Objective: To describe distinctive acute behavioral changes that occurred during monopolar review in PD patients implanted with DBS directional leads, operated consecutively over 12 months.

Background: Psychiatric adverse events (AEs) are the second most common type during deep brain stimulation (DBS). Directional leads for DBS are a recent advance in movement disorders such as Parkinson’s disease (PD). Their segmented structure allows current steering, which can shape stimulation and potentially optimize clinical benefits while minimizing AEs.

Method: Preoperative screening of 23 PD patients indicated no psychiatric history, cognitive scores ≥25/30, and depression score ≤ 16 (BDI). Identification of probable spots responsible for the AEs and visualization of the STN-associated anatomical pathways i.e. white matter tracts (WMTs) and the volume of tissue activated with the settings that caused behavioral changes were determined using preoperative MRI, DTI, postoperative CT, Brainlab Elements, and Guide™ XT.

Results: During postoperative monopolar review, four patients presented behavioral AEs with severity varying between and within each patient. Stimulating distal contacts mostly resulted in acute sleepiness. Gradually moving stimulation to higher contacts resulted in various behavioral manifestations (e.g., hyperemotional crying, uncontrolled laughter, disinhibition), but spontaneous euthymia when stimulating at proximal contacts. AEs were more intense when stimulating the right side. The images obtained indicated that the distal contacts and part of the first level of the segmented electrode were located in the substantia nigra and in the vicinity of WMTs.

Conclusion: Contact-dependent behavioral symptoms are possible and certain DBS settings may cause reproducible and radically different behavioral changes. The mechanism behind these phenomena is currently unclear, but the substantia nigra and/or WMTs seem to be implicated.  Further studies are needed to clarify our observations.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/acute-contact-dependent-behavioral-changes-in-parkinson-disease-pd-patients-during-monopolar-contact-review-of-subthalamic-deep-brain-stimulation-dbs-using-directional-leads/