CorpusHuman Anatomy
NervousNerve

Glossopharyngeal nerve (CN IX)

Nervus glossopharyngeus

Also known as: CN IX, ninth cranial nerve

A mixed nerve of the 3rd pharyngeal arch. It carries taste and general sensation from the posterior third of the tongue and the oropharynx, information from the carotid body and sinus, parasympathetic fibres to the parotid gland, and motor fibres to the single muscle stylopharyngeus.

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Overview

ExitJugular foramen
GangliaSuperior & inferior (sensory); otic (parasympathetic)
Only muscle suppliedStylopharyngeus
Pharyngeal arch3rd

CN IX emerges as rootlets from the postolivary sulcus of the upper medulla and leaves the skull through the jugular foramen, in front of X and XI. Just outside the skull it has two sensory ganglia, superior and inferior (petrosal). It descends between the internal carotid artery and the internal jugular vein. It then curves forward around the stylopharyngeus muscle and passes between the superior and middle pharyngeal constrictors to reach the base of the tongue and the palatine tonsil.

Its nuclei, all in the medulla, are:
• the nucleus ambiguus (SVE) to stylopharyngeus;
• the inferior salivatory nucleus (GVE);
• the nucleus of the solitary tract (taste and visceral afferents);
• the spinal trigeminal nucleus (general sensation).

The tympanic nerve (Jacobson's nerve) forms the tympanic plexus on the promontory of the middle ear. It continues as the lesser petrosal nerve to the otic ganglion, whose postganglionic fibres travel with the auriculotemporal nerve (V3) to the parotid gland. The carotid sinus nerve (of Hering) carries baroreceptor information from the carotid sinus and chemoreceptor information from the carotid body. These afferents form the afferent limb of the baroreceptor reflex and contribute to the control of breathing.

Location

Upper medulla (postolivary sulcus) → jugular foramen → between the ICA and IJV → around stylopharyngeus → base of the tongue and pharynx.

Parts & subdivisions

  1. Functional components
    Both (mixed): SVE (stylopharyngeus), GVE (parotid), GVA (carotid sinus and body, pharynx), SVA (taste, posterior 1/3 of the tongue) and GSA (posterior tongue, middle ear and a small area of the external ear).
  2. Clinical testing
    The gag reflex: touching the posterior pharyngeal wall or tonsillar pillar (afferent IX) produces pharyngeal contraction and palatal elevation (efferent X). Also test taste and sensation on the posterior third of the tongue, which is rarely done in practice. IX is usually assessed together with X.
  3. Lesion signs
    Ipsilateral loss of the gag reflex (afferent limb), loss of taste and sensation on the posterior 1/3 of the tongue, and mild dysphagia. An isolated CN IX lesion is rare. It is usually involved together with X and XI in jugular foramen (Vernet) syndrome, for example from a glomus jugulare tumour.

Anatomy

Innervation

- Motor: stylopharyngeus.
• Parasympathetic: parotid gland via the otic ganglion.
• Sensory: posterior 1/3 of the tongue (taste and general sensation), oropharynx, palatine tonsil, middle ear and auditory tube, carotid sinus and carotid body.

Course

Medulla → jugular foramen (anterior part) → superior and inferior (petrosal) ganglia → descends between the ICA and IJV → winds around the posterior border of stylopharyngeus → passes between the superior and middle constrictors → tonsillar bed and posterior third of the tongue.

Branches

- Tympanic nerve: tympanic plexus, then lesser petrosal nerve, then otic ganglion, then the parotid gland via the auriculotemporal nerve.
• Carotid sinus nerve.
• Pharyngeal branches: sensory part of the pharyngeal plexus.
• Nerve to stylopharyngeus.
• Tonsillar branches.
• Lingual branches: taste and general sensation to the posterior 1/3 of the tongue.

Function

  • Taste and general sensation from the posterior third of the tongue
  • Sensation from the oropharynx, tonsils, middle ear and auditory tube
  • Baroreceptor and chemoreceptor input from the carotid sinus and body (cardiovascular and respiratory reflexes)
  • Parotid salivary secretion
  • Elevation of the pharynx and larynx during swallowing and speech (stylopharyngeus)
  • Afferent limb of the gag reflex

Clinical significance

Glossopharyngeal neuralgia

Paroxysmal, stabbing pain in the throat, tonsil, base of the tongue and ear, triggered by swallowing, talking or yawning. It can be accompanied by bradycardia or syncope, through the carotid sinus nerve and vagal reflexes. It is treated like trigeminal neuralgia, with carbamazepine.

Tonsillectomy

CN IX lies in the tonsillar bed deep to the superior constrictor. Injury during tonsillectomy can cause post-operative loss of taste and sensation on the posterior third of the tongue, and referred earache through the tympanic branch.

Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.