Evaluation of shunt malfunction using shunt site reservoir.

OBJECTIVE To determine the usefulness of a separate reservoir placed at the site of the shunt in evaluation of shunt malfunction. METHODS AND MATERIALS A ventricular catheter was placed alongside the proximal catheter of the shunt and connected to a subgaleal reservoir in 17 patients, in 9 a double-lumen catheter with integrated reservoir and in 13 patients a dual catheter with a double-port reservoir was used. At presentation of suspected shunt malfunction, a standard shunt function evaluation using shunt tap, CT scan or shunt injection was performed, and subsequently, the pressure from the tap of the reservoir was obtained. RESULTS Thirty-three patients presented with symptoms of malfunction at an interval of 2.3 +/- 3 months (range 2-429 days). The pretest probability of shunt malfunction in this population was 73%. Posttest probability of shunt malfunction was 82.5% with standard evaluation and improved to 100% by the separate reservoir tap pressure measurement. In 4 patients in whom the shunt tap was dry, shunt infection was diagnosed prior to revision using CSF obtained at the reservoir tap. In 5 patients with proximal malfunction and bradycardia, the reservoir tap allowed early ventricular decompression. CONCLUSION This study shows that a reservoir placed at the site of the shunt remains patient even when the shunt malfunctions, suggesting that flow rather than catheter position is important in proximal malfunction. It is superior to shunt tap for detection of shunt malfunction and infection, and it allows early ventricular decompression in a sick patient awaiting surgery for shunt revision.