Evaluation of Shunt Malfunction Using a Shunt Site Reservoir
  Cost-effective evaluation of shunt malfunction is a perplexing problem. The shunt tap test has been effectively used to screen patients with suspect shunt malfunction. A complete radiological examination including a shunt survey, shunt injection test and CT scan may cost over a thousand dollars. Each of these tests, however, has drawbacks. In a patient with partial proximal obstruction or inadequately functioning shunt and slit ventricles; the shunt tap may show low pressure and some flow, the shunt injection may clear in presence of some flow, the CT scan may not show ventricular enlargement, and yet the intracranial pressure may be high. Intracranial pressure may be the only true guide to shunt function in these patients. Presence of a reservoir not in line with the shunt may be more helpful in estimating the pressure and evaluating shunt function.
 
  Abstract
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. (From: Sood,S., Canady,A.I., Ham,S.D., Pediatric Neurosurgery 2000; 32:180-186)