Why now? Moving from stroke risk factors to stroke triggers

Autonomic Nervous System and Stress to Predict Secondary Ischemic Events after Transient Ischemic Attack or Minor Stroke: Possible Implications of Heart Rate Variability

Transient ischemic attack (TIA) and minor stroke have high risks of recurrence and deterioration into severe ischemic strokes. Risk stratification of TIA and minor stroke is essential for early effective treatment. Traditional tools have only moderate predictive value, likely due to their inclusion of the limited number of stroke risk factors. Our review follows Hans Selye’s fundamental work on stress theory and the progressive shift of the autonomic nervous system (ANS) from adaptation to disease when stress becomes chronic. We will first show that traditional risk factors and acute triggers of ischemic stroke are chronic and acute stress factors or “stressors,” respectively. Our first review shows solid evidence of the relationship between chronic stress and stroke occurrence. The stress response is tightly regulated by the ANS whose function can be assessed with heart rate variability (HRV). Our second review demonstrates that stress-related risk factors of ischemic stroke are correlated with ANS dysfunction and impaired HRV. Our conclusions support the idea that HRV parameters may represent the combined effects of all body stressors that are risk factors for ischemic stroke and, thus, may be of important predictive value for the risk of subsequent ischemic events after TIA or minor stroke.

Risk Factors for Pregnancy-Associated Stroke in Women With Preeclampsia

BACKGROUND AND PURPOSE

Preeclampsia affects 3% to 8% of pregnancies and increases risk of pregnancy-associated stroke (PAS). Data are limited on which women with preeclampsia are at highest risk for PAS.

METHODS

Using billing data from the 2003 to 2012 New York State Department of Health inpatient database, we matched women with preeclampsia and PAS 1:3 to preeclamptic controls based on age and race/ethnicity. Pre-defined PAS risk factors included pregnancy complications, infection present on admission, vascular risk factors, prothrombotic states, and coagulopathies. We constructed multivariable conditional logistic regression models to calculate the odds ratios (ORs) and 95% confidence intervals (95% CIs) for independent risk factors for PAS.

RESULTS

Among women aged 12 to 55 years admitted to New York State hospitals for any reason during the study period (n=3 373 114), 88 857 had preeclampsia, and 197 of whom (0.2%) had PAS. In multivariable analysis, women with preeclampsia and stroke were more likely than controls to have severe preeclampsia or eclampsia (OR, 7.2; 95% confidence interval [CI], 4.6-11.3), infections present on admission (OR, 3.0; 95% CI, 1.6-5.8), prothrombotic states (OR, 3.5; 95% CI, 1.3-9.2), coagulopathies (OR, 3.1; 95% CI, 1.3-7.1), or chronic hypertension (OR, 3.2; 95% CI, 1.8-5.5). Additional analyses matched and stratified by severity of preeclampsia confirmed these results.

CONCLUSIONS

Infections, chronic hypertension, coagulopathies, and underlying prothrombotic conditions increase PAS risk in women with preeclampsia. These women may warrant closer monitoring.

Psychiatric Hospitalization Increases Short-Term Risk of Stroke

BACKGROUND AND PURPOSE

Recent evidence suggests that psychological distress, including the symptoms of psychiatric illness, may acutely increase the risk of stroke. However, existing studies are limited by small sample sizes, inherent recall bias, and poorly defined criteria for what constitutes psychological distress.

METHODS

We analyzed administrative data from the Healthcare Cost and Utilization Project for the state of California from 2007 to 2009 using a case-crossover design. Conditional logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (95% CIs) for combined hemorrhagic and ischemic stroke risk occurring within 15, 30, 90, 180, and 365 days of a hospitalization for a psychiatric diagnosis (as defined by International Classification of Diseases, Ninth Revision, code) among adults.

RESULTS

Psychiatric hospitalizations within 1 year before stroke were found in 2585 (5.3%) of 48 558 stroke patients. Hospitalization for a psychiatric condition was associated with increased risk of stroke within all 5 time periods, with the highest odds of stroke occurring within 15 days (0-15 days: OR, 3.5; 95% confidence interval [CI], 2.6-4.8; 0-30 days: OR, 3.0; 95% CI, 2.4-3.8; 0-90 days: OR, 2.3; 95% CI, 2.0-2.7; 0-180 days: OR, 2.2; 95% CI, 2.0-2.5; and 0-365 days: OR, 2.6; 95% CI, 2.4-2.8).

CONCLUSIONS

Psychiatric hospitalization increases the short-term risk of stroke, particularly within the 15-day period after hospitalization.

Risk of Acute Stroke After Hospitalization for Sepsis: A Case-Crossover Study

BACKGROUND AND PURPOSE

Infections have been found to increase the risk of stroke over the short term. We hypothesized that stroke risk would be highest shortly after a sepsis hospitalization, but that the risk would decrease, yet remain up to 1 year after sepsis.

METHODS

This case-crossover analysis utilized data obtained from the California State Inpatient Database of the Healthcare Cost and Utilization Project. All stroke admissions were included. Exposure was defined as hospitalization for sepsis or septicemia 180, 90, 30, or 15 days before stroke (risk period) or similar time intervals exactly 1 or 2 years before stroke (control period). Conditional logistic regression was used to calculate the odds ratio (OR) and 95% confidence interval (95% CI) for the association between sepsis/septicemia and ischemic or hemorrhagic stroke.

RESULTS

Ischemic (n=37 377) and hemorrhagic (n=12 817) strokes that occurred in 2009 were extracted where 3188 (8.5%) ischemic and 1101 (8.6%) hemorrhagic stroke patients had sepsis. Sepsis within 15 days before the stroke placed patients at the highest risk of ischemic (OR, 28.36; 95% CI, 20.02-40.10) and hemorrhagic stroke (OR, 12.10; 95% CI, 7.54-19.42); however, although the risk decreased, it remained elevated 181 to 365 days after sepsis for ischemic (OR, 2.59; 95% CI, 2.20-3.06) and hemorrhagic (OR, 3.92; 95% CI 3.29-4.69) strokes. There was an interaction with age (P=0.0006); risk of developing an ischemic stroke within 180 days of hospitalization for sepsis increased 18% with each 10-year decrease in age.

CONCLUSIONS

Risk of stroke is high after sepsis, and this risk persists for up to a year. Younger sepsis patients have a particularly increased risk of stroke after sepsis.

Stroke Risk Factors, Genetics, and Prevention

Stroke is a heterogeneous syndrome, and determining risk factors and treatment depends on the specific pathogenesis of stroke. Risk factors for stroke can be categorized as modifiable and nonmodifiable. Age, sex, and race/ethnicity are nonmodifiable risk factors for both ischemic and hemorrhagic stroke, while hypertension, smoking, diet, and physical inactivity are among some of the more commonly reported modifiable risk factors. More recently described risk factors and triggers of stroke include inflammatory disorders, infection, pollution, and cardiac atrial disorders independent of atrial fibrillation. Single-gene disorders may cause rare, hereditary disorders for which stroke is a primary manifestation. Recent research also suggests that common and rare genetic polymorphisms can influence risk of more common causes of stroke, due to both other risk factors and specific stroke mechanisms, such as atrial fibrillation. Genetic factors, particularly those with environmental interactions, may be more modifiable than previously recognized. Stroke prevention has generally focused on modifiable risk factors. Lifestyle and behavioral modification, such as dietary changes or smoking cessation, not only reduces stroke risk, but also reduces the risk of other cardiovascular diseases. Other prevention strategies include identifying and treating medical conditions, such as hypertension and diabetes, that increase stroke risk. Recent research into risk factors and genetics of stroke has not only identified those at risk for stroke but also identified ways to target at-risk populations for stroke prevention.

Infection and Stroke: an Update on Recent Progress

The role of infection in cerebrovascular disease is complex and remains incompletely understood. Over the last 5 years, investigators have made notable inroads in untangling this thorny topic. In this review, we examine these recent developments, concentrating on four aspects of the relationship between infection and stroke. We first discuss specific infectious agents as direct causes of stroke, focusing on recent work implicating herpesviruses and HIV in cerebral vasculopathy. We then discuss systemic infection of any type as a stroke trigger, focusing on the relationship of infection to timing of acute stroke, both in children and adults, as well as the role of vaccination in stroke prevention. We examine the evidence for chronic infection or "infectious burden" as a stroke risk factor. Finally, we discuss recent work on infection as a risk factor for increased morbidity after stroke, possible mechanisms mediating this effect, and the evidence for prophylactic antibiotics.

Circumstances surrounding the onset of stroke: a qualitative study

AIM

To document perceptions of circumstances spontaneously associated with the occurrence of the stroke on that particular day.

BACKGROUND

Known triggers of stroke include birthday or negative emotions. However, specific circumstances relating to that birthday or emotion have not yet been documented.

DESIGN

Phenomenological perspective where data were collected between October 2011-June 2012.

METHOD

In-depth interviews conducted 5-8 weeks post stroke with 37 participants, with a mean age of 56·3 years (sd 11·9) and 40·5% (14/37) of whom were female. An interview guide composed of open-ended questions and developed with experts was used to explore in detail free associations surrounding the stroke. All interviews were audiotaped and transcribed. Data were rigorously analysed by two team members and discussed in team meetings until reaching consensus on essential themes.

FINDINGS

Relationships emerged as being the overarching theme related to stroke triggers with the interrelated subthemes of: (1) birthday or anniversary; (2) parenting; (3) being sick seen as a benefit; and (4) alcohol or drug abuse. The stroke happened on a day which was related in some way to a relationship with a significant other affected by tension, a lack of transparency or an overinvestment of emotional/affective state.

CONCLUSIONS

There is a need to address individuals' beliefs as a part of secondary prevention interventions to be truly client-centred, which the phenomenological perspective allows. Relationships as a potential source of stress should be added as a theme to discuss with patients for a holistic approach to stroke prevention including psychosocial factors.

Changes in Depressive Symptoms and Incidence of First Stroke Among Middle-Aged and Older US Adults

Background

Although research has demonstrated that depressive symptoms predict stroke incidence, depressive symptoms are dynamic. It is unclear whether stroke risk persists if depressive symptoms remit.

Methods and Results

Health and Retirement Study participants (n=16 178, stroke free and noninstitutionalized at baseline) were interviewed biennially from 1998 to 2010. Stroke and depressive symptoms were assessed through self-report of doctors’ diagnoses and a modified Center for Epidemiologic Studies - Depression scale (high was ≥3 symptoms), respectively. We examined whether depressive symptom patterns, characterized across 2 successive interviews (stable low/no, onset, remitted, or stable high depressive symptoms) predicted incident stroke (1192 events) during the subsequent 2 years. We used marginal structural Cox proportional hazards models adjusted for demographics, health behaviors, chronic conditions, and attrition. We also estimated effects stratified by age (≥65 years), race or ethnicity (non-Hispanic white, non-Hispanic black, Hispanic), and sex. Stroke hazard was elevated among participants with stable high (adjusted hazard ratio 2.14, 95% CI 1.69 to 2.71) or remitted (adjusted hazard ratio 1.66, 95% CI 1.22 to 2.26) depressive symptoms compared with participants with stable low/no depressive symptoms. Stable high depressive symptom predicted stroke among all subgroups. Remitted depressive symptoms predicted increased stroke hazard among women (adjusted hazard ratio 1.86, 95% CI 1.30 to 2.66) and non-Hispanic white participants (adjusted hazard ratio 1.66, 95% CI 1.18 to 2.33) and was marginally associated among Hispanics (adjusted hazard ratio 2.36, 95% CI 0.98 to 5.67).

Conclusions

In this cohort, persistently high depressive symptoms were associated with increased stroke risk. Risk remained elevated even if depressive symptoms remitted over a 2-year period, suggesting cumulative etiologic mechanisms linking depression and stroke.

Circumstances surrounding stroke onset: symbolic meaning of time factors related to numbers and days of the week

PURPOSE

To explore the circumstances surrounding the onset of stroke, and especially the symbolic meaning of time factors related to numbers and days of the week.

METHOD

Phenomenological qualitative study involving individual interviews conducted 5-8 weeks post-stroke. The audiotaped interviews were transcribed, then comprehensively coded by two team members, and summaries of each case were written. Since this was a secondary analysis, special attention was paid to the significance of themes, numbers and days of the week when analyzing the summaries and transcripts.

RESULTS

Interviews were conducted with 37 participants (mean age 56.3 ± 11.9 years, 60% male). Five themes were identified with respect to the meaning attributed to numbers: (1) personal events, (2) historical events, (3) annual events, (4) age, and (5) avoidance. Themes identified as being associated with days of the week were work, leisure activities, household chores and medical tests/appointments.

CONCLUSION

The impact of internalised emotions related to these perceptions can be quite significant. This study suggests that health professionals should personalise the secondary prevention of strokes by considering clients holistically and also give clients the opportunity to freely express their feelings about the meaning of time factors to foster awareness of their own perceptions.

IMPLICATIONS FOR REHABILITATION

The use of checklists only for stroke secondary prevention does not allow taking into account psychosocial factors as potential precipitating factors. An open dialogue about personal circumstances starting on the date and day the stroke happened enabled the emergence of meaningful themes. As relationships emerged as the overarching essential theme, quality of relationships could be addressed in rehabilitation post-stroke and thus potentially contribute to prevent stroke recurrence.

Triggering of stroke by ambient temperature variation: a case-crossover study in Maputo, Mozambique

OBJECTIVES

The effect of ambient temperature as a stroke trigger is likely to differ by type of stroke and to depend on non-transient exposures that influence the risk of this outcome. We aimed to quantify the association between ambient temperature variation and stroke, according to clinical characteristics of the events, and other risk factors for stroke.

METHODS

We conducted a case-crossover study based on a 1-year registry of the hospital admissions due to newly occurring ischemic and hemorrhagic stroke events in Maputo, Mozambique's capital city (N=593). The case-period was defined as the 7 days before the stroke event, which was compared to two control periods (14-21 days and 21-28 days before the event). We computed humidity- and precipitation-adjusted odds ratios (OR) and 95% confidence intervals (95%CI) using conditional logistic regression.

RESULTS

An association between minimum temperature declines higher than 2.4 °C in any two consecutive days in the previous week and the occurrence of stroke was observed only for first events (OR=1.43, 95%CI: 1.15-1.76). Stronger and statistically significant associations were observed for hemorrhagic stroke (OR=1.50, 95%CI: 1.07-2.09) and among subjects not exposed to risk factors, including smoking, high serum cholesterol or atrial fibrillation. No differences in the effect of temperature were found according to the patients' vital status 28 days after the event.

CONCLUSIONS

First stroke events, especially of the hemorrhagic type, were triggered by declines in the minimum temperature between consecutive days of the preceding week.

The role of the cerebral capillaries in acute ischemic stroke: the extended penumbra model

The pathophysiology of cerebral ischemia is traditionally understood in relation to reductions in cerebral blood flow (CBF). However, a recent reanalysis of the flow-diffusion equation shows that increased capillary transit time heterogeneity (CTTH) can reduce the oxygen extraction efficacy in brain tissue for a given CBF. Changes in capillary morphology are typical of conditions predisposing to stroke and of experimental ischemia. Changes in capillary flow patterns have been observed by direct microscopy in animal models of ischemia and by indirect methods in humans stroke, but their metabolic significance remain unclear. We modeled the effects of progressive increases in CTTH on the way in which brain tissue can secure sufficient oxygen to meet its metabolic needs. Our analysis predicts that as CTTH increases, CBF responses to functional activation and to vasodilators must be suppressed to maintain sufficient tissue oxygenation. Reductions in CBF, increases in CTTH, and combinations thereof can seemingly trigger a critical lack of oxygen in brain tissue, and the restoration of capillary perfusion patterns therefore appears to be crucial for the restoration of the tissue oxygenation after ischemic episodes. In this review, we discuss the possible implications of these findings for the prevention, diagnosis, and treatment of acute stroke.

The effect of season and temperature variation on hospital admissions for incident stroke events in Maputo, Mozambique

BACKGROUND

Identifying locale-specific patterns regarding the variation in stroke incidence throughout the year and with atmospheric temperature may be useful to the organization of stroke care, especially in low-resource settings.

GOAL

We aimed to describe the variation in the incidence of stroke hospitalizations across seasons and with short-term temperature variation, in Maputo, Mozambique.

METHODS

Between August 1, 2005, and July 31, 2006, we identified 651 stroke events in Maputo dwellers, according to the World Health Organization's STEPwise approach. The day of symptom onset was defined as the index date. We computed crude and adjusted (humidity, precipitation and temperature) incidence rate ratios (IRRs) and 95% confidence intervals (CIs) with Poisson regression.

RESULTS

Stroke incidence did not vary significantly with season (dry versus wet: crude IRR = .98, 95% CI: .84-1.15), atmospheric temperature at the index date, or average atmospheric temperature in the preceding 2 weeks. The incidence rates of stroke were approximately 30% higher when in the previous 10 days there was a decline in the minimum temperature greater than or equal to 3 °C between any 2 consecutive days (variation in minimum temperature -5.1 to -3.0 versus -2.3 to -.4, adjusted IRR = 1.31, 95% CI: 1.09-1.57). No significant associations were observed according to the variation in maximum temperatures.

CONCLUSIONS

Sudden declines in the minimum temperatures were associated with a higher incidence of stroke hospitalizations in Maputo. This provides important information for prediction of periods of higher hospital affluence because of stroke and to understand the mechanisms underlying the triggering of a stroke event.

Psychosocial distress and stroke risk in older adults

BACKGROUND AND PURPOSE

To investigate the association of psychosocial distress with risk of stroke mortality and incident stroke in older adults.

METHODS

Data were from the Chicago Health and Aging Project, a longitudinal population-based study conducted in 3 contiguous neighborhoods on the south side of Chicago, IL. Participants were community-dwelling black and non-Hispanic white adults, aged 65 years and older (n=4120 for stroke mortality; n=2649 for incident stroke). Psychosocial distress was an analytically derived composite measure of depressive symptoms, perceived stress, neuroticism, and life dissatisfaction. Cox proportional hazards models examined the association of distress with stroke mortality and incident stroke over 6 years of follow-up.

RESULTS

Stroke deaths (151) and 452 incident strokes were identified. Adjusting for age, race, and sex, the hazard ratio (HR) for each 1-SD increase in distress was 1.47 (95% confidence interval [CI]=1.28-1.70) for stroke mortality and 1.18 (95% CI=1.07-1.30) for incident stroke. Associations were reduced after adjustment for stroke risk factors and remained significant for stroke mortality (HR=1.29; 95% CI=1.10-1.52) but not for incident stroke (HR=1.09; 95% CI=0.98-1.21). Secondary analyses of stroke subtypes showed that distress was strongly related to incident hemorrhagic strokes (HR=1.70; 95% CI=1.28-2.25) but not ischemic strokes (HR=1.02; 95% CI=0.91-1.15) in fully adjusted models.

CONCLUSIONS

Increasing levels of psychosocial distress are related to excess risk of both fatal and nonfatal stroke in older black and white adults. Additional research is needed to examine pathways linking psychosocial distress to cerebrovascular disease risk.

Epidemiology and risk factors

PURPOSE OF REVIEW

: This article presents current knowledge on stroke epidemiology. It covers recent data on the global burden of stroke, disparities, silent stroke, traditional and novel risk factors, and stroke triggers as well as the clinical implications of these findings.

RECENT FINDINGS

: Stroke is the third leading cause of death and the leading cause of chronic disability in the United States, and the burden of stroke worldwide is even greater. Large international and US case-control and prospective cohort studies have demonstrated disparities in stroke mortality and incidence. They have also shed light on the relative importance of several well-established, modifiable risk factors for ischemic stroke, such as hypertension, atrial fibrillation, other cardiac diseases, hyperlipidemia, diabetes, cigarette smoking, physical inactivity, alcohol consumption, abdominal obesity, diet, and TIA. Research on other putative stroke risk factors (including inflammation, infection, renal disease, depression, stress, and others) is ongoing. Identifying stroke triggers may be another way to minimize stroke incidence if high-risk time windows can be determined.

SUMMARY

: Stroke is a major global health burden. While many of the risk factors for stroke are well known and have been studied for decades, recent studies continue to shed light on the distribution and severity of these problems.

Stressful Life Events as Triggers of Ischemic Stroke: A Case-Crossover Study

Background

Acute stressors, such as stressful life events, might trigger ischemic stroke.

Aims

Our objective was to investigate the association between life events exposure and ischemic stroke onset.

Methods

Consecutive patients were interviewed about life events exposure (e.g. bereavement) using the Interview for Recent Life Events. Using a case-crossover approach, life events exposure within one month of stroke onset (hazard period) was compared with exposure during five control periods of one month preceding the hazard period. Similarly, life events exposure within one week of stroke onset was compared with exposure during three control periods of one week. Odds ratios and 95% confidence intervals were calculated using conditional logistic regression.

Results

Two hundred forty-seven patients were interviewed within a median time of five days (interquartile range 3–7). Life events belonging to bereavement, health, and other categories accounted for half of life events. Over the six-month period, 187 patients were exposed to ≥1 life events. Patients were exposed to ≥1 life events more often during the first month preceding stroke onset than during the five control periods (odds ratio = 2·96; 95% confidence interval, 2·19–4·00). Over the four-week period, 97 patients were exposed to ≥1 life events. Patients were exposed to ≥1 life events more often during the first week preceding stroke onset than during the three control periods (odds ratio = 2·10; 1·40–3·17).

Conclusions

Recent life events exposure is associated with an increased risk of ischemic stroke.

Hospitalization for infection and risk of acute ischemic stroke: the Cardiovascular Health Study

BACKGROUND AND PURPOSE

Little is known about the acute precipitants of ischemic stroke, although evidence suggests infections contribute to risk. We hypothesized that acute hospitalization for infection is associated with the short-term risk of stroke.

METHODS

The case-crossover design was used to compare hospitalization for infection during case periods (90, 30, or 14 days before an incident ischemic stroke) and control periods (equivalent time periods exactly 1 or 2 years before stroke) in the Cardiovascular Health Study, a population-based cohort of 5888 elderly participants from 4 US sites. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by conditional logistic regression. Confirmatory analyses assessed hazard ratios of stroke from Cox regression models, with hospitalization for infection as a time-varying exposure.

RESULTS

During a median follow-up of 12.2 years, 669 incident ischemic strokes were observed in participants without a baseline history of stroke. Hospitalization for infection was more likely during case than control time periods; for 90 days before stroke, OR=3.4 (95% CI, 1.8 to 6.5). The point estimates of risks were higher when we examined shorter intervals: for 30 days, OR=7.3 (95% CI, 1.9 to 40.9), and for 14 days, OR=8.0 (95% CI, 1.7 to 77.3). In survival analyses, risk of stroke was associated with hospitalization for infection in the preceding 90 days, adjusted hazard ratio=2.4 (95% CI, 1.6 to 3.4).

CONCLUSIONS

Hospitalization for infection is associated with a short-term increased risk of stroke, with higher risks observed for shorter intervals preceding stroke.

Depressive symptoms predict incident stroke independently of memory impairments

BACKGROUND

We evaluated whether depressive symptoms predict the onset of first stroke independently of memory impairment. We conceptualized memory impairment as a marker of preexisting cerebrovascular disease. We hypothesized that if depressive symptoms are causally related to stroke through mechanisms unrelated to cerebrovascular disease, depressive symptoms should predict stroke independently of memory impairment.

METHODS

Incidence of first stroke was assessed with self or proxy reports from 19,087 participants in the Health and Retirement Study cohort (1,864 events). Elevated depressive symptoms (3+ on an 8-item Centers for the Epidemiologic Study of Depression scale) and memory impairment (score of ≤6 on a combined immediate and delayed recall of a 10-word list) were used as predictors of incident stroke in Cox survival models with adjustment for sociodemographic and cardiovascular risk factors.

RESULTS

After adjustment for sociodemographic and cardiovascular risk factors, elevated depressive symptoms (hazard ratio = 1.25; 95% confidence interval 1.12-1.39) and memory impairment (hazard ratio = 1.26; 95% confidence interval 1.13-1.41) each predicted stroke incidence in separate models. Hazard ratios were nearly unchanged and remained significant (1.23 for elevated depressive symptoms and 1.25 for memory impairment) when models were simultaneously adjusted for both elevated depressive symptoms and memory impairment. Elevated depressive symptoms also predicted stroke when restricting analyses to individuals with median memory score or better.

CONCLUSIONS

Memory impairments and depressive symptoms independently predict stroke incidence. Memory impairment may reflect undiagnosed cerebrovascular disease. These results suggest that depressive symptoms might be directly related to stroke rather than merely indicating preexisting cerebrovascular disease.

Inflammatory mechanisms of stroke

Basic and clinical research provides evidence that inflammatory mechanisms play a central role in the pathogenesis and progression of atherosclerosis, plaque rupture, thrombosis, and stroke. Inflammatory biomarkers such as high-sensitivity C-reactive protein have been identified as predictors of first stroke and prognosis after stroke. The value of high-sensitivity C-reactive protein and other markers may depend on the characteristics of the study population; their utility may be less among populations with high vascular risk. A recent randomized, clinical trial suggests that the use of rosuvastatin therapy in otherwise healthy patients with high-sensitivity C-reactive protein >2 mg/dL can reduce the risk of a first stroke by 50%. The prognostic role of high-sensitivity C-reactive protein among patients after stroke, however, is less clear, and other biomarkers, including lipoprotein-associated phospholipase A(2), may provide complementary information about the risk of stroke recurrence. Infections, moreover, may contribute to inflammation and stroke risk. Although no single infectious organism is likely to be identified as the direct cause of atherosclerosis, summary measures of multiple chronic infectious exposures, or "infectious burden," have been associated with the risk of stroke and atherosclerosis affecting the carotid arteries. Acute infections have also been found to serve as stroke triggers in epidemiologic studies. Recommendations to vaccinate patients with cardiovascular disease against influenza represent the first specific anti-infective strategy to be used in vascular prophylaxis. Further studies are needed to determine the role of treatment of inflammation and infection in stroke prevention.

Which dietary and lifestyle behaviours may be important in the aetiology (and prevention) of stroke?

Prevention of stroke requires optimal control of causal risk factors. However, only three-quarters of all strokes can be attributable to known causal risk factors. We aimed to identify novel risk factors for acute stroke in 48 patients with acute (<1 week) stroke admitted to Royal Perth Hospital Stroke Unit and 47 controls matched for age and sex from the northeast Perth metropolitan area. Patients and controls were interviewed, and had physical measurements and blood taken. Multiple odds ratios (OR) for risk factors, with 95% confidence intervals (CI), were calculated by unconditional multiple logistic regression. Mediterranean diet (OR: 0.1; 95% CI, 0.02-0.4), increased waist-to-hip ratio (OR 4.0, 95% CI, 1.5-11), physical activity during leisure time (OR 0.2; 95% CI, 0.1-0.9), periodontal disease (OR 6.4; 95% CI, 1.5-27), and acute febrile illness (OR 14; 95% CI, 1.5-127) were associated significantly and independently with ischaemic stroke. These preliminary data suggest that certain dietary and lifestyle behaviours may play as important a role in the aetiology (and prevention) of stroke as other conventional causal risk factors for stroke. However, these associations need confirmation from larger randomised trials given the small sample size of the current study.

The science of stroke: mechanisms in search of treatments

This review focuses on mechanisms and emerging concepts that drive the science of stroke in a therapeutic direction. Once considered exclusively a disorder of blood vessels, growing evidence has led to the realization that the biological processes underlying stroke are driven by the interaction of neurons, glia, vascular cells, and matrix components, which actively participate in mechanisms of tissue injury and repair. As new targets are identified, new opportunities emerge that build on an appreciation of acute cellular events acting in a broader context of ongoing destructive, protective, and reparative processes. The burden of disease is great, and its magnitude widens as a role for blood vessels and stroke in vascular and nonvascular dementias becomes more clearly established. This review then poses a number of fundamental questions, the answers to which may generate new directions for research and possibly new treatments that could reduce the impact of this enormous economic and societal burden.

IL-6 as a biomarker of ischemic cerebrovascular disease

The lack of a rapid and clinically accurate diagnostic tool remains a major obstacle to optimal care of patients with stroke. Cytokine changes in patients with acute stroke have been insufficiently studied. The purpose of this study is to delineate the relevance of IL-6 as a biochemical marker of stroke diagnosis, taking into account the genetic basis, and changes of the protein in serum and cerebrospinal fluid in relation to stroke development. Inflammation has an important role in ischemic cerebrovascular disease pathophysiology. Proinflammatory cytokines, such as IL-6, have been implicated in several mechanisms that might promote ischemic brain injury and an early neurological worsening. Cardiovascular diseases constitute one of the principal health problems in developing countries. Over the past few years, several studies have found evidence of the important role of inflammation in the ischemic cerebrovascular disease. The availability of a diagnostic biomarker panel for patients with stroke symptoms would be enormously valuable to complement clinical data and to precede radiological findings. IL-6 levels in cerebrospinal fluid and serum seem to reflect either the extent of tissue damage, or the accompanying clinical worsening. The -174 G/C functional polymorphism in the IL-6 gene might not be solely involved in disease susceptibility but also in linkage disequilibrium with other functional polymorphisms. Further studies are needed to solve this. Presently, the association between IL-6 genotype and stroke remains undetermined. Development of new neuroprotective therapies targeted to modulate cytokine-induced inflammation could be a promising way to prevent early deterioration in acute ischemic stroke.

Posterior reversible encephalopathy syndrome and cerebral vasculopathy associated with influenza A infection: report of a case and review of the literature

BACKGROUND AND PURPOSE

Influenza A infection can precipitate encephalopathy, encephalitis, or Reye syndrome with the development of cerebral edema in children and is associated with an increased incidence of stroke in adults. The mechanism of these events is poorly understood. Posterior reversible encephalopathy syndrome (PRES) is seen in association with infection/sepsis, and cerebral vasculopathy has been demonstrated in PRES. We describe a case of PRES that develops in association with influenza A.

SUMMARY OF CASE

A normotensive 65-year-old woman presented with altered mentation and nausea in the setting of a viral prodromal illness ultimately confirmed as influenza A. Posterior reversible encephalopathy syndrome developed on the second day after admission. Catheter cerebral angiogram documented vasculopathy in PRES-involved regions with areas of focal vessel dilatation and string-of-bead appearance.

CONCLUSIONS

The association between influenza A and PRES with documentation of cerebral vasculopathy suggests a common systemic vascular mechanism behind PRES and influenza-related encephalopathic edema and stroke.

Influenza A encephalopathy, cerebral vasculopathy, and posterior reversible encephalopathy syndrome: combined occurrence in a 3-year-old child

Encephalopathy is an uncommon complication of childhood influenza infection, typically recognized during influenza epidemics. Imaging hallmarks include characteristic thalamic lesions, thalamic necrosis and hemispheric edema. We describe a child with acute influenza A associated necrotizing encephalopathy with MR angiographic evidence of significant cerebral vasculopathy and a hemispheric edema pattern consistent with PRES. This case reinforces that significant cerebral vasculopathy can accompany influenza infection and that influenza is a likely trigger for PRES.

The autonomic nervous system and ischemic stroke: a reciprocal interdependence

Signs and symptoms of autonomic nervous system (ANS) dysfunction are frequently reported after ischemic or haemorrhagic stroke and in many cases they exhibit peculiar patterns in relationship with the site and the extension of brain lesion. However if an ANS disorder can cause or predispose to a stroke is far from being correctly known. Evidences in favor of a pathogenetic mechanism of an ANS dysfunction are reported for myocardial infarction and such data are likely to be appropriate also for atherothrombotic type of ischemic stroke. On the other hand, it is well known that many risk factors for this pathology are strongly correlated with an altered functioning of ANS so that a reciprocal interdependence between ANS and stroke can be hypothesized. This review points to evidence the possible relationship existing between these two conditions and suggests a quite different diagnostic and therapeutic approach to both on the basis of their pathogenetic mechanisms.

Systemic infection, inflammation and acute ischemic stroke

Extensive evidence implicates inflammation in multiple phases of stroke etiology and pathology. In particular, there is growing awareness that inflammatory events outside the brain have an important impact on stroke susceptibility and outcome. Numerous conditions, including infection and chronic non-infectious diseases, that are established risk factors for stroke are associated with an elevated systemic inflammatory profile. Recent clinical and pre-clinical studies support the concept that the systemic inflammatory status prior to and at the time of stroke is a key determinant of acute outcome and long-term prognosis. Here, we provide an overview of the impact of systemic inflammation on stroke susceptibility and outcome. We discuss potential mechanisms underlying the impact on ischemic brain injury and highlight the implications for stroke prevention, therapy and modeling.

Gene expression in peripheral blood differs after cardioembolic compared with large-vessel atherosclerotic stroke: biomarkers for the etiology of ischemic stroke

There are no biomarkers that differentiate cardioembolic from large-vessel atherosclerotic stroke, although the treatments differ for each and approximately 30% of strokes and transient ischemic attacks have undetermined etiologies using current clinical criteria. We aimed to define gene expression profiles in blood that differentiate cardioembolic from large-vessel atherosclerotic stroke. Peripheral blood samples were obtained from healthy controls and acute ischemic stroke patients (<3, 5, and 24 h). RNA was purified, labeled, and applied to Affymetrix Human U133 Plus 2.0 Arrays. Expression profiles in the blood of cardioembolic stroke patients are distinctive from those of large-vessel atherosclerotic stroke patients. Seventy-seven genes differ at least 1.5-fold between them, and a minimum number of 23 genes differentiate the two types of stroke with at least 95.2% specificity and 95.2% sensitivity for each. Genes regulated in large-vessel atherosclerotic stroke are expressed in platelets and monocytes and modulate hemostasis. Genes regulated in cardioembolic stroke are expressed in neutrophils and modulate immune responses to infectious stimuli. This new method can be used to predict whether a stroke of unknown etiology was because of cardioembolism or large-vessel atherosclerosis that would lead to different therapy. These results have wide ranging implications for similar disorders.

Acute ischaemic stroke and infection: recent and emerging concepts

The relation between acute ischaemic stroke and infection is complex. Infection appears to be an important trigger that precedes up to a third of ischaemic strokes and can bring about stroke through a range of potential mechanisms. Infections that present subsequent to stroke also complicate up to a third of cases of stroke and might worsen outcome. Inflammatory responses, which are a defence mechanism against infection but can also be a pathogenic mechanism that precipitates stroke and neurological sequelae, are important features. Although factors such as stroke severity and dysphagia are important predictors of poststroke infection, there is evidence from experimental and clinical settings of impaired immunity or brain-induced immunodepression after stroke. Greater understanding of the relation between inflammation and both infection and ischaemic mechanisms is needed. This might be particularly important because new treatment strategies for acute ischaemic stroke are being investigated, including those that modulate cytokines and the immune system.