Deep Brain Stimulation in Parkinson Disease: A Switch for On/Off Dystonia

Background: Dystonia is common in Parkinson disease patients, affecting about 30% of them. Bilateral subthalamic nucleus deep brain stimulation (DBS) can sometimes lead to dystonia, but this relationship is not well understood. Our aim was to provide a better understanding of dystonia's causes and its connection to DBS. Methods: We conducted a retrospective analysis of clinical data from 80 Parkinson disease patients who underwent bilateral subthalamic nucleus stimulation, focusing on dystonia before and after surgery and its relation to medication state (on-dystonia/off-dystonia). Results: After DBS, off-dystonia had a higher recovery rate than on-dystonia (43.5% vs. 9.1%). Among patients suffering for on-dystonia, 74.4% had it for the first time after surgery; these patients assumed higher doses of levodopa before DBS. Conclusions: Patients with off-dystonia before surgery tend to improve after DBS. Otherwise, DBS could have the role of “additive boost” in the process of sensitization of striato-pallidal pathways and lead to on-dystonia in particular patients.