Objective: Validate an MRI procedure to localize the position of our final implanted electrodes.
Material and Methods: 26 parkinsonian patients were selected for DBS. Surgery was performed with a CRW (Radionics) frame. The final electrode (Medtronic Activa 3389) was implanted according to the MRI preoperative target, microrecording and macrostimulation. A postop 3D MPRAGE MRI was performed to localize the distal end of the distorsion artifact induced by the contacts of the electrodes. The size of this artifact was studied independently by scanning the electrode in a reference system. It allowed us to calculate the center of each contact, together with the projected angles of the electrode, the height of one contact and the distance between 2 adjacent contacts.
Results: A distance of 1.4 mm was measured between the artifact and the contact. 208 contacts and 65 active contacts were projected on sagittal, coronal and axial views of the Schaltenbrand and Wahren stereotactic atlas (SWSA). The mean coordinates of each contact were reported as well as the active contact (AP: 3.09 mm behind, LAT: 12.06 mm, VERT: 4.06 mm below the MCP). Conclusion: Considering the knowledge of the distorsion artifact induced by the electrodes, the validation of our procedure is based on the exact matching of the planned target and the mean active contact. The distribution of our contacts over the anatomical limits of the STN on the SWSA suggests a possible variability of position between individuals as well as the possible efficacy of other stimulated structures (SNr) on PD symptoms.