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BACKGROUND Figures for the prevalence of sleep apnoea syndrome range from 0.3% to 8.5%. These widely ranged estimates are probably due to differences in the definitions used, study designs, and study populations. A study was undertaken to determine the lower limit of the prevalence of clinically significant sleep apnoea syndrome. METHODS A cross sectional survey by postal questionnaire was carried out in a general practice of a small town in which three doctors serve 93% of its population of 6747 inhabitants of all ages. All men aged 35 and over and women aged 50 and over were invited to fill in a specially designed questionnaire on snoring and sleep. All men and women whose answers suggested the possible occurrence of sleep apnoea were invited to undergo further investigation. Oronasal thermistry was performed in the subjects’ homes and the results were scored to provide an apnoea index (AI). Those subjects with an AI of ⩾5 were referred to a sleep laboratory for investigation by polysomnography. RESULTS Of the 2466 questionnaires issued, 2182 (88.5%) were completed and returned. The occurrence during the previous three months of regular snoring, together with daytime sleepiness and/or partners’ observation of interruptions in breathing at night, was reported by 194 subjects (169 men, 25 women). In 173 subjects oronasal thermistry applied in their homes provided satisfactory recordings and, of these, 24 men and one woman had an AI of ⩾5. Analysis of the polysomnographic findings showed that 14 men and one woman met the criteria for sleep apnoea syndrome. Scrutiny of their case records disclosed that in seven men this was clinically significant. CONCLUSIONS Our findings suggest that the prevalence of clinically significant sleep apnoea syndrome in men aged 35 and over is at least 0.45%. Extrapolation to the population of the Netherlands suggests that at least 16 000 men suffer from sleep apnoea syndrome that should be relieved by medical care. A large proportion of these subjects remains to be diagnosed.

Background and objective quantitative electroencephalographic parameters and saccadic eye movements are frequently used as pharmacodynamic measures of benzodiazepine effect. We investigated the relationship between these measures and the hypnotic effect. Methods The correlation between the pharmacodynamic measures and sleep quality was determined in 21 patients with primary insomnia. The pharmacokinetic-pharmacodynamic relationships were characterized after administration of 20 mg oral temazepam. The hypnotic effect was determined on the basis of polysomnographic sleep recordings and a subjective sleep evaluation questionnaire. Correlations between pharmacodynamic measures and the improvement of sleep were investigated. Results The pharmacokinetic-pharmacodynamic relationships for the parameters derived from electroencephalography and saccadic eye movements showed considerable interindividual variability. Administration of temazepam led to a significant improvement in the objective parameters sleep period efficiency, wake time after sleep onset, and sleep efficiency and in the subjective assessment of sleep quality. No significant correlations were observed between the pharmacokinetic-pharmacodynamic-derived parameters and the improvement in objective or subjective sleep parameters. Conclusion In subjects with primary insomnia the administration of 20 mg oral temazepam results in changes in both the pharmacodynamic measures and in quality of sleep. No individual correlations between the pharmacodynamic measures and quality of sleep were observed. We concluded that the investigated pharmacodynamic measures are of value in the first assessment of clinical efficacy and for the selection of the dose(s) to be investigated in subsequent trials that aim at showing clinical efficacy. However, the conclusive quantification of clinical efficacy should be performed only on the basis of the clinical end point itself. Clinical Pharmacology & Therapeutics (1997) 62, 444–452; doi

BACKGROUND This epidemiologic study cross-sectionally examined the effects of sex and age on subjective characteristics of sleep and the factors related to self-evaluated sleep quality in a Dutch noninstitutionalized elderly population. METHODS 1,692 sleep questionnaires were mailed to all attenders of the general practice serving Krimpen aan de Lek, The Netherlands, aged 50 or over. Both target population and responders (1,485 subjects) were virtually representative of the Dutch population regarding sex and age (50 +) characteristics. RESULTS Overall, females reported significantly poorer quality of sleep, longer sleep latencies, more nighttime awakenings, less frequent napping, and more frequent use of sedative-hypnotic drugs when compared to males. Additionally, there was a female predominance in the prevalence of disturbed sleep onset and sleep maintenance, whereas a male predominance was observed in the prevalence of excessive daytime sleepiness. Across subjects, a significant age-related increment was found for sleep latency time and time spent in bed. The number of nighttime awakenings increased significantly with age only in males. No significant correlations were found between health status and sex, age, or subjective sleep quality. The most frequently reported causes of disturbed sleep onset and sleep maintenance were worries and nocturia, respectively. Subjective quality of sleep was mostly associated with self-estimated sleep latency. CONCLUSIONS Our findings extend those of previous epidemiologic studies reporting that sleep disorders are common in the general elderly population. Future studies should further elucidate the nature and extent of geriatric sleep disorders to satisfy the increasing need for its accurate diagnosis and treatment.

Although various investigators have suggested algorithms for the automatic detection of eye movements during sleep, objective comparisons of the proposed methods have previously been difficult due to different recording arrangements of different investigators. In this study the results of five eye movement detection algorithms applied to the same data were compared to visually scored data. The percentages of true and false detections are given for various threshold levels in rapid and slow eye movement detections. The methods gave best results when they were used with the same electrode montage they were designed for but the performance decreased when other montages were used. Subtracting the cross-talk of EEG delta activity improved the correctness of eye movement detections.

To assess the impact of institutionalization on sleep/wake characteristics of elderly people, we compared subjective (study I: n = 160) and objective (study II: n = 30) sleep/wake measures of non-demented institutionalized subjects and age-matched non-institutionalized controls. We also evaluated the prevalence and causes of various sleep disturbances. The three living conditions, i.e. independently living (IL), service home (SH) and nursing home (NH) were respectively assumed to have minimal, moderate and maximal effects upon the timing, the amount and the quality of the sleep/wake behaviour of the persons involved. Study I showed that a higher level of institutionalization was significantly (p < 0.05) associated with phase-advanced sleep/wake patterns, increased amounts of time spent in bed during the 24-hour period and increased usage of prescribed sedative-hypnotic drugs. Poor sleep quality and disturbed sleep onset occurred significantly mostly in the SH group. No differences between groups were demonstrated with respect to the prevalence of disturbed sleep maintenance, parasomnias and difficulty with awakening and their possible causes, except for environmental noise which was exclusively reported by institutionalized subjects. No differences between groups for any of the objective measures were found (study II). Overall, our findings are in line with previous findings on this topic, although the observed high rate of poor sleep quality and sleep disturbances and their associated causes as observed in institutionalized subjects also occurs in an age-matched non-institutionalized population.

The aim of this study was to compare the extent to which activity and immobility measures are related to sleep stages and sleep cycles in order to improve the informative value of actigraphic assessment of sleep. We therefore performed simultaneous ambulatory polysomnography and wrist-activity monitoring (AM) in 14 healthy male subjects without sleep complaints. In this context, a simple method for transforming raw motor activity data into a time-series reflecting onset and duration of activity and immobility clusters is introduced. Our results demonstrate that nocturnal AM measures were significantly affected by sleep stage. Low activity levels and particularly prolonged episodes of uninterrupted immobility were associated with increasing sleep depth. On the other hand, high activity levels and prolonged episodes of activity were related to intermittent wakefulness during sleep. Our results suggest that measures reflecting the occurrence and duration of activity and immobility clusters provide a better approach in studying the relationship between activity/immobility and sleep stages. Except for the duration of uninterrupted immobility episodes, which showed a significant decrease in the fourth cycle, none of the AM measures showed a significant cycle-to-cycle variation. Consequently, mean nocturnal motor activity measures provide an accurate reflection of the total sleep period. However, none of the AM-derived measures seems useful in evaluating the cycle structure during sleep.

In a prospective study of consecutive patients (age 15 or over) with transient loss of consciousness 45 patients had a history of seizure and 74 patients had a history of syncope. All patients had an EEG, ECG, laboratory tests and a hyperventilation test and were followed for an average of 14.5 months. Epileptiform activity in the interictal EEG had a sensitivity of 0.40 and a specificity of 0.95 for the diagnosis of a seizure. Epileptiform activity nearly doubled the probability of a seizure in doubtful cases. If no epileptiform activity was found, this probability remained substantially the same. The hyperventilation test had a sensitivity of 0.57 and a specificity of 0.84 for the diagnosis of syncope. A positive test increased the probability of syncope half as much in doubtful cases. A negative test did not exclude syncope. Laboratory tests were not helpful except for an ECG which was helpful in elderly patients.

RESUME Les auteurs ont enregistre pendant 40 jours ľelectroencephalogramme de facon continue, pendant la veille et pendant le sommeil, au moyen de 4 electrodes posees sur le scalp. Les electrodes n'ont entraine aucune lesion, aucun inconfort ni artefactbien qu'elles aient ete utilisees en partie sous des conditions arctiques. Les caracteristiques du sommeil enregistre ont ete les memes que celles retrouvees par les electrodes de surface. Les enregistrements ont une qualite suflisante pour permettre ľetablissement ďun hypnogramme suivant les criteres de Rechtshaffen et Kales. RESUMEN Utilizando 4 electrodos subcutaneos implantados en cuero cabelludo se han obtenido los corrrespondientes registros continuos de las fases de vigilia-sueno durante 40 dias. Los electrodes no causaron ningun dano ni inconveniente o artefact0 alguno incluso cuando fueron utilizados, parcialmente, bajo condiciones Articas. Las caractensticas del sueno registrado fueron semejantes a las que se ven con electrodos superficiales cutaneos. Los registros fueron de suficiente calidad como para permitir su cuantificacion segun los criterios de Rechtschaffen and Kales. ZUSAMMENFASSUNG Uber 40 Tage wurde ein kontinuierliches Schlaf-Wach-EEG mit 4 subcutanen Skalp-Elektroden abgeleitet. Die Elektroden verursachten weder Schmerzen, Ungehagen noch Artefakte, obwohl sie zum Teil unter artischen Bedingungen gebraucht wurden. Die Schlaf-EEG-Kurven gleichen denen bei Oberflachenelektroden. Die Qualitat war ausreichend gut, urn eine Einteilung nach Rechtschaffen und Kales vorzunehmen.

In a double-blind placebo-controlled trial, ritanserin (a 5-HT2 receptor blocker) 5 mg/day or placebo was added to the usual medication in 28 patients with narcolepsy during 4 wk. The effect was assessed by means of polysomnography, daily and weekly subjective evaluations, and Multiple sleep latency tests (MSLT). During the night ritanserin increased the amount of nonrapid eye movement slow wave sleep and reduced wakefulness after sleep onset. It improved the feeling of being refreshed in the morning after awakening and reduced subjective daytime sleepiness. The drug did not significantly influence sleep latency in the MSLT.

A model of sleep phasic events such as vertex waves, K complexes, delta waves and sleep spindles is proposed. It consists of feedback loops that are driven by white noise (simulating tonic delta and sigma activity) and by isolated random impulses, simulating vertex waves or K complexes, depending on the background tonic activity. A model-based method for the detection of sleep phasic events was implemented in a personal computer. Its performance was investigated using simulated and real whole-night EEG signals. The method was able to detect K complexes and vertex waves in a reliable way in spite of their variable shapes and in the presence of a variety of background activities. The detector appears to have superior performance to those so far reported in the literature. The performance of the detector was also compared to that of an electroencephalographer using normal sleep EEG records of 8 h duration from 6 subjects. The performance was satisfactory both in terms of accuracy and reliability. The problem of detecting K complexes in stages 3 and 4 of sleep is discussed.

The purpose of this study is to investigate whether the international standard electrode placement (C4-A1) can be replaced by an alternative placement (Fpz-Cz/Pz-Oz) in an automatic sleep monitoring system without losing Rechtschaffen and Kales (R-K) balances. Single night-sleep polygraphic recordings of 10 patients, screened in a clinical sleep disorder setting, were recorded simultaneously with both placements, and visual sleep classification was performed separately by two independent observers. Interobserver and interplacement agreement were evaluated by way of average (dis)agreement matrices and kappa values computed for overall and individual stage scoring. Interobserver agreement for both the test and the standard electrode placements and interplacement agreement for both observers were assessed as fair to good or excellent. Scoring differences were evaluated by the rank sign test applied to clinical and theoretical difference scores. It appears that the interplacement differences are about equal to the interobserver differences, except for a slight tendency for sleep to be scored in a deeper stage with the proposed alternative placement. The data are presented and discussed in relation to current literature concepts.

In dit hoofdstuk wordt eerst besproken wat gerontologie is en welke subdisciplines er zijn. Er zijn verschillende manieren om veroudering bij de mens te bestuderen: via transversaal, longitudinaal en time-lag onderzoek (met verstorende invloeden daarop van leeftijd-, cohort- en periode-effecten) en via onderzoek naar mortaliteit en morbiditeit. Een keurkorps van ‘senieurs’ bewijst dat bij sommige ouderen functies tot op zeer hoge leeftijd intact blijven.

Low-frequency EEG was analyzed quantitatively during 2 nights in 40 females and 34 males aged 26 to 101 years. Analyses were based on Rechtschaffen and Kales NREM sleep stages, on absolute low-frequency amplitude (i.e. power in the range of 0.2-2.0 Hz) and on low-frequency continuity. The latter parameter describes how much (0-100%) of the current slow-wave activity is continued in the near-future EEG. Such continuation can occur through closed loops in the underlying neuronal network and cells. These loops are slow, thus corresponding to slow-wave frequencies, and can consist of electrophysiological, chemical and/or other pathways. The continuity percentage then monitors the relative activity of these loops. It does not depend directly on absolute EEG amplitudes. All analyzed parameters, including amplitude-independent continuity, decreased substantially and significantly with increasing age. The amplitudes of low-frequency EEG in females were significantly and substantially (40%) larger than those in males. However, the amplitude-independent continuity percentage did not differ between the genders. These findings support the notion that gender-related anatomical differences have a general effect on EEG amplitude, including during slow-wave sleep. Aging, however, specifically affects the neurophysiological slow-wave-generating mechanism.

BACKGROUND--The combined use of wrist actigraphic assessment and self assessment of sleep in the screening of obstructive sleep apnoea syndrome was evaluated in a community based sample. METHODS--One hundred and sixteen community based subjects clinically suspected of having obstructive sleep apnoea (syndrome) were evaluated by means of simultaneous ambulatory recording of respiration (oronasal flow thermistry), motor activity (wrist actigraphy), and subjective sleep (sleep log) during one night of sleep. RESULTS--The subjects were distributed according to their apnoea index (AI); AI < 1 (non-apnoeic snorers) 44%; AI 1- < 5 39%; and AI > or = 5 17%. High apnoea index values were associated with self reported disturbed sleep initiation and more fragmented and increased levels of motor activity and decreased duration of immobility periods, particularly in those with an apnoea index of > or = 5. Across subjects the duration of immobility periods was the only predictor of the apnoea index, explaining 11% of its variance. Use of the multiple regression equation to discriminate retrospectively between those with an apnoea index of < 1 and > or = 5 resulted in sensitivity and specificity values of 75% and 43%, and 5% and 100%, respectively. CONCLUSIONS--The combined use of a sleep log and actigraphic assessment of sleep failed to identify reliably those subjects who suffered from obstructive sleep apnoea (syndrome) in a sample of community based subjects reporting habitual snoring combined with excessive daytime sleepiness and/or nocturnal respiratory arrests.

Objective: To assess differences in activity and immobility during sleep between patients with Parkinson's disease (PD) and healthy subjects and to evaluate the relations of clinical variables with the motor activity measures in patients with PD. Design: Survey, case series. Setting: University hospital outpatient neurology department and urban population in Leiden, the Netherlands. Motor activity was recorded during 6 successive nights at home with a wrist-worn activity monitor. Participants: Eighty-nine patients with PD and 83 age-matched healthy controls. Main Outcome Measures: For each subject, three mean measures reflecting activity or immobility during the nocturnal period were calculated. Results: Compared with the healthy elderly subjects, patients with PD have an elevated nocturnal activity level and an increased proportion of time with movement, indicating a more disturbed sleep. The mean duration of nocturnal immobility periods was similar for both groups. This measure, however, did reflect the self-reported disturbed sleep maintenance in both groups. The daily dose of levodopa or the use of dopamine agonists in patients not receiving levodopa, rather than disease severity, proved to be the best predictors of nocturnal activity. Conclusions: We hypothesize that in mildly to moderately affected patients with PD, levodopa or dopamine agonists cause sleep disruption by their effects on sleep regulation. In more severely affected patients, the beneficial effects of these drugs on nocturnal disabilities that cause sleep disruption in PD prevail.

The polygraphically recorded sleep-wake continuum of 21 Prader-Willi syndrome (PWS) patients was compared with that of 19 normal people. In the Prader-Willi group, excessive daytime sleepiness (EDS) is found in 95% of subjects, and rapid eye movement (REM) sleep disorders occur in 52%. These two features were significantly different from the normal group of subjects. No indications were found for the presence of the apnoea syndrome. The REM sleep disorders are: sleep onset rapid eye movements (SOREM), REM sleep in naps, many arousals during REM sleep, and a significant decrease in total REM sleep. These disturbances in the Prader-Willi group, combined with the presence of EDS and sometimes of cataplexy, are likely to be expressions of a narcoleptic syndrome although this was not sustained by the HI-A-DR2 expression above normal. The quality of life of PWS subjects can be improved in some cases by treating them as narcoieptic patients.

Objective: To measure the influence of age on measures of nocturnal activity and immobility in 100 healthy subjects aged 50 to 98 years. Design: Cross-sectional study. Setting: Urban population in Leiden. Recordings were performed at home while the subjects maintained their habitual 24-hour pattern of activities. Participants: 100 subjects without a history of major medical disorders and a normal neurological examination and performance-oriented assessment of gait (Tinetti). Measurements: Motor activity was recorded during six successive nights with a wrist-worn activity monitor. The occurrence of supra-threshold motor activity was recorded over 15-second epochs. A questionnaire was used to evaluate sleep habits and the occurrence of sleep disturbances. Four mean measures reflecting activity or immobility during the nocturnal period were calculated for each subject. Results: Only one out of four measures, (ie, the nocturnal proportion of time with movement, increased with age for females. For males, no age effects emerged. The mean duration of nocturnal immobility periods was higher in females than in males. Also, for females, the use of hypnotics increased with successive decades. Sex and the use of hypnotics were significantly related to the mean duration of immobility periods. Conclusion: If care is taken not to confound aging with illness, measures of nocturnal activity and immobility reveal only marginal effects of aging.

The aim of this study was to assess the internight and intrasubject variability of nocturnal activity and immobility measures of 99 healthy subjects aged 50-98 years. Motor activity was recorded at home during 6 successive nights with a wrist-worn activity monitor. The occurrence of suprathreshold motor activity was recorded over 15-second epochs. For each subject, six mean measures reflecting activity or immobility during sleep and their coefficient of variation were calculated. Our results revealed no first-night effect or day-of-week effect of the activity and immobility measures over the 6 nights across all subjects. On the other hand, for all nocturnal activity and immobility measures, a considerable intrasubject variability across the 6 nights was found. Females had a greater intrasubject variability of the mean duration of immobility periods and the movement index than males. The intrasubject variability of all nocturnal activity and immobility measures across the successive age groups remains stable. These findings emphasize that although a first-night effect may be lacking, the intrasubject variability of activity and immobility measures across several nights may still be considerable.

Objective The study was designed to investigate sleep-wake patterns in healthy elderly men and women (>88 years) using ambulatory recording techniques. Design Cross-sectional observations on 2 consecutive days. Methods Two consecutive 24-hour recordings were made. Each 30-second period of the recording was scored as characteristic of wakefulness, REM, and non-REM sleep (stages 1–4). Setting Interviews and recordings were done in the home of the elderly, not interfering with the habitual routine. Participants Among eligible members of the “Senieur” protocol, screened for wellness, seven females (88–102 years) and seven males (88–98 years) volunteered to participate. Main Outcome Measures Organization of sleep, sleep structure, and daytime napping. Results There was no difference between the first and second night recording. Important gender differences were observed: males had significantly less total sleep, shorter REM latency, more transitions to wake from REM, less NREM 3 sleep, and virtually no NREM 4. Daytime napping, REM amount, and distribution did not show sex differences. Although the variability in the amount of napping was considerable, it occupied less than 10 percent of the total sleep time in both women and men. Daytime napping was unrelated to sleep characteristics. Conclusions Ambulatory sleep-wake recordings allow an objective and critical evaluation of sleep function in normal aging. Interesting findings include a shift of REM sleep to the first part of the sleep period an increased cycle variability, and non-correlation of night-time sleep with daytime napping. In contrast to earlier findings in elderly persons, a polygraphic and subjective first-night effect was lacking.

The concept of a first night effect on sleep patterns, specifically in relation to age is a controversial topic in the literature. Our data are obtained during two consecutive 24-h ambulatory home sleep-wake recording in 10 elderly persons with a mean age of 85.5 years. Polysomnographic recordings indicated that a first night effect is present in old age, even using home recording, and that several types of insomnia can be differentiated, stressing that sleep cycle parameters should be taken into account. It is suggested that the first night effect is a 'miniature' replication of a psychophysiological insomnia.

Sleep-wakefulness (S-W) patterns were recorded continuously for 40 consecutive 24 h using subcutaneous chronic electrodes and an ambulatory cassette recorder in a healthy 57-year-old volunteer. Variability of sleep patterns was assessed in steady-state conditions and in the course of a scientific journey encompassing flights in both west/east and south/north directions. Data were compared with findings from age-matched laboratory control records. Polysomnographic evaluation of our sleep data shows: 1. (1) Stability of the first 3 sleep cycles and variability of the remaining sleep period with respect to both duration and structure. Vulnerability of REM sleep to environmental interference. 2. (2) Stability of the WASO/drowsiness cluster as an intraindividual biological trait independent of social interactions. The clinical relevance of ambulatory serial recording is stressed. 3. (3) The role of the first sleep cycle structure in the chronobiological adaptation process is documented. Apparently travelling in south/north directions may have similar or even more polygraphic implications than west/east transfer.

Episodic nocturnal phenomena represent a separate cluster of disturbances within the classification of sleep disorders. The reported case history covers paroxysmal signs occurring secondary to a REM-dependent mixed sleep apnoea syndrome. The pathophysiology of similar episodes in elderly (non-)epileptic patients is discussed. Ambulatory monitoring is an appropriate technique for investigation if respiratory and motor activity, and EEG and ECG are recorded simultaneously.

The effect of a single dose (30 mg) of Org 3770 (metirzapine) on human sleep was assessed in a double blind, placebo controlled, cross over study in 6 young, healthy male volunteers. The sleep stage classification was based on visual scoring of 24 h electroencephalographic recordings according to the criteria of Rechtschaffen and Kales. Org 3770 30 mg p.o. given 2 h before bedtime had a sleep promoting action in all subjects, resulting in a shortened time to the onset of sleep. Bedtime waking and dozing (Stage 1) were reduced in favour of deep, slow wave sleep (Stages 3 and 4). Org 3770 increased the latency of REM sleep with respect to Stage 2 sleep in all subjects. It also caused a minor reduction in waking periods during REM sleep and a lower frequency of awakenings after periods of movement. No effect of Org 3770 was observed in reaction and vigilance tests on the post treatment day. The observed effects of Org 3770 on normal human sleep suggest that it might ameliorate the sleep disturbances encountered in endogenous depression, which are characterized by a reduction in slow wave sleep, an increase in nighttime awakenings and shortening of REM sleep latency.

Cimetidine-related neurotoxicity may be characterized by signs of affective dysfunction, toxic delusional state and/or delirium, confusion and/or amnestic signs, coma, epileptic phenomena and focal neurological signs. EEG features are rarely mentioned in the literature. They are discussed here in a patient presenting with cimetidine-related mental impairment and epileptic seizures. Some of the clinical signs are related to our incomplete understanding of the neurotransmitter function of histamine in the brain. It is suggested that transient functional deafferentiation of the cortex may occur with chemical histamine receptor blockade at brain stem level. EEG monitoring may be helpful in patients at risk.

The plasma growth hormone profiles and sleep patterns of 13 treated male acromegalic patients, aged 29-67 years, were studied. All patients had undergone selective pituitary transsphenoidal surgery 4-9 years previously; five patients had also undergone supplemental pituitary irradiation. Blood samples were taken at 20-min intervals; the sleep patterns were obtained by EEG. GH reserve was assessed after insulin-induced hypoglycaemia and GHRH (1-44) with and without pyridostigmine. The profiles were analysed with the aid of the Pulsar program. Seven out of eight non-irradiated patients had 1-3 nocturnal GH peaks; in the irradiated group only one patient had a normal profile. The GH reserve after insulin-induced hypoglycaemia was normal in seven out of eight non-irradiated patients, and subnormal in all five irradiated patients. In the latter group the GH reserve was diminished when tested with GHRH. One patient from each group had a severe apnoea syndrome; in both cases there was no nocturnal GH increase. The percentage sleep stage 1 was lower for irradiated patients when compared with non-irradiated patients, but the 14 other sleep parameters did not differ. From this study we conclude that the physiological regulation of GH secretion is restored in surgically treated patients. Radiation therapy may lead to pituitary and hypothalamic damage, which could affect spontaneous GH secretion.

Summary: A Markov chain model has been proposed as a mechanism that generates human sleep stages, A method for estimating the parameters of the model, i.e., the transition probabilities (rates) between sleep stages, has been introduced and applied to 95 hypnograms taken from 23 subjects. The rates characterize interindividual differences and nightly variations of the sleep mechanism, related to sleep-onset behavior, to the decreasing amount of slow wave sleep in the course of the night, and to the REM-NREM periodicity, The model simulates both probabilistic and the above-mentioned predictable dy­ namics of sleep, but only if these time-varying, individual rates are applied.

Five male Irish Terrier puppies had a stiff gait, difficulty in swallowing, dirty cheeks because of food residues, an enlarged tongue and atrophic muscles. At electromyographical examination high-frequency discharges suggestive of myotonia were present. The values for serum creatine-phosphokinase and aldolase were extremely high. Serum vitamin E values were normal. At necropsy the muscles were pale with yellowish white streaks. Histologically there was a patchy distribution of the lesions. Granular and floccular changes (Zenker's degeneration) with phagocytosis, giant cells and calcification were found. Histochemical changes were the same in all muscles investigated, but were not equally pronounced. In the muscle specimens with greatest change the distinction between type I and type II fibres was largely lost. Rounded hypertrophic fibres contained no glycogen, and most did not show activity of phosphorylase, dehydrogenases, and oxidases. Activity of glyccrol-3-phosphate oxidase and acid phosphatase was markedly increased. Abnormal mitochondria and unknown electron-dense bodies were found. The tubular system seemed to be reduced in some abnormal fibres. The disease is probably recessive X-linked.

The effects of relatively constant plasma levels of a rapidly eliminated benzodiazepine (triazolam) were studied in young healthy males to determine whether tolerance to certain effects may develop over a relatively short period of time. The drug was given over a period of 30 h (2 days and 1 night) at zero-order rate using a rectal osmotic pump. Performance was measured at 2 hourly intervals during the day and was continuously impaired during the infusion, though there was a rapid recovery when the infusion ceased. All tasks were affected, in particular mental arithmetic and letter cancellation, but there was some improvement in performance during the second day. The normal circadian improvement in performance may have contributed to this effect, but some degree of tolerance to the effect of the drug cannot be excluded. Overnight there was a marked reduction in wakefulness, suppression of slow wave sleep, and delay to the onset and reduction in the duration of rapid eye movement sleep. During the night after infusion there was less slow wave sleep and increased wakefulness. The experimental design may prove useful in the study of tolerance to drugs.

In view of recent reports on lower brainstem dysfunction in Huntington's chorea, we studied respiration during sleep in 12 patients with Huntington's chorea (HC) and in controls. There were no statistically significant differences between patients and controls with respect to apnea periods, respiratory frequency and time elapsed between minimal and maximal value of the respiratory curve. No statistically significant differences in respiratory variability were observed between patients and controls. In the present study, no indication was found for dysfunction of lower brainstem structures involved in respiration in HC.

A new form of ultrasound diagnostic possibility is presented (the electroscan). The basic principles of this two dimensional method are described. Special attention is given to the probe consisting of an array of 21 elements of piezo-electric material. The results of this method in four patients are discussed (meningioma, arteriovenous aneurysm, subdural haematoma, and a baby with hydrocephalus). The baby with hydrocephalus showed diagnostic problems which could be understood from the pneumoencephalographic findings. The electroscan method seems to offer good possibilities for the diagnosis of brain lesions, if these have a consistency different from that of normal brain tissue.