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

Eighty Hertz vs. 130Hz 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 80Hz vs. 130Hz frequency on cortical excitability and bradykinesia. 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 80Hz or 130Hz 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. Both frequencies of stimulation improved distal bradykinesia to an equal extent. However, 80Hz was less effective than high frequency stimulation in normalising SICI, however, bradykinesia of proximal arm/shoulder movements was improved more by 80Hz compared to 130Hz. Stimulation of STN at 80Hz and 130Hz 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 80Hz is more effective in improving proximal muscle function.