gms | German Medical Science

Objective: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson’s disease allows for the recording of local field potentials (LFPs) in this part of the basal ganglia. Such recordings are of great interest since they may serve as possible biomarkers for the current "physiological status" of the patient and thus might be used for "sensing" and consecutive adaptive stimulation ("closed-loop DBS").

Methods: 38 Parkinson-patients (mean age 60.1 years (range 47-71), 11 female/27 male, mean disease duration 11.6 years (range 7-20) having undergone STN-DBS were included. LFP-recordings were performed via externalized leads in all patients. Recordings were done with the patient in a recumbent position during rest (awake patient, eyes open), during right/ left hand opening and closing (frequency 2/s; 5 min.), during standing for 5 min, slow walking 30 m and fast walking 30 m. LFPs were amplified, recorded and digitally stored (resolution 0.1 µV, sampling rate 2000 Hz, filter 0.1 Hz – 500 Hz). Raw data were high-pass filtered (3rd order Butterworth, 1 Hz) and resampled to a sampling frequency of 422 Hz. The fast Fourier algorithm of Malta and averaging the resulting spectra were used to compute the frequency spectrum of all data.

Results: Fifty-one of 76 (67.1%) recordings had one peak, eight (10.5%) recordings showed two peaks, and 17 (22.4%) recordings showed no peak. Movement of either hand did not reliably suppress beta peaks. Walking reduced the peaks in the high beta band (above 20.2 Hz) but not the peaks in the low beta band.

Conclusion: Beta-peaks can be detected in a high percentage of LFP-recordings using DBS-electrodes. Beta suppression caused by movement is dependent on the type of movement and the frequency of the peak. Further studies should consider the fact that the beta frequency band may host different physiological processes - that might be suitable biomarkers for "adaptive DBS".