Pathogenesis of laryngeal narrowing in patients with multiple system atrophy

Abstract

1. We do not fully understand the pathogenesis of nocturnal laryngeal stridor in patients with multiple system atrophy (MSA). Recent studies suggest that inspiratory thyroarytenoid (TA) muscle activation has a role in the development of the stridor.2. The breathing pattern and firing timing of TA muscle activation were determined in ten MSA patients, anaesthetized with propofol and breathing through the laryngeal mask airway, while the behaviour of the laryngeal aperture was being observed endoscopically.3. Two distinct breathing patterns, i.e. no inspiratory flow limitation (no-IFL) and IFL, were identified during the measurements. During IFL, significant laryngeal narrowing was observed leading to an increase in laryngeal resistance and end-tidal carbon dioxide concentration. Development of IFL was significantly associated with the presence of phasic inspiratory activation of TA muscle. Application of continuous positive airway pressure suppressed the TA muscle activation.4. The results indicate that contraction of laryngeal adductors during inspiration narrows the larynx leading to development of inspiratory flow limitation accompanied by stridor in patients with MSA under general anaesthesia.

Abnormalities of Respiratory Control and the Respiratory Motor Unit

“…48 -50 However, electromyographic studies indicate that stridor is associated with sustained tonic activity of adductor vocal cord muscles. 47,51,52 Respiratory insufficiency may be the presenting symptom in MSA, causing daytime hypersomnolence or dyspnea on exertion. 44 Alveolar hypoventilation resulting in hypercapnic respiratory failure during sleep, or sometimes while awake, can sometimes occur, and even cause death by hypoxemia in extreme cases.…”

Non-invasive positive pressure ventilation for laryngeal contraction disorder during sleep in multiple system atrophy

“…If untreated, sudden death may occur during sleep [1,4,5]. Although pathological and electrophysiological studies have been used to investigate the possible mechanisms [6,7], the pathogenesis of stridor remains controversial. If laryngeal inspiratory stridor is demonstrated by laryngoscopy, tracheostomy or continuous positive airway pressure (CPAP) has been recommended as the standard treatment [1,8].…”

The close relationship between life-threatening breathing disorders and urine storage dysfunction in multiple system atrophy

“…VCAP, which results in obstructive sleep apnea, is attributed to a loss of vagal motoneurons in the nucleus ambiguous (NA) [10,11] or dystonia of the vocal cords due to supranuclear impairment [12,13]. On the other hand, impairment of the respiratory center or impaired ventilatory chemosensitivity results in central sleep apnea (CSA), which can be observed even after tracheostomy [4,5,14].…”