Branch of facial nerve (CN VII) carrying two functional components: special sensory (taste from anterior 2/3 of tongue) + parasympathetic secretomotor (to submandibular + sublingual glands).

Origin

• From facial nerve within facial canal, in its vertical (mastoid) part, a short distance above stylomastoid foramen

Course

1. Passes backward (doubles back, opposite direction to main facial nerve trunk)
2. Enters middle ear via posterior canaliculus for chorda tympani
3. Within middle ear: crosses medial surface of tympanic membrane; runs lateral to long process of incus, medial to neck of malleus; superior to tensor tympani tendon attachment
4. Exits middle ear via anterior canaliculus for chorda tympani (near petrotympanic fissure) → enters infratemporal fossa
5. Descends + joins posterior border of lingual nerve ~2 cm below base of skull
6. Travels within lingual nerve to destinations

Functional Components and Distribution

1. Special sensory (taste):

• Taste from anterior 2/3 of tongue, except vallate papillae (= CN IX)
• Route: lingual nerve → chorda tympani → geniculate ganglion (cell bodies) → nucleus of tractus solitarius

2. Parasympathetic secretomotor:

• Preganglionic from superior salivatory nucleus → nervus intermedius → facial nerve → chorda tympani → lingual nerve → submandibular ganglion (relay)
• Postganglionic to submandibular gland — 5-6 branches directly from ganglion
• Postganglionic to sublingual gland + anterior lingual glands — re-enter lingual nerve via anterior root → distally to glands

Relations in Infratemporal Fossa

• Lateral: mandibular nerve
• Medial: tensor veli palatini
• Posterior: middle meningeal artery
• Anterior: medial pterygoid muscle

Connection with Otic Ganglion

• Connected to otic ganglion + nerve of pterygoid canal → alternative pathway for taste from anterior 2/3 of tongue; clinical evidence suggests parotid gland also receives some secretomotor contribution via chorda tympani

Applied Anatomy

Myringotomy — chorda tympani runs across inner surface of tympanic membrane (lateral to incus long process, medial to malleus neck); incision made in posteroinferior quadrant to avoid nerve injury

Pars flaccida — chorda tympani lies behind pars flaccida; disease involving pars flaccida = caution to avoid nerve injury

Effects of injury:

• Loss of taste from most of anterior 2/3 of tongue
• Reduced salivation from submandibular + sublingual glands

The chorda tympani is a branch of the facial nerve (CN VII) that carries two distinct functional components: special sensory (taste) fibres from the anterior two-thirds of the tongue, and parasympathetic secretomotor fibres to the submandibular and sublingual salivary glands.

Origin

The chorda tympani arises from the facial nerve within the facial canal, in its vertical (mastoid) part, a short distance above the stylomastoid foramen.

Course — Route of Passage

The nerve passes backward (in the opposite direction to the main trunk of the facial nerve, i.e., it “doubles back”) and enters the middle ear cavity through the posterior canaliculus for the chorda tympani.

Within the middle ear, the chorda tympani:

• Runs across the inner (medial) surface of the tympanic membrane.
• Passes lateral to the long process of the incus, but medial to the neck of the malleus.
• Lies superior to the attachment of the tensor tympani tendon.

It then exits the middle ear through the anterior canaliculus for the chorda tympani, near the petrotympanic fissure, to enter the infratemporal fossa.

In the infratemporal fossa, it descends and joins the posterior border of the lingual nerve (a branch of the mandibular division of the trigeminal nerve), about 2 cm below the base of the skull. The chorda tympani then travels within the lingual nerve to reach its destinations.

                FACIAL NERVE (CN VII)
                in facial canal (vertical/mastoid part,
                above stylomastoid foramen)
                          │
                  CHORDA TYMPANI
                  branches off, runs backward
                          │
        Enters middle ear via POSTERIOR CANALICULUS
        for chorda tympani
                          │
        Crosses medial surface of tympanic membrane
        — lateral to long process of incus
        — medial to neck of malleus
                          │
        Exits middle ear via ANTERIOR CANALICULUS
        for chorda tympani (near petrotympanic fissure)
                          │
        Enters infratemporal fossa
                          │
        JOINS LINGUAL NERVE (CN V3 branch)
        ~2 cm below base of skull
                          │
        Travels within lingual nerve
                ┌─────────┴─────────┐
                │                   │
        TASTE FIBRES          SECRETOMOTOR FIBRES
        to anterior 2/3       relay in SUBMANDIBULAR
        of tongue             GANGLION (suspended from
        (except vallate       lingual nerve)
        papillae)                   │
                          ┌─────────┴─────────┐
                          │                   │
                Submandibular gland   Sublingual gland
                (postganglionic       (postganglionic fibres
                fibres direct from    re-enter lingual nerve
                ganglion)             via anterior root, travel
                                       distally to gland)

Functional Components and Distribution

1. Special sensory (taste) fibres:

• Carry taste sensation from the anterior two-thirds of the tongue, except the vallate papillae (which are supplied by the glossopharyngeal nerve).
• Travel via the lingual nerve, then the chorda tympani, to the geniculate ganglion of the facial nerve (cell bodies here), and centrally to the nucleus of the tractus solitarius.

2. Parasympathetic secretomotor fibres:

• Preganglionic fibres arise in the superior salivatory nucleus.
• Pass via the nervus intermedius, the facial nerve, the chorda tympani, and the lingual nerve to reach the submandibular ganglion, where they relay.
• Postganglionic fibres for the submandibular gland pass directly from the ganglion (5–6 branches) to the gland.
• Postganglionic fibres for the sublingual gland and anterior lingual glands re-enter the lingual nerve via its anterior root and travel distally within the nerve to reach the glands.

Relations

• Lateral: Mandibular nerve.
• Medial: Tensor veli palatini (tensor palati) muscle.
• Posterior: Middle meningeal artery.
• Anterior: Medial pterygoid muscle.

Connection with Otic Ganglion

The chorda tympani is connected to the otic ganglion and to the nerve of the pterygoid canal. These connections provide an alternative pathway for taste sensation from the anterior two-thirds of the tongue, and clinical evidence suggests the parotid gland may also receive secretomotor contribution via the chorda tympani.

Clinical Correlation

Myringotomy: When an incision is made in the tympanic membrane to drain pus from the middle ear (myringotomy), care must be taken because the chorda tympani runs across the inner surface of the tympanic membrane (lateral to the long process of the incus, medial to the neck of the malleus). The incision is therefore made in the posteroinferior quadrant, away from the nerve’s course.

Pars Flaccida and Chorda Tympani: The chorda tympani lies behind the pars flaccida of the tympanic membrane; disease involving the pars flaccida should therefore be treated with caution to avoid injury to the nerve.

Effects of Injury:

• Loss of taste sensation from most of the anterior two-thirds of the tongue.
• Reduced salivation from the submandibular and sublingual glands (loss of secretomotor supply).

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