Objective: To report a case in which STN stimulation-induced gaze deviation was mapped and managed using directional lead programming.

Background: Deep Brain Stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson’s Disease (PD) has been reported to cause a contralateral gaze deviation in some patients though the pathways involved in this process are not fully understood. Directional programming provides an opportunity to explore the localization of these underlying pathways.

Method: We describe a single patient with PD and bilateral STN DBS where thresholds for stimulation-induced gaze deviation were prospectively mapped out using the St. Jude Infinity directional DBS system.

Results: A 69-year-old woman with a 15-year history of PD underwent bilateral STN DBS using the St. Jude Infinity directional DBS System. During intraoperative bipolar stimulation of the right STN lead, a leftward gaze deviation was observed with higher stimulation of the two dorsal contacts: at 3.0mA for 3-4+ and with 3+4- at slightly lower amplitude. In post-operative follow-up, more in-depth mapping of this phenomenon was explored. With monopolar (omnidirectional) stimulation, a contralateral gaze deviation was again observed using the two dorsal contacts. Directional mapping using the three segments of contact 3 demonstrated a significantly lower threshold for gaze deviation using the lateral segment compared with the posterior segment at 2.5mA and 4.0mA respectively. Eye movements returned to normal immediately upon cessation of stimulation. No contralateral arm or face contractions were noted. Eye movement abnormalities were not observed using the two ventral contacts through 4mA.

Conclusion: This case demonstrates the potential for directional programming to both better elucidate and troubleshoot specific stimulation-induced side effects. In this instance, lateral stimulation had a lower threshold for inducing contralateral gaze deviation when compared to posterior stimulation suggesting the origin of impaired eye movements likely involves secondary activation of the laterally situated internal capsule (IC). Furthermore, that the gaze deviation occurred without noted tetanic contractions would suggest activation of the medial fibers of the IC, which are more associated with the frontal eye fields.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/use-of-directional-stimulation-to-localize-and-troubleshoot-stn-related-contralateral-gaze-deviation-a-case-report/