Aural Stimulation with Capsaicin Ointment Improved the Swallowing Function in Patients with Dysphagia: Evaluation by the SMRC Scale

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  • Kondo Eiji
    Department of Otolaryngology, University of Tokushima School of Medicine
  • Jinnouchi Osamu
    Department of Otolaryngology, Anan Kyoei Hospital
  • Ohnishi Hiroki
    Department of Otolaryngology, University of Tokushima School of Medicine
  • Kawata Ikuji
    Department of Otolaryngology, Anan Kyoei Hospital
  • Takeda Noriaki
    Department of Otolaryngology, University of Tokushima School of Medicine

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Other Title
  • 外耳道へのカプサイシン軟膏刺激による嚥下障害患者の嚥下機能の改善: SMRC スケールを用いた評価
  • ガイジドウ エ ノ カプサイシン ナンコウ シゲキ ニ ヨル エンカ ショウガイ カンジャ ノ エンカ キノウ ノ カイゼン : SMRC スケール オ モチイタ ヒョウカ

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Cough and swallowing reflexes are important airway-protective mechanisms against aspiration. Angiotensin-converting enzyme (ACE) inhibitors, one of the side effects of which is cough, have been reported to reduce the incidence of aspiration pneumonia in hypertensive patients with stroke. ACE inhibitors have also been reported to improve the swallowing function in post-stroke patients. On the other hand, stimulation of the Arnold nerve, the auricular branch of the vagus, triggers the cough reflex (Arnold's ear-cough reflex). Capsaicin, an agonist of Transient Receptor Potential Vanilloid 1 (TRPV1), has been shown to activate the peripheral sensory C-fibers. Stimulation of the sensory branches of the vagus in the laryngotracheal mucosa with capsaicin induces the cough reflex and has been reported to improve the swallowing function in patients with dysphagia. In our previous study, we showed that aural stimulation of the Arnold nerve with 0.025% capsaicin ointment improved the swallowing function, as evaluated by the endoscopic swallowing score, in 26 patients with dysphagia. In the present study, the video images of swallowing recorded in the previous study were re-evaluated using the SMRC scale by an independent otolaryngologist who was blinded to the information about the patients and the endoscopic swallowing score. The SMRC scale is used to evaluate four aspects of the swallowing function: 1) Sensory: the initiation of the swallowing reflex as assessed by the white-out timing; 2) Motion: the ability to hold blue-dyed water in the oral cavity and induce laryngeal elevation; 3) Reflex: glottal closure and the cough reflex induced by touching the epiglottis or arytenoid with the endoscope; 4) Clearance: pharyngeal clearance of the blue-dyed water after swallowing. Accordingly, we demonstrated that a single application of capsaicin ointment to the external auditory canal of patients with dysphagia significantly improved the R, but not the S, M or C scores, and this effect lasted for 60 min. After repeated aural stimulation with the ointment for 7 days, the R score improved significantly in patients with severe dysphagia. The present findings suggest that stimulation of the Arnold's branch of the vagus in the external auditory canal with capsaicin improves the glottal closure and cough reflex in patients with dysphagia. Thus, aural stimulation with capsaicin represents a novel treatment for dysphagia. It is also suggested that repeated alternative aural stimulation with capsaicin for a week, rather than a single application, is needed to improve the swallowing function in patients with severe dysphagia. By the same mechanism as that underlying the effect of ACE inhibitors, aural stimulation with capsaicin may reduce the incidence of aspiration pneumonia in patients with dysphagia.

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