Fig. 1
From: Interactions of brain, blood, and CSF: a novel mathematical model of cerebral edema
A Structural model of the intracranial space with four compartments: the subarachnoid space enveloped inwardly by the pia and outwardly by the dura, the brain enveloped by the pia, the ventricles, and the cerebrovascular circulation. The intracranial subarachnoid space is in continuity with the spinal subarachnoid space. CSF is produced by the choroid plexus (QCSF) and flows through the ventricles and into the subarachnoid space until its absorption into the superior sagittal sinus (SSS) via the arachnoid granulations. The cerebral interstitial fluid (QISF) flows through the extracellular space and into the subarachnoid space where it joins CSF flow. Cerebral intracellular edema causes a reduction of the extracellular space volume with a concomitant increase in resistance to the flow of cerebral interstitial fluid. When blood–brain barrier (BBB) disruption associated with brain injury occurs, fluid may enter the brain from the capillaries through the disrupted BBB (QBBB) leading to cerebral edema. B An electrical analogue model demonstrating flow, resistances, and compliances, within the compartments depicted in the structural model. Flow of cerebral ISF (QISF) and CSF (QCSF) is depicted in green, while the cerebral vascular circulation is depicted in red. The intracranial compartments are represented by the capacitors CBR (orange), CVEN (green), and CSAS (purple) for brain, ventricles, and subarachnoid space, respectively. The cerebrovascular compartment is represented by the capacitors (red) CA, CC, and CV, representing the arterial-arteriolar, capillary and venous compartments, respectively. The spinal subarachnoid space is represented by CSPI. Resistance to bulk flow of cerebral interstitial fluid is represented by RBF, resistance to CSF flow in the ventricles by RVEN, resistance to CSF outflow by absorption into the superior sagittal sinus (blue) is represented by ROUT. Resistance to flow of CSF from the intracranial subarachnoid space through the foramen magnum into the spinal subarachnoid space is represented as RFM. Resistance to flow in the cerebrovascular system is represented by RA, RC, RV, and RBV, which denote resistance of arterioles, capillaries, veins, and bridging veins, respectively. Resistance to movement of fluid across the BBB, which is very high under normal conditions but may be impaired with brain injury is represented by RBBB. Pressure in the intracranial compartments include ventricular pressure, (ICPVEN), brain intraparenchymal pressure (ICPBR), and subarachnoid space pressure (ICPSAS), while those in the cerebrovascular compartment include systemic arterial pressure (PA), arteriolar pressure (PARL), capillary pressure (PC), and venous pressure (PV). Pressure in the superior sagittal sinus is depicted by PSSS