Real-time effects of centrotemporal spikes on cognition in rolandic epilepsy

Role of Language-Related Functional Connectivity in Patients with Benign Childhood Epilepsy with Centrotemporal Spikes

Background and Purpose

Benign childhood epilepsy with centrotemporal spikes (BECTS) does not always have a benign cognitive outcome. We investigated the relationship between cognitive performance and altered functional connectivity (FC) in the resting-state brain networks of BECTS patients.

Methods

We studied 42 subjects, comprising 19 BECTS patients and 23 healthy controls. Cognitive performance was assessed using the Korean version of the Wechsler Intelligence Scale for Children-III, in addition to verbal and visuospatial memory tests and executive function tests. Resting-state functional magnetic resonance imaging was acquired in addition to high-resolution structural data. We selected Rolandic and language-related areas as regions of interest (ROIs) and analyzed the seed-based FC to voxels throughout the brain. We evaluated the correlations between the neuropsychological test scores and seed-based FC values using the same ROIs.

Results

The verbal intelligence quotient (VIQ) and full-scale intelligence quotient (FSIQ) were lower in BECTS patients than in healthy controls (p<0.001). The prevalence of subjects with a higher performance IQ than VIQ was significantly higher in BECTS patients than in healthy controls (73.7% vs. 26.1%, respectively; p=0.002). Both the Rolandic and language-related ROIs exhibited more enhanced FC to voxels in the left inferior temporal gyrus in BECTS patients than in healthy controls. A particularly interestingly finding was that the enhanced FC was correlated with lower cognitive performance as measured by the VIQ and the FSIQ in both patients and control subjects.

Conclusions

Our findings suggest that the FC alterations in resting-state brain networks related to the seizure onset zone and language processing areas could be related to adaptive plasticity for coping with cognitive dysfunction.

Differential patterns of dynamic functional connectivity variability of striato-cortical circuitry in children with benign epilepsy with centrotemporal spikes

Benign epilepsy with centrotemporal spikes (BECTS) is characterized by abnormal (static) functional interactions among cortical and subcortical regions, regardless of the active or chronic epileptic state. However, human brain connectivity is dynamic and associated with ongoing rhythmic activity. The dynamic functional connectivity (dFC) of the distinct striato-cortical circuitry associated with or without interictal epileptiform discharges (IEDs) are poorly understood in BECTS. Herein, we captured the pattern of dFC using sliding window correlation of putamen subregions in the BECTS (without IEDs, n = 23; with IEDs, n = 20) and sex- and age-matched healthy controls (HCs, n = 28) during rest. Furthermore, we quantified dFC variability using their standard deviation. Compared with HCs and patients without IEDs, patients with IEDs exhibited excessive variability in the dorsal striatal-sensorimotor circuitry related to typical seizure semiology. By contrast, excessive stability (decreased dFC variability) was found in the ventral striatal-cognitive circuitry (p < .05, GRF corrected). In addition, correlation analysis revealed that the excessive variability in the dorsal striatal-sensorimotor circuitry was related to highly frequent IEDs (p < .05, uncorrected). Our finding of excessive variability in the dorsal striatal-sensorimotor circuitry could be an indication of increased sensitivity to regional fluctuations in the epileptogenic zone, while excessive stability in the ventral striatal-cognitive circuitry could represent compensatory mechanisms that prevent or postpone cognitive impairments in BECTS. Overall, the differentiated dynamics of the striato-cortical circuitry extend our understanding of interactions among epileptic activity, striato-cortical functional architecture, and neurocognitive processes in BECTS.

"Atypical forms" of benign epilepsy with centrotemporal spikes (BECTS): How to diagnose and guide these children. A practical/scientific approach

Benign epilepsy with centrotemporal spikes (BECTS) epilepsy, also known as rolandic epilepsy, is the most common childhood type of epilepsy. There is debate on its "benign" definition given the numerous literature data on its correlation to cognitive morbidity. Although its prognosis is often favorable, BECTS can present or evolve however to an atypical form, characterized by a worse prognosis and negative impact on cognitive development. It is possible that abnormal electrical activity, marker of neurological dysfunction, has the potential to disrupt neural network function and development. Numerous studies tried to identify clinical or electroencephalographic criteria for atypical forms and atypical evolution of BECTS in order to guide follow-up and treatment of patients and to predict their outcome. This review provides a compact summery of literature data with a focus on predictive features of future cognitive decline.

Postoperative seizure freedom does not normalize altered connectivity in temporal lobe epilepsy

OBJECTIVES

Specific changes in the functional connectivity of brain networks occur in patients with epilepsy. Yet whether such changes reflect a stable disease effect or one that is a function of active seizure burden remains unclear. Here, we longitudinally assessed the connectivity of canonical cognitive functional networks in patients with intractable temporal lobe epilepsy (TLE), both before and after patients underwent epilepsy surgery and achieved seizure freedom.

METHODS

Seventeen patients with intractable TLE who underwent epilepsy surgery with Engel class I outcome and 17 matched healthy controls took part in the study. The functional connectivity of a set of cognitive functional networks derived from typical cognitive tasks was assessed in patients, preoperatively and postoperatively, as well as in controls, using stringent methods of artifact reduction.

RESULTS

Preoperatively, functional networks in TLE patients differed significantly from healthy controls, with differences that largely, but not exclusively, involved the default mode and temporal/auditory subnetworks. However, undergoing epilepsy surgery and achieving seizure freedom did not lead to significant changes in network connectivity, with postoperative functional network abnormalities closely mirroring the preoperative state.

SIGNIFICANCE

This result argues for a stable chronic effect of the disease on brain connectivity, with changes that are largely "burned in" by the time a patient with intractable TLE undergoes epilepsy surgery, which typically occurs years after the initial diagnosis. The result has potential implications for the treatment of intractable epilepsy, suggesting that delaying surgical intervention that may achieve seizure freedom may lead to functional network changes that are no longer reversible by the time of epilepsy surgery.

Altered language network in benign childhood epilepsy patients with spikes from non-dominant side: A resting-state fMRI study

Benign childhood epilepsy with centrotemporal spikes (BECTS) is one of the most common childhood epilepsy syndromes, and language deficits associated with BECTS have become a hot topic. This study investigated alterations of the language network in BECTS children with spikes from the non-dominant side in comparison with healthy controls. Twenty-three children with BECTS and 20 age-matched healthy controls were enrolled. Region of interest -based whole brain functional connectivity analysis was used to identify the potential differences in the functional connectivity of the Broca's area between the two groups. Increased positive functional connectivity within the Broca's region was detected mainly at the left superior frontal gyrus (Brodmann area 8), bilateral insula, and anterior and posterior cingulate in the BECTS group. No regions showed significantly decreased connection in the BECTS patients compared to the controls. This study suggested alterations in the language network that was related with the Broca's area in children with BECTS from the non-dominant side. Further studies with longitudinal assessments from the perceptive of functional neuroimaging are needed to illustrate the dynamic course of language development and corresponding neuroimaging evidence.

The executive profile of children with Benign Epilepsy of Childhood with Centrotemporal Spikes and Temporal Lobe Epilepsy

RATIONALE

Benign Epilepsy of Childhood with Centrotemporal Spikes (BECTS) and temporal lobe epilepsy (TLE) represent two distinct models of focal epilepsy of childhood. In both, there is evidence of executive dysfunction. The purpose of the present study was to identify particular deficits in the executive function that would distinguish children with BECTS from children with TLE.

METHODS

We prospectively evaluated 19 consecutive children and adolescents with TLE with hippocampal sclerosis (HS) (57.9% male; mean 11.74years [SD 2.05]; mean IQ 95.21 [SD 15.09]), 19 with BECTS (36.8% male; mean 10.95years [SD 2.33]; mean IQ 107.40 [SD 16.01]), and 21 age and gender-matched controls (33.3% male; mean 11.86years [SD 2.25]; mean IQ 108.67 [15.05]). All participants underwent a neuropsychological assessment with a comprehensive battery for executive and attentional functions. We used ANOVA and chi-square to evaluate differences on demographic aspects among groups (BECTS, TLE-HS, and control groups). Group comparisons on continuous variables were complemented by MANOVA and Bonferroni posthoc comparisons.

RESULTS

Patients with BECTS had worse performance than controls in: Matching Familiar Figures Test, time (p=0.001); Matching Familiar Figures Test, time×errors index (p<0.001); Verbal Fluency for foods (p=0.038); Trail Making Test, part B time (p=0.030); Trail Making Test, part B number of errors (p=0.030); and WCST, number of categories achieved (p=0.043). Patients with BECTS had worse performance than patients with TLE-HS on Matching Familiar Figures Test, time (p=0.004), and Matching Familiar Figures Test, time×errors index (p<0.001). Patients with TLE-HS had worse performance than controls on the following tests: Verbal Fluency for foods (p=0.004); Wisconsin Card Sorting Test, the number of categories achieved (p<0.001); and Wisconsin Card Sorting Test, the number of perseverative errors (p=0.028). Patients with TLE-HS had worse performance than patients with BECTS on Digit Backward (p=0.002); and the Wisconsin Card Sorting Test, the number of perseverative errors (p<0.001).

CONCLUSIONS

Patients with TLE and BECTS present distinct cognitive profiles. Patients with TLE-HS had worse performance in mental flexibility, concept formation, and working memory compared to BECTS. Patients with BECTS had worse inhibitory control compared to children with TLE-HS. Both TLE-HS and BECTS had a higher number of errors on an inhibitory control test. However, patients with BECTS had a slower mental processing even when compared to patients with TLE-HS. Rehabilitation programs for children with epilepsy must include children with benign epilepsies and must take into account the epileptic syndrome and its particular neurocognitive phenotype.

Working memory and phonological awareness in children with rolandic epilepsy

This study investigated how the difficulties in language in children with Rolandic Epilepsy (RE) could be related to alterations in their development of phonological awareness and/or working memory. We evaluated fourty-two children aged 6 to 13 years old. From these, twenty-one children were diagnosed with RE and formed the experimental group; and twenty-one children without RE, paired with the experimental group by sex, age, education and socioeconomic status, formed the control group. The results showed significant differences in the performances of children with RE and healthy children in the tests that evaluated working memory and phonological awareness. Also, positive and high significant correlations were found between working memory and phonological awareness in the RE clinical subgroup. Generally, the results suggest that compromises in both cognitive functions might be associated to loss of language capabilities in children with RE, and also point that the development of working memory and phonological awareness are interconnected.

Local and Distant Dysregulation of Synchronization Around Interictal Spikes in BECTS

Objective: High Density electroencephalography (HD EEG) is the reference non-invasive technique to investigate the dynamics of neuronal networks in Benign Epilepsy with Centro-Temporal Spikes (BECTS). Analysis of local dynamic changes surrounding Interictal Epileptic Spikes (IES) might improve our knowledge of the mechanisms that propel neurons to the hypersynchronization of IES in BECTS. Transient distant changes in the dynamics of neurons populations may also interact with neuronal networks involved in various functions that are impaired in BECTS patients.

Methods: HD EEG (64 electrodes) of eight well-characterized BECTS patients (8 males; mean age: 7.2 years, range: 5–9 years) were analyzed. Unilateral IES were selected in 6 patients. They were bilateral and independent in 2 other patients. This resulted in a total of 10 groups of IES. Time-frequency analysis was performed on HD EEG epochs around the peak of the IES (±1000 ms), including phase-locked and non-phase-locked activities to the IES. The time frequency analyses were calculated for the frequencies between 4 and 200 Hz.

Results: Time-frequency analysis revealed two patterns of dysregulation of the synchronization between neuronal networks preceding and following hypersynchronization of interictal spikes (±400 ms) in the epileptogenic zone. Dysregulation consists of either desynchronization (n = 6) or oscillating synchronization (n = 4) (4–50 Hz) surrounding the IES. The 2 patients with bilateral IES exhibited only local desynchronization whatever the IES considered. Distant desynchronization in low frequencies within the same window occurs simultaneously in bilateral frontal, temporal and occipital areas (n = 7).

Significance: Using time-frequency analysis of HD EEG data in a well-defined population of BECTS, we demonstrated repeated complex changes in the dynamics of neuronal networks not only during, but also, before and after the IES. In the epileptogenic zone, our results found more complex reorganization of the local network than initially thought. In line with previous results obtained at a microscopic or macroscopic level, these changes suggested the variability strategies of neuronal assemblies to raise IES. Distant changes from the epileptogenic zone in desynchronization observed in the same time window suggested interactions between larger embedded networks and opened new avenues about their possible role in the underlying mechanism leading to cognitive deficits.

Prevalence of epileptiform discharges in healthy 11- and 12-year-old children

We sought to determine the prevalence of interictal epileptiform discharges (IEDs) in healthy 11- and 12-year-old children. Sixth grade students with no history of seizure, or neurologic or psychiatric disease, were enrolled in a longitudinal physical activity intervention study. Per study protocol, each student had two EEG recordings approximately 6months apart. Epileptiform discharges were present in 4 (2.9%) of 140 students: centrotemporal in three and generalized in one. In three children, the discharges were still present six months later. None of the children had developed seizures a minimum of one year after the second EEG. These results are consistent with those of two landmark European studies performed nearly a half century ago, before the modern era of digital EEG. Healthy 11- and 12-year-old children with no history of seizure may have centrotemporal or generalized epileptiform discharges on EEG, which can persist for at least 6months. Based on both our results and those of the two prior European studies, such discharges, if found incidentally in otherwise healthy children in this age group, should not prompt further evaluation or treatment.