gms | German Medical Science

60th Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Benelux countries and Bulgaria

German Society of Neurosurgery (DGNC)

24 - 27 May 2009, Münster

Precision of frameless stereotactic probe positioning (VarioGuide) into the brainstem

Meeting Abstract

  • H. Giese - selbständiger Arbeitsbereich Pädiatrische Neurochirurgie, Charité - Universitätsmedizin Berlin
  • K.T. Hoffmann - Radiologie, Charité - Universitätsmedizin Berlin
  • A. Winkelmann - Anatomie, Charité - Universitätsmedizin Berlin
  • F. Stockhammer - Klinik für Neurochirurgie, Charité - Universitätsmedizin Berlin
  • U.W. Thomale - selbständiger Arbeitsbereich Pädiatrische Neurochirurgie, Charité - Universitätsmedizin Berlin

Deutsche Gesellschaft für Neurochirurgie. 60. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit den Benelux-Ländern und Bulgarien. Münster, 24.-27.05.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. DocP10-04

doi: 10.3205/09dgnc356, urn:nbn:de:0183-09dgnc3569

Published: May 20, 2009

© 2009 Giese et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: The quality of performing biopsies or placing probes into deep seated brain structures significantly depends on the precision of the technical procedure. Frameless stereotaxy, guided by neuronavigation, has its advantage in preoperative imaging; however, accuracy of this technique has been discussed. The study evaluates the precision of positioning brainstem probes using a navigated frameless stereotactic system in an experimental setting.

Methods: Using the frameless stereotactic system (VarioGuide, BrainLab) probes (n=33) were placed into a specially designed model filled with agarose. In a second experimental series, anatomical specimens (n=8) were used to position a total of 32 catheters into the pontine brainstem using ether a suboccipital or a pre-coronal entry point. Before intervention a thin sliced CT (GE, Lightspeed) for planning was performed in both settings and fused to a volumetric T1 MR data set (MP rage, GE Signa Twin Speed 1.5 Tesla). Using frameless stereotaxy, flexible catheters (PVC, 3Ch) were placed through an outer guide cannula. After this procedure a further CT as well as MR imaging were performed to compare the course and the position of the catheters to pre-interventional planning. The deviation between the planned position and the actual location of the catheter's tip was measured to evaluate the precision of the navigated intervention.

Results: Using the VarioGuide system a mean target deviation of 2.8±1.2mm in CT and 3.1±1.2mm in MRI was detected with a mean catheter length of 151mm in the agarose model. Catheter placement in the anatomical specimen revealed a mean tip deviation of 2.2±1.2mm in CT and 2.1±1.1mm in MRI imaging for the sub-occipital approach and a mean catheter length of 59.5mm. For the pre-coronal approach a deviation of 1.95±0.6mm in CT and 1.8±0.7mm in MRI was measured (catheter length 85.9mm).

Conclusions: The system-based deviation of frameless stereotaxy using the VarioGuide reveals good values for probe placement in deep seated brain tissue locations. Therefore we assume its accurate applicability for biopsies and probe placement in patients.