Preservation of branchimotor neurons of the nucleus ambiguus in multiple system atrophy.

Cholinergic neurons in the nucleus ambiguus (NA) were counted in autopsy tissue obtained from five patients with multiple system atrophy (MSA), four patients with PD, and five controls. The number of neurons in the dorsal NA was not significantly different among the three groups. Neurons in the ventrolateral portion of the NA were depleted in MSA. Laryngeal stridor cannot be explained solely by neuronal loss in the NA.