Ventriculostomy-associated hemorrhage: a risk assessment by radiographic simulation

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OBJECTIVE

Ventriculostomy entry sites are commonly selected by freehand estimation of Kocher's point or approximations from skull landmarks and a trajectory toward the ipsilateral frontal horn of the lateral ventricles. A recognized ventriculostomy complication is intracranial hemorrhage from cortical vessel damage; reported rates range from 1% to 41%. In this report, the authors assess hemorrhagic risk by simulating traditional ventriculostomy trajectories and using CT angiography (CTA) with venography (CTV) data to identify potential complications, specifically from cortical draining veins.

METHODS

Radiographic analysis was completed on 50 consecutive dynamic CTA/CTV studies obtained at a tertiary-care academic neurosurgery department. Image sections were 0.5 mm thick, and analysis was performed on a venous phase that demonstrated high-quality opacification of the cortical veins and sagittal sinus. Virtual ventriculostomy trajectories were determined for right and left sides using medical diagnostic imaging software. Entry points were measured along the skull surface, 10 cm posteriorly from the nasion, and 3 cm laterally for both left and right sides. Cannulation was simulated perpendicular to the skull surface. Distances between the software-traced cortical vessels and the virtual catheter were measured. To approximate vessel injury by twist drill and ventricular catheter placement, veins within a 3-mm radius were considered a hemorrhage risk.

RESULTS

In 100 virtual lines through Kocher's point toward the ipsilateral ventricle, 19% were predicted to cause cortical vein injury and suspected hemorrhage (radius ≤ 3 mm). Little difference existed between cerebral hemispheres (right 18%, left 20%). The average (± SD) distance from the trajectory line and a cortical vein was 7.23 ± 4.52 mm. In all 19 images that predicted vessel injury, a site of entry for an avascular zone near Kocher's point could be achieved by moving the trajectory less than 1.0 cm laterally and less than 1.0 cm along the anterior/posterior axis, suggesting that empirical measures are suboptimal, and that patient-specific coordinates based on preprocedural CTA/CVA imaging may optimize ventriculostomy in the future.

CONCLUSIONS

In this institutional radiographic imaging analysis, traditional methods of ventriculostomy site selection predicted significant rates of cortical vein injury, matching described rates in the literature. CTA/CTV imaging potentiates identification of patient-specific cannulation sites and custom trajectories that avoid cortical vessels, which may lessen the risk of intracranial hemorrhage during ventriculostomy placement. Further development of this software is underway to facilitate stereotactic ventriculostomy and improve outcomes.

ABBREVIATIONS CTA = CT angiography; CTV = CT venography.

Article Information

Correspondence William B. Gormley, Department of Neurosurgery, Brigham and Women's Hospital and Harvard Medical School, 75 Francis St., Boston, MA 02115. email: wgormley@partners.org.

INCLUDE WHEN CITING Published online December 2, 2016; DOI: 10.3171/2016.8.JNS16538.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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Figures

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    Three-dimensional reconstructions performed using medical diagnostic imaging software to depict ventriculostomy trajectory (yellow arrow) and risk of cortical vessel injury. The entry site was marked by measuring along the skull surface, 10 cm posteriorly from the nasion in the sagittal plane (A), and 3 cm laterally in the coronal plane for both right and left sides (B), with perpendicular entry. The rest of the images (C–F) demonstrate measurements between a ventricular catheter and the nearest cortical vessel (C–E, red; F, blue). Figure is available in color online only.

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    Bar graph showing the distance between the ventricular catheter and nearest cortical vessel, according to a simulated ventriculostomy trajectory on CTA. Assuming a twist-drill diameter of 6 mm, vessels within a 3-mm radius (red) were considered at risk for iatrogenic damage. Figure is available in color online only.

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    Measuring avascular zones on CT angiograms. For those trajectories that involved vessel injury, the cortical vessel anatomy was viewed in a plane perpendicular to the trajectory, and the area was surveyed for the nearest avascular zone in which a cannula could be safely placed. The circles are 6 mm in diameter to reflect the area of the twist drill. Red circles represent the empirical entry at Kocher's point for 2 representative images (A and B) where vessel injury was predicted. The distance from the empirical entry site to an avascular zone (green circles) was measured (B). An avascular zone existed in all cases. Figure is available in color online only.

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    Calculating an ideal ventriculostomy site. Avascular zones near Kocher's point were attainable with minor adjustments to the trajectory (< 1.0 cm laterally and < 1.0 cm along the anterior/posterior axis) in all 19 cases of predicted vessel injury. The nearest avascular zone is indicated by the black dots on the skull. Notably, the coordinates of the nearest avascular zone differed by patient, underscoring the importance of patient-specific ventriculostomy planning. Figure is available in color online only.

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