Localizing Broca's area for transcranial magnetic stimulation: Comparison of surface distance measurements and stereotaxic positioning

Weiduschat, Nora; Habedank, Birgit; Lampe, Birgit; Poggenborg, Jörg; Schuster, Alexander; Haupt, Walter F.; Heiss, Wolf Dieter; Thiel, Alexander

doi:10.1016/j.brs.2008.09.005

« Previous Next »BRAIN STIMULATION: Basic, Translational, and Clinical Research in Neuromodulation
Volume 2, Issue 2 , Pages 93-102, April 2009

Localizing Broca's area for transcranial magnetic stimulation: Comparison of surface distance measurements and stereotaxic positioning

Nora Weiduschat, MD
- Department of Neurology, University of Cologne, Cologne, Germany
- Correspondence: Dr. Nora Weiduschat, Department of Neurology, University of Cologne, Kerpener Str. 62, 50924 Cologne, Germany.
Birgit Habedank, MD
- Department of Neurology, University of Cologne, Cologne, Germany
Birgit Lampe
- Department of Neurology, University of Cologne, Cologne, Germany
Jörg Poggenborg, MD
- Department of Radiology, University of Cologne, Cologne, Germany
Alexander Schuster
- Max-Planck Institute for Neurological Research, Cologne, Cologne, Germany
Walter F. Haupt, MD, PhD
- Department of Neurology, University of Cologne, Cologne, Germany
Wolf Dieter Heiss, MD, PhD
- Max-Planck Institute for Neurological Research, Cologne, Cologne, Germany
Alexander Thiel, MD, PhD
- Department of Neurology, McGill University, Montreal, Quebec, Canada

Received 26 June 2008; received in revised form 8 September 2008; accepted 10 September 2008. published online 10 December 2008.

Background

Precise placement of transcranial magnetic stimulation (TMS) coils over target regions is crucial for correct interpretation of TMS effects. Modern frameless stereotaxic systems yield high accuracy, but require extensive equipment and cannot be used in every setting, for example, during functional imaging sessions.

Objective

The aim of this study was the development of a method for TMS-coil placement based on individual imaging data without the need for external tracking devices.

Methods

We compared coil positioning over Broca's area using an advanced stereotaxic navigation system with placement according to the surface distance measurements (SDM) method. By using the SDM-method, 3-dimensional renderings adapted from individual T1-weighted magnetic resonance imaging (MRI) data were created to identify Broca's area and Broca's homologue, respectively, and to define anatomic landmarks on the skin's surface. Distances between these landmarks were used to localize the real target on the individual's head.

Results

The mean Euclidean distance between surface positions as determined with the two methods was 8.31 mm and the mean difference of estimated virtual electric field intensity at the target point was 7.37 V/m corresponding to 4.01% of maximum field strength.

Conclusions

Our findings suggest that, compared with a state-of-the-art frameless stereotaxy system, the SDM-method yields a reasonable accuracy for positioning of a TMS-coil over Broca's area in terms of spatial coordinates.

Keywords: rTMS, target localization method, coil placement, neuronavigation, TMS aiming accuracy