Objective: To compare bipolar sensing (BS) with monopolar sensing (MS) of local field potentials (LFP) within the beta band of subthalamic nucleus (STN) in Parkinson’s disease (PD).

Background: In PD, LFP within the beta frequency of (13-30Hz) particularly in the lower range (13-20Hz) is an established real-time biomarker. Current deep brain stimulation (DBS) programming allows for sensing along the electrode using bipolar pairs. Interpretation of bipolar sensing (BS) to identify where the LFP beta signal is strongest can often be subjective and challenging. A novel use of monopolar sensing (MS) may eliminate potential discrepancies. Using the maximum peak identified in low beta (13-20Hz), we compared the putative optimal contact levels derived from the two sensing configurations. We hypothesized that one of the BS pairs would correspond to the contact(s) of MS.

Method: Ten PD patients (4F/6M, post diagnosis = 9.2 ± 3.5 years) with bilateral STN DBS (n=20 hemispheres) implanted with 1-3-3-1 segmented lead and sensing capable neurostimulator were recruited. Sensing analysis was performed by identifying the segment and level of contacts that corresponded with the greatest beta peak within the lower frequency range. Collecting both MS and BS configurations enabled a unique opportunity to investigate how the contact selected with bipolar sensing information compared to easier to interpret monopolar results.

Results: Final BS configurations were the following adjacent pairs (N=6), single level between pairs (N=12), and two levels between pairs (N=2). Regarding level, the MS level corresponded with between the BS pairs 10% and was a contact of one of the BS pairs 90%. Final BS configurations for segment pairs were the following horizontal pairs (n=1) and vertical pairs (n=19). Regarding segment, the MS segment corresponded with one of the contacts of the BS pairs 95% of the time.

Conclusion: This study expands upon MS being easier to interpret for selecting the therapeutic contact. Users with access to only BS, must interpret whether the LFP beta signal is strongest between or on one of the sensing contacts. We show the contact with the greatest LFP beta signal is commonly one of the bipolar sense pairs and not the contact between the sensing pairs. This could help inform potential future algorithms or approaches to contact selection using BS information.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/comparison-of-monopolar-and-bipolar-sensing-of-beta-frequency-in-parkinsons-disease-of-the-subthalamic-nucleus-for-deep-brain-stimulation/