Objective: Use deep brain stimulation (DBS)-evoked potentials recorded using dry-EEG electrodes to estimate stimulation outcome.

Background: Subthalamic DBS effectively alleviates motor symptoms in Parkinson’s disease. With the introduction of segmented leads, the parameter space for DBS settings has markedly increased. DBS-evoked potentials (EP) have been proposed as an easily-accessible and non-invasive marker to guide contact selection and programming[1,2]. However, a limiting factor is that mounting conventional EEG systems is time-consuming and may not scale for use in typical outpatient clinic settings. Dry-Electrode systems may be set up in minutes, but have not been tested for use with DBS-EP.

Method: We recorded EP in 24 patients (48 hemispheres) with Parkinson’s disease using a 32-channel dry EEG system. Low-frequency stimulation (2 Hz) was applied at the clinically chosen DBS contact for 10 minutes in each hemisphere. An amplitude map (time x channels) characterizing average EP was created for each hemisphere (Fig. 1) after channels were flipped for recordings with right-sided DBS. For each element of this matrix, amplitudes were correlated with upper limb percentage UPDRS improvements obtained for the same contact under high-frequency DBS across hemispheres, leading to a matrix of correlation coefficients (R-matrix). To validate this matrix, it was subjected to leave-one-out cross-validation: Iteratively, the process was repeated, each time leaving out one hemisphere. The similarity between each hemisphere’s amplitude map and the R-matrix was used to derive an estimate of motor improvement, which was compared with the observed improvement.

Results: Across hemispheres, stimulation evoked three distinct EP at 22, 58 and 138 ms (N20, P60 and P140, see Fig. 1). The R-matrix revealed a lateralized fronto-central N20 and frontal P60 pattern(Fig. 2). In the leave-one-out cross-validation this map estimated significant amounts of variance in the empirical UPDRS improvements (R = 0.38, p = 0.019).

Conclusion: We present a novel DBS EP mapping approach that may potentially be used to identify the optimal pattern of EP by element-wise correlation. Further investigation is needed to test our model’s performance for DBS contact selection. Due to the dry-electrode setup used, results may suggest a promising approach to guide DBS programming during clinical practice.

Figure 1. DBS-Evoked Potentials.

Figure 2. DBS Evoked Potential Mapping Approach.

References: [1] Bahners BH, Spooner RK, Hartmann CJ, Schnitzler A, Florin E. Subthalamic stimulation evoked cortical responses relate to motor performance in Parkinson’s disease. Brain Stimul 2023;16:561–3. https://doi.org/10.1016/j.brs.2023.02.014.
[2] Miocinovic S, de Hemptinne C, Chen W, Isbaine F, Willie JT, Ostrem JL, et al. Cortical potentials evoked by subthalamic stimulation demonstrate a short latency hyperdirect pathway in humans. J Neurosci 2018;38:9129–41. https://doi.org/10.1523/JNEUROSCI.1327-18.2018.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/deep-brain-stimulation-evoked-potentials-as-an-avenue-to-optimize-stimulation-outcomes-in-parkinsons-disease/