The effect of the surgical site of Deep Brain Stimulation (DBS) on balance and gait in Parkinson’s Disease (PD) is uncertain. This is the first double-blind study of subjects randomized to either the Subthalamic Nucleus (STN, N=14) or Globus Pallidus interna (GPi, N=14) who were assessed on a range of clinical balance measures.

Balance testing occurred before and 6 months post-surgery. A control PD group was tested over the same time period without surgery (N=9). All subjects were tested on and off medication and DBS subjects were also tested on and off DBS. The Postural Instability and Gait Disability items of the Unified Parkinson’s Disease Rating Scale and additional functional tests we call the Balance and Gait scale were assessed. Activities of Balance Confidence and Activities of Daily Living questionnaires were also recorded.

Balance was not different between the best-treated states before and after DBS surgery for both sites. Switching DBS on improved balance scores and scores further improved with medication compared to the off state. The GPi group showed improved performance in the post-surgery off state and better ratings of balance confidence after surgery compared to the STN group.

Clinical measures of balance function for both the STN and GPi sites showed that balance did not improve beyond the best medically-treated state prior to surgery. Both clinical balance testing in the OFF/OFF state and self-reported balance confidence after surgery showed better performance in the GPi than the STN group.