The procedure entails the insertion of a catheter into both the ventricular system and the peritoneal cavity, connected to a programmable valve that regulates cerebrospinal fluid flow. The choice of programmable valve (Codman Hakim or Codman Certas Programmable Valves, Integra, Plainsboro, USA; Strata valve, Medtronic, Minneapolis, USA; Sophysa, Orsay, France; Miethke proGAV, Aesculap, Tuttlingen, Germany) is at the surgeon's discretion. The preoperative valve setting is preset to a pressure level between 85 - 135 mmH2O. The VPS procedure is conducted under general anesthesia and typically lasts approximately 90-120 minutes.

The modified Rankin Scale (mRS) is used to assess the degree of disability and dependency in everyday life. Th mRS is a standard tool to assess the neurological outcome in trials with acute severe brain disease. The mRS ranges from 0 (no disability) to 6 (death). Lower values indicate less disability.

The Montreal Cognitive Assessment (MoCA) is used to evaluate cognitive function and detect mild cognitive impairment. It scores between 0 and 30, with higher scores indicating better cognitive performance. A score of 26 or above is generally considered normal.

To assess the gait and balance, a 10-metre GaitRite walkway, specifically designed to measure and analyze gait patterns, is performed. The body's movement are recorded using the the Ambulatory Parkinson's Disease Monitoring (APDM) Mobility Lab System.

To assess the gait and balance, the Timed-Up-and-Go Test is performed. This is a simple and quick assessment to measure the time taken for an individual to stand up from a chair, walk three meters, turn around, walk back to the chair, and sit down again, with shorter times indicating better mobility.

To assess the gait and balance, the modified Clinical Test of Sensory Interaction on Balance (mCTSIB, 30 seconds) is performed. The mCTSIB measures a person's ability to maintain stability in different sensory conditions for 30 seconds each.

To assess the gait and balance, the modified Balance Error Scoring System (mBESS) is performed. The mBESS involves performing three standing balance tasks (double-leg stance, single-leg stance, and tandem stance) on both firm and foam surfaces, with errors recorded to gauge balance performance.

To assess the gait and balance, the 5-times-sit-to-stand test is performed. It involves timing how long it takes a person to rise from a seated position to a standing position five times as quickly as possible.

To assess the gait and balance, the hand grip strength test is performed. It assesses the maximum isometric strength of the hand and forearm muscles and involves using a dynamometer to measure the force exerted when a person squeezes the device with their hand.

As a neuropsychological assessment the Montreal Cognitive Assessment is performed to evaluate cognitive function and detect mild cognitive impairment. It assesses various cognitive domains, including memory, attention, language, and executive functions, with a maximum score of 30 points; higher scores indicate better cognitive function.

As a neuropsychological assessment the TAP Test (Test of Attentional Performance) is a computer-based assessment used to evaluate different aspects of attention, such as alertness, divided attention, and sustained attention. It measures reaction times and accuracy across various tasks designed to assess cognitive functions related to attentional control and processing speed.

As a neuropsychological assessment the Trail Making Test is performed to evaluate cognitive flexibility, visual attention, and task-switching abilities. It consists of two parts: Part A involves connecting numbered circles sequentially, while Part B requires alternating between numbers and letters in ascending order. The test measures executive functioning and processing speed, with longer completion times indicating potential cognitive impairment.

As a neuropsychological assessment the Stroop-Test is performed to measure selective attention, cognitive flexibility, and processing speed. It typically involves presenting color names (e.g., "red," "blue") printed in incongruent colored ink (e.g., the word "red" printed in blue ink), and participants are required to name the ink color while ignoring the word. The test assesses the ability to inhibit automatic responses and is sensitive to cognitive impairments, with longer response times or increased errors indicating potential difficulties in executive functioning.

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word List is used as a neuropsychological assessment to evaluate verbal memory. It consists of a list of 10 common words that the participant is asked to recall immediately after hearing them. This test assesses the ability to remember and retrieve information shortly after it was presented, providing insights into memory function and potential cognitive impairments.

The CERAD Constructive Praxis is used as a neuropsychological assessment to assess visuospatial and constructional abilities by asking participants to copy a series of geometric figures. This test helps evaluate visual perception, spatial orientation, and motor skills, providing insights into cognitive functioning.

As a neuropsychological assessment the Boston Naming Test is performed. It assesses the ability to name objects or pictures presented by the examiner, evaluating language and semantic memory functions.

As a neuropsychological assessment the Rey-Osterrieth Complex Figure Test is performed. It assesses visuospatial and constructional abilities as well as visual memory. It involves copying a complex figure and then recalling and reproducing it from memory.

The Beck Depression Inventory (BDI) is used to assess the intensity of depression. The BDI is a self-report questionnaire designed to assess the severity of depressive symptoms. It consists of 21 multiple-choice questions, each related to a specific symptom of depression such as sadness, pessimism, guilt, and fatigue. Scores on the BDI can range from 0 to 63, with higher scores indicating more severe depressive symptoms.

In a radiological assessment the flow-void presence is determined.

In a radiological assessment the ventricular volumetry is measured.

In a radiological assessment periventricular perfusion measurements are carried out.

In a radiological assessment the idiopathic normal pressure hydrocephalus (iNPH) radiological scale is assessed. Scores typically range from 0 to 12, with higher scores indicating greater severity of radiological findings suggestive of iNPH, such as enlarged ventricles, narrow sulci, and periventricular white matter changes.

iNPH severity is measured using the Hellström score, which ranges from 0 to 12, with higher scores indicating more severe symptoms across domains of gait, balance, and cognitive impairment.

The quality of life is assessed using the 15D health-related quality of life (HRQoL) patient-reported questionnaire. It cover aspects like physical functioning, emotional well-being, social functioning, and pain. Scores can range from 0 to 100, with higher scores reflecting better perceived health and functioning across various domains, while lower scores suggest greater impairment and reduced quality of life.

During hospitalization, 6-8 weeks, as well as 6- and 12-month follow-up, the incidence of complications is assessed. Complications are defined as infections, bleeding, shunt dysfunction (e.g., due to misplacement, obstruction of the proximal ventricular catheter, dysfunction of the valve, dysfunction of the peritoneal catheter), ETV occlusions (requiring re-ETV or VPS insertion), and neuronal tissue injury (e.g., fornix injury).

during hospitalization, 6-8 weeks, as well as 6- and 12-month follow-up, the incidence and reason of revision surgery is assessed.

The mortality is assessed during hospitalization and the 12-month follow-up