Objective: To investigate the impact of stimulation location on non-motor symptoms (NMS) in PD patients with DBS in the subthalamic nucleus (STN) via an analysis of volumes of activated tissue (VAT).

Background: STN-DBS improves non-motor and motor symptoms. In a recent study, we showed that NMS improvement is higher with a more anterior, ventral and medial position of the active contact, whereas motor symptoms improve more with a more posterior and lateral position of the active contact. However, investigating only electrode locations neglects the spatial extent of electrical stimulation, which also depends on the stimulation parameters. We thus conducted an investigation into the spatial distribution of NMS improvement in the STN using VATs.

Methods: Clinical data was collected from an ongoing prospective, open-label, multicenter study (Cologne, London, Manchester) including 92 patients with bilateral STN-DBS. The following scales were collected at preoperative baseline (MedON) and on follow-up (FU) six months after surgery (MedON/StimON): SCOPA-motor examination (SCOPA-motor), -activities of daily living (ADL), NMSScale (NMSS), NMSQuestionnaire (NMSQ), Hospital Anxiety and Depression Scale-anxiety and depression subscales (HADS-A/-D). Wilcoxon signed-rank test was used to test for significant changes between baseline and follow-up and Bonferroni-correction was applied for multiple comparisons. Individual VATs, based on the stimulation parameters used in clinical setting, were calculated in MNI space (ICBM 2009b) as described elsewhere (1). To analyse the relationship between VATs and change scores, we employed probabilistic stimulation maps and projected them on the DISTAL-Atlas (2).

Results: All outcomes, besides HADS-D, improved significantly at FU. Probabilistic stimulation maps showed higher improvement of NMS for stimulation localized in the limbic and associative STN, whereas motor symptoms improved more for stimulation localized in the motor STN.

Conclusions: Our preliminary results support the finding that the non-motor outcome after DBS may depend on the location of neurostimulation. DBS in non-motor STN subregions was associated with bigger improvement of NMS. The underlying mechanisms and clinical relevance of our results should be investigated in future studies.

References: 1 Horn, A., Reich, M., Vorwerk, J., Li, N., Wenzel, G., Fang, Q.,. . . Fox, M. D. (2017). Connectivity predicts deep brain stimulation outcome in Parkinson’s disease. Ann Neurol. doi:10.1002/ana.24974. 2 Ewert, S., Plettig, P., Li, N., Chakravarty, M. M., Collins, D. L., Herrington, T. M., . . . Horn, A. (2017). Toward defining deep brain stimulation targets in MNI space: A subcortical atlas based on multimodal MRI, histology and structural connectivity. Neuroimage. doi:10.1016/j.neuroimage.2017.05.015.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/non-motor-outcomes-of-subthalamic-dbs-in-pd-depend-on-the-location-of-volume-of-activated-tissue/