Daytime hypoxemia, sleep-disordered breathing, and laryngopharyngeal findings in multiple system atrophy

Background: The mechanism underlying nocturnal sudden death in patients with MSA remains unclear. It may be explained by upper airway obstruction, such as vocal cord abductor paralysis; an impairment of the respiratory center, such as Cheyne- Stokes respiration; or an impaired hypoxemic ventilatory response. Objective: To investigate the mechanism of sleep-disordered breathing in multiple system atrophy ( MSA). Design: We recruited 21 patients with probable MSA who were admitted sequentially to our hospital, and performed daytime blood gas analysis, pulmonary function tests, polysomnography, and fiberoptic laryngoscopy during wakefulness and with the patient under anesthesia. Results: A decrease in arterial oxygen pressure and an increase in alveolar- arterial oxygen gradient significantly correlated with disease duration ( P=. 045 and.046, respectively). Polysomnography demonstrated CheyneStokes respiration in 3 ( 15%) of 20 patients. Fiberoptic laryngoscopy during wakefulness showed that 3 ( 14%) of the 21 patients exhibited vocal cord abductor paralysis, and laryngoscopy under anesthesia showed that 9 ( 45%) of 20 patients exhibited vocal cord abductor paralysis. Laryngoscopy under anesthesia also revealed that 11 ( 55%) of 20 patients showed upper airway obstruction in places other than the vocal cords, including obstruction at the base of the tongue or soft palate. In addition, it demonstrated novel laryngopharyngeal findings, such as floppy epiglottis and airway obstruction at the arytenoid. Conclusions: We observed daytime hypoxemia with an increased alveolar- arterial oxygen gradient, CheyneStokes respiration, and novel abnormal laryngopharyngeal movements in patients with MSA. We also found that laryngoscopy under anesthesia might be useful for evaluating upper airway obstruction. The significance of these findings to the mechanism of sudden death in those with MSA needs to be examined.