Abstract
Blood oxygenation-level dependent cerebrovascular reactivity (BOLD-CVR) has gained attention in recent years as an effective way to investigate CVR, a measure of the hemodynamic state of the brain, with high spatial and temporal resolution. An association between impaired CVR and diverse pathologies has been observed, especially in ischemic cerebrovascular diseases and brain gliomas. The ability to obtain this information intraoperatively is novel and has not been widely tested. We report our first experience with this intraoperative technique in vascular and oncologic neurosurgical patients, discuss the results of its feasibility, and the possible developments of the intraoperative employment of BOLD-CVR.
Highlights
Cerebrovascular reactivity (CVR) is the physiological capacity of the brain vessels to modulate cerebral blood flow (CBF) by changing their caliber in response to a vasoactive stimulus: this allows an adequate supply of oxygenated blood to the brain despite wide variations of perfusion pressure [1, 2]
The intraoperative BOLD-CVR assessment was performed at our institution on both oncological and vascular diseases [11, 12, 17, 20] (Table 1)
The aim of introducing and developing BOLD-CVR assessment is to offer a new tool, which could help surgery and influence decision-making by offering an early feedback on the hemodynamic state of the brain
Summary
Cerebrovascular reactivity (CVR) is the physiological capacity of the brain vessels to modulate cerebral blood flow (CBF) by changing their caliber in response to a vasoactive stimulus: this allows an adequate supply of oxygenated blood to the brain despite wide variations of perfusion pressure [1, 2]. CVR can be studied by applying a vasoactive stimulus to a patient and measuring the resulting changes at the brain level, either by CBF modifications or by surrogate of blood flow. To measure hemodynamic changes after administration of a vasoactive stimulus, many methods are granted, like Doppler sonography [9], arterial spin labeling (ASL) [14], or blood oxygenation-level dependent functional magnetic resonance imaging (BOLD-CVR) [3]. Detecting changes in the BOLD signal has proved a valid method with high imaging resolution, allowing a good depiction of the hemodynamic state at brain tissue level. This exploits deoxyhemoglobin paramagnetic properties, which make the BOLD signal get lower with higher blood deoxyhemoglobin concentrations [1, 15]. Areas with a higher blood flow achieve a higher deoxyhemoglobin clearance, thereby displaying a higher oxyhemoglobin/ deoxyhemoglobin ratio, which results in higher BOLD signal [1]
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