Evidence of nonlinear response of hydrocephalus shunt valves to pulsating flow

We found that shunt valves used in regulating the cerebrospinal fluid flow (CSF) of the hydrocephalus patients alter the characteristics of the input waveform under AC flow; we tested Codman Hakim and Medtronic Strata programmable valves. We found that these two valves alter the characteristics of the fluid waveform; there is a change in the amplitude, phase and form. We are still investigating how the response of the shunt valves to AC signals similar to those present in the brain could contribute or lead to some of the complications observed in patients.