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Cranial nerves · Mixed

IX. Glossopharyngeal nerve

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The glossopharyngeal nerve (CN IX) supplies sensation and taste to the posterior third of the tongue and the pharynx, motor fibres to stylopharyngeus, parasympathetic secretomotor fibres to the parotid gland, and afferents from the carotid sinus and body.

Terminologia Anatomica (Latin): Nervus glossopharyngeus

Function

General somatic and visceral afferent from the pharynx, tonsil, posterior third of the tongue, middle ear and carotid sinus (baroreceptors) and body (chemoreceptors). Special visceral afferent (taste, posterior third). Special visceral efferent to stylopharyngeus. General visceral efferent to the parotid gland via the otic ganglion.

Nuclei

Nucleus ambiguus (motor to stylopharyngeus), inferior salivatory nucleus (parasympathetic), nucleus of the solitary tract (taste and visceral afferents including the carotid sinus), and the spinal trigeminal nucleus (general sensation).

Exit from the skull

It leaves the skull through the jugular foramen, together with CN X and CN XI, passes between the internal carotid artery and the internal jugular vein, and curves forward around stylopharyngeus to reach the pharynx and tongue.

Testing

Test the gag reflex (afferent IX, efferent X) and the palatal movements, and assess the taste and general sensation of the posterior third of the tongue when needed. Isolated IX lesions are uncommon and are usually assessed together with the vagus nerve.

Signs of a lesion

Loss of the gag reflex on the affected side (afferent limb), loss of taste and sensation over the posterior third of the tongue, and mild dysphagia. Glossopharyngeal lesions usually coexist with vagal and accessory involvement in jugular foramen syndromes.

Clinical correlations

Glossopharyngeal neuralgia causes brief, severe pain in the throat, tonsil, ear or base of the tongue, triggered by swallowing, coughing or talking, and may be accompanied by syncope through vagal overactivity. Jugular foramen lesions (glomus tumour, schwannoma, metastasis) affect IX, X and XI together.

Common exam points

  • Leaves via the jugular foramen with CN X and XI.
  • Only muscle supplied is stylopharyngeus; parasympathetic to the parotid via the otic ganglion.
  • Afferent limb of the gag reflex (efferent: vagus) and of the carotid sinus reflex.
  • Taste and general sensation from the posterior third of the tongue.
  • Glossopharyngeal neuralgia: paroxysmal throat or ear pain, sometimes with syncope.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Haines DE, Mihailoff GA. Fundamental Neuroscience for Basic and Clinical Applications. Elsevier, 5th edition (2018) — Tier 3 (textbook)
  4. Bickley LS. Bates' Guide to Physical Examination and History Taking (Bickley). Wolters Kluwer, 13th edition (2020) — Tier 3 (textbook)

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