Changes in speech characters of patients with Parkinson's disease after bilateral subthalamic nucleus stimulation

To investigate the effects of bilateral subthalamic nucleus deep brain stimulation (STN-DBS) on acoustic characteristics of speech in Chinese patients with Parkinson's disease (PD).

Eleven patients (five men and six women) diagnosed with PD participated in this study. Motor disabilities and speech samples were evaluated and recorded under six different conditions according to the states of medication and stimulation. Motor disabilities were evaluated with the Unified Parkinson's Disease Rating Scale (UPDRS). Acoustic signals were recorded from the subjects during production of sustained vowels /a/, /i/, and/u/; repetitions of /pataka/; and sentence production tasks. Acoustic analysis was performed with the Multidimensional Voice Program (MDVP), the Motor Speech Profile (MSP), and Computerized Speech Lab (CSL) (Kay Elemetrics, Lincoln Park, NJ).

Based on the UPDRS III scores, the motor ability of the patients improved. There was almost no change in the speech score, which was also supported by the instrumental analysis of PD speech. This indicated that bilateral STN-DBS was associated with a significant improvement in the patients' motor disabilities but did not have much influence on speech performance during the short time after the stimulation switch was turned on. Furthermore, gender-related differences for speech performance were demonstrated, with the vowel /i/ being more sensitive.

These results are consistent with previous studies that have reported disparity between limb and speech improvements after neurosurgical intervention for PD, such as STN-DBS. The long-term effects of STN-DBS on Parkinsonian speech of Chinese patients should be studied further.