Eye Movement Periods Research Articles

Sleep-related changes in hemodynamic and autonomic regulation in human hypertension

The present study investigates the hemodynamic and autonomic regulation during sleep-awake transitions and across different sleep cycles in patients with essential hypertension. Nineteen individuals free of sleep apnea (10 normotensive and nine hypertensive matched for age, sex, and body mass index) underwent a standard polysomnography, with simultaneous electrocardiography and beat-to-beat blood pressure monitoring (Portapres). All measurements were determined while awake (before and after sleep), as well as in the beginning and at end of the sleep cycle (first/last cycle of nonrapid and rapid eye movement stages). Systolic blood pressure was higher in hypertensives and exhibited a similar reduction to the normotensives ones in initial nonrapid eye movement sleep. This reduction was because of different mechanisms: a significant fall in cardiac output in normotensives, whereas in hypertensives was also dependent of a decrease in peripheral vascular resistance. Hypertensive patients presented lower heart rate variation and attenuated baroreflex sensitivity during sleep but not immediately before and after sleep. Spectral analysis suggested a higher sympathetic activity in the sleep stages in hypertension. Additionally, a progressive sympathetic predominance (final rapid eye movement > initial rapid eye movement and awake period postsleep > awake period presleep) was observed in both groups. Hypertension is associated with depressed baroreflex sensitivity and increased sympathetic activation during sleep. The greater sympathetic predominance at the end of night (preceding the morning surge of sympathetic activity) could be implicated in the occurrence of cardiovascular events.

Three-dimensional Morphological Analyses of Positional Dependence in Patients with Obstructive Sleep Apnea Syndrome

It is generally considered that patients with obstructive sleep apnea syndrome (OSAS) at increased perioperative risk should be placed in nonsupine positions throughout the recovery process; however, not all patients with OSAS show positional dependence. The authors hypothesized that morphological differences exist in three-dimensional (3D) soft tissue and craniofacial structures of the pharyngeal airway between positional and nonpositional OSAS. The subjects of the study were body mass index-matched, age-matched, and apnea hypopnea index-matched positional (n = 10) and nonpositional (n = 10) Japanese OSAS patients and body mass index-matched Japanese control subjects (n = 10). Pharyngeal magnetic resonance imaging and cephalometric radiography were performed during wakefulness. The patients with positional OSAS had a smaller volume of the pharyngeal lateral wall soft tissues, larger maxilla-nasion-mandible angle, and smaller lower facial height than the nonpositional OSAS and the control subjects. The patients with positional OSAS showed a significantly steeper sella-nasion-mandible angle and smaller craniofacial volume than the control subjects. There were no significant differences in tongue volume and 3D pharyngeal anatomical balance between positional and nonpositional OSAS. Multivariate stepwise regression for positional dependence showed that the dominant determinant was the volume of the lateral pharyngeal wall, followed by lower facial height and maxilla-nasion-mandible angle. Patients with positional OSAS have wider airways in the lateral parts, lower facial height, and more backward position of the lower jaw, which may explain differences in the maintenance of pharyngeal airway patency in the lateral sleep position.

Tonic and phasic phenomena underlying eye movements during sleep in the cat

Mammalian sleep is not a homogenous state, and different variables have traditionally been used to distinguish different periods during sleep. Of these variables, eye movement is one of the most paradigmatic, and has been used to differentiate between the so-called rapid eye movement (REM) and non-REM (NREM) sleep periods. Despite this, eye movements during sleep are poorly understood, and the behaviour of the oculomotor system remains almost unknown. In the present work, we recorded binocular eye movements during the sleep-wake cycle of adult cats by the scleral search-coil technique. During alertness, eye movements consisted of conjugated saccades and eye fixations. During NREM sleep, eye movements were slow and mostly unconjugated. The two eyes moved upwardly and in the abducting direction, producing a tonic divergence and elevation of the visual axis. During the transition period between NREM and REM sleep, rapid monocular eye movements of low amplitude in the abducting direction occurred in coincidence with ponto-geniculo-occipital waves. Along REM sleep, the eyes tended to maintain a tonic convergence and depression, broken by high-frequency bursts of complex rapid eye movements. In the horizontal plane, each eye movement in the burst comprised two consecutive movements in opposite directions, which were more evident in the eye that performed the abducting movements. In the vertical plane, rapid eye movements were always upward. Comparisons of the characteristics of eye movements during the sleep-wake cycle reveal the uniqueness of eye movements during sleep, and the noteworthy existence of tonic and phasic phenomena in the oculomotor system, not observed until now.

Challenging Sleep Homeostasis in Narcolepsy-Cataplexy: Implications for Non-REM and REM Sleep Regulation

We recently proposed insufficient non-rapid eye movement sleep (NREMS) intensity to contribute to disturbed nocturnal sleep in patients with narcolepsy-cataplexy (NC). To test this hypothesis, we investigated the effect of physiologically intensified NREMS in recovery sleep following sleep deprivation. Nocturnal baseline and recovery sleep architecture, and the sleep electroencephalogram (EEG) before and after 40 hours of sustained wakefulness were compared between 6 drug-free patients with NC (age range: 19-37 years) and 6 individually matched, healthy control subjects (18-43 years). Sleep and sleep EEG power spectra (C3A2 derivation). The dynamics of the homeostatic Process S were estimated from the time course of slow-wave activity (SWA, spectral power within 0.75-4.5 Hz) across consecutive NREMS episodes. Sleep research laboratory. In baseline, SWA decreased across consecutive NREMS episodes in patients with NC and control subjects. The build-up of SWA, however, was attenuated in NC in the second episode (P = 0.01) due to a higher number of short wake periods (P = 0.02). Prolonged wakefulness increased initial SWA in both groups (P = 0.003) and normalized the baseline differences between patients and control subjects in the time course of SWA in NREMS. The changed dynamics of SWA in the patients in recovery sleep when compared with baseline were associated with reduced numbers of intermittent wake periods in the first (P = 0.01) and second (P = 0.04) NREMS episodes. All patients, but no control subjects, showed a sleep-onset rapid eye movement period (SOREMP) in both baseline and recovery sleep. Sleep deprivation increased SOREMP duration (P = 0.03). Increased SWA after sleep deprivation indicates that sleep homeostasis is functional in NC. Increased NREMS intensity in recovery sleep postpones sleep fragmentation, supporting our concept that sleep fragmentation is directly related to insufficient NREMS intensity in NC. The persistence of SOREMP despite enhanced NREMS pressure suggests an abnormal interaction between NREMS and REMS regulatory processes.

Shape Selectivity in Primate Frontal Eye Field

Previous neurophysiological studies of the frontal eye field (FEF) in monkeys have focused on its role in saccade target selection and gaze shift control. It has been argued that FEF neurons indicate the locations of behaviorally significant visual stimuli and are not inherently sensitive to specific features of the visual stimuli per se. Here, for the first time, we directly examined single cell responses to simple, two-dimensional shapes and found that shape selectivity exists in a substantial number of FEF cells during a passive fixation task or during the sample, delay (memory), and eye movement periods in a delayed match to sample (DMTS) task. Our data demonstrate that FEF neurons show sensory and mnemonic selectivity for stimulus shape features whether or not they are behaviorally significant for the task at hand. We also investigated the extent and localization of activation in the FEF using a variety of shape stimuli defined by static or dynamic cues employing functional magentic resonance imaging (fMRI) in anesthetized and paralyzed monkeys. Our fMRI results support the electrophysiological findings by showing significant FEF activation for a variety of shape stimuli and cues in the absence of attentional and motor processing. This shape selectivity in FEF is comparable to previous reports in the ventral pathway, inviting a reconsideration of the functional organization of the visual system.

Narcolepsy in Children: A Single-Center Clinical Experience

Although the initial manifestations of narcolepsy in children may differ from those with adult onset, hypersomnia remains the most common presenting sign. This study aimed to (1) describe the clinical and polysomnographic features, and treatment outcomes, of a group of children with narcolepsy, and (2) describe other sleep disorders to be considered in the differential diagnosis of hypersomnia and which may coexist with narcolepsy. A retrospective review of 125 children referred in 1 year for hypersomnia revealed 20 patients (16%) with narcolepsy. Of these, only 15% exhibited cataplexy, 10% experienced hallucinations, and none manifested sleep paralysis. Eighty-five percent of children with narcolepsy had sleep-disordered breathing on polysomnography. Body mass indices of these children were higher than for healthy, age-matched controls subjects. Other polysomnography findings included periodic limb movements of sleep (25%) and parasomnias (5%). The multiple sleep latency test revealed a mean sleep latency of 6.14 minutes, with sleep-onset rapid eye movement periods (median, 2/5 naps). Treatment with modafinil and sodium oxybate provided optimal control of daytime sleepiness. Physicians should routinely screen for hypersomnia in children by obtaining a detailed history and, in appropriate situations, ordering polysomnographic testing to rule out narcolepsy and other causes of hypersomnia.

Sleep Disorders in Chronic Traumatic Brain Injury

To examine the spectrum of sleep disorders in patients with chronic traumatic brain injury (TBI) and determine if the severity of sleep disorder is related to severity of chronic TBI. Patients who underwent evaluation for sleep disorder/s following a TBI were included in this retrospective analysis. Sixty adult patients with TBI (age 20-69 yr; 38 M and 22 F), who presented with sleep-related complaints 3 months to 2 years following TBI, were studied. None had sleep complaints prior to the TBI. Orophrayngeal, chin, and TMJ examinations were considered benign. The severity of injury was assessed by the Global Assessment of Functioning (GAF) scale. Polysomnograms (PSGs) were performed on 54 patients (90%), 28 of whom underwent multiple sleep latency tests (MSLTs) because they scored >11 on the Epworth Sleepiness Scale (ESS). The Beck Depression Inventory (BDI) scale was administered if there was sleep maintenance insomnia, and the Hamilton Anxiety Scale (HAS) was administered if there was sleep onset insomnia. The TBI severity was mild in 40%, moderate in 20%, and severe in 40%. The Epworth Sleepiness Scale (ESS) score was elevated (>11) in 52%. Hypersomnia was the presenting complaint in 50%, mostly due to sleep apnea, narcolepsy, and periodic limb movement disorder (PLMD). Insomnia was the presenting complaint in 25%, half with sleep maintenance insomnia and high BDI scores, and the remainder with sleep onset insomnia and high HAS scores. Parasomnia was the presenting complaint in 25%; the most frequent parasomnia was REM behavior disorder (RBD). GAF scores were significantly correlated (p < 0.05) with some of the measures of sleep disruption (stage 1, sleep efficiency, and wake during sleep), but not with others (wake before sleep, stage-shifts, PLMI, PLMA and AHI) on the PSG. Fifty-three percent (15/28) had a mean sleep onset latency <5 minutes, and 32% (9/28), also had two or more sleep onset rapid eye movement periods (SOREMPs) on the MSLT. The results of this study demonstrate that a full spectrum of common sleep disorders occurs in patients with chronic TBI. The severity of chronic TBI as measured by GAF scores is correlated with some of the measures of sleep disruption but not others, indicating a complex and multifactorial pathogenesis.

Sleep and Well-Being of ICU Housestaff

Our understanding of the effect of the Accreditation Council for Graduate Medical Education (ACGME)-mandated work-hour limitation on physicians' quality of life, sleepiness, and sleep-work habits is evolving. In this study, we sought to determine the effect of work-hour reduction on quality of life in residents and fellows (ICU housestaff) when subject to the ACGME-compliant schedule of one institution. To determine the effect of work-hour reduction on subjective and objective measures of sleepiness in ICU housestaff at a center. A single-center study of 34 residents and 10 fellows who were studied before and after the ACGME-mandated work-hour limitation went into effect in July 2003. In a single center, after the work-hour reduction, residents reported statistically significant but minor improvements in sleep time, subjective sleepiness, and some aspects of quality of life (p < 0.05). Both before and after work-hour limitations, subjective sleepiness and quality-of-life indexes deteriorated during the course of the ICU rotation. Following work-hour reductions, subjective sleepiness improved (p < 0.05), but objective sleepiness was unchanged (p = 0.6). Moreover, after the implementation of work-hour reductions, 59%, 43%, and 25% of the ICU team had mean sleep latency < 10, 7, and 5 min, respectively, with 14% of the team manifesting sleep-onset rapid eye movement periods (signifying severe sleepiness) before beginning their extended work-hour period. In ICU housestaff, at a single center, small benefits to quality of life and subjective sleepiness were realized by an ACGME-compliant work-hour schedule. Significant levels of objective sleepiness, however, remained. Further measures may need to be undertaken to address the persistence of sleepiness in ICU housestaff. These findings may not be generalized outside of the scheduling system studied.

Ocular dipping and ping-pong gaze in hypoxic encephalopathy

A 16-year-old girl with fever of unknown origin was found comatose in the morning. Examination disclosed periodic eye movements with an initial downward deviation followed by rapid upward correction (dipping), which lasted 10 to 15 seconds (figure, A; video E-1, on the Neurology Web site at www.neurology.org). Intermittently, these movements were followed by slow to-and-fro horizontal eye motion (ping-pong gaze) immediately or with a latency of several seconds (figure, A, arrow; video E-1). During the dipping and roving eye motion, EEG …

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Although transitory alternating saccade (TAS) is classically-observed as one of the cerebellar ocular-motor signs, its occurrence has been noted only in isolated cases in the literature. In the present study, we quantitatively examined a total of 29 TAS waveforms with spectral analysis by discrete Fourier transformation. TAS was characterized by periodic eye movements over a time course of several seconds coupled with fast eye movement that reverses its direction. That is, the low frequency component of TAS was a periodic eye drift with a frequency of 0.36±0.09 Hz and an amplitude of 11.4±4.4°, whereas the high frequency component was a nystagmus-like eye movement with an amplitude of 1.41±0.4°. Routine computerized electronystagmography (ENG) testing revealed that in only 3 cases TAS was observed during the testing of spontaneous nystagmus. In another 26 cases, TAS was evoked during head position-change, neck stimulation such as neck-torsion and carotid-compression, or after optokinetic and rotational stimulation. In 48% of the 29 cases, disorders in visual fixation, smooth pursuit, and optokinetic nystagmus were also seen. TAS may be a result of the pathological oculomotor findings associated with lesions in the vicinity of the midline of the cerebellum.

Physiology of sleep

Sleep is a vital, highly organized process regulated by complex systems of neuronal networks and neurotransmitters. Normal sleep comprises non-rapid eye movement (NREM) and REM periods that alternate through the night. Sleep usually begins in NREM and progresses through deeper NREM stages (2, 3, and 4 stages), but newborns enter REM sleep (active sleep) first before NREM (quiet sleep). A period of NREM and REM sleep cycle is approximately 90 minutes, but newborn have a shorter sleep cycle (50 minutes). As children mature, sleep changes as an adult pattern: shorter sleep duration, longer sleep cycles and less daytime sleep. REM sleep is approximately 50% of total sleep in newborn and dramatically decreases over the first 2 years into adulthood (20% to 25%). An initial predominant of slow wave sleep (stage 3 and 4) that peaks in early childhood, drops off abruptly after adolescence by 40% from preteen years, and then declines over the life span. The hypothalamus is recognized as a key area of brain involved in regulation of sleep and wakefulness. The basic function of sleep largely remains elusive, but it is clear that sleep plays an important role in the regulation of CNS and body physiologic processes. Understanding of the architecture of sleep and basic mechanisms that regulate sleep and wake cycle are essential to evaluate normal or abnormal development of sleep pattern changes with age. Reduction or disruption of sleep can have a significant impact on daytime functioning and development, including learning, growth, behavior, and emotional regulation.

Simplified ultrasound screening for fetal brain function based on behavioral pattern

Despite the longstanding conclusion that behavior can reveal aspects of underlying anatomy and function, no generalized antenatal behavior screening has been developed to identify fetuses that may have central nervous system defects requiring further evaluation. We devised a brief ultrasound examination to distinguish fetuses with compromised central nervous system function from the general population and evaluated it with this study. The study design compared behavioral findings obtained by retrospectively reviewing the ultrasound examinations of 5 fetuses that had abnormal behavior with prospectively obtained findings of 29 normal fetuses. Median time for brief examination criteria was 50 min (range, 30–60 min). The only case undetectable by this brief ultrasound examination has an eye-movement period significantly longer than the normal upper limit. Using this method as a screening test may make it possible to include assessment of fetal brain function as part of routine antenatal care.

The Prevalence of Multiple Sleep-Onset REM Periods in a Population-Based Sample

The presence of 2 or more sleep-onset rapid eye movement periods (SOREMPs) on a Multiple Sleep Latency Test (MSLT) has been used as 1 of the criteria for the diagnosis of narcolepsy and is thought to be specific to this disorder. However, previous studies have shown the prevalence of SOREMPS in healthy volunteers and apneic patients to be higher than expected. The present study determined the prevalence of 2 or more SOREMPs in a representative sample of the population from southeast Michigan and investigated potential associations with other sleep-related variables. Cross-sectional laboratory-based analysis. Sleep disorders clinic. Population-based sample. N/A. A population-based sample of 333 subjects was assessed by nocturnal polysomnography and daytime MSLT (5 naps), and an additional 206 subjectively sleepy people were also assessed (total = 539). Sample demographics were comparable to the 2000 census. Epworth Sleepiness Scale scores were also determined. Groups were formed based on a median split of each sleep variable (Epworth Sleepiness Scale, MSLT, total sleep time from nocturnal polysomnography) for comparisons of SOREMPs in each group. The prevalence of 2 or more SOREMPs was 3.9%. Only mean sleep latency on the MSLT was a discriminator for the presence of 2 or more SOREMPs (short latency = 6.3%, long latency = 1.9%, p < .05). Among the subjects who had an MSLT of 5 minutes or less (an indicator of a pathologic level of sleepiness), 9.5% had 2 or more SOREMPS. The overall prevalence of 2 or more SOREMPs in our sample is 3.9%. Interestingly, of the variables assessed (MSLT, Epworth Sleepiness Scale, and total sleep time from nocturnal polysomnography), objective sleepiness, as determined by the MSLT, was the only measure significantly associated with 2 or more SOREMPs. Therefore, subpopulations with excessive sleepiness (eg, shift workers, young adults, patients with apnea) are likely to have a greater prevalence of SOREMPs.

Timing of spontaneous sleep‐paralysis episodes

The objective of this prospective naturalistic field study was to determine the distribution of naturally occurring sleep-paralysis (SP) episodes over the course of nocturnal sleep and their relation to bedtimes. Regular SP experiencers (N = 348) who had previously filled out a screening assessment for SP as well as a general sleep survey were recruited. Participants reported, online over the World Wide Web, using a standard reporting form, bedtimes and subsequent latencies of spontaneous episodes of SP occurring in their homes shortly after their occurrence. The distribution of SP episodes over nights was skewed to the first 2 h following bedtime. Just over one quarter of SP episodes occurred within 1 h of bedtime, although episodes were reported throughout the night with a minor mode around the time of normal waking. SP latencies following bedtimes were moderately consistent across episodes and independent of bedtimes. Additionally, profiles of SP latencies validated self-reported hypnagogic, hypnomesic, and hypnopompic SP categories, as occurring near the beginning, middle, and end of the night/sleep period respectively. Results are consistent with the hypothesis that SP timing is controlled by mechanisms initiated at or following sleep onset. These results also suggest that SP, rather than uniquely reflecting anomalous sleep-onset rapid eye movement (REM) periods, may result from failure to maintain sleep during REM periods at any point during the sleep period. On this view, SP may sometimes reflect the maintenance of REM consciousness when waking and SP hallucinations the continuation of dream experiences into waking life.

Objective Measures of Sleepiness and Wakefulness: Application to the Real World?

The impact of excessive sleepiness on the individual and on society is immense, and chronic sleepiness is one of the most common complaints evaluated by sleep medicine specialists. The author explores how measures of sleepiness and wakefulness using the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT) can be clinically useful. A companion article presents a counterpoint discussion of the limitations and drawbacks associated with the MSLT and MWT. Both presentations use an evidence-based approach to understanding the operating characteristics of these tests, and the overall goal is to clarify for sleep medicine specialists the positive and negative attributes of the MSLT and MWT. The MSLT and MWT are the most widely accepted objective measures of an individual's ability to fall asleep and ability to remain awake, respectively. The MSLT is a well-validated and extensively published objective measure of the speed at which a subject falls asleep under standardized laboratory conditions, and it is associated with good to excellent interrater and intrarater reliability, and excellent test-retest reliability. The MSLT is indicated as part of the evaluation of suspected narcolepsy and it may be helpful in differentiating narcolepsy from idiopathic hypersomnia. Mean sleep latency values less than 5 minutes are observed in the majority of subjects with narcolepsy, and the presence of two or more sleep-onset rapid eye movement periods is strongly correlated with a diagnosis of narcolepsy. An MSLT should be performed to address specific clinical questions, and should not be used as a screening tool. The MWT has clinical usefulness in evaluating response to treatment following intervention for conditions associated with excessive sleepiness, and in assessing individuals who must remain awake for safety reasons. However, the sleep medicine specialist should not rely solely on mean sleep latency values as a single indicator of impairment or risk of accidents, but findings should be integrated with the clinical history, compliance, patient judgment, and other factors to form a global impression regarding the individual's response to treatment. Future challenges include refinement of normative ranges in different populations using rigorous statistical methods, and improved understanding of the specific operating characteristics of the MSLT and MWT in different age groups. Additional study is necessary regarding the impact of MSLT and MWT findings on clinical decision-making, patient outcome, and patient and physician satisfaction. From a safety and regulatory standpoint, additional study is needed to establish the correlation between MWT findings and the risk of adverse consequences of sleepiness such as accidents. Because the MSLT and MWT are in-laboratory tests, it is important that investigators also develop novel techniques that provide reliable assessment of sleepiness and wakefulness in the actual work environment over extended periods. In summary, the MSLT and MWT are not perfect tests, but they are the best objective measures currently available for characterization of ability to fall asleep and ability to remain awake.

Narcolepsy in Singapore: Is it an Elusive Disease?

Introduction: The aims of the study were to determine the demographic, clinical, and polysomnographic characteristics of narcolepsy, and to address the difficulties in diagnosing narcolepsy and cataplexy, which is a cardinal symptom. We also ventured to investigate the differences between narcolepsy with and without cataplexy. Materials and Methods: Data were collected retrospectively from patients diagnosed with narcolepsy at the Sleep Disorder Unit of Singapore General Hospital over 5 years. Each patient had had a detailed clinical evaluation and overnight polysomnography (PSG) followed by a multiple sleep latency test (MSLT). Results: A total of 28 cases were studied. Males made up 85.7% of the total and females, 14.3%. The mean age was 30.9 years. All had excessive daytime sleepiness. Other manifestations were cataplexy (48.1%), sleep paralysis (51.9%), hypnogogic hallucinations (84%), disturbed night sleep (29.2%), automatisms (17.4%) and catnaps (95.8%). The mean duration of symptoms was 7.24 years. In the MSLT, the mean values for mean sleep latency and number of sleep onset rapid eye movement (REM) periods (SOREMP) were 4.3 minutes and 2.7, respectively. Narcolepsy was associated with obstructive sleep apnoea and periodic limb movement disorder (35.7%). All the variables were compared between those who had narcolepsy with cataplexy and without cataplexy. The duration of presenting complaint, REM latency, respiratory disturbance index, number of SOREMPs and the presence of sleep paralysis were significantly different in the 2 groups. Conclusions: Narcolepsy predominantly affects young males. Concurrence of other sleep disorders is not uncommon. Some differences are evident between those who have narcolepsy with and without cataplexy.

Secondary Narcolepsy Following Neurocysticercosis Infection

The authors describe a case of secondary narcolepsy resulting from neurocysticercosis infection. Neurocysticercosis is a common central nervous system parasitic disease endemic to Central and South America caused by ingestion of eggs from a host with intestinal taeniasis. Neurological deficits depend on lesion location. Our case developed a hypothalamic cyst causing severe sleepiness and sleep-onset rapid eye movement periods on both polysomnography and multiple sleep latency testing. The cerebrospinal fluid hypocretin-1 level was normal indicating secondary narcolepsy can result without failure of hypocretin production. The diagnosis of neurocysticercosis should be considered in any individual with excessive sleepiness and recent travel to endemic regions of the world.

Sleep structure: a new diagnostic tool for stage determination in sleeping sickness

Human African trypanosomiasis (HAT), due to the transmission of Trypanosoma brucei ( T. b.) gambiense and T. b. rhodesiense by tsetse flies, is re-emerging in inter-tropical Africa. It evolves from the hemolymphatic Stage I to the meningo-encephalitic Stage II. The latter is generally treated with melarsoprol, an arseniate provoking often a deadly encephalopathy. A precise determination of the HAT evolution stage is therefore crucial. Stage II patients show: (i) a deregulation of the 24-h distribution of the sleep–wake alternation; (ii) an alteration of the sleep structure, with frequent sleep onset rapid eye movement (REM) periods (SOREMPs). Gambian HAT was diagnosed in eight patients (four, Stage II; three, Stage I; one, “intermediate” case) at the trypanosomiasis clinic at Viana (Angola). Continuous 48-h polysomnography was recorded on Oxford Medilog 9000-II portable systems before and after treatment with melarsoprol (Stage II) or pentamidine (Stage I and “intermediate” stage). Sleep traces were visually analyzed in 20-s epochs using the PRANA software. Stage II patients showed the complete sleep–wake syndrome, partly reversed by melarsoprol 1 month later. Two Stage I patients did not experience any of these alterations. However, the “intermediate” and one Stage I patients exhibited sleep disruptions and/or SOREMPs, persistent after pentamidine treatment. Polysomnography may represent a diagnostic tool to distinguish the two stages of HAT. Especially, SOREMPs appear shortly after the central nervous system invasion by trypanosomes. The reversibility of the sleep–wake cycle and sleep structure alterations after appropriate treatment constitutes the basis of an evaluation of the healing process.

Diagnostic ambiguities in a case of post-traumatic narcolepsy with cataplexy

Narcolepsy arising from trauma can present particular problems of differential diagnosis. In this case study presentation the patient suffered a head trauma, without unconsciousness, and began to experience unusual episodic behaviours. Symptom presentation differed from the typical clinical manifestations of idiopathic narcolepsy leading to an 8-year search for a definitive diagnosis. Key relevant aspects that led to diagnostic ambiguities were the order of symptom development, negative for the antigen HLA DR2, significance of the Multiple Sleep Latency Test (MSLT) mean sleep latency versus number of sleep onset rapid eye movement periods, the somewhat atypical features of cataplexy, the coexistence of sleep apnoea, and the mildness of the original head injury. It is argued that cases of post-traumatic narcolepsy should be considered in the context of their clinical development over time and that practitioners should be aware that this form of narcolepsy can differ from the typical clinical history of idiopathic narcolepsy.

Sleep microstructure around sleep onset differentiates major depressive insomnia from primary insomnia.

In the present study we investigate whether alterations of sleep propensity or of wake propensity are implicated in sleep initiation disturbances encountered in major depressive insomnia and in primary insomnia. For this purpose, the time course of electroencephalogram (EEG) power density during the period preceding sleep onset and during the first non-rapid eye movement (REM) period was examined in three age and gender matched groups of 10 women and 11 men (healthy controls, primary insomniacs and depressive insomniacs). In contrast to healthy controls and depressive insomniacs, patients with primary insomnia did not experience a gradual decrease of their alpha and beta1 power during the sleep onset period and had a lower delta activity in the 5 min preceding sleep onset. Compared with the two other groups, depressive patients exhibit less dynamic changes in slow wave activity during the first non-REM period. The present results suggest that hyperarousal (high 'Process W') may mainly be implicated in the sleep initiation difficulties of primary insomniacs whereas the homeostatic sleep regulation process seems to be partially maintained. In our major depressed patients, the sleep initiation disturbances appeared to relate to a lower sleep pressure (low 'Process S') rather than to hyperarousal. This study supports the idea that different mechanisms are implicated in sleep disturbances experienced by primary insomniacs and major depressive insomniacs.