Emergence of restless legs syndrome after subthalamic stimulation in Parkinson's disease: a dopaminergic overstimulation?

Objective: Studies investigating the effects of subthalamic deep-brain stimulation (DBS-STN) on restless legs syndrome (RLS) in Parkinson's disease (PD) are limited and report conflicting results, with some describing the emergence of RLS after DBS-STN, while others report postoperative improvement of this disorder. Severe decrease in postoperative dopaminergic medications dose, which may unmask RLS symptoms, has been proposed to explain the emergence of RLS after surgery. We aimed to specifically identify factors associated with the risk of developing RLS after DBS-STN in order to enhance our comprehension of the underlying mechanisms contributing to the development of RLS in PD. Patients: In this observational prospective study, we evaluated the occurrence of RLS in 31 patients with PD originally free from RLS symptoms, six months after bilateral chronic DBS-STN, and compared clinical and treatment parameters of patients who developed postoperative RLS with those of patients without postoperative RLS. Results: Six patients out of 31 reported post-operative emergence of RLS. There was no between-group difference in demographic data, pre-operative treatment parameters or clinical improvement measures after DBS-STN. However, PD patients with emergence of RLS after DBS-STN had a higher dose of dopamine agonists at postoperative evaluation compared to PD patients without emergence of RLS (p = 0.040) and a lower percentage of decrease in dopamine agonists (p = 0.043). Conclusion: Overstimulation resulting from cumulative effects of dopamine agonists and STN-DBS may induce changes in excitability of the dopaminergic system, leading to an emergence of RLS. Clinicians should take into account this phenomenon while adjusting pharmacological treatment after surgery. (C) 2014 Elsevier B.V. All rights reserved.