Background Pallidal deep brain stimulation (DBS) has shown to be beneficial in patients with advanced levodopa-responsive Parkinson's disease (PD) in several short-term studies. However, reported long-term outcomes of pallidal DBS for PD are limited and contradictory. Methods Eighteen consecutive PD patients were treated with unilateral or bilateral stimulation of the internal part of the globus pallidus (GPi). Assessments were carried out before and six months after neurosurgery, and annually thereafter for up to 16 years (mean follow-up time: 6 years). Primary outcomes included motor signs (Unified PD Rating Scale [UPDRS]-III), activities of daily living (ADL, UPDRS-II), and levodopa-induced motor complications (UPDRS-IV). Results The results show that GPi stimulation improves levodopa-responsive PD motor signs (UPDRS-III), levodopa-induced motor complications (UPDRS-IV), and ADL (UPDRS-II) in advanced PD. Among motor signs, tremor showed the best response to pallidal stimulation. Levodopa-induced motor complications and tremor showed improvements for more than 10 years after neurosurgery. Conclusions The overall findings in our cohort demonstrate that pallidal stimulation is effective in reducing parkinsonian motor signs (UPDRS-III), particularly in the ‘off’-medication state. Although the beneficial effects on bradykinesia, rigidity and ADL may be limited to 5–6 years, the follow up results indicate that the improvements of levodopa-induced motor complications (UPDRS-IV) and tremor can be sustained for more than 10 years.
