Spectral EEG analysis following hemispheric stroke

Quantitative EEG frequency analysis was performed within the acute stage and after the recovery in 40 patients with hemispheric stroke in order to analyze ipsi- and contralateral alpha peak frequency (APF) and band power changes. Localization of hemispheric lesion was determined by computer tomography. Changes of clinical scores were compared with the alpha asymmetries. In the cases of small subcortical infarcts good improvement of alpha activity was observed over the affected hemisphere; contralateral APF was relatively preserved. Bilateral symmetric reduction of APF was found in territorial middle cerebral artery infarcts, with poor tendency of recovery of alpha power and neurologic status. These findings suggest transitory derangement of alpha generators in the contralateral hemisphere evidenced by APF and power asymmetries. EEG signs of contralateral alpha reduction may be due to the remote effect of primary ischemic lesion indicating an electrical diaschisis phenomenon in the acute phase of stroke. EEG signs of diaschisis may anticipate a poor recovery of alpha activity and clinical status in the post-stroke period.     

Serum CK-BB activity in the preterm infant and outcome at two and four years of age

The relationship between serum creatine kinase brain-specific isoenzyme (CK-BB) activity immediately after birth and neurodevelopmental outcome at two and four years corrected age was studied prospectively in 45 preterm infants (less than 34 weeks gestation). Nine infants died during the neonatal period and one was lost to follow-up. Of the 35 children available for follow-up, seven had motor disabilities: four severe diplegia, two mild to moderate diplegia and one hemiplegia. No relationship existed between these motor disabilities and serum CK-BB activity after birth. There seemed to be a relationship between increased serum CK-BB after birth and low scores on the Bayley Scales of Mental Development, but this did not reach statistical significance. At the age of four years, four of the five survivors with high serum CK-BB activity after birth (greater than 25U/L) needed special schooling because of mental retardation. Increased serum CK-BB activity after birth may be associated with delayed mental development, but further study is needed, especially of asphyxiated infants.     

Spectral analysis of the EEG in craniocerebral trauma

The objectives of the present study were to evaluate the relationship between the fractional amplitudes of the EEG derived from power spectral analysis (PSA) of the electroencephalogram (EEG) and depth of coma measured clinically with the Glasgow Coma Score, and to assess the accuracy of PSA in predicting long-term outcome. Thirty-two patients rendered unconscious by blunt head injury (mean (GCS = 7) had intermittent EEG recordings daily from 1-10 days post injury. There was a significant correlation between fractional amplitude of the EEG and the GCS. The rate and magnitude of change in the EEG and GCS were also correlated. There were significant differences in PSA parameters between improved and deteriorated patient groups at the termination of monitoring (p = .02) and in the change of PSA parameters over time (p = .02). Using linear discriminant analysis of PSA parameters, the accuracy of outcome prognostication based on the six month outcome was approximately 75%. Accurate classification of outcome was possible in a number of patients in whom there was little or no change in the GCS during the period of monitoring.     

Predicting developmental outcome at school age from infant tests of normal, at-risk and retarded infants

The predictive validity of developmental testing was investigated in term, preterm and retarded children. Verbal, performance and locomotor development were assessed at various ages and individual development curves constructed. Inter-age correlations between development tests at nine to 24 months and intellectual assessment at seven years revealed a strong effect on prediction for age at testing and level of mental performance. Categorisation by level of mental performance demonstrated that at seven years 98.6 per cent of the children with developmental quotients (DQs) greater than 85 at 24 months achieved IQs greater than 85, while 98.7 per cent of the seven- to eight-year-old children with DQs greater than 85 at nine to 24 months achieved IQs greater than 85. The Griffiths language and performance scores and their combination were the strongest predictors of later intellectual functioning. The social score was of moderate significance, while the locomotor score had no predictive value. Analysis of individual development curves revealed that prediction was hampered in some children by factors not detectable by statistical analysis, such as dissociations in development, organic impairment and major life events. Among the prenatal, perinatal and postnatal variables studied, only socio-economic status was of predictive significance; its effect depended on the level of mental performance and was most marked in term children, but it had no effect on retarded children.     

Family nurture intervention alters relationships between preterm infant EEG delta brush characteristics and term age EEG power

ObjectiveFamily Nurture Intervention (FNI) facilitates mother/infant emotional connection, improves neurodevelopmental outcomes and increases electroencephalogram (EEG) power at term age. Here we explored whether delta brushes (DB), early EEG bursts that shape brain development, are altered by FNI and mediate later effects of FNI on EEG.MethodsWe assessed DB characteristics in EEG data from a randomized controlled trial comparing infants with standard care (SC, n = 31) versus SC + FNI (n = 33) at ~35 and ~40 weeks GA.ResultsCompared to SC infants, FNI infant DB amplitude increased more from ~35 to ~40 weeks, and FNI infants had longer duration DBs. DB parameters (rate, amplitude, brush frequency) at ~35 weeks were correlated with power at ~40 weeks, but only in SC infants. FNI effects on DB parameters do not mediate FNI effects on EEG power or coherence at term.ConclusionsDBs are related to subsequent brain activity and FNI alters DB parameters. However, FNI’s effects on electrocortical activity at term age are not dependent on its earlier effects on DBs.SignificanceWhile early DBs can have important effects on later brain activity in preterm infants, facilitating emotional connection with FNI may allow brain maturation to be less dependent on early bursts.     

Spectral analysis of all-night sleep EEG in healthy adults

Power and coherence spectra were computed from all-night sleep EEG records in 6 healthy adult subjects. Derivations were from F3, F4, P3, P4, O1, O2, T3, and T4 to the vertex (Cz). Records were conventionally scored into sleep stages. Average power per sleep stage was maximal at frequencies 0.4-6 c/s in stage 4, at 6-10 c/s in either stage 3 or stage 4, at 12-14 c/s in stage 2 and at 14-30 c/s in stage 1. The average power range from highest values in the lowest frequency band to lowest values in the highest frequency band showed marked differences between sleep stages: It was lowest (12-14 dB) in stage 1, followed by stage 2 (20-22 dB), and stage 3 (16-28 dB), and largest in stage 4 (29-32 dB). REM sleep (15-16 sB) was between stage 1 and 2. The waking state showed an average power range of 11-15 dB. Alpha power at 8-10 c/s in occipital and parietal leads was remarkably constant during sleep, i.e. independent of sleep stage. Coherence showed maximal values at 2-8 c/s in REM sleep, at 8-12 c/s in stage 4, at 12-17 c/s in either stage 3 or 4, and at 17-30 c/s again in stage REM. There was significant coherence increase at 2-8 and 17-30 c/s from NREM to REM sleep, most pronounced between parietal to vertex derivations. Overall coherence between both occipital-to-vertex, or between occipital and parietal-to-vertex derivations, was essentially higher than in the other derivations. The results, essentially, give a comprehensive phenomenology of the dynamic spectral structure of all-night sleep EEG. They suggest that the different brain states during sleep (e.g. stage 1 NREM vs. REM) which are associated with different functions (e.g. hypnagogic hallucinations vs. dreams) differ in EEG spectral parameters if coherence is considered. Likewise, they suggest that studies of automatic sleep staging based exclusively on EEG spectral parameters appear promising.     

Spectral analysis of rapid (beta) EEG activity

Spectral analysis techniques provide high resolution of the beta frequency range and, if a logarithmic transformation is used, also of lower level intensity. This is in contrast to the generally poor resolution of fast activity in the time domain, an effect which may be compared with that of a magnifying glass applied to beta activity. In the frequency domain several different types of beta activity may be distinguished, i.e., (1) narrow; (2) medium; (3) broad-band beta; (4) harmonic beta where the beta component shows a harmonic relationship to a lower frequency component; (5) complex beta as a mixture of 2 or more of the foregoing types; and (6) undefined beta, where the relative increase of beta power is the only assessable feature. If observed, significant coherence occurs most frequently between antero-posterior leads in activities of types 1 and 2, whereas coherence between hemispheres is generally low. Broad-band beta seems to be essentially non-coherent. Coherence of harmonic beta depends largely on the features of the underlying component. Bi-coherence analysis may be of help to further analysis of harmonic or complex beta activity.     

EEG of the very premature infant born at 24 to 30 weeks gestational age. Definitions and normal area]

This article aims at summarizing normal EEG criteria and their maturational pattern in premature infants of 24 to 30 weeks gestational age. Although very premature infants with a normal outcome are not numerous, their normal EEG patterns must be known, as EEG constitutes a basis for neurological prognosis. Background activity is first discontinuous. Discontinuity decreases thereafter with increasing age, so that some long periods of continuous activity may be observed in active sleep, around 30 weeks of age. Conversely, interburst intervals become shorter and the proportion of time without EEG activity is decreasing. Based on EEG activity and eye movements, a rough sleep-state differentiation was described as soon as 25 weeks of gestational age and is completely achieved at 30 weeks. The main EEG figures are high-voltage delta waves of higher amplitude and slower frequency in younger infants. Temporal delta waves occur in sequences, these are very characteristic of the very premature infant; thereafter, they become smaller, less numerous and eventually disappear around 27-28 weeks. In contrast, occipital delta waves remain numerous and of high voltage, are usually bilateral and superimposed with fast rhythms. The two types of frontal delta waves that are observed in 24-27 weeks prematures disappear with maturation. Bursts of synchronized delta waves are less numerous than localized delta waves and also disappear before 28 weeks of age. Finally, diffuse theta bursts are mainly recorded at 26-27 weeks GA and become more localized in temporal areas with maturation. At 30 weeks, they are observed on temporal areas, mainly during slow-wave sleep.     

Spectral analysis of neocortical and hippocampal EEG in the protein malnourished rat

In these studies, power spectral analysis techniques were utilized to quantify changes in the cortical and hippocampal EEG obtained from rats reared on either an 8% or 25% casein diet as they mature from 14 to 22 days of age. Analyses of the power spectral data obtained from the frontal cortex of rats reared on the 25% casein diet during this preweaning period (14-22 days) indicated increases in the power in the 0.5-3.5 c/sec frequency band primarily during slow-wave sleep. Prenatal protein malnutrition (8% casein diet) significantly reduced the low frequency power content in the cortical EEG obtained during slow-wave sleep at 18 and 22 days of age. Analyses of power spectral data obtained from the hippocampal EEG during REM sleep also revealed developmental and diet-related differences. The frequency at which the peak power occurs in the theta band (4-11 c/sec) was found to increase normally in a linear fashion from 14 to 22 days of age (from 4.4 to 5.5 c/sec) in rats reared on the 25% casein diet. In addition, power in the 4-7 c/sec band significantly increased during this preweaning period. Prenatal protein malnutrition significantly slowed the development of theta frequency and produced higher values of power in the component of theta rhythm. Finally, vigilance profiles showed that rats normally progress from 14 days of age when REM sleep dominates their vigilance profile, to 22 days of age when they spend significantly more time in slow-wave sleep. Prenatal protein malnutrition retards this normal developmental sequence by significantly reducing the REM sleep time at 14 and 18 days of age and increasing the time spend in aroused waking at both these ages. However, at the time of weaning, i.e., at 22 days of age, these differences in sleep-waking behavior were no longer observed to be significant.     

Spectral versus visual EEG analysis in mild hepatic encephalopathy.

OBJECTIVE: Spectral EEG analysis has been claimed to reduce subjective variability in EEG assessment of hepatic encephalopathy and to allow the detection of mild encephalopathy. METHOD: To test such assumptions, 43 digital EEG were recorded in 32 cirrhotics without overt encephalopathy or with grade 1 overt encephalopathy; 7 patients were re-tested (2-5 times) in their follow up. All patients underwent psychometric assessment. Nineteen controls were considered. EEG were blindly evaluated by two electroencephalographers and by spectral EEG analysis performed according to 3 different techniques. RESULTS: The reliability of the classification based on spectral analysis (biparietal technique) was higher than that based on a three-degree qualitative visual reading (concordance/discordance = 58/4 versus 46/16 P < 0.01) and comparable with that of semiquantitative visual assessment based on posterior basic rhythm (concordance/discordance = 55/7 P = 0.5). The accuracy of spectral EEG analysis was higher than that of qualitative visual EEG readings alone (90 versus 75%) and comparable to semi-quantitative visual assessment (87%), however, statistical significance was not reached. In the follow-up, the variations of theta and delta relative power were found to be significantly correlated with psychometric variations. CONCLUSIONS: In conclusion, spectral EEG analysis may improve the assessment of mild hepatic encephalopathy by decreasing inter-operator variability and providing reliable parameters correlated with mental status.     

Spectral analysis of hippocampal unit train in relation to hippocampal EEG

Sampling and analysis programs are implemented on a microcomputer for the computation of autopower, coherence and phase spectra of unit train and EEG. Application to the hippocampus reveals that both theta and fast activity in the EEG are correlated with different phase relationships with unit activity. The estimate of coherence and phase spectra of unit-EEG relationship has not been reported before and is unique for the present method.