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Hemodynamics in internal carotid artery occlusion examined by positron emission tomography
H Yamauchi1, H Fukuyama, J Kimura
1Department of Neurology, Kyoto University School of Medicine, Japan.
Insights
Patients with internal carotid artery occlusion show reduced blood flow in brain watershed areas. This highlights the vulnerability of these regions and the importance of systemic factors like blood pressure in stroke development.
Area of Science:
- Neurology
- Cerebrovascular Medicine
- Medical Imaging
Background:
- Unilateral internal carotid artery occlusion can compromise cerebral blood flow.
- Watershed areas are particularly vulnerable to hemodynamic changes.
- Assessing regional hemodynamic status is crucial for understanding stroke risk.
Purpose of the Study:
- To analyze regional cerebral blood flow (CBF), oxygen metabolism, and hemodynamics in patients with minor strokes and unilateral internal carotid artery occlusion.
- To investigate the hemodynamic status of watershed areas in relation to collateral circulation.
- To identify factors contributing to watershed infarction.
Main Methods:
- Positron emission tomography (PET) was used in nine patients with minor strokes and unilateral internal carotid artery occlusion.
- Regional cerebral blood flow, cerebral metabolic rate of oxygen, oxygen extraction fraction, and cerebral blood volume were quantified.
- Patient data were compared with eight healthy controls.
Main Results:
- Patients exhibited significantly decreased regional CBF in the middle cerebral artery territory and watershed areas of the occluded hemisphere (p < 0.01).
- Oxygen extraction fraction increased with distance from the circle of Willis, peaking in watershed areas.
- A reduced CBF/cerebral blood volume ratio indicated decreased mean blood flow velocity, suggesting blood viscosity impacts CBF.
Conclusions:
- Watershed areas are hemodynamically vulnerable following internal carotid artery occlusion, even with good collateral circulation.
- Systemic hemodynamic factors, including blood pressure and blood volume, play a significant role in watershed infarction.
- PET imaging provides valuable insights into regional brain hemodynamics and stroke risk assessment.
Abstract:
Using positron emission tomography in nine patients with minor strokes, unilateral internal carotid artery occlusion, and good collateral circulation through the anterior portion of the circle of Willis, we analyzed regional cerebral blood flow, cerebral metabolic rate of oxygen, oxygen extraction fraction, and cerebral blood volume. These studies allowed quantification of the regional hemodynamic status, especially in relation to watershed areas. Compared with eight normal controls, the patients had significantly (p less than 0.01) decreased regional cerebral blood flow in the middle cerebral artery territory and the surrounding watershed areas of the occluded hemisphere. The oxygen extraction fraction rose with the distance from the anterior portion of the circle of Willis, attaining the highest value in the superior parietal and posterior temporo-occipital watershed area. A concomitant decrease in the cerebral blood flow/cerebral blood volume ratio suggested reduction in the mean blood flow velocity, whereby elevated blood viscosity would be more liable to reduce cerebral blood flow. These findings suggest hemodynamic vulnerability of the watershed areas after internal carotid artery occlusion in persons with good collateral circulation through the anterior portion of the circle of Willis. Our results also emphasize the importance of systemic hemodynamic factors such as blood pressure and circulating blood volume in the genesis of watershed infarction.