Objective: In this study, we show feasibility of a novel embedded closed-loop DBS (CL-DBS) that uses local field potential (LFP) oscillations of the alpha/beta band (8-30 Hz) of the Vim for movement-mediated stimulation delivery.

Background: Essential tremor (ET) is a hyperkinetic disorder that manifests as kinetic tremor, and is one of the most common neurological disorders. Deep brain stimulation (DBS) of the ventral intermediate nucleus (Vim) in open loop setting is a common therapeutic strategy for ET. Since tremor is typically not present at rest, continuous stimulation is unnecessary and induces side-effects such as speech impairment, as well as premature depletion of the battery.

Method: In addition to the clinically therapeutic depth lead, a cortical strip was placed on the primary motor cortex. We recorded movement-related modulations from the cortical strip (CL-C) and the depth lead (CL-V) separately, delivering stimulation only during movements with the Medtronic RC+S pulse generator. To determine feasibility, movement tasks (goal-directed motions of the upper limbs), and holding tasks (maintaining position against gravity) were tested. The frequency band was chosen using a Fisher discriminant analysis on spectral components of a cued movement task, and was within the alpha/beta bands [8-30 Hz]. Embedded on the RC+S is a linear discriminant analysis classifier that allows for a single threshold to be specified.

Results: Using data collected in a single subject we show consistent performances using real-time power bands to drive a closed-loop paradigm. In [figure1], all postoperative scores, including CL-V, showed a decrease in the Tremor Rating Scale (TRS) compared to baseline. Closed-loop paradigms performed as well or better than no stimulation, similar to previous work [1]. CL-C showed an average accuracy (mean±std%) during movement tasks of 80±7%, with holding tasks showing 57±5% for accuracy.

Conclusion: Serving as a proof of concept, we have shown that the depth lead alone has the potential to be used as a source for a viable control-policy for a chronic closed loop DBS device (RC+S). Translating these results to a broader population could decrease the number of battery replacement surgeries required, while maintaining efficacy of tremor control.

References: [1] E. Opri et al., “Chronic embedded cortico-thalamic closed-loop deep brain stimulation for the treatment of essential tremor,” Sci. Transl. Med., vol. 12, no. 572, p. 7680, Dec. 2020, doi: 10.1126/SCITRANSLMED.AAY7680.

« Back to MDS Virtual Congress 2021

MDS Abstracts - https://www.mdsabstracts.org/abstract/closing-the-loop-on-essential-tremor-using-thalamic-and-cortical-control-signals/