Objective: To provide a proof of concept of correlating LFPs to EMG during multi tasks in PD subtypes.

Background: Evidence highlights the unique contributions of the rZI and STN to disease profile and therapeutic benefit in DBS for PD. Differences in EMG and LFPs coherence of the rZI and STN differ during task performance (1). The contributions of rZI and STN afferent and efferent connections have also been described in akinetic rigid PD patients (2). DBS activation of these two targets results in unique clinical efficacy for improvement of rigidity, bradykinesia, and tremor; such as rigidity may improve best with stimulation in the region of the rZI while tremor may improve best with stimulation within the STN (3). Despite these findings, further research is warranted to better understand the physiology of the rZI and STN and their unique contribution to pathophysiology in PD.

Method: Standard microelectrode recordings (MER) was used to target STN (average 3 electrodes). During MER, LFP were recorded from the rZI, dorsal and ventral borders of the STN. These regions were predetermined on MRI and confirmed by MER. EMG electrodes were attached to forearm muscles. Patients performed tasks of the arm contralateral to DBS implanted side while recording was obtained at each of the predetermined locations: rest, flexion of arm and supination of forearm, flexion of arm and pronation of forearm, flexion of arm and flexion forearm at elbow, and finger to chin task. Each task was performed three times each with a duration of 20 sec.  Analysis was performed offline and included correlation of LFP to EMG for each task and muscles activated, comparison of the differences between the coherence LFP to EMG for the rZI, dorsal and ventral STN.  Confirmation of placement of the DBS electrode was made by post-operative MRI with optimized imaging to visualize the rZI.

Results: Preliminary data indicate differences in the strength of correlation of LFP to EMG for all muscles and with different tasks. Overall, 3 muscles (FCR, ECR, and FCU) showed significant differences in coherence between the STN and rZI on 4 tasks. Further analysis is underway including analysis of PD subtypes.

Conclusion: This promising pilot data demonstrates differences in the coherence of LFP to EMG between the rZI and the STN which appears to depend upon the muscles tested and tasks performed.

References: 1. Reck C et al. Eur J Neurosci. 2009;29:599-612. 2. Florin et al. Eur J Neurosci. 2010;31:491 – 498. 3. Akram H, et al. NeuroImage. 2017 (158):332-345.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/correlation-of-local-field-potentials-lfps-to-electromyography-emg-of-the-rostral-zona-incerta-rzi-and-subthalamic-nucleus-stn-in-parkinsons-disease-pd/