Subthalamic nucleus stimulation and spontaneous language production in Parkinson's disease: A double laterality problem.

BACKGROUND Asymmetric degeneration of dopaminergic neurons, are characteristic for Parkinson's disease (PD). Despite the lateralized representation of language, the correlation of asymmetric degeneration of nigrostriatal networks in PD with language performance has scarcely been examined. OBJECTIVE/HYPOTHESIS The laterality of dopamine depletion influences language deficits in PD and thus modulates the effects of subthalamic nucleus (STN) stimulation on language production. METHODS The spontaneous language production of patients with predominant dopamine depletion of the left (PD-left) and right (PD-right) hemisphere was compared in four stimulation conditions. RESULTS PD-right made comparatively more verb inflection errors than PD-left. Bilateral STN stimulation improves spontaneous language production only for PD-left. CONCLUSIONS The laterality of dopamine depletion influences spontaneous language production and the effect of STN stimulation on linguistic functions. However, it is probably only one of the many variables influencing the effect of STN stimulation on language production.