Laryngeal electromyography in multiple system atrophy with autonomic failure.

In five patients with multiple system atrophy, electromyographic studies using a new surface electrode technique, showed unequivocal evidence of denervation of the posterior crico-arytenoid muscle, and in three of them, of the interarytenoid muscle or crico-pharyngeal sphincter. By comparison, only minor electromyographic abnormalities were found in one-third of patients with other extra-pyramidal syndromes, though in two cases, the abnormalities were of a different kind from those found in multiple system atrophy.