Speech and language deterioration in benign rolandic epilepsy

Interictal Spikes as an EEG Biomarker of Cognitive Impairment

SUMMARY

Although interictal spikes (IISs) are a well-established EEG biomarker for epilepsy, whether they are also a biomarker of cognitive deficits is unclear. Interictal spikes are dynamic events consisting of a synchronous discharge of neurons producing high frequency oscillations and a succession of action potentials which disrupt the ongoing neural activity. There are robust data showing that IISs result in transitory cognitive impairment with the type of deficit specific to the cognitive task and anatomic location of the IIS. Interictal spike, particularly if frequent and widespread, can impair cognitive abilities, through interference with waking learning and memory and memory consolidation during sleep. Interictal spikes seem to be particularly concerning in the developing brain where animal data suggest that IISs can lead to adverse cognitive effects even after the disappearance of the spikes. Whether a similar phenomenon occurs in human beings is unclear. Thus, although IISs are a clear biomarker of transitory cognitive impairment, currently, they lack sensitivity and specificity as a biomarker for enduring cognitive impairment.

Hypnagogic Frontal EEG Bursts in Children: Epileptic or Not?

PURPOSE

Various EEG patterns emerge in drowsiness. Intermittent bilateral midfrontal slowing (BFS) and hypnogogic frontal predominant sharply contoured waveforms (HFSC), maximal at (Fz, F3-4, and Fp1-2), are often encountered. These do not meet the criteria for epileptiform discharges. The study objective was to determine the clinical significance of BFS and HFSC.

METHODS

Clinical information of children with BFS (n = 49) and HFSC (n = 99) was compared with control subjects with generalized spike-wave (GSW) discharges (n = 102) and normal EEGs (n = 100).

RESULTS

HFSC was present in younger children (mean age was 3.5 ± 3.6 years), whereas BFS was present in older children (mean 12.9 ± 4.8 years). Seizures occurred in the normal EEG, BFS, HFSC, and GSW groups, respectively, as follows: 22 (22%), 15 (31%), 42 (43%), and 100 (98%) patients, whereas epilepsy occurred in 17 (17%), 10 (20%), 35 (35%), and 95 (93%) patients. The GSW group had more seizures and epilepsy than the other groups (P < 0.001), but the HFSC group also had more seizures (P < 0.001) and epilepsy (P < 0.003) than the normal EEG group. Seizures and neurodevelopmental and psychiatric comorbidities were similar between the BFS and normal EEG groups. Notably, the HFSC group had more developmental delay than the normal EEG group [33 (33%) versus 18 (18%), P < 0.009] but were similar to the GSW group 22 (22%).

CONCLUSIONS

Bilateral midfrontal slowing and HFSC have had unclear significance. Our results suggest that HFSC may be a marker of increased risk of seizure, epilepsy, and developmental delay as compared to children with normal EEGs and has similar risk of developmental delay to those with GSW.

Concurrent EEG monitoring helps interpret neuropsychological testing results in patients with epilepsy

OBJECTIVE

We sought to determine if global cognitive function in patients with epilepsy (PWE) differs when electroencephalographic (EEG) abnormalities are present during concurrent neuropsychological (NP) evaluation.

METHODS

We explored the association between subclinical epileptiform discharges (sEDs) and interictal epileptiform discharges (IEDs) and global aspects of cognition in 79 consecutive PWE who underwent continuous EEG monitoring during NP evaluation for diagnostic (15%) or presurgical (85%) purposes while on their standard antiseizure medication (ASM) regimens. As some researchers have suggested that the apparent link between IEDs and cognition represent epiphenomena of an underlying damaged neural substrate, we used functional status as a stratifying covariate to allow us to address this position.

RESULTS

Despite being on their standard ASM regimen, EEG was abnormal in 68% of patients. Epileptiform abnormalities (IEDs, sEDs, or both) were seen in isolation or coupled with diffuse or focal slowing in 38% of patients. Individuals with IEDs occurring during their NP evaluation demonstrated poorer scores in attention/working memory (forward and backward digit span), processing speed (symbol searching and coding), and speeded components of language (semantic fluency) tests compared with those with normal EEG tracings matched by their real-world, functional status. In two high functioning patients, performance was significantly better when these individuals were tested in the absence of IEDs, with performances appearing invalid when tested during periods of IED activity. No significant association was found between NP performance and nonepileptiform EEG abnormalities.

SIGNIFICANCE

A substantial proportion of PWE undergoing NP evaluation manifest concurrent EEG abnormalities, with epileptiform abnormalities associated with poorer global cognitive performance. As this pattern was observed regardless of functional status, this association appears to represent more than unrelated features coincidentally shared by the lowest functioning cohort. Coupled with our individual case data, our findings suggest that NP testing may be adversely affected by IEDs and sEDs going unrecognized in the absence of simultaneous EEG recordings, and set the stage for future studies to definitively establish this possible relationship.

Functional and Structural Network Disorganizations in Typical Epilepsy With Centro-Temporal Spikes and Impact on Cognitive Neurodevelopment

Epilepsy with Centrotemporal Spikes (ECTS) is the most common form of self-limited focal epilepsy. The pathophysiological mechanisms by which ECTS induces neuropsychological impairment in 15-30% of affected children remain unclear. The objective of this study is to review the current state of knowledge concerning the brain structural and functional changes that may be involved in cognitive dysfunctions in ECTS. Structural brain imaging suggests the presence of subtle neurodevelopmental changes over the epileptogenic zone and over distant regions in ECTS. This structural remodeling likely occurs prior to the diagnosis and evolves over time, especially in patients with cognitive impairment, suggesting that the epileptogenic processes might interfere with the dynamics of the brain development and/or the normal maturation processes. Functional brain imaging demonstrates profound disorganization accentuated by interictal epileptic spikes (IES) in the epileptogenic zone and in remote networks in ECTS. Over the epileptogenic zone, the literature demonstrates changes in term of neuronal activity and synchronization, which are effective several hundred milliseconds before the IES. In the same time window, functional changes are also observed in bilateral distant networks, notably in the frontal and temporal lobes. Effective connectivity demonstrates that the epileptogenic zone constitutes the key area at the origin of IES propagation toward distant cortical regions, including frontal areas. Altogether, structural and functional network disorganizations, in terms of: (i) power spectral values, (ii) functional and effective connectivity, are likely to participate in the cognitive impairment commonly reported in children with ECTS. These results suggest a central and causal role of network disorganizations related to IES in the neuropsychological impairment described in ECTS children.

Effects of Antiepileptic Drugs on Language Abilities in Benign Epilepsy of Childhood with Centrotemporal Spikes

Background and Purpose

This study is to assess the responsiveness of electroencephalography (EEG) abnormalities and their effects on language ability after initiating different types of antiepileptic therapy in children with newly diagnosed benign epilepsy of childhood with centrotemporal spikes (BECTS).

Methods

The records of patients newly diagnosed with BECTS (n=120; 69 males) were reviewed retrospectively. The patients were randomly treated with lamotrigine, oxcarbazepine, or topiramate monotherapy, and underwent at least two EEG and standardized language tests. Effects were compared using Pearson's chi-square tests and paired t-tests.

Results

The recurrence rates for seizures in the lamotrigine, topiramate, and oxcarbazepine groups were 19.4%, 21.7%, and 11.4%, respectively, while complete or partial recovery (as indicated by EEG) occurred in 32%, 39%, and 16% of the patients. Patients in the lamotrigine group showed significant improvements in all parameters assessed by the Test of Language Problem Solving Abilities, except for ‘determining cause.’ Patients in the oxcarbazepine group also showed improvements, except for ‘making inferences’ (p<0.05). Most linguistic index scores were worse in the topiramate group except for Mean Length of Utterance in Words. Patients in the lamotrigine and oxcarbazepine groups showed significant improvements in the receptive language test (p<0.05). EEG improvements were not related to language ability.

Conclusions

The improvements in language and problem-solving performance in children with BECTS were greater for lamotrigine and oxcarbazepine than for topiramate. However, EEG remission did not imply that language function would be improved after the treatments.

The Clinical Spectrum of Benign Epilepsy with Centro-Temporal Spikes: a Challenge in Categorization and Predictability

Benign epilepsy with centro-temporal spikes (BECTS) is the most common type of focal epilepsy in children; it is age-dependent and presumably genetic. Traditionally, children with BECTS have a very good prognosis, even without medical treatment, and are thought to show no neurological symptoms or cognitive deficits. However, many previous studies have shown that BECTS can present with various clinical and electroencephalographic characteristics that are commonly associated with neuropsychological deficits, including linguistic, cognitive, and behavioral impairment. The degree of the neuropsychological deficits appears to depend on the sleep cycle and the localization of epileptiform discharges. Furthermore, based on neurobiological studies, a complex interplay between the processes of brain maturation and the involvement of genes that confer susceptibility may contribute to a variety of different childhood epileptic syndromes with various neuropsychological deficits. Thus, BECTS, atypical benign focal epilepsy during childhood, status epilepticus of BECTS, Landau-Kleffner syndrome, and epileptic encephalopathy with continuous spike-and-wave during sleep are all considered different entities, but are part of a single spectrum of disorders. In clinical practice, we have to consider BECTS as benign only when there are no or only mild neuropsychological deficits before medical treatment.

Neuropsychological assessment of children with rolandic epilepsy: executive functions

Rolandic epilepsy (RE) is the most common type of childhood focal epilepsy. Although there is no intellectual deficit, children with RE may have specific cognitive impairments. The aims of this study were to identify changes in executive functions in children with RE and to verify the influence of epilepsy and seizure variables. We evaluated 25 children with RE and 28 healthy controls. A comprehensive neuropsychological battery was utilized. The results showed that the RE children had worse performance than the control group in some categories of the Wisconsin Card Sorting Test, the Trail Making Test part B, and the Verbal Fluency Test (FAS). Children with earlier onset of epilepsy had worse performance when compared with children with later onset of epilepsy. We conclude that children with RE may show a deficit in executive function despite their normal IQ. The set of tests was more extensive than what was previously used in other studies. Our study suggests that early seizures can interfere with brain development. Regarding cognition, the term benign should be used cautiously in RE.

A mechanistic appraisal of cognitive dysfunction in epilepsy

A strong relationship between the clinical characteristics of epilepsy and the nature of cognitive impairments associated with the condition has been found, but the nature of this relationship appears to be quite complex and not well understood. This review presents a summary of the research on the interaction between cognition and epilepsy, surveyed from a mechanistic perspective with the aim of clarifying factors that contribute to the co-existence of both disorders. The physiological basis underpinning cognitive processing is first reviewed. The physiology of epilepsy is reviewed, with emphasis placed on interictal discharges and seizures. The nature of the impact of epilepsy on cognition is described, with transient and prolonged effects distinguished. Finally, the complexity of the co-morbidity between cognitive dysfunction and epilepsy is discussed in relation to childhood and adult-onset epilepsy syndromes and severe epileptic encephalopathies. Structural and functional abnormalities exist in patients with epilepsy that may underpin both the cognitive dysfunction and epilepsy, highlighting the complexity of the association. Research, possibly of a longitudinal nature, is needed to elucidate this multifactorial relationship between cognitive dysfunction and epilepsy.

Serial changes of prefrontal lobe growth in the patients with benign childhood epilepsy with centrotemporal spikes presenting with cognitive impairments/behavioral problems

Several studies have reported a higher incidence of learning and behavioral difficulties in association with frontal lobe dysfunctions in children with benign childhood epilepsy with centrotemporal spikes (BCECTS). We studied serial changes in frontal and prefrontal lobe volumes using three-dimensional magnetic resonance imaging in BCECTS with or without cognitive impairments and behavioral problems and evaluated correlations between prefrontal lobe growth and active seizure period. Serial changes in regional cerebral volumes were measured in two patients with cognitive impairments and behavioral problems (BCECTS(+)) and five patients without neuropsychiatric deficits (BCECTS(-)). Eleven normal subjects (4-13years old) served as controls. Volumes of the frontal and prefrontal lobes were determined using a workstation, and the prefrontal-to-frontal lobe volume ratio was calculated. Frontal and prefrontal lobe volumes revealed growth disturbance in BCECTS(+) compared with BCECTS(-) and control subjects. In addition, prefrontal-to-frontal lobe volume ratio increased serially in BCECTS(-) similarly to controls, but was stagnant or decreased in BCECTS(+). Prefrontal growth also revealed more rapid recovery in a BCECTS(+) patient with shorter active seizure period. These findings suggest that longer active seizure period as frequent spike-waves coupled with the occurrence of frequent seizures may be associated with prefrontal lobe growth disturbance, which relates to neuropsychological problems.

Benign rolandic epilepsy -- perhaps not so benign: use of magnetic source imaging as a predictor of outcome

The purpose of this study was to evaluate children with benign rolandic epilepsy, a childhood epilepsy characterized by centrotemporal/rolandic spike-wave discharges with infrequent partial seizures that may secondarily generalize. Recently, some investigators have questioned whether benign rolandic epilepsy is indeed "benign" or whether long-term cognitive outcome may be adversely affected. We initiated an ongoing study to identify children with benign rolandic epilepsy. The children were evaluated in the Texas Comprehensive Epilepsy Program using outpatient or continuous video-electroencephalographic monitoring, brain magnetic resonance imaging, magnetoencephalography, and neuropsychological testing. Neuropsychological testing revealed fine motor dysfunction, visuomotor integration deficits, dyscalculia, and/or expressive language deficits in all of the 9 patients evaluated, reaffirming that benign rolandic epilepsy is not necessarily a benign disorder. Our study shows a high concordance of motor and cognitive deficits in benign rolandic epilepsy, as others have previously suggested. Furthermore, magnetic source imaging shows a higher resolution of dipole localization compared with conventional electroencephalography, which may ultimately improve prediction of deficits. This reaffirms that magnetoencephalography is a valuable diagnostic tool in the evaluation of children with benign rolandic epilepsy.

Prevalence of epileptiform activity in healthy children during sleep

BACKGROUND

The term epileptiform discharge typically refers to interictal paroxysmal activity that occurs more commonly during sleep. This type of paroxysmal activity does not include the electroencephalographic (EEG) activity observed during a seizure. The prevalence of epileptiform activity in the general pediatric population is unknown.

METHODS

Polysomnographic (PSG) studies were conducted in otherwise healthy children recruited from the general population and with no previous history of seizures or any other medical conditions. All sleep studies included an eight-lead EEG montage. Spike and sharp waves, either alone or accompanied by slow waves, occurring singly or in bursts lasting <5s were considered as representing epileptiform activity.

RESULTS

Nine hundred seventy children underwent overnight PSG. In 14 children, evidence of epileptiform activity, in the absence of any additional abnormality in the PSG, occurred. Thus, the prevalence of epileptiform activity was 1.45%. Epileptiform patterns found were either spike or spike and wave and were more prominent during non-rapid eye movement (NREM) sleep, with 11 patients presenting spike and spike and wave patterns in the centro-temporal regions. Four of the six children who underwent neurocognitive tests exhibited abnormal findings in areas of behavior, attention, hyperactivity, and learning.

CONCLUSION

Epileptiform activity in otherwise healthy children from the community is relatively frequent and, if confirmed by prospective studies, could be associated with suboptimal cognitive and behavioral functions. Increased awareness by sleep professionals and use of PSG montage that includes temporal leads and >2 standard EEG leads should facilitate the detection of epileptiform activity in children.

Role of interictal epileptiform abnormalities in cognitive impairment

The epileptic encephalopathies are conditions in which neurological deterioration is attributable entirely or partly to epileptic activity and is due to very frequent or severe seizures or severely abnormal electroencephalograms (EEGs), or both. Evidence for the concept that seizures or the abnormal EEGs are responsible for the cognitive deterioration is the observation that patients can improve dramatically when therapy eliminates or reduces seizure frequency and improves or normalizes the EEG. For example, children with the syndrome of continuous spike-wave of sleep (CSWS) have electrical status epilepticus during sleep (ESES) and cognitive regression. Although seizures often occur in the disorder, there are indications that the EEG abnormalities are responsible for the cognitive regression. Interictal spikes, which correspond to a large intracellular depolarization with evoked action potentials, in many ways mimic a "miniseizure." Interictal spikes can result in transitory cognitive impairment with the type of deficit dependent on where in the cortex the spike arises. We suggest that interictal spikes, particularly if frequent and widespread, can impair cognitive abilities, through interference with waking learning and memory, and memory consolidation during sleep.

Cognitive and behavioral effects of nocturnal epileptiform discharges in children with benign childhood epilepsy with centrotemporal spikes

This review addresses the effects of subclinical localized epileptiform discharges during sleep in children with benign childhood epilepsy with centrotemporal spikes (BCECTS) on cognition and behavior. A diversity of educational deficits, behavioral impairments, language delay, and neuropsychological test results have been reported in children with BCECTS. The occurrence of atypical seizure characteristics seems to be related to language delay, and several atypical EEG characteristics are related to cognitive or behavioral problems. It remains to be shown whether treatment of nocturnal discharges in children with BCECTS is indicated to improve cognitive and behavioral problems.

Written language skills in children with benign childhood epilepsy with centrotemporal spikes

PURPOSE

The goal of this work was to study written language skills in children with benign childhood epilepsy with centrotemporal spikes (BCECTS) in the absence of atypical clinical or electroencephalographic (EEG) features (n = 32), as compared with controls (n = 36).

METHODS

BCECTS patients (7-16 years), attending regular school, without cognitive or behavioral regression, or atypical EEG patterns, completed four tests assessing written language skills and one nonverbal cognitive test. School performance information was recorded. Seizure types, duration, and frequency; awake and sleep interictal EEG findings; and medication status were documented. Epilepsy and educational outcome was recorded for a period of 1-5 years after diagnosis.

RESULTS

As a group, BCECTS patients performed significantly worse than controls in spelling, reading aloud, and reading comprehension; presented dyslexic-type errors; and frequently had below-average school performance. Among 11 with poor written language performance, 4 had developmental dysfunctions before school and seizure onset and, as a group, demonstrated low performance on a nonverbal cognitive test. Even though 65.6% were on anticonvulsants due to frequent seizures and/or seizures while awake, none belonged to the atypical BCECTS spectrum with respect to clinical or EEG findings. Increased epilepsy duration and seizure frequency were less represented in patients with no or mild written language problems than in those with poor performance. Otherwise, clinical course and EEG findings in this group were no different than those for the 11 children with severe written language problems. Clinical follow-up indicated that learning problems appear persistent and several children require remedial classes and/or tutoring after the epilepsy has resolved.

CONCLUSIONS

Children with severe but not atypical BCECTS performed, as a group, significantly worse than controls in written language skills, specifically in spelling, reading, aloud and reading comprehension; they also presented many difficulties also found in children with dyslexia. However, poor written language performance was not considered specific to BCECTS because it occurred in children with generally low cognitive capacity and/or preexisting developmental dysfunctions. Moreover, a dissociation between epilepsy outcome and learning problem outcome, in the subgroup with poor performance, casts doubt on the existence of a possible causal link between BCECTS and educational performance.

Learning disability: occurrence and long-term consequences in childhood-onset epilepsy

This study analyzed the occurrence of learning disability (LD) in adults with childhood-onset epilepsy and the impact of LD on medical and social outcome. Any LD occurred in 76%: in 57% of mentally normal (IQ>85), in 67% of mentally near-normal (IQ=71-85), and, self-evidently, in all mentally retarded (IQ<71) adults. Half of the patients (51%) with LD had mental retardation. In multivariate analysis, mental retardation and subsequent LD were predicted by occurrence of cerebral palsy (odds ratio [OR]=3.83; 95% confidence interval [CI]=1.77-8.28, P=0.0006), onset of epilepsy before the age of 6 years (OR=3.63, 95% CI=1.57-8.42, P=0.0026), and poor early effect of drug therapy (OR=2.78, 95% CI=1.43-5.39, P=0.0025). Among mentally normal or near-normal subjects, a symptomatic etiology of epilepsy was the only predictor (OR=7.72, 95% CI=3.02-19.76). The degree of LD significantly affected medical, social, and educational long-term outcomes.