Objective: To identify deep brain stimulation (DBS)-related disruption of the subthalamic nucleus (STN)–temporal network as a possible source of STN-DBS induced dysarthria.

Background: STN-DBS often exacerbates dysarthria in patients with Parkinson’s disease (PD). A theta-alpha network exists between the left STN and the temporal cortex (1), possibly subserving speech related functions (2). Its disruption may contribute to DBS-related dysarthria.

Method: For this interim analysis, 10 PD patients with STN-DBS were evaluated 6 months after implantation. Each underwent EEG recording and local field potential (LFP) telemetry in DBS-ON and DBS-OFF conditions, both OFF-medications. Recordings were performed at rest (5 minutes), and during vocalization and a compensation paradigm (3). Here, speech components corresponding to laryngeal (pitch, F0) and posterior tongue (first formant, F1) position were altered during vocalization, and participants’ compensation to the perceived mispronunciation was recorded. Areas of high coherence in the theta–alpha range with the STN were first identified at rest and then tracked during vocalization and in the speech compensation response window.

Results: One patient was unable to complete the task and was excluded. Vocal analysis showed appropriate compensation for F0 in both DBS-ON and DBS-OFF conditions, and for F1 only in DBS-OFF. Resting-state theta–alpha coherence was primarily localized to centro-frontal and left temporal sensors. In DBS-OFF, we observed a tendency for increased coherence at 5 Hz in the temporal sensors during vocalization and F1 perturbation, and a tendency for decreased coherence in the frontal ones during F0 perturbation. These changes were not present in DBS-ON.

Conclusion: In this preliminary analysis, DBS appeared to negatively affect compensation for perceived F1 errors. In the DBS-OFF state, vocalization and F1 compensation seemed to be associated with increased theta coherence between the left STN and temporal sensors, whereas F0 compensation was linked to decreased theta coherence to the frontal ones. Interestingly, DBS seemed to suppress temporal coherence during the task and vocalization, suggesting a detrimental effect of stimulation on speech-related network activation. Further recruitment and correlation with clinical outcomes might confirm this as a mechanism for DBS induced dysarthria.

References: 1.Litvak et.al, 2011
2.Vissani et.al, 2024
3.Mollaei et.al, 2016

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MDS Abstracts - https://www.mdsabstracts.org/abstract/tracking-the-role-of-the-subthalamo-temporal-network-in-speech-a-deep-brain-stimulation-electroencephalography-study/