Blood storage within the intracranial space and its impact on cerebrospinal fluid dynamics
Clive B Beggs 1
, Simon J Shepherd 1
, Pietro Cecconi 2
and Maria Marcella Lagana 2
1. Medical Biophysics Laboratory, University of Bradford, Bradford, BD7 1DP, UK
2. Fondazione Don Carlo Gnocchi ONLUS, IRCCS S. Maria Nascente. Milan, Italy
Background: The volumetric changes that occur throughout the cardiac cycle (CC) in the various
intracranial vascular compartments are poorly understood. Although blood entering/leaving the
cranium is pulsatile, flow in the cerebral vascular bed is non-pulsatile , implying the transient
storage of blood.
Objective: To characterise the temporal changes in fluid volume that occur within the cranium
throughout the CC.
Methods: Neck MRI data were acquired from 14 healthy adults (age <35), using a 1.5 Tesla
scanner. Arterial, venous and cerebrospinal fluid (CSF) flow rate data acquired at the C2/C3 level
were standardized to 32 points over the CC. The relative changes in the intracranial arterial, venous
and CSF volumes were calculated by: (i) integrating the respective flow rate signals to compute the
instantaneous volumetric changes (ivc); (ii) mean centering the respective ivc signals; and (iii)
cumulating the mean centered ivc signals to yield the fluid volumetric changes in the cranium
throughout the CC.
Results: The aggregated flow rate signals for all subjects are shown in Figure 1, while Figure 2
shows the relative changes in the intracranial arterial, venous and CSF volumes. A strong inverse
relationship exists between the arterial and venous volumetric signals (r = -0.844, p<0.001). As the
intracranial arterial blood volume decreases to a minimum during diastole, so blood is stored in the
intracranial venous compartments. This coincides with the period when the intracranial CSF volume
increases. Only when the intracranial CSF volume peaks and starts to decrease, is the venous blood
stored in the cranium allowed to discharge.
Conclusions: The behavior of the venous pulse is controlled by volumetric changes within the
cranium in a process that is mediated by the CSF. This finding supports the hypothesis that CSF
interacts with the cortical bridging veins to facilitate the storage of venous blood during diastole
Figure 1. Aggregated fluid flow rates. Figure 2. Relative intracranial fluid volumes.
References:  Bateman GA. Neuroradiology 2002, 44:740–748;  Luce JM, et al. J Ap
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