CSF shunts 50 years on - past, present and future

Cerebrospinal fluid (CSF) shunts were invented almost 50 years ago. While t heir introduction revolutionized the treatment of hydrocephalus, their comp lications have become legendary, and the focus of much investigation and de velopment of new devices. New devices have been based upon improved underst anding of the pathophysiology of hydrocephalus or shunt complications. Desp ite the rational, or frequently "more physiolagical," functioning of these devices, all too often unexpected complications have ensued, and the initia l enthusiasm for the devices has waned. Assessing the efficacy of the devic es has been difficult, owing to the lack of properly conducted studies. Nev ertheless, the overall impact of shunt design improvements has seemed very limited. A recent randomized trial of CSF shunt design, examining the failu re rates of two new and widely used valves (the Cordis Orbis Sigma and the Medtronic PS Medical Delta valves) failed to find any advantage of these ov er standard valve designs, many of which have been used almost since the in ception of CSF shunts. A search for risk factors for failure, in a post hoc analysis of the data, indicated only that the etiology of the hydrocephalu s and the position and local environment of the ventricular catheter tip we re probably important. Remarkably, the rate of change in the size of the ve ntricles and the final ventricular size were not different despite the subs tantial differences in flow characteristics of the two new valves. Shunt fa ilure rates of less than 5% at 1 year, with infection rates of less than 1% , seem like reasonable goals for the next decade in the new millenium. This can be achieved through basic research into the pathophysiology of shunt f ailure with improved mathematical models, and perhaps animal models of shun t failure. Efficacy of new devices or treatments must be scrutinized scient ifically so as not to waste valuable resources and time on unproven treatme nts. Uncontrolled series and testimonial assertions about new treatments or devices, especially from proponents with a vested interest, should be rega rded with great skepticism. Nevertheless, our best efforts are likely to re sult in a major advance in the management of pediatric hydrocephalus, which now seems tantalizingly close.