Preoperative determination of ventriculostomy trajectory in ventriculoperitoneal shunt surgery using a simple modification of the standard coronal MRI.

The aim of this technical report is to report a new method for ventriculoperitoneal (VP) shunt placement by determining the angle and distance of the proximal shunt catheter trajectory in the coronal plane using a simple modification of a standard coronal MRI. A modified coronal MRI (mcMRI) was taken in the coronal plane, which included Kocher's point and a point 1cm anterior to the tragus. Using this mcMRI, the trajectory from Kocher's point to a target in the frontal horn may be determined, and the angle and distance of the proximal shunt catheter trajectory may also be obtained. We identified a "safety angle" for catheter insertion, which avoided contact with any intraventricular structures. In addition, the length of the proximal catheter was calculated using the mcMRI, which we defined as the "safety depth." Twenty VP shunt surgeries were performed using an individual safety angle and safety length as determined by a preoperative mcMRI. The ventriculostomy was successful on the first attempt in all patients. The accurate placement of the proximal catheter was confirmed using a postoperative mcMRI. Only one patient demonstrated a track hemorrhage around the catheter path on CT scans. Follow-up evaluations were performed 3 to 12 months after the shunt surgery. The mcMRI protocol is a simple modification of the standard coronal MRI and may important for the determination of an accurate angle and distance of the proximal catheter during free-hand ventriculostomy for VP shunt.