Bilateral effects of unilateral subthalamic nucleus deep brain stimulation in advanced Parkinson's disease.

To investigate the bilateral effects of unilateral subthalamic nucleus deep brain stimulation (STN-DBS), we prospectively studied 9 consecutive advanced Parkinson's disease (PD) patients (2 men and 7 women) who underwent unilateral STN-DBS. Patients were evaluated preoperatively and at 3 and 6 months postoperatively with and without dopaminergic medications ('on' and 'off' medication, respectively). Postoperatively, patients were assessed with and without stimulation. We found that, when compared with baseline, the 'off' medication scores of the Unified Parkinson's Disease Rating Scale motor part (UPDRS III) and activities of daily living (UPDRS II) were improved by 37% (p = 0.028) and 50% (p = 0.046) at 6 months after surgery, respectively. Stimulation while 'off' medication improved the total UPDRS score by 42% (p = 0.028) at 6 months. At 6 months after surgery, the subscore of UPDRS III of body parts contralateral to the DBS implantation had improved by 48% (p = 0.028), and the ipsilateral subscore of UPDRS III and the axial subscore of UPDRS III had improved by 20% (p = 0.027) and 39% (p = 0.028), respectively. Daily dosage of levodopa was reduced by 15% at 6 months. No patient exhibited permanent side effects. These findings indicate that unilateral STN-DBS may be a reasonable surgical procedure for selected PD patients who have markedly asymmetric parkinsonism.