Oral Transport, Penetration, and Aspiration in PD: Insights from a RCT on STN + SNr Stimulation

Dysphagia is frequent and detrimental in advanced Parkinson's disease (PD) and does not respond to standard treatments. Experimental models suggested that pathological overactivity of the substantia nigra pars reticulata (SNr) may hinder oral contributions to swallowing. Here, we hypothesized that the combined stimulation of subthalamic nucleus (STN) and SNr improves measures of dysphagia after eight weeks of active treatment. We enrolled 20 PD patients with dysphagia and deep brain stimulation (DBS). Patients were assessed in 'medication on' and 'STN' stimulation at baseline (V1) and then were randomized 1:1 to 'STN' or 'STN + SNr' stimulation. In addition, patients of both groups received swallowing therapy as a standard of care. The primary endpoint was the change in Penetration-Aspiration Scale (PAS) at eight-week follow-up (V2) with respect to the baseline (V1) under the hypothesis, that 'STN + SNr' was superior to 'STN'. We obtained further secondary endpoints on oral preparation, transport, pharyngeal phase, penetration, and aspiration. PAS change from V1 to V2 was not significantly different between groups (p = 0.221). When considering all patients for secondary analyses, we found that the entire study cohort showed better PAS scores at V2 compared to V1 irrespective from DBS treatment allocation (p = 0.0156). Both STN and STN + SNr treatments were safe. 'STN + SNr' stimulation was not superior compared to standard 'STN' stimulation both on PAS and the secondary endpoints. We found that the entire study cohort improved dysphagia after eight weeks, which presumably mirrors the effect of continued swallowing therapy and the increased patient attention on swallowing.