Introduction: Deep brain stimulation (DBS) sytems are regarded as sealed systems, insulated from the potentially disruptive effect of fluid within the system. "Fluid shorts" percieved as a consequence of fluid contamination during implant are sometimes cited as a potential source of malfunction of the device. Our observations suggest other potential sources for fluid ingress into the DBS system.
Methods: Initial observations of some amount of tissue fluid in the subdermal pocket of implantable pulse generators(IPG) during replacement for battery exhaustion was our first hint at the DBS system existing far from a fluid naive environment. Further note of fluid levels within extension kits and adaptor kits(FIG 2) and soft tissue ingrowth along extension kit contacts to the IPG prompted further investigation. Methylene blue was used to simply demonstrate areas of capillary action that might explain these findings.
Results: Methylene blue demonstrated a strong capillary action along the central core of a DBS electrode ascending rapidly up the electrode against gravity.(FIG 1-Video) Methylene blue also demonstrated penetration into the internal architecture of a 2x4 adaptor.(FIG 3,4)
Conclusions: Capillary action may play a significant role in "fluid contamination" of the internal components of DBS systems even when scrupulous surgical technique is employed.
Patient Care: Appreciation of the role of capillary action in fluid contamination of DBS systems may help promote strategies of implant design and surgical technique to optimize outcome.
Learning Objectives: Sensitivity to the potential role of capillary action as it pertains to fluid contamination in DBS systems may sharpen observations by implanting surgeons of similar phenomena.