The Dominant-STN phenomenon in bilateral STN DBS for Parkinson's disease

In some patients with Parkinson's disease (PD) and bilateral STN-DBS the motor benefit from one STN alone appears similar to the improvement obtained with bilateral STN-DBS. Thus, we hypothesized that some patients have a “dominant-STN,” whose stimulation achieves similar results than bilateral stimulation.Twenty-two consecutive PD patients with bilateral STN-DBS were assessed in 4 randomized conditions: bilateral off-stimulation, bilateral on-stimulation, unilateral right- and unilateral left-stimulation. A hierarchical agglomerative cluster analysis of the motor UPDRS scores in these 4 conditions showed that 11 patients (50%) presented with a “dominant-STN.” Interestingly, in 3 of these patients the dominant-STN was ipsilateral to the most affected side of the body.Our results support the presence of different phenotypes of response to bilateral STN stimulation. In our sample 50% of the patients presented with a dominant-STN, suggesting that a non-negligible part of PD patients might not need bilateral STN-DBS surgery.

Research Highlights
► Stimulation of one STN achieved improvement similar to stimulation of both STN.
► This finding was called the “dominant STN phenomenon” in PD patients.
► A dominant STN was observed in 50% of a case series of PD patients with bilateral STN-DBS.
► Further research will help to tailor unilateral vs. bilateral STN-DBS to surgical candidates.