Speech in Parkinson's disease following subthalamic nucleus deep brain stimulation: Preliminary results

Abstract

Impairment of speech can affect the majority of patients with Parkinson's disease (PD). Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an effective treatment for the improvement of limb movements, but its effect on speech is less predictable. This study aims to compare the effects of STN-DBS versus the effects of medical (drug) treatment alone on speech and limb movement over 1 year. Sixteen consecutive patients with PD, who were part of a larger trial, were randomized in two groups, either surgical treatment (N = 8) with bilateral STN-DBS or medical treatment (N = 8). Both groups were assessed in the "on and off" medication states, at baseline and at 1 year, using a speech evaluation protocol and the motor part of the Unified Parkinson's Disease Rating Scale (UPDRS-III). The group that received STN-DBS was also assessed in the "on and off" stimulation states. The speech evaluation consisted of recordings of sustained phonation, sentence reading, and 1 minute of monologue. The STN-DBS group in the "on medication and on stimulation" state showed an improvement of the UPDRS-III score. Stimulation and medication also increased significantly the intensity of sustained phonation and the mean of long-term average spectra of the read sentences and the monologue. The sentence intelligibility scores did not change significantly in either group, with the STN-DBS patients showing a wide variability. All acoustical measures of speech for the medical group showed a small and nonsignificant deterioration over 1 year. This is the first study to compare the effects of medical and STN-DBS treatment on speech and limb movement in PD over a year. The different effects of STN-DBS and medication on speech and limb movement warrant further investigation.