Differences in cause of revision in early and late shunt revisions – And how it correlates to the preventable shunt revision rate

Background: Shunt revisions constitute a major neurosurgical hurdle. The subject has been thoroughly investigated, and recently the term preventable shunt revision rate has been introduced focusing on early malfunctions. We aim to investigate the differences between early and late malfunctions and identify further preventable causes of revision. Methods: The study was based on two databases of shunt surgery from Copenhagen University Hospital and Aarhus University Hospital. We extracted details on shunt surgery, including cause of revision and time to revision. In this study, we presented a Kaplan-Meier curve and made a subdivision in early and late revisions. Causes for early and late revisions were subsequently compared. Results: A total of 622 patients with mean follow-up time of 1.58 years were included. During follow-up 243 (39.1%) patients had at least one shunt revision. The Kaplan-Meier shunt survival curve could be mathematically described as biphasic with an early and a late curve section. The intersection between the two sections was at 0.2 years. Shunt survival was 77.7% at 0.2 years and 59.5% at two years. The causes for early and late revisions differed significantly in terms of infections (early revision), valve defects, and disconnections (late revisions). Conclusions: We found that early shunt revisions are predominant, and that causes for early shunt revisions in some terms differ from late shunt revisions. In early revisions infections are overrepresented, while valve defects and disconnections are overrepresented in late revisions. Our findings suggest that reduction of early and late shunt revisions could require different strategies.