Towards a neurobiology of dysfunctional arousal in depression: the relationship between beta EEG power and regional cerebral glucose metabolism during NREM sleep.

This study sought to clarify the neurobiological basis of variations in one aspect of central nervous system 'arousal' in depression by characterizing the functional neuroanatomic correlates of beta electroencephalographic (EEG) power density during non-rapid eye movement (NREM) sleep. First, nine healthy (n=9) subjects underwent concurrent EEG sleep studies and [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) positron emission tomography (PET) scans during their first NREM period of sleep in order to generate hypotheses about specific brain structures that show a relationship between increased beta power and increased relative glucose metabolism. Second, brain structures identified in the healthy subjects were then used as a priori regions of interest in similar analyses from identical studies in 12 depressed subjects. Statistical parametric mapping was used to identify the relationship between beta power and relative regional cerebral glucose metabolism (rCMRglu) during NREM sleep. Regions that demonstrated significant correlations between beta power and relative cerebral glucose metabolism in both the healthy and depressed subjects included the ventromedial prefrontal cortex and the right lateral inferior occipital cortex. During a baseline night of sleep, depressed patients demonstrated a trend toward greater beta power in relation to a separate age- and gender-matched healthy control group. In both healthy and depressed subjects, beta power negatively correlated with subjective sleep quality. Finally, in the depressed group, there was a trend for beta power to correlate with an indirect measure of absolute whole brain metabolism during NREM sleep. This study demonstrates a similar relationship between electrophysiological arousal and glucose metabolism in the ventromedial prefrontal cortex in depressed and healthy subjects. Given the increased electrophysiological arousal in some depressed patients and the known anatomical relations between the ventromedial prefrontal cortex and brain activating structures, this study raises the possibility that the ventromedial prefrontal cortex plays a significant role in mediating one aspect of dysfunctional arousal found in more severely aroused depressed patients.

Changes in forebrain function from waking to REM sleep in depression: preliminary analyses of [18F]FDG PET studies.

Based on recent functional brain imaging studies of healthy human REM sleep, we hypothesized that alterations in REM sleep in mood disorder patients reflect a functional dysregulation within limbic and paralimbic forebrain structures during that sleep state. Six unipolar depressed subjects and eight healthy subjects underwent separate [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) PET scans during waking and during their first REM period of sleep. Statistical parametric mapping contrasts were performed to detect changes in relative regional cerebral glucose metabolism (rCMRglu) from waking to REM sleep in each group as well as interactions in patterns of change between groups. Clinical and EEG sleep comparisons from an undisturbed night of sleep were also performed. In contrast to healthy control subjects, depressed patients did not show increases in rCMRglu in anterior paralimbic structures in REM sleep compared to waking. Depressed subjects showed greater increases from waking to REM sleep in rCMRglu in the tectal area and a series of left hemispheric areas including sensorimotor cortex, inferior temporal cortex, uncal gyrus-amygdala, and subicular complex than did the control subjects. These observations indicate that changes in limbic and paralimbic function from waking to REM sleep differ significantly from normal in depressed patients.

Neonates with electrically confirmed seizures and possible placental associations.

Placental specimens were reviewed from 73 singleton pregnancies of women whose offspring received electroencephalogram (EEG) studies in the neonate period. A group of 43 neonates (postconception age [PCA] 23-44 weeks) with electrically confirmed seizures in the immediate neonate period were compared with 30 healthy preterm and term infants of comparable PCA who had no electrographic seizures. Pathologic placental changes were separated: Group A consisted of chorioamnionitis, edema, meconium staining, and/or retroplacental hematoma. Group B consisted of abnormal villous maturation, infarction, and/or chronic villitis. Logistic regression analyses calculated the odds ratio of having Group A or Group B placental lesions in each neonate group as a function of increasing PCA. For the seizure group, the odds of having Group B with or without Group A placental lesions increased by a factor of 1.2 for each postconception week up to 43 weeks PCA. For a 15-week interval the odds of having Group B lesions for the seizure group increased by a factor of 12.1 (P < 0.007). Ratios were not significant for Group A lesions alone in the seizure group or for either Group B or Group A findings in the neonate group without seizures. Pathophysiologic events in utero leading to Group B rather than Group A findings are associated with electrically confirmed seizures in near-term and term infants. Group A lesions were considered more likely to have intrapartum or peripartum associations, whereas Group B lesions were considered more likely to have antepartum associations.

Regional differences in spectral EEG measures between healthy term and preterm infants.

State-specific spectral electroencephalographic (EEG) values were compared among 14 bipolar channel derivations between two healthy neonatal cohorts. Fifty-five healthy preterm neonates of < or = 32 weeks gestational age at birth were studied with 24-channel recordings over 3 hours at term conceptional age. These were compared with studies of 45 healthy term neonates. Five spectral measures for each channel (i.e., total spectral EEG, delta, theta, alpha, and beta frequency ranges) were calculated for each minute, which was identified as active or quiet sleep, based on visual analysis. Using multivariate analysis of variance, differences at each channel were assessed between neonatal cohorts for both states and cohorts; higher total EEG spectral values were noted during active sleep; whereas higher delta and theta spectral values were noted during quiet sleep. The term cohort had higher values for spectral theta, alpha, and beta power spectra in multiple channels, most significantly in the left central (i.e., C3O1) and sagittal regions (FzCz, CzPz) during both states (P < .0001, adj r2 > or = .2). Both interhemispheric and intrahemispheric differences in spectral values were present. For a healthy preterm cohort, lower spectral energies are expressed during sleep in specific head regions. Physiologic asymmetries exist in the newborn brain which are unique for the preterm infant, emphasizing functional alterations in brain development. How these asymmetries are altered by prenatal or postnatal stress or disease states needs to be explored.

Computer classification of state in healthy preterm neonates.

Nineteen electroencephalographic (EEG) sleep measures describing four physiologic aspects of sleep behavior (i.e. sleep continuity, EEG spectra, body and eye movements, and autonomic measures) were derived from visual and computer analyses of 71 24-channel, 3-hour EEG sleep recordings on 52 healthy preterm neonates from 28-36.5 weeks postconceptional age (PCA). Forty-eight subjects were neurodevelopmentally normal up to 2 years of age. Four electrographic states that comprise tracé discontinu of the preterm neonate were defined in terms of increasing seconds of EEG quiescence per minute. A regression analysis was performed after transformations of nonlinear data sets representing the 19 EEG sleep measures, with the four sleep states as outcome variables. Postconceptional age was also included in these analyses as the 20th explanatory variable. Four measures best defined the EEG sleep states, explaining 75% of the variance: decreasing rapid eye movements per minute, decreasing numbers of spontaneous arousals per minute, increasing spectral theta energies, and decreasing facial movements per minute. Other cerebral and noncerebral measures, including total spectral EEG energies, spectral EEG energies in three bandwidths (i.e. delta, alpha, beta), cardiac and respiratory measures, and body movements, did not contribute as significantly to the prediction. Inclusion of PCA into the regression equation with the four EEG measures, selected by the analysis procedure, indicated that its contribution to state prediction was also small; the effect of PCA on state was found to be explained by the four EEG sleep measures.

Prediction of lower developmental performances of healthy neonates by neonatal EEG-sleep measures.

Previous neurophysiologic studies from our laboratory have demonstrated altered EEG-sleep behavior at conceptional term ages in healthy preterm infant compared with a term cohort. Developmental assessments at 12 and 24 months of age of 16 children in each cohort were compared using MANOVA. Differences were detected on MANOVA between each cohort on Bayley mental and motor performance scores, while social skills (Vineland) and temperament (Carey) were similar. Healthy preterm infants had lower scores at 12 months of age (P < .0001) and 24 months (P < .04) than term infants before adjustment for prematurity. No group differences were observed after adjustment. For the combined cohort of 32 healthy neonates, specific neonatal EEG-sleep measures were included as predictor variables in regression analyses with Bayley mental scores as outcome variables. Lower Bayley mental scores at 12 and 24 months were associated with higher spectral EEG correlations, lower spectral EEG energies in the beta frequency ranges, fewer arousals per minute, lower rapid eye movements per minute, and shorter sleep latencies from awake state to active sleep. Significant associations were observed before adjustment for prematurity at both 12 and 24 months, and after adjustment at 12 months of age for lower spectral beta EEG energies. Lower socioeconomic class also correlated with lower developmental scores. Even in the absence of major neonatal illnesses, brain adaptation to prematurity influences later developmental outcome. Adjustment for "age equivalency" may be required up to at least 24 months of age even in a healthy preterm population.

Computer classification of sleep in preterm and full-term neonates at similar postconceptional term ages.

A classification strategy of neonatal sleep is being developed by comparing visually scored minutes of 21 channels of electroencephalographic (EEG)/polygraphic recordings with the corresponding values for each physiological signal derived from either visual or computer analyses. Continuous 3-hour sleep studies on 54 preterm and full-term neonates at similar postconceptional term ages were acquired under environmentally controlled conditions using a computerized monitoring system. An on-line event marker program recorded behavioral observations. One of three EEG sleep states was assigned to each of 8,995 minutes by traditional visual analysis criteria. EEG spectral values, spectral and nonspectral cardiorespiratory calculations and behaviorally observed movements, arousals and rapid eye movement counts were submitted for discriminant analysis. Based on the total minutes known for each of three states (i.e. active, quiet and awake), linear combinations of all specified digitized parameters were formed into an arithmetic algorithm by use of discriminant analysis, which served as the basis of a state assignment for each minute. Fifty percent of the data were arbitrarily used as the training set to derive the state classification model. The remaining fifty percent of the data were used as the cross-validation "test sample" to determine the accuracy of the classification when compared to the visually analyzed score for each corresponding minute. Thirteen out of 32 physiological measures best predicted state of both preterm and full-term neonatal groups. For both groups, the correct classification for active sleep was 90.3%, quiet sleep was 97.4%, awake was 97% and the overall accuracy was 93.3%. However, the order of significance for specific variables differed between these two neonatal groups. Differences in the order of variables that predict sleep states between preterm and full-term infants may reflect adaptation of brain function of the preterm infant to prematurity and/or prolonged extrauterine experience.

Estimation of gestational maturity of preterm infants by five fetal sonographic measurements compared with neonatal EEG and the last menstrual period.

We previously reported no differences in estimates of gestational maturity between a cumulative score based on sonographic/obstetrical measurements and an EEG interpretation for healthy preterm neonates. For the present study, a rank order among 5 fetal sonographic measurements was used to estimate gestational age: head circumference, transcerebellar diameter, biparietal diameter, femur length, and abdominal circumference were compared with an electroencephalographic estimate and an arithmetic estimate of maturity (i.e., the mother's last menstrual period). A fetal sonographic study for each of 13 premature neonates (i.e., born at < 32 weeks estimated gestational age) was followed after birth by a neonatal EEG recording. EEG and sonographic estimates of maturity were assigned without knowledge of other clinical data. The mother's last menstrual period was obtained from the medical record. Principal component analysis determined that 86% of the variance was evenly distributed over the 5 sonographic measurements. Using a regression procedure, 61% of the variance (adjusted r2 = 0.61) was explained by EEG when compared with fetal sonographic estimates. Only 19% (adjusted r2 = 0.19) of the variance was explained by the estimate based on the mother's last menstrual period. Optimal subset selection determined that the rank order for prediction of gestational maturity among the fetal sonographic measurements was as follows: (1) head circumference; (2) transcerebellar diameter; (3) biparietal diameter; (4) femur length; (5) abdominal circumference. Cranial measurements on fetal sonography (i.e., head circumference, transcerebellar diameter, biparietal diameter) compared more closely with EEG estimates than non-cranial measurements (i.e., femur length and abdominal circumference). In conclusion, neonatal EEG estimates of gestational maturity compared more closely with sonographic measurements than estimates based on the time of the last menstrual period. These findings will be useful in situations when dates of conception are unknown or inaccurate, or when intrauterine growth restriction causes discrepancies in growth rates between cranial and non-cranial fetal measurements on sonography.

Postnatal adaptation of brain function in full-term neonates as assessed by EEG sleep analyses.

Differences in electroencephalographic (EEG) sleep between preterm and full-term neonatal cohorts at matched postconceptional ages have been previously presented by our study group. These differences may have occurred, however, because of postnatal brain adaptation of the full-term infant after a more recent delivery. EEG sleep analyses, therefore, were performed on only the full-term cohort to determine if EEG sleep measures changed over the first three days after birth, which might account for the differences with the preterm group. Twelve full-term infants studied on the first day of life were compared with 17 full-term infants who were studied on days of life 2 and 3. Using multivariate analysis of variance (MANOVA), comparisons were performed among 13 EEG sleep measures. No EEG sleep differences were seen between full-term children born by Cesarean section versus those born by vaginal presentation. No statistical differences were noted between day 1 compared to days 2 and 3 with respect to 10 measures concerning sleep architecture, phasic, continuity, spectral EEG, and autonomic features. In three EEG sleep measures, changes occurred between days 1 and 2-3, but two of the three measures were in a direction that strengthen our claim that differences exist between preterm and full-term cohorts: more body movements and lower percentages of quiet sleep were noted for full-term infants on days 2-3. EEG sleep differences between preterm and full-term infants at matched postconceptional term ages are more likely to be due to conditions associated with prematurity rather than postnatal brain adaptation in the full-term group who experienced a more recent delivery.

Maturational trends of EEG-sleep measures in the healthy preterm neonate.

Five physiologic groupings of 45 EEG-sleep measures were acquired from serial 24-channel EEG-sleep recordings (i.e., sleep architecture, continuity, EEG spectral, phasic, and autonomic measures), utilizing 129 studies on 56 healthy preterm infants from 28 to 43 weeks postconceptional age (PCA) who were neurodevelopmentally normal on follow-up. Regression analyses chose the least number of measures that best reflected maturation. Four of 45 variables (i.e., spectral alpha energy during quiet sleep, total spectral EEG energy, arousal number during active sleep, and percentage of EEG discontinuity) most significantly explained brain maturation in neonates < 36 weeks PCA. Three of 45 variables (i.e., spectral theta and beta energies during active sleep and spectral alpha energy during quiet sleep) were most representative after 36 weeks PCA. Spectral EEG energies were the strongest indicators of maturation compared with other measures, particularly in near-term neonates.

Maturation of phasic and continuity measures during sleep in preterm neonates.

Different physiologic measures during EEG sleep periods in preterm neonates are postulated to change with maturation and reflect functional brain development. Forty-three healthy preterm neonates received 3-h EEG sleep studies in an environmentally controlled setting. Postconceptional ages of neonates at each recording session ranged from 28 to 35 wk. Minute-by-minute analyses of EEG discontinuity, motility, arousals, and REM were performed. Eight phasic events and continuity measures of sleep were tabulated. Data were analyzed using Spearman rank order correlation coefficients. Increases in arousal numbers (p < 0.001) and durations (p < 0.001) were noted with age only during continuous periods of EEG activity (i.e. active sleep). REM also increased with corrected age during indeterminate or transitional sleep (p < 0.002) and decreased during quiet sleep (p < 0.01). Decreases in small body movements per minute (p = 0.02) and large body movements per minute (p < 0.001) occurred only during discontinuous periods of EEG activity (i.e. quiet sleep). Sleep efficiency (p < 0.001), maintenance (p < 0.001), and latency (p = 0.01) also decreased with increasing postconceptional age. Cycle length between two segments of continuous EEG with an intervening period of EEG discontinuity also lengthened with maturation (p < 0.001). These findings are discussed in the context of previously reported differences in phasic and continuity measures noted between preterm and full-term infants at matched full-term postconceptional ages. Changes in phasic and continuity measures with increasing postconceptional ages reflect maturation of specific neuronal processes of the CNS within a rudimentary sleep cycle of the preterm neonate.

Cardiorespiratory behavior during sleep in full-term and preterm neonates at comparable postconceptional term ages.

Cardiorespiratory behavior during sleep has been investigated by comparing visually analyzed minutes of EEG sleep with the digitized values of these two physiologic variables for each corresponding minute. Continuous 3-h nighttime sleep studies on 37 full-term and preterm neonates at comparable postconceptional term ages were acquired under controlled conditions, using a 24-channel computerized monitoring system and an automated event-marker program. Five thousand, two hundred ninety-four minutes were assigned an EEG state by traditional criteria. Eighteen preterm infants were compared with 19 full-term infants with respect to six cardiac and six respiratory measures: two nonspectral calculations (i.e. average per minute and variance of the means) and four spectral calculations of the cardiorespiratory signal (i.e. bandwidth, spectral edge, mean frequency, and ratio of harmonics). The relative capabilities of these measures to predict a sleep state change were investigated using discriminant analysis. A stepwise selection algorithm in discriminant analysis was used to identify the order of significance for the remaining variables. Eight cardiorespiratory measures were then submitted to multivariate analysis of variance to assess sleep state or preterm-full-term differences: mean frequency, bandwidth, average per minute, and ratio of harmonics for cardiac signals; and spectral edge, mean frequency, logarithm of variance, and ratio of harmonics for respiratory signals. Differences among the sleep states and between neonatal groups were highly significant (p < 0.0001). Interaction between sleep state and neonatal group was also significant (p < 0.034). Two variables differentiated preterm from full-term respiratory behavior: ratio (p < or = 0.001) and mean frequency (p < or = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative estimates of neonatal gestational maturity by electrographic and fetal ultrasonographic criteria.

We previously reported a high correlation between electrographic and postmortem neuroanatomic (i.e., sulcal-gyral) estimates of maturity in sick preterm neonates who were clinically abnormal because of neonatal medical illnesses. Electroencephalographic studies have not yet been compared with ultrasonographic measurements in healthy fetuses who subsequently had normal neurodevelopmental outcome. Twenty-five EEG recordings on healthy neonates (28-43 weeks postconceptional age) had EEG estimates of gestational maturity without knowledge of obstetric, neonatal, or ultrasonographic criteria. Thirteen recordings from this cohort were obtained on very premature neonates (i.e., < 32 weeks estimated gestational age). Fetal ultrasonographic determinations of gestational maturity for these 13 subjects were also obtained prior to birth. Ultrasonographic estimates were assigned without knowledge of other clinical data. Gestational age estimates based on electroencephalographic analyses were compared with 5 ultrasonographic estimates of gestational age maturity using multivariate regression (i.e., biparietal diameter, abdominal circumference, femur length, transcerebellar diameter, and head circumference), as well as the mother's last menstrual period. No significant differences were detected between the electrographic and obstetric/ultrasonographic estimates of gestational maturity. An electroencephalographer's assessment of gestational age is as accurate as the fetal ultrasonographic estimates in the asymptomatic preterm neonate whose gestational age is < 32 weeks at birth.

Rectal temperature changes during sleep state transitions in term and preterm neonates at postconceptional term ages.

Mean rectal temperatures in neonates were investigated during sleep state transitions as assessed by visually analyzed electroencephalographic-polygraphic recordings. Continuous 3-hour studies were obtained on 3 term and 5 preterm infants at postconceptional term ages using a 24-channel computerized monitoring system. In the study, 1,461 min were assigned an EEG state by traditional criteria. Mean rectal temperature measurements were tabulated for each minute of sleep. Data were analyzed both as 1,461 consecutive minutes of sleep, and as 28 complete ultradian neonatal sleep cycles. Exploratory analyses were performed using t tests, Mann-Whitney U tests, and one-way analysis of variance. Decreases in mean rectal temperatures followed a transition from active to quiet sleep for only the term group. The preterm group had higher temperatures at sleep onset than the term group and demonstrated no changes during state transitions. Higher temperatures were maintained in the preterm group during both active and quiet sleep (i.e., 36.7 degrees C versus 36.4 degrees C, P = .02) when 28 complete cycles of sleep were compared and during the transition when 658 min of active sleep were compared to 617 min of quiet sleep. These findings are preliminary; however, the phenomenon of state-dependent changes in mean rectal temperature in neonates based on electroencephalographic sleep is unreported. Higher mean rectal temperatures during active sleep and altered temperature responses during transition to quiet sleep in the preterm infant suggest altered brain function because of the preterm infant's adaptation to the extrauterine experience.

Comparisons of EEG spectral and correlation measures between healthy term and preterm infants.

Continuous 12-hour electroencephalography (EEG)-sleep studies were acquired by a computerized monitoring system under environmentally controlled conditions for 2 groups of neonates. Eighteen health preterm infants at a postconceptional term age were matched to 18 term infants. These 2 groups were also matched for gender, race, and socioeconomic class. For the entire 12-hour recording, relative spectral power values (i.e., ratio of specific EEG power in specific frequency band compared to total EEG power) were significantly reduced in the preterm group for theta (P < or = .007), alpha (P < or = .001), and beta (P < or = .018) frequency bands, while delta remained unchanged. Correlations between 91 pairs of EEG channels were also calculated and the preterm infants had significantly higher correlation values in 27 of the 91 pairs of channels (P < .05); 14 interhemispheric, 8 intrahemispheric, and 5 sagittal combinations, while 3 intrahemispheric combinations were higher in the term group. Fewer functional neuronal aggregates generate less oscillatory potential (i.e., lower spectral power) in the theta through beta frequency ranges in the preterm infant, while greater cortical connectivity (i.e., higher correlations) exists in many brain regions by postconceptional term ages in this group. These findings suggest a functional alteration in brain development of the preterm infant as a result of prolonged extrauterine experience and/or prematurity.

Positive temporal sharp waves on EEG recordings of healthy neonates: a benign pattern of dysmaturity in pre-term infants at post-conceptional term ages.

One complete sleep cycle was selected in each of ninety-four 3 h EEG recordings on 52 healthy neonates from 29 to 43 weeks CA (28 pre-term (PT)/24 full-term (FT)); 51 who are neurodevelopmentally normal up to at least 18 months of age. Each recording was reviewed to identify positive temporal sharp waves (PTS). This wave form was compared to another commonly occurring wave form, temporal theta of prematurity (PT theta). 588 PTS and 626 PT theta observations were tabulated in terms of frequency, amplitude, morphology, left:right predominance, and sleep state at 6 post-conceptional age ranges up to term. Mean PTS for FT, PT and pre-term at post-conceptional term age (PTT) infants, respectively, were 1.5 +/- 0.85, 2.8 +/- 2.5, 2.0 +/- 1.6 per sleep cycle. PTS amplitudes (microV) were 59.7 +/- 23.5, 38.2 +/- 17.8, and 51.8 +/- 29.3. The peak incidence of PTS occurs at older post-conceptional ages than PT theta (r = 0.21, P = 0.0001). PTT infants had more PTS (chi 2 = 32.5, P = 0.001) than FT infants. Similar numbers and descriptions of PT theta were noted between neonatal groups at post-conceptional term ages. While pathological PTS waves have been described in FT neonates and infants (Chung and Clancy: Electroenceph. clin. Neurophysiol., 1991, 79: 256-263), benign PTS waves are also present on recordings of healthy pre-term and full-term neonates. PTS are electrographically similar to PT theta, but are more abundant at older post-conceptional ages in pre-term infants than full-term infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological significance of sharp wave transients on EEG recordings of healthy pre-term and full-term neonates.

One EEG sleep cycle was selected from each of ninety-four 3 h studies on 52 healthy neonates from 29 to 43 weeks post-conceptional ages (CA) (28 pre-term (PT)/24 full-term infants (FT); 51 are normal up to at least 18 months of age). Each record was reviewed to identify sharp wave transients (SWTs). No spike discharges were noted. 364 SWTs were tabulated in terms of amplitude, morphology, left:right predominance, anatomical site and EEG sleep state. Mean number of SWTs per hour for full-term, pre-term, and pre-term at post-conceptional term age (PTT) infants were 11.7 (+/- 12), 10.0 (+/- 7), and 13 (+/- 10). Mean amplitudes (microV) were 98.8 (+/- 23.2), 84.9 (+/- 38.3), and 99.4 (+/- 28.8) for FT, PT, and PTT infants respectively. FP1, FP2, T4 and C3 accounted for 94%, 83% and 84% of SWT sites for FT, PT and PTT groups, respectively. Biphasic waves were noted more frequently, and triphasic waves almost exclusively in PT infants (chi 2 = 130.8, P = 0.001). Spearman correlations were significant for amplitude of SWTs with CA (and r = 0.45, P = 0.0001). Significant differences (ANOVA) were found, for instance, between SWT frequency with the site and sleep state (R2 = 0.63, P = 0.0001) between SWT amplitude with sleep state and morphology (R2 = 0.59, P = 0.0001). Brain maturation alters the location and morphology of SWTs in healthy neonates. Descriptions of SWTs on EEG recordings of healthy neonates will improve the assessment of encephalopathic recordings of infants studied for clinical reasons.

Comparisons of EEG sleep state-specific spectral values between healthy full-term and preterm infants at comparable postconceptional ages.

Differences in state-specific electroencephalographic (EEG) spectral values are described between groups of preterm and full-term neonates at comparable postconceptional term ages. Eighteen healthy preterm neonates of < or = 32 weeks gestation were selected from an inborn population of a neonatal intensive care unit. Twenty-four-channel recordings were obtained at a full-term age and compared with studies of 22 healthy full-term neonates. The initial three hours of each 12-hour study were recorded on paper from which EEG sleep state scores per minute were visually assessed. Six mean spectral values (i.e. total EEG, electromyogram, delta, theta, alpha and beta energies) were calculated from each corresponding minute of digitized data, which was also assigned one of six EEG sleep states. Each neonatal group displayed statistically significant differences among sleep-state segments for all spectral values. The alpha- and beta-range spectral values of the preterm group, compared to the full-term control group, were lower during all sleep state segments. Spectral values for the theta band were lower during both quiet sleep segments only, whereas spectral values for delta were lower during all sleep stages, except tracé-alternant quiet sleep. Significant differences in EEG spectral values were noted among states of sleep for both preterm and full-term infants of similar postconceptional term ages. These data also suggest differences in central nervous system maturation between neonatal populations. These findings strengthen our previously stated contention that there is a functional alteration in brain development of the preterm infant as reflected in sleep organization that results from a prolonged extrauterine experience and/or prematurity.

Ictal and interictal electrographic seizure durations in preterm and term neonates.

The effect of gestational age on neonatal ictal and interictal durations has not been investigated. Sixty-eight neonates with 644 electrographic seizures were identified retrospectively. Thirty-five full-term (FT) neonates were compared with 33 preterm (PT) neonates. Eighteen older preterm infants (OPT) [> 31 weeks estimated gestational age (EGA)] were also compared with 15 young preterm infants (YPT) of < or = 31 weeks EGA. Ictal/interictal durations were calculated for the total cohort with and without status epilepticus (SE). Statistical analyses were two-tailed t tests, chi-square calculations, and one-way analysis of variance (ANOVA) with Duncan's multiple-range test. Eleven of 35 (33%) FT had SE as compared with 3 of 33 (9%) PT (chi-square = 7.8, p < 0.05). The mean ictal duration was 14.2 min for FT infants as compared with 3.1 min for PT infants (p < 0.01); only borderline differences were noted after those with SE were excluded. Interictal durations were longer for OPT than YPT (p < 0.05). By ANOVA and Duncan's multiple-range tests, group differences included longer mean ictal durations for FT infants as compared with OPT infants (p = 0.06, ANOVA; p < 0.05, Duncan's), and longer mean interictal durations for FT infants versus OPT and OPT versus YPT (p = 0.02, ANOVA; p < 0.05, Duncan's). More developed neuronal networks result in longer ictal durations in FT than in PT neonates, including FT infants with SE.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrographic seizures in preterm and full-term neonates: clinical correlates, associated brain lesions, and risk for neurologic sequelae.

Electrographically confirmed seizures in preterm and term neonates were compared with respect to clinical correlates, incidence, associated brain lesions, and risk for neurologic sequelae. Over a 4-year period, 92 neonates from a neonatal intensive care unit population of 4020 admissions at a large obstetric hospital with 40,845 livebirths had electrographically confirmed seizures. Sixty-two neonates were preterm and 30 were full-term for gestational age. Chi-square calculations were used to compare the two groups. While the incidence of seizures for all neonates admitted to a neonatal intensive care unit was 2.3%, outborn neonates were more likely to have seizures than inborn neonates. Preterm neonates of < or = 30 weeks gestational age had a seizure frequency of 3.9%, which was significantly higher than that of older preterm neonates and full-term neonates. Clinical criteria contemporaneous with electrographic seizures were noted in only 28 (45%) of 62 preterm, and 16 (53%) of 30 full-term neonates. Subtle seizures coincident with electrographically confirmed seizures were the most predominant clinical type for both term and preterm neonates (71% and 68%, respectively). The distribution of clonic, myoclonic, and tonic seizures was also similar for both groups. Autonomic signs coincident with electrographically confirmed seizures (ie, blood pressure, heart rate, oxygenation, respiration changes) were more frequently observed in preterm than full-term neonates with subtle seizures; 7 (37%) of 19 compared with 1 (6%) of 16. Electrical seizures without clinical correlates were noted more frequently than electroclinical seizures for both populations.(ABSTRACT TRUNCATED AT 250 WORDS)