Effect of intracranial pressure on cerebrospinal fluid formation in isolated brain ventricles

The effect of intracranial pressure on cerebrospinal fluid formation has been studied in cats by ventricular perfusion with the aqueduct of Sylvius blocked (isolated ventricular perfusion). It has been found that intracranial pressure has a considerable effect on the rate of cerebrospinal fluid formation, while increases in pressure cause a significant and prolonged decrease in cerebrospinal fluid formation. The effect was observed in animals whether they were initially perfused under lower or under higher intracranial pressure. Cerebrospinal fluid absorption has been studied under the above conditions and it has been noted that the ventricles are capable of significant cerebrospinal fluid absorption, since in isolated ventricles cerebrospinal fluid formation and absorption were in balance at physiological intracranial pressure. In addition, cerebrospinal fluid formation rate within the isolated brain ventricles has been compared with the formation rate in the whole cerebrospinal fluid system. Since only about 30% of the total cerebrospinal fluid formation was observed by isolated ventricular perfusion, it seems that the brain ventricles are not the exclusive site of cerebrospinal fluid formation.