Chorda tympani
Division or branch · CN VII Sensory Parasympathetic
The last branch of the facial nerve inside the temporal bone, leaving the facial canal a few millimetres above the stylomastoid foramen. It crosses the middle ear on the inner surface of the tympanic membrane between the malleus and incus, leaves the skull through the petrotympanic fissure and joins the lingual nerve of V3 in the infratemporal fossa. It carries taste from the anterior two-thirds of the tongue and parasympathetic fibres to the submandibular ganglion.
Traced from the start
Detail
- Sensory
- Taste from the anterior two-thirds of the tongue (fungiform and foliate papillae); cell bodies in the geniculate ganglion, central process to the solitary nucleus
- Parasympathetic
- Preganglionic fibres from the superior salivatory nucleus → submandibular ganglion → submandibular and sublingual glands
- Hitch-hikes on
- The lingual nerve (V3), so lingual nerve injuries also cost taste and salivation
When it goes wrong
Bell's palsy, Ramsay Hunt syndrome or a temporal bone fracture affecting the facial nerve proximal to the chorda tympani
Loss of taste on the anterior two-thirds of the tongue and reduced salivation on the same side as the facial weakness; a lesion at or beyond the stylomastoid foramen spares taste, so taste loss localises the lesion to the temporal bone
Middle ear surgery (tympanoplasty, stapedectomy) or cholesteatoma involving the nerve as it crosses the tympanic cavity
Metallic taste or loss of taste on one side of the tongue that may be permanent
Practise this structure
2 questions in the bank tagged Facial Nerve.
A 52-year-old woman has had two months of numbness over the right forehead, the right upper eyelid and the tip of her nose, with a gritty feeling in the right e…
Foundations · middle twist
A 44-year-old man has had drooping of the right side of his face for three days. He drools from the right corner of his mouth, the right nasolabial fold is flat…
Foundations · common