Programmable shunt assistant tested in Cambridge shunt evaluation laboratory

Abstract

Objective: The programmable Shunt Assistant (capped!) (ProSA) shunt system has recently been introduced into clinical use. The system can be in vivo adjusted magnetically, and this adjustability is supposed to affect CSF drainage only in the vertical body position. Materials and methods: We tested a combination of ProSA with fixed differential pressure valve designed to drain cerebrospinal fluid (CSF) from the brain ventricles into the peritoneal cavity. Results: The ProSA showed good mechanical durability and stability of hydrodynamic performance over a 60-day period. The flow-pressure performance curves and operating pressures were stable, fell within the limits specified by the manufacturer, and changed according to the programmed performance levels. The ProSA system has higher than usual hydrodynamic resistance (around 8.8 mmHg/(mL/min)) in the vertical position. Operating pressure in the vertical position reacted repeatedly to changes of settings within the limits 0-40 cmH2O and was reduced gradually when the axis of the valve declined from vertical to horizontal. External programming proved to be reliable. Strong magnetic fields (3-T MRI) were not able to change the programming of ProSA. Conclusion: ProSA works in the horizontal position as differential fixed pressure low hydrodynamic resistance and in the vertical position as an adjustable, normal hydrodynamic resistance valve. It is able to compensate for posture-related overdrainage.