Branchial motor function (SVE): The muscular branch from the nucleus ambiguus innervates the stylopharyngeal muscle to elevate the pharynx during phases of swallowing and speech. It also innervates the superior pharyngeal constrictor together with muscular branches of CN X.

Visceral motor function (GVE): Fibers from the inferior salivatory nucleus innervate the parotid gland to provide parasympathetic innervation to the parotid gland via the lesser superficial petrosal nerve (promotes salivation).

General somatic sensory function (GSA): It carries general sensory information from the posterior one-third of the tongue, the tonsil, the skin of the external ear, the internal surface of the tympanic membrane, and the pharynx via the superior and inferior petrosal ganglia to the spinal trigeminal nuclei.

Special sensory function (SA): It provides taste sensation from the posterior one-third of the tongue, the circumvallate papillae, posterior pharynx, and the Eustachian tube. This information travels via the inferior petrosal nerve to the nucleus solitarius.

General visceral sensory function (GVA): carries visceral changes in blood O₂ and CO₂ from the carotid body (chemoreceptors) and increased blood pressure information from the carotid sinus (baroreceptors) via the carotid sinus nerve to the inferior petrosal ganglia to reach the nucleus solitaries and the inferior salivatory nucleus, respectively. The former triggers control of respiratory depth and rate, while the latter will cause a vagal response with consensual activation of the dorsal nucleus of CN X.

Demyelinating lesions are most frequent to consider as etiologies of the disease.