Silent brain infarcts: a systematic review

Age-related changes in white matter lesions, hippocampal atrophy, and cerebral microbleeds in healthy subjects without major cerebrovascular risk factors

Although cumulative evidence indicates that risk factors for arteriosclerosis have an impact on age-related changes in brain pathology, the influence of aging without major risk factors on changes in brain structures has not yet been fully elucidated. We used magnetic resonance imaging (MRI) to study how aging affects structural changes in the brain (eg, white matter lesions, hippocampal atrophy [HA], microbleeds) in normal subjects without major risk factors for cerebrovascular diseases. We studied 1108 subjects who underwent voluntary brain screening and had no cerebrovascular risk factors, such as hypertension, diabetes mellitus, or hyperlipidemia. We examined the conventional and T2-weighted MRI to define white matter hyperintensities, HA, and cerebral microbleeds in addition to all physical parameters, blood biochemical data, and neuropsychiatric symptoms. We found that the prevalence of white matter lesions and HA increased significantly with age (P < .001). Logistic analysis showed that periventricular hyperintensity was significantly related to age (P < .0001) and depressive state (P < .01). A linear relation was found between white matter lesions and HA (P < .05). Cerebral microbleeds also increased with age, and their presence was associated with HA (P < .001). White matter lesions, HA, and cortical microbleeds were associated with one another in healthy elderly subjects, and these changes were affected by the aging process independent of any cerebrovascular risk factors. Cerebral amyloid angiopathy may underlie these age-related brain changes.

Blood pressure lowering with valsartan is associated with maintenance of cerebral blood flow and cerebral perfusion reserve in hypertensive patients with cerebral small vessel disease

BACKGROUND

The purpose of this study was to determine the effect of systemic blood pressure-lowering treatment with an angiotensin II receptor blocker, valsartan, on cerebral hemodynamics in patients with hypertension and evidence of cerebral small vessel disease.

METHODS

We used positron emission tomography and acetazolamide challenge tests to measure cerebral blood flow (CBF) and cerebrovascular reserve (CVR) in 8 patients with hypertension (mean age 70.8 years) with lacunar infarcts and white matter lesions before and after valsartan therapy.

RESULTS

Systemic blood pressure was significantly decreased from baseline after treatment with valsartan. The baseline global CBFs before and after treatment were 38.2 +/- 5.6 mL/min/100 g and 39.9 +/- 9.0 mL/min/100 g, respectively. The CVRs before and after treatment were 52.2 +/- 18.4% and 39.7 +/- 18.9%, respectively. Differences in these parameters were not significant. Both regional CBF and CVR in the corona radiata with moderate or severe white matter lesions were also preserved after valsartan therapy compared with those before treatment.

CONCLUSIONS

Cerebral hemodynamics were preserved after blood pressure lowering with valsartan therapy. Valsartan could be a feasible antihypertensive regimen in terms of cerebral circulation in patients with cerebral small vessel disease.

Retinal microvascular abnormalities and subclinical magnetic resonance imaging brain infarct: a prospective study

Silent brain infarct and white matter lesions are common radiological findings associated with the risk of clinical stroke and dementia; however, our understanding of their underlying pathophysiology and risk factors remains limited. This study aimed to determine whether assessment of retinal microvascular abnormalities could provide prognostic information regarding the risk of brain infarct and white matter lesions on magnetic resonance imaging. This study is based on a subset of 810 middle-aged persons without clinical stroke or baseline magnetic resonance imaging infarct enrolled in the Atherosclerosis Risk in Communities Brain Magnetic Resonance Imaging Study, a prospective, population-based study. Participants had a baseline magnetic resonance imaging brain examination and retinal photography in 1993-1995, and returned for a repeat magnetic resonance imaging examination in 2004-2006. Magnetic resonance images were graded for presence of any cerebral infarct, infarct with lacunar characteristics and white matter lesions according to standardized protocols. Retinal photographs were graded for presence of retinopathy lesions and retinal arteriolar abnormalities following a standardized protocol. Over a median follow-up of 10.5 years, 164 (20.2%) participants developed cerebral infarct, 131 (16.2%) developed lacunar infarct, 182 (24.2%) developed new white matter lesions and 49 (6.1%) had evidence of white matter lesion progression. After adjusting for age, gender, race, cardiovascular risk factors and carotid intima-media thickness, retinopathy was associated with incident cerebral infarct (odds ratio 2.82; 95% confidence interval 1.42-5.60) and lacunar infarct (odds ratio 3.19; 95% confidence interval: 1.56-6.50). Retinal arteriovenous nicking was associated with incident cerebral infarct (odds ratio 2.82; 95% confidence interval: 1.66-4.76), lacunar infarct (odds ratio 2.48; 95% confidence interval: 1.39-4.40) and white matter lesion incidence (odds ratio 2.12; 95% confidence interval: 1.18-3.81) and progression (odds ratio 2.22; 95% confidence interval: 1.00-5.88). In conclusion, retinal microvascular abnormalities are associated with emergence of subclinical magnetic resonance imaging brain infarcts and white matter lesions, independent of shared risk factors. Retinal vascular imaging may offer a non-invasive tool to investigate the pathogenesis and natural history of cerebral small-vessel disease.

Relationship between chronic kidney disease and silent cerebral infarction in patients with Type 2 diabetes

AIMS

Silent cerebral infarction (SCI) is an independent risk factor for future symptomatic stroke. Although the prevalence of SCI is closely related to kidney function in non-diabetic individuals, evidence is lacking whether albuminuria and/or reduced estimated glomerular filtration rate (eGFR) independently increase the risk of SCI in diabetic patients. We therefore examined the relationships between albuminuria, eGFR and SCI in patients with Type 2 diabetes mellitus (T2DM).

METHODS

We studied 786 T2DM patients with an eGFR > or = 15 ml/min 1.73/m(2), including 337 women and 449 men [mean (+/- sd), age 65 +/- 11 years]. All patients underwent cranial magnetic resonance imaging (MRI) to detect SCI. GFR was estimated using the modified three-variable equation for Japanese subjects. Albuminuria was defined as a first morning urinary albumin-to-creatinine ratio (ACR) > or = 30 mg/g.

RESULTS

SCI was detected in 415 (52.8%) of the subjects. The prevalence of SCI was significantly associated with both elevated ACR and decreased eGFR in univariate analysis. In multivariate logistic regression analysis, urinary ACR remained independently associated with SCI after adjusting for conventional cardiovascular risk factors [odds ratio (OR) of urinary ACR per logarithmical value: 1.89, 95% confidence interval (CI) = 1.41-2.51, P < 0.001]; however, eGFR was no longer significantly associated with SCI (OR per ml/min 1.73/m(2) = 0.99, 95% CI = 0.98-1.00, P = 0.095).

CONCLUSION

In conclusion, albuminuria but not decreased eGFR may be an independent predictor of prevalent SCI in patients with T2DM.

Sex differences in the risk profile and male predominance in silent brain infarction in community-dwelling elderly subjects: the Sefuri brain MRI study

Although brain infarction is more common in men, the male predominance of silent brain infarction (SBI) was inconsistent in the earlier studies. This study was to examine the relationship between sex differences in the risk profile and SBI. We conducted a population-based, cross-sectional analysis of cardiovascular risk factors and SBI on MRI. We asked all the female participants about the age at natural menopause and parity. SBI was detected in 77 (11.3%) of 680 participants (266 men and 414 women) with a mean age of 64.5 (range 40-93) years. In the logistic analysis, age (odds ratio (OR)=2.760/10 years, 95% confidence interval (CI)=2.037-3.738), hypertension (OR=3.465, 95% CI=1.991-6.031), alcohol intake (OR=2.494, 95% CI=1.392-4.466) and smoking (OR=2.302, 95% CI=1.161-4.565) were significant factors concerning SBI. Although SBI was more prevalent among men, this sex difference disappeared on the multivariate model after adjustment for other confounders. In 215 women aged 60 years or older, age at natural menopause, early menopause, duration of menopause, number of children and age at the last parity were not significantly associated with SBI after adjustment for age. Hypertension and age were considered to be the major risk factors for SBI in community-dwelling people. Male predominance in SBI was largely due to higher prevalence of alcohol habit and smoking in men than in women in our population.

A systematic review of dynamic cerebral and peripheral endothelial function in lacunar stroke versus controls

BACKGROUND AND PURPOSE

The etiology of cerebral small vessel disease is unknown. An association with endothelial dysfunction has been suggested. We systematically assessed all relevant studies of dynamic endothelial function in patients with lacunar stroke as a marker of small vessel disease.

METHODS

We searched for studies of cerebral or peripheral vascular reactivity in patients with lacunar or cortical (ie, large artery atheromatous) ischemic stroke or nonstroke control subjects. We calculated standardized mean difference (SMD) in vascular reactivity+/-95% CIs between small vessel disease and control groups.

RESULTS

Sixteen publications (974 patients) were included. In lacunar stroke, cerebrovascular reactivity (n=534) was reduced compared with age-matched normal (SMD -0.94, 95% CI -1.17 to -0.70), but not age+risk factor-matched control subjects (SMD 0.08, 95% CI -0.36 to 0.53) or cortical strokes (SMD -0.29, 95% CI -0.69 to 0.11); forearm flow-mediated dilatation (n=401) was reduced compared with age-matched normal control subjects (SMD -1.04, 95% CI -1.33 to -0.75) and age+risk factor-matched control subjects (SMD -0.94, 95% CI -1.26 to -0.61), but not cortical strokes (SMD -0.23, 95% CI -0.55 to 0.08).

CONCLUSIONS

Endothelial dysfunction is present in patients with lacunar stroke but may simply reflect exposure to vascular risk factors and having a stroke, because a similar degree of dysfunction is found in cortical (large artery atheromatous) stroke. Current data do not confirm that endothelial dysfunction is specific to small vessel stroke. Future studies should include control subjects with nonlacunar stroke.

Correlation between images of silent brain infarction, carotid atherosclerosis and white matter hyperintensity, and plasma levels of acrolein, IL-6 and CRP

OBJECTIVE

We found previously that the measurement of plasma levels of protein-conjugated acrolein (PC-Acro) together with IL-6 and CRP can be used to identify silent brain infarction (SBI) with high sensitivity and specificity. The aim of this study was to clarify how three biochemical markers are correlated to SBI, carotid atherosclerosis (CA) and white matter hyperintensity (WMH).

METHODS

The levels of PC-Acro, IL-6 and CRP in plasma were measured by ELISA. SBI and WMH were evaluated by MRI, and CA was evaluated by duplex carotid ultrasonography.

RESULTS

A total of 790 apparently healthy volunteers were classified into 260 control, 214 SBI, 263 CA and 245 WMH subjects, which included 187 subjects with two or three pathologies. When the combined measurements of PC-Acro, IL-6 and CRP were evaluated together with age, using a receiver operating characteristic curve and artificial neural networks, the relative risk value (RRV), an indicator of tissue damage, was in the order SBI with CA (0.90)>SBI (0.80)>CA (0.76)>WMH with CA (0.65)>WMH (0.46)>control (0.14). RRV was also correlated with severity in each group of SBI, CA and WMH.

CONCLUSION

The RRV supports the idea that the degree of risk to develop a stroke is in the order SBI>CA>WMH.

Brain aging and gait

Aging is associated with a reduction in several functions including gait. The preservation of gait is important in order to prevent falls and consequent injury as one gets older. Poorer gait may also be an important marker for health status and a determinant of quality of life in later life. It is now recognized that specific regions of the brain such as the frontal motor, prefrontal and parietal cortices, the basal ganglia and cerebellum play an important role in the initiation, planning, execution and maintenance of gait, in tandem with other neuromuscular factors. Aging and age-related disease may affect areas of the brain that are involved in the regulation of gait. Recent technological advances in brain imaging have enabled the identification of age-related changes occurring in the brain, such as cortical atrophy, brain infarctions or cerebral white matter lesions. There is a small, but growing, amount of research examining the association between these changes and gait. The objective of this review is to summarize the current state of knowledge on the impact of the aging brain on gait, and to identify directions for future research. Such research may lead to the development of interventions aimed at preventing or reducing the effect of brain aging on gait.

Cerebral microvascular disease predicts renal failure in type 2 diabetes

Abnormalities in small renal vessels may increase the risk of developing impaired renal function, but methods to assess these vessels are extremely limited. We hypothesized that the presence of small vessel disease in the brain, which manifests as silent cerebral infarction (SCI), may predict the progression of kidney disease in patients with type 2 diabetes. We recruited 608 patients with type 2 diabetes without apparent cerebrovascular or cardiovascular disease or overt nephropathy and followed them for a mean of 7.5 years. At baseline, 177 of 608 patients had SCI, diagnosed by cerebral magnetic resonance imaging. The risk for the primary outcome of ESRD or death was significantly higher for patients with SCI than for patients without SCI [hazard ratio, 2.44; 95% confidence interval (CI) 1.36 to 4.38]. The risk for the secondary renal end point of any dialysis or doubling of the serum creatinine concentration was also significantly higher for patients with SCI (hazard ratio, 4.79; 95% CI 2.72 to 8.46). The estimated GFR declined more in patients with SCI than in those without SCI; however, the presence of SCI did not increase the risk for progression of albuminuria. In conclusion, independent of microalbuminuria, cerebral microvascular disease predicted renal morbidity among patients with type 2 diabetes.

Predicting recurrent stroke after minor stroke and transient ischemic attack

The risk of a subsequent stroke following an acute transient ischemic attack or minor stroke is high, with 90-day risk at approximately 10%. Identification of those patients at the highest risk for recurrent stroke following a transient ischemic attack or minor stroke may allow risk-specific management strategies to be implemented, such as hospital admission with expedited work-up for those at high risk and emergency room discharge for those at low risk. Predictors of recurrent stroke, including the ABCD2 score, brain imaging and the stroke mechanism, are reviewed in this article, with a focus on recent literature. An emphasis is placed on the importance of early imaging of the brain parenchyma (diffusion-weighted imaging) and vascular imaging to identify patients at high risk for recurrence. The need for identification of the cause of the initial event, allowing therapies to be tailored to the individual patient, is discussed.

Silent cerebral infarction is associated with incident stroke and TIA independent of carotid intima-media thickness

BACKGROUND

Both silent cerebral infarction (SCI) and carotid intima-media thickness (IMT) are associated with future stroke. We evaluated whether SCI could be a predictor for incident stroke independent of carotid IMT in high-risk patients.

METHODS

We performed a prospective cohort study among 282 outpatients who had one or more atherosclerotic risk factors but without a history of cardiovascular disease. We conducted cranial MRI and measured carotid IMT at baseline, and then evaluated the risks of incident stroke and transient ischemic attacks (TIA) using Cox proportional hazards models.

RESULTS

SCI was present in 67 patients (23.7%) at baseline. During 4.1 years of follow-up, stroke and TIA occurred in 8 patients (2.8%). The incidence of stroke/TIA was 22.3 per 1,000 person-years in those with SCI compared with 2.2 per 1,000 person-years in those without SCI. Both SCI and carotid IMT at baseline were associated with incident stroke/TIA events after adjustment for age, sex, and traditional vascular risk factors. The predictive value of SCI remained significant even after adjustment for carotid IMT (HR 8.56; 1.72-42.55).

CONCLUSION

SCI, similar to carotid IMT, is an independent predictor of stroke and TIA in high-risk patients.

Counting cavitating lacunes underestimates the burden of lacunar infarction

BACKGROUND AND PURPOSE

On brain imaging, lacunes, or cerebrospinal fluid-containing cavities, are common and are often counted in epidemiological studies as old lacunar infarcts. The proportion of symptomatic lacunar infarcts that progress to lacunes is unknown. Noncavitating lacunar infarcts may continue to resemble white matter lesions.

METHODS

We identified patients with acute lacunar stroke, with or without an acute lacunar infarct on computed tomography or MRI, who had follow-up imaging. A neuroradiologist classified lacunar infarcts progressing to definite or possible cavities on follow-up imaging. We tested associations between cavitation and patient-related, stroke-related, and imaging-related features, including other features of small vessel disease.

RESULTS

Among 90 patients (mean age 67 years), any cavitation was present on follow-up imaging in 25 (28%), and definite cavitation in 18 (20%). Definite cavitation was associated with increasing time to follow-up imaging (median 228 days, range 54 to 1722, versus no cavitation 72 days, range 6 to 1440; P=0.0003) and deep cerebral atrophy (P=0.03) but not with age, stroke severity, larger initial infarct size, or other features of small vessel disease. Hypertension and diabetes were negatively associated with cavitation (P=0.01 and 0.02, respectively).

CONCLUSIONS

Definite cavitation occurs in one fifth of symptomatic lacunar ischemic strokes, implying that most continue to resemble white matter lesions. Epidemiology and pathophysiology studies of lacunar stroke, which have only counted lacunes as lacunar infarcts, may have substantially underestimated by as much as 5 times the true burden of lacunar stroke disease.

Genome-wide association studies of MRI-defined brain infarcts: meta-analysis from the CHARGE Consortium

BACKGROUND AND PURPOSE

Previous studies examining genetic associations with MRI-defined brain infarct have yielded inconsistent findings. We investigated genetic variation underlying covert MRI infarct in persons without histories of transient ischemic attack or stroke. We performed meta-analysis of genome-wide association studies of white participants in 6 studies comprising the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium.

METHODS

Using 2.2 million genotyped and imputed single nucleotide polymorphisms, each study performed cross-sectional genome-wide association analysis of MRI infarct using age- and sex-adjusted logistic regression models. Study-specific findings were combined in an inverse-variance-weighted meta-analysis, including 9401 participants with mean age 69.7 (19.4% of whom had >or=1 MRI infarct).

RESULTS

The most significant association was found with rs2208454 (minor allele frequency, 20%), located in intron 3 of MACRO domain containing 2 gene and in the downstream region of fibronectin leucine-rich transmembrane protein 3 gene. Each copy of the minor allele was associated with lower risk of MRI infarcts (odds ratio, 0.76; 95% confidence interval, 0.68-0.84; P=4.64x10(-7)). Highly suggestive associations (P<1.0x10(-5)) were also found for 22 other single nucleotide polymorphisms in linkage disequilibrium (r(2)>0.64) with rs2208454. The association with rs2208454 did not replicate in independent samples of 1822 white and 644 black participants, although 4 single nucleotide polymorphisms within 200 kb from rs2208454 were associated with MRI infarcts in the black population sample.

CONCLUSIONS

This first community-based, genome-wide association study on covert MRI infarcts uncovered novel associations. Although replication of the association with top single nucleotide polymorphisms failed, possibly because of insufficient power, results in the black population sample are encouraging, and further efforts at replication are needed.

Ambulatory recorded ST segment depression on ECG is associated with lower cognitive function in healthy elderly men

ST segment depression (STDE) has been found to be associated with cardiovascular disease in the elderly. Studies of the relation of ambulatory STDE to cognitive function in elderly persons aged 80 years or above is lacking.

OBJECTIVE

To study the association between STDE and cognition.

DESIGN AND PARTICIPANTS

A cross-sectional cohort study of 88 81-year-old men from the population study "Men born in 1914" investigated in an outpatient research clinic. Measurements included ambulatory 24-hour electrocardiogram (ECG) monitoring and a cognitive test battery of six tests. Proportion of lower cognitive function was calculated for each test in relation to STDE during the day and at night-time.

RESULTS

Fifty-eight percent of the men had STDE and a higher proportion with low visuospatial cognitive function was found among those with STDE compared to the others (84% vs 59%; p = 0.014). A significant trend was noted for subjects without STDE compared to STDE night-time less than 60 minutes and night-time more than 60 minutes for spatial and verbal cognitive functions (p = 0.022). No trends were noted for STDE daytime. Maximal STDE during night showed similar association to spatial function (Benton Visual Retention test, r = -0.26; p = 0.028). Even when seven subjects with a history of stroke were excluded, the occurrence of STDE was associated to lower visuospatial cognitive function compared to those without STDE (87% vs 57%; p = 0.004).

CONCLUSION

ST segment depression on ECG is common among elderly men and might be a vascular risk factor for cognitive deterioration.

Aortic stiffness is associated with cardiac function and cerebral small vessel disease in patients with type 1 diabetes mellitus: assessment by magnetic resonance imaging

OBJECTIVE

To evaluate, with the use of magnetic resonance imaging (MRI), whether aortic pulse wave velocity (PWV) is associated with cardiac left ventricular (LV) function and mass as well as with cerebral small vessel disease in patients with type 1 diabetes mellitus (DM).

MATERIALS AND METHODS

We included 86 consecutive type 1 DM patients (49 male, mean age 46.9 +/- 11.7 years) in a prospective, cross-sectional study. Exclusion criteria included aortic/heart disease and general MRI contra-indications. MRI of the aorta, heart and brain was performed for assessment of aortic PWV, as a marker of aortic stiffness, systolic LV function and mass, as well as for the presence of cerebral white matter hyperintensities (WMHs), microbleeds and lacunar infarcts. Multivariate linear or logistic regression was performed to analyse the association between aortic PWV and outcome parameters, with covariates defined as age, gender, mean arterial pressure, heart rate, BMI, smoking, DM duration and hypertension.

RESULTS

Mean aortic PWV was 7.1 +/- 2.5 m/s. Aortic PWV was independently associated with LV ejection fraction (ss = -0.406, P = 0.006), LV stroke volume (ss = -0.407, P = 0.001), LV cardiac output (ss = -0.458, P = 0.001), and with cerebral WMHs (P < 0.05). There were no independent associations between aortic stiffness and LV mass, cerebral microbleeds or lacunar infarcts.

CONCLUSION

Aortic stiffness is independently associated with systolic LV function and cerebral WMHs in patients with type 1 DM.

Plasticity during stroke recovery: from synapse to behaviour

Reductions in blood flow to the brain of sufficient duration and extent lead to stroke, which results in damage to neuronal networks and the impairment of sensation, movement or cognition. Evidence from animal models suggests that a time-limited window of neuroplasticity opens following a stroke, during which the greatest gains in recovery occur. Plasticity mechanisms include activity-dependent rewiring and synapse strengthening. The challenge for improving stroke recovery is to understand how to optimally engage and modify surviving neuronal networks, to provide new response strategies that compensate for tissue lost to injury.

Physical activity and subclinical MRI cerebral infarcts: the ARIC Study

BACKGROUND

We hypothesized that physical activity (PA), which is often associated with reduced risk of ischemic stroke, may also be associated with reduced risk of subclinical cerebral infarcts.

OBJECTIVES

We studied the cross-sectional association between PA and subclinical cerebral infarcts among African-Americans in the Atherosclerosis Risk in Communities (ARIC) Study.

METHODS

PA self-reported at baseline and images from cerebral MRI examination obtained 6 years later were evaluated for presence and location of subclinical infarcts > or = 3 mm in size. After exclusions, 944 participants were eligible for study.

RESULTS

The results suggested an inverse relationship between odds of having a subclinical cerebral infarct and level of PA on several measures, although the multivariable adjusted odds ratios (OR) were statistically significant only for the sport score. A 1-unit increase in the sport score, indicating more leisure PA, was associated with an adjusted OR for having a subclinical cerebral infarct of 0.62 (0.44-0.87), with a statistically significant monotonic trend across quartiles of the score (P = 0.01). There was no association of work scores with subclinical infarcts.

CONCLUSIONS

In African-Americans, sport PA was inversely related to subclinical MRI-detected cerebral infarcts assessed six years later.

Do management strategies for coronary artery disease influence 6-year cognitive outcomes?

BACKGROUND

Previous uncontrolled studies have suggested that there is late cognitive decline after coronary artery bypass grafting that may be attributable to use of the cardiopulmonary bypass pump.

METHODS

In this prospective, nonrandomized, longitudinal study, we compared cognitive outcomes after on-pump coronary artery bypass surgery (n = 152) with off-pump bypass surgery patients (n = 75); nonsurgical cardiac comparison subjects (n = 99); and 69 heart-healthy comparison (HHC) subjects. The primary outcome measure was change from baseline to 72 months in the following cognitive domains: verbal memory, visual memory, visuoconstruction, language, motor speed, psychomotor speed, attention, executive function, and a composite global score.

RESULTS

There were no consistent differences in 72-month cognitive outcomes among the three groups with coronary artery disease (CAD). The CAD groups had lower baseline performance, and a greater degree of decline compared with HHC. The degree of change was small, with none of the groups having more than 0.5 SD decline. None of the groups was substantially worse at 72 months compared with baseline.

CONCLUSIONS

Compared with subjects with no vascular disease risk factors, the CAD patients had lower baseline cognitive performance and greater degrees of decline over 72 months, suggesting that in these patients, vascular disease may have an impact on cognitive performance. We found no significant differences in the long-term cognitive outcomes among patients with various CAD therapies, indicating that management strategy for CAD is not an important determinant of long-term cognitive outcomes.

Incidental findings on brain magnetic resonance imaging: systematic review and meta-analysis

OBJECTIVE

To quantify the prevalence of incidental findings on magnetic resonance imaging (MRI) of the brain.

DESIGN

Systematic review and meta-analysis of observational studies.

DATA SOURCES

Ovid Medline (1950 to May 2008), Embase (1980 to May 2008), and bibliographies of relevant articles. Review methods Two reviewers sought and assessed studies of people without neurological symptoms who underwent MRI of the brain with or without intravenous contrast for research purposes or for occupational, clinical, or commercial screening.

MAIN OUTCOME MEASURES

Overall disease specific and age specific prevalence of incidental brain findings, calculated by meta-analysis of pooled proportions using DerSimonian-Laird weights in a random effects model.

RESULTS

In 16 studies, 135 of 19 559 people had neoplastic incidental brain findings (prevalence 0.70%, 95% confidence interval 0.47% to 0.98%), and prevalence increased with age (chi(2) for linear trend, P=0.003). In 15 studies, 375 of 15 559 people had non-neoplastic incidental brain findings (prevalence 2.0%, 1.1% to 3.1%, excluding white matter hyperintensities, silent infarcts, and microbleeds). The number of asymptomatic people needed to scan to detect any incidental brain finding was 37. The prevalence of incidental brain findings was higher in studies using high resolution MRI sequences than in those using standard resolution sequences (4.3% v 1.7%, P<0.001). The prevalence of neoplastic incidental brain findings increased with age.

CONCLUSIONS

Incidental findings on brain MRI are common, prevalence increases with age, and detection is more likely using high resolution MRI sequences than standard resolution sequences. These findings deserve to be mentioned when obtaining informed consent for brain MRI in research and clinical practice but are not sufficient to justify screening healthy asymptomatic people.

Diffusion and perfusion MR imaging of acute ischemic stroke

Diffusion and perfusion MR imaging have proven to be highly useful in the clinical description and understanding of acute and hyperacute ischemic stroke. In this article, the authors give a brief overview of the basic concepts of diffusion and perfusion imaging and describe some of the current developments, applications, challenges, and limitations of these techniques as applied to cerebral ischemia.

Association between cholesterols, homocysteine and silent brain infarcts

BACKGROUND

The aim of this study was to assess the relationship between total plasma homocysteine, cholesterol levels, vitamin B(12), folate, thyroid hormones, urea, ferritin, uric acid, C-reactive protein, cardiovascular risk factors and silent brain infarct (SBI) in patients without any neurological disorder. Whether the factors of interest were associated with SBI is investigated.

METHODS

One hundred and forty-two subjects with a mean age of 52.1 +/- 13.1 years (21-87 years) without any history of stroke, transient ischaemic attack and neurological abnormality were enrolled in this cross-sectional study. The subjects underwent brain magnetic resonance imaging and blood chemistry determinations. Student's t-test was used to compare differences in means of laboratory results between the groups with and without SBI. The chi(2)-test was used for categorized variables. Multiple logistic regression analysis was used to determine the independent predictors of SBI.

RESULTS

The group comprised 56 men and 86 women. SBI were found in 40 patients (28%). The low-density lipoprotein levels were significantly higher in the infarct group (P = 0.019), homocysteine concentrations were significantly higher in the men-infarct group (P = 0,029) and total cholesterol levels were significantly higher in the women-infarct group than the women non-infarct group (P = 0.006).

CONCLUSION

Serum low-density lipoprotein, total cholesterol and homocysteine levels were associated with SBI.

Beyond mild cognitive impairment: vascular cognitive impairment, no dementia (VCIND)

Identifying the causes of dementia is important in the search for effective preventative and treatment strategies. The concept of mild cognitive impairment (MCI), as prodromal dementia, has been useful but remains controversial since in population-based studies it appears to be a limited predictor of progression to dementia. Recognising the relative contribution of neurodegenerative and vascular causes, as well as their interrelationship, may enhance predictive accuracy. The concept of vascular cognitive impairment (VCI) has been introduced to describe the spectrum of cognitive change related to vascular causes from early cognitive decline to dementia. A recent review of this concept highlighted the need for diagnostic criteria that encompass the full range of the VCI construct. However, very little is known regarding the mildest stage of VCI, generally termed 'vascular cognitive impairment, no dementia' (VCIND). Whether mild cognitive change in the context of neurodegenerative pathologies is distinct from that in the context of cerebrovascular diseases is not known. This is key to the definition of VCIND and whether it is possible to identify this state. Distinguishing between vascular (that is, VCIND) and non-vascular (that is, MCI) cognitive disorders and determining how well each might predict dementia may not be possible due to the overlap in pathologies observed in the older population. Here, we review the concept of VCIND in an effort to identify recent developments and areas of controversy in nosology and the application of VCIND for screening individuals at increased risk of dementia secondary to vascular disease and its risk factors.

Early risk assessment for Alzheimer's disease

The purpose of the Alzheimer's Association Research Roundtable meeting was to discuss the potential of finding diagnostic tools to determine the earliest risk factors for Alzheimer's disease (AD). Currently, drugs approved for AD address symptoms which are generally manifest after the disease is already well-established, but there is a growing pipeline of drugs that may alter the underlying pathology and therefore slow or halt progression of the disease. As these drugs become available, it will become increasingly imperative that those at risk for AD be detected and possibly treated early, especially given recent indications that the disease process may start decades before the first clinical symptoms are recognized. Early detection must go hand-in-hand with qualified tools to determine the efficacy of drugs in people who may be asymptomatic or who have only very mild symptoms of the disease. Devising strategies and screening tools to identify and monitor those at risk in order to perform "prevention" trials is seen by many as a top public-health priority, made all the more urgent by an impending growth in the elderly population worldwide.

Multidetector row CT of the brain and carotid artery: a correlative analysis

AIM

To evaluate the association between types of carotid plaque, the presence of prior ischaemic events detectable with CT, and patient's symptoms.

MATERIALS AND METHODS

Between January 2004 and May 2006, 112 patients were evaluated using multidetector row computed tomography angiography (MDCTA) of the carotid arteries and computed tomography (CT) of the brain. Carotid arteries were categorized by evaluating the degree of stenosis according to North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria, the type of plaque, and the presence of plaque ulceration. The brain was assessed via CT for the presence, type, and position of lesions. Chi-square tests, Student's t test, and simple logistic regression analysis were performed and the Cohen kappa test was applied for interobserver variability measurement.

RESULTS

The Chi-square test indicated a statistically significant association between the presence of fatty plaques (p=0.005) and CT-detectable lesions in the brain (p=0.004). Moreover, the number of patients with CT-detectable brain lesions was greater in patients with >70% stenosis than in those with <70% stenosis (p=0.007). Logistic regression confirmed the association between fatty plaque and symptoms (p=0.001), between >70% stenosis and symptoms (p=0.041), and an inverse association between calcified plaque and symptoms (p=0.009).

CONCLUSION

MDCTA allows adequate evaluation of the type of plaque. The results of the present study indicate that there is an association between cerebral lesions, symptoms, and fatty plaque in the carotid artery. The degree of stenosis also correlated with cerebral lesions and symptoms. According to the obtained data, the type of carotid plaque should be included among primary parameters in the classification of patients' risk class.

Validity of self-reported stroke in elderly African Americans, Caribbean Hispanics, and Whites

BACKGROUND

The validity of a self-reported stroke remains inconclusive.

OBJECTIVE

To validate the diagnosis of self-reported stroke using stroke identified by magnetic resonance imaging (MRI) as the standard.

DESIGN, SETTING, AND PARTICIPANTS

Community-based cohort study of nondemented, ethnically diverse elderly persons in northern Manhattan.

METHODS

High-resolution quantitative MRIs were acquired for 717 participants without dementia. Sensitivity and specificity of stroke by self-report were examined using cross-sectional analyses and the chi(2) test. Putative relationships between factors potentially influencing the reporting of stroke, including memory performance, cognitive function, and vascular risk factors, were assessed using logistic regression models. Subsequently, all analyses were repeated, stratified by age, sex, ethnic group, and level of education.

RESULTS

In analyses of the whole sample, sensitivity of stroke self-report for a diagnosis of stroke on MRI was 32.4%, and specificity was 78.9%. In analyses stratified by median age (80.1 years), the validity between reported stroke and detection of stroke on MRI was significantly better in the younger than the older age group (for all vascular territories: sensitivity and specificity, 36.7% and 81.3% vs 27.6% and 26.2%; P = .02). Impaired memory, cognitive skills, or language ability and the presence of hypertension or myocardial infarction were associated with higher rates of false-negative results.

CONCLUSIONS

Using brain MRI as the standard, specificity and sensitivity of stroke self-report are low. Accuracy of self-report is influenced by age, presence of vascular disease, and cognitive function. In stroke research, sensitive neuroimaging techniques rather than stroke self-report should be used to determine stroke history.

Cerebrovascular disease and patterns of cerebral oxygenation during sleep in elders

PURPOSE

The aim of this descriptive exploratory study was to describe patterns of cerebral oxygen reserves during sleep and their association with cerebrovascular risk factors in elders.

METHOD

Participants--115 elders, age 70+ years--were monitored overnight using standard polysomnography. Measures included arterial oxyhemoglobin (SaO2) and regional measures of percentage of cerebral oxyhemoglobin saturation (rcSO2) via cerebral oximetry. Participants were classified based on the magnitude of change in rcSO2 from resting baseline to the end of the first nonrapid-eye-movement (NREM) period. One-way ANOVA and Chi-square were used to test group differences in SaO2 and the prevalence of cerebrovascular risk factors.

FINDINGS

20 participants (Group 1) experienced an increase in rcSO2 during sleep along with sleeping rcSO2 levels >or= 55%; 95 participants experienced a decline in rcSO2; 72 participants (Group 2) had sleeping rcSO2 levels >or= 55%; and 23 participants had sleeping rcSO2 levels <55% (Group 3). Although all three groups had equivalent declines in SaO2 levels during sleep, Group 3 had more cardiovascular comorbidity than Groups 1 and 2.

CONCLUSIONS

Although SaO2 levels decline in most people during sleep, compensatory vascular responses to these drops in SaO2 are important for preventing rcSO2 from falling during sleep. Those entering sleep with lower baseline rcSO2 levels and those with greater declines in cerebral oxygenation during sleep may have greater cardiovascular burden and be at greater risk for stroke and other forms of disabling cerebrovascular disease.

Analysis of 1008 consecutive patients aged 15 to 49 with first-ever ischemic stroke: the Helsinki young stroke registry

BACKGROUND AND PURPOSE

To analyze trends in occurrence, risk factors, etiology, and neuroimaging features of ischemic stroke in young adults in a large cohort.

METHODS

We evaluated all 1008 consecutive ischemic stroke patients aged 15 to 49 admitted to Helsinki University Central Hospital, 1994 to 2007. Etiology was classified by Trial of Org 10172 in Acute Stroke Treatment criteria. Comparisons were done between groups stratified by gender and age.

RESULTS

Estimated annual occurrence was 10.8/100,000 (range 8.4 to 13.0), increasing exponentially with aging. Of our 628 male and 380 female (ratio 1.7:1) patients, females were preponderant among those <30, whereas male dominance rapidly increased around age of 44. The most frequent risk factors were dyslipidemia (60%), smoking (44%), and hypertension (39%). Males and patients >44 clearly had more risk factors. Cardioembolism (20%) and cervicocerebral artery dissection (15%) were the most frequent etiologic subgroups. Proportions of large-artery atherosclerosis (8%) and small-vessel disease (14%) began to enlarge at age 35, whereas frequency of undetermined etiology (33%) decreased along aging. Posterior circulation infarcts were more common among patients <45 years of age. Left hemisphere infarcts were more frequent in general. There were 235 (23%) patients with multiple and 126 (13%) with silent infarcts, and 55 (5%) patients had leukoaraiosis.

CONCLUSIONS

The frequency of ischemic stroke increases sharply at age 40. Etiology and risk factors start resembling those seen in the elderly in early midlife but causes defined in younger patients still are frequent in those aged 45 to 49. Subclinical infarcts were surprisingly common in the young.

Asymptomatic cerebral microbleeds seen in healthy subjects have a strong association with asymptomatic lacunar infarction

BACKGROUND

Cerebral microbleed (CMB), which is conspicuous on gradient-echo T2-weighted magnetic resonance imaging, is a risk factor of intracerebral hemorrhage (ICH). CMBs have been detected even in neurologically healthy persons, who also seem prone to be affected by stroke, not only ICH but also cerebral infarction.

METHODS AND RESULTS

The presence of CMB was investigated in brain dock participants, making reference to silent lacunar infarction (SLI). Participants comprised 377 neurologically healthy persons and 21 (5.6%) had CMB detected, which was associated with a high incidence of hypertension, other conventional risk factors having no significant correlation with CMB. In a simple correlation analysis, CMB showed a positive association with age and systolic blood pressure (SBP). Logistic regression analysis revealed that SLI was the factor most strongly associated with CMB. Moreover, individuals who had both CMB and SLI had higher SBP than other groups.

CONCLUSIONS

The etiology of CMB is similar to that of SLI.

Symptomatic and Silent Ischemia Associated With Microsurgical Clipping of Intracranial Aneurysms

Background and Purpose— Silent ischemic events are known to occur during diagnostic and interventional endovascular procedures between 10% and 69% of the time. The occurrence of silent and symptomatic ischemic events in the surgically treated population is not known, although atherosclerotic changes of intracranial vessels or within the aneurysms wall or neck area are seen often during surgery.

Methods— Patients with unruptured and ruptured intracranial aneurysms treated by microsurgical clipping were prospectively evaluated with MRI using diffusion-weighted imaging sequences before and within 24 hours after surgery. Patients were evaluated clinically before and after surgery. During surgery, the overall and maximal time of temporary occlusion as well as the total number of temporary and finally applied clips was noted. Diffusion-weighted images were analyzed with determination and characterization of diffusion-weighted imaging abnormalities.

Results— Thirty-six patients with 51 aneurysms were included. One symptomatic and 5 silent ischemic lesions were found in 5 patients. This represents a risk of silent ischemia of 9.8% per treated aneurysm and a risk of symptomatic stroke of 2%. The most significant risk factor in increasing order was: age ( P <0.05), presence of thrombus ( P <0.05), number of final clips applied ( P <0.05), number of temporary clips used ( P <0.01), total time of temporary clip occlusion ( P <0.001), and maximal time of temporary occlusion ( P <0.001).

Conclusions— The risk of silent and symptomatic ischemic events during microsurgical clipping of intracranial aneurysms seems to be low. Microsurgical clipping is safe and should continue to be strongly considered as a treatment option.

Neuroimaging in dementia

Although dementia is a clinical diagnosis, neuroimaging often is crucial for proper assessment. Magnetic resonance imaging (MRI) and computed tomography (CT) may identify nondegenerative and potentially treatable causes of dementia. Recent neuroimaging advances, such as the Pittsburgh Compound-B (PIB) ligand for positron emission tomography imaging in Alzheimer's disease, will improve our ability to differentiate among the neurodegenerative dementias. High-resolution volumetric MRI has increased the capacity to identify the various forms of the frontotemporal lobar degeneration spectrum and some forms of parkinsonism or cerebellar neurodegenerative disorders, such as corticobasal degeneration, progressive supranuclear palsy, multiple system atrophy, and spinocerebellar ataxias. In many cases, the specific pattern of cortical and subcortical abnormalities on MRI has diagnostic utility. Finally, among the new MRI methods, diffusion-weighted MRI can help in the early diagnosis of Creutzfeldt-Jakob disease. Although only clinical assessment can lead to a diagnosis of dementia, neuroimaging is clearly an invaluable tool for the clinician in the differential diagnosis.