Investigation of the improvement of swallowing function with low-frequency pulse waves or interference waves delivered via cervical electrical stimulation in patients with Parkinson's disease: A randomized controlled study protocol.

Parkinson's disease (PD) is associated with a high rate of swallowing dysfunction, which may lead to aspiration pneumonia. This randomized controlled trial aims to investigate the effects of cervical electrical stimulation interventions (interferential current or low-frequency pulse wave stimulation) on swallowing dysfunction in patients with PD. The study will include patients with PD with Hoehn-Yahr stages 2-4 and will assess the swallowing function in a multifaceted manner using tools such as the 1 % citric acid cough test, videofluoroscopic swallowing study (VFSS), Functional Oral Intake Scale score, and Eating Assessment Tool-10 score. The primary endpoint is an improvement in the cough reflex, as measured by the citric acid cough test, whereas the secondary endpoints include changes in the swallowing function, including the VFSS, tongue pressure, and salivary substance P levels. Participants will receive 30 min of cervical stimulation daily for 2 weeks. This study also explores the use of novel instruments such as multichannel surface electromyography and electronic stethoscopes for the detailed assessment of swallowing physiology. By investigating these two electrical stimulation techniques, this study seeks to provide insights into the pathophysiology of swallowing dysfunction in PD and to evaluate the efficacy and safety of these interventions. Trial registration number: jRCTs062240041; pre-results.