gms | German Medical Science

Objective: Subthalamic (STN) deep brain stimulation (DBS) lead placement for Parkinson’s disease (PD) is based upon anatomical landmarks, microelectrode recording, and test stimulation. Microelectrode recordings in five parallel tracts throughout the target region and clinical stimulation responses are used to select the tract and the depth for final lead placement. For reliable stimulation testing, patient cooperation is essential, which might be impaired by fatigue and sedation; furthermore awake craniotomies may cause additional discomfort to the patient. We therefore sought to answer the question, whether intraoperative macrostimulation is dispensible and whether lead placement is possible solely on the basis of MR anatomy and microelectrode recordings.

Method: We retrospectively reviewed intraoperative recording and stimulation protocols of 92 lead placements in 46 patients with advanced PD. In addition to clinical data we looked into (a) the position and the tract length of the distinct electrographic STN signal in relation to final electrode placement and (b) the influence of macrostimulation on final tract selection.

Results: Two lead placements in two patients were excluded from further analysis, as no test stimulation was performed because of poor patient cooperation, due to an intraparenchymal hemorrhage in one patient. Of the remaining 90 placement procedures, 39 leads (43%) were not placed in the position of the longest tract of microelectrode STN signals but were placed according to the results of test stimulation in at least two different trajectories. In eight placement procedures (9%), the trajectory used for implantation did not show any appropriate electrophysiological signal in the first place. The center trajectory showed the longest STN signal in 47 procedures, in these cases only six leads were placed in other than the center tract. For 61 final lead placements the center tract (67%) was chosen, the anterior trajectory was used in 14 procedures (16%), the medial position in seven (8%), the lateral position in five (6%) and the posterior position in three procedures (3%).

Conclusions: Although the majority of leads were placed in the center tract and/or the trajectory of the longest microelectrode STN signal, 43% of lead placements were guided by test stimulation. Test stimulation in selected trajectories was essential for proper lead positioning. Multiple test trajectories should always be planned if possible to allow for stimulation based lead position selection.