Deep brain stimulation of the subthalamic nucleus in Parkinson’s Patients: Effects on Swallowing Function

Background: Swallowing disorders are common in patients with Parkinson’s disease (PD). Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is used as a surgical treatment option for the disease. The surgery is well recognized in improving limb function, but it is unclear how swallowing is affected. Aim: To investigate the effect of DBS-STN on swallowing function and if pre-operative effect of medication correlates with post-operative effect of stimulation. Method: Fiberoptic Endoscopic Evaluation of Swallowing (FEES) was used to retrospectively evaluate swallowing function in 9 PD patients who had undergone DBS surgery at Umeå University Hospital in Sweden. Comparisons were made pre-operatively (medication on and off), 6 and 12 months post-operatively (stimulation on and off, medication on). The following parameters were evaluated: penetration-aspiration, preswallow spillage, pharyngeal residue, clearance and secretion stagnation. Results: DBS-STN improved swallowing in 2 out of 9 patients; however the stimulation did not entirely eliminate dysfunction. Post-operative response to stimulation on swallowing function did not correlate with pre-operative L-Dopa response. Conclusions: DBS-STN improved swallowing function only to some degree in a limited number of patients and cannot be used to treat dysfunction. Response to stimulation was differing both within and across patients. Thus, dysphagia in PD cannot solely be explained by dopaminergic deficiency. Further, non-pharmacologic, swallowing therapy is necessary for those PD patients who suffer from swallowing disorders.