Deep brain stimulation (DBS) is an important therapy for movement disorders and DBS is being explored for treatment-resistant psychiatric conditions. The mechanism of action is investigated by combining computer simulations, physiological measurements, imaging and clinical evaluations. Disorders of interest are Parkinson’s disease, essential tremor, and new indications and targets where DBS is introduced. We are an international cross-disciplinary team with technical and clinical DBS expertise working together.
Methods
Deep brain stimulation
The DBS electrode has 4 contacts which are programmed with a pulse generator. For some DBS electrodes one or more contracts are split so the stimulation field can be steered. DBS electrodes are implanted in the deeper part of the brain, and the choice of target depends on the patient’s symptom. Implantation of DBS electrodes are done with stereotactic technique. For more information see Wårdell et al. 2022
Stereotactic DBS implantation and imaging
Stereotactic magnetic resonance imaging (MRI) is used for pre-operative target identification and planning of trajectories. During surgery the DBS electrode is introduced to the target point and the operation is fulfilled. Intraoperative measurements of neuronal activity with microelectrode recording (MER), microvascular blood flow and tissue grey-whiteness with laser Doppler flowmetry (LDF), or movement with wrist accelerometers may be done in relation to surgery. Post-operative verification of the DBS lead position is accomplished using MRI or CT. As a last step the pulse generator is implanted under the collor bonde. (Hemm & Wårdell 2010)
Patient-specific electric field simulations
Finite element method (FEM) simulation of the electric field surrounding the DBS lead is done in COMSOL Multiphysics (Åström et al., 2009, Åström et al., 2015). Individual DBS settings together with the pre- and postoperative images makes it patient-specific. Brain models are built in MatLab. Preprogrammed COMSOL-Apps for DBS lead configurations and stimulations modes are available for download. Results are visualized with the patient own preoperative images. See webinar
Present projects focus on group analys and prediction of DBS stimulation by combining simulations, patient outcome, creation of anatomical atlases and statistical analysis. (Nordin et al., 2022, Vogel et al. 2024)
Tractography
By using diffusion weighted MRI (dMRI) white matter tracts connecting brain regions involved in DBS can be anatomically visualized. This can also be combined with visualization of simulated patient-specific electric fields and the aptients own anatomical brain images. One example is the visualization of the dentato-rubro-thalamo-cortical circuit. Other white fiber tracts of interest in DBS are the pallidothalamic tracts and the hyperdirect cortico-subthalamic tracts. (Nordin et al., 2019)
Intraoperative optical measurements
Laser Doppler flowmetry (LDF) is used for intraoperative measurements of the brain microcirculation and tissue type during implantation of DBS electrodes. A probe with optical fibers is used as guide during creation of the trajectory. It functions an on-line “vessel alarm” for hemorrhage prevention and “bar codes” presenting grey-white tissue boundaries. (Zsigmond 2018; Wårdell et al., 2024)
Demonstrator
ELMA, DBSim and DBViS are Apps for DBS simulations and visualization available for request. With ELMA a patient-specific brain model is created. This is used as in-data for patient-specific simulations done with DBSim. DBViS displays extended information from our simulation studies and the user can compare these with their own simulations. Request the Apps
Previous and ongoing major projects
- SNSF Project: Prediction of Patient-Specific Deep Brain Stimulation Parameters (ongoing)
- SSF Big Data Project: Deep brain stimulation-data analysis for clinical support
- FP7project IMPACT: Improving the lives of Parkinson’s Diseases patients while reducing side effects through tailored deep brain stimulation
