Objective: The aim of the current study is to characterize spontaneous pallidal neuronal activity in patients with Pakninson’s disease (PD) and dystonia with different clinical outcomes from deep brain stimulation (DBS).

Background: Globus pallidus internus (GPi) is well known surgical target for DBS treatment of both PD and dystonia patients. Despite the effectiveness of this treatment, in some cases the DBS outcome remains quite low. We have previously showed a negative correlation between firing rate of pallidal cells and clinical effect in patients with cervical dystonia [1].

Method: We assessed 10 patients with PD and 12 with generalized dystonia (GD) who underwent implantation of DBS electrodes in globus pallidus (GPi). Spontaneous single-unit activity was recorded by means of microelectrodes in awake state. We performed estimation of the volume of activated tissue (VAT) based on the actual therapeutic stimulation parameters in Lead-DBS toolbox. Then we performed multiple regression analysis of single unit activity parameters in VAT with the stimulation effect assessed by a neurologist.

Results: We showed that VAT cells were  characterized by regular high frequency activity with median firing rate 80 spikes/sec and coefficient of variance 0,89 in PD and low frequency irregular activity with median firing rate 45 spikes/sec and coefficient of variance 1,1 in GD.  Multiple regression analysis showed strong correlation between VAT pallidal activity and DBS outcome in both PD (R=0,66; p<0,03) and GD (R=0,5; p<0,006) groups. The most significant features of pallidal activity were entropy and local variance, which reflect randomness of interspike intervals (ISI). Additionally we found significant contribution of burst spike percent in PD, and asymmetry index (median/mean ISI) with percent of ISI larger mean in GD. These parameters characterize the burstiness of the neural activity pattern in the stimulation area.

Conclusion: Our results showed that randomness and bursting of pallidal spiking activity are most important features which correlates with clinical outcome from DBS surgery in Parkinson’s disease and dystonia. These data also suggest that single unit activity may have predictive potential for enhancing DBS efficiency. 

The study was funded by Russian Science Foundation (RSF), project number 23-15-00487.

References: [1] Sedov, A., Popov, V., Gamaleya, A., Semenova, U., Tomskiy, A., Jinnah, H. A., & Shaikh, A. G. (2021). Pallidal neuron activity determines responsiveness to deep brain stimulation in cervical dystonia. Clinical Neurophysiology, 132(12), 3190-3196.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/randomness-and-bursting-of-pallidal-spiking-activity-correlates-with-dbs-outcome-in-parkinsons-disease-and-dystonia/