Obstruction of the ventricular catheter is a leading cause of shunt failure. This work focused primarily on preventing and reversing proximal ventricular-catheter obstruction with the ultimate goal of designing a ventricular catheter that will resist occlusion due to cellular accumulation.
Presently, the conventional treatment of an occluded shunt is surgical replacement. While studies have investigated in situ occlusion removal in place of complete catheter replacement, each technique still requires an invasive procedure to access to the malfunctioning catheter [5, 6, 7, 8, 9, 10]. Other approaches to improve the catheter design have yet to demonstrate efficacy in reducing ventricular catheter obstructions .
We proposed that microactuator technology could be used to non-invasively mitigate catheter obstruction in a permanently implanted device. Our approach was to use local mechanical force to clear the obstruction. We introduced a novel, remotely activated micromechanical element that generated sufficient force to physically sweep adherent cells from a hole comparable in size to that found in a ventricular catheter. Magnetic forces were particularly appealing for this application because they could be achieved using an external power supply (i.e., no implanted electronics or wired connections were required) as we demonstrated in prior work [12, 13, 14]. Furthermore, microfabrication technology allowed us to manufacture devices at the cellular-scale level, plus offered the potential of low-cost production.
We designed, fabricated, and tested functional magnetic microactuators. The actuator design consisted of a nickel magnet on a layer of silicon nitride that was anchored to the substrate by two silicon-nitride torsion beams. To identify the appropriate dimensions for the magnetic actuator, we designed an array of microactuators with varying physical parameters. We also investigated cellular adhesion strength in relation to the shear force produced by the microactuators. Using data from device characterization and prototype cellular actuation, we determined the device dimensions that contributed most significantly to cell removal ability.
To analyze the obstruction process for existing catheter designs, we designed, fabricated, and implemented an in vitro test setup. We used this setup to artificially create cellular occlusions within commercially available ventricular catheters. Future studies include integration of our microactuators into ventricular catheters, and comparison of the occlusion rates of MEMS-integrated catheters with traditional designs.
By producing a self-clearing ventricular catheter, we hope to realize a next-generation hydrocephalus shunt that will prevent or significantly delay shunt obstruction and thus reduce the frequency of shunt-replacement surgeries.