Randomized crossover trial on motor and non-motor outcome of directional deep brain stimulation in Parkinson's disease.

Deep brain stimulation (DBS) with electric field steering may avoid areas responsible for side effects. This prospective randomized cross-over trial compared omnidirectional (OS) and directional (DS) subthalamic DBS in 19 patients. Electromyographically measured rigidity was the primary outcome. Motor and non-motor scores were secondary outcomes. There were no significant differences between OS and DS. In the acute setting, both conditions improved motor scores compared to no stimulation. Motor symptoms improved after 3 weeks of OS relative to acute measurements, whereas they worsened under DS. The more ventral the active contact, and the less the motor improvement sweet spot was stimulated, the greater the benefit of DS over OS for executive function. Accurate OS of the dorsal subthalamic nucleus ensures motor and non-motor improvements. While DS can mitigate executive decline stemming from off-target stimulation, it may lead to worse motor outcomes. Larger, long-term studies are needed to confirm these findings. (Registration: subthalamic steering for therapy optimization in Parkinson's Disease ClinicalTrials.gov: NCT03548506, 2018-06-06).