Response to subthalamic deep brain stimulation on speech intelligibility in Parkinson’s disease

Abstract

The study reports on intelligibility of reading and monologues produced by Parkinsonian patients who underwent unilateral subthalamic deep brain stimulation (STN DBS). Twenty right-handed individuals with advanced Parkinson’s disease (PD) and dysarthria underwent unilateral STN DBS. Ten were operated on the right hemisphere and ten on the left hemisphere. The side receiving STN DBS had more affected motor function. Speech was evaluated before surgery and three-to-six months after surgery with stimulator-off and with stimulator-on; all were off anti-Parkinsonian medication for 12 h before evaluation. Evaluators and subjects were blinded to the subjects stimulator status at the postsurgery evaluations. Nonspeech motor performance was assessed with UPDRS-III. Each subject read a standard passage and produced a monologue on a preselected topic. The readings and monologues were rated for intelligibility using UPDRS-III item 18. Sixteen student clinicians in speech pathology served as judges. Each speech sample was repeated three times. The reading and monologue samples were presented in two blocks. Within each block, the samples were randomly presented to each judge over headphones. Presentation and response collection were completed using a computer procedure written in Praat. The results are discussed with regard to speech and nonspeech motor response and to hemisphere-specific response on speech intelligibility.