• Reuben R Shamir, Leo Joskowicz, Sergey Spektor, and Yigal Shoshan.
• School of Engineering and Computer Science, The Hebrew University, Jerusalem, Israel.
• Neurosurgery. 2011 Mar 1; 68 (1 Suppl Operative): 95-101; discussion 101-2.

BackgroundCatheter, needle, and electrode misplacement in navigated neurosurgery can result in ineffective treatment and severe complications.ObjectiveTo assess the Ommaya ventricular catheter localization accuracy both along the planned trajectory and at the target.MethodsWe measured the localization error along the ventricular catheter and on its tip for 15 consecutive patients who underwent insertion of the Ommaya catheter surgery with a commercial neuronavigation system. The preoperative computed tomography/magnetic resonance images and the planned trajectory were aligned with the postoperative computed tomography images showing the Ommaya catheter. The localization errors along the trajectory and at the target were then computed by comparing the preoperative planned trajectory with the actual postoperative catheter position. The measured localization errors were also compared with the error reported by the navigation system.ResultsThe mean localization errors at the target and entry point locations were 5.9 ± 4.3 and 3.3 ± 1.9 mm, respectively. The mean shift and angle between planned and actual trajectories were 1.6 ± 1.9 mm and 3.9 ± 4.7°, respectively. The mean difference between the localization error at the target and entry point was 3.9 ± 3.7 mm. The mean difference between the target localization error and the reported navigation system error was 4.9 ± 4.8 mm.ConclusionThe catheter localization errors have significant variations at the target and along the insertion trajectory. Trajectory errors may differ significantly from the errors at the target. Moreover, the single registration error number reported by the navigation system does not appropriately reflect the trajectory and target errors and thus should be used with caution to assess the procedure risk.

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