Cerebrospinal fluid shunt technology.

Since the invention of the first implantable shunt valve by Nulsen and Spitz (12) almost 50 years ago, there has been a remarkable number of ingenious modifications and new designs of shunt equipment to treat pediatric hydrocephalus. These developments were in response to the immediately evident high shunt failure rate. These designs included antisiphon devices (15), on-off devices, gravity-actuated changes in opening pressure, and even externally adjustable valves, some with electromagnetic programmers (16) (Fig. 18.1). Aside from the introduction of the silicone elastomer material, there has in fact been little clinical impact on the treatment with patients with shunts. Moreover, there has been a recognition of the unexpected complications-cor pulmonale (11) and shunt nephritis (19) from cardiac shunts, bowel erosion from springcoiled catheters (1), obstruction of anti-siphon devices by capsule formation (3), and tonsilar herniation by lumboperitoneal shunts (2). In fact, each new shunt equipment design has in many cases brought along its own unique set of complications. Interpretation of the results of new shunt hardware was often hampered by the design of the studies. They often contained small retrospective series of patients, loosely defined inclusion criteria, poor definition of outcome events, short follow-up, and inappropriate statistical analysis. These studies were often conducted by enthusiasts of the devices who had vested interests in the outcome, including financial incentives. Early enthusiastic reports were often followed by less enthusiastic ones, often about unexpected complications.