Swallowing and deep brain stimulation : swallowing function in Parkinson's disease after subthalamic nucleus and caudal zona incerta deep brain stimulation

Abstract: Background Swallowing problems are common in Parkinson’s disease, and these affect morbidity and mortality largely due to aspiration-induced pneumonia. Even mild dysphagia affects patient Quality of Life. Deep Brain Stimulation (DBS), a surgical treatment for Parkinson’s disease, improves overall motor function, though the effect of DBS on swallowing function is not clear. The aim of the studies in this thesis was to improve our understanding of the effect from DBS of caudal zona incerta and subthalamic nucleus on pharyngeal swallowing function. Specific aims were to compare DBS effects over time postoperatively (6 & 12 months) for swallowing function, on and off stimulation, with a preoperative baseline assessment in order to identify possible negative swallowing effects of DBS.Methods Eight patients with DBS in caudal zona incerta and eleven patients with DBS in subthalamic nucleus were included in the two studies. The effect of DBS on swallowing function was evaluated by self-estimation on a visual analogue scale and fiberoptic endoscopic evaluation of swallowing function with a predefined swallowing protocol including Rosenbek’s Penetration/Aspiration Scale, Secretion Severity Scale,preswallow spillage, pharyngeal residue and pharyngeal clearance. The patients with caudal zona incerta DBS also answered questions regarding swallowing-related Quality of Life. All patients received L-dopa treatment during postoperative assessments.Results There was no clear effect of DBS on swallowing function in the two samples. The occurrence of aspiration, secretions, pharyngeal residue or clearance was not affected by the surgery or the stimulation. In the subthalamic nucleus DBS sample, self-estimations revealed an improvement with stimulation turned on. For the caudal zona incerta DBS patients, no effect of DBS was seen on the results from the swallowing-related QOL questions.Conclusion Subthalamic nucleus DBS and caudal zona incerta DBS did not appear to have a negative effect on swallowing function in this cohort. Patients with subthalamic nucleus DBS reported a self-perceived improvement in swallowing function after DBS. There appears to be no increased risk for aspiration or penetration due to surgery or stimulation regardless of stimulation site. Since the sample sizes in these cohorts are small, the findings need to be confirmed in larger studies.