title: The dilemma of complicated shunt valves: How to identify patients with posthemorrhagic hydrocephalus after aneurysmatic subarachnoid hemorrhage who will benefit from a simple valve?
abstract: BACKGROUND
  Sophisticated shunt valves provide the possibility of pressure adjustment and antisiphon control but have a higher probability of valve dysfunction especially in a posthemorrhagic setting. The aim of the present study is to analyze the clinical outcome of patients with shunt dependent posthemorrhagic hydrocephalus after aneurysmatic subarachnoid hemorrhage (SAH) in order to identify patients who would benefit from a simple differential pressure valve.
  
  
  METHODS
  From 2000 to 2013, 547 patients with aneurysmatic SAH were treated at our institution, 114 underwent ventricular shunt placement (21.1%). 47 patients with available pre- and post-operative computed tomography scans, and an available follow-up of minimum 6 months were included. In order to measure the survival time which a nonprogrammable differential pressure valve would have had in an individual patient we defined the initial equalized shunt survival time (IESS). IESS is the time until surgical revisions of fixed differential pressure or flow-regulated valves for the treatment of over- or under-drainage as well as re-programming of adjustable valves due to over- or under-drainage.
  
  
  RESULTS
  Twenty patients were treated with fixed differential pressure valves, 15 patients were treated with flow-regulated valves, and 12 underwent ventriculoperitoneal (VP) shunt placement with differential pressure valves assisted by a gravitational unit. Patients who reacted with remarkable changes of the ventricular width after the insertion of external ventricular drainage (EVD), before shunt placement, showed a significantly longer IESS.
  
  
  CONCLUSIONS
  Decline of the ventricular width after EVD placement was a predictor for successful VP shunt therapy in the later course of disease. Possibly, this could allow identifying patients who benefit from a simple differential pressure valve or a flow-regulated valve, and thus could possibly avoid valve-associated complications of a programmable valve in the later course of disease.
authors.affiliation: Department of Neurosurgery, Neurovascular Centre, Unfallkrankenhaus Berlin, Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: von der Brelie
authors.affiliation: Department of Neurosurgery, Neurovascular Centre, Unfallkrankenhaus Berlin, Berlin, Germany.
authors.forename: Ullrich
authors.initials: U
authors.lastname: Meier
authors.affiliation: Department of Neurosurgery, Neurovascular Centre, Unfallkrankenhaus Berlin, Berlin, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gräwe
authors.affiliation: Department of Neurosurgery, Neurovascular Centre, Unfallkrankenhaus Berlin, Berlin, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Lemcke
keywords: Gravitational unit; outcome; posthemorrhagic hydrocephalus; subarachnoid hemorrhage; valve settings