Objective: The electrode position is important to the surgical outcome after subthalamic nucleus (STN) deep brain stimulation (DBS). The aim of this study was to compare the surgical outcome of bilateral STN DBS with the electrode position estimated using fused magnetic resonance imaging.
Methods: Bilateral STN DBS was performed in 60 patients with advanced Parkinson's disease. Patients were evaluated with the Unified Parkinson's Disease Rating Scale, Hoehn and Yahr staging, Schwab and England Activities of Daily Living, L-dopa equivalent dose, and Short Form-36 Health Survey before and at 3 and 6 months after surgery. Brain magnetic resonance imaging (1.5-T) was performed in 53 patients at 6 months after STN DBS. The electrode position was estimated in the fused pre- and postoperative magnetic resonance images and correlated with the surgical results.
Results: As a group, the Unified Parkinson's Disease Rating Scale, Hoehn and Yahr staging, Schwab and England Activities of Daily Living, and Short Form-36 Health Survey scores improved at 3 and 6 months after STN DBS. The L-dopa equivalent dose decreased by 60% at 3 and 6 months after STN DBS. The electrode position was divided into 6 types according to its relationship to the STN and the red nucleus. Most off-medication Unified Parkinson's Disease Rating Scale motor subscale scores improved regardless of the type of electrode position. The off-medication speech subscale score improved only in the patients whose electrodes were correctly positioned in the STN bilaterally.
Conclusion: The electrodes accurately positioned in the STN led to improved speech after bilateral STN DBS. An effort should be made in each patient to document the electrode position to monitor surgical performance and to improve the surgical outcome after STN DBS.