Radionuclide shunt patency study for suspected ventriculoatrial shunt malfunction

Objectives Radionuclide shunt studies have been used at some centers for decades to evaluate intracranial shunt patency, however, the methodology is not standardized nor well-validated. The purpose of this study is to determine the clinical utility of radionuclide ventriculoatrial (VA) shunt studies for diagnosis of suspected shunt malfunction.

Methods A retrospective review was undertaken of all patients who had a VA radionuclide shunt patency study between 2001 and 2009. All had a 20-min gamma camera acquisition (1 min/frame) immediately following injection of Tc-99m DTPA into the shunt reservoir. Time activity curves were generated and a half time (T1/2) of emptying quantified. The results of the radionuclide study were correlated with medical and surgical records and final diagnoses.

Results The studies of 42 patients were retrieved; 2 had no clinical follow up and were eliminated from analysis. 49 studies in 40 adult patients were analyzed. Primary diagnoses included pseudotumor cerebri (25), normal pressure hydrocephalus (11) and obstructed hydrocephalus (4). 13 shunt studies had a T1/2 of 3.9 to 8.0 min minutes; these patients did not need revision surgery for a mean follow up of 15.1 months. 14 patient studies had a T1/2 < 3.9 min; 13 had over draining shunts, 1 required revision surgery. 22 had a T1/2 > 8 min; further evaluation included neuroexam, neuroimaging and intracranial pressure monitoring; 13 had shunt obstruction, 9 had over drainage and all had intraoperative confirmation.

Conclusions Radionuclide VA shunt studies are valuable for evaluation of ventriculoatrial shunt patency. Results can be interpreted using a single-variable (T1/2). T1/2 of 3.9 to 8 minutes indicates a patent shunt; T1/2 < 3.9 min is consistent with overdrainage. T1/2 of > 8 requires further evaluation to differentiate between obstruction and over drainage