The investigation of cerebrospinal fluid formation by ventriculo-aqueductal perfusion method in cats.

OBJECTIVES

The perfusion of cerebrospinal fluid (CSF) spaces by artificial CSF (aCSF) containing an indicator, is an indirect method used to calculate CSF formation. To evaluate this method, we have developed a ventriculo-aqueductal perfusion method, which enables a direct measurement of CSF formation in the ventricles.

METHODS

In chloralose anaesthetized cats, the aqueduct of Sylvius was cannulated so that the outflow end of the plastic cannula was positioned extracranially. Both lateral ventricles were also cannulated, with one cannula for infusion of aCSF containing blue dextrane and the other for measurement of CSF pressure.

RESULTS

During ventriculo-aqueductal perfusion (direct method) under physiological CSF pressure, the outflow rate from aqueductal cannula did not differ significantly from the inflow rate, i.e. no CSF formation was observed. When the indirect method based on dilution of blue dextran in the outflowing perfusate was used, the formation of approximately 5 microl/min of CSF was obtained.

CONCLUSION

Results of the direct method indicate that net CSF formation inside brain ventricles does not exist. The opposite results obtained by the indirect method questions this method as a reliable study of CSF formation.