Testing of cerebrospinal fluid shunt systems under dynamic flow conditions.

There exists considerable disagreement regarding the experimental methods that are used to evaluate cerebrospinal fluid (CSF) shunts. Nearly everyone who has studied CSF shunts has attempted to define shunt characteristics by either steady pressure or steady flow-rate tests of only the valve component of the shunt. However, a valved shunt assembly must actually function in a very dynamic environment. A series of bench tests have been designed to determine the dynamic characteristics of complete shunt systems. Thirty CSF shunt assemblies, consisting of six assemblies from five different manufacturers, have been tested. The tests show that the response times for CSF shunts vary from 0.17 min to 0.46 min, and that the mean pressure maintained in a dynamic flow environment may be very different from the pressure maintained under steady flow conditions.