Intracranial Hemodynamic Compensation Mechanisms in Patients with Cerebrovascular Disease

Abstract

Cerebrovascular disease (CVD) encompasses conditions that affect the blood supply to the brain. CVD results in hemodynamic impairment, and when the brain can no longer compensate for decreased oxygen delivery to tissue, stroke results. The development and validation of tools to evaluate parenchymal impairment is important not only for determination of patient-specific disease severity and outcomes following intervention, but also for utilization in clinical trials to stratify patients and determine treatment success. Positron emission tomography laid the foundation for understanding the hemodynamic and metabolic changes in CVD, and which confer significantly elevated stroke risk. In recent years, significant progress has been made toward the evaluation of hemodynamic and metabolic processes in the brain using non-invasive magnetic resonance imaging (MRI) without the use of exogenous contrast agents. Important questions remain regarding the sensitivity of non-invasive methods to detect impairment or improvement, and predict subsequent stroke. The results contained aim to address gaps related to sensitivity of functional MR methods to disease and intervention outcome, as well as extend upon currently available tools for parenchymal assessment by:

1. Evaluating a potential marker of global hemodynamic impairment (oxygen extraction fraction, OEF: ratio of oxygen consumed to oxygen delivered) in CVD compared to healthy controls.

2. Evaluating improvement in cerebrovascular compliance measures following surgical intervention in moyamoya, and comparing these findings to gold-standard digital subtraction angiography.

3. Extending the functionality of an existing MR method for global OEF determination toward hemispheric and regional measurements.