Objective: The aim of this study was to investigate the stability of beta oscillations (13 – 30 Hz) in the subthalamic nucleus (STN) of patients with Parkinson’s disease over a time period of up to 8 months after implantation of subthalamic deep brain stimulation (STN-DBS) electrodes.

Background: Based on the assumption that subthalamic beta activity is a reliable correlate of bradykinetic – rigid symptom severity in patients with PD, adaptive DBS using increased beta oscillations as a stimulation trigger, has been compared to conventional continuous stimulation with promising results. However, evidence so far has solely been derived in a short postoperative interval. A new implantable impulse generator (Activa PC+S, Medtronic, Natick, MA) is now capable to record subthalamic LFP even months after surgery.

Methods: Rest recordings from 12 PD patients (4 f; mean age: 63.2 years; range 56 to 72 years) were conducted using the chronically implanted Activa PC+S under ON and OFF medication conditions at baseline, 3 months and 8 months post implantation. UPDRS scores were obtained for all patients at each time point. Power spectra were calculated using fourier transform based methods. All power spectra were normalized to the percentage total power of the spectrum. Spearman’s correlations were conducted to investigate a potential association of beta power and clinical symptom severity.

Results: Power spectra averaged across all contacts in all subjects showed distinct peaks in the beta band at 3 and 8 months follow up but not at baseline. This was partly due to a wide spread of peaks within the 13-35 Hz band. The peak amplitude of the beta peak OFF medication was similar for all three time points (p>0.3) and was significantly suppressed by levodopa medication (p < 0.001). Moreover, beta peak power OFF medication correlated with individual UPDRS-III scores across time (r= 0.47, p= 0.0017).

Conclusions: Our study shows that oscillatory activity in the beta frequency band can be recorded chronically via the implanted pulse generator and beta power remains stable over a time period of 8 months of DBS and is correlated with the clinical symptom severity across all time points (albeit a partial initial suppression that might be due to the stun effect). Moreover, a significant suppression of beta activity by antiParkinsonian medication could also be shown months after electrode implantation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/long-term-recordings-of-subthalamic-ocillatory-activity-in-patients-with-parkinsons-disease/