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Background: Subthalamic nucleus deep brain stimulation (STN-DBS) is an effective therapy for selected Parkinson's disease patients with motor fluctuations, but can adversely affect speech and axial symptoms. The use of short pulse width (PW) has been shown to expand the therapeutic window acutely, but its utility in reducing side effects in chronic STN-DBS patients has not been evaluated. Objective To compare the effect of short PW settings using 30-mu s with conventional 60-mu s settings on stimulation-induced dysarthria in Parkinson's disease patients with previously implanted STN-DBS systems.

Methods: In this single-center, double-blind, randomized crossover trial, we assigned 16 Parkinson's disease patients who had been on STN-DBS for a mean of 6.5 years and exhibited moderate dysarthria to 30-mu s or 60-mu s settings for 4 weeks followed by the alternative PW setting for a further 4 weeks. The primary outcome was difference in dysarthric speech measured by the Sentence Intelligibility Test between study baseline and the 2 PW conditions. Secondary outcomes included motor, nonmotor, and quality of life measures.

Results: There was no difference in the Sentence Intelligibility Test scores between baseline and the 2 treatment conditions (P = 0.25). There were also no differences noted in motor, nonmotor, or quality of life scores. The 30-mu s settings were well tolerated, and adverse event rates were similar to those at conventional PW settings. Post hoc analysis indicated that patients with dysarthria and a shorter duration of DBS may be improved by short PW stimulation.

Conclusions: Short PW settings using 30 mu s did not alter dysarthric speech in chronic STN-DBS patients. A future study should evaluate whether patients with shorter duration of DBS may be helped by short PW settings.