THE GLOSSOPHARYNGEAL NERVE (CN IX)

 
The Origin(s) and functional components

    • Gustatory nucleus: SVA fibres from the posterior third of the tongue and rudimentary taste buds in the pharynx.

    • Solitary nucleus: GVA fibres from the posterior third of the tongue, pharynx and carotid sinus.

    • Spinal nucleus of the trigeminal nerve: GSA fibres from the pinna of the ear and the external auditory meatus.

    • Nucleus ambiguus: SVE, branchiomotor, fibres to the stylopharyngeus muscle

    • Inferior salivatory nucleus: pre-ganglionic parasympathetic, GVE fibres, to the parotid gland.

The Course and distribution

  • Emerges from the brain stem as a series of five or six small nerve rootlets, immediately dorsal to the inferior olive.

  • Rootlets emerge rostral to the vagus nerve rootlets

  • Exits through the jugular foramen and emerges immediately posterior to the styloid process.

  • It has two ganglia superior (GSA) , and the inferior ( GVA and SVA).

 

Branches
Distribution

Tympanic nerve


  • Tympanic cavity
  • Auditory tube
  • Otic ganglion
Auricular branch
  • Small area on the pinna of the ear
  • External auditory meatus.
Nerve to stylopharyngeus (SVE)
  • Stylopharyngeus muscle
Carotid sinus branch (GVA)
  • Carotid sinus
  • Carotid body
Pharyngeal nerve
  • posterior third of the tongue, providing both SVA (taste) and GVA innervation.
  • Oro-pharyngeal mucosa
Functional Components
 
 

Clinical disorders of Glossopharyngeal nerve

A lesion affecting only the glossopharyngeal nerve is rare. It is characterised by:

  • The loss of (or reduction in) the gag reflex usually elicited by stroking the lateral wall of the pharynx near the tonsilar fossa. 

  •  loss of taste sensation on the ipsilateral posterior third of the tongue
    ,
  • marked reduction in the serous secretion of the ipsilateral parotid gland.