Age-related reductions in cerebral vasomotor reactivity and the law of initial value: a 4-year prospective longitudinal study

The benefits of regular aerobic exercise training on cerebrovascular function and cognition in older adults

We compared the differences in cerebrovascular and cognitive function between 13 aerobic exercise trained, older adults and 13 age-, height- and sex-matched sedentary, untrained controls. We determined whether other measures accounted for differences in cerebrovascular and cognitive function between these groups and examined the associations between these functions. Participants undertook anthropometric, mood, cardiovascular, exercise performance, strength, cerebrovascular, and cognitive measurements, and a blood collection. Transcranial Doppler ultrasonography determined cerebrovascular responsiveness (CVR) to hypercapnia and cognitive stimuli. The trained group had a higher CVR to hypercapnia (80.3 ± 7.2 vs 35.1 ± 6.7%, P < 0.001), CVR to cognitive stimuli (30.1 ± 2.9 vs 17.8 ± 1.4%, P = 0.001) and total composite cognitive score (117 ± 2 vs 98 ± 4, P < 0.001) than the controls. These parameters no longer remained statistically different between the groups following adjustments for covariates. There were positive correlations between the total composite cognitive score and CVR to hypercapnia (r = 0.474, P = 0.014) and CVR to cognitive stimuli (r = 0.685, P < 0.001). We observed a relationship between cerebrovascular and cognitive function in older adults and an interaction between regular lifelong aerobic exercise training and cardiometabolic factors that may directly influence these functions.

Age-related normative changes in cerebral perfusion: Data from The Irish Longitudinal Study on Ageing (TILDA)

OBJECTIVE

To establish normative reference values for total grey matter cerebral blood flow (CBF_GM) measured using pseudo-continuous arterial spin labelling (pCASL) MRI in a large cohort of community-dwelling adults aged 54 years and older.

BACKGROUND

Quantitative assessment of CBF_GM may provide an imaging biomarker for the early detection of those at risk of neurodegenerative diseases, such as Alzheimer's and dementia. However, the use of this method to differentiate normal age-related decline in CBF_GM from pathological reduction has been hampered by the lack of reference values for cerebral perfusion.

METHODS

The study cohort comprised a subset of wave 3 (2014-2015) participants from The Irish Longitudinal Study on Ageing (TILDA), a large-scale prospective cohort study of individuals aged 50 and over. Of 4309 participants attending for health centre assessment, 578 individuals returned for 3T multi-parametric MRI brain examinations. In total, CBF_GM data acquired from 468 subjects using pCASL-MRI were included in this analysis. Normative values were estimated using Generalised Additive Models for Location Shape and Scale (GAMLSS) and are presented as percentiles, means and standard deviations.

RESULTS

The mean age of the cohort was 68.2 ± 6.9 years and 51.7% were female. Mean CBF_GM for the cohort was 36.5 ± 8.2 ml/100 g/min. CBF_GM decreased by 0.2 ml/100 g/min for each year increase in age (95% CI = -0.3, -0.1; p ≤ 0.001) and was 3.1 ml/100 g/min higher in females (95% CI = 1.6, 4.5; p ≤ 0.001).

CONCLUSIONS

This study is by far the largest single-site study focused on an elderly community-dwelling cohort to present normative reference values for CBF_GM measured at 3T using pCASL-MRI. Significant age- and sex-related differences exist in CBF_GM.

Clinical characteristics and leptomeningeal collateral status in pediatric and adult patients with ischemic moyamoya disease

AIM

Previous studies have found significant differences in clinical characteristics between pediatric and adult moyamoya disease (MMD) patients, but few studies have focused on the factors underlying these differences. We aimed to investigate the differences in leptomeningeal collateral (LMC) status between pediatric and adult MMD patients and to analyze the effects of LMCs on clinical characteristics and therapeutic prognosis.

METHODS

We retrospectively analyzed 214 MMD patients from January 2014 to January 2016. Clinical characteristics and LMC status were compared between the pediatric and adult patients. LMC status was graded as good or poor depending on the retrograde flow from the posterior cerebral artery (PCA) on digital subtraction angiography (DSA).

RESULTS

A total of 83 pediatric and 131 adult (1:1.6) MMD patients were analyzed. Pediatric patients were more likely to experience a transient ischemic attack (81%), whereas adult patients were more likely to experience infarction (51%). Regarding the different MMD stages (the early, medium, and advanced stages corresponded to Suzuki stages 1-2, 3-4, and 5-6, respectively), the prevalence of good LMC status was higher for pediatric patients than for adult patients in the early stage (P = 0.047) and the medium stage (P = 0.001), but there were no differences between these patient groups in the advanced stage (P = 0.547). Worse postoperative angiographic outcomes (P = 0.017) were found in adult patients than in pediatric patients in the medium stage. Poor LMC status had strong correlations with infarction (P < 0.001 and P = 0.017) and poor postoperative outcomes (P = 0.003 and P = 0.043) in both pediatric and adult patients.

CONCLUSIONS

Pediatric MMD patients have greater patency and a greater ability to establish good LMC status than adult patients, and poor LMC status has a strong correlation with severe clinical symptoms and poor postoperative outcomes. LMC status may be an important factor in the differences in clinical characteristics and prognosis between pediatric and adult MMD patients.

Reducing Hypertriglyceridemia in Elderly Patients with Cerebrovascular Disease Stabilizes or Improves Cognition and Cerebral Perfusion

Effects of lowering serum triglyceride levels were investigated among 44 el derly hypertriglyceridemic patients with risk factors for stroke, reduced cere bral perfusion, and a history compatible with symptomatic occlusive cerebro vascular disease. Patients were randomly assigned to either treatment with gem fibrozil, a lipid-lowering agent, or control conditions. Subjects in both groups were instructed to follow a diet recommended for lowering serum lipid levels, while the treatment group was additionally administered 600 mg daily of gemfi brozil. Subjects assigned to the treatment group (n = 22) showed significant re ductions in serum triglyceride levels (p < .0005). Control subjects (n=22) did not show any significant changes in serum triglyceride levels. There were also no significant changes in total cholesterol levels in either group. Analyses of values for mean bihemispheric gray matter cerebral blood flow measured by the xenon 133 inhalation method and cognitive scores tested by the Cognitive Ca pacity Screening Examination indicated that gemfibrozil-treated patients main tained significantly higher levels of cerebral perfusion and cognitive perform ance than untreated controls did. Regression analyses for different treatment intervals indicated that both cerebral blood flow and cognition showed linear improvements that correlated directly with the duration of treatment. Lowering triglyceride levels in hyperlipidemic subjects appears to benefit cerebral perfu sion and cognitive performance after four to six months.

Cerebrovascular Reactivity and Central Arterial Stiffness in Habitually Exercising Healthy Adults

Reduced cerebrovascular reactivity to a vasoactive stimulus is associated with age-related diseases such as stroke and cognitive decline. Habitual exercise is protective against cognitive decline and is associated with reduced stiffness of the large central arteries that perfuse the brain. In this context, we evaluated the age-related differences in cerebrovascular reactivity in healthy adults who habitually exercise. In addition, we sought to determine the association between central arterial stiffness and cerebrovascular reactivity. We recruited 22 young (YA: age = 27 ± 5 years, range 18–35 years) and 21 older (OA: age = 60 ± 4 years, range 56–68 years) habitual exercisers who partake in at least 150 min of structured aerobic exercise each week. Middle cerebral artery velocity (MCAv) was recorded using transcranial Doppler ultrasound. In order to assess cerebrovascular reactivity, MCAv, end-tidal carbon dioxide (ETCO₂), and mean arterial pressure (MAP) were continuously recorded at rest and during stepwise elevations of 2, 4, and 6% inhaled CO₂. Cerebrovascular conductance index (CVCi) was calculated as MCAv/MAP. Central arterial stiffness was assessed using carotid–femoral pulse wave velocity (PWV). Older adults had higher PWV (YA: 6.2 ± 1.2 m/s; OA: 7.5 ± 1.3 m/s; p < 0.05) compared with young adults. MCAv and CVCi reactivity to hypercapnia were not different between young and older adults (MCAv reactivity, YA: 2.0 ± 0.2 cm/s/mmHg; OA: 2.0 ± 0.2 cm/s/mmHg; p = 0.77, CVCi reactivity, YA: 0.018 ± 0.002 cm/s/mmHg²; OA: 0.015 ± 0.001 cm/s/mmHg²; p = 0.27); however, older adults demonstrated higher MAP reactivity to hypercapnia (YA: 0.4 ± 0.1 mmHg/mmHg; OA: 0.7 ± 0.1 mmHg/mmHg; p < 0.05). There were no associations between PWV and cerebrovascular reactivity (range: r = 0.00–0.39; p = 0.07–0.99). Our results demonstrate that cerebrovascular reactivity was not different between young and older adults who habitually exercise; however, MAP reactivity was augmented in older adults. This suggests an age-associated difference in the reliance on MAP to increase cerebral blood flow during hypercapnia.

Comparison of Physiological and Psychological Relaxation Using Measurements of Heart Rate Variability, Prefrontal Cortex Activity, and Subjective Indexes after Completing Tasks with and without Foliage Plants

The objective of this study was to compare physiological and psychological relaxation by assessing heart rate variability (HRV), prefrontal cortex activity, and subjective indexes while subjects performed a task with and without foliage plants. In a crossover experimental design, 24 university students performed a task transferring pots with and without a foliage plant for 3 min. HRV and oxyhemoglobin (oxy-Hb) concentration in the prefrontal cortex were continuously measured. Immediately thereafter, subjective evaluation of emotions was performed using a modified semantic differential (SD) method and a profile of mood state questionnaire (POMS). Results showed that the natural logarithmic (ln) ratio of low frequency/high frequency, as an estimate of sympathetic nerve activity, was significantly lower while performing the task with foliage plants for the average 3 min measurement interval. Oxy-Hb concentration in the left prefrontal cortex showed a tendency to decrease in the 2–3 min interval in the task with foliage plants compared to the task without plants. Moreover, significant psychological relaxation according to POMS score and SD was demonstrated when the task involved foliage plants. In conclusion, the task involving foliage plants led to more physiological and psychological relaxation compared with the task without foliage plants.

The Effect of Chunghyul-Dan on Hyperventilation-Induced Carbon Dioxide Reactivity of the Middle Cerebral Artery in Normal Subjects: A Dose-Dependent Study

Background. This study was conducted to show the prompt effect of chunghyul-dan (CHD) on cerebral hemodynamics in order to provide evidence for its use in stroke prevention. Methods. Hyperventilation-induced CO₂ reactivity of the middle cerebral artery was measured in 12 healthy male volunteers (mean age: 26.3 ± 1.1 years) using transcranial Doppler sonography. All subjects were examined before and for 3 hours after administration, with an interval of 1 week between measurements. Results. Compared to baseline, the CO₂ reactivity of the middle cerebral artery increased significantly at 2 and 3 hours after the administration of CHD (600 mg and 1200 mg). The mean blood pressure and heart rate did not vary from the baseline values in all groups. Conclusion. These data suggest that CHD administration (especially 600 mg) immediately improves cerebral blood flow.

Physiological Effects of Nature Therapy: A Review of the Research in Japan

Humans have evolved into what they are today after the passage of 6-7 million years. If we define the beginning of urbanization as the rise of the industrial revolution, less than 0.01% of our species' history has been spent in modern surroundings. Humans have spent over 99.99% of their time living in the natural environment. The gap between the natural setting, for which our physiological functions are adapted, and the highly urbanized and artificial setting that we inhabit is a contributing cause of the "stress state" in modern people. In recent years, scientific evidence supporting the physiological effects of relaxation caused by natural stimuli has accumulated. This review aimed to objectively demonstrate the physiological effects of nature therapy. We have reviewed research in Japan related to the following: (1) the physiological effects of nature therapy, including those of forests, urban green space, plants, and wooden material and (2) the analyses of individual differences that arise therein. The search was conducted in the PubMed database using various keywords. We applied our inclusion/exclusion criteria and reviewed 52 articles. Scientific data assessing physiological indicators, such as brain activity, autonomic nervous activity, endocrine activity, and immune activity, are accumulating from field and laboratory experiments. We believe that nature therapy will play an increasingly important role in preventive medicine in the future.

Elucidation of a physiological adjustment effect in a forest environment: a pilot study

There is a significant positive relationship between exposure to forest environments and physical and mental health. However, there are individual differences within these responses, and this phenomenon has posed questions in various fields. Here, we show that the physiological effect of a forest environment can differ depending on a subject’s initial values and that forests have a physiological adjustment effect close to an appropriate level. Subjects with high initial blood pressure and pulse rate showed a decrease in these values after walking in a forested area, whereas those with low initial values showed an increase. There was no physiological adjustment effect observed in an urban area; thus, these effects are specific to a forest environment.

Effect of ST36 Acupuncture on Hyperventilation-Induced CO 2 Reactivity of the Basilar and Middle Cerebral Arteries and Heart Rate Variability in Normal Subjects

This study was conducted to verify the effect of acupuncture on cerebral haemodynamics to provide evidence for the use of acupuncture treatment as a complementary therapy for the high-risk stroke population. The effect of ST36 acupuncture treatment on the hyperventilation-induced CO2 reactivity of the basilar and middle cerebral arteries was studied in 10 healthy male volunteers (mean age, 25.2 ± 1.5 years) using a transcranial Doppler sonography with an interval of 1 week between measurements, and a portable ECG monitoring system was used to obtain ECG data simultaneously. The CO2 reactivity of the basilar and middle cerebral arteries increased significantly after ST36 acupuncture treatment, whereas the mean arterial blood pressure and pulse rate did not change significantly. The high-frequency power significantly increased after ST36 acupuncture treatment, and the percentage increase of high-frequency power correlated significantly with the percentage increase in the CO2 reactivity of the contralateral middle cerebral artery. These data suggest that ST36 acupuncture treatment increases CO2 reactivity, indicating improvement of vasodilatory potential of the cerebral vasculature to compensate for fluctuations caused by changes in external conditions. The increase in parasympathetic tone by ST36 acupuncture treatment is responsible for this therapeutic effect.

[Elucidation of the physiological adjustment effect of forest therapy]

OBJECTIVES

The aim of this study was to elucidate the physiological adjustment effect of forest therapy based on the Law of Initial Value.

METHODS

The experiments were conducted in nine forest and urban areas in Japan during the period from 2011 to 2012. There were 12 male Japanese university students participating in each of the nine experiments (total, 108 participants). Of these, 98 subjects (mean age ± standard deviation, 21.4 ± 1.6 years) were analyzed. The subjects were instructed to view a real forest landscape or urban area for 15 min. The systolic blood pressure, diastolic blood pressure, and pulse rate of each subject were measured. We analyzed the correlation between the initial values (after city viewing) and the differences in values between the two environments (after forest viewing-after city viewing).

RESULTS

There was a negative correlation between the initial values and the differences in values between the two environments. The subjects whose initial systolic blood pressure, diastolic blood pressure, and pulse rate were high showed marked decreases in these parameters as their response after viewing the forest environment, whereas those whose initial systolic blood pressure, diastolic blood pressure, and pulse rate were low showed increases in these parameters as their response.

CONCLUSIONS

These results support the premise that the physiological effect of a forest environment can differ depending on a subject's initial response values. Moreover, it was clear that forest therapy caused physiological adjustment, normalizing blood pressure and pulse rate.

Biomarkers and perfusion--training-induced changes after stroke (BAPTISe): protocol of an observational study accompanying a randomized controlled trial

Background

Physical activity is believed to exert a beneficial effect on functional and cognitive rehabilitation of patients with stroke. Although studies have addressed the impact of physical exercise in cerebrovascular prevention and rehabilitation, the underlying mechanisms leading to improvement are poorly understood. Training-induced increase of cerebral perfusion is a possible mediating mechanism. Our exploratory study aims to investigate training-induced changes in blood biomarker levels and magnetic resonance imaging in patients with subacute ischemic stroke.

Methods/design

This biomarker-driven study uses an observational design to examine a subgroup of patients in the randomized, controlled PHYS-STROKE trial. In PHYS-STROKE, 215 patients with subacute stroke (hemorrhagic and ischemic) receive either 4 weeks of physical training (aerobic training, 5 times a week, for 50 minutes) or 4 weeks of relaxation sessions (5 times a week, for 50 minutes). A convenience sample of 100 of these patients with ischemic stroke will be included in BAPTISe and will receive magnetic resonance imaging (MRI) scans and an additional blood draw before and after the PHYS-STROKE intervention. Imaging scans will address parameters of cerebral perfusion, vessel size imaging, and microvessel density (the Q factor) to estimate the degree of neovascularization in the brain. Blood tests will determine several parameters of immunity, inflammation, endothelial function, and lipometabolism. Primary objective of this study is to evaluate differential changes in MRI and blood-derived biomarkers between groups. Other endpoints are next cerebrovascular events and functional status of the patient after the intervention and after 3 months assessed by functional scores, in particular walking speed and Barthel index (co-primary endpoints of PHYS-STROKE). Additionally, we will assess the association between functional outcomes and biomarkers including imaging results. For all endpoints we will compare changes between patients who received physical fitness training and patients who had relaxation sessions.

Discussion

This exploratory study will be the first to investigate the effects of physical fitness training in patients with ischemic stroke on MRI-based cerebral perfusion, pertinent blood biomarker levels, and functional outcome. The study may have an impact on current patient rehabilitation strategies and reveal important information about the roles of MRI and blood-derived biomarkers in ischemic stroke.

Trial registration

NCT01954797.

Functional imaging of cerebral perfusion

The functional imaging of perfusion enables the study of its properties such as the vasoreactivity to circulating gases, the autoregulation and the neurovascular coupling. Downstream from arterial stenosis, this imaging can estimate the vascular reserve and the risk of ischemia in order to adapt the therapeutic strategy. This method reveals the hemodynamic disorders in patients suffering from Alzheimer's disease or with arteriovenous malformations revealed by epilepsy. Functional MRI of the vasoreactivity also helps to better interpret the functional MRI activation in practice and in clinical research.

The detrimental effect of aging on leptomeningeal collaterals in ischemic stroke

BACKGROUND

Aging is associated with decreased penumbral salvage in patients with ischemic stroke. Another critical factor that determines the fate of penumbra tissue is the degree of collateral circulation, which decreases significantly with aging in experimental models of stroke. In this study, we sought to identify whether these observations could be translated to humans and, therefore, analyzed the effect of patient age on extent of leptomeningeal collaterals in patients with ischemic stroke.

METHODS

Computed tomography angiography (CTA) source images were used to assess the degree of collateral circulation in a retrospective series of patients with proximal middle cerebral artery (MCA) occlusion. Bivariate and multivariate analyses were used to explore the relationship between patient age and degree of collateral circulation.

RESULTS

A total of 70 patients were included into the study. Older age (P = .005), history of hypertension (P = .036), higher admission National Institutes of Health Stroke Scale (NIHSS) scores (P = .013), and increased time to CTA (P = .013) were associated with inadequate collaterals in bivariate analyses. In multivariate analysis, older age (P = .008) and higher NIHSS scores (P = .032) remained as the only significant independent variables that were associated with inadequate collaterals. A 10-year increment in patient age increased the odds of inadequate collateral circulation by 1.87 (95% confidence interval: 1.18-2.97).

CONCLUSION

Our findings show that there is a significant interplay between patient age and adequacy of leptomeningeal collateral circulation in patients with proximal MCA occlusion. The relationship could contribute to adverse tissue outcome and thereby to unfavorable clinical outcome observed in elderly patients with ischemic stroke.

Cyclooxygenase inhibition abolishes age-related differences in cerebral vasodilator responses to hypercapnia

Blood flow and vasodilatory responses are altered by age in a number of vascular beds, including the cerebral circulation. To test the role of prostaglandins as regulators of cerebral vascular function, we examined cerebral vasodilator responses to CO(2) (cerebrovascular reactivity) in young (26 ± 5 yr; 6 males/6 females) and older (65 ± 6 yr, 5 males/5 females) healthy humans before and after cyclooxygenase inhibition (using indomethacin). Middle cerebral artery velocity (MCAv) responses to stepped hypercapnia were measured before and 90 min after indomethacin. Changes in MCAv during the recovery from hypercapnia (vasoconstrictor responses) were also evaluated before and after indomethacin. Cerebrovascular reactivity was calculated using linear regression between MCAv and end-tidal CO(2). Young adults demonstrated greater MCAv (55 ± 6 vs. 39 ± 5 cm/s: P < 0.05) and MCAv reactivity (1.67 ± 0.20 vs. 1.09 ± 0.19 cm·s(-1)·mmHg(-1); P < 0.05) to hypercapnia compared with older adults (P < 0.05). In both groups MCAv and MCAv reactivity decreased between control and indomethacin. Furthermore, the age-related differences in these cerebrovascular variables were abolished by indomethacin. During the recovery from hypercapnia, there were no age-related differences in MCAv reactivity; however, indomethacin significantly reduced the MCAv reactivity in both groups. Taken together, these results suggest that cerebral blood flow velocity and cerebrovascular reactivity are attenuated in aging humans, and may be due to a loss of prostaglandin-mediated vasodilation.

Improved Cerebral Vasomotor Reactivity After Exercise Training in Hemiparetic Stroke Survivors

Background and Purpose—

Animal studies provide strong evidence that aerobic exercise training positively influences cerebral blood flow, but no human studies support the use of exercise for improving cerebral hemodynamics. This randomized study in stroke survivors assessed the effects of treadmill aerobic exercise training (TM) on cerebral blood flow parameters compared to a control intervention of nonaerobic stretching.

Methods—

Thirty-eight participants (19 in TM group and 19 in control group) with remote stroke (>6 months) and mild to moderate gait deficits completed middle cerebral artery blood flow velocity measurements by transcranial Doppler ultrasonography before and after a 6-month intervention period. Middle cerebral artery blood flow velocity was assessed bilaterally during normocapnia and hypercapnia (6% CO 2 ). Cerebral vasomotor reactivity (cVMR) was calculated as percent change in middle cerebral artery blood flow velocity from normocapnia to hypercapnia (cVMR percent) and as an index correcting percent change for absolute increase in end tidal CO 2 (cVMR index).

Results—

The TM group had significantly larger improvements than did controls for both ipsilesional and contralesional cVMR index ( P ≤0.05) and contralesional cVMR percent ( P ≤0.01). Statin users in the TM group (n=10) had higher baseline cVMR and lower training-induced cVMR change, indicating that cVMR change among those not using statins (n=9) primarily accounted for the between-group effects. There was a 19% increase in V o 2 peak for the TM group compared to a 4% decrease in the control group ( P <0.01), and peak fitness change correlated with cVMR change ( r =0.55; P <0.05).

Conclusions—

Our data provide the first evidence to our knowledge of exercise-induced cVMR improvements in stroke survivors, implying a protective mechanism against recurrent stroke and other brain-related disorders. Statin use appears to regulate cVMR and the cVMR training response.

Aura attacks from acute convexity subarachnoid haemorrhage not due to cerebral amyloid angiopathy

Background and purpose: Convexity subarachnoid haemorrhage (cSAH) has recently been recognised as a cause of recurrent aura-like symptoms, mimicking transient ischaemic attacks (TIAs). Subarachnoid haemorrhage and recurrent aura-like episodes can occur in patients with cerebral amyloid angiopathy (CAA), which has been the presumed cause in the majority of reported cases. However, this syndrome can occur following cSAH secondary to other conditions, and it is important for clinicians to investigate and manage such patients appropriately.

Method: Case series.

Results: We describe two patients who presented with recurrent stereotyped transient neurological symptoms in the setting of acute cSAH identified on MRI. In one patient, SAH occurred secondary to cerebral venous sinus thrombosis. In the other, SAH was due to extension of a traumatic subdural haematoma.

Conclusions: Conditions other than CAA can cause the clinicoradiological syndrome of cSAH with recurrent TIA-like events. Gradient echo or susceptibility-weighted imaging should be included in the diagnostic work-up of patients presenting with such events. When cSAH is detected, the full differential diagnosis for this should be considered. Aetiologies other than CAA can cause this syndrome and management can vary greatly depending on the underlying cause.

Effects of aging on the cerebrovascular orthostatic response

When healthy subjects stand up, it is associated with a reduction in cerebral blood velocity and oxygenation although cerebral autoregulation would be considered to prevent a decrease in cerebral perfusion. Aging is associated with a higher incidence of falls, and in the elderly falls may occur particularly during the adaptation to postural change. This study evaluated the cerebrovascular adaptation to postural change in 15 healthy younger (YNG) vs. 15 older (OLD) subjects by recordings of the near-infrared spectroscopy-determined cerebral oxygenation (cO₂Hb) and the transcranial Doppler-determined mean middle cerebral artery blood velocity (MCA V(mean)). In OLD (59 (52-65) years) vs. YNG (29 (27-33) years), the initial postural decline in mean arterial pressure (-52 ± 3% vs. -67 ± 3%), cO₂Hb (-3.4 ± 2.5 μmoll(-1) vs. -5.3 ± 1.7 μmoll(-1)) and MCA V(mean) (-16 ± 4% vs. -29 ± 3%) was smaller. The decline in MCA V(mean) was related to the reduction in MAP. During prolonged orthostatic stress, the decline in MCA V(mean)and cO(2)Hb in OLD remained smaller. We conclude that with healthy aging the postural reduction in cerebral perfusion becomes less prominent.

Neurocognitive function and cerebral emboli: randomized study of on-pump versus off-pump coronary artery bypass surgery

BACKGROUND

Neurocognitive impairment can be a debilitating complication after coronary artery bypass graft surgery (CABG). Cardiopulmonary bypass, in particular, cerebral emboli, has been implicated. We compared neurocognitive function and cerebral emboli in patients undergoing on-pump and off-pump CABG.

METHODS

212 patients admitted for CABG were randomly assigned to on-pump (n = 104) or off-pump (n = 108) surgery. Embolic signals were detected with bilateral transcranial Doppler ultrasonography of the middle cerebral artery. Neurocognitive tests were administered preoperatively, on discharge from hospital, at 6 weeks, and at 6 months after surgery. Composite neurocognitive scores were derived using principal component analysis and were compared between the two groups, using analysis of covariance to adjust for baseline values.

RESULTS

At discharge from hospital, the adjusted composite neurocognitive score was 0.25 standard deviations greater in the off-pump group compared with the on-pump group (95% confidence interval: 0.05 to 0.45; p = 0.01). There was no significant difference at 6 weeks (0.09 standard deviations, 95% confidence interval: -0.11 to +0.30; p = 0.4) and 6 months (-0.002 standard deviations, 95% confidence interval: -0.23 to +0.23; p = 1.0). Median number of embolic signals was 1,605 (751 to 2,473) during on-pump and 9 (4 to 27) in off-pump CABG (p < 0.001). Age, length of education, and on-pump status were independent predictors of the predischarge neurocognitive score (p = 0.02, 0.03, and 0.006, respectively).

CONCLUSIONS

Cerebral emboli are more prevalent during on-pump CABG. At discharge from hospital, neurocognitive function is better after off-pump surgery, possibly as a result of the lower embolic load. However, the difference in neurocognitive function does not persist at 6 weeks and 6 months.

Mortality and blood pressure in elderly people with and without cognitive impairment

BACKGROUND

Controversial data are available on the association between mortality, blood pressure and cognitive impairment in the elderly.

OBJECTIVE

To verify the role of blood pressure on mortality in an elderly population with and without cognitive impairment.

METHODS

A cross-sectional survey with a 6-year mortality evaluation was conducted in a region of southern Italy in elderly subjects with and without cognitive impairment. Subjects were divided into 4 groups on the basis of systolic, diastolic, mean and pulse blood pressure values.

RESULTS

Mortality shows a linear relationship with pulse blood pressure and a U-curve shape for diastolic blood pressure. This phenomenon was more evident in subjects with cognitive impairment showing the greatest risk of mortality at the lowest and highest levels of diastolic blood pressure.

CONCLUSION

The study shows that mortality increases linearly with increasing blood pressure in the elderly. In contrast, mortality shows a U-shape curve for diastolic blood pressure; cognitively impaired patients with the lowest and highest diastolic blood pressures show the greatest relative risk of mortality.

Vasoreactivity in patients with periventricular white matter lucency

OBJECTIVES

Cerebral hypoperfusion has been evidenced in patients with periventricular white matter lucency (PWML), however, our knowledge is limited regarding vasoreactivity (VR) changes in these patients. Therefore, we compared the cerebral blood flow velocity (CBFV) responses during different vasoregulatory challenges in healthy volunteers, to those in patients with PWML.

MATERIAL AND METHODS

In 20 patients with PWML and in 20 healthy volunteers the VR of the middle cerebral artery (MCA) system was measured by analyzing the changes of CBFV during different stimulation paradigms (ventilation, tilting and acetazolamide tests). During transcranial Doppler (TCD) registration the systemic blood pressure, the expiratory partial CO(2) pressure (pCO(2)) and the electroencephalograph (EEG) were monitored.

RESULTS

The relative velocity change was significantly smaller in the PWML group than in the normal control group during hypercapnia (16 +/- 12% vs 32 +/- 17%; P < 0.001) and this finding was confirmed by assessment of pCO(2)-corrected velocity change (4.7 +/- 3.7 cm/s/kPa vs 18.4 +/- 6.8 cm/s/KPa; P < 0.001). Although CBFV measurements during acetazolamide test tended to support these findings, the changes of other parameters measured did not reach the level of significance. One patient showed considerable orthostatic reaction (mean arterial blood pressure decrease by 70 mmHg) but it was not associated with significant changes in CBFV.

CONCLUSION

Patients with PWML showed an impaired VR in the MCA flow territory supporting the concept of the microangiopathic origin of leukoaraiotic changes.

Gender-related effects of indomethacin on cerebrovascular CO2 reactivity

Prostaglandins are believed to play an important role in the regulation of resting cerebral blood flow and in the vasodilatory response to hypercapnia. Recently, we reported an increased CO2 reactivity (CR) in premenopausal women and, in the past, evidence has accumulated that estrogens might increase basal levels of prostaglandin secretion from endothelial cells. Therefore, one may speculate that gender differences in CR are possibly mediated by higher prostaglandin levels in women. Using transcranial Doppler sonography, we assessed CR before and 90 min after a single dose of 100 mg of indomethacin in 22 healthy volunteers (11 men, 11 women). Before intake of indomethacin, women had a significantly higher CR (4.53+/-0.49 vs. 3.61+/-0.74, P<0.01). Ninety minutes after indomethacin administration, CR decreased to 1.53+/-0.93 in women and 1.60+/-0.92 in men, respectively. The change of CR was 3.00+/-1.29 in women vs. 2.01+/-1.06 in men (P=0.07). For the entire study population, the decrease of CR was linearly correlated with the initial value of CR (rs=0.74, P<0.001). This gender-related difference possibly relates to higher prostaglandin levels as mediators of an increased CR in premenopausal women, although the exact features remain to be clarified.

Cerebrovascular assessment of the high-risk patient: the role of transcranial Doppler ultrasound

With increased attention to the causes and effects of neurologic injury related to cardiopulmonary bypass anesthesia and surgery, multiple modality examination and monitoring of cerebral function and perfusion in the perioperative period may prove to be advantageous. Transcranial Doppler examination and monitoring is inexpensive, noninvasive, safe, provides unique information about the functional status of the intracranial circulation, and complements the duplex Doppler study of the extracranial carotid vessels of the neck for preoperative evaluation of the surgical patient. The transcranial Doppler examination permits quantitation of blood flow velocity of the intracranial vessels, evaluation of autoregulatory capacity and vasomotor reserve, determination of symmetry of flow velocity in the circle of Willis, assessment of collateral circulatory capacity, examination of vessels not accessible to the duplex Doppler and serves as a baseline for intraoperative monitoring and the postoperative examination. Noninvasive, unilateral or bilateral, continuous monitoring of brain blood flow velocity intraoperatively or postoperatively with trending, storage, and correlation with other physiologic variables provides evidence of cerebral perfusion, occurrence and rate of cerebral embolism, and continuous monitoring of therapeutic interventions. A review of the incidence of stroke and neuropsychologic deficit after bypass surgery is focused on parameters amenable to diagnosis using transcranial Doppler. Patient-specific risk factors for neurologic injury derived from previous studies are discussed as well as risk factors that are related to anesthetic and surgical management and equipment. A description of Doppler technology and the correlation of transcranial Doppler findings with angiography and radionucleotide scans establishes the accuracy of the Doppler examination. The preoperative examination, provocative tests of vasomotor reserve, the evaluation of cerebral collateral circulation, and examples of Doppler applications are discussed.

Photic stimulation study of changing the arterial partial pressure level of carbon dioxide

To investigate the effect of the level of baseline cerebral blood flow (CBF) on local CBF augmentation by activation, we have used positron emission tomography to measure regional CBF (rCBF) in 12 normal volunteers with and without photic stimulation during hypocapnia, normocapnia, and hypercapnia. The increase in rCBF in the primary visual cortex by photic stimulation was 10.8 +/- 3.1, 18.6 +/- 9.3, and 19.5 +/- 6.1 ml 100 ml-1 min-1 in hypo-, normo-, and hypercapnia, respectively. The increase was significantly smaller in hypocapnia than in normocapnia (p < 0.005). The fractional CBF increase caused by the photic stimulation was the same in all breathing conditions. This result indicates that the magnitude of the CBF increase induced by neuronal activity correlates proportionally with the level of baseline CBF.

Vibration-induced regional cerebral blood flow responses in normal aging

Task-induced changes in regional CBF (rCBF) can be measured with positron emission tomography (PET) and provide a powerful tool to map brain function. Many studies using these techniques have investigated responses in healthy young subjects. Since many pathological conditions occur more commonly in older subjects, it is necessary to compare blood flow responses in these patients with appropriately age-matched controls. Furthermore, the effects of normal aging on such blood flow responses remain unknown. For both reasons, we designed this study to determine whether vibration-induced CBF responses change with advancing age in normals. CBF was measured with PET and bolus-administered H2(15)O in 26 subjects from 20 to 72 years old (mean = 39; SD = 19). Regional responses were identified by subtraction-image analysis. Left and right hand vibration produced consistent responses in contralateral primary sensorimotor area (PSA) and supplementary motor area (SMA). Response magnitudes were compared to age by linear regression. There were no substantial relationships between age and responses to vibration for PSA or SMA (PSA r = -0.28, p = 0.054; SMA r = -0.33, p = 0.13). Power analysis demonstrates a high degree of confidence (99.7% for PSA and 87% for SMA) for detecting at least a moderate correlation (r = 0.6) between response magnitude and age. We conclude that the rCBF responses to vibrotactile hand stimulation do not change with normal aging.

Distribution of red blood cell velocity in capillary network, and endothelial ultrastructure, in aged rat skeletal muscle

Although age-related structural and functional changes in skeletal muscle have been described extensively, little is known about the accompanying hemodynamic and structural changes in the microvasculature. The objective of this study was to use the extensor digitorum longus muscle in mid-aged (12 months) and old (28 months) Fisher 344 male rats to evaluate (1) the distribution of microvascular flow in the resting state, (2) the distribution response to a complete 30-min tourniquet ischemia, and (3) the extent of damage of capillary endothelium. Using intravital video microscopy, the mean resting velocity of red cells in capillaries was found to be 3x larger in old rats while the distribution of velocity within the microvascular bed was as heterogeneous as that in mid-aged rats. The postischemic response was characterized by the same mean peak velocity, but a slower return to velocity to the preischemic level. Within the microvascular bed, there was a less uniform postischemic response among capillaries. No long-term effect of ischemia was seen as velocity was already stable at the preischemic level 20 min after the tourniquet release. There were no differences in the pre- and postischemic densities of perfused capillaries, wet/dry weight ratios, or the occurrence of damaged capillaries. Thus, in this muscle model, aging was associated with an increased resting flow but a remarkably unaffected long-term flow response to a vasodilatory stimulus and endothelial ultrastructure.

Effect of age on blood vessels and neurovascular appositions in the CA1 region of the rat hippocampus

Rats aged 3, 9, 24 and 30 months were used in this study. Increased basal lamina thickening in capillaries, muscular large vessels and nonmuscular large vessels was shown with advancing age. There is also an age-related increase in the area of mitochondria in smooth muscle cells. These ultrastructural changes may underlie observed age-related functional changes in the vasculature. They may be a compensatory response of the vessel wall cells to a declining capacity to handle the continual and varying shear stress exerted by the blood. Ultrastructural differences between capillaries and the two types of large vessels are reported and discussed in terms of their functional significance. It was noted that there are more dendrites adjacent to capillaries than to large vessels, however, this was unaffected by increasing age. Since advancing age did not alter the number of neuronal processes adjacent to vessels, age-related compromises in vessel function may not be subjected to neuronal regulation.

Effects of nitrous oxide on global and regional cortical blood flow

We conducted regional cortical blood flow studies using the xenon-133 clearance technique on 12 volunteers during the administration of 25% and 50% N2O and during baseline conditions (breathing room air or 100% O2). Global cortical blood flow was very highly significantly increased above baseline measures in all subjects by 50% N2O (mean increase 37% above 100% O2 condition). A smaller but still significant increase was observed with 25% N2O. Analysis of regional cortical blood flow revealed heterogeneity in the pattern of changes; that is, the baseline pattern was altered by the inhalation of N2O, most often resulting in an accentuation of relative frontal blood flow. The anterior-posterior gradient in N2O-induced blood flow changes differs from that observed with simple vasodilatory agents, such as CO2, with which the increase is purely systemic and the baseline pattern is preserved. This indicates that N2O has differential effects on cerebral metabolism that may well reflect the typical alterations in experiential state reported by subjects.

Stroke risk and age do not predict behavioral activation of brain blood flow

Twenty-four neurologically normal subjects, 12 in their twenties and 12 in their sixties, were included in a protocol that studied the relationship of resting cerebral blood flow and cerebral blood flow activation by neuropsychological testing to age and stroke risk factors. Both age and a stroke risk index were predictive of a reduced resting cerebral blood flow. Despite this, cerebral blood flow activation relative to resting flow was preserved. Subclinical lesions of deep white matter are proposed to explain the apparently paradoxical result that resting cerebral blood flow is decreased by factors that damage cerebral vessels, while cerebral vascular reactivity is unimpaired.

Randomized clinical trial of daily aspirin therapy in multi-infarct dementia. A pilot study

Seventy multi-infarct dementia patients were randomized into an aspirin-treated group and an untreated control group for an exploratory investigation to determine any effects of 325 mg aspirin daily on cognitive performance. The control group did not receive placebo but evaluations were carried out in a blinded manner. The index group (N = 37, mean age 67.1 years) received 325 mg of aspirin by mouth once daily while the control group (N = 33, mean age 67.6 years) was followed and treated in a similar manner except that they received no aspirin. Both groups had comparable risk factors for stroke, which were treated similarly, as well as comparable initial cerebral blood flow values, as measured by the 133xenon inhalation method, and initial scores on Cognitive Capacity Screening Examination testing. Patients were evaluated at intervals of one year. Significant improvements were demonstrated for cerebral perfusion values (P less than .0001) and cognitive performance scores (P less than .0001) among aspirin-treated patients compared to untreated controls at each of three annual follow-up evaluations. Both men and women benefited from aspirin therapy and their quality of life and independence appeared to be improved, which was not apparent in the control group. Daily aspirin appears to improve or stabilize declines in cerebral perfusion and cognition among patients with multi-infarct dementia.

Cerebral cortical and white matter reactivity to carbon dioxide

We measured cerebrovascular reactivity to carbon dioxide in the cerebral cortex and the subcortical white matter of 12 healthy adult volunteers (four young subjects aged 21-24, four middle-aged subjects aged 34-40, and four elderly subjects aged 62-85 years). Blood flow was computed from the concentration history of xenon-133 in the volume of interest measured with an ultrapure germanium detector array. End-tidal PaCO2 ranged from 35.4 to 42.6 mm Hg. The mean +/- SD baseline blood flows in the cerebral cortex were 60 +/- 7, 51 +/- 9, and 33 +/- 4 ml/100 cm3/min in the young, the middle-aged, and the elderly subjects, respectively; the corresponding subcortical white matter baseline blood flows were 21 +/- 1, 22 +/- 3, and 16 +/- 5 ml/100 cm3/min. Mean +/- SD cerebrovascular reactivities to carbon dioxide in the cerebral cortex were 2.03 +/- 0.58, 1.36 +/- 0.41, and 0.72 +/- 0.19 ml/100 cm3/min/mm Hg PaCO2 for the young, the middle-aged, and the elderly subjects, respectively; the corresponding reactivities in the subcortical white matter were 0.69 +/- 0.11, 0.59 +/- 0.17, and 0.36 +/- 0.41 ml/100 cm3/min/mm Hg PaCO2. Blood flow and cerebrovascular reactivity in the cerebral cortex of the young subjects were significantly higher than those for white matter and significantly higher than those in the elderly subjects (p less than 0.001). Age vs. blood flow (for the cortex) and age vs. cerebrovascular reactivity (for both cortical gray and subcortical white matter) also showed significant linear correlation (p less than 0.05). However, the age-related changes in white matter blood flow and cerebrovascular reactivity were slow, and the differences among the age groups were not statistically significant.

Additional predisposing risk factors for atherothrombotic cerebrovascular disease among treated hypertensive volunteers

A 7-year prospective study of a cohort of 107 neurologically normal elderly hypertensive volunteers (mean age, 65.8 +/- 8.3 years) was undertaken to investigate the predictive validities of additional risk factors for atherothrombotic cerebrovascular disease including stroke, transient ischemic attacks, reversible ischemic neurological deficits, and multi-infarct dementia. This longitudinal study has been in progress now for 7 years with a mean follow-up interval of 50.12 +/- 5.76 months. Among 107 formerly symptom-free, normal hypertensive volunteers, 25 (23%) have developed cerebrovascular disease, 7 (6.5%) sustained a stroke, 10 (9.3%) developed multi-infarct dementia, and 18 (16.8%) have transient ischemic attacks. None have suffered intracranial hemorrhage. Mean gray matter cerebral blood flow (CBF) values measured at the initial visit were sensitive predictors of cerebrovascular disease. Eight of 16 hypertensives (50%) with initial CBF values below 60.0 ml/100 g/min now exhibit signs and symptoms of cerebrovascular disease, while 11 of 43 hypertensives (25.6%) with initial CBF values between 60.1 and 69.9 ml/100 g/min and only 6 of 48 (12.5%) with initial CBF levels above 70.0 developed cerebrovascular disease. Incidence of cerebrovascular disease among cigarette smoking hypertensive volunteers (32.5%) was significantly greater than among nonsmokers (17.2%).

Cognitive performance correlates with cerebrovascular impairments in multi-infarct dementia

Cerebral blood flow (CBF) was measured by the 133Xe inhalation method in patients with multi-infarct dementia (MID, N = 26), Alzheimer's dementia (AD, N = 19), and among age-matched, neurologically normal, healthy volunteers (N = 26). Cognitive performance was assessed in all subjects using the Cognitive Capacity Screening Examination (CCSE). Cerebral vasomotor responses were calculated from differences in values of mean hemispheric gray matter blood flow (Delta CBF) measured during inhalation of 100% oxygen (hyperoxia) compared with CBF measured while breathing room air. Significant correlations were found between CCSE performance and vasomotor responsiveness in patients with MID (P less than .01), but not in patients with AD or in neurologically normal volunteers. Loss of vasomotor responsiveness is an indicator of cerebrovascular disease with rigidity and/or loss of reactivity of cerebral vessels, which impairs cerebrovascular responses to situational demands and predisposes to cerebral ischemia. Loss of cerebral vasomotor responsiveness among MID patients, which is a biologic marker of cerebrovascular disease, provides confirmatory evidence of the vascular etiology of MID and assists in separating MID from AD patients.