Cerebrospinal fluid pressure as a function of body position in dogs

Cerebrospinal fluid (CSF) pressure has been measured as a function of body position in dogs under pentobarbital anaesthesia. CSF pressure was higher than superior sagittal sinus pressure by an almost constant 6 cm of water, regardless of position, if 30 min were allowed for the system to reach equilibrium. The sinus pressure was found to depend on simple hydrostatic theory when the sinus was at or below the level of the heart. When the sinus was above the heart, the collapsing nature of the jugular veins prevented the sinus pressure from dropping as low as a simple hydrostatic theory would predict.