Abstract
BackgroundSeveral central nervous system diseases are associated with disturbed cerebrospinal fluid (CSF) flow patterns and have typically been characterized in vivo by phase-contrast magnetic resonance imaging (MRI). This technique is, however, limited by its applicability in space and time. Phase-contrast MRI has yet to be compared directly with CSF tracer enhanced imaging, which can be considered gold standard for assessing long-term CSF flow dynamics within the intracranial compartment.MethodsHere, we studied patients with various CSF disorders and compared MRI biomarkers of CSF space anatomy and phase-contrast MRI at level of the aqueduct and cranio-cervical junction with dynamic intrathecal contrast-enhanced MRI using the contrast agent gadobutrol as CSF tracer. Tracer enrichment of cerebral ventricles was graded 0–4 by visual assessment. An intracranial pressure (ICP) score was used as surrogate marker of intracranial compliance.ResultsThe study included 94 patients and disclosed marked variation of CSF flow measures across disease categories. The grade of supra-aqueductal reflux of tracer varied, with strong reflux (grades 3–4) in half of patients. Ventricular tracer reflux correlated with stroke volume and aqueductal CSF pressure gradient. CSF flow in the cerebral aqueduct was retrograde (from 4th to 3rd ventricle) in one third of patients, with estimated CSF net flow volume about 1.0 L/24 h. In the cranio-cervical junction, net flow was cranially directed in 78% patients, with estimated CSF net flow volume about 4.7 L/24 h.ConclusionsThe present observations provide in vivo quantitative evidence for substantial variation in direction and magnitude of CSF flow, with re-direction of aqueductal flow in communicating hydrocephalus, and significant extra-cranial CSF production. The grading of ventricular reflux of tracer shows promise as a clinical useful method to assess CSF flow pattern disturbances in patients.Graphic abstract
Highlights
Over the last few years, the impact of cerebrospinal fluid (CSF) homeostasis for brain function has gained renewed interest, not least facilitated by the description of theEide et al Fluids Barriers central nervous system (CNS) (2021) 18:16Recently, several reviews have addressed the lack of consensus regarding magnitude and direction of CSF flow in man [4, 6,7,8,9]
This study examined patients with different CSF disorders with regard to how CSF tracer moves from the subarachnoid space into cerebral ventricles, and the direction and magnitude of CSF flow in the cerebral aqueduct and at the cranio-cervical junction
Twenty-four individuals were categorized as reference (REF) patients where no apparent CSF disturbance was eventually diagnosed, and 70 patients with CSF disorders, including idiopathic normal pressure hydrocephalus, communicating hydrocephalus, spontaneous intracranial hypotension (SIH, n = 8), arachnoid cyst (AC, n = 7), pineal cyst (PC, n = 11) and idiopathic intracranial hypertension (IIH, n = 3; Table 1)
Summary
Over the last few years, the impact of cerebrospinal fluid (CSF) homeostasis for brain function has gained renewed interest, not least facilitated by the description of theEide et al Fluids Barriers CNS (2021) 18:16Recently, several reviews have addressed the lack of consensus regarding magnitude and direction of CSF flow in man [4, 6,7,8,9]. A traditional concept of CSF circulation was coined by Harvey Cushing in 1925 as “The third circulation” (first referring to blood and second to lymphatic circulation) [10] According to this view, CSF is thought to be mainly produced by the choroid plexus and circulate from the lateral and third ventricles to the fourth ventricle and further to the surface of the brain with efflux to venous blood via arachnoid granulations. Several central nervous system diseases are associated with disturbed cerebrospinal fluid (CSF) flow patterns and have typically been characterized in vivo by phase-contrast magnetic resonance imaging (MRI). This technique is, limited by its applicability in space and time. Phase-contrast MRI has yet to be compared directly with CSF tracer enhanced imaging, which can be considered gold standard for assessing long-term CSF flow dynamics within the intracranial compartment
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