Diagnosis and treatments for oropharyngeal dysphagia: effects of capsaicin evaluated by newly developed ultrasonographic method

Abstract

Oropharyngeal dysphagia (OD) is a common symptom in the older people, and may cause fatal complications such as aspiration pneumonia. However, there is no established treatment for OD. The relationship between the transient receptor potential vanilloid 1 (TRPV1) and substance P released by activated TRPV1 was recently demonstrated. Further, there are several reports showing that capsaicin, a specific agonist of TRPV1, can improve OD. Currently, the evaluation of swallowing is mainly performed by videofluoroscopic examination. However, there are no reports on the clinical application of ultrasonography using tissue Doppler imaging. In this review, we describe the pathophysiology and treatments for OD, introduce our novel US method to evaluate cervical esophageal motility, and then outline our clinical study examining the effects of capsaicin, a specific TRPV1 agonist, in older patients with OD.

Keywords: capsaicin; oropharyngeal dysphagia; substance P; transient receptor potential vanilloid 1; ultrasonographic tissue Doppler imaging.

Fig. 1.

The assumed important pathological factors associated with oropharyngeal dysphagia (OD) in older patients.

Fig. 2.

The physiological pathway of the sensory nervous system involved in the swallowing reflex via transient receptor potential vanilloid 1 (TRPV1), capsaicin, and substance P (SP).

Fig. 3.

The detailed protocol of our study. Taken from Nakato et al. Digestion 2017 (ref. 55).

Fig. 4.

Correlation of the duration of the rate of change in the cervical esophageal wall opening time (CEOT) and the rate of change in salivary SP. There was a significant negative correlation of the rate of change in the CEOT with the rate of change in SP. Taken from Nakato et al. Digestion 2017 (55).