We aimed to evaluate the long-term effects of STN-DBS surgery on PIGD symptoms and factor related to the outcome in patients with advanced-stage PD.

High-frequency deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a well-established surgical therapy for patients with advanced Parkinson’s disease (PD) with motor complications that are no longer adequately managed with medication. In addition, the consensus guideline for selection of patients who will likely have a successful outcome after DBS has been established.  However, the long-term effects of bilateral deep brain stimulation of the subthalamic nucleus (STN-DBS) on postural instability and gait disturbance (PIGD) in patients with Parkinson's disease (PD) remain unclear.

This study was retrospective and observational study.  We retrospectively reviewed 49 consecutive PD patients who underwent bilateral STN-DBS at Asan Medical Center, Seoul, South Korea. Unified Parkinson's Disease Rating Scale (UPDRS) scores and sub-scores for PIGD were assessed at baseline and at 1, 3, and 5 years postoperatively. The PIGD sub-score was divided into PIGD-motor and PIGD-activity of daily living (ADL) scores according to UPDRS part III and II, respectively.

PIGD-motor and PIGD-ADL scores at 'medication-off' state improved up to 3 years and 5 years, respectively. Overall, UPDRS-III and II scores at 'medication-off' improved up to 5 years. The dyskinesia score in UPDRS IV was also significantly improved at all follow-up periods. Finally, the PIGD-motor score at baseline, and amount of improvement in the PIGD-motor score at 1-year follow-up, predicted longterm improvement of this score at the 5-year follow-up.

STN-DBS has both short and long-term effects on PIGD, as well as overall motor function in patients with advanced PD. The degree of PIGD at preoperative evaluation may predict the long-term outcome of STNDBS surgery.