The HCRN recently published its work on using intraoperative ultrasound (US) to guide the placement of ventricular catheters during shunt surgery. Shunt catheters placed into specific areas of the ventricle (i.e. frontal horn or trigone) away from the choroid plexus, the organ that secretes CSF, are associated with lower rates of shunt failure. Our goal for the study was to show how effective intraoperative US is for placing catheters accurately. We found that the use of US did not significantly improve the rate of accurate placement (59%) compared to conventional shunt insertion techniques (49%). Shunt survival rates between the two insertion techniques were also similar.
Analysis of the study data suggests that the reason for the lower than expected accuracy rates is due to movement of the catheter from a good location to a bad location very early after catheter placement. When we looked at the images from the intraoperative US, over 85% of catheters were placed accurately, but when we compared these results to the first postoperative image, which were mostly CTs scans obtained on the first day after surgery, about 1/3rd of the catheter tips had moved away from the target. The movement of the catheter is probably multifactorial. It may be moving because of changes in head position between images, the type of shunt hardware at the entry site (e.g. use of right angle guide at burr hole site), the location of the entry site, the contour of the skull, the change in ventricular size, the stiffness of the catheter, and the thickness and compliance of the brain itself. Future work for the HCRN will be looking at which of these factors plays the most significant role in catheter migration, and searching for techniques to prevent migration. Ultimately we are searching for any modification to our current operative technique that prolongs survival of the shunt and results in fewer shunt failures.
Dr. Whitehead’s paper published in the Journal of Neurosurgery: Pediatrics in December 2013 can read for free online. We appreciate the support of Journal of Neurosurgery in making our papers free to the public.