a plexus on the promontory of the labyrinthine wall of the tympanic cavity, formed by the tympanic nerve, an anastomotic branch of the facial, and sympathetic branches from the internal carotid plexus; it supplies the mucosa of the middle ear, mastoid cells, and auditory (eustachian) tube and gives off the lesser superficial petrosal nerve to the otic ganglion. SYN: Jacobson plexus, plexus (nervosus) tympanicus.