Tapping of a suspected malfunctioning ventriculoperitoneal shunt is usually easy, sometimes informative, but also potentially misleading. The purpose of this study was to determine the effectiveness of a shunt evaluation protocol that does not involve direct shunt tapping except in rare and specific cases.
The authors adopted a protocol for shunt evaluation that involves shunt tapping only in selected cases of suspected infection or in patients with noncommunicating hydrocephalus and equivocal computed tomography (CT) findings of shunt infection. They then reviewed the clinical characteristics and surgical findings in 373 consecutive assessments of 155 pediatric patients who were evaluated for shunt malfunction and/or infection by using this protocol between January 2003 and December 2005.
Mental status change and headache were the symptoms most concordant with shunt malfunction, but no symptom had a predictive value much better than 50%. Follow-up CT scans demonstrated enlarged ventricles in 72 of 126 cases of shunt revision. Among those with obstruction but without remarkable CT changes, 8 patients had evidence of distal obstruction on x-ray “shunt series” consisting of skull, chest, and abdominal radiographs, and 5 had obvious symptoms that rendered further testing unnecessary; 38 cases of obstruction were diagnosed based on elevated opening pressure on lumbar puncture (mean 34.7 cm H2O). A shunt tap was required in only 8 cases (2%).
The authors have shown that it is possible to evaluate the majority of ventricular shunt malfunctions without tapping the device. Because it is possible to diagnose shunt obstruction correctly by other means, the shunt tap may not be obligatory as a routine test of the device's patency.