title: Hydrostatic and hydrodynamic considerations in shunted normal pressure hydrocephalus.
abstract: Symptoms of overdrainage, a frequent complication following shunting procedures especially in patients with normal-pressure hydrocephalus (NPH), are presumed to be caused by siphoning: gravity-enhanced flow of cerebro spinal fluid (CSF) through shunts in upright position. A critical reappraisal of siphoning and overdrainage (OD) is presented considering the occurrence of subdural hygromas (SDH) encountered in a group of patients shunted for NPH. The patients participated in the multicentre Dutch NPH study: 101 NPH patients were randomised for treatment with shunts with low or medium-high working pressure. Treatment with shunts with low working pressure resulted in an increased incidence of SDH (iSDH). Current physiological concepts of overdrainage are discussed and criticised. A new theory is presented on the basis of general physiological considerations. The theoretical model proposed yields a revised explanation for the origin of extremely low ventricular pressure in the upright position found with overdrainage. The efficacy of siphoning-preventing shunts and subtemporal decompression is explored in the light of the proposed theory.
authors.affiliation: Department of Neurosurgery, Rotterdam University Hospital, The Netherlands.
authors.forename: D A
authors.initials: DA
authors.lastname: de Jong
authors.forename: E J
authors.initials: EJ
authors.lastname: Delwel
authors.forename: C J
authors.initials: CJ
authors.lastname: Avezaat
mesh_terms: D002555:Cerebrospinal Fluid / Q000502:physiology; D015170:Cerebrospinal Fluid Pressure / Q000502:physiology*; D005500:Follow-Up Studies; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000503:physiopathology / Q000601:surgery*; D009426:Netherlands; D011183:Postoperative Complications / Q000503:physiopathology*; D011187:Posture / Q000502:physiology; D013353:Subdural Effusion / Q000503:physiopathology; D017287:Ventriculoperitoneal Shunt / Q000295:instrumentation*