Evaluation of the effects of deep brain stimulation of the subthalamic nucleus and levodopa treatment on parkinsonian voice using perturbation, nonlinear dynamic, and perceptual analysis

Abstract

Background/aims: To quantify aperiodic phonation, nonlinear dynamic methods of acoustic voice analysis, such as correlation dimension, have been shown to be useful. The purpose of this study is to evaluate the validity of nonlinear dynamic analysis as a voice analysis tool for the effects of deep brain stimulation (DBS) and levodopa on patients with Parkinson's disease (PD).

Methods: In this study, the effects of DBS and levodopa treatment on patients with PD were measured using perturbation, nonlinear dynamic, and perceptual analysis. Nineteen PD patients that received bilateral (n = 9), left (n = 7), or right (n = 3) DBS performed sustained vowel phonations, which were recorded before and after medication with the stimulator off and on. Recordings were also taken of 10 PD patients who did not receive DBS surgery before and after medication to provide a baseline.

Results: A mixed two-way ANOVA (surgery, medication) generated significant positive treatment effects of DBS only in mean log-transformed D2, which was supported by mean log-transformed shimmer, vF0 (variability in fundamental frequency), and vAm (peak-to-peak amplitude variation).

Conclusion: These findings may indicate the validity of nonlinear dynamic analysis as a complement to perceptual analysis in clinical PD voice studies.

Figure 1

Parkinsonian voice acoustic waveform of a patient that received DBS in the BMSON situation.

Figure 2

The reconstructed phase space of a Parkinsonian voice in this study.

Figure 3

The estimated D₂ value versus r. The curves from bottom to top correspond to the embedding dimension m=1, 2, 3, …, 10.

Figure 4

Boxplot of D₂ values for non-surgical patients in the before- (BM) and after-medication (AM) situations and surgical patients divided by bilateral, left, and right in the before- and after-medication stimulator-off (BMSOFF, AMSOFF) and before- and after-medication stimulator-on (BMSON, AMSON) situations.

Figure 5

Boxplot of perceptual ratings of general vocal impairment for non-surgical patients in the before- (BM) and after-medication (AM) situations and surgical patients divided by bilateral, left, and right in the before- and after-medication stimulator-off (BMSOFF, AMSOFF) and before- and after-medication stimulator-on (BMSON, AMSON) situations.