Realization of Fricatives in Patients with Parkinson’s Disease Treated with Deep Brain Stimulation in the Subthalamic Nucleus or the Caudal Zona Incerta

Background In advanced Parkinson’s disease (PD) the motor symptoms can be treated with deep brain stimulation (DBS). Subthalamic nucleus (STN) has been the most common target and caudal zona incerta (cZi) is a more recent target for stimulation. Stimulation in both of these targets has proved to be positive for the motor symptoms but there is no consensus about how DBS affects speech and articulation. Aim The aim of this study was to investigate how fricatives are realized in patients suffering from PD treated with DBS in STN or cZi. Method Nine patients stimulated in STN and 10 patients stimulated in cZi were recorded reading a short text. The recordings were made preoperatively (Pre) and 12 months after surgery with the stimulation switched off (sOff) and on (sOn). From the recordings the fricatives were extracted and assessed in a blinded and randomized procedure. Results For the patients stimulated in cZi the target fricative /s/ had significant lower correct realizations in the sOn condition compared to the other two conditions. The other target fricatives in the cZi group showed the same pattern as well. For the STN group no unequivocal pattern could be seen. Conclusions The results suggest that stimulation in cZi may affect the patients’ articulation of fricatives and thereby their extended articulatory movements more negatively than stimulation in STN.