Chorda tympani

At a glance

English

Chorda tympani

Latin (TA2)

Chorda tympani

System

Nerve

Region

Head

Side

Paired, left and right

About the chorda tympani

The chorda tympani is a slender offshoot of cranial nerve VII, the facial nerve, with two jobs. It carries taste from the front two-thirds of the tongue back to the brainstem, and it carries preganglionic parasympathetic fibres outwards for two salivary glands, the submandibular and the sublingual. It has no fibres for the muscles of the face. Its name, the cord of the drum, comes from its course across the inside of the eardrum.

Its fibres enter the temporal bone with the facial nerve through the internal acoustic meatus. The chorda leaves the facial nerve in the facial canal a few millimetres above the stylomastoid foramen and enters the middle ear through a small canal in its back wall. It then runs forwards across the inner surface of the tympanic membrane, covered by the lining of the middle ear, passing between the handle of the malleus and the long limb of the incus, medial to the malleus at its neck. It leaves through the petrotympanic fissure, emerges into the infratemporal fossa and, deep to lateral pterygoid, joins the back of the lingual nerve.

From then on it travels hidden within the lingual nerve. Its parasympathetic fibres leave to synapse in the submandibular ganglion, which hangs from the lingual nerve above the submandibular gland; the postganglionic fibres drive saliva from the submandibular and sublingual glands and widen vessels of the tongue. The taste fibres stay with the lingual nerve to reach the fungiform papillae on the front of the tongue. Their cell bodies lie in the geniculate ganglion, and centrally they end in the upper, gustatory part of the solitary nucleus, an area they share with taste fibres of the greater petrosal and glossopharyngeal nerves. The chorda is especially sensitive to salt.

Because it lies exposed in the middle ear, the nerve can be stretched or cut during ear surgery or inflamed by middle ear disease. The result is loss or distortion of taste on the front of the tongue on that side, often with a metallic taste, while taste at the back of the tongue, served by the glossopharyngeal nerve, is kept. The chorda normally damps activity in other taste nerves and in pain fibres of the tongue, so its loss can release odd taste or burning sensations.

Course and supply

Arises from

The facial nerve within the facial canal of the temporal bone, a little above the stylomastoid foramen; its taste fibres have their cell bodies in the geniculate ganglion.

Ends in

Joins the lingual nerve in the infratemporal fossa; its secretory fibres end in the submandibular ganglion and its taste fibres in the taste buds of the front two-thirds of the tongue.

Supplies

Taste from the front two-thirds of the tongue; preganglionic parasympathetic (secretomotor) supply to the submandibular and sublingual glands, relayed in the submandibular ganglion.