Discussion Of The Accuracy Of External Ventricular Drain

Objective This study retrospectively analyzed the head computerized tomography(CT) from the patients who were performed external ventricular drain (EVD). Under three-dimensional (3D) model measurements were made to calculate position of the burr hole, length and position of the catheter and its sagittal and coronal angular variations. The deviation with the theoretical position was analyzed. It also discussed the factors influence the accuracy of EVD and improvement measures so that we could find the effective measures which could improve the accuracy and success of operation.Methods Retrospective evaluation was performed on the head computed tomography (CT) scans of59patients who underwent73freehand EVDs (45patients were underwent in the right of heads,14patients were underwent in the both). Under three-dimensional model measurements were made to calculate position of the burr hole, length and position of the catheter and the sagittal and coronal angular variations.Results Under3D model the mean distance from the catheter tip to the Monro foramen was60mm (47mm-69mm) and the distance of54cases (74%) was between5cm to7cm. The mean distance from burr hole to coronal suture was24mm (19mm-27mm), while to midline was25mm (16mm-34mm), and the intracranial catheter length was63mm (45mm-101mm)。Regarding accurate catheter tip placement, the catheter tips of26cases (35.6%) were in the ipsilateral lateral ventricle (target place),15cases (20.5%) were in lateral ventricle body,11cases (15.1%) were in the third ventricle,11cases (8.2%) were in the contralateral ventricle,10cases(13.7%) were within the inter hemispheric fissure, and5cases(6.8%) were in the interhemis pheric fissure.29cases(39.7%) of the EVDs were in the sagittal plane and31cases (42.5%) were in the coronal plane with an angular variation of±5°to the target and20cases (27.4%) were in the both planes with an angular variation of±5°the target. On the standard which was reported by Kakarla et al., this study shows that only79.5%was considered as functional,35.6%was in the target place。Conclusion Because of the traditional EVD was usually performed without any guidance and only by surgery’s experience, the deviations were made easily. So there was certainly much room for improving the EVD operation and the operation need effective guidance so that improve the accuracy and success.