Vagus nerve ( IX )

Abbas A. A. Shawka

Medical student

2nd grade

Function

Nerve Modality Nucleus Position Distribution

Vagusnerve

SVE**

Nucleus ambigius Medulla Motor to constrictor muscles of pharynx, intrinsic muscles oflarynx, muscles of palate (except tensor veli palatini), and striatedmuscle in superior two thirds of esophagus

GVE Dorsal vagus nuclei Medulla Smooth muscle of trachea, bronchi, and digestive tract,cardiacmuscle

GVA Solitary nucleus Lower medulla

Visceral sensation from base of tongue, pharynx, larynx, trachea,bronchi, heart, esophagus, stomach, and intestine

SVA Taste from epiglottis and palate

GSA Sensory nucleus of trigeminal nerve

Pons – C2 Sensation from auricle, external acoustic meatus, and dura materof posterior cranial fossa

Anatomy

• Leave medulla between olive and ICP.

• Exit the skull through jugular foramina in whit the nerve lie posteriorly in it.

• Superior ganglion have cells convey GSA

• Two branches from the superior ganglion :-

• 1- meningeal branch ( sensory )

• 2- auricular branch ( sensory )

• Inferior ganglion have cells for GVA and SVA.

IX

X

XI

XII

Anatomy

• Descend in neck in the carotid sheath posteriorly and enter thorax anterior to subclavian a. on left and between CCA and sumcalvian a. on right side

• In mediastinum it will give branches to pulmonary and esophageal plexus.

• Enter abdomen through esophageal opening ( left anteriorly and right posteriorly ) to terminate in the abdominal viscera.

IX

X

XI

XII

Branches in H&N

• In jugular fossa :-

1. Meningeal branch ( GSA ) to dura of posterior cranial cavity

2. Auricular branch ( GSA )

12

Branches in H&N

• In neck :-

1. Pharyngeal branch ( SVE ) :-supply all muscles of pharynx and soft palate except for stylopharungeous ( IX ) and tensor veli palatine (V) { form pharungeal plexus with IX and external laryngeal nerve }

2. Superior laryngeal nerve ( SVE ) (GSA) divides into external laryngeal n. ( SVE ) and internal laryngeal n. ( GSA )

3. Recurrent laryngeal nerve (SVE) and ( GSA )

4. Cardiac branch

1

2

3

4

Vagus nuclei

1. N. ambiguous

2. Dorsal vagus nucleus

3. Nucleus solitaries

4. Spinal nucleus and tract

1

2

3

4

1

4

23

1

4

2

3

Vagus nuclei • The vagus nerve includes axons which

emerge from or converge onto four nuclei of the medulla:

1. The dorsal nucleus of vagus nerve —which sends parasympathetic output to the viscera, especially the intestines

2. The nucleus ambiguus — which gives rise to the branchial efferent motor fibers of the vagus nerve and preganglionic parasympathetic neurons that innervate the heart

3. The solitary nucleus — which receives afferent taste information and primary afferents from visceral organs

4. The spinal trigeminal nucleus —which receives information about deep/crude touch, pain, and temperature of the outer ear, the dura of the posterior cranial fossa and the mucosa of the larynx

1

2

3

4

Evaluation

• Sensory evaluation :-

• Difficult due to overlapping with VII and IX

• Motor evaluation :-

• Bilateral elevation of palate and uvula without deviation indicate normal function to X.

• Unilateral vagal injury lead to failure of palate elevation , uvula deviation away from the affected side and unilateral vocal cord paralysis ( hoarsens )

Lesions • Recurrent laryngeal nerve palsies are most commonly due to malignant

disease (25%) and surgical damage (20%) during operations on the thyroid gland, neck, oesophagus, heart and lung

• Because of its longer course, lesions of the left nerve are much more frequent than those of the right.

• In a complete unilateral paralysis of vocal cords, the cord takes up an intermediate position between full abduction and adduction; the voice is hoarse and the patient cannot cough in the usual explosive manner. In an incomplete lesion the cord takes up an adducted position, i.e. the power of abduction seems to be lost first. Despite several theories, there is no universally acceptable explanation why this should be so.

• High lesions of the vagus nerve which affect the pharyngeal and superior laryngeal as well as the recur rent laryngeal branches cause difficulty in swallowing as well as vocal cord defects

Evaluation

• Reflexes

• Gag reflex

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

• Cough reflex

• Afferent (X) nucleus solitaries medullary respiratory centers

• Afferent (X) nucleus solitaries N. ambigious efferent (X) larynx and pharynx muscles

• Vomiting reflex

• Afferent CNX nucleus solitaries N ambigious

efferent X close glottis

• Afferent CNX nucleus solitarious reticulospinaltract contraction of diaphragm and abdominal muscles

Evaluation

• Autonomic evaluation

• lpsilateral decreased carotid sinus reflex may be seen because vagal outflow Is necessary.

• Bilateral vagi dysfunction is associated with tachycardia and other signs of sympathetic over activity ..

Thank You