Peculiar snoring in patients with multiple system atrophy: its sound source, acoustic characteristics, and diagnostic significance.

It is known that abductor paralysis (AP) of the vocal folds sometimes occurs in patients with multiple system atrophy (MSA), and some of them have sleep apnea and loud snoring during sleep. However, the site of obstruction and the sound source of the snoring are still unknown. We performed fiberscopic examinations under diazepam sedation in 8 MSA patients with AP and analyzed the snoring sound. We found that the peculiar snoring occurred with inspiratory vibration of the vocal folds, and there was no obstruction in this portion. Acoustic analysis showed that the fundamental frequency of vocal fold snoring was 260 to 330 Hz, which is different from that of ordinary soft palate snoring. Recognition of vocal fold snoring is important in the early diagnosis of MSA and sleep-related breathing disorders.