Net Cerebrospinal Fluid Flow Research Articles

Significant individual variation in cardiac-cycle-linked cerebrospinal fluid production following subarachnoid hemorrhage

BackgroundSpontaneous subarachnoid hemorrhage (SAH) often results in altered cerebrospinal fluid (CSF) flow and secondary hydrocephalus, yet the mechanisms behind these phenomena remain poorly understood. This study aimed to elucidate the impact of SAH on individual CSF flow patterns and their association with secondary hydrocephalus.MethodsIn patients who had experienced SAH, changes in CSF flow were assessed using cardiac-gated phase-contrast magnetic resonance imaging (PC-MRI) at the Sylvian aqueduct and cranio-cervical junction (CCJ). Within these regions of interest, volumetric CSF flow was determined for every pixel and net CSF flow volume and direction calculated. The presence of acute or chronic hydrocephalus was deemed from ventriculomegaly and need of CSF diversion. For comparison, we included healthy subjects and patients examined for different CSF diseases.ResultsTwenty-four SAH patients were enrolled, revealing a heterogeneous array of CSF flow alterations at the Sylvian aqueduct. The cardiac-cycle-linked CSF net flow in Sylvian aqueduct differed from the traditional figures of ventricular CSF production about 0.30–0.40 mL/min. In 15 out of 24 patients (62.5%), net CSF flow was retrograde from the fourth to the third and lateral ventricles, while it was upward at the cranio-cervical junction in 2 out of 2 patients (100%). The diverse CSF flow metrics did not distinguish between individuals with acute or chronic secondary hydrocephalus. In comparison, 4/4 healthy subjects showed antegrade net CSF flow in the Sylvian aqueduct and net upward CSF flow in CCJ. These net CSF flow measures also showed interindividual variability among other patients with CSF diseases.ConclusionsThere is considerable inter-individual variation in net CSF flow rates following SAH. Net CSF flow in the Sylvian aqueduct differs markedly from the traditional ventricular CSF production rates of 0.30–0.40 mL/min in SAH patients, but less so in healthy subjects. Furthermore, the cardiac-cycle-linked net CSF flow rates in Sylvian aqueduct and CCJ suggest an important role of extra-ventricular CSF production.

Perivascular pumping of cerebrospinal fluid in the brain with a valve mechanism.

The flow of cerebrospinal fluid (CSF) along perivascular spaces (PVSs) is an important part of the brain's system for clearing metabolic waste. Experiments reveal that arterial motions from cardiac pulsations and functional hyperaemiadrive CSF in the same direction as the blood flow, but the mechanism producing this directionality is unclear. Astrocyte endfeet bound the PVSs of penetrating arteries, separating them from brain extracellular space (ECS) and potentially regulating flow between the two compartments. Here, we present two models, one based on the full equations of fluid dynamics and the other using lumped parameters, in which the astrocyte endfeet function as valves, regulating flow between the PVS and the ECS. In both models, cardiac pulsations drive a net CSF flow consistent with prior experimental observations. Functional hyperaemia, acting with cardiac pulsation, increases the net flow. We also find, in agreement with experiments, a reduced net flow during wakefulness, due to the known decrease in ECS permeability compared to the sleep state. We present in vivo imaging of penetrating arteries in mice, which we use to measure accurately the amplitude of their constrictions and dilations during both cardiac pulsation and functional hyperaemia, an important input for the models. Our models can be used to explore the effects of changes in other input parameters, such as those caused by ageing or disease, as better measurements of these parameters become available.

Cerebrospinal Fluid Flow in Patients with Huntington's Disease.

Investigations of cerebrospinal fluid (CSF) flow aberrations in Huntington's disease (HD) are of growing interest, as impaired CSF flow may contribute to mutant Huntington retention and observed heterogeneous responsiveness to intrathecally administered therapies. We assessed net cerebral aqueduct CSF flow and velocity in 29 HD participants (17 premanifest and 12 manifest) and 51 age- and sex matched non-HD control participants using 3-Tesla magnetic resonance imaging methods. Regression models were applied to test hypotheses regarding: (i) net CSF flow and cohort, (ii) net CSF flow and disease severity (CAP-score), and (iii) CSF volume after correcting for age and sex. Group-wise analyses support a decrease in net CSF flow in HD (mean 0.14 ± 0.27 mL/min) relative to control (mean 0.32 ± 0.20 mL/min) participants (p = 0.02), with lowest flow in the manifest HD cohort (mean 0.04 ± 0.25 mL/min). This finding was explained by hyperdynamic CSF movement, manifesting as higher caudal systolic CSF flow velocity and higher diastolic cranial CSF flow velocity across the cardiac cycle, in HD (caudal flow: 0.17 ± 0.07 mL/s, cranial flow: 0.14 ± 0.08 mL/s) compared to control (caudal flow: 0.13 ± 0.06 mL/s, cranial flow: 0.11 ± 0.04 mL/s) participants. A positive correlation between cranial diastolic flow and disease severity was observed (p = 0.02). Findings support aqueductal CSF flow dynamics changing with disease severity in HD. These accelerated changes are consistent with changes observed over the typical adult lifespan, and may have relevance to mutant Huntington retention and intrathecally administered therapeutics responsiveness. ANN NEUROL 2023;94:885-894.

Sleep quality associated with neuroimaging measures of CSF flow in individuals with Parkinson’s disease (N5.001)

<h3>Objective:</h3> To investigate the relationship between sleep quality and cerebrospinal fluid (CSF) flow in individuals with Parkinson’s disease (PD). <h3>Background:</h3> Previous studies have emphasized the role of CSF circulation in the clearance of brain waste products, with recent findings demonstrating increased CSF flow during sleep. CSF circulation impairment could play a major role in neurodegenerative proteinopathies such as PD, a commonly encountered feature of which is disrupted sleep. Here, we assessed the relationship between patient-reported sleep quality and imaging assays of CSF flow. <h3>Design/Methods:</h3> Imaging and clinical assessments were completed in 23 PD participants aged 56 to 79 (M_age=66.70; 16 males). The Montreal Cognitive Assessment (MoCA) and Unified Parkinson’s Disease Rating Scale (UPDRS) were administered; subjective sleep measurements were recorded using the Sleep Disturbance (SD) and Sleep-Related Impairment (SRI) items from the Patient-Reported Outcomes Measurement Information System (PROMIS) scale. MRI phase contrast sequences quantified CSF flux (mL/min) via the cerebral aqueduct. Net CSF flow was defined as the difference between caudal and cranial flow, whereas absolute flow was calculated as the sum of total caudal and cranial flow per cardiac cycle. <h3>Results:</h3> Participants had mean MoCA scores of 24.17 (range 13–30) and UPDRS scores of 30.70 (7–59). PROMIS scores for SD and SRI were 20.14 (9–32) and 15.00 (8–24), respectively. Mean CSF measurements were 0.25 mL/min (−0.29–0.88) for net and 8.11 mL/min (3.55–16.34) for absolute flow. Higher SRI scores correlated with greater net CSF flow while awake (r=0.531, p=0.023). Additionally, SRI and age explained 73.4% of variation in absolute CSF flow in a linear regression model (F(3,15)=24.5, p&lt;0.0001). <h3>Conclusions:</h3> Self-reported sleep impairment is associated with increased CSF flow in awake individuals with PD. This study is the first to link patient-reported measures of sleep with alterations to CSF flow. These data support novel outcomes for clinical studies that improve sleep. <b>Disclosure:</b> Mr. Ponzo has nothing to disclose. Dr. Hett has nothing to disclose. Mr. Eisma has nothing to disclose. Mr. Elenberger has nothing to disclose. Mr. Song has nothing to disclose. An immediate family member of Dr. McKnight has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Deciphera. The institution of Dr. McKnight has received research support from RSNA. Dr. Considine has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for MDisrupt. Dr. Considine has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for Park Dietz &amp; Associates. The institution of Dr. Considine has received research support from NIH. The institution of Dr. Considine has received research support from DoD. The institution of Dr. Considine has received research support from Acadia Pharmaceuticals. Manus Donahue, 13717 has received personal compensation for serving as an employee of Alterity. Manus Donahue, 13717 has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Alterity. Manus Donahue, 13717 has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Pfizer. Manus Donahue, 13717 has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Global Blood Therapeutics. Manus Donahue, 13717 has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Pfizer. The institution of Manus Donahue, 13717 has received research support from National Institutes of Health. Dr. Claassen has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Teva Neuroscience. Dr. Claassen has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Spark . The institution of Dr. Claassen has received personal compensation in the range of $50,000-$99,999 for serving as a Consultant for Alterity. Dr. Claassen has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Teva Neuroscience. Dr. Claassen has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for HD Insights. The institution of Dr. Claassen has received research support from NIH. The institution of Dr. Claassen has received research support from CHDI. The institution of Dr. Claassen has received research support from HDSA. The institution of Dr. Claassen has received research support from Department of Defense. The institution of Dr. Claassen has received research support from Griffin Family Foundation. The institution of Dr. Claassen has received research support from Neurocrine. The institution of Dr. Claassen has received research support from Vaccinex. The institution of Dr. Claassen has received research support from AbbVie. The institution of Dr. Claassen has received research support from CHDI. The institution of Dr. Claassen has received research support from Genentech/ Roche. The institution of Dr. Claassen has received research support from Prilenia. The institution of Dr. Claassen has received research support from Neurocrine/ HSG.

Choroid plexus perfusion and bulk cerebrospinal fluid flow across the adult lifespan

The choroid plexus (ChP) comprises a collection of modified ependymal cells that play an important role in the production of brain cerebrospinal fluid (CSF), and ChP perfusion aberrations have been implicated in a range of cerebrovascular and neurodegenerative disorders. To provide an exemplar for the growing interest in ChP activity, we evaluated ChP perfusion and bulk CSF flow cross-sectionally across the healthy adult lifespan. Participants (n = 77; age range = 21–86 years) were scanned at 3T using T1-weighted, T2-weighted-FLAIR, perfusion-weighted pCASL, and phase contrast MRI to calculate ChP anatomy, perfusion, and aqueductal CSF flow, respectively. Regression models were applied to evaluate aging effects on ChP volume and ChP perfusion in the lateral ventricles, as well as CSF flow. ChP volume (mean ± std = 2.81 ± 1.1 cm3) increased (p < 0.001), ChP perfusion (36.3 ± 8.6 mL/100 g/min) decreased (p = 0.0078), and ChP total blood flow (1.13 ± 0.34 mL/min) increased (p < 0.001) with age. Cranial-to-caudal net CSF flow (0.245 ± 0.20 mL/min) decreased, absolute CSF flow (4.86 ± 2.96 mL/min) increased, and CSF regurgitant fraction (0.87 ± 0.126) increased with age (all: p < 0.001). ChP perfusion was directly related to net cranial-to-caudal CSF flow through the aqueduct (p = 0.033). The implications of these findings are discussed in the context of the growing literature on CSF circulatory dysfunction in neurodegeneration and cerebrovascular disease.

Cerebrospinal fluid flow driven by arterial pulsations in axisymmetric perivascular spaces: Analogy with Taylor’s swimming sheet

Cerebrospinal fluid (CSF) flow in the perivascular space (PVS), which surrounds the arteries in the brain, is of paramount importance in the removal of metabolic waste. Despite a number of experimental and numerical studies regarding CSF flow, the underlying mechanics of CSF flow are still debated, especially regarding whether an arterial pulsation can indeed produce net CSF flow velocity. Furthermore, the relationship between CSF flow and arterial wall pulsation has not been fully defined. To clarify these questions, we numerically investigated the CSF flow in the PVS in an axisymmetric channel with a pulsating boundary, where CSF is modeled as an incompressible, Newtonian viscous fluid in non-porous space. Our numerical results show that the net CSF flow velocity driven by the arterial pulsation is consistent with that of previous animal experiments. However, the peak oscillatory velocity is two orders of magnitude larger than the net velocity. Interestingly, the net CSF flow velocity collapses on the analytical solution derived from the lubrication theory in analogy with Taylor’s swimming sheet model.

Phase contrast MRI measurements of net cerebrospinal fluid flow through the cerebral aqueduct are confounded by respiration.

BackgroundNet cerebrospinal fluid (CSF) flow through the cerebral aqueduct may serve as a marker of CSF production in the lateral ventricles, and changes that occur with aging and in disease.PurposeTo investigate the confounding influence of the respiratory cycle on net CSF flow and stroke volume measurements.Study TypeCross‐sectional study.SubjectsTwelve young, healthy subjects (seven male, age range 19–39 years, average age 28.3 years).Field Strength/SequencePhase contrast MRI (PC‐MRI) measurements were performed at 7T, with and without respiratory gating on expiration and on inspiration. All measurements were repeated.AssessmentNet CSF flow and stroke volume in the aqueduct, over the cardiac cycle, was determined.Statistical TestsRepeatability was determined using the intraclass correlation coefficient (ICC) and linear regression analysis between the repeated measurements. Repeated measures analysis of variance (ANOVA) was performed to compare the measurements during inspiration/expiration/no gating. Linear regression analysis was performed between the net CSF flow difference (inspiration minus expiration) and stroke volume.ResultsNet CSF flow (average ± standard deviation) was 0.64 ± 0.32 mL/min (caudal) during expiration, 0.12 ± 0.49 mL/min (cranial) during inspiration, and 0.31 ± 0.18 mL/min (caudal) without respiratory gating. Respiratory gating did not affect stroke volume measurements (41 ± 18, 42 ± 19, 42 ± 19 μL/cycle for expiration, no respiratory gating and inspiration, respectively). Repeatability was best during inspiration (ICC = 0.88/0.56/–0.31 for gating on inspiration/expiration/no gating). A positive association was found between average stroke volume and net flow difference between inspiration and expiration (R = 0.678/0.605, P = 0.015/0.037 for the first/second repeated measurement).Data ConclusionMeasured net CSF flow is confounded by respiration effects. Therefore, net CSF flow measurements with PC‐MRI cannot in isolation be directly linked to CSF production. Level of Evidence: 1 Technical Efficacy: Stage 2J. Magn. Reson. Imaging 2019;49:433–444.

Assessment of CSF Flow Dynamics Using PC‐MRI in Spontaneous Intracranial Hypotension

Spontaneous intracranial hypotension (SIH) is caused by spontaneous cerebrospinal fluid (CSF) leaks and is known to cause orthostatic headaches. Phase-contrast magnetic resonance imaging (PC-MRI) is a non-invasive technique that can be used to quantify variation in CSF flow. The aim of this study was to assess CSF flow dynamics using PC-MRI in SIH. Twenty-five patients with a definitive diagnosis of SIH and 25 healthy subjects were evaluated with PC-MRI. Magnetic resonance (MR) images were acquired using a 1.5-T unit with an 8-channel head coil. Differences between SIH patients and control subjects were assessed statistically using Wilcoxon's rank sum test, Spearman's rho test, or Pearson's chi-square test, as appropriate. CSF flow volumes toward the third ventricle, CSF flow volumes toward the fourth ventricle, the absolute stroke volume, the peak systolic velocity, and the peak diastolic velocity in SIH patients were significantly smaller than those in control subjects (P < .0001). On the other hand, the net CSF flow volume (P = .9227) and the net CSF flow direction (P = .2472) for SIH patients and control subjects were not significantly different. The results obtained by CSF flow analysis were directly related to values of CSF opening pressure, determined by lumbar puncture, and clinical findings, such as headache scores. Thus, CSF flow analysis with PC-MRI, which has a short performance time and is non-invasive, may contribute to assessment of SIH patients.

Temporal and spatial assessment of normal cerebrospinal fluid dynamics with MR imaging

The purpose of this study was to measure normal cerebrospinal fluid (CSF) pulsations within the intracranial and upper cervical subarachnoid spaces and the ventricular system. Phase contrast cine MR sequences were performed in sagittal and axial planes on 13 volunteers with flow encoding in the craniocaudal direction. CSF pulsations displayed considerable variations in healthy subjects, depending both on measurements localization and subjects, with CSF peak velocities ranging from 0 to 7 cm/s. In the subarachnoid spaces, the highest velocities occurred in the anterior location and increased from the cerebellar pontine angle cisterns towards the lower cervical spaces. In the ventricular system, the highest velocities occurred through the aqueduct of Sylvius. CSF flow within the third ventricle seemed to reflect a circular motion. There was a caudal net CSF flow in the aqueduct whereas in the upper cervical spaces net CSF flow was caudal anteriorly and cranial laterally. Velocity profiles of CSF pulsations demonstrated arterial morphology. After the R wave, caudal systolic motion was first observed in the posterior subarachnoid spaces, soon after in the anterior subarachnoid spaces and later in the ventricular system. Considering the morphology of CSF pathways, three successively initiated phenomena may explain the temporal course of CSF motion: the systolic expansion of the main arteries at the base of the brain, the systolic expansion of the cerebrospinal axis and, finally, the systolic expansion of the choroid plexuses.