Ventriculocisternal Perfusion Studies in the Monkey. III. Sources of Error in Measuring Cerebrospinal Fluid Formation,
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
Pagination or Media Count:
Ventriculocisternal perfusion is regarded as a precise method of measuring the rate of formation of cerebrospinal fluid CSF but possesses inherent potential sources of error not commonly appreciated. Using the technique to measure CSF formation rate in the rhesus monkey, rate changes were observed when none was expected. Most puzzling has been the steady decline of CSF formation rate at 4 percent each hour during the final 5 hours of a 7-hour perfusion although variables known to affect CSF formation remained stable. In addition, artifactitious alterations in rate were observed in experiments in which craniospinal blood volume was changed by sudden changes of either PCO2 or central venous pressure. Mobilization of sequestration of incompletely equilibrated CSF is believed responsible. In other experiments, a small increase of intracranial pressure produced by increasing outflow resistance was quickly followed by an apparent reduction of CSF formation. Here we speculate that when intracranial pressure is increased above normal, some newly formed CSF may be diverted to drainage channels before it can mix with perfusion fluid. We have concluded that to assess accurately the effect of a variable on the rate of CSF formation, one must control perfusion time and craniospinal blood volume as well as intracranial pressure. Knowledge of the normal rate of formation of CSF is necessary before this model can be used to study relation of CSF dynamics to central nervous system trauma and disease.
- Anatomy and Physiology