Entry points for catheter placement in convection-enhanced delivery--a retrospective anatomic analysis

Planning the trajectories for catheter positioning in convection-enhanced delivery (CED) is delicate. The bulk flow follows the path of least resistance. Additional factors such as the varying tumor location and the functional relevance of the surrounding brain areas add to complicate the trajectory planning even further. Therefore several criteria have been established, dealing with the correct general entry and target point position. The goal of our study was to analyze the trajectories for CED catheters placed in our department to find preferable entry point positions.

We retrospectively looked at 51 trajectories for CED catheters planned with neuronavigation during 2003-2005 for 21 patients with supratentorial malignant gliomas. We evaluated the entry points for their anatomic position, the functional relevance of the area and their parameter to reach the important white matter tracts for CED. This was done using the anatomic literature, macroscopical studies in our laboratory on human autopsy brains and MR imaging.

Most tumors were located in the fronto-temporo-parietal region. For these locations catheters were predominantly placed via the superior parietal lobule and the superior frontal gyrus. Looking at the anatomic literature and our laboratory results we characterized these areas with properties predisposing them for catheter placement as having wide superficial gyri and few deep sulci. In addition, they have far less functional relevance than the surrounding eloquent areas. Most relevant white matter tracts can be reached from these entry points. Accordingly, we have defined 2 areas that appear most suitable as entry points in CED catheter placement: the superior parietal lobule and superior frontal gyrus.

Inserting CED catheter via the described entry points will presumably save time in planning and reduce side effects.