Clinical predictors of speech changes after subthalamic neurostimulation in Parkinson's disease

Objective: To identify preoperative clinical predictive factors of postoperative speech changes in Parkinson’s disease (PD) patients with bilateral subthalamic nucleus deep brain stimulation (STN-DBS). Methods: Demographic variables, neuroimaging data, and clinical characteristics were retrospectively collected from consecutive PD patients, before, 1 and 10-years after bilateral STN-DBS at the Grenoble University Hospital (France) from 1993 to 2015. Predictors of postoperative speech changes (demographic, clinical and MRI variables) were assessed with univariate and multivariate logistic regression analyses. We considered as “event” a worsening of speech subscore (UPDRS item 18; MDS-UPDRS item 3.1) in the postoperative on-stimulation/off-medication (1-year follow-up) or under chronic treatment (10-years follow-up) conditions compared with the preoperative off-medication condition. Results: 324 PD patients (males: 196; disease duration at surgery: 11.10 [± 4.13] years; age at surgery: 56.25 [± 8.52] years) were included in the analysis. Overall, the speech item of the clinical rating did not change in 138 patients (42.6%), it improved in 113 patients (34.9%) and worsened in 73 patients (22.50%) 1-year after surgery. The preoperative off-medication speech item score and the degree of motor improvement after surgery in the med-off condition predicted the 1-year postoperative speech change. In the long-term subgroup (n=51) the preoperative percentage of daily time spent with fluctuations was associated with long-term speech worsening. Interpretation: Effects of STN-DBS on speech can substantially vary in PD patients. Predictors of short-term speech deterioration appears to be related to preoperative off-medication speech impairment and degree of motor improvement after surgery.