title: In vivo assessment of hydrocephalus shunt.
abstract: OBJECTIVE
  Over a 3-year period, we have performed 312 tests in 197 shunted patients. The data have been analyzed retrospectively to: (1) investigate the parameters describing CSF dynamics that correlate with shunt under-drainage and (2) estimate accuracy of this method.
  
  
  METHODS
  Constant rate infusion tests into shunt prechamber were performed.
  
  
  RESULTS
  In 161 of the 312 infusion tests, results indicated under-draining shunts. Patients in the under-draining group had higher baseline and plateau CSF pressures, higher resistance to CSF outflow and higher levels of baseline pulse amplitude waveform. During the test, a significantly greater vasogenic waves and lower compensatory reserve was noticed in patients with blocked shunts. In 21 patients with suggestion of shunt blockage and who subsequently underwent operative revision of the shunt, reports of intraoperative shunt patency were available. Shunt blockage was confirmed intra-operatively during surgery in 19 cases.
  
  
  CONCLUSIONS
  In vivo shunt testing is easy, safe and clinically useful, aiding decision in difficult clinical situations, where shunt malfunction is suspected but not certain. It also has satisfactory positive predictive power.
authors.affiliation: Academic Neurosurgical Unit, Addenbrooke's Hospital, Cambridge, UK. Gianpaolo_p@hotmail.com
authors.forename: G
authors.initials: G
authors.lastname: Petrella
authors.forename: M
authors.initials: M
authors.lastname: Czosnyka
authors.forename: P
authors.initials: P
authors.lastname: Smielewski
authors.forename: D
authors.initials: D
authors.lastname: Allin
authors.forename: E P
authors.initials: EP
authors.lastname: Guazzo
authors.forename: J D
authors.initials: JD
authors.lastname: Pickard
authors.forename: Z H
authors.initials: ZH
authors.lastname: Czosnyka
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015170:Cerebrospinal Fluid Pressure; D002557:Cerebrospinal Fluid Shunts; D002648:Child; D002675:Child, Preschool; D004868:Equipment Failure; D005260:Female; D006801:Humans; D006849:Hydrocephalus / Q000601:surgery*; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D011237:Predictive Value of Tests; D012737:Sex Factors; D012815:Signal Processing, Computer-Assisted; D016896:Treatment Outcome