Objective: To describe oscillatory patterns of pallidal local field potentials (LFP) in fully implanted patients with dystonia. ​​​

Background: New implantable devices for deep brain stimulation (DBS) are capable of recording the activity of the implanted target simultaneously to stimulation. These devices can potentially operate by adapting the stimulation parameters in response to the recorded neural signals (adaptive DBS, [aDBS]). The identification of reliable biomarkers of pathological activity is critical for the development of aDBS paradigms. DBS of the globus pallidus pars interna (GPi) is a mainstay treatment for drug-refractory dystonia. Recent studies associated exaggerated theta oscillations in the GPi, recorded with externalized electrodes, to dystonic symptoms. Results should be confirmed in fully implanted patients.

Method: We recorded bilateral LFP of the GPi from the chronically implanted DBS leads (3389, Medtronic PLC) in four dystonic patients (two with cervical and two with myoclonus dystonia) with the new device Percept PC. Recordings were acquired bilaterally for 22 seconds from all non-adjacent contact pairs (0-3, 1-3, 0-2, with 0 and 3 being the lowermost and uppermost contact). Bipolar combinations of adjacent contacts (0-1, 1-2, 2-3) were obtained by subtracting channels. Patients were evaluated after switching off the stimulation for at least 12 hours. We computed the power spectral density (PSD) of each recording pair with the Welch’s method and removed the 1/f component. PSD were normalized for the standard deviation calculated in the 6-96Hz band and inspected for theta peaks and movement artefacts.

Results: The eight GPi analyzed showed exaggerated theta activity in 45 out of 48 recording pairs. The most prominent theta peak among recording pairs was centred at 5.7 ±2.1Hz. One patient also showed a sharp beta peak at 20Hz. Of relevance, recordings exhibited considerable artefacts due to transient motor symptoms (i.e., dystonic and myoclonic jerks).

Conclusion: We confirmed the presence of exaggerated theta activity in pallidal LFP recordings in fully implanted dystonic patients. This finding prompts further studies of this biomarker for aDBS paradigms in dystonia. The impact of motion artefacts on the quality of the recordings should be carefully considered. In this regard, longer recordings might provide a more accurate PSD estimation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/pallidal-recordings-in-fully-implanted-dystonic-patients-preliminary-results/