Introduction

Aspiration secondary to impaired swallow function, or dysphagia, is one of the major causes of mortality in patients with Parkinson’s disease (PD). Dysphagia usually does not respond well to medications. Despite its effectiveness on motor fluctuation, dyskinesia and tremor in patients with PD, deep brain stimulation (DBS) is not as effective on axial symptoms of balance, freezing of gait (FOG), speech and swallow function. Studies even raise concerns about axial symptoms under usual high-frequency stimulation (HFS) of the subthalamic nucleus (STN), particularly ON medication.1 STN DBS has various effects on swallow function.2–4 Swallowing involves multiple phases, with oral and pharyngeal phases most critical for bolus clearance and airway protection. However, the impact of different oral textures on aspiration with or without DBS in patients with PD has not been studied.2 Fast-flowing liquids may be more likely to aspirate before and during the swallow, although with less risk of post-swallow aspiration of residue compared with more viscous solids. Dynamic changes in swallow parameters have not been well characterised either.2 A comprehensive evaluation in a randomised double-blind study under various DBS conditions over time is therefore of significant importance. We hypothesised that liquids would more likely yield aspiration than solids, regardless of DBS conditions and assessment timing, and that swallowing measures could worsen in a year.