Pressure changes observed in Codman-Medos programmable valves following magnetic exposure and filliping

Objects: We wished to find what pressure changes were caused in Codman-Medo s programmable valve by magnetic exposure and filliping. This pressure-adju stable valve system was used in an experimental investigation of the change s measured in the pressure setting following MR exposure and other impulses . Methods: In one experiment, two valves were affixed to a human model: one was installed in the right retroauricular region and the other at the ante rior chest wall. The pressure was changed in 58 (80.6%) of 72 tests in the valve in the right retroauricular region and in 46 (63.9%) of 72 tests in t he valve at the anterior chest wall. In some tests with the valve pressure originally set at 200 mmH(2)O striking changes to lower pressures were obse rved. In the other experiment, the changes of pressure settings in seven pa tients with a shunt system installed were checked before and after random f illiping with the tip of an index finger 50 times. In all 7 patients, the p ressures initially set were greatly changed, by up to 120 mmH(2)O of the ma ximum range. Conclusions: These results demonstrate that the pressure setti ng of the shunt system can be changed by various shocks, including magnetic impulses, and that the pressure level of the shunt system must be constant ly monitored.