Pathogenesis of laryngeal narrowing in patients with multiple system atrophy

1. We do not fully understand the pathogenesis of nocturnal laryngeal strid or in patients with multiple system atrophy (MSA). Recent studies suggest t hat inspiratory thyroarytenoid (TA) muscle activation has a role in the dev elopment of the stridor. 2. The breathing pattern and firing timing of TA muscle activation were det ermined in ten MSA patients, anaesthetized with propofol and breathing thro ugh the laryngeal mask airway, while the behaviour of the laryngeal apertur e was being observed endoscopically. 3. Two distinct breathing patterns, i.e. no inspiratory flow limitation (no -IFL) and IFL, were identified (luring the measurements. During IFL, signif icant laryngeal narrowing was observed leading to an increase in laryngeal resistance and end-tidal carbon dioxide concentration. Development of IFL w as significantly associated with the presence of phasic inspiratory activat ion of TA muscle. Application of continuous positive airway pressure suppre ssed the TA muscle activation. 4. The results indicate that contraction of laryngeal adductors (luring ins piration narrows the larynx leading to development of inspiratory flow limi tation accompanied by stridor in patients with MSA under general anaesthesi a.