Glossopharyngeal Nerve( IX )

Abbas A. A. Shawka

Medical student

2nd grade

Function

Nerve Modality Nucleus Position Distribution

Glosso-pharyngeal

nerve

SVE Nucleusambigius

Medulla Motor to stylopharyngeusthat assists withswallowing

GVE Inferior salivatorynucleus

Medulla Parasympatheticinnervation to parotidgland

GVA

Solitary nucleus Lower medulla

Visceral sensation fromparotid gland, carotidbody and sinus,pharynx, and middle ear

SVA Taste from posterior 1/3of tongue

GSA sensory nucleus of trigeminal

nerve

Pons – C2 Cutaneous sensation fromexternal earCommon sensation fromposterior 1/3 of tongue

Anatomy

• The gtossopharyngeal nerve leaves the medulla between the olive ventnlly and the inferior cerebellar peduncle dorsally.

• Most rostral part of the CN exit between olive and ICP.

• The nerve sends off a tympanic branch to the middle ear beforeexiting the skull through the jugular foramen.

• In jugular foramina it lies anterior to CN X,XI.

• The nerve exits the jugular foramen posteromedlal to tbe styloid process, then descends lateral to the

• pharynx between the internal carotid arrery (ICA) and IJV (lntenaljugular vein) In the carotid space.

IX

X

XI

XII

Anatomy

• It supplies the stylopbatyngeusmusde and then penetrates the pbaryngeal constrictor muscles (above the level of the middle constrictor ) to reach the posterior aspect of the tongue.

Branches • As the nerve passes through the

jugular foramen, it gives rise to six terminal branches.

• These are :-

1. the tympanic

2. the carotid

3. the pharyngeal

4. the tonsillar

5. the lingual

6. the muscular branches

• OBSERVE THE MODALITY OF EACH BRANCH AND RELATE IT TO THE FUNCTION OF THE NERVE !!

1

2

3,4,5

6

• Nuclei 1. N ambiguous

2. Solitary tract nucleus

3. Spinal tract of V n.

4. Inferior salivatory nucleus

1

2

3

4

1

4

2 3

1

4

2

3

Glossopharyngeal nuclei1. The branchial motor component originates from the nucleus ambiguus

2. The preganglionic nerve fibers originate in the inferior salivatory nucleus

3. the visceral sensory fibers enter the lateral medulla between the olive and the inferior cerebellar peduncle and descend in the tractus solitariusto synapse in the caudal nucleus solitarius. From the nucleus solitarius, connections are made with several areas in the reticular formation and hypothalamus to mediate cardiovascular and respiratory reflex responses to changes in blood pressure, and serum concentrations of CO2 and O2.

4. The central processes of the general sensory neurons exit the glossopharyngeal ganglia and pass through the jugular foramen to enter the brainstem at the level of the medulla. Upon entering the medulla these fibers descend in the spinal trigeminal tract and synapse in the caudal spinal nucleus of the trigeminal.

Glossopharyngeal nuclei

5. The central processes of the special sensory neurons exit the inferior ganglion and pass through the jugular foramen to enter the brainstem at the level of the rostral medulla between the olive and inferior cerebellar peduncle. Upon entering the medulla, these fibers ascend in the tractussolitarius and synapse in the gustatory part of nucleus solitarius. Taste fibers from CN VII and X also ascend and synapse here. Ascending secondary neurons originating in nucleus solitarius project bilaterally to the ventral posteromedial (VPM) nuclei of the thalamus via the central tegmental tract. Tertiary neurons from the thalamus project via the posterior limb of the internal capsule to the inferior one-third of the primary sensory cortex (the gustatory cortex of the parietal lobe).

Evaluation • Sensory evaluation :-

• sensory evaluation of

- Posterior 1/3 of the tongue

- Soft palate

- Nasopharynx

• Motor evaluation :-

- NOT IMPORTANT / since this nerve supply only stylopharyngeous and when paralyzed will lead to mild dysphagia

Evaluation

• Reflexes

• Gag reflex

- Afferent ( IX ) N ambiguous efferent to pharyngeal muscle ( IX and X )

- Light touch to pharynx, tonsillar area or base of toung will lead to gagging !

- Gagging is retraction of the tongue and elevation and constriction of pharyngeal muscles.

Evaluation

• Reflexes

- Palatal reflex

- Afferent ( IX ) N ambiguous efferent to palatal and pharyngeal muscle (X)

- Light touch to soft palate should lead to ipsilateral deviation of the uvula and elevation of the soft palate ( swallowing reflex )

Evaluation

• Autonomic evaluation

• Ipsilateral alteration in salivation from parotid ( difficult to test ).

• Bradychardia or tachycardia associated with hypotension ..

Lesions & Test • Isolated glossopharyngeal nerve

lesions are extremely rare, as the last four cranial nerves are not often damaged and even if they are, they are commonly affected together (e.g. by a posterior cranial fossa tumour).

• Since the motor part of the glossopharyngeal nerve supplies only one small muscle, stylopharyngeus, it is impossible to test.

• If necessary, taste sensation on the posterior part of the tongue can be tested.

• The Glossopharyngeal nerve (CN IX) provides sensory supply to the palate. It can be tested with the gag reflex or by touching the arches of the pharynx

Notes :-• IX nerve is one of four CNs that

carry parasympathetic fibers ..

• Nuclei :- inferior salivatorynucleus

• Ganglia :- Otic ganglion

• Secretomotor to parotid gland

• IX-tympanic n. – tympanic plexus – lesser petrosal – oticganglion – auriculotemporal -parotid gland …

• Tympanic branch carry ALL the parasympathetic fibers of this nerve…

Thank You