Objective: To evaluate the contribution of motor speech, language, and cognition to communication changes after subthalamic nucleus deep brain stimulation (STN-DBS) in people with Parkinson’s disease (PwPD), and to determine which STN regions are associated with these changes.

Background: Approximately half of PwPD report worsening communication after STN-DBS. However, the mechanisms driving these changes remain unclear. These can be conceptualized in terms of 1) which subsystem of verbal communication is affected, and 2) what networks modulated by DBS contribute to these changes. Understanding these mechanisms may improve clinical management and clarify the neural circuits supporting communication.

Method: We conducted a prospective study evaluating PwPD before and after STN-DBS. Thirty-four participants completed a comprehensive assessment of motor speech, language, and cognition at both time points. Functional communication was assessed with the Communicative Participation Item Bank (CPIB), which classified participants as showing communication decline or stability/improvement. Measures were adjusted for demographic characteristics when available. Mann-Whitney U tests compared changes from pre- to post-DBS between groups.

Lead-DBS software reconstructed lead locations and evaluated associations between stimulation sites and communication change. MNI coordinates were converted to the CIT168 atlas, and pathway-level stimulation was estimated using the Subthalamic DBS Map.

Results: Participants with communication decline showed faster motor speech rates, including alternating motion rates (U=11, p=.015) and sequential motion rates (U=9.5, p=.008). They also showed greater reductions in category fluency and longer response times on inhibition tasks, although these differences were not statistically significant. Stimulation of the anterior left STN was associated with declines in CPIB scores. Stimulation extending into the superior internal capsule was also associated with worse communication. Among patients with a left-sided lead, greater stimulation of the prefrontal hyperdirect pathway was significantly associated with CPIB decline (p<0.05).

Conclusion: Nearly half of PwPD reported worsening communication after STN-DBS. Improvements in motor speech speed may paradoxically impair functional communication. Stimulation of the anterior STN region and the hyperdirect pathway is associated with reduced communication impairment.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/verbal-communication-after-subthalamic-nucleus-deep-brain-stimulation/