Ventricular shunt tap as a predictor of proximal shunt malfunction in children: a prospective study

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The clinical diagnosis of cerebrospinal fluid (CSF) shunt malfunction can be challenging. In this prospective study, the authors evaluated a common method of interrogating shunts: the shunt tap; specifically, its ability to predict proximal malfunction.


The authors performed standardized shunt taps in a consecutive series of cases involving children with suspected or proven shunt malfunction, assessing flow and, when possible, opening pressure. Data were collected prospectively, and results analyzed in light of surgical findings.


A shunt tap was performed prior to 68 operative explorations in 51 patients. Of the 68 taps, 28 yielded poor or no CSF flow on aspiration. After 26 of these 28 procedures, proximal catheter obstruction was identified. After 28 taps with good CSF return and normal or low opening pressure, 18 shunts were found to have a proximal obstruction, 8 had no obstruction, and 2 had a distal obstruction. Another 12 taps with good CSF flow had high opening pressure; subsequent surgery showed distal obstruction in 11 of the shunts, and proximal obstruction in 1. The positive predictive value of poor flow was 93%, while good flow on shunt tap predicted adequate proximal catheter function in only 55% of cases.


Poor flow of CSF on shunt tap is highly predictive of obstruction of the proximal catheter. Because not all patients with good flow on shunt tap underwent surgical shunt exploration, the specificity of this test cannot be determined. Nonetheless, a shunt tap that reveals good flow with a normal opening pressure can be misleading, and management of such cases should be based on clinical judgment.

Abbreviations used in this paper: CSF = cerebrospinal fluid; CT = computed tomography; MR = magnetic resonance.

Article Information

Address correspondence to: Bermans J. Iskandar, M.D., University of Wisconsin Hospital & Clinics, 600 Highland Avenue, K4/832, Madison, Wisconsin 53792-8660. email:

© AANS, except where prohibited by US copyright law.



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    Diagram showing the findings on surgical exploration after 68 shunt tap procedures.

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    Diagram illustrating the correlation of shunt tap results with surgical findings. n = number of shunt taps.

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    Diagram demonstrating the correlation of shunt tap results with surgical findings in patients with larger ventricles.

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    Diagram illustrating the correlation of shunt tap results with surgical findings in patients with slit ventricles.

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    Diagram depicting the correlation of shunt tap results with surgical findings in patients with unchanged ventricles (not slitlike).



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