Investigating the effects of subthalamic Nucleus-Deep brain stimulation on the voice quality.

Deep brain stimulation (DBS) is a standard surgical treatment method which is generally applied to subthalamic nucleus in Parkinson's patients in cases where medical treatment is insufficient in treating the motor symptoms. It is known that Subthalamic Nucleus Deep Brain Stimulation (STN-DBS) treats many motor symptoms. However, the results of studies on speech and voice vary. The aim of the study is analysing the effect of STN-DBS on the characteristics of voice. A total of 12 patients, (8 male-4 female) with an age average of 58.8 ± 9.6, who have been applied DBS surgery on STN included in the study. The voice recordings of the patients have been done prior to surgery and 6 months after the surgery. The evaluation of voice has been carried out through the instrumental method. The patients' voice recordings of the /a,e,i/ vowels have been done. The obtained recordings were evaluated by the Praat programme and the effects on jhitter, shimmer, fundamental frequency (F0) and noise harmonic rate (NHR) were analysed. Numerical values of F0 of all female participants have been decreased for all of the vowels postoperatively. In the females; jhitter and fraction parameters were found to be significantly different (0.056 and 0.017, perspectively) for the vowel /e/. In addition, values in the shimmer for vowels /e,i/ were thought to be clinically significant (.087, .079 and .076) respectively. All these changes in second measurements were found to indicate worsening vocal quality after the DBS in females. In males, there is not any significant difference observed between two measures in any of the parameters of any vowels. Acoustic voice quality deteriorated after STN-DBS predominantly for females however this deterioration was not prominent audio-perceptually. This finding commented as a result of the fact that that voice quality deviance of the participants was not severe.