Effect of STN-DBS frequency on cortical excitability and motor performance in Parkinson's disease

Abstract

Introduction Eighty Hertz vs. 130 Hz stimulation have a different effect on axial symptoms in some patients on chronic subthalamic nucleus (STN) deep brain stimulation in patients with Parkinson's disease (PD). This could be linked to a direct effect of the frequency of stimulation on the STN itself, and indirectly measured by means of transcranial magnetic stimulation. Our goal is to evaluate the effect of 80 Hz vs. 130 Hz frequency on cortical excitability and bradykinesia. Material and methods We conducted a double-blind crossover study in 15 patients with advanced PD treated with DBS for at least 6 months. Mean ± SD age was 63.3 ± 6.6 years and disease duration 15.5 ± 5.2 years. The time since surgery was 4.45 ± 3.9 years. The patients were stimulated with 80 Hz or 130 Hz randomly for 3 weeks and then switched to the other frequency for 3 more weeks. Adjustments of voltage were made according to the best clinical effect. Cortical excitability was measured in the first dorsal interosseous muscle with Short intracortical inhibition (SICI). In total, the patients were assessed 6 times. Proximal and distal movement task were also assessed. Results Both frequencies of stimulation improved distal bradykinesia to an equal extent. However, 80 Hz was less effective than high frequency stimulation in normalising SICI, however, bradykinesia of proximal arm/shoulder movements was improved more by 80 Hz compared to 130 Hz. Conclusions Stimulation of STN at 80 Hz and 130 Hz may have different effects on proximal and distal muscle control. One hundred and thirty Hertz may have a small advantage for distal hand muscles, whereas 80 Hz is more effective in improving proximal muscle function.