Abstract
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become an effective and widely used tool in the treatment of Parkinson’s disease (PD). STN-DBS has varied effects on speech. Clinical speech ratings suggest worsening following STN-DBS, but quantitative intelligibility, perceptual, and acoustic studies have produced mixed and inconsistent results. Improvements in phonation and declines in articulation have frequently been reported during different speech tasks under different stimulation conditions. Questions remain about preferred STN-DBS stimulation settings. Seven right-handed, native speakers of English with PD treated with bilateral STN-DBS were studied off medication at three stimulation conditions: stimulators off, 60 Hz (low frequency stimulation—LFS), and the typical clinical setting of 185 Hz (High frequency—HFS). Spontaneous speech was recorded in each condition and excerpts were prepared for transcription (intelligibility) and difficulty judgements. Separate excerpts were prepared for listeners to rate abnormalities in voice, articulation, fluency, and rate. Intelligibility for spontaneous speech was reduced at both HFS and LFS when compared to STN-DBS off. On the average, speech produced at HFS was more intelligible than that produced at LFS, but HFS made the intelligibility task (transcription) subjectively more difficult. Both voice quality and articulation were judged to be more abnormal with DBS on. STN-DBS reduced the intelligibility of spontaneous speech at both LFS and HFS but lowering the frequency did not improve intelligibility. Voice quality ratings with STN-DBS were correlated with the ratings made without stimulation. This was not true for articulation ratings. STN-DBS exacerbated existing voice problems and may have introduced new articulatory abnormalities. The results from individual DBS subjects showed both improved and reduced intelligibility varied as a function of DBS, with perceived changes in voice appearing to be more reflective of intelligibility than perceived changes in articulation.
Highlights
High frequency, chronic stimulation of the subthalamic nuclei (STN) has become a widespread tool in the treatment of levodopa responsive Parkinson’s disease (PD), minimizing tremor and bradykinesia.Similar to levodopa, deep brain stimulation (DBS) of the STN has had a less impressive impactBrain Sci. 2020, 10, 26; doi:10.3390/brainsci10010026 www.mdpi.com/journal/brainsciBrain Sci. 2020, 10, 26 on the axial symptoms, including balance, gait, and speech
The present study examined the effects of three DBS frequencies using three measures of a single speech task considered most sensitive to the PD disorder and STN-DBS, spontaneous speech
The “Rating Ave.” columns represent the average percent changes for the lower frequencies (LFS) and high frequency stimulation (HFS) conditions. These results demonstrate that, in general, both LFS and HFS reduce the intelligibility of spontaneous speech in the range of 11% to 16% compared to the STN-DBS off condition
Summary
Chronic stimulation of the subthalamic nuclei (STN) has become a widespread tool in the treatment of levodopa responsive Parkinson’s disease (PD), minimizing tremor and bradykinesia.Similar to levodopa, deep brain stimulation (DBS) of the STN has had a less impressive impactBrain Sci. 2020, 10, 26; doi:10.3390/brainsci10010026 www.mdpi.com/journal/brainsciBrain Sci. 2020, 10, 26 on the axial symptoms, including balance, gait, and speech. Chronic stimulation of the subthalamic nuclei (STN) has become a widespread tool in the treatment of levodopa responsive Parkinson’s disease (PD), minimizing tremor and bradykinesia. Deep brain stimulation (DBS) of the STN has had a less impressive impact. Brain Sci. 2020, 10, 26 on the axial symptoms, including balance, gait, and speech. This paper begins with a brief review of gait studies to further understand of the effects of STN frequency settings, followed by a consideration of selected studies of speech. Both behaviors, gait and speech, have been shown to yield variable results with this form of therapy
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