Deep brain stimulation (DBS) is used to reduce the motor symptoms such as rigidity or bradykinesia, in patients
with Parkinson's disease (PD). The Subthalamic Nucleus (STN) has emerged as prime target of DBS in idiopathic PD.
However, DBS surgery is a difficult procedure requiring the exact positioning of electrodes in the pre-operative selected
targets. This positioning is usually planned using patients' pre-operative images, along with digital atlases, assuming that
electrode's trajectory is linear. However, it has been demonstrated that anatomical brain deformations induce electrode's
deformations resulting in errors in the intra-operative targeting stage. In order to meet the need of a higher degree of
placement accuracy and to help constructing a computer-aided-placement tool, we studied the electrodes' deformation in
regards to patients' clinical data (i.e., sex, mean PD duration and brain atrophy index). Firstly, we presented an automatic
algorithm for the segmentation of electrode's axis from post-operative CT images, which aims to localize the electrodes'
stimulated contacts. To assess our method, we applied our algorithm on 25 patients who had undergone bilateral STNDBS.
We found a placement error of 0.91±0.38 mm. Then, from the segmented axis, we quantitatively analyzed the
electrodes' curvature and correlated it with patients' clinical data. We found a positive significant correlation between
mean curvature index of the electrode and brain atrophy index for male patients and between mean curvature index of the
electrode and mean PD duration for female patients. These results help understanding DBS electrode' deformations and
would help ensuring better anticipation of electrodes' placement.
Movement disorders in Parkinson disease patients may require functional surgery, when medical therapy isn't effective.
In Deep Brain Stimulation (DBS) electrodes are implanted within the brain to stimulate deep structures such as
SubThalamic Nucleus (STN). This paper describes successive steps for constructing a digital Atlas gathering patient's
location of electrodes and contacts for post operative assessment.
Materials and Method
12 patients who had undergone bilateral STN DBS have participated to the study. Contacts on post-operative CT scans
were automatically localized, based on black artefacts. For each patient, post operative CT images were rigidly registered
to pre operative MR images. Then, pre operative MR images were registered to a MR template (super-resolution
Collin27 average MRI template). This last registration was the combination of global affine, local affine and local non
linear registrations, respectively. Four different studies were performed in order to validate the MR patient to template
registration process, based on anatomical landmarks and clinical scores (i.e., Unified Parkinson's disease rating Scale).
Visualisation software was developed for displaying into the template images the stimulated contacts represented as
cylinders with a colour code related to the improvement of the UPDRS.
The automatic contact localization algorithm was successful for all the patients. Validation studies for the registration
process gave a placement error of 1.4 +/- 0.2 mm and coherence with UPDRS scores.
The developed visualization tool allows post-operative assessment for previous interventions. Correlation with additional
clinical scores will certainly permit to learn more about DBS and to better understand clinical side-effects.