The Relation between Catheter Occlusion and Backflow during Intraparenchymal Cerebral Infusions

Background/Aims: The distribution of infusate into the brain by convection-enhanced delivery can be affected by backflow along the catheter shaft. This work assesses the following: (1) whether tissue coring and occlusion of the catheter lumen occurs when an open end-port catheter is inserted, (2) whether there is a relationship between intracatheter pressure and backflow, and (3) whether catheter occlusion increases backflow. Methods: Freshly excised monkey brains were used to assess tissue coring and its correlation with the behavior of the line pressure. In vivo infusions of gadolinium solution into monkey putamen at 1 μl/min were conducted with and without a stylet during insertion. The effect of flow during insertion was evaluated in vivo in the pig thalamus. MRI and line pressure were continuously monitored during in vivo infusions. Results: Ex vivo testing showed that open end-port insertions always cored tissue (which temporarily plugs the catheter tip) and increased pressure followed by a rapid fall after its expulsion. Catheter insertion with a stylet in place prevented coring but not flow insertion; neither affected backflow. Conclusion: Open end-port catheters occlude during insertion, which can be prevented by temporarily closing the port with a stylet but not by infusing while inserting. Backflow was not completely prevented by any insertion method.