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Investigation: visual inspection: during the investigation, deposits/ tissue residues on the device were determined.No damages or other abnormalities.Permeability test: a permeability test has shown that both valves are permeable.Computer controlled test: to investigate the claim of under-drainage, the opening pressure is measured using a miethke computer controlled testing apparatus which simulates a cerebrospinal fluid flow.The valves are tested in both the horizontal as well as the vertical position.The results show that the valves do not operate within the permissible tolerance in their respective relevant position.An accelerated outflow of both valves was determined.Adjustment test: the valves were tested and both valves are not adjustable in all pressure settings.Braking force and brake function test: the brake functionality test has shown that the brake function operates as expected.However, the braking force cannot be measured due to the non-adjustability of the valves.Internal inspection : after dismantling of the valves, organic deposits were found in both valves.Results: based on our investigation results, we can determine an accelerated outflow and adjustment difficulties of both valves.The determined organic deposits can be named as the cause for the functional deviations.Organic matter in the cerebrospinal fluid can influence the function temporarily and are known inherent side effects in hydrocephalus therapy.
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