Cerebrospinal fluid circulation

• Diagnostic and phylogenetic perspectives of the 2023 Murray Valley encephalitis virus outbreak in Australia: an observational study
• Genomic profiling and prognostic factors of leptomeningeal metastasis in EGFR-mutant NSCLC after resistant to third-generation EGFR-tyrosine kinase inhibitors
• The Relationship Between Glymphatic Function, White Matter Hyperintensity and Cognition: A Structural Equation Model MRI Study
• Cerebrospinal Fluid-Derived Genomic Alterations Tracking Glioma
• Advances in Circulating Biomarkers for Neurodegenerative Diseases, Traumatic Brain Injuries, and Central Nervous System Tumors
• Uncommon Locations for Brain Herniations Into Arachnoid Granulations: 5 Cases and Literature Review
• Glymphatic Function Abnormality and Its Association With Pathophysiology in Primary Open-Angle Glaucoma
• Diagnostic Challenges in Creutzfeldt-Jakob Disease: A Case Report of an Atypical Presentation

Cerebrospinal fluid (CSF) circulation refers to the continuous flow and movement of CSF within the central nervous system (CNS), which includes the ventricles of the brain, the subarachnoid space around the brain and spinal cord, and the spaces surrounding the spinal cord itself. This circulation is vital for maintaining homeostasis in the CNS, facilitating waste removal, nutrient delivery, and mechanical cushioning for the brain and spinal cord.

Cerebrospinal fluid production

Cerebrospinal fluid absorption.

Breathing and Cardiac Activity: Both respiratory and heart cycles influence CSF circulation through the impact of pressure changes within the chest cavity, which can affect the venous return and CSF flow dynamics.

Obstructions: Any blockages in the ventricular system, such as those caused by tumors, cysts, or infections, can alter CSF circulation, leading to conditions like hydrocephalus.

Age and Disease: Age-related changes or neurodegenerative diseases like Alzheimer’s or Parkinson’s can impair CSF dynamics, potentially affecting the brain’s ability to clear waste products and maintain homeostasis.

Understanding CSF circulation is critical in diagnosing and managing conditions such as hydrocephalus, intracranial hypertension, and spinal cord diseases. Imaging techniques like MRI and CT scans are used to visualize CSF flow, identify blockages, or assess changes in CSF pressure. More advanced methods, such as phase-contrast MRI, allow for real-time assessment of CSF flow dynamics, offering insights into both physiological and pathological changes in CSF circulation.

Cerebrospinal fluid, occupying the subarachnoid space, is elaborated in an active process by the choroid plexus. It supports the brain and spinal cord and acts in lieu of a lymphatic system for central nervous tissue. Whether or not absorption of CSF into dural venous sinuses is an active or passive process is still controversial. A very thin layer of bone separates the posterior ethmoid air sinus from the subarachnoid space. There appears to be potential in man for flow of cerebrospinal fluid into the perilymphatic space of the inner ear, but it seldom occurs ¹⁾.

Cerebrospinal fluid (CSF) is continuously produced at a 0.4-ml per-minute rate with an average rate of 20-ml per-hour.

CSF flows in a pulsatile manner, dependent on the cardiac rhythm. CSF, being associated with increasing intracranial blood flow and pressure in the cardiac systole, made from the cerebrum, passes through the lateral ventricles by means of Foramen of Monro to the third ventricle, then to the fourth ventricle by the aqueduct cerebri, and to the pontine by passing through the cistern and flows within the spinal canal in the subarachnoid gap. In diastole, there is a return flow toward the lateral ventricles.

The CSF contains approximately 0.3% plasma proteins, or approximately 15 to 40 mg/dL, depending on sampling site, and it is produced at a rate of 500 ml/day. Since the subarachnoid space around the brain and spinal cord can contain only 135 to 150 ml, large amounts are drained primarily into the blood through arachnoid granulations in the superior sagittal sinus. Thus the CSF turns over about 3.7 times a day. This continuous flow into the venous system dilutes the concentration of larger, lipid-insoluble molecules penetrating the brain and CSF.

Intracranial pressure (ICP) is derived from the circulatory cerebrospinal fluid dynamics and cerebral blood flow that occur within the rigid intracranial compartment ²⁾.

Several studies have cast doubt on the traditional cerebrospinal fluid (CSF) circulation theory. Some of the criticism has been due to the results of magnetic resonance imaging (MRI) studies, which have indicated that the CSF does not move in a laminar flow in the CSF space. The CSF can move in a turbulent, swirling, oscillating fashion in various parts of the CSF space. Today, many researchers believe that CSF does not act like water in a river, moving in a unidirectional fashion throughout several parts of the CSF space, and the terms CSF flow and cerebrospinal fluid circulation in the CSF space have been replaced with cerebrospinal fluid motion or cerebrospinal fluid movement.

These new concepts arose from several different types of MRI sequences. Unfortunately, most of these imaging techniques do not produce quantitative data, and interpretation is limited to subjective impression. This may not provide a full understanding of the true CSF motion, and cannot be used to identify diseases such as hydrocephalus that involve disturbance of the CSF motion. Additionally, the question has arisen as to how CSF motion changes with aging. Understanding the relation between CSF motion and aging is important to understand the CSF environment. Idiopathic normal pressure hydrocephalus (iNPH) is caused by the disturbance of CSF motion distribution, usually found in elderly individuals, and for this reason it is important to identify the CSF motion in elderly individuals.

The Cerebrospinal fluid (CSF) moves in a pulsatile manner throughout the CSF system with a nearly zero net flow, as shown on an MRI.

The cerebrospinal fluid flow speed and its direction can be measured non-invasively via Phase contrast magnetic resonance imaging (Cine-Contrast MR). When CSF flow is obstructed at any level, hydrocephalus occurs ^{3) 4)}.

Cerebrospinal fluid flows throughout the inner ventricular system in the brain and is absorbed back into the bloodstream, rinsing the metabolic waste from the central nervous system through the blood–brain barrier. This allows for homeostatic regulation of the distribution of neuroendocrine factors, to which slight changes can cause problems or damage to the nervous system. For example, high glycine concentration disrupts temperature and blood pressure control, and high CSF pH causes dizziness and syncope.

To use Davson's term, the CSF has a “sink action” by which the various substances formed in the nervous tissue during its metabolic activity diffuse rapidly into the CSF and are thus removed into the bloodstream as CSF is absorbed.

Cerebrospinal fluid flow.