Course
- The glossopharyngeal nerve emerges from the medulla with the vagus and hypoglossal nerves and exits the skull via the jugular foramen, accompanied by the vagus and accessory nerves.
Jacobson nerve
- Aka
- Tympanic branch of the glossopharyngeal nerve (CN IX)
- Inferior salivary nucleus → Arises from the inferior ganglion of the glossopharyngeal nerve → Carries preganglionic parasympathetic fibres → enters the tympanic cavity via the inferior tympanic canaliculus (Jacobson canal) → contributes to the tympanic plexus located on the cochlear promontory → The parasympathetic fibres leave the plexus as the lesser petrosal nerve → Otic ganglion → auriculotemporal nerve → parotid gland
- Pathology
- The neuroendocrine cells related to this nerve give rise to tympanic paraganglioma.
- A Jacobson nerve schwannoma is a rare middle ear tumour presenting as a mass along the cochlear promontory or enlargement of the inferior tympanic canaliculus
Function
- Five functional components make up the glossopharyngeal nerve (IX):
- Special sensory fibers have their cell bodies in the inferior glossopharyngeal ganglion.
- They supply the taste buds in the posterior third of the tongue and terminate in the nucleus of the solitary tract.
Components | Ganglia | Nuclei | Exit through Skull | Target Organ | Function |
Somatic motor | ㅤ | Nucleus ambiguus | Jugular foramen | Stylopharyngeus | Elevates pharynx |
Visceral motor | Otic | Inferior salivatory | ㅤ | Parotid gland | Gland secretion |
Somatic sensory | Superior glossopharyngeal | Spinal trigeminal tract | ㅤ | External ear | Somatic sensation |
Visceral sensory | Inferior glossopharyngeal | Solitary tract | ㅤ | Carotid sinus and body; pharynx and posterior third of tongue | Baro- and chemoreceptor reflexes; pain, temperature, and touch sensation |
Special sense | ㅤ | ㅤ | ㅤ | Taste buds in posterior third of tongue | Taste |
Clinical
Hering’s nerve
- A branch of CN IX that is the sensory limb of the carotid body. When a chemoreceptor detects changes in blood O2 and CO2 concentration, Hering’s nerve is stimulated
Glossopharyngeal nerve lesion
- Rarely occurs in isolation
- Causes
- Hoarse voice
- Dysphagia
- Loss of the gag reflex
- Glossopharyngeal neuralgia
- A syndrome of agonizing ear and throat pain, is similar in character to trigeminal neuralgia but less common.