PUMP study: reservoir pumping in suspected underdrained shunted patients with normal pressure hydrocephalus - a prospective single-center study.

BACKGROUND: Suboptimal improvement or secondary deterioration is frequently observed in patients with shunted normal pressure hydrocephalus (NPH). The non-invasive tap test ("pumping-test") performed via the flushing reservoir of shunts may represent an alternative to invasive diagnostic procedures for detecting underdrainage. The aim of this study was to demonstrate its efficacy and potential to reduce the need for invasive diagnostic tests. METHODS: A prospective study was conducted on 25 NPH patients who had been shunted with a "Sprung-Reservoir" and a proGAV 2.0 and in whom underdrainage was suspected. By performing 100 pumps, approximately 20 ml of cerebrospinal fluid (CSF) was withdrawn from the ventricles. Immediate effects were assessed through gait examinations after 10 min, and changes over one week were evaluated using observation sheets completed by patients and/or caregivers. Based on the results and subsequent clinical decisions, the extent to which invasive tests could be avoided was determined. RESULTS: The test was feasible in all patients. It was well tolerated, with no side effects or discomfort in 21 patients. Temporary headaches occurred in 1 patient, and dizziness lasting less than 5 min was reported in 3 patients. Improvement after 10 min was observed in 11 patients; in 8 of these cases, the shunt valve was immediately downregulated. The remaining 17 patients were provided with observation sheets: 6 showed no improvement, 7 reported temporary improvement, and 4 experienced sustained improvement. Patients with temporary improvement were offered valve downregulation, while those with sustained improvement were advised to return only if new symptoms developed. Patients with no improvement were put to further follow-up and possibly offered invasive tests for further clarification. Consequently, the pumping test enabled avoidance of invasive testing in 19 cases (76%). CONCLUSION: The pumping test proved to be safe, effective, and capable of providing rapid clinical feedback. The additional use of observation sheets supports the monitoring of delayed effects. More invasive and costly tests can often be avoided-76% in this study. This non-invasive tap test should be considered a first-line diagnostic procedure in cases of suspected underdrainage, at least in NPH patients, before pursuing invasive diagnostics. However, not all flushing reservoirs are suitable for this "pumping test."