Laryngeal sensory testing using flexible endoscopy
Satoh, Asako Kaneoka
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Sensory input from the laryngeal mucosa is vital for triggering protective airway reflexes. The laryngeal adductor reflex (LAR) is a brief vocal fold adductor reflex in response to stimulation of the laryngeal mucosa. Depressed LAR may lead to aspiration of foreign substances into the airway. Loss of laryngeal sensation has thus been considered as one of the risk factors associated with aspiration and airway complications in patients with dysphagia. Laryngeal sensation can be endoscopically tested by lightly and briefly touching a patient’s arytenoids or epiglottis with the tip of a flexible laryngoscope (the touch method). In a preliminary study, we endoscopically investigated the laryngeal sensation and swallowing ability of healthy adults and patients with dysphagia. The results indicated an association between sensory deficits as determined by the touch method and penetration/aspiration of trial boluses in both healthy adults and patients with dysphagia. However, the pressure applied to the larynx using this touch method might not be consistent, and the expected responses elicited by this method were uncertain. Study 1 of this dissertation investigated the variability in the pressure delivered by clinicians using the touch method. The study also reported on the types of various subject responses to the touches. The results revealed that there was a wide range of pressure levels exerted by examiners. This suggested the need for further research to establish the validity of this diagnostic tool. The study also showed that the LAR always occurred in response to touch in normal volunteers, suggesting that this technique may be quite sensitive at detecting sensory deficits in a person who does not exhibit an LAR in response to touch. Study 2 examined hospitalized patients with symptoms of dysphagia. The question of interest was whether an absent LAR in response to touch was associated with aspiration or pneumonia. No significant association was found between absent LAR and aspiration of food or liquid; however, a significant association was observed between absent LAR and the occurrence of pneumonia. The study indicated that the touch method has potential for predicting pneumonia in patients with swallowing problems.