G. Rosadini

Dynamics of slow wave activity in narcoleptic patients under bed rest conditions

Following a baseline night recording, 9 narcoleptic subjects and 9 sex- and age-matched control subjects were maintained on 16 h of diurnal sleep deprivation. Thereafter subjects were submitted to a 32 h bed rest protocol in a sound- and light-attenuated room. The EEG was recorded and processed by a Fast Fourier Transform. Narcoleptics did not differ from controls in total sleep time over the whole 32 h, but spent more time sleeping during the daytime (DT). In both groups slow wave activity (SWA) showed an exponential decaying trend during the first night (N1); a similar exponential trend during the second night (N2) was evident only in controls. In controls SWA showed a circadian-circasemidian distribution that was hardly detectable in nacroleptics. Narcoleptics showed an ultradian distribution of SWA with periodic emergence every 4 h during DT and N2. Our data confirm that a homeostatic mechanism is evident in narcolpetics when stimulated by diurnal sleep deprivation, while circadian and circasemidian mechanisms are less evident during DT and N2. These findings suggest a different coupling between homeostatic sleep regulating and circadian drives to sleep in narcoleptics. Ultradian drives to sleep seem to be predominant in these patients, thus probably acting as a means for the avoidance of stressful attempts to counteract a weaker waking state maintenance mechanism.

Reduction of Cerebral Blood Flow in Subclinical Hepatic Encephalopathy and its Correlation with Plasma-Free Tryptophan

Cerebral blood flow (CBF), measured by the noninvasive xenon-133 inhalation method, EEG, and plasma levels of ammonia (NH3) and free tryptophan were determined in 18 hospitalized cirrhotic patients affected with subclinical hepatic encephalopathy, as diagnosed by the Kurtz test. CBF results were significantly lower (p < 0.001) in the patients group as compared with a sex- and age-matched normal control population, although seven patients had values in the normal range. NH3 was increased only in six, while free tryptophan was increased in all but two patients. A significant negative correlation (p = 0.02) between CBF and free tryptophan was found, even though it appears to be difficult to interpret. We suggest that CBF impairment in some cirrhotic patients with subclinical hepatic encephalopathy may be related to the systemic metabolic derangement caused by the liver disease; free tryptophan could have some implication in producing CBF reduction.

Human flash-VEP and quantitative EEG are independently affected by acute scopolamine

Scopolamine in acute intramuscular doses of 0.25-0.75 mg reduced the P2-N3 flash-VEP amplitude and, in the quantitative EEG, the 8.5-12.0 Hz power and total power in 8 healthy young male volunteers. The effects on flash-VEP and EEG total power were dose dependent and were evident 30 min and 90 min respectively after drug administration, regardless of dose. The reduction in 8.5-12.0 Hz power was limited to the 0.50 and 0.75 mg doses. No systematic effects on the pattern-VEP were observed. Possible interferences with flash- or pattern-VEP amplitude of the scopolamine-induced EEG changes were identified and removed by regression analysis and computation of VEP residuals from the regression function. The P2-N3 flash-VEP residuals proved EEG independent and showed relationships with dose and time after drug administration that were superimposable on those of the original data, with comparable significance levels at the drug/placebo and pre/postdrug statistical comparisons. The results indicate that VEP estimates of drug effects which are independent from EEG changes can be identified in human studies and allow some inference on the cholinergic specificity of the systems affecting late flash-VEP components. The statistical approach used in this study is suitable for application in VEP studies when effects of interacting factors are to be expected.

Visual evoked potentials as recorded from the scalp and from the visual cortex before and after surgical removal of the occipital pole in man.

Abstract In an epileptic patient who had to undergo surgical ablation of the occipital pole, a comparison was made: (1) between the averaged visual evoked response recorded from the scalp and the response recorded directly from the visual cortex, and (2) between scalp responses recorded before and after surgical removal of the occipital pole. The scalp recorded response was satisfactorily similar to that recorded from the visual cortex, provided that spatial arrangement of the electrodes was similar. The ablation of the occipital pole did not affect the initial components of the response (having peak latencies below 45 msec) or the late components (peak latencies over 120 msec), but greatly reduced the amplitude of the waves with peak latencies between 50 and 110 msec.

Excitability cycle of the visual cortex during sleep and wakefulness.

Resume Les auteurs etudient le cycle dexcitabilite du cortex visuel chez le chat intact non anesthesie, au cours des etats de veille, de sommeil avec synchronisation EEG et de sommeil avec desynchronisation EEG. Ils procedent a lanalyse des amplitudes relatives des deux potentials evoques dans laire corticale visuelle par deux stimulations identiques appliquees aux radiations optiques et separees par des intervalles de temps variables. Lexcitabilite des neurones du cortex visuel est plus eleee au cours du sommeil que pendant letat de veille; il na pas ete trouve de differences significatives entre les deux phases de sommeil. Les auteurs tentent dinterpreter ce phenomene en emettant lhypothese que durant le sommeil le cortex cerebral est libere dune influence inhibitrice exercee par le systeme reticulaire activateur. Les fluctuations de lexcitabilite corticale pendent le sommeil synchronise pourraient etre dues a lactivite oscillante des circuits de synchronisation thalamo-corticaux; sa stabilite relative pendant le sommeil desynchronise pourrait etre attribuee a une influence ascendante hypnogene du tronc cerebral. Des aires corticales differentes pourraient montrer des modifications differentes dexcitabilite au cours du sommeil et de la veille; les changements dexcitabilite du thalamus paraissent differer en partie de ceux du cortex cerebral.

Relations between threshold of arousal and electroencephalographic patterns during sleep in man

Abstract The depth of sleep was evaluated in human subjects by studying the intensity of painful electric stimuli to the skin necessary to produce arousal (study of the threshold of arousal). The threshold of arousal was definitely lower during the phase 1 of sleep than during the other phases. No significant difference between sleep with slow electroencephalographic waves and sleep with fast, low amplitude electroencephalographic activity and rapid eye movements was found. In this respect there is a striking difference from what occurs in the cat.

Ultradian aspects of sleep in narcolepsy

Following a baseline night recording, 9 narcoleptic subjects and 9 sex and age-matched control subjects were maintained on 16 hours of diurnal sleep deprivation. Thereafter subjects were submitted to a 32 hour bed rest protocol in a sound-light attenuated room. The EEG was recorded and processed using a Fast Fourier Transform. Narcoleptic patients did not differ from control subjects in total sleep time over the whole time-span. An ultradian tendency to sleep seems to be predominant in narcoleptic patients and evidence of a strong basic rest activity cycle is shown. The coupling between the homeostatic process of sleep regulation and an ultradian drive to sleep would explain the peculiar 4 hour distribution pattern of SWA in narcoleptic patients.

Quantitative EEG and Neuropsychological Effects of Piracetam and of the Association Piracetam-Lecithin in Healthy Volunteers

The electroencephalographic (EEG) and neuropsychological effects of single, oral doses or piracetam (800-6,400 mg) and of its association with lecithin (4,800 mg and 25 g, respectively) were investigated in two groups of healthy volunteers in placebo-controlled studies. The EEG was quantified by power spectral analysis; both parametric and nonparametric procedures were applied to process the EEG and neuropsychological data statistically. The drug plasma concentration was assessed (gas chromatography) in concomitance with the EEG and neuropsychological measurements. Piracetam was found to elicit systematic EEG effects, namely a decrease in the low-frequency components and an increase in the power of the 8.5- to 12.0-Hz and of the fast-frequency components. The EEG modifications were restricted to the anterior scalp areas; its detection by means of parametric statistics was conditioned by the relevant individual variability and was inferred resting upon a number of criteria (indication at nonparametric tests, topography, consistency across subjects, replicability, etc). The correlation between EEG changes and drug plasma concentration was ambiguous, and the compound was not found to be effective on any of the neuropsychological variables considered. The study exemplifies some of the methodological problems in quantitative pharmaco-EEG and emphasizes the relevance of topography and replication.

Neurosurgical aspects of epilepsy: Physiological sleep as a means for focalizing EEG epileptic discharges

SummaryThe EEGs of a group of epileptic patients with no clear signs of lateralization either in the clinical history and examination, the clinical seizure pattern, the radiological examinations, or the repeated standard EEG recordings, were registered during nocturnal physiological sleep. The appearance of clearcut focal epileptic discharges was observed during sleep in most of the patients who when awake had normal EEG or bilateral inconstantly synchronous abnormalities; no focal abnormality was found in patients showing bilateral constantly synchronous convulsive discharges during wakefulness. The possible application of these findings in the selection of patients for surgical treatment of their epilepsy is discussed.ZusammenfassungBei einer Gruppe von epileptischen Patienten, die weder im klinischen Verlauf und Befund, im klinischen Ablauf der Anfälle, den Röntgenbefunden, noch bei wiederholten EEG-Standard-Ableitungen eindeutige Seitenhinweise gefunden werden konnten, wurde das EEG während des nächtlichen physiologischen Schlafes abgeleitet. Das Auftreten eindeutiger fokaler epileptischer Entladungen wurde während des Schlafes bei den meisten derjenigen Patienten beobachtet, bei denen im wachen Zustand ein. normales EEG oder bilaterale inkonstante synchrone pathologische Befunde gefunden worden waren. Keine fokalen Veränderungen fanden sich bei solchen Patienten, die konstant bilaterale synchrone Krampfstromabläufe im wachen Zustand aufwiegen. Die Möglichkeit der Anwendung dieser Befunde bei der Auswahl der Patienten für die chirurgische Therapie ihrer Epilepsie wird besprochen.RésuméChez un groupe dépileptiques ne présentant pas de signe de latéralisation, ni dans lhistoire clinique, ni à lexamen, ni au cours de crise, ni à lexamen radiologique, ni aux E.E.G. standards répétés, on fait des E.E.G. sous sommeil physiologique nocturne. Lapparition de foyer de décharges épileptiques est observée pendant le sommeil chez beaucoup de malades qui ont eu des E.E.G. normaux à létat de veille ou des E.E.G. avec des anomalies synchronisées bilatérales inconstantes. Aucun foyer anormal nest trouvé chez des malades ayant continuellement des décharges synchronisées bilatérales à létat de veille. Lapplication possible de ces découvertes dans la sélection des malades pour un traitement chirurgical de leur épilepsie est discutée.RiassuntoRegistrazioni EEG durante il sonno fisiologico notturno sono state eseguite in pazienti epilettici che non mostravano alcun segno di lateralizzazione nellanamnesi, crisi clinica, esami radiologiei e ripetuti esami EEG standard. Nella maggior parte dei pazienti con EEG normale o con alterazioni diffuse asincrone durante la veglia é stata osservata durante il sonno la eomparsa di scariche epilettiche chiaramente focalizzate; nei pazienti con scariche convulsive bilaterali e sincrone durante la veglia il sonno non ha rivelato alcuna focalizzazione. La possibile utilizzazione di questi risultati per lindicazione alla terapia chirurgica dellepilessia viene discussa.ResumenEn un grupo de epilépticos que no presentaban signos de lateralización en la historia clínica, en la exploración, en las crisis, en el examen radiológico ni en los E.E.G. standard repetidos se ha hecho un estudio E.E.G. bajo sueño fisiológico nocturno. En muchos enfermos se observó durante el sueño la aparición de un foco de descargas epileptógenas, estos enfermos tenian un E.E.G. normal en estado despierto ó con anomalías bilaterales sincronizadas inconstantes. Se discute la posible aplicación de estos hallazgos para la selección de enfermos susceptibles de un tratamiento quirúrgico para la epilepsía.

Akinetic mutism following cranio-cerebral trauma. Physiopathological considerations based on sleep studies

SummarySleep patterns has been studied in patients in akinetic mutism due to head injury.Completely organized sleep patterns occurred in 7 patients. Well organized sleep patterns, which lacked only the sleep phase with “desynchronized” EEG and rapid eye movements, were observed in 2 cases. Some atypical sleep-like EEG manifestations were recorded twice. Finally, no sign of sleep could be found in 3 patients.Some correlation between sleep patterns and the clinical course of the akinetic mutism was apparent: well organized sleep patterns were frequently followed by favourable clinical progress and viceversa.An attempt has been made to interpret the characteristics of the brain damage in the different cases observed by relating the type of sleep organization with what is known of the neurophysiological mechanisms of sleep itself.ZusammenfassungBei Patienten mit akinetischem Mutismus als Folge von Schädelverletzungen wurden Untersuchungen der Schlafstrukturen durchgeführt.Ein vollständig physiologisches Schlafverhalten war bei 7 Patienten festzustellen. Bei 2 Fällen fand sich eine gute Schlaforganisation, aber mit Fehlen derjenigen Schlafphase, die durch eine Desynchronisation des EEG und durch rasche Augenbewegungen charakterisiert ist. Zweimal wurden atypische schlafähnliche EEG-Veränderungen registriert. Bei 3 Patienten schließlich konnten keine Zeichen von Schlaf gefunden werden.Es ließen sich gewisse Korrelationen zwischen dem Schlafverhalten und der Entwicklung des akinetischen Mutismus aufzeigen: Einem guten Grad von Schlaforganisation folgte häufig eine günstige Entwicklung des Krankheitsbildes und umgekehrt.Es wurde der Versuch unternommen, die Charakteristika des Hirnschadens bei den verschiedenen beobachteten Fällen unter Berücksichtigung der Arten der Schlaforganisation und der bisherigen Erkenntnisse der neurophysiologischen Mechanismen des Schlafes zu interpretieren.RésuméOn a étudié la structure électroencéphalographique du sommeil chez des patients présentant un mutisme akinétique à la suite dun traumatisme crânio-cérébral.Sept patients présentaient des tracés typiques de sommeil.Chez deux patients, les tracés montraient une bonne organisation de sommeil; la phase de sommeil disparaissait avec les mouvements rapides des yeux, lE.E.G. montrant alors une désynchronisation. Deux patients avaient des tracés atypiques de sommeil. Chez trois autres, il ny avait aucune évidence électroencéphalographique de sommeil.Il semblait exister une certaine relation entre le tracé de sommeil obtenu et lévolution du mutisme akinétique; chez les patients qui présentèrent un tracé de sommeil, lévolution était favorable et vice-versa.A la lumière des connaissances actuelles des mécanismes neurophysiologiques du sommeil, et à lanalyse des tracés obtenus, les auteurs tentent dinterpréter les caractéristiques des lésions cérébrales.RiassuntoLa stmttura del sonno é stata studiata in pazienti in mutismo acinetico conseguente a trauma cranico.Quadri di sonno completamente strutturati sono stati osservati in 7 casi. Una buona organizzazione del sonno, mancante tuttavia della fase di sonno con EEG «desincronizzato» e movimenti oculari rapidi, era presente in 2 casi. Qualche atipica manifestazione EEG di sonno é stata registrata in 2 casi. Infine, nessun segno di sonno é stato riscontrato in 3 casi.Viene messo in evidenza un certo rapporto tra quadro di sonno ed evoluzione del mutismo acinetico: una buona organizzazione del sonno é frequentemente seguita da unevoluzione favorevole e viceversa.Unipotetica interpretatione delle caratteristiche del danno encefalico nei differenti casi osservati viene avanzata mettendo in rapporto il tipo di quadro di sonno con quanto é noto sui meccanismi neurofisiologici del sonno stesso.ResumenLa estructura del sueño ha sido estudiada en pacientes con mutismo aquinético debido a traumas craneales.En 7 enfermos se observaba un sueño tipico organizado. Un sueño profundo pero con carencia de él en algunas fases con EEG desincronizado y mivimientos rápidos de los ojos pudo observarse en 2 casos. Algún sueño atípico con manifestaciones electroencefalográficas se registró dos veces. Por ultimo signos de insomio fueron registrados en 3 pacientes.Una cierta correlación entre los patrones tipo de sueño y su evolución hacia el mutismo aquinético era evidente: un buen grado de organizatión del sueño era frecuentemente seguida por una evolución favorable y viceversa.Se ha hecho un intento de interpretatión de las caracteristicas de la afectación cerebral en los diferentes casos en relatión con el tipo de sueño con lo que se conoce en los mecanismos neurofisiológicos como el sueño propiamente dicho.