gms | German Medical Science

Objective: Stereotactic planning for DBS surgery is usually performed by fusing preoperative MRI with stereotactic CT scans. Intraoperative stereotactic MRI scans with image distortion correction enable stereotactic frame fitting and movement artifact-free image acquisition as well as direct image-guided electrode planning.

Methods: We report on our series of DBS surgeries for movement disorders using the intraoperative 1.5T Siemens Espree MRI scanner for stereotactic electrode planning since the installation in 2009. Patient demographics are presented. Euclidean electrode implantation accuracy and directional targeting errors are calclulated via postoperative CT image fusion and correlated with factors like age, implantation order, intracranial air, number and of MER tracts and Evan’s Index. Complications are recorded. Times for surgery, anaesthesia and time in the stereotactic frame are given and compared in the first and last 10 STN and Vim surgeries.

Results: n=81 patients with n=86 DBS surgeries were performed using intraoperative stereotactic MRI for electrode planning. n=49 patients were operated for Parkinson’s disease (PD) in the STN, n=27 patients were operated for tremor (ET) in the Vim and n=5 patients were operated for dystonia (DY) in the GPi. Mean age at surgery was 60.4 years (9-87). 539 MER trajectroies were chosen. In 71,3% of cases center trajectroies were chosen for electrode implantation on the Ben gun. Mean Euclidean distance for electrode implantation accuracy was 2.1mm +/-0.6mm). Electrode implantation accuracy did not correlate with age, implantation order, intracranial air, the number of MER tracts or Evan’s Index. Electrodes showed mean directional errors in medial (X=-0.3mm), posterior (Y=-0.5mm) and inferior (Z=-0.6mm) trajectories. n=1 intracranial hemorrhage (1.1%), n=2 ischemic strokes (2.3%), n=2 seizures (2.3%) and n=3 hardware infections (3.5%) ocurred. N=1 out of 167 electrodes had to be repositioned for lack of effectiveness (0.6%). Time for surgery and time spent in the stereotactic frame were significantly reduced in the last 10 cases by 61 and 59 minutes for Vim surgery and by 121 and 120 minutes for STN surgery (p=0.01) compared to the first 10 cases each.

Conclusion: Intraoperative stereotactic MRI for DBS electrode planning is a viable option that goes along with high implantation accuracy, low directional errors and a low complication profile. Our approach saves radiation from CT scan and spares the patient stereotactic frame fitting under local anaesthesia.