Is posture-related craniospinal compliance shift caused by jugular vein collapse? A theoretical analysis

Abstract

BackgroundPostural changes are related to changes in cerebrospinal fluid (CSF) dynamics. While sitting up leads to a decrease in cranial CSF pressure, it also causes shifts in the craniospinal CSF volume and compliance distribution. We hypothesized that jugular vein collapse in upright posture is a major contributor to these shifts in CSF volume and compliance.MethodsTo test this hypothesis, we implemented a mathematical lumped-parameter model of the CSF system and the relevant parts of the cardiovascular system. In this model, the CSF and the venous system are each divided into a cranial and a spinal part. The pressures in these cranial and spinal portions differ by the posture-dependent hydrostatic pressure columns in the connecting vessels. Jugular collapse is represented by a reduction of the hydrostatic pressure difference between cranial and spinal veins. The CSF pressure–volume relationship is implemented as a function of the local CSF to venous pressure gradient. This implies that an increase in CSF volume leads to a simultaneous displacement of blood from adjacent veins. CSF pulsations driven by the cardiovascular system are introduced through a pulsating cranial arterial volume.ResultsIn upright posture, the implemented CSF pressure–volume relationship shifts to lower cranial CSF pressures compared to the horizontal position, leading to a decrease in cranial CSF pressure when sitting up. Concurrently, the compliance of the spinal compartment decreases while the one of the cranial compartment increases. With this, in upright posture only 10% of the CSF system’s compliance is provided by the spinal compartment compared to 35% in horizontal posture. This reduction in spinal compliance is accompanied by a caudal shift of CSF volume. Also, the ability of the spinal CSF compartment to compensate for cerebral arterial volume pulsations reduces in upright posture, which in turn reduces the calculated craniospinal CSF flow pulsations.ConclusionThe mathematical model enabled us to isolate the effect of jugular collapse and quantify the induced shifts of compliance and CSF volume. The good concordance of the modelled changes with clinically observed values indicates that jugular collapse can be considered a major contributor to CSF dynamics in upright posture.

Noninvasive assessment of intracranial elastance and pressure in spontaneous intracranial hypotension by MRI

“…It is also worth mentioning that SIH patients with EVD showed significantly larger decreases in IJVF ratio compared with those without EVD. This phenomenon closely resembles the posture‐related changes of intracranial hemodynamics . As reported in an MRI intracranial physiological study, a collapsed IJV and diversion of venous drainage into the epidural, vertebral, and other deep cerebral or cervical veins were observed in the upright position, while venous outflow presented predominantly through the IJV while supine .…”

“…This phenomenon closely resembles the posture-related changes of intracranial hemodynamics. 37 As reported in an MRI intracranial physiological study, a collapsed IJV and diversion of venous drainage into the epidural, vertebral, and other deep cerebral or cervical veins were observed in the upright position, while venous outflow presented predominantly through the IJV while supine. 38 Hence, the lower IJVF ratio is likely an important sign of intense compensation for intracranial hypotension in SIH patients with EVD, who had higher IE than the normal subjects and SIH group without EVD.…”

Comparing invasive with MRI‐derived intracranial pressure measurements in healthy elderly and brain trauma cases: A pilot study

“…In general, spinal compliance is the dominant contributor to the craniospinal compliance because the dura is less confined by the vertebra in the lower region of the spine (lumbar region) compared with the cranium and upper cervical regions. This finding, however, is not consistent with several other studies stating that the cranial vault is the dominant source of craniospinal compliance (almost two‐thirds) …”

“…This finding, however, is not consistent with several other studies stating that the cranial vault is the dominant source of craniospinal compliance (almost two-thirds). 2,28,29 The significant correlations of cranial and spinal compliance contribution with MR-ICP and LPOP respectively support our hypothesis that the craniospinal compliance distribution plays a major role in modulating the ICP. A cranium with higher compliance reserve can accommodate a larger capacity of fluid inside it without an appreciable increase in ICP.…”

Human jugular vein collapse in the upright posture: implications for postural intracranial pressure regulation

“…Furthermore, a recent theoretical analysis of CSF compliance has also indicated that IJV collapse likely plays an important role in the CSF dynamics in the upright human [11]. However, neither of these studies investigated how the suggested neck-level pressure reference point is formed and upheld by the well-known jugular venous collapse.…”