Assessment of the effects of unilateral electrode dysfunction in patients with parkinsons disease undergoing bilateral STN-DBS

BACKGROUND: Bilateral subthalamic nucleus deep brain stimulation (STN-DBS) is the gold standard surgical treatment for medically intractable Parkinsons disease (PD), and unilateral electrodes are reported to have beneficial effects. However, assessment of patients after electrode failure needs to be established. OBJECTIVE: To assess the effects of the remaining unilateral electrode in PD after bilateral STN-DBS. METHODS: Between May 2000 and March 2009, eight patients encountered unilateral STN-DBS after bilateral STN-DBS. We assessed clinical outcome by comparing the Unified Parkinsons Disease Rating Scale (UPDRS) motor score, activities of daily living (ADL), levodopa equivalent daily dosages (LEDD), and quality of life (QOL) according to the short-form 36 health survey between patients with unilateral and bilateral electrodes. RESULTS: Although ipsilateral and axial UPDRS motor scores were compromised, UPDRS motor scores contralateral to the side of the implant remained unaltered after removal of one electrode. Although physical aspects of QOL declined significantly with a unilateral electrode, pain and social functioning were not significantly affected. No significant changes in ADL, Hoehn and Yahr stage, or LEDD were observed after removal of one electrode. CONCLUSION: The UPDRS motor score with unilateral STN-DBS was compromised relative to bilateral STN-DBS for ipsilateral motor and axial symptoms. When one electrode is compromised, revision of that electrode will eventually be required, but not immediately in all patients. If a patient tolerates loss of one electrode according to motor score while maintaining ADL and QOL, it is possible to wait and observe the situation instead of immediately revising the electrode.