Gender and risk factor dependence of cerebral blood flow velocity in Chinese adults

The influence of obesity on cerebral blood flow in young adults using arterial spin labeling MRI

Obesity causes damage to several organs, including the brain. Recent studies have been focusing on understanding the mechanisms through which obesity affects brain structure and function using neuroimaging techniques. A functional biomarker, such as cerebral blood flow (CBF), is a powerful tool that can be used to explore neural dysfunction. However, there is currently limited information regarding the association between CBF and obesity. The study was conducted to investigate the potential effect of obesity on brain perfusion in a young cohort aged 20-30 years. A total of 21 obese (body mass index (BMI) > 26 kg/m² ) and 21 lean (BMI < 24 kg/m² ) right-handed volunteers were included in this study. CBF was acquired using the 2D single post-labeling delay (PLD) arterial spin labeling (ASL) technique on a 3 T MRI scanner. A multiple regression analysis was performed to examine the difference in global and regional gray matter (GM) CBF between the groups. CBF value was assigned as the dependent variable, whereas age, sex, and group (obese or lean) were considered as the independent variables. Results showed that group-related differences in CBF were homogeneous across brain regions, as obese subjects had significantly lower global GM CBF than lean subjects (P < 0.05). In the voxelwise analysis, obese individuals had significantly lower CBF in the left pulvinar of the thalamus and visual association areas, including Brodmann area (BA) 7, BA18, and BA19, than lean subjects. Although the signal-to-noise ratio was slightly compromised for 2D sequences and subject-specific arterial transit time was not estimated due to a single PLD sequence, this study demonstrated alterations in CBF in obese subjects, particularly in regions of the pulvinar of the thalamus and its synchronously related areas such as visual association areas. These results suggest that ASL provides a potential platform for further obesity-related research.

Whole blood viscosity and cerebral blood flow velocities in obese hypertensive or obese normotensive adolescents

BACKGROUND

Obesity affects all major organ systems and leads to increased morbidity and mortality. Whole blood viscosity is an important independent regulator of cerebral blood flow. The aim of the present study was to evaluate the effect of whole blood viscosity on cerebral artery blood flow velocities using transcranial Doppler ultrasound in pediatric patients with obesity compared to healthy controls and analyze the effect of whole blood viscosity and blood pressure status to the cerebral artery blood flow velocities.

METHODS

Sixty patients with obesity diagnosed according to their body mass index (BMI) percentiles aged 13-18 years old were prospectively enrolled. They were grouped as hypertensive or normotensive according to their ambulatory blood pressure monitoring. Whole blood viscosity and middle cerebral artery velocities by transcranial Doppler ultrasound were studied and compared to 20 healthy same aged controls.

RESULTS

Whole blood viscosity values in hypertensive (0.0619±0.0077 poise) and normotensive (0.0607±0.0071 poise) groups were higher than controls (0.0616±0.0064 poise), with no significance. Middle cerebral artery blood flow velocities were higher in the obese hypertensive (73.9±15.0 cm/s) and obese normotensive groups (75.2±13.5 cm/s) than controls (66.4±11.5 cm/s), but with no statistical significance.

CONCLUSIONS

Physiological changes in blood viscosity and changes in blood pressure did not seem to have any direct effect on cerebral blood flow velocities, the reason might be that the cerebral circulation is capable of adaptively modulating itself to changes to maintain a uniform cerebral blood flow.

Peak Systolic Velocity Measurements with Transcranial Doppler Ultrasound Is a Predictor of Incident Stroke among the General Population in China

BACKGROUND AND OBJECTIVE

It is necessary to develop an effective and low-cost screening tool for identifying Chinese people at high risk of stroke. Transcranial Doppler ultrasound (TCD) is a powerful predictor of stroke in the pediatric sickle cell disease population, as demonstrated in the STOP trial. Our study was conducted to determine the prediction value of peak systolic velocities as measured by TCD on subsequent stroke risk in a prospective cohort of the general population from Beijing, China.

METHODS

In 2002, a prospective cohort study was conducted among 1392 residents from 11 villages of the Shijingshan district of Beijing, China. The cohort was scheduled for follow up with regard to incident stroke in 2005, 2007, and 2012 by a study team comprised of epidemiologists, nurses, and physicians. Univariate and multivariate Cox proportional hazard regression models were used to determine the factors associated with incident stroke.

RESULTS

Participants identified by TCD criteria as having intracranial stenosis had a 3.6-fold greater risk of incident stroke (hazard ratio (HR) 3.57, 95% confidence interval (CI) 1.86-6.83, P<0.01) than those without TCD evidence of intracranial stenosis. The association remained significant in multivariate analysis (HR 2.53, 95% CI 1.31-4.87) after adjusting for other risk factors or confounders. Older age, cigarette smoking, hypertension, and diabetes mellitus remained statistically significant as risk factors after controlling for other factors.

CONCLUSIONS

The study confirmed the screening value of TCD among the general population in urban China. Increasing the availability of TCD screening may help identify subjects as higher risk for stroke.

Doppler study of cerebral arteries in hypercholesterolemia

Background:

Hypercholesterolemia is one of the major modifiable risk factors for atherosclerosis of the coronary and carotid arteries. Although transcranial Doppler (TCD) studies of the cerebral arteries are indicative of decreased cerebral blood flow velocities in patients with hypercholesterolemia, the number of these studies has been limited. The aim of this study was to assess the hemodynamic status of the cerebral arteries in patients with hypercholesterolemia using TCD.

Methods:

In a case-control study, 60 individuals, including 30 hypercholesterolemic cases (low-density lipoprotein [LDL] > 160 mg/dL) and 30 healthy controls were enrolled. Other arterial risk factors, including diabetes mellitus, hypertension, smoking, and obesity (body mass index > 30), were evaluated and matched as well. TCD was used to assess the hemodynamics of the intracranial arteries as well as the internal carotid arteries. The mean blood flow velocity, pulsatility index, and resistance index were recorded in all the arteries.

Results:

The mean blood flow velocity, pulsatility index, and resistance index of the intracranial arteries and internal carotid arteries were not significantly different between the two groups (P > 0.05). However, those with higher levels of LDL (>180 mg/dL) showed significantly lower mean blood flow velocity and resistance index of the internal carotid arteries than the healthy controls. In addition, individuals with high-density lipoprotein (HDL) <35 mg/dL had significantly lower mean blood flow velocity in the internal carotid arteries.

Conclusion:

Hypercholesterolemia (LDL >160 mg/dL) does not seem to have a detrimental effect on the hemodynamic status of the intracranial arteries and internal carotid arteries. However, in cases of higher LDL (>180 mg/dL) and lower HDL, decreased TCD parameters in the internal carotid arteries, as a surrogate of the peripheral arteries, are prominent.