Abductor Paresis in Shy-Drager Disease

Vocal cord abductor impairment (VCAI) is a life-threatening complication in MSA. It is characterized by vocal cord abduction restriction with paradoxical movements, associated with a characteristic inspiratory stridor. VCAI is caused by five factors derived from two core components of abductor paralysis and adductor hyperactivities. Upper airway structures consisting of the soft palate, oropharyngeal regions, tongue base, epiglottis, arytenoid regions, and vocal cords can obstruct independently, simultaneously at multilevel, or additionally with progression. Moreover, central respiratory disturbances such as central sleep apnea and hyposensitivity to hypoxemia also contribute to upper airway obstruction, resulting in a complex respiratory disturbance. In respiratory management, there are several problems including multilevel obstruction, supraglottic collapse, CPAP failure, and complex sleep apnea. Upper airway obstruction develops via dynamic changes in quantity and in quality. Prediction and comprehensive treatment of respiratory disturbances in multiple system atrophy (MSA) are therapeutic challenges.