CRANIAL NERVE 9 (GLOSSOPHARYNGEAL) & CRANIAL.pptx

CRANIAL NERVE

1. CRANIAL NERVE 9 (GLOSSOPHARYNGEAL) & CRANIAL NERVE 10 (VAGUS)

2. W ork together to supply the musculature of the pharynx (mostly supplied by CN 10) and T ransmit visceral afferent information from vascular baroreceptors. A nd each nerve also has additional individual functions.

3. T hey are difficult to isolate clinically. C ommonly affected together since they both communicate with nuclei in the dorsolateral medulla. B oth pass through the jugular foramen, and they are adjacent throughout parts of the neck.

4. CN 9 supplies: • One pharyngeal muscle: stylopharyngeus • One gland: parotid • One region of taste: posterior one third of the tongue • One region of visceral sensation: carotid body • Three small regions of somatic sensation: posterior one third of the tongue, pharynx (shared with CN 10), middle ear, and external auditory meatus (shared with CN 7 and CN 10

5. The functions of CN 10 include: • Motor supply to all muscles of the larynx and pharynx except tensor veli palitini (CN 5), mylohyoid (CN 5), stylohyoid (CN 7), stylopharyngeus (CN 9) • Motor supply to one muscle of the tongue: palatoglossus (all others are innervated by CN 12)

6. Cont … Somatic sensation from: • The dura matter of the posterior fossa aside from the tentorium (the sensory innervation to the rest of the dura including the tentorium is supplied by CN 5) • The pharynx (shared with CN 9) • The external auditory meatus (shared with CN 7 and CN 9

7. Cont … Visceral sensation from the aortic arch • Visceral parasympathetic efferent supply to and afferent input from all of the viscera of the thorax and abdomen with the exception of the distal third of the GI tract and genitourinary organs (which receive their parasympathetic supply from sacral spinal cord levels S2–S4). • Taste in the pharynx

8. There are several functions that are shared across cranial nerves CNs 5, 7, 9, and 10,

9. Cont … The laryngeal and pharyngeal motor input to CN 9 and CN 10 comes from the nucleus ambiguus in the dorsal medulla. Visceral motor supply that travels in CN 10 originates in the dorsal motor nucleus of the vagus . Afferent visceral information arrives with taste information to the nucleus solitarius .

10. Lesions of CN 10 can cause laryngeal and/or pharyngeal weakness. Laryngeal weakness can lead to softer voice ( hypophonia ), nasal voice, and guttural dysarthria (difficulty producing the consonants “G” and “K”). Pharyngeal weakness can cause difficulty swallowing (dysphagia).

11. On examination, CN 9 and CN 10 can be assessed by evaluating palate elevation and gag reflex. When there is unilateral palate weakness , the palate droops on the weak side and is pulled upward toward the stronger side. The gag reflex is mediated predominantly by CN 9 for the afferent limb ( palate sensation) and predominantly CN 10 for the efferent limb (palate elevation).

12. Unilateral palate/larynx dysfunction can be caused by: • Brainstem pathology: for example, posterior inferior cerebellar artery ( PICA ) stroke causing lateral medullary syndrome (causing unilateral palate/laryngeal dysfunction due to involvement of the nucleus ambiguus ; other symptoms include vertigo, ataxia, Horner’s syndrome, and/or crossed hemisensory loss [decreased pain/temperature sensation in the face ipsilateral to the lesion and body contralateral to the lesion])

13. Cont … • Jugular foramen pathology: for example, glomus jugulare tumor , which can affect CNs 9, 10, and 11 • Local pathology in the neck: for example, lymphadenopathy , carotid dissection • Complication of neck surgery: for example, thyroid surgery or carotid endarterectomy

14. Cont … Isolated unilateral laryngeal dysfunction can also be caused by pathology in the upper thorax because the recurrent laryngeal nerve branch of the vagus nerve descends into the upper thorax before re-ascending to the larynx Therefore , mediastinal , aortic, or apical lung pathology or cardiothoracic surgery can all cause recurrent laryngeal nerve dysfunction leading to hoarseness of the voice.

15. Bilateral laryngeal/pharyngeal dysfunction is commonly seen in motor neuron disease (e.g., amyotrophic lateral sclerosis [ALS ].

16. Glossopharyngeal Neuralgia A nalogue to trigeminal neuralgia. Lancinating neuralgic pain occurs in the throat and/or ear. Pain can be triggered by swallowing . Syncope occurs during attacks of glossophayngeal neuralgia in some cases due to altered visceral afferent transmission in CN 9. N euroimaging should be obtained to evaluate for the possibility of compression of CN 9 by a vascular loop (although most cases are idiopathic ), and antiepileptics such as carbamazepine may be used for treatment.

17. Axial 3D CISS image reveals right glossopharyngeal nerve (large arrowhead) in contact with loop formed by right PICA (arrows) at supraolivary fossette . On left side, note PICA (arrow) that does not compress left glossopharyngeal nerve (small arrowhead).

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