Freehand ventricular catheter placement
The standard method of Freehand ventricular catheter placement is a technique using surface anatomical landmarks. However, the standard freehand EVD technique results in catheter malpositioning in up to 60.1% of procedures 1).
It should be noted that neurosurgeons typically measure the success of freehand ventricular catheter placement by the free flow of cerebrospinal fluid (CSF) from the distal end of the ventricular catheter 2). However, this in itself is falsely reassuring, as a large percentage of ventricular catheter tips have been observed in CSF spaces other than the frontal horn of the lateral ventricle (e.g. subarachnoid space) even though there was CSF drainage at the start 3)
To avoid shunt dysfunction, it is essential to place the ventricular catheter tip above the foramen of Monro.
Supposing that a convex of skull matches to a sphere, in which the foramen of Monro is the center, a perpendicular direction from the surface of the sphere to inside always directs toward the center. The authors identified the range of skull where corresponded to the sphere by magnetic resonance imaging assessment and utilized tripod to achieve exactly perpendicular insertion of ventricular catheter. And an optimal length of catheter insertion was investigated by navigation system.
The anterior-posterior range of the spherical portion was from coronal suture to 20mm anterior, and the lateral range of it was between 15 and 35mm lateral from sagittal suture. The optimal catheter length for insertion was between 55 and 58mm from the brain surface. Ideal placement of a ventricular catheter tip was achieved in more than 90% of cases (31/34) with this technique 4).
A analysis demonstrated an improvement of catheter positioning with ultrasound guidance. In the absence of additional burden or risks, this method should be favored over freehand technique. It remains to be demonstrated in a randomized controlled fashion to what extent improved catheter position translates into improved outcome 5).
Free-hand insertion is associated with a significant ventricular catheter misplacement rate. Consequently, several expensive alternative methods that are unfortunately not available worldwide have been used.
Patients who underwent ventriculostomy placement in the ICU differed in important ways (i.e. indication for placement and the administration of pre-procedure prophylactic antibiotics) from patients treated in the OR. However, the available data suggests that complications of hemorrhage, infection, and non-functional drains may be mitigated by ventriculostomy placement in the OR 6).
Techniques to accurately place ventricular catheters and new valve designs that effectively control ventricular size might reduce shunt malfunction 7).
Accurate ventricular drainage placement plays an important role in reducing the risk of ventriculoperitoneal shunt failure.
Stereotactic- and ultrasound-guided ventricular catheter placements are significantly more accurate than freehand placement, and the use of these intraoperative guidance techniques reduced proximal shunt failure 8).
Retrospective evaluation was performed on the head computed tomography (CT) scans of 97 patients who underwent 98 freehand pass ventriculostomy catheter placements in an ICU setting. Using the postprocedure CT scans of the patients, 3D measurements were made to calculate the accuracy of ventriculostomy catheter placement.
The mean distance (+/- standard deviation [SD]) from the catheter tip to the Monro foramen was 16 +/- 9.6 mm. The mean distance (+/- SD) from the catheter tip to the center of the bur hole was 87.4 +/- 14.0 mm. Regarding accurate catheter tip placement, 56.1% of the catheter tips were in the ipsilateral lateral ventricle, 7.1% were in the contralateral lateral ventricle, 8.2% were in the third ventricle, 6.1% were within the interhemispheric fissure, and 22.4% were within extraventricular spaces.
The accuracy of freehand ventriculostomy catheterization typically required 2 passes per successful placement, and, when successful, was 1.6 cm from the Monro foramen. More importantly, 22.4% of these catheter tips were in nonventricular spaces. Although many neurosurgeons believe that the current practice of ventriculostomy is good enough, the results of this study show that there is certainly much room for improvement 9).
The use of image guidance technology added approximately 36 minutes to the time from when the need was identified to when successful drainage was achieved (p = 0.002), but added only 4 minutes of operative time (p = 0.12). Accuracy of placement demonstrated a statistically significant improvement in the accuracy of ventriculostomy over historical data. There were two registration failures which were converted to the traditional technique; there were no other complications arising from the use of image-guided technology. Electromagnetic image guidance is feasible and accurate. Image guidance technology eliminated unacceptably placed catheters and may reduce the risk of catheter-associated intracerebral hemorrhages 10).
Bruneau et al. developed a simple surgical technique based on radio-anatomical landmarks aimed at reducing VC's misplacements.
They reproduced the preoperative imaging on the patient's head using common anatomical landmarks. This allows defining stereotactic VC coordinates to be followed during the surgical procedure.
This simple and cost-effective method improves VC insertion accuracy 11).