title: Gravity assisted vs. medium pressure valves for communicating hydrocephalus show similar valve-revision rates.
abstract: BACKGROUND
  Two common valve types used to treat hydrocephalus include gravity assisted valves (GAV) and medium pressure valves (MPV). Despite their different mechanism of action, differentiated surgical indications per type are not well defined. One could assume that due to a higher complexity of the GAV system, it may be more prone to valve-related malfunction. The purpose of this retrospective study was to compare the valve-related complication rates of GAV and MPV in patients with communicating hydrocephalus.
  
  
  METHODS
  Patients aged 16 years or older undergoing their first shunt implantation using GAV or MPV were included. We recorded demographic data, implantation diagnosis, outcome, complications, valve type and valve adjustments. Symptoms were documented at discharge and follow-up. Valve-related malfunctions were distinguished from other shunt complications.
  
  
  RESULTS
  N = 252 patients (range 16.6-88.4, mean 65.0 years, 116 male and 136 female) underwent shunt placement for the first time. N = 122 GAV (48.4 %) and n = 130 MPV were implanted (51.6 %) over a period of 5 years. The most frequent diagnoses were normal pressure hydrocephalus (NPH) in 86 cases (34.1 %) and posthemorrhagic hydrocephalus in 114 cases (45.2 %). About two thirds of patients were free of hydrocephalus-related symptoms at follow-up. N = 66 subjects (26.2 %) underwent at least one shunt revision. N = 29 revisions (11.5 %) were due to valve-related malfunction. Valve-related revisions were the main cause for revision in 18/37 cases (48.6 %) in the GAV group and in 11/29 (37.9 %) in the MPV group. Neither clinical improvement nor valve-related malfunctions were found to be statistically different among groups.
  
  
  CONCLUSIONS
  Despite their technical differences, GAV and MPV show similar valve-related revision rates in the treatment of communicating hydrocephalus.
authors.affiliation: Department of Neurosurgery, Aarau Hospital, Tellstr. 1, 5000, Aarau, Switzerland, schatlo@gmail.com.
authors.forename: Bawarjan
authors.initials: B
authors.lastname: Schatlo
authors.forename: Motaz
authors.initials: M
authors.lastname: Hamed
authors.forename: Alexander
authors.initials: A
authors.lastname: Grote
authors.forename: Johannes
authors.initials: J
authors.lastname: Schramm
authors.forename: Georg
authors.initials: G
authors.lastname: Neuloh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002557:Cerebrospinal Fluid Shunts / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006112:Gravitation; D006801:Humans; D006849:Hydrocephalus / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000517:prevention & control; D011312:Pressure; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult