title: Radionuclide shunt patency study for evaluation of suspected ventriculoperitoneal shunt malfunction in adults with normal pressure hydrocephalus.
abstract: OBJECTIVE
  Shunt patency studies are performed to determine whether shunt revision surgery is needed in malfunctioned ventriculoperitoneal shunt. The aim of our study was to develop a simple diagnostic algorithm in the diagnostic workup and identify factors associated with improvement after revision surgery.
  
  
  METHODS
  A retrospective review of patients with confirmed shunt obstruction who underwent a revision surgery and were followed for 6 to 12 months was performed. A simpler algorithm to identify shunt obstruction was created and compared with the 4-variable algorithm.
  
  
  RESULTS
  Of the 63 patients in whom shunt obstruction was suspected, 39 were diagnosed with complete or partial obstruction. Thirty-seven patients underwent shunt revision surgery that included removal of shunt (n = 2), conversion to a ventriculoatrial shunt (n = 8), and relocation of the distal end of the catheter into a different part of the peritoneal cavity (n = 27). Improvements were seen in 63.3% (n = 19) of patients evaluated at 6 months and 63.6% (n = 14) of patients evaluated at 12 months. The positive predictive value of the study was 80%. A simpler 1-variable algorithm using T(1/2) (half-time) could correctly classify 86.9% of patients with shunt obstruction, compared with a 4-variable algorithm that correctly classified 80% of patients.
  
  
  CONCLUSIONS
  Shunt patency studies are very useful for evaluation of shunt patency. Their results can be interpreted using a single-variable (T(1/2)) algorithm. Patients most likely to respond to a revision surgery are those who had a good response to original placement of a ventriculoperitoneal shunt.
authors.affiliation: Department of Neurology, The Johns Hopkins University School of Medicine, Adult Hydrocephalus Program, The Johns Hopkins Hospital, Baltimore, Maryland 21287, USA.
authors.forename: Siddharth
authors.initials: S
authors.lastname: Kharkar
authors.forename: John
authors.initials: J
authors.lastname: Shuck
authors.forename: Sumit
authors.initials: S
authors.lastname: Kapoor
authors.forename: Sachin
authors.initials: S
authors.lastname: Batra
authors.forename: Michael A
authors.initials: MA
authors.lastname: Williams
authors.forename: Daniele
authors.initials: D
authors.lastname: Rigamonti
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D004867:Equipment Design; D004868:Equipment Failure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D011868:Radioisotopes; D011877:Radionuclide Imaging; D012189:Retrospective Studies; D013997:Time Factors; D014654:Vascular Patency / Q000502:physiology; D017287:Ventriculoperitoneal Shunt / Q000009:adverse effects* / Q000295:instrumentation*
chemical_list: D011868:Radioisotopes