Changing Concepts of Cerebrospinal Fluid Hydrodynamics: Role of Phase-Contrast Magnetic Resonance Imaging and Implications for Cerebral Microvascular Disease

Abstract

Summary: Phase-contrast magnetic resonance imaging (PC-MRI) or flow-sensitive MRI can be used to noninvasively measure intracranial vascular and CSF flow. Monro-Kellie homeostasis is the complex compensatory mechanism for the increase in intracranial blood volume during systole. Through PC-MRI techniques, our understanding of Monro-Kellie homeostasis and the associated intracranial hydrodynamics has greatly improved. Failure of this homeostatic mechanism has been implicated in a wide range of cerebral disorders, including vascular and Alzheimer's dementia, late-onset depression, benign and secondary intracranial hypertension, communicating and normal pressure hydrocephalus, and age-related white matter changes. The most common mode of homeostatic failure is due to vascular disease with decreased cerebral arterial compliance. This has wide-reaching implications in the investigation of patients with cerebral vascular disease. Here we discuss the role of PC-MRI in the study of cerebral hydrodynamics and the current understanding of Monro-Kellie homeostasis in both healthy and disease states. Quantitative assessment of the changes in this homeostatic mechanism using PC-MRI has important implications in the development of biomarkers of vascular involvement in disease with application in diagnosis, treatment planning, phenotype identification, and outcome assessment in clinical trials.

Velocity and pressure gradients of cerebrospinal fluid assessed with magnetic resonance imaging

“…Today, the development of the PC methods has dramatically improved our understanding of CSF flow dynamics and has changed the concepts of CSF dynamics including the bulk-flow theory. 28 Nevertheless, previously, the PC method was only useful for determining the direction of the CSF movement indicated by vector or signal intensity determined by visual recordings, or the CSF movement was calculated on the basis of the velocity of the CSF. However, analysis of velocity alone describes only some aspects of the CSF motion.…”

Intracranial atherosclerosis as a contributing factor to Alzheimer's disease dementia

“…The pulsatile movements result in arterial expansion and concomitant brain volume enlargement assisted by systolic capillary dilation and venous and subarachnoid space engorgement. Recoil of CSF from the spinal canal into the brain's subarachnoid space occurs during diastole [50;51]. Dilation of the brain ventricles in AD correlates with the degree of cerebral blood flow impingement created by advanced atherosclerotic and arteriosclerotic lesions.…”

Magnetic resonance velocity mapping of 3D cerebrospinal fluid flow dynamics in hydrocephalus: preliminary results

“…Significant differences are marked with an asterisk "*". Scale of classification: 0 = not detectable/no information, 1 = poor, 2 = acceptable, 3 = good, and 4 = excellent [13][14][15][16][17][28][29][30][31]. However, the examination of CSF flow dynamics in clinical routine as well as in research is almost always limited to 2D PC-MRI experiments using velocity encoding in only one spatial direction, which resulted in in-plane velocity images or through-plane flow curves.…”