Fig. 1

Schematic illustration of the Monro-Kellie doctrine. The Monro-Kellie doctrine describes the dynamic relationship between the intracranial cerebrospinal fluid (CSF), blood, and brain volumes to maintain intracranial pressure. The left panel displays the CSF displacement invoked by an increased cerebral blood volume during hypercapnia. As well, flow in the superior sagittal sinus is shown. Here, CSF is absorbed through the subarachnoid villi. The middle panel is an illustration of the intracranial compartment during normoxic normocapnia. The right panel shows the intracranial volume during hypercapnia, when blood volume increases and CSF volume decreases