The chorda tympani is a branch of the facial nerve that originates from the taste buds in the front of the tongue, runs through the middle ear, and carries taste messages to the brain. It joins the facial nerve (cranial nerve VII) inside the facial canal, at the level where the facial nerve exits the skull via the petrotympanic fissure.
CT: Chorda tympani; I: Incus; JB: Jugular bulb; LSC: Lateral semicircular canal; M: Malleus; PSC: Posterior semicircular canal; S: Stapes; SM: Stapedius muscle; SSC: Superior semicircular canal; VIIms: mastoid segment of VII cranial nerve; VIIts: tympanic segment of VII cranial nerve.
The chorda tympani is part of one of three cranial nerves that are involved in taste. The taste system involves a complicated feedback loop, with each nerve acting to inhibit the signals of other nerves. The chorda tympani appears to exert a particularly strong inhibitory influence on other taste nerves, as well as on pain fibers in the tongue. When the chorda tympani is damaged, its inhibitory function is disrupted, leading to less inhibited activity in the other nerves.