Sleep patterns in acute ischemic stroke

Sleep-like cortical dynamics during wakefulness and their network effects following brain injury

By connecting old and recent notions, different spatial scales, and research domains, we introduce a novel framework on the consequences of brain injury focusing on a key role of slow waves. We argue that the long-standing finding of EEG slow waves after brain injury reflects the intrusion of sleep-like cortical dynamics during wakefulness; we illustrate how these dynamics are generated and how they can lead to functional network disruption and behavioral impairment. Finally, we outline a scenario whereby post-injury slow waves can be modulated to reawaken parts of the brain that have fallen asleep to optimize rehabilitation strategies and promote recovery.

Deciphering Post-Stroke Sleep Disorders: Unveiling Neurological Mechanisms in the Realm of Brain Science

Sleep disorders are the most widespread mental disorders after stroke and hurt survivors' functional prognosis, response to restoration, and quality of life. This review will address an overview of the progress of research on the biological mechanisms associated with stroke-complicating sleep disorders. Extensive research has investigated the negative impact of stroke on sleep. However, a bidirectional association between sleep disorders and stroke exists; while stroke elevates the risk of sleep disorders, these disorders also independently contribute as a risk factor for stroke. This review aims to elucidate the mechanisms of stroke-induced sleep disorders. Possible influences were examined, including functional changes in brain regions, cerebrovascular hemodynamics, neurological deficits, sleep ion regulation, neurotransmitters, and inflammation. The results provide valuable insights into the mechanisms of stroke complicating sleep disorders.

Disturbed laterality of non-rapid eye movement sleep oscillations in post-stroke human sleep: a pilot study

Sleep is known to promote recovery post-stroke. However, there is a paucity of data profiling sleep oscillations in the post-stroke human brain. Recent rodent work showed that resurgence of physiologic spindles coupled to sleep slow oscillations (SOs) and concomitant decrease in pathological delta (δ) waves is associated with sustained motor performance gains during stroke recovery. The goal of this study was to evaluate bilaterality of non-rapid eye movement (NREM) sleep-oscillations (namely SOs, δ-waves, spindles, and their nesting) in post-stroke patients vs. healthy control subjects. We analyzed NREM-marked electroencephalography (EEG) data in hospitalized stroke-patients (n = 5) and healthy subjects (n = 3). We used a laterality index to evaluate symmetry of NREM oscillations across hemispheres. We found that stroke subjects had pronounced asymmetry in the oscillations, with a predominance of SOs, δ-waves, spindles, and nested spindles in affected hemisphere, when compared to the healthy subjects. Recent preclinical work classified SO-nested spindles as restorative post-stroke and δ-wave-nested spindles as pathological. We found that the ratio of SO-nested spindles laterality index to δ-wave-nested spindles laterality index was lower in stroke subjects. Using linear mixed models (which included random effects of concurrent pharmacologic drugs), we found large and medium effect size for δ-wave nested spindle and SO-nested spindle, respectively. Our results in this pilot study indicate that considering laterality index of NREM oscillations might be a useful metric for assessing recovery post-stroke and that factoring in pharmacologic drugs may be important when targeting sleep modulation for neurorehabilitation post-stroke.

Disturbed laterality of non-rapid eye movement sleep oscillations in post-stroke human sleep: a pilot study

Sleep is known to promote recovery post-stroke. However, there is a paucity of data profiling sleep oscillations post-stroke in the human brain. Recent rodent work showed that resurgence of physiologic spindles coupled to sleep slow oscillations(SOs) and concomitant decrease in pathological delta(δ) waves is associated with sustained motor performance gains during stroke recovery. The goal of this study was to evaluate bilaterality of non-rapid eye movement (NREM) sleep-oscillations (namely SOs, δ-waves, spindles and their nesting) in post-stroke patients versus healthy control subjects. We analyzed NREM-marked electroencephalography (EEG) data in hospitalized stroke-patients (n=5) and healthy subjects (n=3) from an open-sourced dataset. We used a laterality index to evaluate symmetry of NREM oscillations across hemispheres. We found that stroke subjects had pronounced asymmetry in the oscillations, with a predominance of SOs, δ-waves, spindles and nested spindles in one hemisphere, when compared to the healthy subjects. Recent preclinical work classified SO-nested spindles as restorative post-stroke and δ-wave-nested spindles as pathological. We found that the ratio of SO-nested spindles laterality index to δ-wave-nested spindles laterality index was lower in stroke subjects. Using linear mixed models (which included random effects of concurrent pharmacologic drugs), we found large and medium effect size for δ-wave nested spindle and SO-nested spindle, respectively. Our results indicate considering laterality index of NREM oscillations might be a useful metric for assessing recovery post-stroke and that factoring in pharmacologic drugs may be important when targeting sleep modulation for neurorehabilitation post-stroke.

The Importance of Sleep for Successful Neurorehabilitation after Stroke

Sleep has important clinical implications for neurorehabilitation after stroke. We aimed to systematically explore sleep (including naps) as an essential factor in the neurorehabilitation of patients after stroke. After titles and abstracts were screened, 49 full texts were reviewed, and 7 were included in this review. Data were extracted and assessed for quality and risk of bias. We looked at any neurorehabilitation setting, and compared sleep with no sleep and explored these factors in stroke patients versus healthy individuals. Rehabilitation is critical for many activities that may need to be learned or re-learned following stroke and for returning to everyday life. In this context, sleep is essential in neurorehabilitation and physical therapy practice as it supports neuroplasticity, memory, and learning. The available data suggest that sleep should be considered in the treatment plan for successfully targeted physiotherapy to optimize cognitive and motor learning. Physical therapists should advise about sleep hygiene and therapies to improve sleep, both quality and quantity.

Stroke: What's Sleep Got to Do With It?

SUMMARY

Ischemic strokes most often occur between 6 am and 12 am after awakening from sleep but up to 30% occur during sleep. Wake-up strokes (WUS) are new focal neurological deficit(s) persisting for ≥ 24 hours attributable to an ischemic event present on patient awakening. Obstructive sleep apnea (OSA) is a major risk factor for WUS because it compounds the instability of the morning environment and increases the likelihood of cardiovascular events, including hypertension, atrial fibrillation, right-to-left shunts, and stroke. Circadian-driven alterations in structural, homeostatic, and serological factors also predispose to WUS. Also, WUS patients are often not considered candidates for time-dependent intravenous thrombolysis therapy because of an uncertain onset time. However, using the tissue clock (positive diffusion weighted imaging-negative fluid-attenuated inversion recovery mismatch) dates the WUS as 3 to 4.5 hours old and permits consideration for intravenous thrombolysis and if needed mechanical thrombectomy. Given the high prevalence of moderate/severe OSA in stroke patients and its impact on stroke outcomes, screening with overnight pulse oximetry and home sleep apnea test is needed. Treating OSA poststroke remains challenging. Polysomnographic changes in sleep architecture following acute/subacute stroke may also impact upon stroke outcome.

Recovery of consolidation after sleep following stroke-interaction of slow waves, spindles, and GABA

Sleep is known to promote recovery after stroke. Yet it remains unclear how stroke affects neural processing during sleep. Using an experimental stroke model in rats along with electrophysiological monitoring of neural firing and sleep microarchitecture, here we show that sleep processing is altered by stroke. We find that the precise coupling of spindles to global slow oscillations (SOs), a phenomenon that is known to be important for memory consolidation, is disrupted by a pathological increase in "isolated" local delta waves. The transition from this pathological to a physiological state-with increased spindle coupling to SO-is associated with sustained performance gains during recovery. Interestingly, post-injury sleep could be pushed toward a physiological state via a pharmacological reduction of tonic γ-aminobutyric acid (GABA). Together, our results suggest that sleep processing after stroke is impaired due to an increase in delta waves and that its restoration can be important for recovery.

Slow Waves Promote Sleep-Dependent Plasticity and Functional Recovery after Stroke

Functional recovery after stroke is associated with a remapping of neural circuits. This reorganization is often associated with low-frequency, high-amplitude oscillations in the peri-infarct zone in both rodents and humans. These oscillations are reminiscent of sleep slow waves (SW) and suggestive of a role for sleep in brain plasticity that occur during stroke recovery; however, direct evidence is missing. Using a stroke model in male mice, we showed that stroke was followed by a transient increase in NREM sleep accompanied by reduced amplitude and slope of ipsilateral NREM sleep SW. We next used 5 ms optical activation of Channelrhodopsin 2-expressing pyramidal neurons, or 200 ms silencing of Archeorhodopsin T-expressing pyramidal neurons, to generate local cortical UP, or DOWN, states, respectively, both sharing similarities with spontaneous NREM SW in freely moving mice. Importantly, we found that single optogenetically evoked SW (SWopto) in the peri-infarct zone, randomly distributed during sleep, significantly improved fine motor movements of the limb corresponding to the sensorimotor stroke lesion site compared with spontaneous recovery and control conditions, while motor strength remained unchanged. In contrast, SWopto during wakefulness had no effect. Furthermore, chronic SWopto during sleep were associated with local axonal sprouting as revealed by the increase of anatomic presynaptic and postsynaptic markers in the peri-infarct zone and corresponding contralesional areas to cortical circuit reorganization during stroke recovery. These results support a role for sleep SW in cortical circuit plasticity and sensorimotor recovery after stroke and provide a clinically relevant framework for rehabilitation strategies using neuromodulation during sleep.SIGNIFICANCE STATEMENT Brain stroke is one of the leading causes of death and major disabilities in the elderly worldwide. A better understanding of the pathophysiological mechanisms underlying spontaneous brain plasticity after stroke, together with an optimization of rehabilitative strategies, are essential to improve stroke treatments. Here, we investigate the role of optogenetically induced sleep slow waves in an animal model of ischemic stroke and identify sleep as a window for poststroke intervention that promotes neuroplasticity and facilitates sensorimotor recovery.

Sleep Disruption After Brain Injury Is Associated With Worse Motor Outcomes and Slower Functional Recovery

Background. Sleep is important for consolidation of motor learning, but brain injury may affect sleep continuity and therefore rehabilitation outcomes. Objective. This study aims to assess the relationship between sleep quality and motor recovery in brain injury patients receiving inpatient rehabilitation. Methods. Fifty-nine patients with brain injury were recruited from 2 specialist inpatient rehabilitation units. Sleep quality was assessed (up to 3 times) objectively using actigraphy (7 nights) and subjectively using the Sleep Condition Indicator. Motor outcome assessments included Action Research Arm test (upper limb function), Fugl-Meyer Assessment (motor impairment), and the Rivermead Mobility Index. The Functional Independence Measure (FIM) was assessed at admission and discharge by the clinical team. Fifty-five age- and gender-matched healthy controls completed one assessment. Results. Inpatients demonstrated lower self-reported sleep quality (P < .001) and more fragmented sleep (P < .001) than controls. For inpatients, sleep fragmentation explained significant additional variance in motor outcomes, over and above that explained by admission FIM score (P < .017), such that more disrupted sleep was associated with poorer motor outcomes. Using stepwise linear regression, sleep fragmentation was the only variable found to explain variance in rate of change in FIM (R²_adj = 0.12, P = .027), whereby more disrupted sleep was associated with slower recovery. Conclusions. Inpatients with brain injury demonstrate impaired sleep quality, and this is associated with poorer motor outcomes and slower functional recovery. Further investigation is needed to determine how sleep quality can be improved and whether this affects outcome.

Influence of rapid eye movement sleep on all-cause mortality: a community-based cohort study

Introduction: Although the proportion and duration of rapid eye movement (REM) sleep are correlated with neurological and cardiovascular diseases, whether REM sleep is associated with all-cause mortality in community-based populations remains unknown.

Methods: A prospective study was performed within the Sleep Heart Health Study (SHHS, Registration NO. NCT00005275). Total sleep time, sleep efficiency, and REM sleep were measured using polysomnography. Cox proportional hazards regression models were used to estimate the association of the REM sleep with all-cause mortality.

Results: Over a mean follow-up period of 11.0 ± 3.1 y, 1234 individuals (21.9%) died. In the entire population, reduced REM sleep was significantly associated with increasing all-cause mortality. After adjustment for age, sex, race, body mass index, smoking status, total cholesterol, triglycerides, high-density lipoprotein, history of diabetes and hypertension, and the apnea–hypopnea index, the duration and proportion of REM sleep were found to be significantly associated with all-cause mortality when the lowest and the highest REM quartile groups were compared (hazard ratio, 95% confidence interval: 1.727, 1.434-2.079; 1.545, 1.298-1.839; respectively).

Conclusion: The proportion and duration of REM sleep are negatively associated with all-cause mortality. This finding emphasizes the importance of personalized sleep management in community-based populations.

Postoperative sleep disorders and their potential impacts on surgical outcomes

Postoperative sleep disturbance is a common occurrence with significant adverse effects on patients including delayed recovery, impairment of cognitive function, pain sensitivity and cardiovascular events. The development of postoperative sleep disturbance is multifactorial and involves the surgical inflammatory response, the severity of surgical trauma, pain, anxiety, the use of anesthetics and environmental factors such as nocturnal noise and light levels. Many of these factors can be managed perioperatively to minimize the deleterious impact on sleep. Pharmacological and non-pharmacological treatment strategies for postoperative sleep disturbance include dexmedetomidine, zolpidem, melatonin, enhanced recovery after surgery (ERAS) protocol and controlling of environmental noise and light levels. It is likely that a combination of pharmacological and non-pharmacological therapies will have the greatest impact; however, further research is required before their use can be routinely recommended.

Role of REM Sleep, Melanin Concentrating Hormone and Orexin/Hypocretin Systems in the Sleep Deprivation Pre-Ischemia

STUDY OBJECTIVES

Sleep reduction after stroke is linked to poor recovery in patients. Conversely, a neuroprotective effect is observed in animals subjected to acute sleep deprivation (SD) before ischemia. This neuroprotection is associated with an increase of the sleep, melanin concentrating hormone (MCH) and orexin/hypocretin (OX) systems. This study aims to 1) assess the relationship between sleep and recovery; 2) test the association between MCH and OX systems with the pathological mechanisms of stroke.

METHODS

Sprague-Dawley rats were assigned to four experimental groups: (i) SD_IS: SD performed before ischemia; (ii) IS: ischemia; (iii) SD_Sham: SD performed before sham surgery; (iv) Sham: sham surgery. EEG and EMG were recorded. The time-course of the MCH and OX gene expression was measured at 4, 12, 24 hours and 3, 4, 7 days following ischemic surgery by qRT-PCR.

RESULTS

A reduction of infarct volume was observed in the SD_IS group, which correlated with an increase of REM sleep observed during the acute phase of stroke. Conversely, the IS group showed a reduction of REM sleep. Furthermore, ischemia induces an increase of MCH and OX systems during the acute phase of stroke, although, both systems were still increased for a long period of time only in the SD_IS group.

CONCLUSIONS

Our data indicates that REM sleep may be involved in the neuroprotective effect of SD pre-ischemia, and that both MCH and OX systems were increased during the acute phase of stroke. Future studies should assess the role of REM sleep as a prognostic marker, and test MCH and OXA agonists as new treatment options in the acute phase of stroke.

The role of sleep in recovery following ischemic stroke: A review of human and animal data

Despite advancements in understanding the pathophysiology of stroke and the state of the art in acute management of afflicted patients as well as in subsequent neurorehabilitation training, stroke remains the most common neurological cause of long-term disability in adulthood. To enhance stroke patients' independence and well-being it is necessary, therefore, to consider and develop new therapeutic strategies and approaches. We postulate that sleep might play a pivotal role in neurorehabilitation following stroke. Over the last two decades compelling evidence for a major function of sleep in neuroplasticity and neural network reorganization underlying learning and memory has evolved. Training and learning of new motor skills and knowledge can modulate the characteristics of subsequent sleep, which additionally can improve memory performance. While healthy sleep appears to support neuroplasticity resulting in improved learning and memory, disturbed sleep following stroke in animals and humans can impair stroke outcome. In addition, sleep disorders such as sleep disordered breathing, insomnia, and restless legs syndrome are frequent in stroke patients and associated with worse recovery outcomes. Studies investigating the evolution of post-stroke sleep changes suggest that these changes might also reflect neural network reorganization underlying functional recovery. Experimental and clinical studies provide evidence that pharmacological sleep promotion in rodents and treatment of sleep disorders in humans improves functional outcome following stroke. Taken together, there is accumulating evidence that sleep represents a "plasticity state" in the process of recovery following ischemic stroke. However, to test the key role of sleep and sleep disorders for stroke recovery and to better understand the underlying molecular mechanisms, experimental research and large-scale prospective studies in humans are necessary. The effects of hospital conditions, such as adjusting light conditions according to the patients' sleep-wake rhythms, or sleep promoting drugs and non-invasive brain stimulation to promote neuronal plasticity and recovery following stroke requires further investigation.

Polysomnographic Characteristics of Sleep in Stroke: A Systematic Review and Meta-Analysis

BACKGROUND

Research on sleep after stroke has focused mainly on sleep disordered breathing. However, the extend to which sleep physiology is altered in stroke survivors, how these alterations compare to healthy volunteers, and how sleep changes might affect recovery as well as physical and mental health has yet to be fully researched. Motivated by the view that a deeper understanding of sleep in stroke is needed to account for its role in health and well-being as well as its relevance for recovery and rehabilitation, we conducted a systematic review and meta-analysis of polysomnographic studies comparing stroke to control populations.

METHOD

Medline and PsycInfo databases were searched using "stroke" and words capturing polysomnographic parameters as search terms. This yielded 1692 abstracts for screening, with 15 meeting the criteria for systematic review and 9 for meta-analysis. Prisma best practice guidelines were followed for the systematic review; the Comprehensive Meta-Analysis software was used for random effects modelling.

RESULTS

The meta-analysis revealed that patients with stroke have poorer sleep than controls. Patients had lower sleep efficiency (mean 75% vs 84%), shorter total-sleep-time (309.4 vs 340.3 min) and more wake-after-sleep-onset (97.2 vs 53.8 min). Patients also spend more time in stage 1 (13% vs 10%) and less time in stage 2 sleep (36% vs 45%) and slow-wave-sleep (10% vs 12%). No group differences were identified for REM sleep. The systematic review revealed a strong bias towards studies in the early recovery phase of stroke, with no study reporting specifically on patients in the chronic state. Moreover, participants in the control groups included community samples as well as other patients groups.

CONCLUSIONS

These results indicate poorer sleep in patients with stroke than controls. While strongly suggestive in nature, the evidence base is limited and methodologically diverse, and hands a clear mandate for further research. A particular need regards polysomnographic studies in chronic community-dwelling patients compared to age-matched individuals.

Sleep Parameters, Functional Status, and Time Post-Stroke are Associated with Offline Motor Skill Learning in People with Chronic Stroke

BACKGROUND

Mounting evidence demonstrates that individuals with stroke benefit from sleep to enhance learning of a motor task. While stage NREM2 sleep and REM sleep have been associated with offline motor skill learning in neurologically intact individuals, it remains unknown which sleep parameters or specific sleep stages are associated with offline motor skill learning in individuals with stroke.

METHODS

Twenty individuals with chronic stroke (>6 months following stroke) and 10 control participants slept for three consecutive nights in a sleep laboratory with polysomnography. Participants practiced a tracking task the morning before the third night and underwent a retention test the morning following the third night. Offline learning on the tracking task was assessed. Pearson's correlations assessed for associations between the magnitude of offline learning and sleep variables, age, upper-extremity motor function, stroke severity, depression, and time since stroke occurrence.

RESULTS

Individuals with stroke performed with significantly less error on the tracking task following a night of sleep (p = 0.006) while the control participants did not (p = 0.816). Increased sleep efficiency (r = -0.285), less time spent in stage NREM3 sleep (r = 0.260), and more time spent in stage REM sleep (r = -0.266) were weakly-to-moderately associated with increased magnitude of offline motor learning. Furthermore, higher upper-extremity motor function (r = -0.400), lower stroke severity (r = 0.360), and less time since stroke occurrence (r = 0.311) were moderately associated with increased magnitude of offline motor learning.

CONCLUSION

This study is the first study to provide insight into which sleep stages and individual characteristics may be associated with offline learning in people with stroke. Further research is needed to delineate which factors or combination of factors promote offline motor learning in people with neurologic injury to best promote motor recovery in these individuals.

Action observation as a tool for neurorehabilitation to moderate motor deficits and aphasia following stroke

The mirror neuron system consists of a set of brain areas capable of matching action observation with action execution. One core feature of the mirror neuron system is the activation of motor areas by action observation alone. This unique capacity of the mirror neuron system to match action perception and action execution stimulated the idea that mirror neuron system plays a crucial role in the understanding of the content of observed actions and may participate in procedural learning. These features bear a high potential for neurorehabilitation of motor deficits and of aphasia following stroke. Since the first articles exploring this principle were published, a growing number of follow-up studies have been conducted in the last decade. Though, the combination of action observation with practice of the observed actions seems to constitute the most powerful approach. In the present review, we present the existing studies analyzing the effects of this neurorehabilitative approach in clinical settings especially in the rehabilitation of stroke associated motor deficits and give a perspective on the ongoing trials by our research group. The data obtained up to date showed significant positive effect of action observation on recovery of motor functions of the upper limbs even in the chronic state after stroke, indicating that our approach might become a new standardized add-on feature of modern neurorehabilitative treatment schemes.

Sleep characteristics of individuals with chronic stroke: a pilot study

Changes in sleep characteristics in individuals with chronic stroke are not well described, particularly compared with healthy individuals. Therefore, the aim of this pilot study was to explore the sleep characteristics in individuals with chronic stroke compared to age- and sex-matched controls. Sixteen individuals with chronic stroke and ten age- and sex-matched controls underwent two nights of polysomnographic recording. The sleep characteristics of interest included total sleep time, sleep efficiency, and percent time, as well as time in minutes spent in stages N1, N2, and N3 and stage R sleep. The individuals with chronic stroke spent less percent time in stage N3 compared with controls (P=0.048). No significant differences in the other sleep characteristics were found between the stroke and control groups. Individuals with chronic stroke present with altered stage N3 sleep compared with healthy controls. These alterations in stage N3 sleep might be a sign of neuronal dysfunction and may impact recovery following stroke. A larger scale study is needed to confirm these findings.

Nocturnal deterioration after ischemic stroke and autonomic dysfunction: hypothesis and implications

BACKGROUND

A significant number of patients admitted to hospital after acute ischemic stroke deteriorate clinically. Deterioration is generally noted within the first 48 h after stroke onset. The mechanisms leading to this deterioration are not fully understood.

SUMMARY

One potential cause of this deterioration may be altered or impaired autonomic function. We expect the hemodynamic changes regulated by the autonomic nervous system that are dysregulated after stroke to be exaggerated during sleep, resulting in arrhythmia and blood pressure fluctuations in these patients. Such physiological changes could result in worsening the overall outcome of the ischemic stroke patient or in sudden death. Therefore, it is necessary to summarize yet unrelated observations and hypothesize on their individual effects and interactions as they relate to poststroke deterioration.

KEY MESSAGES

If the hypothesis is correct that dysautonomia occurs to the degree that it affects clinical outcomes negatively, this would have important implications for the prevention of neurological deterioration and sudden death after ischemic stroke.

Ischemic stroke selectively inhibits REM sleep of rats

Sleep disorders are important risk factors for stroke; conversely, stroke patients suffer from sleep disturbances including disruptions of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep and a decrease in total sleep. This study was performed to characterize the effect of stroke on sleep architecture of rats using continuous electroencephalography (EEG) and activity monitoring. Rats were implanted with transmitters which enabled continuous real time recording of EEG, electromyography (EMG), and locomotor activity. Baseline recordings were performed prior to induction of either transient middle cerebral artery (MCA) occlusion or sham surgery. Sleep recordings were obtained for 60 h after surgery to identify periods of wakefulness, NREM, and REM sleep before and after stroke. Spectral analysis was performed to assess the effects of stroke on state-dependent EEG. Finally, we quantified the time in wake, NREM, and REM sleep before and after stroke. Delta power, a measure of NREM sleep depth, was increased the day following stroke. At the same time, there was a significant shift in theta rhythms to a lower frequency during REM and wake periods. The awake EEG slowed after stroke over both hemispheres. The EEG of the ischemic hemisphere demonstrated diminished theta power specific to REM in excess of the slowing seen over the contralateral hemisphere. In contrast to rats exposed to sham surgery which had slightly increased total sleep, rats undergoing stroke experienced decreased total sleep. The decrease in total sleep after stroke was the result of dramatic reduction in the amount of REM sleep after ischemia. The suppression of REM after stroke was due to a decrease in the number of REM bouts; the length of the average REM bout did not change. We conclude that after stroke in this experimental model, REM sleep of rats is specifically and profoundly suppressed. Further experiments using this experimental model should be performed to investigate the mechanisms and consequences of REM suppression after stroke.

Strokes and their relationship with sleep and sleep disorders

INTRODUCTION

In the current population, strokes are one of the most important causes of morbidity and mortality, to which new risk factors are increasingly being attributed. Of late, there is increased interest in the relationship between sleep disorders and strokes as regards risk and prognosis.

DEVELOPMENT

This article presents the changes in sleep architecture and brain activity in stroke patients, as well as the interaction between stroke and sleep disorders, including those which may also influence the outcome and recovery from strokes. The different treatments discussed in the literature are also reviewed, as correct treatment of such sleep disorders may not only improve quality of life and reduce after-effects, but can also increase life expectancy.

CONCLUSIONS

Sleep disorders are becoming increasingly associated with stroke. In addition to being a risk factor, they can also interfere in the outcome and recovery of stroke patients. This article aims to present an exhaustive and current review on strokes and their relationship with sleep alterations and sleep disorders.

Spontaneous arm movement activity assessed by accelerometry is a marker for early recovery after stroke

The factors determining recovery from hemiparetic stroke are manifold. We studied spontaneous arm movement activity in the acute phase after stroke as a predictor of recovery. Included in this prospective study were 25 patients (63 ± 10 years; 9 women, 16 men) with acute middle cerebral artery stroke and 7 control patients without neurological disease (61 ± 14 years; 3 women, 4 men). Movement activity was measured continuously for 4 days in both arms using Actiwatches and analysed off-line. Movement activity of the nonaffected arm ranged from <10 to >16 h per day in the stroke patients. Nine stroke patients with an initial decline in arm movement activity showed no increase in movement activity in either arm over 4 days after stroke, and the other 16 patients improved steadily after admission (p < 0.003). C-reactive protein was elevated in the non-recovering patients (4.4 ± 4.9 mg/dl) related to a low number of waking hours (r = -0.512, p < 0.01). Stroke severity, location and treatment, as well as arterial blood pressure (162 ± 21 mmHg) and body temperature (36.9 ± 06 °C) were not different among the groups. The impairment was still different among the two groups 3 months after stroke. Our results support the notion that in the acute stage after middle cerebral artery stroke there are patients with a secondary decline in general motor activity related to an enhanced sleep demand as assessed with accelerometry. This impairment was related to elevated C-reactive protein.

Does sleep promote motor learning? Implications for physical rehabilitation

Sleep following motor skill practice has repeatedly been demonstrated to enhance motor skill learning off-line (continued overnight improvements in motor skill that are not associated with additional physical practice) for young people who are healthy. Mounting evidence suggests that older people who are healthy fail to demonstrate sleep-dependent off-line motor learning. However, little is known regarding the influence of sleep on motor skill enhancement following damage to the brain. Emerging evidence suggests that individuals with brain damage, particularly following stroke, do benefit from sleep to promote off-line motor skill learning. Because rehabilitation following stroke requires learning new, and re-learning old, motor skills, awareness that individuals with stroke benefit from a period of sleep following motor skill practice to enhance skill learning could affect physical therapist practice. The objective of this article is to present the evidence demonstrating sleep-dependent off-line motor learning in young people who are healthy and the variables that may influence this beneficial sleep-dependent skill enhancement. In young people who are healthy, these variables include the stages of memory formation, the type of memory, the type of instruction provided (implicit versus explicit learning), and the task utilized. The neural mechanisms thought to be associated with sleep-dependent off-line motor learning also are considered. Research examining whether older adults who are healthy show the same benefits of sleep as do younger adults is discussed. The data suggest that older adults who are healthy do not benefit from sleep to promote off-line skill enhancement. A possible explanation for the apparent lack of sleep-dependent off-line motor learning by older adults who are healthy is presented. Last, emerging evidence showing that individuals with chronic stroke demonstrate sleep-dependent off-line motor skill learning and some of the possible mechanisms for this effect are considered.

Correlation between sleep and cognitive functions after hemispheric ischaemic stroke

BACKGROUND

The aim of this study was to test the hypothesis of a link between sleep and cognitive functions, particularly memory and attention, after stroke.

METHODS

We studied 11 consecutive patients with first-ever hemispheric ischaemic stroke within eight days after symptoms onset and nine of them at least three months after stroke. Sleep EEG was recorded with a portable system. Cognitive functions were assessed using a standardized battery of tests allowing the estimation of the most relevant domains of cognition. Five age-matched healthy subjects served as controls.

RESULTS

The patients were aged 43 +/- 12 years (18-59). In five patients stroke was right-sided and in six patients left-sided. In the acute stroke phase a correlation between attention and amounts of slow wave sleep (SWS), Rapid eye movement (REM) sleep and sleep efficiency was found. In the recovery phase verbal/figural memory and attention significantly improved in most patients. Furthermore, an association between (i) verbal/figural (non-verbal) memory and amounts of SWS, REM sleep and sleep efficiency, and between (ii) attention and sleep efficiency was observed.

CONCLUSIONS

The results point to a link between sleep and cognitive functions and their recovery after hemispheric stroke. Further studies are needed to determine the specific nature of this link.

Cerebrovascular disease and sleep

Sleep is a function of the brain and sleep affects brain function, contributing to cerebral pathology through a diversity of direct and indirect mechanisms. Sleep-disordered breathing (SDB) is a very common disorder and is the major sleep-related risk factor for cerebrovascular disease. Epidemiologic studies have shown a dose-response relationship between the severity of SDB and the odds ratio for development of systemic hypertension. Following stroke, both in the acute and chronic stages, patients have a high prevalence of SDB that reduces the potential for rehabilitation, further increases the risk of secondary stroke, and heightens mortality. There is proof that successful correction of SDB with noninvasive positive airway pressure ventilation lowers mean blood pressure. In patients with advanced SDB, altered cerebral evoked potentials are not corrected with applications of noninvasive ventilation, suggesting permanent cerebral structural damage. This is supported by reports of increased leukoaraiosis in patients with advanced SDB. Circadian changes during sleep may increase the risk of both cardiovascular and cerebrovascular accidents.

Power and coherence of sleep spindle frequency activity following hemispheric stroke

Brainstem and thalamic structures are known to play a critical role in modulating sleep-wake cycles, but the extent to which the cerebral hemispheres are involved remains unclear. To study the role of the cerebral hemispheres in generating sleep EEG patterns, all-night polysomnographic recordings were collected in subjects with brain damage (n = 30) caused by hemispheric stroke and in hospitalized controls (n = 12). Recordings were made in the acute (< or =10 days post-stroke), subchronic (11-35 days post-stroke) and chronic (>60 days post-stroke) phases of stroke. Bipolar and referential EEG derivations were recorded. Standard sleep stage scoring was conducted using the referential derivation placed opposite the lesion. Sleep stage 2 power and coherence spectra were calculated based on recordings from bipolar derivations. In the mean spectra, the highest spindle frequency peak was identified and its size was calculated relative to the background spectrum. Analysis of visually scored EEG data indicated that, compared with controls, acute phase brain-damaged subjects had lower sleep efficiency and increased waking after sleep onset. The durations of rapid eye movement and non-rapid eye movement sleep stages did not differ significantly between brain-damaged subjects and hospitalized controls. Spectral analyses revealed that, compared with hospitalized controls, brain-damaged subjects had significantly reduced spindle peak sizes in the power and coherence spectra from derivations ipsilateral to the lesion. Within-subject comparisons across time demonstrated that the power and coherence of sleep spindle frequency activity increased significantly from the acute to the chronic phases of stroke, suggesting that plastic mechanisms allowed the possibility of recovery. Our findings provide novel evidence that the cerebral hemispheres are important in generating coherent sleep spindles in humans, and they are consonant with prior empirical and theoretical evidence that corticothalamic projections modulate the generation of synchronous spindle oscillations. Because spindle oscillations are thought to be involved in blocking sensory input to the cortex during sleep, the decrease in synchronous spindle frequency activity following hemispheric stroke may contribute to the observed reduction in sleep continuity.

Sleep and brain lesions: a critical review of the literature and additional new cases

We present a comprehensive review of sleep studies performed in patients with brain lesions complemented by 16 additional personal selected cases and by discussion of the corresponding animal data. The reader is cautioned about the risk of establishing an erroneous correlation between abnormal sleep and a given disorder due to the important inter and intra variability of sleep parameters among individuals. Salient points are stressed: the high frequency of post-stroke sleep breathing disorders is becoming increasingly recognised and may, in the near future, change the way this condition is managed. Meso-diencephalic bilateral infarcts induce a variable degree of damage to both waking and non-REM sleep networks producing and abnormal waking and sometimes a stage 1 hypersomnia reduced by modafinil or bromocriptine, which can be considered as a syndrome of cathecholaminergic deficiency. Central pontine lesions induce REM and non-REM sleep insomnia with bilateral lateral gaze paralysis. Bulbar stroke leads to frequent sleep breathing disorders. Polysomnography can help define the extent of involvement of various degenerative diseases. Fragmented sleep in Parkinson's disease may be preceded by REM sleep behavioural disorders. Multiple system atrophies are characterised by important sleep disorganization. Sleep waking disorganization and a specific ocular REM pattern are often seen in supra-nuclear ophtalmoplegia. In Alzheimer patients, sleep perturbations parallel the mental deterioration and are possibly related to cholinergic deficiency. Fronto-temporal dementia may be associated with an important decrease in REM sleep. Few narcoleptic syndromes are reported to be associated with a tumour of the third ventricle or a multiple sclerosis or to follow a brain trauma; all these cases raise the question whether this is a simple coincidence, a revelation of a latent narcolepsy or, as in non-DR16/DQ5 patients, a genuine symptomatic narcolepsy. Trypanosomiasis and the abnormal prion protein precociously after sleep patterns. Polysomnography is a precious tool for evaluating brain function provided it is realised under optimal conditions in stable patients and interpreted with caution. Several unpublished cases are presented: one case of pseudohypersomnia due to a bilateral thalamic infarct and corrected by modafinil, four probable late-onset autosomal recessive cerebellar ataxias without sleep pattern anomalies, six cases of fronto-temporal dementia with strong reduction in total sleep time and REMS percentage on the first polysomnographic night, one case of periodic hypersomnia associated with a Rathke's cleft cyst and four cases of suspected symptomatic narcolepsy with a DR16-DQ5 haplotype, three of which were post-traumatic without MRI anomalies, and one associated with multiple sclerosis exhibiting pontine hyper signals on MRI.

Sleep electroencephalogram changes in acute hemispheric stroke

Background/objective: Since reports of the effects of cerebral hemispheric stroke on sleep architecture are rare and contradictory, we prospectively studied 24 patients with first acute supratentorial, extra-thalamic stroke.Methods: We assessed stroke severity, topography, and volume (on brain MRI). Sleep electroencephalogram recordings were performed a mean of 12 days after stroke onset, and scored for sleep stages over the healthy hemisphere. Sleep spindles and sawtooth waves were analyzed over both hemispheres. Data were compared with those of 17 age and gender-matched patients with normal brain imaging.Results: Compared to controls, stroke patients had lower total sleep time (P<0.01), lower sleep efficiency (P=0.02), and reduced amounts of NREM sleep stages 2-4 (P=0.02). Sleep spindles and sawtooth waves were often bilaterally reduced in patients with stroke volumes >25 ml. Abnormalities of REM sleep were more common in sleep studies performed within 3 days after stroke onset. Compared to patients with poor outcome, those with good outcome had higher sleep efficiency (P<0.01), more sleep time (P=0.02), and more NREM sleep stage 2 (P<0.01).Conclusion: Acute hemispheric stroke is accompanied by sleep EEG changes over the healthy hemisphere that correlate with stroke severity. These findings support the hypothesis that the cerebral hemispheres participate in the control of sleep.

Sleep disturbances after non-cardiac surgery

After major non-cardiac surgery sleep pattern is usually disturbed with initial suppression of rapid eye movement sleep with a subsequent rebound during the first post-operative week. Deep sleep is also suppressed for several days after the operation and subjective sleep quality is impaired. The sleep disturbances seem to be related to the magnitude of trauma and thereby to the surgical stress response and/or post-operative opioid administration. Post-operative sleep disturbances may contribute to the development of early post-operative fatigue, episodic hypoxaemia, haemodynamic instability and altered mental status, all with a potential negative effect on post-operative outcome. Minimizing surgical trauma and avoiding or minimizing use of opioids for pain relief may prevent or reduce post-operative sleep disturbances. Post-operative sleep pattern represents an important research field, since it may have a significant negative on post-operative outcome. 2001 Harcourt Publishers Ltd

Rapid eye movements during paradoxical sleep in patients with cerebrovascular disease

Rapid eye movements that occur during paradoxical sleep are generated from the brainstem and are modulated by cerebral hemispheres. In an attempt to establish the participation of cerebral hemispheres on rapid eye movements, we carried out a quantitative study of eye movements density in patients bearing hemispheres vascular lesions. The polysomnographic recordings of 24 patients were compared to those of 24 healthy volunteers. Density of rapid eye movements was defined as the percentage of eye movements during the respective time of paradoxical sleep. Based on the present results, we concluded that: stroke patients with hemispheric lesions displayed increased density of rapid eye movements; there was no difference on the density of rapid eye movements according to the hemispheric lesion; higher density of rapid eye movements was observed in patients with anterior hemispheric lesion.

Fatigue after stroke

OBJECTIVE

To determine the frequency and outcome of fatigue, its impact on functioning, and its relationship with depression in patients 3 to 13 months poststroke.

DESIGN

Survey.

SETTING

Community.

PARTICIPANTS

Eighty-eight individuals from a pool of 181 consecutive patients previously admitted to an acute stroke service who were willing and able to complete the self-report questionnaires, and 56 elderly controls living independently in the community.

MAIN OUTCOME MEASURES

Fatigue Impact Scale (a self-report measure of the presence and severity of fatigue and its impact on cognitive, physical, and psychosocial functions) and the Geriatric Depression Scale.

RESULTS

The frequency of self-reported fatigue problems was greater in the stroke group (68%) than in the control group (36%, p < .001) and was not related to time poststroke, stroke severity, or lesion location. Forty percent of the stroke group reported that fatigue was either their worst or one of their worst symptoms. Patients attributed more functional limitations to their fatigue than did control subjects with fatigue. Although the presence of fatigue was independent of depression, the impact of fatigue on functional abilities was strongly influenced by depression.

CONCLUSION

Fatigue can contribute to functional impairment up to 13 months after stroke, and its recognition and treatment are important for maximizing recovery.

Sleep apnea in patients with hemispheric stroke

Sleep pattern and breathing in humans are altered following cerebrovascular accidents involving the brainstem. Sleep apnea is a well-established complication of stroke involving the brainstem. On the other hand, the effect of cerebral stroke on sleep and breathing has not been well defined. The diffuse cerebral symptoms such as cognitive deficits, depression or fatigue, after hemispheric stroke mimic those present in patients with sleep apnea. To define the breathing pattern in patients with stroke involving cerebral hemispheres without brainstem lesion and without the prior history of sleep-disordered breathing, we studied 10 patients within 1 year of their stroke. The data collected during polysomnography from the stroke patients were compared with a group of subjects matched for age, body mass index, presence of hypertension, and smoking history without stroke. Patients with stroke had an abnormal sleep architecture with significantly lower slow wave sleep and rapid eye movement (REM) sleep when compared with controls. Sleep was fragmented because of the presence of increased respiratory disturbances. Stroke patients had a respiratory disturbance index of 52 +/- 10 events per hour when compared with 3 +/- 1 in controls (p < .05). Majorities of respiratory events were obstructive apneas and were associated with arterial oxygen desaturations and arousals. The pathogenic mechanism of sleep-disordered breathing in patients with hemispheric stroke seems to be related to the physiological effect of sleep on already compromised upper airway muscle control. Patients with stroke and diffuse cerebral symptoms should be investigated for the possibility of sleep-disordered breathing.