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.