80 Hz versus 130 Hz subthalamic nucleus deep brain stimulation: effects on involuntary movements.

Background: Subthalamic Nucleus Deep Brain Stimulation (STN-DBS) represents a valid therapeutic option for advanced Parkinson’s disease (PD), leading to a significant amelioration of motor fluctuations and levodopa-induced involuntary movements (IM). This study address the issue of whether stimulation frequency may influence the control of IM in STN-DBS treated patients, comparing the effects of 80 Hz and 130 Hz STN-DBS frequencies in 10 parkinsonian patients with residual IM (dyskinesia in 6 cases and dystonia in 4 cases). Methods: Patients were evaluated by means of the Rush Dyskinesias Rating Scale (blinded-video analysis) and Unified Parkinson’s Disease Rating Scale at 4 different time-points: baseline, shortly after the switch of stimulation frequency from 130 Hz to 80 Hz, after 1 month and 12 months of chronic 80 Hz stimulation. Results: IM improved in most subjects after the switch of stimulation frequency: dyskinesias improved in 6/6 subjects and dystonic features in 3/4 subjects after one month of 80 Hz stimulation. However, the 130 Hz STN stimulation was restored in 4 subjects during the following months, because of a gradual worsening of parkinsonian symptoms. A sustained efficacy on motor features and IM was observed with 80 Hz stimulation frequency in the remaining patients. Conclusions: In this limited cohort of STN-DBS patients, we observed an improvement of residual IM after the switch of stimulation frequency from 130 Hz to 80 Hz. However, a moderate worsening of parkinsonian symptoms was observed in a portion of patients, requiring to return at 130 Hz STN-DBS.