F De Carli

Regional cerebral blood flow in chronic hypertension. A correlative study.

BACKGROUND AND PURPOSE Cerebral hypoperfusion has occasionally been reported during essential hypertension. We explored regional cerebral blood flow in a large series of neurologically asymptomatic hypertensive patients to determine relations among cerebral blood flow, concomitant main vascular risk factors, and the most common signs of end-organ damage. METHODS Regional cerebral blood flow was measured by the 133Xe inhalation method in 101 hypertensive patients without clinically apparent central nervous system involvement, including 39 mild to moderate untreated and 62 mild to severe treated patients. RESULTS Compared with age- and sex-matched normal control subjects, cerebral blood flow was significantly reduced in untreated hypertensive patients (P < .01) and to a lesser extent in treated patients (P = .047). Both regional and global cerebral blood flow reductions were observed in approximately one third of patients in both groups. Analysis of variance failed to show significant correlations between cerebral blood flow and total cholesterol concentration, mean arterial blood pressure, duration of disease, or the presence of retinopathy or left ventricular hypertrophy. In the treated group, the quality of control of hypertension significantly influenced both global cerebral blood flow (P = .007) and cerebrovascular resistance (P < .0001). CONCLUSIONS Focal or diffuse cerebral hypoperfusion is present even in neurologically asymptomatic hypertensive patients, especially when untreated; good control of blood pressure may preserve cerebral perfusion and reduce cerebrovascular resistance. Regional cerebral blood flow examination represents a relatively simple and low-cost technique to explore the perfusional condition of the brain, one of the main target organs of hypertensive disease.

Relationship of sleep interictal epileptiform discharges to sigma activity (12–16 Hz) in benign epilepsy of childhood with rolandic spikes

OBJECTIVE The activation of interictal epileptic discharges (IEDs) by NREM sleep is a well-known phenomenon in benign epilepsy of childhood with rolandic spikes (BECRS). The activating properties of NREM sleep on IEDs have been attributed to increased synchronization within thalamocortical neurons. During NREM sleep two synchronizing mechanisms lead to the appearance of spindles and delta waves on the EEG. Spectral analysis technique is a suitable method that can be used to quantitatively describe the dynamics of delta (slow wave activity (SWA) 0.5-4.0 Hz) and sigma activity (12.0-16.0 Hz) during sleep. METHODS In order to define more accurately the relationship between synchronizing mechanisms (spindles and delta activities) and IEDs during sleep in BECRS, we have performed overnight continuous EEG polysomnography studies in 9 patients (mean age 7.4 +/- 2.5 years). The temporal series of SWA and sigma values, derived from spectral analysis, have been obtained from a spike-free derivation lead. The IEDs count has been performed on the most active lead. Relationships between sigma and SWA and time series of IEDs were tested by means of correlation techniques after data normalization. RESULTS Our results revealed a significant higher correlation between IEDs and sigma activity with respect to SWA in all the subjects, in total sleep time. The same analysis limited to NREM sleep highlights the better correlation between sigma and IEDs. CONCLUSIONS Data suggest that during sleep of BECRS patients, IEDs are more sensitive to the promoting action of the spindle-generating mechanism than to the SWA-producing one.

Modulation of sleep interictal epileptiform discharges in partial epilepsy of childhood

OBJECTIVE NREM sleep increases the Interictal Epileptic Discharges (IEDs) in the majority of children affected by partial epilepsy (both symptomatic or cryptogenetic). Experimental data revealed that the normal sleep oscillations, leading to the appearance of spindles and delta waves on the surface EEG during NREM sleep, might develop into paroxysmal synchronization. Spectral analysis enables the quantitative description of the dynamics of delta (slow wave activity, SWA, 0,5-4,5 Hz) and sigma activity (SA, 12.0-16.0 Hz) and can be used to assess the relationship between SA, SWA and IEDs during sleep. DESIGN AND METHODS We have performed overnight continuous EEG-polysomnographic studies in 7 patients (mean age 7.2+/-1.3). The temporal series of SWA and SA were obtained from a spike-free derivation lead. The IEDs count was performed on the most active lead. Relationships between sigma and SWA and time series of IEDs were tested by means of correlation techniques after data normalization. RESULTS Our results revealed a significant higher correlation between IEDs and SA with respect to SWA in all the subjects, in total sleep time. The same analysis limited to NREM sleep highlights the better correlation between SA and IEDs. CONCLUSIONS Our data suggest that the neural mechanisms involved in the generation of sleep spindles facilitate the IEDs production in childhood partial epilepsies at least in those strongly activated by sleep.

Sleep-EEG modulation of interictal epileptiform discharges in adult partial epilepsy: a spectral analysis study

INTRODUCTION In order to define accurately the relationship between EEG components (spindles, delta and theta frequencies) and the occurrence of interictal epileptiform discharges (IED) during sleep in partial epilepsy, a correlation study between spike overnight distribution and EEG spectral power time series was performed. METHODS Eighteen patients (mean age: 24.7+/-5.5 years) affected by partial epilepsy underwent continuous EEG-polysomnography. The temporal series of Slow Wave Activity (SWA), Sigma Activity (SA) and Theta Band (TB), derived from spectral analysis, were obtained from a spike-free and pathologic alteration-free derivation, contralateral to the most active lead, where the IED count was performed. Relationships between SA, SWA and TB and time series of IED were tested by means of correlation techniques after data normalization. RESULTS Our results revealed a significantly higher correlation between IED and SWA in 12 subjects; a significantly higher correlation between IED and SA in three subjects and a significant correlation with TB in three cases. CONCLUSIONS Data suggest that in most adult patients with partial epilepsy IED production during sleep is facilitated by the action of synchronizing mechanisms which are active during NREM sleep and lead to the appearance of EEG delta waves. Nevertheless evidence is given of two smaller groups of patients. In one of them IED are more sensitive to the promoting action of the spindle generating mechanism, active during stage 2 of NREM sleep. In the other one the promoting action of TB, characterizing EEG during stage 1 and REM sleep, is evident.

A quantified analysis of sleep electroencephalography in anorectic adolescents

BACKGROUND Previous studies on sleep characteristics in anorexia nervosa have led to controversial results. This may be due to either the heterogeneity of the samples studied or to an intrinsic inadequacy of the scoring criteria. To obtain a more detailed analysis we have investigated sleep characteristics in a group of adolescents affected by anorexia nervosa using spectral analysis techniques. METHODS After a baseline night, the sleep-electroencephalograms of 10 adolescent anorectic girls (age +/- SD = 14 +/- 2 years) and 10 age-matched control subjects were recorded and processed by a fast Fourier transformation routine. RESULTS Anorectics showed an increased number of awakenings and wakefulness after sleep onset and a reduction of sleep efficiency and slow-wave sleep. Spectral analysis results revealed a significant reduction in the power spectral values of slow-wave activity (SWA; 0.5-4.5 Hz) band in all NREM-REM cycles of sleep and in the undisturbed and stable stage 4. Moreover the anorectic group was characterized by a concentration of SWA in the first NREM-REM cycle with an abrupt decay in the second part of the night. A positive correlation (r2 = .58, p < .01) between body mass index and the amount of SWA was found. CONCLUSIONS Sleep of anorectic patients seems to be characterized by a weakness of SWA producing mechanisms. The positive correlation between body mass index and the amount of SWA appears to be consistent with the neurobiological consequences of the malnutrition state.

Distribution of epileptiform discharges during nREM sleep in the CSWSS syndrome: relationship with sigma and delta activities

PURPOSE The EEG pattern of epilepsy with continuous spike-waves during slow wave sleep (CSWSS) is characterized by an almost continuous activation of spike-and-slow-wave complexes during nREM sleep with a marked reduction of EEG abnormalities during REM sleep and the awake state. Experimental studies indicate that normal sleep oscillations that during nREM sleep lead to the appearance of spindles and delta waves on scalp EEG might develop into paroxysmal synchronization. Spectral analysis enables the quantitative description of the dynamics of delta (Delta Activity, DA, 0.5-4.5 Hz) and sigma activity (SA, 12-16 Hz) and can be used to assess the relationship between SA, DA and epileptiform discharges (EDs) during sleep. METHODS We analyzed the EDs distribution during sleep in five children affected by CSWSS. We used a model of the evolution of power of DA and SA to which the time series of EDs could be fitted. RESULTS We found a high and positive correlation between EDs and SA. DA resulted negatively correlated with EDs. CONCLUSION Our data suggest that neural mechanisms involved in the generation of sleep spindles facilitate EDs production in the CSWSS syndrome. Such a mechanism seems to be an age related phenomenon shared by other epileptic syndromes of childhood.

Spindles-Inducing Mechanism Modulates Sleep Activation of Interictal Epileptiform Discharges in the Landau-Kleffner Syndrome

Summary: Purpose: Landau–Kleffner syndrome (LKS) is characterized by a marked increase of interictal epileptiform discharges (IEDs) during sleep. During nonrapid eye movement (NREM) sleep, neuronal membrane potential oscillations lead to the appearance of spindles and delta waves in the surface EEG and might develop into paroxysmal synchronization. Spectral analysis allows the quantitative description of the dynamics of delta (slow‐wave activity, SWA, 0.5‐4.5 Hz) and sigma activity (SA, 12.0–16.0 Hz) and can be used to assess the relation between SA, SWA, and IEDs during sleep.

Regional cerebral blood flow in chronic stroke patients.

Background and Purpose The aim of this study was to investigate regional cerebral blood flow parameters during the postacute phase of unilateral ischemic stroke and to correlate them with clinical data. Methods Regional cerebral blood flow was measured in 187 patients in the stabilized phase of stroke by the xenon-133 inhalation method with 32 extracranial detectors. Thirty-eight patients were reexamined after a mean ± D time of 32 ± 21.4 months. Results The overall detection of hypoperfusion was 92.0%, with asymmetries as the most sensitive index, especially for patients with a lesser degree of neurological disability. Neurological disability score was strongly associated with regional cerebral blood flow in the affected hemisphere (p<0.0001) and with asymmetries (p<0.0001). The presence of carotid obstruction further decreased the regional cerebral blood flow in the affected hemisphere and significantly increased asymmetry (p< 0.0001). Subjects who had no hypoperfusion at absolute values analysis were more frequently free of carotid disease and had less severe disability than those who had bilateral or unilateral regional absolute cerebral blood flow reduction. In 38 patients without new cerebrovascular events, a significant (p=0.005) reduction of hemispheric regional cerebral blood flow asymmetries was found on a follow-up examination. Conclusions These data confirm the value of regional cerebral blood flow asymmetries in stroke detection and point out that important clinical information is also contained in absolute values analysis.

Relationship of sigma activity to sleep interictal epileptic discharges: a study in children affected by benign epilepsy with occipital paroxysms.

INTRODUCTION By applying spectral analysis techniques we recently showed that Interictal Epileptic Discharges (IEDs) are modulated by sleep spindle synchronization mechanisms (sigma activity, SA, 12. 0-16.0 Hz). This finding applies to both benign epilepsy of childhood with rolandic spikes (BECRS), to symptomatic epilepsy of childhood strongly activated by sleep and to the Landau-Kleffner syndrome. These results are quite different from those found in adult partial epileptic patients where slow wave activity (SWA, 0. 5-4.5 Hz) plays the main role in the modulation of IEDs during sleep. This finding could suggest that the activation of IEDs by spindle activities could be an age-related feature of epilepsy. In order to verify this hypothesis we studied a group of epileptic children performing a polysomnographic study on five patients with BEOP strongly activated by sleep. METHODS We performed overnight continuous EEG-polysomnographic studies in five patients (mean age 6. 0+/-2.5). The IEDs count was performed on the most active occipital lead. The temporal series of SWA and SA values, derived from spectral analysis, were obtained from a spike-free central, controlateral lead. Relationships between SA, SWA and time series of IEDs were tested by means of correlation techniques after data normalization. RESULTS Our results revealed a significantly higher correlation between IEDs and SA with respect to SWA in all subjects, in total sleep time. When the analysis was limited only to NREM sleep the correlation between sigma and IEDs was even more impressive. CONCLUSIONS Data suggest that also in BEOP the spindle generating mechanism modulates the IEDs during sleep. This mechanism seems to be an age-dependent phenomenon with no relation whatsoever either with the type of epilepsy or with the brain region.

Evaluation of cerebral blood flow data in stroke patients using a mapping system.

We retrospectively examined regional cerebral blood flow values in 78 patients in the stabilized phase of stroke to evaluate the consistency of lateralization compared with computed tomographic imaging. Examinations were performed using the xenon-133 inhalation technique, and the data were processed and displayed by a computer-assisted system of our own design that allows statistical analysis in real time and is suitable for clinical use. The consistency of lateralization correlated with computed tomographic findings was tested for absolute values, percent distribution, and asymmetries. The latter yielded the highest degree of sensitivity (in 83.3% of the patients the affected hemisphere was correctly identified). Absolute values showed at least one hypoperfused area in the affected hemisphere in 48.7% of the patients, and percent distribution did so in 57.7%. Furthermore, the combination of the three methods of data analysis yielded a sensitivity of 91%; the remaining 9% of the patients, however, exhibited some abnormalities of regional cerebral blood flow (bilateral or contralateral hypoperfusion). Although good agreement was found for lateralization by computed tomography and by the combined use of the three methods of analysis, a complete overlap between functional and structural examinations should not be expected. Problems concerning the sensitivity of the xenon-133 inhalation technique under conditions of low blood flow and the statistical analysis of regional cerebral blood flow data are discussed.