Abstract
While bilateral high-frequency subthalamic nucleus stimulation (Bi-HFS) frequently worsens speech in Parkinson's disease (PD), low-frequency stimulation (LFS) may alleviate gait deficits but lacks robust evidence for speech benefits. This randomized trial compared Bi-LFS (60 Hz) and Bi-HFS (130 Hz) in 33 PD patients with postural instability/gait difficulty (PIGD), and evaluated asymmetric frequency stimulation (AFS) in 20 patients. Bi-LFS significantly improved dysphonia severity index (DSI, FDR-p = 0.024), maximum phonation time (MPT, FDR- p = 0.025), and subjective speech ratings compared to Bi-HFS. Left-LFS/right-HFS (L-LFS/R-HFS) matched Bi-LFS efficacy and surpassed Bi-HFS in objective measures (FDR-p ≤ 0.021). Speech improvements correlated with motor/gait gains, independent of tremor. Findings suggest Bi-LFS mitigates speech dysfunction in PIGD-PD, with left-sided LFS potentially driving benefits, while AFS provides comparable outcomes. These data support tailored stimulation protocols to optimize speech in PD. The National Medical Research Registration and Information System of China (MR-31-23-036810).