Hemispheric specialization in children with unilateral epileptic focus, with and without computed tomography-demonstrated lesion

The Detection of the Negative Effects of Interictal Epileptiform Discharges on Cognition: An Event-Related Potential Study

Evidence from a neuropsychological test revealed that interictal epileptiform discharges (IEDs) may have significant impact on cognitive performance. Sometimes, neuropsychological tests may not be sensitive to detection of mild cognitive changes. We applied P300 and mismatch negativity (MMN) to detect mild cognitive changes caused by small amount of IEDs. Sixty-seven adult epilepsy patients and participants were divided into six groups according to different IEDs index. The patients with IED index greater than 7.5% showed longer latency and lower amplitude in the test of P300 and MMN than patients with IED index less than 7.5%, which indicated mild impaired cognitive function. The negative effect of IED index greater than 10% on cognitive has been found by neuropsychological test, whereas the mild negative effect of IED index greater than 7.5% has only been found by P300 and MMN. So, P300 and MMN may be more sensitive than neuropsychological tests to detect mild cognitive impairment caused by IEDs.

Cognitive correlates of interictal epileptiform discharges in adult patients with epilepsy in China

OBJECTIVE

Learning difficulties or cognitive impairment has been observed in many patients with epilepsy. Evidence from neurophysiologic and functional neuroimaging suggests that epileptic seizures and/or epileptiform activity can be the dominant factors inhibiting specific brain areas. However, most previous studies were focused on cognitive performance in children. In this study, we analyzed a new cohort of adult patients with frequent interictal epileptiform discharges (IEDs).

METHODS

Data from 67 adult patients with epilepsy were reviewed. Electroencephalography (EEG)-video recording and cognitive testing were performed, and the IED index was estimated as a percentage assigned to one of four categories (<1%, 1-10%, 10-50%, and >50%) during either wakefulness or sleep. Correlations of cognitive test results and clinical characteristics of IED categories were analyzed. The effects of the frequency, duration, location, and sleep-wake cycles of IEDs on cognition (intelligence and memory capacity) were analyzed.

RESULTS

Patients with an IED index >10% showed impaired performance on the Chinese Wechsler Adult Intelligence Scale (WAIS-RC) and the Chinese Wechsler Memory Scale (WMS). This effect was detected independently from other IED frequencies and other IED-related variables, such as duration, distribution, and location. The impact of waking or sleeping IEDs was of equal importance in contributing to impaired WAIS-RC and WMS performance.

CONCLUSION

An IED frequency of more than 10% in both waking and sleeping EEGs is associated with impaired cognitive performance in adult patients. However, whether patients with a high IED frequency but low seizure frequency will benefit from antiepileptic treatment should be examined in future studies.

Cognitive effects of interictal epileptiform discharges in children

Frequent interictal epileptiform discharges (IEDs) may have effects on cognition. We analysed a group of 182 children with different epilepsy syndromes as well as children with IEDs without observed seizures [corrected], with 24-h ambulatory EEG and cognitive tests. The IED index was estimated, in wakefulness and in sleep, as percentage of time in five categories (0%, <1%, 1-10%, ≥10-50% and ≥50%). IEDs were defined as spikes or spike-wave complexes, isolated or occurring serially (in runs) without evident clinical signs of a seizure. The IED categories were correlated to cognitive test results and epilepsy characteristics. The group of patients with diurnal IEDs in ≥10% of the EEG record showed impaired central information processing speed, short-term verbal memory and visual-motor integration. This effect was seen independently from other EEG-related and epilepsy-related characteristics, and independently from epilepsy syndrome diagnosis. The impact of the nocturnal IEDs was of less importance; only contributing partially to the slowing of central information processing speed. We conclude that frequent IEDs (in more than 10% of the record) in the awake EEG can impair cognitive performance in children. Whether children with a high diurnal spike frequency and low seizure frequency can benefit from antiepileptic treatment should be examined in controlled trials.

Disengagement and inhibition of visual-spatial attention are differently impaired in children with rolandic epilepsy and Panayiotopoulos syndrome

We assessed voluntary orientation and reorientation of visuospatial attention in 313 healthy 6- to 22-year-old participants, 30 children suffering from benign epilepsy with centrotemporal spikes (BECTS) and 13 children with Panayiotopoulos syndrome (PS). The developmental section highlights the late development of reorienting skills. Only children with BECTS-R showed a strong tendency toward a rightward bias in attentional orientation. Additionally, a unilateral deficit of disengagement characterizes the patients with BECTS-R and comorbid ADHD. Right rolandic spikes seem to aggravate subclinical reorienting difficulties. Finally, children with PS failed to diffuse inhibition, except in the nearest area outside the attentional focus. This deficit could be attributed to the typical occipital-to-frontal spreading of the spikes in PS. By showing distinct attentional deficiencies according to the epileptic syndrome and the epileptic focus lateralization in BECTS, the results provide new evidence for alterations of attentional mechanisms by interictal epileptic activity, which probably contribute to learning difficulties.

Atypical hemispheric asymmetries for the processing of phonological features in children with rolandic epilepsy

We assessed language lateralization in 177 healthy 4- to 11-year-old children and adults and atypical asymmetries associated with unilateral epileptic foci in 18 children with benign epilepsy with centrotemporal spikes (BECTS). Dichotic listening results revealed two indices of immature functional asymmetry when the focus was left-sided (BECTS-L). First, children with BECTS-L did not show left hemisphere dominance for the processing of place of articulation, which was recorded in children with BECTS-R and control children. On the contrary, healthy children exhibited a gradual increase in left hemisphere dominance for place processing during childhood, which is consistent with the shift from global to finer-grained acoustic analysis predicted by the Developmental Weighting Shift model. Second, children with BECTS-L showed atypical left hemisphere involvement in the processing of the voiced value (+V), associated with a long acoustic event in French stop consonants, whereas right hemisphere dominance increased with age for +V processing in healthy children. BECTS-L, therefore, interferes with the development of left hemisphere dominance for specific phonological mechanisms.

Nonverbal dichotic test in patients with epilepsy

Auditory processing during childhood may be altered if there is any predisposing factor during the course of development. Neurological disorders are among the risk factors for auditory processing disorders. Some studies have shown verbal auditory processing disorder in children with epilepsy.

Objective

To verify the performance of children with epilepsy on a nonverbal dichotic test.

Methods

Thirty-eight subjects, 23 female and 15 male, ranging from 7 to 16 years of age with neurological diagnosis of idiopathic epilepsy, without clinical or imaging evidence of cerebral lesion were evaluated. Patients were divided into two groups: 23 patients diagnosed with partial seizures and 15 patients with generalized seizures. Illiterate children, children with hearing thresholds exceeding the normal range and with brain lesions confirmed either clinically or by imaging tests were excluded from the study group.

Results

Analysis of the performance of epileptic patients with partial and generalized seizures on the Nonverbal Dichotic Test revealed that the majority of patients with epilepsy showed impairments in the test, with no significant differences related to seizure type, generalized or partial. Although patients with partial and generalized seizures performed similarly, all the epileptic patients showed different performance to a normal population.

Conclusions

This study revealed a high prevalence of impairments among epileptic patients in relation to nonverbal processing in a dichotic paradigm.

Neuropsychological deficits in monozygotic twins with childhood epilepsy with occipital paroxysms

We report a unique pair of monozygotic twins with childhood epilepsy with occipital paroxysms who showed subtle cognitive deficits. The twin with a more severe epileptic disorder showed a more severe impairment of cognitive functioning. We suggest that epileptic focus may act as an element of disturbance in the development of primary functions and may give rise to a neuropsychological impairment proportionate to the severity of the epileptic activity.

Verbal memory impairment in children with focal epilepsy

Findings of both material- and hemisphere-specific influence on memory performance in children with epilepsy are inconsistent. Verbal memory of 80 children with focal epilepsy, aged 7 to 16, was assessed and compared with verbal memory of 80 healthy schoolchildren. The Verbal Selective Reminding test was used to distinguish between patients with left-sided (N=38) and patients with right-sided (N=42) electroencephalographic focal abnormalities. In addition, groups with temporal (N=36) and extratemporal (N=44) focal epilepsy were compared. Effects of seizure-related variables were also assessed. Children with focal epilepsy scored significantly lower on tests when compared with the healthy group. Lateralization of the EEG focus was not found to significantly affect verbal memory performance. Only the CLTR component of the Verbal Selective Reminding test was susceptible to lateralization and localization effects. Differences between the group with left and the group with right temporal epilepsy (P<0.03) and between the group with temporal and the group with extratemporal epilepsy (P<0.01) reached statistical significance.

Hemispheric lateralization of cognitive functions in children with centrotemporal spikes

We assessed the impact of unilateral epileptic foci in benign idiopathic partial epilepsy of childhood with rolandic discharges (BECT) on performance and hemispheric specialization in lateralized cognitive functions. Six children with BECT with a left-sided focus (BECT-L), 6 children with BECT with a right-sided focus (BECT-R), and 12 control children were tested in verbal, visual-spatial, and visual-attention tasks, with visual hemifield presentation. Children with BECT-R were impaired in the visual-spatial task relative to those with BECT-L, and the typical left-hemisphere (LH) advantage was not reported in the verbal task in children with BECT-L. Additionally, the classic global superiority effect was lacking in children with BECT-R, which may be due to impaired performance of the right hemisphere specialized in global (vs local)-level processing. These data argue for the deleterious effect of epileptic discharges per se on cognitive functions in the developing brain, and the decisive role of epileptic focus lateralization in specific cognitive impairments and hemispheric specialization.

Oxcarbazepine monotherapy in benign childhood epilepsy with centrotemporal spikes: a clinical and cognitive evaluation

We report on 70 patients (aged 5.2-11.6 years) newly diagnosed with benign childhood epilepsy with centrotemporal spikes (BECTS) who were assigned to oxcarbazepine (OXC) monotherapy. All of them underwent clinical and electroencephalographic examination at baseline and at 3- to 6-month intervals during the study. Psychometric assessment was performed at baseline and after 18 months of treatment with the WISC-III, Illinois Test of Psychomotor Abilities, DSM-IV, and Bender-Santucci test. The Mann-Whitney U test was used to describe differences in the frequency of abnormal findings: (1) at initial evaluation, comparing patients with a matched group of 45 healthy controls, and (2) after 18 months of OXC monotherapy, as an individual follow-up in the patient group. Cognitive assessment at baseline revealed mild learning disabilities in 9% of patients and 7% of controls; all participants had a normal intelligence quotient. During the follow-up, sustained cessation of seizures under medication was observed in 53% of patients; an additional 21% had some relapse but were subsequently rendered seizure free, 21% experienced a >50% improvement, and 5% showed no improvement. Normalization of interictal epileptiform activity was observed in 58% of patients, 35% showed an improvement in the grade of electroencephalographic pathology, and 7% manifested no change at all. The initial mildly weak scores in isolated cognitive domains did not deteriorate, and even improved in some cases, during the course of the study, with concomitant electroencephalographic improvement or normalization and effective seizure control. The results of this study suggest that OXC is effective in preventing seizures and normalizing electroencephalograms and seems to preserve cognitive functions and behavioral abilities as long-term monotherapy in children with typical BECTS.

Verbal dichotic listening and manual performance in children with congenital unilateral brain lesions

The authors assessed manual performance and verbal dichotic listening performance in 16 epilepsy-free children with congenital unilateral brain lesions and normal IQ to investigate cerebral reorganization. In all children, the paretic hand had fair grip function, but reaction times were impaired, and cerebral reorganization of hand function in those with right hemiplegia was shown by the high incidence of pathological left-handedness. The dichotic listening results showed that most children with left lesions had a left ear advantage significantly related to the extent of brain damage. This finding suggests that extent of cortical damage and presence of thalamic involvement, irrespective of neuropathology, are the primary factors inducing rightward cerebral language reorganization in children with unilateral congenital brain lesions.

Neuropsychologic effects of frontal lobe epilepsy in children

Most published neuropsychologic studies on frontal lobe epilepsy have been performed on mixed groups of adults and adolescents with epilepsies of varying etiology. The cognitive profile of frontal lobe epilepsy in children has not been defined. The purpose of this study was to assess neuropsychologic performance in children with frontal lobe epilepsy. Intelligence and executive functions were examined in eight children (age 6 7/12 years to 13 11/12 years) with frontal lobe epilepsy. Performance was related to the focus side, seizure frequency, and age of epilepsy onset. Frontal lobe epilepsy was associated with a range of frontal dysfunctions, but IQ was generally spared. Left focus was associated with deficits in categorization, verbal long-term memory, and detailed visuospatial analysis. Frequent seizures correlated with attention difficulties and inability to inhibit impulsive responses. Children whose epilepsy appeared before age 6 years had reduced ability to change behavioral strategies. Frontal epileptic activity alone can cause selective frontal deficits, the severity and nature of which are related to side, seizure frequency, and age of epilepsy onset. These findings require confirmation on larger series of selected children.

Timing and type of congenital brain lesion determine different patterns of language lateralization in hemiplegic children

Cerebral lateralization for language has been assessed by means of the Fused Dichotic Words Test in 26 hemiplegic children (mean age 7 years 2 months) with congenital focal brain damage (ten with left, seven with right and nine with bilateral lesions). The specific aim of the study was to investigate the relation between lesion characteristics (side, size and localization) at high field, multiple plane MRI and the pattern of language lateralization at the dichotic test. Significant side and site effects were found at group level; in children with lesions of the left hemisphere a left ear advantage (LEA) was found, while children with right lesions had the expected right ear advantage (REA). Analysis of individual data, however, revealed that type of lesion, cortical-subcortical or periventricular, occurring at term or preterm age, respectively, may be the primary factor responsible for inter versus intrahemispheric organization of language after congenital brain lesions. Only when the left lesions involved cortical-subcortical regions encroaching the temporal lobe and occurred at term age, was language reorganized in the right hemisphere; when lesions (whether left or right) involved only the periventricular white matter and occurred at preterm age, language was lateralized in the left hemisphere. Our results provide evidence that within 'congenital hemiplegias', strictly defined as hemiplegias whose causal lesion occurs before the end of the neonatal period, different recovery mechanisms are at work, depending on the type of brain lesion (neuropathology) which largely depends on the timing of insult (preterm vs. term period).

Neurocognitive development of children with congenital unilateral brain lesion and epilepsy

The aim of this study was to specify the neuropsychological deficits characteristic of children with unilateral non-progressive brain lesion. In order to assess these specific functions, we used a comprehensive model of congenital hemiparesis with partial epilepsy and newly diagnosed partial epilepsy without hemiparesis. The neuropsychological examination was performed using the NEPSY test battery on 44 children aged from 4 to 9 years. The children were divided into three groups: 18 children suffering from congenital hemiparesis with chronic partial epilepsy, 12 children with newly diagnosed partial epilepsy prior to anti-epileptic treatment, and 14 healthy controls matched by sex, age, and socioeconomic status. Children with congenital hemiparesis and epilepsy had a more clearly expressed cognitive dysfunction, especially in language, visuo-perceptual and memory tasks, than children with newly diagnosed partial epilepsy. The profile of cognitive weakness appears to be diffuse and quite similar in both groups, and it did not demonstrate a clear effect of lateralization, according to the side of epileptic electroencephalogram discharges. Children within both groups are likely to have a high risk of developing attention, phonological, visuo-perceptual, and memory deficits in their life. Especially interesting and surprising was the fact that the newly diagnosed epilepsy group demonstrated impairment not only in attention, visuo-perceptual and short-term memory skills, but also in auditory perception, lexical function, and the comprehension of speech. Therefore, it is recommended that children with epilepsy would undergo neuropsychological examination in order to assess their cognitive abilities.

Language development in children with congenital strokes

The congenital lesion population provides an excellent forum to investigate the issues of innate specialization and plasticity. Effects of early lesions on left and right hemisphere function reflect both the cognitive process under study and biological/neurological factors of lesion parameters and hemispheric maturation rates. In general, toddlers with both congenital left and right lesions show mild to moderate delays in language acquisition. School-age children with left hemisphere lesions have more problems with language and language-based academic skills than those with right hemisphere lesions, but the problems are subtle and do occur in both groups. This pattern stands in sharp contrast with the adult, who shows striking language deficits with acquired lesions only in the left perisylvian region. Thus, there is evidence in these studies of the immature nervous system for both innate specialization and plasticity, as well as a right hemisphere contribution to language acquisition and verbal cognition.