TIME-RELATED PATTERNS OF VENTRICULAR SHUNT FAILURE

Proximal obstruction is reported to be the most common cause of ventri culoperitoneal (VP) shunt failure, suggesting that imperfect ventricul ar catheter placement and inadequate valve mechanisms are major causes . This study retrospectively examined patterns of shunt failure in 128 consecutive patients with symptoms of shunt malfunction over a 2-year period. Factors analyzed included site of failure, time from shunt pl acement or last revision to failure, age of patient at time of failure , infections, and primary etiology of the hydrocephalus. One hundred o f these patients required revisions; 14 revisions were due to infectio ns. In this series there was a higher incidence of distal (43%) than o f proximal (35%) failure. The difference was not statistically signifi cant when the overall series was considered; however, when factoring t ime to failure as a variable, marked differences were noted regardless of the underlying cause of hydrocephalus or the age of the patient. O f the 49 patients needing a shunt revision or replacement within 2 yea rs of the previous operation, 50% had proximal malfunction, 14% distal , and 10% had malfunctions attributable directly to the valve itself. Also, 12 of the 14 infections occurred during this time interval. In s harp contrast, of the 51 patients having shunt failure from 2 to more than 12 years after the previous procedure, 72% had distal malfunction , 21% proximal, and only 6% had a faulty valve or infection. This diff erence between time to failure for proximal versus distal failures was statistically significant (P < 0.00001 for both Student's t-test and non-parametric Mann-Whitney U-test). It is concluded that these data a re valuable for interpreting outcome studies of novel valve systems an d ventricular catheter placement techniques, by defining a time frame during which these modifications can be reliably evaluated.