilities. Our study is one of the first to apply task-based measures of MEG network synchronisation in paediatric epilepsy, and we propose that these measures of functional connectivity and node centrality could be used as tools to identify critical regions of the language network prior to epilepsy surgery.

Clinical practice of language fMRI in epilepsy centers: a European survey and conclusions by the ESNR Epilepsy Working Group

Purpose

To assess current clinical practices throughout Europe with respect to acquisition, implementation, evaluation, and interpretation of language functional MRI (fMRI) in epilepsy patients.

Methods

An online survey was emailed to all European Society of Neuroradiology members (n = 1662), known associates (n = 6400), and 64 members of European Epilepsy network. The questionnaire featured 40 individual items on demographic data, clinical practice and indications, fMRI paradigms, radiological workflow, data post-processing protocol, and reporting.

Results

A total of 49 non-duplicate entries from European centers were received from 20 countries. Of these, 73.5% were board-certified neuroradiologists and 69.4% had an in-house epilepsy surgery program. Seventy-one percent of centers performed fewer than five scans per month for epilepsy. The most frequently used paradigms were phonemic verbal fluency (47.7%) and auditory comprehension (55.6%), but variants of 13 paradigms were described. Most centers assessed the fMRI task performance (75.5%), ensured cognitive-task adjustment (77.6%), trained the patient before scanning (85.7%), and assessed handedness (77.6%), but only 28.6% had special paradigms for patients with cognitive impairments. fMRI was post-processed mainly by neuroradiologists (42.1%), using open-source software (55.0%). Reporting was done primarily by neuroradiologists (74.2%). Interpretation was done mainly by visual inspection (65.3%). Most specialists (81.6%) were able to determine the hemisphere dominance for language in more than 75% of exams, attributing failure to the patient not performing the task correctly.

Conclusion

This survey shows that language fMRI is firmly embedded in the preoperative management of epilepsy patients. The wide variety of paradigms and the use of non-CE-marked software underline the need for establishing reference standards.

Electronic supplementary material

The online version of this article (10.1007/s00234-020-02397-w) contains supplementary material, which is available to authorized users.

A Functional Magnetic Resonance Imaging Approach for Language Laterality Assessment in Young Children

Functional magnetic resonance imaging (fMRI) is a usable technique to determine hemispheric dominance of language function, but high-quality fMRI images are difficult to acquire in young children. Here we aimed to develop and validate an fMRI approach to reliably determine hemispheric language dominance in young children. We designed two new tasks (story, SR; Letter picture matching, LPM) that aimed to match the interests and the levels of cognitive development of young children. We studied 32 healthy children (6-10 years old, median age 8.7 years) and seven children with epilepsy (7-11 years old, median age 8.6 years) and compared the lateralization index of the new tasks with those of a well-validated task (verb generation, VG) and with clinical measures of hemispheric language dominance. A conclusive assessment of hemispheric dominance (lateralization index ≤-0.2 or ≥0.2) was obtained for 94% of the healthy participants who performed both new tasks. At least one new task provided conclusive language laterality assessment in six out of seven participants with epilepsy. The new tasks may contribute to assessing language laterality in young and preliterate children and may benefit children who are scheduled for surgical treatment of disorders such as epilepsy.

Epilepsy and Bilingualism. A Systematic Review

Background: In patients with epilepsy, language abilities and neural language organization have been primarily investigated for the patient's mother tongue. However, in clinical practice, many patients use more than one language or use their second language more than their mother tongue. Yet, information about the linguistic profiles and brain organization of both languages in bilingual epilepsy patients is scarce. The purpose of this study was thus to systematically review the literature on language localization and language abilities in bilingual patients with epilepsy. Methods: An extensive literature search was performed using various electronic databases, including Embase and Medline. Key aspects of inclusion criteria were the assessment of language abilities and/or the investigation of neural language mapping in bilingual patients with epilepsy. Results: Our search strategy yielded 155 articles on language in bilingual epilepsy patients. Of these, 12 met final eligibility criteria. The majority of included articles focused on brain mapping of language using fMRI, Wada-test, or electrocortical stimulation in bilingual epilepsy patients, five studies investigated interictal language abilities in this patient group. Study results showed a pronounced heterogeneity of language abilities in bilingual patients, varying from intact language profiles to impairment in several language functions in both languages. However, the mother tongue was most often better perserved than the second language. Furthermore, studies on brain mapping of both languages again revealed heterogeneous findings ranging from identical brain regions for both languages to overlapping, but more distributed cortical areas for the non-native language. Conclusions: This review underlines the need to evaluate linguistic abilities in both languages, as well as the necessity to preoperatively map both languages in bilingual epilepsy patients. In contrast to the large scientific interest in language abilities and language localization in monolingual epilepsy patients, this review shows that in bilingual patients, the examination of language functions and the identification of brain regions associated with both languages so far played a minor role in epilepsy research. Our review thus emphasizes the need of future research activities in this field.

Cortical stimulation mapping for localization of visual and auditory language in pediatric epilepsy patients

OBJECTIVE

To determine resection margins near eloquent tissue, electrical cortical stimulation (ECS) mapping is often used with visual naming tasks. In recent years, auditory naming tasks have been found to provide a more comprehensive map. Differences in modality-specific language sites have been found in adult patients, but there is a paucity of research on ECS language studies in pediatric patients. The goals of this study were to evaluate word-finding distinctions between visual and auditory modalities and identify which cortical subregions most often contain critical language function in a pediatric population.

METHODS

Twenty-one pediatric patients with epilepsy or temporal lobe pathology underwent ECS mapping using visual (n = 21) and auditory (n = 14) tasks. Fisher's exact test was used to determine whether the frequency of errors in the stimulated trials was greater than the patient's baseline error rate for each tested modality and subregion.

RESULTS

While the medial superior temporal gyrus was a common language site for both visual and auditory language (43.8% and 46.2% of patients, respectively), other subregions showed significant differences between modalities, and there was significant variability between patients. Visual language was more likely to be located in the anterior temporal lobe than was auditory language. The pediatric patients exhibited fewer parietal language sites and a larger range of sites overall than did adult patients in previously published studies.

CONCLUSIONS

There was no single area critical for language in more than 50% of patients tested in either modality for which more than 1 patient was tested (n > 1), affirming that language function is plastic in the setting of dominant-hemisphere pathology. The high rates of language function throughout the left frontal, temporal, and anterior parietal regions with few areas of overlap between modalities suggest that ECS mapping with both visual and auditory testing is necessary to obtain a comprehensive language map prior to epileptic focus or tumor resection.

Structured testing during seizures: A practical guide for assessing and interpreting ictal and postictal signs during video EEG long term monitoring

BACKGROUND

Ictal and postictal testing carried out in long-term epilepsy monitoring units is often sub-optimal. Recently, a European consensus protocol for testing patients during and after seizures was developed by a joint taskforce of the International League Against Epilepsy - Commission on European Affairs and the European Epilepsy Monitoring Unit Association.

AIM

Using this recently developed standardised assessment battery as a framework, the goal of this narrative review is to outline the proposed testing procedure in detail and explain the rationale for each individual component, focusing on the underlying neurobiology. This is intended to serve as an educational resource for staff working in epilepsy monitoring units.

METHODS

A literature review of PubMed was performed; using the search terms "seizure", "ictal", "postictal", "testing", "examination", and "interview". Relevant literature was reviewed and relevant references were chosen. The work is presented as a narrative review.

RESULTS

The proposed standardised assessment battery provides a comprehensive and user-friendly format for ictal-postictal testing, and examines consciousness, language, motor, sensory, and visual function.

CONCLUSION

The standardised approach proposed has the potential to make full use of data recorded during video EEG increasing the diagnostic yield with regards to lateralisation and localisation, aiding both presurgical and diagnostic studies.

Direct electrophysiological mapping of human pitch-related processing in auditory cortex

This work sought correlates of pitch perception, defined by neural activity above the lower limit of pitch (LLP), in auditory cortical neural ensembles, and examined their topographical distribution. Local field potentials (LFPs) were recorded in eight patients undergoing invasive recordings for pharmaco-resistant epilepsy. Stimuli consisted of bursts of broadband noise followed by regular interval noise (RIN). RIN was presented at rates below and above the LLP to distinguish responses related to the regularity of the stimulus and the presence of pitch itself. LFPs were recorded from human cortical homologues of auditory core, belt, and parabelt regions using multicontact depth electrodes implanted in Heschl's gyrus (HG) and Planum Temporale (PT), and subdural grid electrodes implanted over lateral superior temporal gyrus (STG). Evoked responses corresponding to the temporal regularity of the stimulus were assessed using autocorrelation of the evoked responses, and occurred for stimuli below and above the LLP. Induced responses throughout the high gamma range (60-200 Hz) were present for pitch values above the LLP, with onset latencies of approximately 70 ms. Mapping of the induced responses onto a common brain space demonstrated variability in the topographical distribution of high gamma responses across subjects. Induced responses were present throughout the length of HG and on PT, which is consistent with previous functional neuroimaging studies. Moreover, in each subject, a region within lateral STG showed robust induced responses at pitch-evoking stimulus rates. This work suggests a distributed representation of pitch processing in neural ensembles in human homologues of core and non-core auditory cortex.

Neuroimaging correlates of language network impairment and reorganization in temporal lobe epilepsy

Advanced, noninvasive imaging has revolutionized our understanding of language networks in the brain and is reshaping our approach to the presurgical evaluation of patients with epilepsy. Functional magnetic resonance imaging (fMRI) has had the greatest impact, unveiling the complexity of language organization and reorganization in patients with epilepsy both pre- and postoperatively, while volumetric MRI and diffusion tensor imaging have led to a greater appreciation of structural and microstructural correlates of language dysfunction in different epilepsy syndromes. In this article, we review recent literature describing how unimodal and multimodal imaging has advanced our knowledge of language networks and their plasticity in epilepsy, with a focus on the most frequently studied epilepsy syndrome in adults, temporal lobe epilepsy (TLE). We also describe how new analytic techniques (i.e., graph theory) are leading to a refined characterization of abnormal brain connectivity, and how subject-specific imaging profiles combined with clinical data may enhance the prediction of both seizure and language outcomes following surgical interventions.

Re-examining the crowding hypothesis in pediatric epilepsy

OBJECTIVE

In adults with left-sided epilepsy, reorganized language may "crowd out" right-hemisphere visual-spatial skills, with relative sparing of language (i.e., the crowding hypothesis). However, this effect has not consistently been demonstrated in pediatric epilepsy studies. The objective of this study was to investigate the crowding hypothesis using a heterogeneous sample of children with intractable epilepsy and typical (left) language dominance or atypical (right or bilateral) language dominance. We examined the relative contributions of seizure onset (before or after age 5), handedness (right versus left), seizure localization (temporal versus extratemporal), as well as language dominance on verbal versus visual cognitive skills.

METHOD

We retrospectively analyzed neuropsychology assessment results from a sample of 91 children who completed presurgical evaluation at the Hospital for Sick Children in Toronto, Canada (34 with typical language, 57 with atypical language, mean age = 12 years). We considered a selection of verbal skills (naming, vocabulary knowledge, verbal abstract reasoning) and visual skills (visual-motor integration, block construction, visual abstract reasoning).

RESULTS

Consistent with several previous adult studies supporting the crowding hypothesis, univariate analyses showed that the typical and atypical language groups were comparable on the measures of vocabulary knowledge and abstract verbal reasoning whereas the atypical language group produced lower scores across visual measures. Multivariate analyses (taking into account language dominance and associated factors) showed that language dominance was the strongest predictor of performance on two of three visual measures whereas language dominance was not a significant predictor of performance on most verbal measures. Unexpectedly, both sets of analyses indicated that the atypical language group had poorer naming abilities than the typical language group.

SIGNIFICANCE

Our data provide some evidence of right-hemisphere functional crowding effects in a heterogeneous sample of children with intractable left-sided epilepsy. Specifically, those with atypical versus typical language dominance showed poorer visual-motor integration and visual-motor problem-solving skills, with comparable scores on certain verbal measures. It is critical that potential crowding effects be considered when interpreting the neuropsychological profiles of children being evaluated for epilepsy surgery.

MEG Assessment of Expressive Language in Children Evaluated for Epilepsy Surgery

Establishing language dominance is an important step in the presurgical evaluation of patients with refractory epilepsy. In the absence of a universally accepted gold-standard non-invasive method to determine language dominance in the preoperative assessment, a range of tools and methodologies have recently received attention. When applied to pediatric age, many of the proposed methods, such as functional magnetic resonance imaging (fMRI), may present some challenges due to the time-varying effects of epileptogenic lesions and of on-going seizures on maturational phenomena. Magnetoencephalography (MEG) has the advantage of being insensitive to the distortive effects of anatomical lesions on brain microvasculature and to differences in the metabolism or vascularization of the developing brain and also provides a less intimidating recording environment for younger children. In this study we investigated the reliability of lateralized synchronous cortical activation during a verb generation task in a group of 28 children (10 males and 18 females, mean age 12 years) with refractory epilepsy who were evaluated for epilepsy surgery. The verb generation task was associated with significant decreases in beta oscillatory power (13–30 Hz) in frontal and temporal lobes. The MEG data were compared with other available presurgical non-invasive data including cortical stimulation, neuropsychological and fMRI data on language lateralization where available. We found that the lateralization of MEG beta power reduction was concordant with language dominance determined by one or more different assessment methods (i.e. cortical stimulation mapping, neuropsychological, fMRI or post-operative data) in 89% of patients. Our data suggest that qualitative hemispheric differences in task-related changes of spectral power could offer a promising insight into the contribution of dominant and non-dominant hemispheres in language processing and may help to characterize the specialization and lateralization of language processes in children.

Knowledge of language function and underlying neural networks gained from focal seizures and epilepsy surgery

The effects of epilepsy and its treatments have contributed significantly to language models. The setting of epilepsy surgery, which allows for careful pre- and postsurgical evaluation of patients with cognitive testing and neuroimaging, has produced a wealth of language findings. Moreover, a new wave of surgical interventions, including stereotactic laser ablation and radio frequency ablation, have contributed new insights and corrections to language models as they can make extremely precise, focal lesions. This review covers the common language deficits observed in focal dyscognitive seizure syndromes. It also addresses the effects of surgical interventions on language, and highlights insights gained from unique epilepsy assessment methods (e.g., cortical stimulation mapping, Wada evaluation). Emergent findings are covered including a lack of involvement of the hippocampus in confrontation word retrieval, possible roles for key white matter tracts in language, and the often-overlooked basal temporal language area. The relationship between language and semantic memory networks is also explored, with brief consideration given to the prevailing models of semantic processing, including the amodal Hub and distributed, multi-modal processing models.

Benign rolandic epilepsy of childhood and central auditory processing disorder: A noncasual neurophysiological association

PURPOSE

The purpose of this study was to demonstrate the association between benign rolandic epilepsy of childhood (BREC) and central auditory processing disorders (CAPDs) and to test the hypothesis that an early onset of BREC could be associated with more cases of CAPD.

METHOD

This study has a retrospective cross-sectional design conducted from January 2006 to January 2016 including 93 patients with BREC and without intellectual disability, dyslexia, and attention-deficit hyperactivity disorders. All patients were evaluated for central auditory processing (CAP), and its presence or absence was compared with age of seizure onset.

RESULTS

In all patients, audiometric test results were normal, and in 43 cases (46.2%), CAPD was detected. There was no significant statistical difference in the mean age of seizure onset.

CONCLUSION

A significant proportion of children with BREC will have a diagnosis of CAPD at school age.

Typical asymmetry in the hemispheric activation during an fMRI verbal comprehension paradigm is related to better performance in verbal and non-verbal tasks in patients with epilepsy

Chronic exposure to seizures in patients with left hemisphere (LH) epileptic focus could favor higher activation in the contralateral hemisphere during language processing, but the cognitive effects of this remain unclear. This study assesses the relationship between asymmetry in hemispheric activation during language fMRI and performance in verbal and non-verbal tasks. Whereas prior studies primarily used fMRI paradigms that favor frontal lobe activation and less prominent activation of the medial or superior temporal lobes, we used a verbal comprehension paradigm previously demonstrated to activate reliably receptive language areas. Forty-seven patients with drug-resistant epilepsy candidates for surgery underwent a multidisciplinary assessment, including a comprehensive neuropsychological evaluation and an fMRI verbal comprehension paradigm. Patients were distributed in two groups depending on laterality indexes (LI): typical hemispheric asymmetry (unilateral left activation preponderance; n = 23) and atypical hemispheric asymmetry (bilateral or unilateral right preponderance; n = 24). Right-handedness and right hemisphere (RH) focus were significant predictors of typical asymmetry. Patients with typical activation pattern presented better performance intelligence quotient and verbal learning than patients with atypical hemispheric asymmetry (for all, p < 0.014). Patients with LH focus had more frequently atypical hemispheric asymmetry than patients with RH focus (p = 0.05). Specifically, they showed lower LI and this was related to worse performance in verbal and non-verbal tasks. In conclusion, an increased activation of homologous RH areas for verbal comprehension processing could imply a competition of cognitive resources in the performance of the same task, disrupting cognitive performance.

A simple magnetoencephalographic auditory paradigm may aid in confirming left-hemispheric language dominance in epilepsy patients

OBJECTIVE

The intracarotid amobarbital procedure (IAP) is the current "gold standard" in the preoperative assessment of language lateralization in epilepsy surgery candidates. It is, however, invasive and has several limitations. Here we tested a simple noninvasive language lateralization test performed with magnetoencephalography (MEG).

METHODS

We recorded auditory MEG responses to pairs of vowels and pure tones in 16 epilepsy surgery candidates who had undergone IAP. For each individual, we selected the pair of planar gradiometer sensors with the strongest N100m response to vowels in each hemisphere and-from the vector sum of signals of this gradiometer pair-calculated the vowel/tone amplitude ratio in the left (L) and right (R) hemisphere and, subsequently, the laterality index: LI = (L-R)/(L+R). In addition to the analysis using a single sensor pair, an alternative analysis was performed using averaged responses over 18 temporal sensor pairs in both hemispheres.

RESULTS

The laterality index did not correlate significantly with the lateralization data obtained from the IAP. However, an MEG pattern of stronger responses to vowels than tones in the left hemisphere and stronger responses to tones than vowels in the right hemisphere was associated with left-hemispheric language dominance in the IAP in all the six patients who showed this pattern. This results in a specificity of 100% and a sensitivity of 67% of this MEG pattern in predicting left-hemispheric language dominance (p = 0.01, Fisher's exact test). In the analysis using averaged responses over temporal channels, one additional patient who was left-dominant in IAP showed this particular MEG pattern, increasing the sensitivity to 78% (p = 0.003).

SIGNIFICANCE

This simple MEG paradigm shows promise in feasibly and noninvasively confirming left-hemispheric language dominance in epilepsy surgery candidates. It may aid in reducing the need for the IAP, if the results are confirmed in larger patient samples.

The focal alteration and causal connectivity in children with new-onset benign epilepsy with centrotemporal spikes

The aim of the current study was to find the epileptic focus and examine its causal relationship to other brain regions in children with new-onset benign childhood epilepsy with centrotemporal spikes (BECTS). Resting-state functional magnetic resonance imaging (fMRI) was performed in 66 children with BECTS and 37 matched control children. We compared the amplitude of low frequency fluctuation (ALFF) signals between the two groups to find the potential epileptogenic zone (EZ), then used Granger causality analysis (GCA) to explore the causal effects of EZ on the whole brain. Children with BECTS had significantly increased ALFF in the right Broca’s area, and decreased ALFF in bilateral fusiform gyrus. The patients also showed increased driving effect from the EZ in Broca’s area to the right prefrontal lobe, and decreased effects to the frontal lobe and posterior parts of the language network. The causal effect on left Wernicke’s area negatively correlated with verbal IQ (VIQ) score. Our research on new-onset BECTS patients illustrates a possible compensatory mechanism in the language network at early stages of BECTS, and the negative correlation of GCA and VIQ suggest the disturbance of epileptiform activity on language. These findings shed light on the mechanisms of and language dysfunction in BECTS.