Objective: To describe five cases of deep brain stimulation (DBS) implants in the caudal zona incerta (cZI) for the treatment of tremor at the University of Kentucky. We plan to include detailed imaging and DBS settings analysis in the final poster.

Background: Dysgeusia, or altered taste perception, is a documented side effect of DBS, especially when targeting thalamic regions. The cZI, a part of the subthalamic region, lies ventral to the thalamus and dorsal to the subthalamic nucleus (STN) within the posterior lateral hypothalamus. As an emerging DBS target for essential tremor (ET), the cZI offers therapeutic benefits but can lead to rare yet significant side effects. This case series highlights dysgeusia as a lesser-known but impactful consequence of cZI DBS for tremor.

Method: Cases were evaluated through chart review.

Results: We describe five patients (four males and one female) who underwent Boston Scientific DBS implantation in the cZI for tremors. One of these patients also had ipsilateral GPi lead placement for cervical dystonia therapy. Each patient reported experiencing a metallic, sour, or copper taste; one patient had hyposmia, and two patients experienced loss of appetite with weight loss. All five patients underwent stimulation adjustments, resulting in complete or near-complete resolution of dysgeusia in four patients. One patient, who had refractory symptoms despite several adjustments—including turning off the leads—required explantation of one lead to completely resolve dysgeusia. Additionally, one patient with ET and cervical dystonia had leads in the left GPi and left cZI. Turning off the left cZI lead completely resolved the dysgeusia.

Conclusion: These findings suggest that cZI-DBS may influence sensory pathways, likely through unintended stimulation of the VPM thalamic nucleus, leading to dysgeusia. Careful lead placement and parameter adjustments are crucial to minimizing sensory side effects. This case series highlights the importance of neuroanatomical knowledge for programmers enabling them to proactively identify and address dysgeusia during DBS programming.

References: Carlson, J. D., McLeod, K. E., Mark, J. B., McLeod, P. S., & Bremer, B. A. (2018). Dysgeusia in deep brain stimulation for essential tremor. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia, 50, 242–246. https://doi.org/10.1016/j.jocn.2018.01.013

Swinnen, B. E. K. S., Bot, M., Goes, K. M., Beudel, M., Schuurman, R. P., & de Bie, R. M. A. (2022). Directional stimulation improves stimulation-induced dysgeusia in DBS for essential tremor. Brain stimulation, 15(3), 680–682. https://doi.org/10.1016/j.brs.2022.04.016

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MDS Abstracts - https://www.mdsabstracts.org/abstract/exploring-dysgeusia-after-czi-dbs-implantation-for-tremor-control-insights-from-a-case-series/