Radionuclide shunt patency study for evaluation of suspected ventriculoperitoneal shunt malfunction in adults with normal pressure hydrocephalus.

Abstract

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. 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. 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. 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.