Objective: To assess if a horizontal current steering in the subthalamic nucleus (STN) by directional deep brain stimulation (dDBS) offers clinical advantages compared to conventional circular DBS (cDBS).

Background: Today there is some evidence that dDBS may be more advantageous than the cDBS, as it offers more programming flexibility.

Method: We analyzed retrospectively a small cohort (5 males) of Parkinson’s disease (PD) patients, implanted with a dDBS system for bilateral subthalamic stimulation. This dDBS system combines eight-contact directional leads (four electrodes levels, with the two middle levels of tripartite electrodes) and a pulse generator capable of multiple independent current source control (MICC). After a standard monopolar review in ring-mode on all four levels of each lead, the chronical stimulation started using cDBS through the electrodes that proved to be most effective for rigidity control, allowing the largest therapeutic window (TW). If during the subsequent period of parameters adjustment, the TW of a lead proved to be too narrow or null, preventing further motor improvement, a directional review of the contact points of this lead was carried out on the best ring-level. If directional review proved to widen the TW, we switched to dDBS, gradually optimizing the horizontal current steering according to clinical needs.

Results: In all our patients we needed to switch from cDBS to dDBS at least on one lead (in a total of 7 out of 10 leads), because of the threshold of adverse effects (facial muscle contractions, dysarthria, dyskinesia) in the ring-mode setting prevented to optimize motor parkinsonian improvement. On these leads an optimal setting of the horizontal current steering resulted in significantly larger TW, and higher side-effect threshold, which allowed to improve contralateral bradykinesia (5 leads), tremor (2 leads), rigidity (2 leads), gait (3 leads), and eyelid opening apraxia (one lead). During the follow-up (mean 11 ± 3 months from implantation), all 7 leads remained with a directional setting; patients showed a clinical ON-state comparable to the preoperative levodopa challenge and a significant reduction of dopaminergic medication by 68%, without complaining of relevant motor fluctuations.

Conclusion: Our results suggest that horizontal current steering in the STN by dDBS-MICC system may expand the TW compared to cDBS, optimizing the efficacy of DBS in PD patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effects-of-directional-deep-brain-stimulation-of-the-subthalamic-nucleus-in-parkinsons-disease/