Caroticotympanic nerves

Caroticotympanic nerves are branches of the internal carotid arterial plexus and contain post-ganglionic sympathetic fibers which arise from the superior cervical ganglion. The nerves follow the course of caroticotympanic branches of internal carotid artery to enter the middle ear cavity from its inferior wall or floor. Here, they merge with the tympanic plexus over the promontory.

Apart from the caroticotympanic nerves, sympathetic innervation to the tympanic plexus also comes via plexus around the middle meningeal artery. Whereas, the parasympathetic neurons (from inferior salivatory nucleus in the brainstem) reach out to the tympanic plexus via the tympanic branch of glossopharyngeal nerve.

The sympathetic (as well as parasympathetic) neurons are distributed to the parotid gland through the auriculotemporal nerve. The Sympathetics cause vasoconstriction of parotid vessels that reduces parotid secretions.