Contralateral Subthalamic Nucleus Beta Suppression in Response to Increased Ipsilateral Deep Brain Stimulation in Parkinson Disease

Introduction: Subthalamic nucleus (STN) local field potentials (LFPs) from individuals who have Parkinson Disease (PD) are characterized by abnormal oscillations in the beta frequency band, ranging from 15-30 Hz. Suppression of beta oscillations by levodopa or by deep brain stimulation (DBS) is correlated with improvement of bradykinesia and rigidity symptoms. Beta suppression from unilateral STN-DBS is typically observed in the ipsilateral STN. However, there is growing evidence that the subthalamic nuclei are interconnected, with unilateral STN-DBS reported to modulate contralateral STN single-unit recordings in 8 participants (Walker 2011) and LFPs in 14 participants (Hasegawa 2020). We report a new series of seven individuals who demonstrate contralateral beta suppression with STN-DBS.

Methods: Bilateral STN LFPs were recorded from individuals with DBS systems with recording capability during routine programming visits from May 2022 to June 2023. Individualized beta peaks were identified in each STN from resting state recordings. Continuous wavelet transforms were used to generate time-frequency signal representations. Beta amplitude was calculated from a 5Hz-wide band centered on the beta peaks and averaged over periods of constant stimulation amplitude.

Results: Seven patients, all right-handed, out of a cohort of fourteen had marked beta amplitude decreases of ≥5dB (corresponding to reduction by a factor of ~3.16) in the contralateral STN after increasing the stimulation amplitude of the ipsilateral STN.

Conclusion : These findings contribute to the evidence that unilateral STN-DBS modulates bilateral STN networks. Further analyses are needed to understand whether this is a patient-specific effect, whether it depends on handedness or side of initial PD symptoms, or whether it is location-dependent within the STN. Furthermore, understanding this phenomenon may affect how DBS is utilized — individuals exhibiting strong bilateral STN modulation to DBS of one STN may not require as high of a stimulation amplitude on the opposite side.