How Many Patients would Benefit from Steering

Steering was deemed useful for 42 patients (21.0%, 19 bilaterally) and 61 leads (15.7%). For STN leads, steering was considered useful for 12.8% of the patients and 8.5% of the leads, for GPi 48.0% of patients (37.5% of leads) and for thalamic area 39.3% of patients (37.5% of leads). (Fig. 1) The most common side-effect limiting a required increase of stimulation amplitude was dysarthria (38 leads), followed by muscle contractions (22 leads). For additional 29 patients, the usefulness of steering was dubious, for example when dyskinesias were the only side-effect, or side-effects had indefinite anatomical localization (e.g. light-headedness), or were not clearly related to stimulation (e.g. inconsistent symptoms, cognitive decline). The results of our study show that, according to the treating clinicians, up to 21% of movement disorders patients undergoing DBS could benefit from leads capable of directional steering, in order to achieve optimal treatment. This applied more frequently to patients with implants in the GPi (48.0%) or thalamic area (39.3%), compared to patients implanted in the STN (12.8%). Results suggest that patients with dystonia or tremors might benefit from this technology more often than those with PD, possibly due to higher amplitudes usually needed in these targets.