Circadian variation in ischemic stroke subtypes

Circadian and Diurnal Regulation of Cerebral Blood Flow

Circadian and diurnal variation in cerebral blood flow directly contributes to the diurnal variation in the risk of stroke, either through factors that trigger stroke or due to impaired compensatory mechanisms. Cerebral blood flow results from the integration of systemic hemodynamics, including heart rate, cardiac output, and blood pressure, with cerebrovascular regulatory mechanisms, including cerebrovascular reactivity, autoregulation, and neurovascular coupling. We review the evidence for the circadian and diurnal variation in each of these mechanisms and their integration, from the detailed evidence for mechanisms underlying the nocturnal nadir and morning surge in blood pressure to identifying limited available evidence for circadian and diurnal variation in cerebrovascular compensatory mechanisms. We, thus, identify key systemic hemodynamic factors related to the diurnal variation in the risk of stroke but particularly identify the need for further research focused on cerebrovascular regulatory mechanisms.

Ruscogenin timing administration mitigates cerebral ischemia-reperfusion injury through regulating circadian genes and activating Nrf2 pathway

BACKGROUND

Ruscogenin (Rus), a steroidal sapogenin extracted from Ophiopogon japonicus (L. f.) Ker-Gawl., has the effect of alleviating cerebral ischemia-reperfusion injury (IRI), acute lung injury. At present, the chronopharmacological effects of Rus are still unknown.

PURPOSE

This study explored the alleviating effect and mechanism of Rus timing administration on mice cerebral IRI.

METHODS

The animals in different groups were administrated Rus (10 mg/kg) by gavage at four time points (23:00-01:00, 05:00-07:00, 11:00-13:00, 17:00-19:00) respectively for 3 days. On the 4th day, middle cerebral artery occlusion (MCAO) surgery was operated during 5:00-7:00. Behavioral tests were executed and the brain was collected for infarct volume, qPCR and immunoblot detection. The levels of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), interleukin-1beta (IL-1β) and inducible nitric oxide synthase (iNOS) were detected by qPCR. Glutathione (GSH), superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in serum and cerebral cortex were detected. The clock genes were tested by western blot. Based on these results, 17:00-19:00 was selected to administrate Rus for further mechanism study and Nrf2 blocker group was administrated all-trans-retinoic acid (ATRA) at 14:00 for 3 days.

RESULTS

Administration of Rus reduced cerebral infarcted volume, ameliorated the behavior score and upregulated the mRNA and protein expression of Per1, Bmal1, Clock, Rev-erbα, transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), quinone oxidoreductase 1 (NQO1). Administration of Rus during 17:00-19:00 had better preventive effect than other three time points. Combined administration of ATRA blunted the preventive effect of Rus.

CONCLUSION

The preventive effect of Rus is affected by the time of administration, which was regulated by Nrf2 pathway. Taken together, we provide solid evidence to suggest that different administration time point affect the effectiveness of Rus in alleviating IRI.

Development of circadian neurovascular function and its implications

The neurovascular system forms the interface between the tissue of the central nervous system (CNS) and circulating blood. It plays a critical role in regulating movement of ions, small molecules, and cellular regulators into and out of brain tissue and in sustaining brain health. The neurovascular unit (NVU), the cells that form the structural and functional link between cells of the brain and the vasculature, maintains the blood-brain interface (BBI), controls cerebral blood flow, and surveils for injury. The neurovascular system is dynamic; it undergoes tight regulation of biochemical and cellular interactions to balance and support brain function. Development of an intrinsic circadian clock enables the NVU to anticipate rhythmic changes in brain activity and body physiology that occur over the day-night cycle. The development of circadian neurovascular function involves multiple cell types. We address the functional aspects of the circadian clock in the components of the NVU and their effects in regulating neurovascular physiology, including BBI permeability, cerebral blood flow, and inflammation. Disrupting the circadian clock impairs a number of physiological processes associated with the NVU, many of which are correlated with an increased risk of dysfunction and disease. Consequently, understanding the cell biology and physiology of the NVU is critical to diminishing consequences of impaired neurovascular function, including cerebral bleeding and neurodegeneration.

Elevated Hypoperfusion Intensity Ratio (HIR) observed in patients with a large vessel occlusion (LVO) presenting in the evening

BACKGROUND

Circadian variability has been implicated in timing of stroke onset, yet the full impact of underlying biological rhythms on acute stroke perfusion patterns is not known. We aimed to describe the relationship between time of stroke onset and perfusion profiles in patients with large vessel occlusion (LVO).

METHODS

A retrospective observational study was conducted using prospective registries of four stroke centers across North America and Europe with systematic use of perfusion imaging in clinical care. Included patients had stroke due to ICA, M1 or M2 occlusion and baseline perfusion imaging performed within 24h from last-seen-well (LSW). Stroke onset was divided into eight hour intervals: (1) Night: 23:00-6:59, (2) Day: 7:00-14:59, (3) Evening: 15:00-22:59. Core volume was estimated on CT perfusion (rCBF <30%) or DWI-MRI (ADC <620) and the collateral circulation was estimated with the Hypoperfusion Intensity Ratio (HIR = [Tmax>10s]/[Tmax>6s]). Non-parametric testing was conducted using SPSS to account for the non-normalized dependent variables.

RESULTS

A total of 1506 cases were included (median age 74.9 years, IQR 63.0-84.0). Median NIHSS, core volumes, and HIR were 14.0 (IQR 8.0-20.0), 13.0mL (IQR 0.0-42.0), and 0.4 (IQR 0.2-0.6) respectively. Most strokes occurred during the Day (n = 666, 44.2%), compared to Night (n = 360, 23.9%), and Evening (n = 480, 31.9%). HIR was highest, indicating worse collaterals, in the Evening compared to the other timepoints (p = 0.006). Controlling for age and time to imaging, Evening strokes had significantly higher HIR compared to Day (p = 0.013).

CONCLUSION

Our retrospective analysis suggests that HIR is significantly higher in the evening, indicating poorer collateral activation which may lead to larger core volumes in these patients.

The role of circadian clock in astrocytes: From cellular functions to ischemic stroke therapeutic targets

Accumulating evidence suggests that astrocytes, the abundant cell type in the central nervous system (CNS), play a critical role in maintaining the immune response after cerebral infarction, regulating the blood-brain barrier (BBB), providing nutrients to the neurons, and reuptake of glutamate. The circadian clock is an endogenous timing system that controls and optimizes biological processes. The central circadian clock and the peripheral clock are consistent, controlled by various circadian components, and participate in the pathophysiological process of astrocytes. Existing evidence shows that circadian rhythm controls the regulation of inflammatory responses by astrocytes in ischemic stroke (IS), regulates the repair of the BBB, and plays an essential role in a series of pathological processes such as neurotoxicity and neuroprotection. In this review, we highlight the importance of astrocytes in IS and discuss the potential role of the circadian clock in influencing astrocyte pathophysiology. A comprehensive understanding of the ability of the circadian clock to regulate astrocytes after stroke will improve our ability to predict the targets and biological functions of the circadian clock and gain insight into the basis of its intervention mechanism.

New insight into ischemic stroke: Circadian rhythm in post-stroke angiogenesis

The circadian rhythm is an endogenous clock system that coordinates and optimizes various physiological and pathophysiological processes, which accord with the master and the peripheral clock. Increasing evidence indicates that endogenous circadian rhythm disruption is involved in the lesion volume and recovery of ischemic stroke. As a critical recovery mechanism in post-stroke, angiogenesis reestablishes the regional blood supply and enhances cognitive and behavioral abilities, which is mainly composed of the following processes: endothelial cell proliferation, migration, and pericyte recruitment. The available evidence revealed that the circadian governs many aspects of angiogenesis. This study reviews the mechanism by which circadian rhythms regulate the process of angiogenesis and its contribution to functional recovery in post-stroke at the aspects of the molecular level. A comprehensive understanding of the circadian clock regulating angiogenesis in post-stroke is expected to develop new strategies for the treatment of cerebral infarction.

Wake-up strokes are linked to obstructive sleep apnea and worse early functional outcome

BACKGROUND AND AIMS

Presence of sleep-disordered breathing (SDB) and especially obstructive sleep apnea (OSA) is a known risk factor for ischemic stroke. Additionally, SDB effects negatively on recovery after stroke. Up to one fourth of strokes are present on awakening. The link between OSA and wake-up stroke (WUS) has been suggested. We aim to determine the association between OSA and WUS in a Finnish stroke unit cohort.

MATERIAL AND METHODS

An observational prospective longitudinal study consisted of 95 TIA (transient ischemic attack) and mild to moderate stroke patients referred to a Stroke Unit in Finland. Respiratory polygraphy was performed within 72 h of hospital admission. Patients were classified into WUS and non-WUS, and functional outcome measures (mRS, rehabilitation, hospitalization time) were collected. Functional outcomes and prevalence of OSA were compared between non-WUS and WUS.

RESULTS

OSA (AHI > 15/h) was more frequent among WUS than non-WUS (71% and 36%, respectively, p = 0.009). Functional outcome measured with mRS was worse in patients with WUS than non-WUS on registration day and at hospital discharge (p = 0.001). Need for rehabilitation in WUS was 43% of cases compared to 23% of non-WUS (p = 0.067). Hospitalization time was longer (5-15days) in 55% of WUS and 41% of non-WUS patients (p = 0.261).

CONCLUSION

Moderate-to-severe OSA is related to WUS compared to non-WUS. In addition, WUS have worse short-term outcomes measured in mRS. Further studies are needed to determine if OSA is causally linked to WUS.

Implications of Circadian Rhythm in Stroke Occurrence: Certainties and Possibilities

Stroke occurrence is not randomly distributed over time but has circadian rhythmicity with the highest frequency of onset in the morning hours. This specific temporal pattern is valid for all subtypes of cerebral infarction and intracerebral hemorrhage. It also correlates with the circadian variation of some exogenous factors such as orthostatic changes, physical activity, sleep-awake cycle, as well as with endogenous factors including dipping patterns of blood pressure, or morning prothrombotic and hypofibrinolytic states with underlying cyclic changes in the autonomous system and humoral activity. Since the internal clock is responsible for these circadian biological changes, its disruption may increase the risk of stroke occurrence and influence neuronal susceptibility to injury and neurorehabilitation. This review aims to summarize the literature data on the circadian variation of cerebrovascular events according to physiological, cellular, and molecular circadian changes, to survey the available information on the chronotherapy and chronoprophylaxis of stroke and its risk factors, as well as to discuss the less reviewed impact of the circadian rhythm in stroke onset on patient outcome and functional status after stroke.

Circadian Biology and Stroke

Circadian biology modulates almost all aspects of mammalian physiology, disease, and response to therapies. Emerging data suggest that circadian biology may significantly affect the mechanisms of susceptibility, injury, recovery, and the response to therapy in stroke. In this review/perspective, we survey the accumulating literature and attempt to connect molecular, cellular, and physiological pathways in circadian biology to clinical consequences in stroke. Accounting for the complex and multifactorial effects of circadian rhythm may improve translational opportunities for stroke diagnostics and therapeutics.

Non-contrast head CT-based thrombolysis for wake-up/unknown onset stroke is safe: A single-center study and meta-analysis

BACKGROUND

Recent studies have shown that tPA can be safely administered past the standard 4.5 h window with good outcomes when selected with multi-model imaging, which is often lacking outside of comprehensive stroke centers.

AIM

We aim to analyze the safety and outcomes of wake up/unknown onset (WUS/UNK) patients treated based on non-contrast head CT (NCCT) at our institution and in the literature.

METHODS

Suspected stroke patients from January 2015 to December 2018 receiving tPA within 4.5 h (standard window-SW) and with WUS/UNK based on NCCT and clinical-imaging mismatch were identified. We compared baseline characteristics, tPA metrics, and outcome data, with primary outcome as symptomatic intracerebral hemorrhage (sICH). A meta-analysis was performed evaluating NCCT-based treatment of WUS/UNK patients.

RESULTS

Of 1827 patients treated at our hub or through telestroke, 93 underwent WUS/UNK-based treatment. There was no statistical difference in sICH between WUS/UNK and SW: 1% vs. 4% (OR 0.3; 95% confidence interval 0.0-1.9). 90-day modified Rankin scale outcomes were similar between SW and WUS/UNK-treated patients. Seven studies encompassing 485 WUS/UNK patients were included in a pooled analysis with a 2.1% incidence of sICH. In our meta-analysis, three studies compared NCCT-based treated WUS/UNK patients with SW patients with no difference in rate of hemorrhage: 2.1% vs 3.4% (OR 1.01; 95% confidence interval 0.45-2.28).

INTERPRETATION

Our single-center analysis and meta-analysis suggest that tPA can be safely administered based on NCCT with comparable rates of sICH for select WUS/UNK stroke patients.

Is the time of calling helpful for differentiating transient ischaemic attack and stroke from mimics in primary care out-of-hours services? A cross-sectional study

OBJECTIVES

Telephone triage of patients suspected of transient ischaemic attack (TIA) or stroke is challenging. Both TIA and stroke more likely occur during daytime, with a peak in the morning hours. Thus, the time of calling might be a helpful determinant during telephone triage. We assessed the time of calling in patients with stroke-like symptoms who called the out-of-hours services in primary care (OHS-PC), and evaluated whether the time of calling differed between patients with TIA or stroke compared with those with mimics.

DESIGN

Cross-sectional study.

SETTING

Six OHS-PC locations in the Netherlands.

PARTICIPANTS

1269 telephone triage recordings of patients calling the OHS-PC because of stroke-like symptoms. We collected information on patient characteristics, symptoms, time of calling and urgency allocation. The final diagnosis related to each triage call was based on letters from the neurologist (retrieved from the patient's general practitioner).

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measures were the time of calling hourly and 4 hourly, and the risk of TIA or stroke/hour. The secondary outcome measure was the risk ratio of TIA or stroke in the morning (08:00-12:00h) versus other hours.

RESULTS

Mean age was 68.6 (SD±18.5) years, 56.9% were women and 50.0% had a TIA or stroke. The risk ratio of TIA or stroke among people calling with stroke-like symptoms between 08:00-12:00h versus other hours was 1.13 (95% CI 1.00 to 1.28, p=0.070). After correction for age and sex, the adjusted risk ratio was 0.94 (95% CI 0.80 to 1.10, p=0.434).

CONCLUSION

In patients who called the OHS-PC because of stroke-like symptoms, the time of calling did not differ between patients with TIA or stroke and patients with mimics.

TRIAL REGISTRATION NUMBER

The Netherlands National Trial Registry (NTR7331).

Thrombolysis beyond 4.5 h in Acute Ischemic Stroke

PURPOSE OF REVIEW

The purpose of this article is to review the current approaches using neuroimaging techniques to expand eligibility for intravenous thrombolytic therapy in acute ischemic stroke patients with stroke of unknown symptom onset.

RECENT FINDINGS

In recent years, several randomized, placebo-controlled trials have shown neuroimaging-guided approaches to be feasible in determining eligibility for alteplase beyond 4.5 h from last known well, and efficacious for reducing disability. DWI-FLAIR mismatch on MRI is an effective tool to identify stroke lesions less than 4.5 h in onset in patients with stroke of unknown symptom onset. Additionally, an automated perfusion-based approach, assessing for a disproportionate amount of salvageable tissue, is effective in identifying patients likely to benefit from late window alteplase treatment. In patients with stroke of unknown symptom onset, an individualized approach using neuroimaging to determine time of stroke onset or presence of salvageable brain tissue is feasible in the acute setting and associated with improved long-term outcomes.

Circadian Features of Neutrophil Biology

Rhythms in immunity manifest in multiple ways, but perhaps most prominently by the recurrent onset of inflammation at specific times of day. These patterns are of importance to understand human disease and are caused, in many instances, by the action of neutrophils, a myeloid leukocyte with striking circadian features. The neutrophil's short life, marked diurnal variations in number, and changes in phenotype while in the circulation, help explain the temporal features of inflammatory disease but also uncover core features of neutrophil physiology. Here, we summarize well-established concepts and introduce recent discoveries in the biology of these cells as they relate to circadian rhythms. We highlight that although the circadian features of neutrophils are better known and relevant to understand disease, they may also influence important aspects of organ function even in the steady-state. Finally, we discuss the possibility of targeting these temporal features of neutrophils for therapeutic benefit.

Efficacy and Safety of Thrombolytic Therapy for Stroke with Unknown Time of Onset: A Meta-Analysis of Observational Studies

BACKGROUND

Recombinant tissue plasminogen activator (rt-PA) is one of the most effective therapies available for patients with known-onset stroke (KOS). Whether rt-PA treatment would improve functional outcomes in patients with stroke with unknown time of onset (UTOS) is undetermined, we aimed to systematically assess the efficacy and safety of thrombolysis for UTOS patients in this meta-analysis.

METHODS

A systematic literature search of Medline, Embase, and Cochrane Library was conducted. We considered the relevant data comparing thrombolyzed UTOS patients versus nonthrombolyzed UTOS patients or thrombolyzed UTOS patients versus thrombolyzed KOS patients. Treatment efficacy and safety were measured according to modified Rankin Scale scores of 0-2 (mRS 0-2), and the presence of spontaneous intracerebral hemorrhage (SICH) or mortality at 90 days respectively.

RESULTS

A total of 11 studies with 2581 patients meeting the inclusion criteria were included in the meta-analysis. All the patients had an ischemic lesion that was assessed by imaging including computed tomography or magnetic resonance imaging. Among these studies, 6 compared the thrombolytic efficacy in thrombolyzed UTOS patients with that in nonthrombolyzed UTOS patients (mRS 0-2: odds ratio [OR] =1.76, 95% confidence interval [CI] 1.11-2.81, P = .02), and 8 studies compared thrombolyzed UTOS patients with thrombolyzed KOS patients (mRS 0-2: OR = 0.87, 95% CI 0.66-1.15, P = .33). The incidence of SICH and mortality at 90 days had no difference between thrombolyzed UTOS patients versus nonthrombolyzed UTOS patients and thrombolyzed UTOS patients versus thrombolyzed KOS patients (all P > .05).

CONCLUSIONS

Data from observational studies suggest that thrombolysis for UTOS patients had significantly favorable outcomes at 90 days compared with nonthrombolyzed patients.

Wake-up stroke: From pathophysiology to management

Wake-up strokes (WUS) are strokes with unknown exact time of onset as they are noted on awakening by the patients. They represent 20% of all ischemic strokes. The chronobiological pattern of ischemic stroke onset, with higher frequency in the first morning hours, is likely to be associated with circadian fluctuations in blood pressure, heart rate, hemostatic processes, and the occurrence of atrial fibrillation episodes. The modulation of stroke onset time also involves the sleep-wake cycle as there is an increased risk associated with rapid-eye-movement sleep. Furthermore, sleep may have an impact on the expression and perception of stroke symptoms by patients, but also on brain tissue ischemia processes via a neuroprotective effect. Obstructive sleep apnea syndrome is particularly prevalent in WUS patients. Until recently, WUS was considered as a contra-indication to reperfusion therapy because of the unknown onset time and the potential cerebral bleeding risk associated with thrombolytic treatment. A renewed interest in WUS has been observed over the past few years related to an improved radiological evaluation of WUS patients and the recent demonstration of the clinical efficacy of reperfusion in selected patients when the presence of salvageable brain tissue on advanced cerebral imaging is demonstrated.

Circadian rhythms may not influence the outcomes of thrombolysis in patients with ischemic stroke: A study from China

Circadian rhythms can affect physical or mental activities as well as the time of stroke onset. The impact of circadian rhythms on acute ischemic stroke (AIS) patients treated by recombinant alteplase (rt-PA) is still incongruent. This study aims to consider whether the outcomes of thrombolysis differ depending on stroke onset time and rt-PA infusion time in patients with AIS. A total of 447 AIS patients, who underwent rt-PA intravenous infusion within 4.5 hours after stroke onset, were enrolled in this study consecutively from June 2010 through December 2016. All of the patients were grouped based on the stroke onset time and rt-PA infusion time into two exact 12-hour intervals as daytime (06:01-18:00) and nighttime (18:01-06:00) and further divided into four subgroups at 6-hour time intervals (00:01-06:00, 06:01-12:00, 12:01-18:00 and 18:01-24:00). Major neurological improvement at 1 hour, 24 hours and 7 days, 7-day mortality rate and 24-hour hemorrhage transformation was recorded. The results showed that a total of 295 patients (66.4%) appeared with AIS and 252 (56.4%) were treated during daytime. Higher NIHSS at admission was observed when stroke occurred in nighttime, especially during 00:01-06:00. Patients with stroke onset in nighttime especially during 18:01-24:00 had a significant shorter onset-door time and onset-needle time. No differences of the major neurological improvement at 1 hour, 24 hours and 7 days, 24-hour hemorrhagic transformation and 7-day fatality rate were found among either 12-hour time frames or 6-hour time frames according to the time of stroke onset or rt-PA infusion. In conclusion, there was no evidence to predict that circadian rhythms could influence the outcomes of AIS patients treated with rt-PA in China, although stroke onset during nighttime might aggravate neurological impairment before treatment. Further, multicenter and prospective clinical trials with larger number of subjects are still needed to draw more reliable conclusions.

Neuroimaging Paradigms to Identify Patients for Reperfusion Therapy in Stroke of Unknown Onset

Despite the proven efficacy of intravenous alteplase or endovascular thrombectomy for the treatment of patients with acute ischemic stroke, only a minority receive these treatments. This low treatment rate is due in large part to delay in hospital arrival or uncertainty as to the exact time of onset of ischemic stroke, which renders patients outside the current guideline-recommended window of eligibility for receiving these therapeutics. However, recent pivotal clinical trials of late-window thrombectomy now force us to rethink the value of a simplistic chronological formulation that “time is brain.” We must recognize a more nuanced concept that the rate of tissue death as a function of time is not invariant, that still salvageable tissue at risk of infarction may be present up to 24 h after last-known well, and that those patients may strongly benefit from reperfusion. Multiple studies have sought to address this clinical dilemma using neuroimaging methods to identify a radiographic time-stamp of stroke onset or evidence of salvageable ischemic tissue and thereby increase the number of patients eligible for reperfusion therapies. In this review, we provide a critical analysis of the current state of neuroimaging techniques to select patients with unwitnessed stroke for revascularization therapies and speculate on the future direction of this clinically relevant area of stroke research.

Regulation of Cerebral Blood Flow: Response to Cytochrome P450 Lipid Metabolites

There have been numerous reviews related to the cerebral circulation. Most of these reviews are similar in many ways. In the present review, we thought it important to provide an overview of function with specific attention to details of cerebral arterial control related to brain homeostasis, maintenance of neuronal energy demands, and a unique perspective related to the role of astrocytes. A coming review in this series will discuss cerebral vascular development and unique properties of the neonatal circulation and developing brain, thus, many aspects of development are missing here. Similarly, a review of the response of the brain and cerebral circulation to heat stress has recently appeared in this series (8). By trying to make this review unique, some obvious topics were not discussed in lieu of others, which are from recent and provocative research such as endothelium-derived hyperpolarizing factor, circadian regulation of proteins effecting cerebral blood flow, and unique properties of the neurovascular unit. © 2018 American Physiological Society. Compr Physiol 8:801-821, 2018.

Increased Risk of Ischemic Stroke during Sleep in Apneic Patients

Background and Purpose

The literature indicates that obstructive sleep apnea (OSA) increases the risk of ischemic stroke. However, the causal relationship between OSA and ischemic stroke is not well established. This study examined whether preexisting OSA symptoms affect the onset of acute ischemic stroke.

Methods

We investigated consecutive patients who were admitted with acute ischemic stroke, using a standardized protocol including the Berlin Questionnaire on symptoms of OSA prior to stroke. The collected stroke data included the time of the stroke onset, risk factors, and etiologic subtypes. The association between preceding OSA symptoms and wake-up stroke (WUS) was assessed using multivariate logistic regression analysis.

Results

We identified 260 subjects with acute ischemic strokes with a definite onset time, of which 25.8% were WUS. The presence of preexisting witnessed or self-recognized sleep apnea was the only risk factor for WUS (adjusted odds ratio=2.055, 95% confidence interval=1.035–4.083, p=0.040).

Conclusions

Preexisting symptoms suggestive of OSA were associated with the occurrence of WUS. This suggests that OSA contributes to ischemic stroke not only as a predisposing risk factor but also as a triggering factor. Treating OSA might therefore be beneficial in preventing stroke, particularly that occurring during sleep.

Daily Variation in the Occurrence of Different Subtypes of Stroke

Three thousand two hundred and ninety-eight patients admitted to our Stroke Unit with hemorrhagic, large artery atherosclerosis, cardioembolic, small-vessel occlusion, and undetermined etiology-cryptogenic strokes were included in the study. The circadian variability in onset in each stroke subgroup and the associations with various risk factors were analyzed. In each subgroup, a significant minority of patients suffered from stroke during sleep. In the ischemic group, hypercholesterolemia, paroxysmal atrial fibrillation, and previous myocardial infarction facilitated the onset during waking. During waking, stroke onset was significantly higher in the morning compared to the afternoon both in the hemorrhagic and in the ischemic type. In hemorrhagic stroke, a previous stroke was associated with a lower early morning occurrence. In large artery atherosclerosis stroke, males were at higher risk of early morning occurrence (p < 0.01). In small-vessel occlusion stroke, hypertension is significantly more present in the morning compared to the afternoon onset (p < 0.005). Circadian patterns of stroke onset were observed both in hemorrhagic and in ischemic stroke, irrespective of the ischemic subgroup. In all groups, stroke was more likely to occur during waking than during sleep and, in the diurnal period, during morning than during afternoon. Moreover, sex and some clinical factors influence the diurnal pattern.

Wake-Up Stroke: Current Understanding

Patients with wake-up strokes account for approximately 1 in 5 individuals presenting with an acute ischemic stroke. However, they are commonly excluded from acute stroke treatment. This article reviews the current understanding of wake-up strokes. A comparison of wake-up and awake-onset strokes demonstrated that they are physiologically, clinically, and radiologically similar. Use of advanced CT and MRI techniques may help extend acute stroke treatment options to patients with wake-up stroke.

A Stroke Registry Data on the Use of Intravenous Recombinant Tissue Plasminogen Activator in Stroke of Unknown Time of Onset

BACKGROUND

Stroke of unknown time of onset (SUTO) constitutes one fifth of all ischemic stroke admissions, and routine use of intravenous recombinant tissue plasminogen activator (IV rtPA) is recommended only in patients with a symptom onset time of less than 4.5 hours. There are limited data on clinical outcome in patients with SUTO versus patients with symptoms onset less than 4.5 hours from onset time. We hypothesized that efficacy and safety outcomes of IV rtPA therapy in selected SUTO patients are comparable to those with known onset time.

METHODS

We compared 90 days' modified Rankin Scale (mRS), rates of symptomatic intracerebral hemorrhage (sICH), in-hospital mortality, and death due to sICH between 3 groups treated with IV rtPA: SUTO, 3 hours or less, and 3.0-4.5 hours from prospective patient admissions between April 1, 2012, and July 31, 2013.

RESULTS

There were 65 participants in the SUTO group, 186 in the 3 hours or less group, and 51 in the 3.0-4.5 hours group. In-hospital mortality rates were 14.5%, 13.5%, and 11.8%, respectively. sICH risks were 1.5%, 1.6%, and 5.8%, and death rates due to sICH were 0%, 1.1%, and 1.9%, respectively. Ninety days' odds of excellent clinical outcome (mRS score 0-1) were not different between the SUTO group (odds ratio [OR] 1.14, 95% confidence interval [CI]: .63-2.10), the 3 hours or less group (OR .87, 95% CI: .48-1.60), and the 3.0-4.5 hours group (OR .79, 95% CI: .48-1.60) (P = .82).

CONCLUSION

Thrombolytic therapy outcome in SUTO is not different from in-license use in our patient population. There is an urgent need to include this patient group in ongoing randomized multicenter trials.

What to do With Wake-Up Stroke

Wake-up stroke, defined as the situation where a patient awakens with stroke symptoms that were not present prior to falling asleep, represents roughly 1 in 5 acute ischemic strokes and remains a therapeutic dilemma. Patients with wake-up stroke were excluded from most ischemic stroke treatment trials and are often not eligible for acute reperfusion therapy in clinical practice, leading to poor outcomes. Studies of neuroimaging with standard noncontrast computed tomography (CT), magnetic resonance imaging (MRI), and multimodal perfusion-based CT and MRI suggest wake-up stroke may occur shortly before awakening and may assist in selecting patients for acute reperfusion therapies. Pilot studies of wake-up stroke treatment based on these neuroimaging features are promising but have limited generalizability. Ongoing randomized treatment trials using neuroimaging-based patient selection may identify a subset of patients with wake-up stroke that can safely benefit from acute reperfusion therapies.

Circadian variation in the effect of intravenous thrombolysis after non-lacunar stroke

The onset of non-lacunar stroke symptoms has a circadian variation, with a higher risk in the early morning hours and lower risk during the nighttime period, but this circadian distribution has not been clearly established on the effect of intravenous (IV) thrombolysis. The aim of the present study was to assess whether the time interval based on time of Alteplase IV infusion may influence the effect of treatment in patients with non-lacunar stroke. We conducted an analysis on prospectively collected data of 476 non-lacunar stroke patients treated with IV thrombolysis. To identify a possible circadian variation in the effect of Alteplase IV infusion, we used the following outcome measures: major neurological improvement (NIH stroke scale [NIHSS] score decrease of ≤8 points from baseline or NIHSS score of 0 at 24 h), and hemorrhagic transformation according to European Cooperative Acute Stroke Study trial definition within 24 h. Multivariate analysis showed that ORs for major neurological improvement were lower in patients who started IV thrombolysis in the 6 AM-noon interval (OR 0.35, 95% CI 0.16-0.74, p = 0.006) and noon-6 PM interval (OR 0.40, 95% CI 0.20-0.81, p = 0.010), whereas ORs for hemorrhagic transformation were lower in patients who started IV thrombolysis in the noon-6 PM interval (OR 0.29, 95% CI 0.12-0.67, p = 0.004) and in the 6 PM-midnight interval (OR 0.26, 95% CI 0.11-0.62, p = 0.002), compared with midnight-6 AM interval. The effect of Alteplase IV infusion could show a circadian variation in patients with non-lacunar stroke. After comparison with the midnight-6 AM interval, thrombolysis could be more safe from noon to midnight, and less effective from 6 AM to 6 PM.

Endovascular therapy of wake-up strokes in the modern era of stent retriever thrombectomy

Background

Endovascular treatment of wake-up strokes (WUS) has been previously described, mostly with the use of pharmacological thrombolysis or first generation thrombectomy devices.

Objective

To describe outcomes of WUS treated with modern endovascular therapy since the Food and Drug Administration approval of stent retrievers, and to identify predictors of good clinical outcome in this population of stroke patients.

Methods

We performed a multicenter retrospective analysis of consecutive patients with WUS who underwent thrombectomy with stent retrievers Trevo (Stryker, Kalamazoo, Michigan, USA) and Solitaire FR (Covidien, Irvine, California, USA), or primary aspiration thrombectomy. We correlated favorable clinical outcomes with demographic, clinical, and technical characteristics.

Results

52 patients were included in this study; 46 (88%) cases were treated with stent retrievers and 6 (12%) were treated with primary aspiration thrombectomy alone. Successful recanalization (Thrombolysis in Cerebral Infarction (TICI) 2b/3) was achieved in 36 (69%) patients. Favorable clinical outcome at 3 months, defined as a modified Rankin Scale score of 0–2, was achieved in 25 (48%) patients. Duration of intervention <30 min and its success, defined as TICI 2b/3 recanalization, were strong predictors of favorable clinical outcome at 90 days (p<0.001 and p<0.0001, respectively).

Conclusions

Our study indicates that endovascular treatment of WUS with stent retrievers and aspiration thrombectomy is safe and effective.

Wake-up Strokes Are Similar to Known-Onset Morning Strokes in Severity and Outcome

BACKGROUND

Stroke symptoms noticed upon waking, wake-up stroke, account for up to a quarter of all acute ischemic strokes. Patients with wake-up stroke, however, are often excluded from thrombolytic therapy.

METHODS

Using our prospectively collected stroke registry, wake-up stroke and known-onset morning strokes were identified. Wakeup stroke was defined as a patient who was asleep >3 hours and first noted stroke symptoms upon awakening between 0100 and 1100. Known-onset morning stroke was defined as a patient who had symptom onset while awake during the same time interval. We compared wake-up stoke to known-onset morning stroke with respect to patient demographics, stroke severity, etiology and outcomes.

RESULTS

One-quarter of patients with acute ischemic strokes (391/1415) had documented time between 0100 and 1100 of symptom onset: 141 (36%) wake-up strokes and 250 (64%) known-onset morning strokes. No difference in baseline characteristics, stroke severity, stroke etiology, neurologic deterioration, discharge disposition or functional outcome was detected. Known-onset morning stroke patients were significantly more likely to get thrombolytic therapy and have higher risk of in-hospital mortality. Wake-up stroke patients tended to be older, have higher diastolic blood pressure and have longer length of hospital stay.

DISCUSSION

While patients with wake-up stroke were similar to patients with known-onset morning stroke in many respects, patients with known onset morning stroke were significantly more likely to get treated with thrombolytic therapy and have higher in-hospital mortality.

Outcome after Stroke upon Awakening

Background:

An estimated 20-25% of all strokes occur during sleep and these patients wake up with their deficits. This study evaluated outcomes among patients who woke up with stroke compared to those who were awake at stroke onset.

Methods:

Using data from the Registry of the Canadian Stroke Network Phases 1 and 2, we compared demographics, clinical data and six-month outcomes between patients with stroke-on-awakening versus stroke-while-awake. Strokes of all types (ischemic stroke, transient ischemic attack, intracerebral hemorrhage and subarachnoid hemorrhage) were included. Standard descriptive statistics, multivariable logistic regression and general linear modeling were applied to the data to compare variables.

Results:

Among 2,585 stroke patients, 349 (13.5%) woke up with stroke and 2,236 (86.5%) did not. Patients with stroke-on-awakening were more likely to have higher blood pressure and to suffer ischemic stroke, but stroke severity, measured by level of consciousness, did not differ. Mortality both at discharge and at six-month follow-up did not differ between the two cohorts. However, patients with stroke-on-awakening were less likely to return home, and their median Stroke Impact Scale-16 scores were 7.0 points lower compared to those with stroke-while-awake.

Conclusions:

There are minor demographic and clinical differences between patients with stroke-on-awakening and stroke-while-awake. Functional outcomes are slightly worse among patients with stroke-on-awakening, an effect which was driven by poor outcomes among patients with subarachnoid hemorrhage.

Seasonal differences and circadian variation in stroke occurrence and stroke subtypes

BACKGROUND

India is a subtropical country with clear seasonal variations in weather conditions. Seasonal and circadian variation in occurrence of subtypes of cerebrovascular disease has been of interest in several studies from different countries and climate zones, but discrepant results have made the conclusions unclear. The aim of the present study was to observe the seasonal and circadian variation in the occurrence of stroke and its subtypes among our population.

METHODS

This was a cross-sectional observational study based on new cases and past cases of stroke on follow-up, conducted between January 2011 and December 2012 in the Department of Neurology, at the All India Institute of Medical Sciences, New Delhi, India. The date and time of onset of the stroke was recorded. The categorization of months into season was in accordance with the Indian Meteorological Department guidelines. The time of onset was distributed into 6 hourly intervals. Statistical calculations were performed using Stata version 12.1 and SPSS version 20.

RESULTS

A total of 583 patients were included for the study. The rate of occurrence of stroke was highest in the late morning 0600-1159 hours (P value <.001) compared with other times of the day, regardless of gender or age for both ischemic and hemorrhagic strokes. It was lowest in late evening (1800-2359 hours) quadrant compared with other quadrants. Although there was no significant difference found by dichotomizing the groups into two 6-month periods, there was an increasing trend in number of patients with stroke during the months November-February. There was no difference in stroke occurrence between the types of stroke or within each type among different seasons with different temperatures. Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification of ischemic strokes also did not show any association with season or circadian rhythm.

CONCLUSIONS

There is a significant increase in occurrence of strokes between 0600 and 1159 hours and lowest between 1800-2359 hours. No significant variation in stroke occurrence or subtype for any of the seasons was observed.

Review of plants and their constituents in the therapy of cerebral ischemia

Cerebral ischemia is a condition in which there is insufficient blood flow to the brain to meet metabolic demand. This leads to cerebral hypoxia and thus to the death of neuronal cells or stroke. The limited number of medicines currently available for patients following ischemic stroke and insufficient data on efficiency of these chemicals in the treatment of stroke led us to the search for novel therapeutic approaches. Recent studies have focused on the possible capacity of natural compounds extracted from vegetables and fruits, to prevent human disabilities caused by cerebral ischemia. In this review, we will discuss some plants and their constituents that may protect brain ischemia or delay the neurological disorders following a stroke. We have reviewed different studies in scientific databases that investigate herbal compounds and their effects on cerebral ischemia.

Advanced neuroimaging to guide acute stroke therapy

Traditionally non-contrast CT has been considered the first choice imaging modality for acute stroke. Acute ischemic stroke patients presenting to the hospital within 3-hours from symptom onset and without any visible hemorrhages or large lesions on CT images are considered optimum reperfusion therapy candidates. However, non-contrast CT alone has been unable to identify best reperfusion therapy candidates outside this window. New advanced imaging techniques are now being used successfully for this purpose. Non-invasive CT or MR angiography images can be obtained during initial imaging evaluation for identification and characterization of vascular lesions, including occlusions, aneurysms, and malformations. Either CT-based perfusion imaging or MRI-based diffusion and perfusion imaging performed immediately upon arrival of a patient to the hospital helps estimate the extent of fixed core and penumbra in ischemic lesions. Patients having occlusive lesions with small fixed cores and large penumbra are preferred reperfusion therapy candidates.

Presentation and outcomes of "wake-up strokes" in a large randomized stroke trial: analysis of data from the International Stroke Trial

BACKGROUND

Recent studies comparing the outcomes of wake-up stroke (WUS) and stroke while awake (SWA) patients reveal better outcomes among SWA patients, attributable in part to their higher rates of thrombolysis. Patients with WUS are largely excluded from therapy. Earlier analyses, conducted before the approval of alteplase for acute stroke, show the true divergence of natural histories between these 2 groups.

METHODS

We analyzed 17,398 patients with ischemic stroke from the International Stroke Trial and compared both presentations and outcomes between the WUS and SWA groups. Severity was assessed by level of consciousness, Oxfordshire Community Stroke Project (OCSP) stroke classification, number of neurologic deficits, and predicted probability of dependency or death. Outcomes were assessed at day 14 and at 6 months. Outcome assessments were controlled for potential confounders.

RESULTS

WUS represented 29.6% of all ischemic strokes. More severe OSCP stroke type (total anterior circulation syndrome) was less common in WUS. Although more patients with WUS were alert at presentation with a lower predicted probability of dependency, the 14-day mortality rates and rates of poor outcome at 6 months were similar between the 2 groups.

CONCLUSIONS

WUS patients comprise one quarter to one third of ischemic stroke patients. Despite their more benign presentations, they deteriorate to outcome rates similar to SWA. Although they are typically excluded from time-dependent acute interventions, patients with WUS may benefit from acute intervention to prevent this worsening natural history.

Wake-up or unclear-onset strokes: are they waking up to the world of thrombolysis therapy?

Wake-up or unclear-onset strokes occur in up to one-fourth of patients with ischemic stroke. Although stroke severity and clinical outcomes appear to be poorer in wake-up strokes than nonwake-up strokes, many patients with wake-up strokes do not receive thrombolytic therapy because stroke onset time cannot be determined. Recent studies have suggested, however, that the actual onset time of wake-up stroke is close to the wake-up time. Furthermore, advanced imaging technologies may enable us to identify patients with favorable risk-benefit profiles for thrombolysis. Indeed, empirical thrombolytic treatments have suggested safety and feasibility of such therapy in these patients. Based on these promising results and the development of multimodal imaging methods, prospective thrombolysis trials using predefined imaging criteria are currently under way to test the safety and efficacy of thrombolysis in patients with wake-up or unclear-onset strokes. The establishment of optimal acute treatment strategies in this important yet so far neglected group of patients is eagerly awaited.

Diffusion-weighted imaging-fluid attenuated inversion recovery mismatch in nocturnal stroke patients with unknown time of onset

BACKGROUND

More than a quarter of patients with ischemic stroke (IS) are excluded from thrombolysis because of an unknown time of symptom onset. Recent evidence suggests that a mismatch between diffusion-weighted imaging (DWI) and fluid attenuated inversion recovery (FLAIR) imaging could be used as a surrogate for the time of stroke onset. We compared used the DWI-FLAIR mismatch and the FLAIR/DWI ratio to estimate the time of onset in a group of patients with nocturnal strokes and unknown time of onset.

METHODS

We used a prospectively collected acute IS patient database with MRI as the initial imaging modality. Nineteen selected nocturnal stroke patients with unknown time of onset were compared with 22 patients who had an MRI scan within 6 hours from stroke onset (control A) and 19 patients who had an MRI scan between 6 and 12 hours (control B). DWI and FLAIR signal was rated as normal or abnormal. FLAIR/DWI ratio was calculated from independent DWI and FLAIR ischemic lesion volumes using semiautomatic software.

RESULTS

The DWI-FLAIR mismatch was different among groups (unknown 43.7%; control A 63.6%; control B 10.5%; Fisher-Freeman-Halton test; P = .001). There were significant differences in FLAIR/DWI ratio among the 3 groups (unknown 0.05 ± 0.12; control A 0.17 ± 0.15; control B 0.04 ± 0.06; Kruskal-Wallis test; P < .0001). Post-hoc pairwise comparisons revealed that FLAIR/DWI ratio from the unknown group was significantly different from the control B group (P = .0045) but not different from the control A group. DWI volumes were not different among the 3 groups.

CONCLUSIONS

A large proportion of patients with nocturnal IS and an unknown time of stroke initiation have a DWI-FLAIR mismatch, suggesting a recent onset of stroke.

Wake-up stroke within 3 hours of symptom awareness: imaging and clinical features compared to standard recombinant tissue plasminogen activator treated stroke

BACKGROUND

Patients with wake-up stroke (WUS) are excluded from thrombolysis because of unknown time of symptom onset. Previous studies have reported similar stroke severity and early ischemic changes (EICs) in patients with WUS and stroke of known onset. These studies, however, included patients within a large timeframe to imaging or did not quantify EICs. The aim of our study was to quantify EICs of patients with WUS presenting within 3 hours of symptom recognition compared to standard 3-hours recombinant tissue plasminogen activator (rt-PA)-treated patients and assess the extent of ischemic lesion and functional independence at follow-up.

METHODS

Patients were selected from our prospectively collected stroke database. Baseline and follow-up computed tomographic scans were graded with Alberta Stroke Program Early Computed Tomography Score (ASPECTS). Clinical outcome measures were modified Rankin Scale score, mortality, and symptomatic intracerebral hemorrhage.

RESULTS

Demographic features, risk factors, stroke severity, and baseline ASPECTS were similar in both groups. WUS and rt-PA-treated patients had similar tissue outcome (median ASPECTS 7.0 vs 7.5; P = .202). Functional outcome was more favorable in rt-PA-treated patients (61.6% vs 43.1%; odds ratio [OR] 2.12; 95% confidence interval [CI] 1.05-4.28; P = .037). After adjusting for age, stroke severity, treatment, and EICs in less than one-third of middle cerebral artery territory, rt-PA and National Institutes of Health Stroke Scale scores remained the only significant predictors of outcome (OR 7.76; 95% CI 2.40-25.05; P = .001 and OR 0.74; 95% CI 0.67-0.82; P < .001, respectively).

CONCLUSIONS

Within 3 hours of symptom recognition, patients with WUS have EICs similar to rt-PA-treated patients. It is reasonable to expect that selected WUS patients might benefit from thrombolysis within 3 hours of symptom awareness.

Lesion size and behavioral deficits after endothelin-1-induced ischemia are not dependent on time of day

BACKGROUND

The occurrence of stroke exhibits a strong circadian pattern with a peak in the morning hours after waking. The factors that influence this pattern of stroke prevalence may confer varying degrees of neuroprotection and therefore influence stroke severity. This question is difficult to address in clinical cases because of the variability in the location and duration of the ischemic event.

METHODS

The purpose of this study was to determine if time of day affected the severity of stroke targeting the motor cortex in rats. Strokes were produced using topical application of the vasoconstrictor endothelin-1 to motor cortex of unanesthetized animals at 2 time points: early day and early night. Behavioral deficits were measured using reaching, cylinder, and horizontal ladder tasks, and the volume of the lesion was quantified.

RESULTS

Behavior on reaching and horizontal ladder tasks were both severely impaired by endothelin-1 treatment compared to vehicle-treated animals, but deficits did not differ according to time of treatment. Similarly, while endothelin-1 produced larger lesions of the motor cortex than did vehicle treatment, the size of the lesion did not differ according to time of treatment.

CONCLUSIONS

These results suggest that while many factors under circadian control can influence the prevalence of stroke, the magnitude of lesion and behavioral deficit resulting from an ischemic event may not be influenced by time of day.

Population-based study of wake-up strokes

OBJECTIVE

Previous studies have estimated that wake-up strokes comprise 8%to 28% of all ischemic strokes, but these studies were either small or not population-based. We sought to establish the proportion and event rate of wake-up strokes in a large population-based study and to compare patients who awoke with stroke symptoms with those who were awake at time of onset.

METHODS

First-time and recurrent ischemic strokes among residents of the Greater Cincinnati/Northern Kentucky region (population 1.3 million) in 2005 were identified using International Classification of Diseases-9 codes 430-436 and verified via study physician review. Ischemic strokes in patients aged 18 years and older presenting to an emergency department were included. Baseline characteristics were ascertained, along with discharge modified Rankin Scale scores and 90-day mortality.

RESULTS

We identified 1,854 ischemic strokes presenting to an emergency department, of which 273 (14.3%) were wake-up strokes. There were no differences between wake-up strokes and all other strokes with regard to clinical features or outcomes except for minor differences in age and baseline retrospective NIH Stroke Scale score. The adjusted wake-up stroke event rate was 26.0/100,000. Of the wake-up strokes, at least 98 (35.9%) would have been eligible for thrombolysis if arrival time were not a factor.

CONCLUSIONS

Within our population, approximately 14% of ischemic strokes presenting to an emergency department were wake-up strokes. Wake-up strokes cannot be distinguished from other strokes by clinical features or outcome. We estimate that approximately 58,000 patients with wake-up strokes presented to an emergency department in the United States in 2005.

Imaging stroke patients with unclear onset times

Stroke is a leading cause of death and adult morbidity worldwide. By defining stroke symptom onset by the time the patient was last known to be well, many patients whose onsets are unwitnessed are automatically ineligible for thrombolytic therapy. Advanced brain imaging may serve as a substitute witness to estimate stroke onset and duration in those patients who do not have a human witness. This article reviews and compares some of these imaging-based approaches to thrombolysis eligibility, which can potentially expand the use of thrombolytic therapy to a broader population of acute stroke patients.

Alberta Stroke Program Early CT Score (ASPECTS) in patients with wake-up stroke

One-quarter of ischemic strokes occur during sleep, and affected patients are excluded from thrombolytic therapy because of an unknown time of stroke onset. It has been suggested that early ischemic changes detected on computed tomography (CT) are similar in patients with acute stroke and patients who recently awoke with stroke. We compared head CT scans using the Alberta Stroke Program Early CT Score (ASPECTS) in patients who were likely to suffer their stroke during sleep (awoke group) and a control group of patients with stroke of known onset time. Patients were recruited from a prospectively collected acute stroke database. The awoke group was defined as all ischemic stroke patients who were "last seen normal" more than 4 hours ago, arrived between 4 a.m. and 10 a.m., and underwent head CT within 15 hours of the time last seen normal. The control group was randomly selected from patients who underwent head CT within 4 hours of stroke onset. The ASPECTS evaluations were performed by investigators blinded to patient group and time of onset. A modified Rankin Scale (mRS) score was available in 15 awoke patients and 46 control patients at 90 days after stroke. Twenty-eight awoke patients and 68 control patients had suitable imaging for the ASPECTS. Baseline demographic characteristics and risk factors were similar in the 2 groups. The dichotomized ASPECTS analysis (≤7 vs 8-10) showed no significant differences between the groups. ASPECTS was 8-10 in 89.3% the awoke group and 95.6% in the control group (P=.353). There was a trend toward higher 90-day mRS score (0-1) in the awoke group versus controls (73% vs 45%; P=.079). Initial ASPECTS was similar in patients with wake-up stroke and those with 4 hours of symptoms. This suggests that a subset of wake-up stroke patients might be suitable for thrombolytic therapy.