EEG changes in patients during the introduction of carbamazepine.

This study evaluates the EEG changes during the standardized introduction of carbamazepine in 16 previously untreated neurological patients and their relationship to serum levels of carbamazepine and carbamazepine-10,11-epoxide. Therapy was started with a dosage of 400 mg carbamazepine b.i.d. and remained unchanged during the whole study period of 35 days. Frequency analysis of serial EEG records was performed by Fast Fourier Transformation. In comparison to the pretreatment period (1) the mean values of the total power and relative powers of the theta and delta bands increased and (2) the mean values of the relative power of the alpha band and the center frequency decreased. These changes were already established 3 days after the beginning of the treatment and remained constant during the observation period. There were marked interindividual differences. (3) There was no statistically significant correlation between serum levels of carbamazepine or carbamazepine-10,11-epoxide and the EEG parameters. Our results demonstrate that the degree of EEG change primarily reflects individual susceptibility to carbamazepine and its metabolite during the early stage of carbamazepine exposure and is not dose related.     

EEG changes induced by carbamazepine therapy at rest and during mental processes

The effects of carbamazepine (CBZ) on EEG backgrouund activity have been studied, at rest and during mental processes, in 18 epileptic patients suffering from focal epilepsy and starting antiepileptic treatment for the first time. The EEGs were recorded before and after CBZ therapy, at rest with eyes closed (EC), during blocking reaction (BR), fixation (FIX) and mental arithmetic (MA) tasks, and then evaluated by spectral analysis. All data underwent statistical evaluation utilizing the ANOVA and correlation coefficient. The following parameters were evaluated by spectral analysis. All data underwent statistical evaluation utilizing the ANOVA and correlation coefficient. The following parameters were evaluated: mean absolute and relative power and mean frequency. The results have shown that CBZ induced a significant increase of slow activity at rest with EC, which was represented by delta potentials, and was correlated with CBZ plasma levels, In evaluating the different cortical activation patterns, a decrease of the alpha reactivity was noted during BR and FIX, while a significant increase of beta activity was observed during the performance of all tasks. The rwelationship between the increased beta power, possibly reflecting an increase of cognitive activity for processing information, and the lack of a significant decrease of alpha activity are discussed.Paper presented at the National Congress at Serrento in 1991 and selected by the Editorial Board of the Journal     

Quantitative EEG changes in Alzheimer patients during long-term donepezil therapy

Twenty patients affected with probable mild-to-moderate Alzheimer's disease (AD; NINCDS-ADRDA criteria; 14 women and 6 men, mean age 75.2 +/- 7.1 years) who regularly received an oral acetylcholinesterase inhibitor (AChEI; donepezil 5 mg/day; Dz group) were compared with a control group of 11 AD patients (6 women and 5 men, mean age 73.5 +/- 6.0 years) diagnosed and followed up in the pre-AChEIs era (C group). At basal evaluation (t(0)), the 2 groups were comparable for age, education, and severity of disease (Global Deterioration Scale). All patients underwent quantitative EEG (qEEG, average reference, 10-20 International System), and were reexamined about 1 year later (t(1); i.e., after 12.3 +/- 3.6 months the Dz group, and after 13.7 +/- 3.9 months the C group). Log-transformed values of two qEEG bands, i.e. 2-6 and 6.5-12 Hz, were averaged between adjacent channels (frontal F3 and F7, F4 and F8; parietotemporal P3 and T7, P4 and T8) to obtain a qEEG ratio (6.5-12/2-6 Hz.) from one frontal and one temporoparietal region in each hemisphere. Neuropsychological impairment was summarized by the Mini-Mental Status Examination (MMSE). At t(0), both the MMSE score and the qEEG ratio values were somewhat higher in the C than in the Dz group, although nonsignificantly. Between t(0) and t(1), the MMSE score decreased significantly (p < 0.01) more in the C group (-4.36 +/- 2.25) than in the Dz group (-1.45 +/- 2.16), as did the qEEG ratio in the right frontal region (p < 0.01), whereas in the left frontal region the significance level was not reached (p = 0.02). Between t(0) and t(1), the qEEG ratio difference in both frontal regions and in the right temporoparietal region significantly correlated with the MMSE difference (p < 0.01), but neither with time between examinations nor with the difference on the Visual Search Test score. Long-term treatment with Dz led to a lesser deterioration of qEEG, paralleling a milder neuropsychological decline. The effect was significant in frontal regions, possibly because they are relatively spared during the mild-to-moderate phases of the disease.     

EEG changes during long-term treatment with donepezil in Alzheimer's disease patients

Summary. In this pilot study, we examined the long-term treatment effect of donepezil on the quantitative EEG (qEEG) in 12 Alzheimer's disease patients. The qEEGs of the mean absolute and relative amplitudes of betal, alpha, theta and delta activities were obtained at baseline and during donepezil treatment. Comparisons of awake qEEG prior to and during treatment were performed using a 2-way analysis of variance (ANOVA) with repeated measures. In patients with mild dementia (n = 5), the qEEG analysis showed a significant reduction of the mean absolute theta activity (p = 0.05) by donepezil, particularly in frontal and temporo-parietal areas. In patients with moderate/severe dementia (n = 7), a significant decrease in the mean absolute beta 1 activity (p = 0.02), particularly in the frontal and occipital areas may be attributed to disease progression which was not counteracted by the long-term treatment. The differences in qEEG in patients with different stages of dementia under donepezil treatment may be related to different compensatory capacities due to structural and functional brain disturbances. Received January 27, 2001; accepted June 8, 2001     

Effect of carbamazepine treatment on EEG changes induced by different cortical activation patterns in newly referred epileptic patients.

Sixteen epileptic patients suffering from focal epilepsy who underwent antiepileptic drug treatment with carbamazepine (CBZ) for the first time were studied. The EEG was recorded at rest with eyes closed, during blocking reaction (BR), fixation (FIX) and mental arithmetic tasks. The computerized EEG study, performed before and after CBZ therapy, utilized spectral analysis. Data underwent statistical evaluation through Anova and correlation analysis. The parameters evaluated were the mean frequency and the mean absolute and relative power. The results have shown that after CBZ treatment there is a decrease in the alpha reactivity during BR and FIX, while a significant increase in beta activity was observed during all tasks. The effect of CBZ therapy on EEG activity during cortical activation patterns are discussed.     

Dynamic EEG changes during cigarette smoking

Electroencephalograms were monitored before, during and after smoking a single cigarette. Quantitative analysis indicated that smoking produced a characteristic psychostimulant profile involving power reductions in delta and theta and increases in both alpha power and peak alpha frequency. Puff-by-puff analysis yielded similar patterns with the effects emerging by the fourth puff. Delta reductions were evident during the act of puffing and following inhalation. The results are discussed in relation to motivational theories of smoking.     

Reversible EEG changes during rotavirus gastroenteritis

Rotavirus can cause seizures and encephalopathy in infants and young children. We report reversible EEG abnormalities in a 2 year and 7 month old boy who had a single seizure during rotavirus gastroenteritis. His EEG showed bilateral independent temporoparietal sharp waves. The EEG was normal 10 days after the first EEG and the patient has been followed with no neurological sequelae. The EEG literature in children developing seizures secondary to rotavirus infection including ours suggest the involvement of mostly posterior cerebral areas. The localization and reversibility of the process can enlighten the pathophysiology underlying this disorder.     

Antero-posterior EEG changes during the wakefulness-sleep transition.

OBJECTIVES: To investigate the brain topography of the human sleep EEG along the antero-posterior axis during the wakefulness-sleep transition, by means of both a single Hz analysis and a grouped-frequency analysis of EEG changes. METHODS: EEG power values were calculated across a 1-28 Hz frequency range in a 1 Hz resolution during the wakefulness-sleep transition of 7 normal subjects. Topographical changes were assessed from C3-A2, C4-A1, Fpz-A1, Fz-A1, Cz-A1, Pz-A1, Oz-A1 recordings, after averaging individual time series, aligned with respect to the onset of stage 2. RESULTS: The single Hz analysis showed that before sleep onset (SO), the <7 Hz slow frequencies were more prominent at the more anterior scalp locations; this anterior prominence was counterbalanced by a reciprocal prevalence across the >8 Hz frequencies of EEG activity from the occipital areas; while the >13 Hz fast frequencies were not characterized by significant antero-posterior differences. After SO, more EEG power was found in the range of slow frequencies at the centro-frontal scalp locations and a second peak of EEG activity was also revealed within the range of the sigma frequency, higher at the centro-parietal scalp locations. No consistent topographical changes were observed within the range of faster EEG frequencies. Grouped-frequency analysis confirmed these results, also pointing to different changes in the alpha frequency as a function of the SO point. CONCLUSIONS: The results suggest that: (a) the alpha rhythm spreads anteriorly as the transition progresses; (b) several anterior areas first synchronize EEG activity; (c) the functional meaning of the EEG bands during the SO period should be partially revised with regard at least to alpha rhythm; (d) SO coincides with the start of stage 2.     

Quantitative EEG changes in non-demented Parkinson's disease patients before and during L-dopa therapy

Nineteen non-demented Parkinson's disease patients have been studied before and during L-dopa therapy by quantitative EEG performed at rest with eyes closed (EC) and during attentive (BR) and cognitive (FIX) tasks. The data have been compared by ANOVA analysis with those of 22 age-matched healthy subjects. In all three conditions a significant increase of the mean δ power as well as a decrease of β1 power was observed in patients before therapy. Abnormal high δ values were observed in 10 out of 19 patients. L-Dopa therapy did not modify this EEG pattern. After therapy, however, a significant decrease of reactivity to BR and FIX was observed in patients compared to normal subjects. These data confirmed the presence of an EEG synchronization (increase of slow activity and decrease of fast activity) in non-demented Parkinson's disease patients. This pattern, similar to that of subjects with Alzheimer-type dementia, might indicate an intellectual impairment at sub-clinical level. A non-dopaminergic mechanism could be responsible for this impairment     

Lithium-induced EEG changes in patients with affective disorders

In 12 patients with affective disorders (ICD-10: F31, F32, F33), EEGs were recorded before and after 4.4 months of lithium treatment. Effects of lithium on the EEG were analyzed by power spectral analysis controlled for vigilance. We found (1) an increase in relative power in both delta and theta band which was related to the lithium plasma level, (2) a decrease in relative alpha power especially at occipital leads and (3) a reduction of the dominant alpha frequency. The changes in relative power were more pronounced in the right hemisphere, which is in contrast to the hypothesis of a site-specific localization of lithium effects only in left anterior regions.     

Hyponatremia during carbamazepine therapy in patients with intellectual disability

Carbamazepine is an anticonvulsant and psychotropic medication commonly used in the treatment of people with intellectual disability (ID). The incidence of hyponatremia during treatment in this population is unclear. The present study aimed to determine the prevalence of hyponatremia during carbamazepine treatment in patients with ID, and to investigate the risk factors and clinical features of this condition. The prevalence of hyponatremia was retrospectively assessed in 53 people receiving carbamazepine (subject group) and 64 people not receiving carbamazepine (control group) who lived in a residential centre for people with ID. The relationship between serum sodium level, sex, age, daily carbamazepine dose and serum carbamazepine levels was examined. The prevalence of the clinical features of hyponatremia was assessed in this population using a checklist. The prevalence of hyponatremia was 41.5% and 9.4% in the subject and control groups, respectively. The mean serum sodium level in the subject group was significantly lower than that in the control group. Hyponatremia correlates significantly with a high daily carbamazepine dose and a high serum carbamazepine level. The checklist of clinical features was not useful in detecting hyponatremia clinically. Hyponatremia is a common occurrence in this population. In the light of the uncertain significance of mild, chronic hyponatremia, the value of routine monitoring of serum electrolytes has yet to be established.     

Connectivity changes underlying spectral EEG changes during propofol-induced loss of consciousness

The mechanisms underlying anesthesia-induced loss of consciousness remain a matter of debate. Recent electrophysiological reports suggest that while initial propofol infusion provokes an increase in fast rhythms (from beta to gamma range), slow activity (from delta to alpha range) rises selectively during loss of consciousness. Dynamic causal modeling was used to investigate the neural mechanisms mediating these changes in spectral power in humans. We analyzed source-reconstructed data from frontal and parietal cortices during normal wakefulness, propofol-induced mild sedation, and loss of consciousness. Bayesian model selection revealed that the best model for explaining spectral changes across the three states involved changes in corticothalamic interactions. Compared with wakefulness, mild sedation was accounted for by an increase in thalamic excitability, which did not further increase during loss of consciousness. In contrast, loss of consciousness per se was accompanied by a decrease in backward corticocortical connectivity from frontal to parietal cortices, while thalamocortical connectivity remained unchanged. These results emphasize the importance of recurrent corticocortical communication in the maintenance of consciousness and suggest a direct effect of propofol on cortical dynamics.     

Spectral analysis of the EEG in children during the introduction of antiepileptic therapy with valproic acid

The EEGs of 16 newly diagnosed children with primary generalized epilepsy were examined before and during up to 3 years of antiepileptic therapy with valproic acid. Spectral analysis was performed and parameters of the relative power within the conventional frequency bands were compared with norm data. Before treatment no significant differences of the background activity between epileptic children and healthy controls were found. While treatment was able to reduce seizures and spike-wave activity, EEG parameters did not change systematically. There was no relation between valproate serum levels and parameters of the background activity.     

EEG changes during word and figure categorization.

OBJECTIVE: To analyze whether the EEG changes observed during figure and word categorization are compatible with either the dual, the common amodal, or the alternative model (modality-specific codes for words and pictures, where meaning is represented for both in a higher-order amodal system) for semantic knowledge. METHODS: EEG was recorded during word and figure categorization of animals or non-animals in a group of 28 children 8-10 years old. Computation of EEG sources in the frequency domain using variable resolution electrical tomography (VARETA) and their statistical evaluation by statistical parametric mapping were carried out. RESULTS: At all frequencies, there were significant changes between EEG segments prior to the presentation of the stimuli and EEG segments recorded after the stimuli. Post-segments showed more power from 1.56 to 7.02 Hz, and less power than pre-segments from 8 to 12.48 Hz. EEG changes were only observed in the word task at: 3.9 (left occipital), 4.68, 5.46, and 6.24 Hz (temporo-occipital regions). These changes may be associated with visual encoding of words. Frequencies 7.8 and 17.94 Hz increased in prefrontal, anterior cingulate, and anterior temporal regions only during figure categorization. The prefrontal region may be related to object working memory. Thus, these frequencies might be related to figure codification. No significant differences between tasks were observed at 3.12 and 7.02 Hz in very wide brain areas (all lobes except occipital), suggesting that the amodal semantic system storage could be the model compatible with figure and word categorization. CONCLUSIONS: Thus, our results support the modified amodal semantic hypothesis, which advocates that the meanings of both kinds of stimuli are represented in a conceptual memory that receives input from the logogen and iconogen systems.     

Spatiotemporal changes of EEG activity during waking-sleeping transition period

To evaluate the spatiotemporal changes of EEG during waking-sleeping transition or hypnagogic period, spectral analysis of the five scalp EEG on the midline (Fpz, Fz, Cz, Pz and Oz) referenced to the left ear lobe was carried out on seven young male subjects. Power spectra from consecutive samples of 5.12 sec period with 0.2 Hz resolution were studied from 10 min before the manually scored stage 1 onset to 30 min after the onset of stage 1. The average power spectra over 1 min segments and corresponding coefficient of variation (CV) were determined for the frequency bands of delta (1-3 Hz), theta (4-7 Hz), alpha (8-12 Hz), sigma (13-15 Hz) and beta (16-19 Hz). The latency score was defined as the time elapsed from the onset of stage 1 to the first epoch when the frequency band power, using the ANOVA significantly increased (or decreased) in comparison with the average level at the onset of stage 1. Median latency scores for each band were similar to the Cz scores, with a ranking, from early to late, of: alpha (2 min), theta (3 min), delta (5 min) and sigma (5 min). Significant change was not observed on the beta band activity. In terms of the EEG areas, the shortest latency was found in the theta band activity of the Fz EEG (2 min), and the longest was the sigma band activity of the Fpz and Oz EEG (8 min). The average stage 2 latency was 3.5 min when it was measured as time elapsed between the onset of stage 1 and 2. The average curves of delta, theta and alpha band CVs, started to increase just before or immediately after stage 1 onset and continued to increase for about 10 min. If the increased CV or unsteadiness of EEG activity is taken as a characteristic of the hypnagogic period, hypnagogic states may be considered to have continued until about 10 min after the stage 1 onset. Delta-theta activity showed a rapid rise in power after the onset of stage 1 for all areas. Delta power at the occipital, however, increased more gradually, and consistently remained at a lower level. The differences of delta power between Oz and other four electrode sites became clear at 7 min after the onset of stage 1. These regional differences may reflect the termination of hypnagogic effects.(ABSTRACT TRUNCATED AT 400 WORDS)     

Paroxysmal EEG changes in patients with multiple sclerosis]

The electroencephalograms (EEG) and visual evoked potentials (VEP) were recorded in 100 multiple sclerosis patients treated from 1981 to 1989. In 35 cases the EEG records were pathological and in 12 of them they showed paroxysmal changes. Pathological EEG were mostly seen in young patients, during the first relapse, with high degree of Kurtzke's disability score. Patients with paroxysmal changes showed on physical examination brain stem lesions that could be responsible for paroxysmal activity in EEG. The latencies of P100 wave and amplitudes of P100/N120 complex were analysed in two groups of patients (with and without paroxysmal activity in EEG). There was no statistically important difference between two groups, although in the group with paroxysmal changes in EEG some prolongation of the latency of P100 wave and a little higher amplitude of P100/N120 complex were recorded.