Validation of models of venous outflow from the cranial cavity in the supine and upright body positions

Introduction
This in silico study was aimed at building reliable models comprising both the jugular and vertebral outflow pathways from the cranial cavity. Such models could be useful in further research on understanding the relevance of stenoses of the internal jugular vein.

Material and methods
Flowsquare+ computational flow mechanics software was used. Models of cerebral venous outflow comprised an initial inflow field representing cerebral circulation, which branched into 2 alternative outflow routes: a tube representing the internal jugular vein, and an irregular network representing the vertebral veins and epidural venous plexus. Then these 2 alternative pathways joined again together to form the outflow field.

Results
In the model representing open internal jugular vein, most (84%) of the blood flowed out through this vein. The remaining 16% utilized the vertebral pathway, which is in line with observations in living subjects. In this model the total flow volume in outflow field was 399 ml/min, which was also in line with observations in humans. When the modelled internal jugular vein was collapsed, which in living humans is seen in the upright body position, in order to get proper values of the total flow it was necessary to increase the value of flow velocity in the initial field. In such a model the total flow was similar to the former one, but the jugular pathway was responsible for only 36% of the total flow.

Conclusions
Models comprising jugular and vertebral outflow pathways have been validated and could be used in future in silico investigations of extracranial disturbances of the cerebral venous outflow.