Objective: The objective of this study was to identify the prevalence of stuttering in PD patients with bilateral STN DBS compared to medically-treated PD (PD-MED) patients, and to determine if using LFS has a beneficial effect on stuttering compared to high frequency stimulation.

Background: Stuttering is a speech disorder involving disruption of verbal fluency, and has frequently been reported after deep brain stimulation (DBS) that targets the subthalamic nucleus (STN). Use of low-frequency stimulation (LFS) has been shown to have beneficial effects on improving speech functions.

Methods: We conducted a cross-sectional study of 15 PD patients with bilateral STN-DBS (PD-DBS) and 32 PD-MED patients. All participants were evaluated by a board-certified neurologist for their stuttering and speech problems during on-period. Only clinically meaningful stuttering, such that the patient and/or caregiver report the problem was disruptive to communication was taken into consideration. Voice level was identified as a sound pressure level in decibels by a digital sound level meter (Benetech, United States). For the PD-DBS patients stuttering, sound pressure, and UPDRS speech sections were compared under three conditions; HFS condition (130 Hz), LFS condition (80 Hz), and off-stimulation condition in 15 PD-DBS patients.

Results: There were no statistically significant differences between PD-DBS patients and PD-MED patients in the following factors: age, gender, disease duration, and H&Y score (p> 0.05, each). However, a significantly lower levodopa equivalent dosage was found in PD-DBS patients compared to PD-MED patients (p< 0.001). Comparison between the two patient groups revealed that stuttering, sound pressure, and UPDRS ADL speech section score in PD-DBS group was significantly worse than those in PD-MED group (p<0.05). Two PD-DBS patients were unable to undergo the off stimulation condition due to severe tremors. Comparison of the three conditions showed HFS resulted in lower sound pressure compared to LFS (p=0.002), and off stimulation (p=0.004). HFS also resulted in a lower UPDRS speech section score compared to LFS in both the activity of daily living section (p=0.002) and motor section (p=0.009). The numbers of stuttering events were also reduced after changing from a HFS (26.3%) into a LFS (5.3%), or off stimulation (11.8%).

Conclusions: Stuttering can be aggravated by STN-DBS, especially with a high frequency stimulation. Though, LFS may have reduced tremor control in our two patients, it seems to be consistently effective on speech problems.

References: 1. Xie T, Padmanaban M, Bloom L, MaCracken E, Bertacchi BDAshman A, et al. Effect of low versus high frequency stimulation on freezing of gait and other axial symptoms in Parkinson patients with bilateral STN DBS: a mini-review. Translational Neurodegeneration 2017; 6:13 DOI 10.1186/s40035-017-0083-7. 2. Tsuboi T, Watanabe H, Tanaka Y, Ohdake R, Yoneyama N, Hara K, et al. Distinct phenotypes of speech and voice disorders in Parkinson’s disease after subthalamic nucleus deep brain stimulation. J Neurol Neurosurg Psychiatry 2015;86: 856–864. 3. Picillo M, Vincos G, Sammartino F, Lozano AM, Fasano A. Exploring risk factors for stuttering development in Parkinson disease after deep brain stimulation. Parkinsonism and Related Disorders. 2017; 38:85-9.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/comparison-of-low-versus-high-frequency-stimulation-on-stuttering-in-parkinsons-disease-patients-with-bilateral-subthalamic-nucleus-deep-brain-stimulation/