Estimation of cerebrospinal fluid pressure via lumbar epidural space by equilibration method.

By introducing water into the lumbar epidural space from a vertically held tube under gravity, we measured lumbar epidural pressure (EDP) when the water meniscus no longer declined. In principle, the pressure of either side of dura mater had become equal at this time which is referred to as the equilibrium point. EDP measured in this way was consistently 1-3 mmHg lower than lumbar cerebrospinal fluid pressure (CSFP) not only immediately after the equilibrium point, but also for 5 min after the equilibrium point had been reached. Both EDP and CSFP responded sensitively to the manipulations of CSFP during this period. We suggest that this method may provide a means to continuously monitor CSFP by EDP.