Thomas Schönecker
This article features a specific method that points to the important question of increasing the anatomic accuracy in localizing electrode contacts in deep brain stimulation (DBS) of the basal ganglia. Representing my primary research interest, electrode localization appears to play a significant role, first in quantitative comparison across patients in group analysis, and second, in individual analysis of the positional relation of electrode contacts with respect to boundaries of the target nucleus and surrounding structures more often requested in a clinical context with regard to clinical effect and side effects. In this article we demonstrated an increased accuracy of localization of electrode contacts following an automated multistep anatomic normalization procedure that progressively optimizes registration accuracy of postoperative MRI data to the Montreal Neurological Institute (MNI) standard space at the subcortical region, which allows for comparison of localizations using the mediolateral x, anteroposterior y, and dorsoventral z coordinates. Importantly, linear registration is applied rather than nonlinear approaches in order to avoid distortion of the susceptibility artifact induced by the electrodes, which in turn allows for assessment of the geometric center of the electrode contacts. This method has been applied frequently in a number of group studies as well as in daily clinical routine and continues to be used. One strength to accurate electrode localization in the MNI-stereotactical space is the availability of an increasing number of probabilistic atlases (eg, Harvard-Oxford subcortical atlas) that facilitate labeling coordinates of contacts with percentage probability of a structure, instead of applying rigid borders that may not reflect the diverse anatomic variances across individuals.