title: Beneficial effect of siphoning in treatment of adult hydrocephalus.
abstract: OBJECTIVE
  To increase awareness about the treatment of adult patients with shunt-nonresponsive hydrocephalus--a state characterized by marked ventriculomegaly, low intracranial pressure, and a patent cerebrospinal fluid diversionary shunt.
  
  
  METHODS
  Retrospective analysis of hospital and outpatient records.
  
  
  METHODS
  Four patients with symptomatic ventriculomegaly and patent ventriculoperitoneal shunts treated with a protocol of progressive ventricular hypotension induced by external cerebrospinal fluid drainage.
  
  
  RESULTS
  Severe clinical manifestations exhibited by the patients, including parkinsonian features, Parinaud syndrome, and extensor posturing, completely reversed once a normalization of ventricular size was achieved. External ventricular drainage pressures as low as -30 cm H2O were required to reduce ventricular size. All patients finally received a shunt incorporating a standard medium differential pressure valve with no antisiphon device.
  
  
  CONCLUSIONS
  Shunt siphoning may be an essential mechanism by which cerebrospinal fluid shunting is effective in many patients with adult hydrocephalus. Cerebrospinal fluid shunts that contain an antisiphon device are ineffective in these patients, despite the attainment of "physiologic" intracranial pressures. Based on reported experimental and clinical evidence, it seems that the cause of this condition may be related to abnormally high intracranial compliance.
authors.affiliation: Division of Neurosurgery, Brain Research Institute, University of California at Los Angeles School of Medicine, 90095-7039, USA. mbergsneider@mednet.ucla.edu
authors.forename: M
authors.initials: M
authors.lastname: Bergsneider
authors.forename: W J
authors.initials: WJ
authors.lastname: Peacock
authors.forename: J C
authors.initials: JC
authors.lastname: Mazziotta
authors.forename: D P
authors.initials: DP
authors.lastname: Becker
mesh_terms: D000328:Adult; D000368:Aged; D002552:Cerebral Ventricles / Q000473:pathology; D014695:Cerebral Ventriculography; D004322:Drainage; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006849:Hydrocephalus / Q000150:complications / Q000601:surgery* / Q000628:therapy*; D007427:Intracranial Pressure; D008297:Male; D008875:Middle Aged; D010302:Parkinson Disease, Secondary / Q000209:etiology; D011183:Postoperative Complications; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D017211:Treatment Failure; D017287:Ventriculoperitoneal Shunt