Ventriculoperitoneal shunt block: what are the best predictive clinical indicators?

Abstract

Aims: To evaluate the predictive value of symptoms, signs, and radiographic findings accompanying presumed ventriculoperitoneal (VP) shunt malfunction, by comparing presentation with operative findings and subsequent clinical course. Methods: Prospective study of all 53 patient referrals to a paediatric neurosurgical centre between April and November 1999 with a diagnosis of presumed shunt malfunction. Referral pattern, presenting symptoms and signs, results of computed tomography (CT) scanning, operative findings, and clinical outcome were recorded. Two patient groups were defined, one with proven shunt block, the other with presumed normal shunt function. Symptomatology, CT scan findings, and the subsequent clinical course for each group were then compared. Results: Common presenting features were headache, drowsiness, and vomiting. CT scans were performed in all patients. Thirty seven had operatively proven shunt malfunction, of whom 34 had shunt block and three shunt infection; 84% with shunt block had increased ventricle size when compared with previous imaging. For the two patient groups (with and without shunt block), odds ratios with 95% confidence intervals on their presenting symptoms were headache 1.5 (0.27 to 10.9), vomiting 0.9 (0.25 to 3.65), drowsiness 10 (0.69 to 10.7), and fever 0.19 (0.03 to 6.95). Every patient with ventricular enlargement greater than their known baseline had a proven blocked shunt. Conclusions: Drowsiness is by far the best clinical predictor of VP shunt block. Headache and vomiting were less predictive of acute shunt block in this study. Wherever possible CT scan findings should be interpreted in the context of previous imaging. We would caution that not all cases of proven shunt blockage present with an increase in ventricle size. C erebrospinal fluid (CSF) shunts remain the mainstay of treatment for most cases of hydrocephalus in the paediatric population. All are prone to malfunction, with block being the commonest reported complication in most series. In the largest reported cohort of 1719 patients, 56% experienced at least one episode of shunt block in the 12 years following insertion.1 Similarly, Lazareff and colleagues 2 recently reported a 44% prevalence of shunt malfunction, including block, in 244 children with CSF shunts followed up over a period of up to six years post initial insertion. The peak "danger" period for blockage is in the first year after insertion, with rates as high as 20% recorded in some series.3 Annual rates of shunt blockage have been estimated by Rekate to be approximately 5%. 4 These findings are in keeping with our published unit experience in which we noted a 28% incidence of shunt block over a 10 year period, and that 55% of patients experienced at least one episode of shunt malfunction during this time.

Comparison of Rapid Cranial MRI to CT for Ventricular Shunt Malfunction

“…We defined a ventricular shunt malfunction as a patient who needed operative revision for relief of mechanical causes of altered shunt flow within 72 hours of initial ED evaluation. 1,8,9,21 Children who underwent neurosurgical intervention for reasons other than altered shunt flow (eg, infection) or whose ventricular shunt valve was adjusted were classified as not having a ventricular shunt malfunction. Two investigators (T.P.B., L.E.N.)…”

“…7,26 Second, a substantial minority of children with a ventricular shunt who present with signs of elevated intracranial pressure and a confirmed shunt obstruction at neurosurgery had no evidence of ventricular dilation on serial neuroimaging. 21,27 Ultimately, diagnosing shunt malfunction in a child with hydrocephalus continues to require integration of the clinical presentation and neuroimaging results by evaluating ED and neurosurgical clinicians.…”

CSF Shunt Failure with Stable Normal Ventricular Size

“…It is widely known that an increase in ventricular size is consistent with CSF shunt obstruction but it is less widely appreciated that stable ventricular size cannot rule out shunt obstruction [1, 2, 15]. This is probably the reason Murtagh et al [16] found CT scans unhelpful in the diagnosis of CSF shunt malfunction in 16% of children admitted to a hospital for possible shunt obstruction.…”

Clinical Manifestations of CSF Shunt Complications

“…Its incidence may be as high as 50 % in children [ 4 ]. Shunt malfunction may be due to proximal catheter obstruction (the most common), valve obstruction, distal catheter occlusion, disconnections of shunt parts, fracture of the tubing, or migration of the proximal or distal catheters.…”