It becomes somewhat apparent from this clinical and experimental study that the pathophysiological conditions of hydrocephalus after subarachnoid hemorrhage are not well understood.
1) The main driving force of ventricle dilatation after SAH is increased resistance to the outflow of cerebrospinal fluid (CSF) caused by obstruction of the basal cistern by hemorrhage.
2) Aside from this general pathogenesis, the compliance of the brain itself and its container (skull, dura etc.) exert an influence on ventricle dilatation.
a) There was no relation between ventricle dilatation and the amplitude of PP. This means that increased amplitude of PP was not the cause of ventricle dilatation in this model.
b) Cerebrospinal fluid in the cranial cavity flows in a to and fro manner, responding to pulsations of the brain. An increase in the compliance of the craniospinal cavity after hemicraniectomy promotes an increase in the amplitude of the to and fro flow of the CSF in that side.
c) The evidence presented suggests that a high degree of correlation exists between the amplitude of PP and pressure-volume response (PVR : an indicator of intracranial compliance). This means that PP can be a good parameter of intracranial compliance in this model. However no correlation could be found between the to and fro movement of CSF and intracranial compliance.

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