ABSTRACT
BACKGROUND: Convection Enhanced Delivery (CED) into targeted brain areas has been tested in animal models and clinical trials for the treatment of various neurological diseases. NEW METHOD: We used a series of techniques, to in effect, maintain positive pressure inside the catheter relative to the outside, that included a hollow stylet, a high volume bolus of solution to clear the line, a low and slow continuous flow rate during implantation, and heat sealing the catheter at the time of implantation. RESULTS: 120 catheters implanted into brain parenchyma of 89 adult female rhesus monkeys across four sets of experiments. After experiencing a high delivery failure rate - non patent catheters - (19 %) because of tissue entrapment and debris and/or blood clots in the catheter tip, we developed modifications, including increasing the bolus infusion volume from 10 to 20 µl such that by the third experiment, the failure rate was 8 % (1 of 12 implants). Increasing the bolus volume to 100 µl and maintaining positive pressure in the catheter during preparation and implantation yielded a failure rate of 0 % (0/12 implants) by the fourth experiment. COMPARISON WITH EXISTING METHODS: We provide a retrospective analysis to reveal how several different manipulations affect catheter patency and how post-op MRI examination is essential for assessing catheter patency in situ. CONCLUSIONS: The results of the present study identified that the main cause of the catheter blockages were clots that rendered the catheter non-patent. We resolved this by modifying the surgical procedures that prevented these clots from forming.
